Distal Femur Fractures: Epidemiology, Anatomy, Biomechanics & Operative Indications

This patient has end-stage ankle arthritis. A short course of NSAIDs may provide pain and inflammation relief. Bracing with either an ankle-foot orthosis or Arizona brace can reduce pain by offloading the ankle joint. Ankle fusion is a reliable procedure for treatment of end-stage ankle arthritis and is especially recommended for active people after it is determined that nonsurgical measures no longer provide adequate relief. Arthroscopic debridement and cheilectomy may be indicated for bony impingement and mild arthritis with little articular cartilage loss. The long-term results of ankle distraction arthroplasty are not yet well defined but likewise would be reserved for scenarios in which nonsurgical measures no longer provide adequate relief. The patient must be able to wear a thin-wire external fixator for 3 months.
RECOMMENDED READINGS
Abidi NA, Neufeld SK, Brage ME, Reese KA, Sabharwal S, Paley, D. Ankle arthritis. In: Pinzur MS, ed. Orthopaedic Knowledge Update: Foot and Ankle 4. Rosemont, IL: American Academy of Orthopaedic Surgeons; 2008:159-193.
Saltzman CL: Ankle arthritis, in Coughlin MJ, Mann RA, Saltzman CL (eds): Surgery of the Foot and Ankle. Philadelphia, PA, Mosby Elsevier, 2007, vol 1, pp 929-932.

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This is a 5-year-old girl with a new diagnosis of scoliosis, having an isolated right thoracic curve. This is considered juvenile onset idiopathic scoliosis, which presents between the ages of 3-9 years old. The initial radiographs show a curve measuring 41°. Any curve >20° in a patient with early onset scoliosis should undergo MRI of the entire spine to assess for intraspinal pathology, with an average of 20% of patients having underlying diagnoses, i.e. Arnold-Chiari, syringomyelia. Observation or TLSO bracing may be indicated; however, an MRI is still the first line of management in this patient. Physical therapy may be useful for adjunct treatment, but the MRI is still required at this stage of evaluation and diagnosis.

Extent of soft tissue injury has been shown in Level 2 evidence as having the highest impact on the decision to undergo limb salvage or amputation.
The referenced study by MacKenzie et al looked at 527 of the 601 patients initially enrolled in the Lower Extremity Assessment Project (LEAP) and looked at several variables which are thought to be predictors of amputation. Severe muscle injury had the highest impact on the decision to amputate the limb, likely related to the surgeon’s assessment that the salvaged limb would function poorly because of the risk of infection, nonunion, and poor function.
The absence of plantar sensation had the next most significant impact on surgical decision making. Factors that would influence proceeding with an amputation include an nonviable limb, irreparable vascular injury, warm ischemia time of more than 8 hours, or a severe crush injury with minimal remaining viable tissue. Amputation should also be considered when attempts at limb salvage leave the limb so severely damaged that function will be less satisfactory than that afforded by a prosthetic replacement, are a threat to the patient’s life, or would demand multiple surgical procedures and prolonged reconstruction time that is incompatible with the personal, sociologic, and economic consequences the patient is willing to undergo.

Surgical excision of a symptomatic ganglion, with removal of the entire ganglion stalk and a portion of the joint capsule at its base, reliably relieves pain and has a low recurrence rate (approximately 5%). C losed rupture, while potentially effective, has a recurrence rate of approximately 50%. Ganglions are prone to recur after aspiration, although 3 serial aspirations of a ganglion have been shown to reduce the recurrence rate to about 15%. The addition of corticosteroids to aspiration treatment has not been shown to provide any additional benefit. While observation of painless ganglions is certainly acceptable treatment given their benign prognosis, it is not considered the optimal course for a symptomatic lesion.

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Lumbopelvic fixation (pedicle screws, iliac screws) has more stability than a stand-alone iliosacral screw. The initial description of iliosacral screw fixation of U-shaped sacral fracture by Nork and associates recommended non-weight bearing for 2 months and use of thoracic lumbosacral hip orthosis for 6 to 8 weeks. In a comparison of lumbopelvic fixation with iliosacral screws, Kelly and associates demonstrated that lumbopelvic fixation allowed immediate weight bearing and increased likelihood of discharge to home; however, iliosacral screw fixation led to a shorter operative time and less blood loss.

DISCUSSION: The MRI scans reveal increased signal in the medial facet of the patella and the anterior aspect of the lateral femoral condyle. This pattern is typically seen in patients with acute patellar dislocations. In patients with ACL tears, the bone bruise of the lateral femoral condyle is usually seen in the central portion at the sulcus terminalis and the posterior half of the lateral tibial plateau and is not usually seen in the patella. This pattern of bone bruising is not seen with patellar tendon ruptures, LCL tears, and PCL tears.
REFERENCES: Elias DA, White LM, Fithian DA: Acute lateral patellar dislocation at MR imaging: Injury patterns of medial patellar soft-tissue restraints and osteochondral injuries of the inferomedial patella. Radiology 2002;225:736-743.
Virolainen H, Visuri T, Kuusela T: Acute dislocation of the patella: MR findings. Radiology 1993;189:243-246.

Repetitive subfailure strains have been shown to affect the mechanical behavior of the inferior glenohumeral ligament, producing dramatic declines in the peak load response and length increases that are largely unrecoverable. In another study, anteroinferior subluxation was found to result in nonrecoverable strain in the anteroinferior capsule, varying from 3% to 7% through a range of joint subluxation.
REFERENCES: Pollock RG, Wang VM, Bucchieri JS, et al: Effects of repetitive subfailure strains on the mechanical behavior of the inferior glenohumeral ligament. J Shoulder Elbow Surg 2000;9:427-435.
Malicky DM, Kuhn JE, Frisancho JC, et al: Nonrecoverable strain fields of the anteroinferior glenohumeral capsule under subluxation. J Shoulder Elbow Surg 2002;11:529-540.

Radiation exposure decreases by a factor of 4 when a surgeon doubles the distance from the radiation beam. No radiation exists 6 ft from a fluoroscopy unit.Correct Answer: 6 ft

Originally, Burkhalter and Strait recommended bony insertion into the proximal phalanx through a drill hole. This procedure does require more surgical dissection and flexes only the MCP joints; thus it cannot extend the PIP joints directly. It does improve clawing in the fingers if the PIPs can extend with preoperative MCP flexion. The ability to extend the PIP joints is evaluated preoperatively using the Bouvier test. With the wrist in neutral position, the examiner holds the MCPs flexed and looks for the ability in that position to actively extend the PIPs. If the patient is able to do so, then the test is considered positive, and this describes "simple" clawing. In such cases, procedures that flex only the MCPs are appropriate. The insertion sites for these procedures include the proximal phalanx, the first annular pulley, and the second annular pulley. If the Bouvier test is negative, then it is best to insert the tendon grafts distally into the lateral bands. This technique has a low chance of leading to hyperextension of the PIP joints, particularly when performed with a wrist extensor motor (which leaves the flexor digitorum superficialis undisturbed) and with no preoperative hyperextensibility of the PIPs.

Osteonecrosis of the femoral head is a known complication from the use of rigid intramedullary nails for femoral fractures in adolescents. When the nails are placed through the piriformis fossa, the lateral ascending vessels of the femoral neck may be injured, resulting in osteonecrosis of the femoral head in 1% to 2% of patients. Rigid reamed nails placed into the piriformis fossa are contraindicated in children with open growth plates because the physis is a barrier to blood supply and the ligamentum teres does not provide sufficient vascularity. Alternative fixation methods for femoral fractures in adolescents include external fixation and open reduction and internal fixation. Nailing through the tip of the trochanter may decrease the incidence of this serious complication.
REFERENCES: Letts M, Jarvis J, Lawton L, et al: Complications of rigid intramedullary rodding of femoral shaft fractures in children. J Trauma 2002;52:504-516.
Stans AA, Morrissy RT, Renwick SE: Femoral shaft fracture treatment in patients age 6 to 16 years. J Pediatr Orthop 1999;19:222-228.
Buckley SL: Current trends in the treatment of femoral shaft fractures in children and adolescents. Clin Orthop 1997;338:60-73.
Beaty JH, Austin SM, Warner WC, et al: Interlocking intramedullary nailing of femoral-shaft fractures in adolescents: Preliminary results and complications. J Pediatr Orthop
1994;14:178-183.

Compartment syndrome of the hand can result from a variety of factors, including a traumatic event such as crush injury, fracture, vascular insult, a high-pressure injection injury, or an insect or spider bite. The treatment involves decompressive fasciotomy of the involved compartments. The diagnosis of hand compartment syndrome is determined by history, examination, and objective testing. Patients experience pain out of proportion to the injury, along with swelling and tense skin. Pain may occur with passive motion of the metacarpophalangeal joints as the intrinsic muscles are stretched. Invasive intracompartmental pressures can be measured in the compartments of the hand but not in the fingers. Arterial Doppler studies assess arterial blood flow, and an abnormality would be a late finding. MRI would show edema of the hand and fingers, but the decision to perform surgical release is less likely made from the findings. The most appropriate method of determining the need for finger fasciotomy is the _history and physical examination._

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The injury shown is a flexion-type supracondylar humerus fracture. The most commonly interposed anatomic structure is the ulnar nerve. The brachialis muscle is often interposed in extension-type fractures, as are the median nerve and radial artery. The radial nerve is at risk for entrapment in a humeral shaft fracture or distal third humeral fracture.

Figures A through C show a medial subtalar dislocation. Irreducible dislocations are typically the result of either inadequate sedation or interposed soft tissue structures.
In medial dislocations, the extensor digitorum brevis, the deep peroneal neurovascular bundle, or the joint capsule may block a closed reduction. In lateral dislocations, the most common structure implicated as a block to reduction is the posterior tibial tendon, although the flexor digitorum longs, posterior tibial neurovascular bundle or flexor hallucis may also block reduction.
Bibbo et al found that subtalar dislocations were irreducible 32% of the time and that 88% had ipsilateral foot and ankle injuries. At follow up, 89% of patients demonstrated radiographic changes of the subtalar joint, and had worse function on the side of the subtalar dislocation as demonstrated by lower
AOFAS scores.
Incorrect Answers:

. The flexor hallucis longus tendon may be a block to closed reduction for lateral subtalar dislocations
Answer 3. The posterior tibial tendon may be a block to reduction for lateral subtalar dislocations
Answer 4. The tibialis anterior tendon does not commonly preclude closed reduction of a subtalar dislocation
Answer 5. The plantar fascia does not block closed reduction of the subtalar joint

Spontaneous rupture of the extensor pollicis longus tendon is most frequently associated with which of the following scenarios?

1) Non-displaced distal radius fracture

2) Non-displaced Rolando fracture

3) Second metacarpal base fracture

4) Boxer's fracture

5) Non-displaced radial styloid fracture

and findings.

A 79-year-old cyclist is involved in an accident and sustains a displaced femoral neck fracture as seen in Figure A. What is the
optimal treatment?
1) Open reduction internal fixation

2) Bipolar hemiarthroplasty

3) Unipolar hemiarthroplasty

4) Total hip arthoplasty

5) Nonoperative treatment

An AP pelvis radiographs with a displaced femoral neck fracture is seen in Figure A. It important to note that degenerative changes are seen on this image. Both references suggest that elderly active individuals should be treated with a primary total hip after displaced femoral neck fractures.
In the first study by Blomfeldt et al, the group reviewed a series of patients who underwent either an acute primary total hip arthroplasty for a femoral neck fracture or a delayed primary hip after an attempt at ORIF. They found that the group treated with an acute primary total hip arthroplasty had better Harris hip and quality of life scores.
The second reference from Blomfeldt et al, studies a population of active elderly patients randomized to either a total hip arthroplasty or bipolar for femoral neck fractures. The group found no mortality or dislocation difference between the groups, but higher Harris hip scores at 1 year in patients treated with a total hip
arthroplasty.

A 53-year-old man sustains the injury seen in figure A and later undergoes open reduction and internal fixation. What variable will
most significantly increase his rate of degenerative arthritis in the long-term?
1) Postoperative joint stepoff

2) Alteration of limb mechanical axis

3) Fracture type

4) Male sex

5) Age greater than 50

Maintenance of mechanical axis correlates most with a satisfactory clinical outcome when managing an intra-articular fracture of the proximal tibia.
According to the study of plateau fractures with up to 27 year follow-up by Rademakers et al, malalignment of the limb by greater than 5 degrees tripled the rate of degenerative osteoarthritis (27% v. 9%). Age at time of injury had no effect on outcome; 31% had joint space narrowing but 64% of those knees were well tolerated.
Weigel and Marsh's study looked at high energy plateau fractures treated with staged external fixation followed by internal fixation, and noted a low rate of severe arthrosis even with mild to moderate joint incongruity.
Stevens et al noted a worse outcome with increasing age at presentation with these injuries; fracture type had a small influence and adequacy of reduction had no significant influence on outcome.
Figure A is a coronal CT image showing a lateral tibial plateau fracture with significant joint depression.

A 69-year-old male sustained a proximal humerus fracture that underwent open reduction and internal fixation nine months ago. He complains of constant pain and weakness; repeat radiographs are shown in Figures A and B. What is the most appropriate surgical treatment at this time?
1) Revision open reduction and internal fixation

2) Valgus corrective osteotomy of proximal humerus

3) Shoulder arthroplasty

4) Shoulder arthrodesis

5) Humeral head resection

Figures A and B show loss of fixation of a proximal humerus fracture. The most appropriate treatment for this scenario is a humeral arthroplasty, as the tenuous blood supply of the proximal humerus is likely chronically disrupted, leading to osteonecrosis and poor healing potential of the proximal humerus.
Traditionally, hemiarthroplasty was performed for these presentations, but reverse total shoulder arthroplasty has emerged as a potentially better
treatment method, especially if the rotator cuff function/status is unknown or poor.
According to the referenced article by Norris et al, delayed shoulder hemiarthroplasty decreased shoulder pain in 95% of patients but warned of technical difficulties and limited postoperative range of motion. A total shoulder arthroplasty is needed if glenoid erosion from the screw(s) or bone occurs.

During the ilioinguinal approach to the pelvis, the corona mortis artery must be identified and ligated if present. The corona mortis artery joins the external illiac artery with which other major artery?

1) Pudendal

2) Deep illiac circumflex

3) Hypogastric

4) Obturator

5) Testicular

The "corona mortis" (translated as “crown of death”) artery is a vascular variant that joins the external illiac and the obturator artery as it crosses the superior pubic ramus. Tornetta et al did a study where "fifty cadaver halves were dissected to determine the occurrence and location of the corona mortis. Anastomoses between the obturator and external iliac systems occurred in 84% of the specimens. Thirty-four percent had an arterial connection, 70% had a venous connection, and 20% had both. The distance from the symphysis to the anastomotic vessels averaged 6.2 cm (range, 3-9 cm)." The corona mortis can be injured in superior ramus fractures and iatrogenically while plating pelvic ring injuries using the ilioinguinal approach.

A 26-year-old male sustains a femoral shaft fracture treated with the implant shown in Figure A. Postoperatively, what muscular deficits can be expected at medium and long-term follow-up?
1) Weakness with hip abduction and knee flexion

2) Weakness with hip abduction and knee extension

3) Weakness with knee flexion and knee extension

4) Weakness with hip external rotation and hip abduction

5) Weakness with hip external rotation and hip flexion

Figure A shows a femoral shaft fracture treated with an antegrade femoral nail. Long term deficits are weakness with knee extension (quadriceps) and hip abduction (glutei muscles).
The referenced study by Kapp et al noted long term quadriceps weakness as well as decreased bone mineral density in the femur (femoral neck by 9%, the lateral cortex by 20% and the medial cortex by 13%). It is unclear whether this is due to the injury, treatment, or a combination of both.
The second referenced study by Archdeacon et al also noted weakness in hip abduction, which showed time dependent improvement. He reports that increased early ipsilateral trunk lean is associated with worse recovery of abduction strength.

A 33-year-old male sustains the injury seen in Figure A as a result of a high-speed motor vehicle collision. Based on this image, what is the most likely acetabular fracture pattern?
1) Both column

2) Anterior column

3) Anterior column posterior hemitransverse

4) Transverse

5) T-type

The radiograph in Figure A shows a transverse acetabulum fracture. The iliopectineal (anterior column) and ilioischial lines (posterior column) are interrupted, revealing bicolumnar involvement; however, this is different than the both column fracture, as a transverse pattern has articular surface still in continuity with the axial skeleton via the sacroiliac joint.
The referenced article by Patel et al showed a wide variation of inter and intra-observer agreement in interpreting radiographs of acetabular fractures, with high agreement for basic radiographic classification and only slight to moderate agreement for other radiologic variables such as impaction.
The other referenced article by Letournel is a great review article regarding the initial classification of these fractures as well as a quick summary of his outcomes.

A 56-year-old carpenter sustains the closed injury seen in Figures A, B, and C. After temporary spanning external fixation is performed and soft tissue conditions improve, what strategy provides the optimal fixation for this fracture pattern?
1) Anatomic lateral locking plate

2) Posteromedial and lateral plates

3) Anatomic medial locking plate

4) Conversion of the spanning external fixator to a hinged external fixator

5) Posterior buttress plate

Figures A and B show a bicondylar tibial plateau fracture, with a typical appearing lateral fracture line and a posteromedial fracture line. The posteromedial sheared fracture piece is difficult, and/or sometimes impossible, to achieve appropriate stable fixation with a single lateral locking plate, as there will be limited screw purchase and fixation into the posteromedial fragment.
The referenced article by Georgiadis notes that a dual incision approach is safe and is associated with improved outcomes over their historical comparisons.
They describe the dual incisions and approaches in length, and review risks/issues with each approach.
The other referenced study by Bhattacharyya et al notes that these fractures have a typical appearance of the posteromedial fracture piece and that articular reduction quality is correlated with short-term results. They recommended buttress-type fixation of these fracture pieces.

A 31-year-old male sustains an irreducible ankle fracture-dislocation with the foot maintained in an externally rotated position. An AP and lateral radiograph are shown in figures A and B respectively. The attempted post reduction AP and lateral are shown in C and D. What structure is most likely preventing reduction?
1) Anterior-inferior tibiofibular ligament

2) Posterior-inferior tibiofibular ligament

3) Peroneus brevis tendon

4) Posterolateral ridge of the tibia

5) Flexor hallucis longus tendon

As described by Hoblitzell et al, the so-called "Bosworth fracture-dislocation" is a rare fracture-dislocation of the ankle where the fibula becomes entrapped behind the tibia and becomes irreducible. It can cause compartment syndrome, as reported by Beekman and Watson.
Hoblitzell et al stress the importance and difficulty of recognizing these injuries. Standard radiographs are difficult to interpret due to the often severe external rotation of the foot. Prompt treatment, though can lead to good results in patients. The posterolateral ridge of the distal tibia hinders reduction and reduction often requires an open technique
Mayer and Evarts stated AP and mortise radiographs can be hard to interpret due to the external rotation posture of the foot. In their series a closed reduction consisting of traction and medial rotation applied to the foot while the fibular shaft is pushed laterally was successful in 3/4 patients.

A 37-year-old female sustains the injury seen in Figures A and B. At long-term follow up, degeneration of which of the following joints has been shown to have the highest rate of patient symptoms?
1) Tibiotalar joint

2) Talonavicular joint

3) Calcaneocuboid joint

4) Lisfranc joint

5) Subtalar joint

Figures A and B show a medial subtalar dislocation, which is more common than a lateral dislocation (65% vs. 35%).
The referenced article by Bibbo et al looked at long-term follow up of these patients, and noted that radiographic degeneration of the ankle and subtalar joints were 89%, although 31% of ankle joints were symptomatic and 68% of subtalar joints were symptomatic. Midfoot degeneration was seen radiographically in 72% (15% symptomatic).

In treating a lateral split-depression type tibial plateau fracture, which of the following adjuncts has been shown to have the least articular surface subsidence when used to fill the bony void?

1) Crushed cancellous allograft

2) Hydroxyapatite

3) Calcium phosphate cement

4) Autogenous iliac crest

5) Bisected diaphyseal humeral allograft

In treating tibial plateau fractures, calcium phosphate has been shown to have the least amount of articular subsidence on follow-up examinations.
The referenced study by Russell et al noted a significantly increased rate of subsidence at 12 months with autograft as compared to calcium phosphate cement (in types I-VI).
The other referenced study by Lobenhoffer et al noted improved radiographic outcomes and earlier weightbearing with usage of calcium phosphate cement.

The pelvic spur sign on plain radiography is indicative of the following injuries?

1) Transtectal transverse acetabular fracture

2) Vertical shear pelvic ring injury

3) Displaced H-type sacral fracture

4) Both column acetabular fracture

5) Anterior-posterior type III pelvic ring injury

The pelvic spur sign is indicative of a both column acetabular fracture. It is best seen on an AP or obturator oblique x-ray. The spur is the intact portion of the ilium, still attached to the axial skeleton and seen posterosuperior to the displaced acetabulum (typically medially displaced).
Illustration A shows the spur sign (arrows) on a CT image, while illustration B shows an obturator oblique of the pelvis and the spur sign is shown with the long tailed arrow (on the left of the image).

A 33-year-old male sustains a distal humerus fracture and is treated with open reduction and internal fixation of the distal humerus with olecranon osteotomy. A postoperative radiograph is shown in Figure A. A new deficit of the anterior interosseous nerve is now noted in the recovery room. What physical exam finding would be expected with this nerve injury?
1) Inability to flex radiocarpal joint

2) Loss of sensation over palmar aspect of thumb

3) Loss of sensation over dorsal hand first webspace

4) Inability to abduct index finger

5) Inability to flex thumb interphalangeal joint

A deficit in the anterior interosseous nerve (AIN) would result in an inability to flex the interphalangeal joint (IPJ) of the thumb.
Injury to the AIN can be seen with K-wires that penetrate through the anterior cortex of the proximal ulna, such as mentioned above. The AIN is a branch of the median nerve that provides motor function to forearm/hand. It branches off from the median nerve 4 cm distal to the medial epicondyle, passes between the 2 heads of the pronator teres, travels through the forearm anterior to the interosseous membrane between the flexor pollicis longs (FPL) and flexor digitorum profundus (FDP), and then terminates in the pronator quadratus (PQ). The nerve gives of branches to the FDP, FPL, and PQ enabling for flexion of the distal phalangeal joint of the index and middle fingers, flexion of the IPJ of the thumb, and aids with pronation of the forearm, respectively.
Injury to the nerve will result in weakness in motor function to these muscles.
Mekail et al. reviewed the anterior approach to the proximal radius in order to describe and identify important neurovascular and musculoskeletal structures in the area. They were specifically aiming to determine the safest anatomic orientation for plate and screw fixation in regards to the posterior interosseous nerve. The authors, however, did discuss that medial plating was especially dangerous to the AIN, and significantly increased the risk of iatrogenic injury to the branch sent to the FPL.
Parker et al. reported a case report in a patient who experienced an AIN deficit postoperatively after tension banding of an olecranon fracture.
Intraoperatively, there were multiple passes of the K-wires in an attempt to find purchase in the anterior cortex of the ulna. The authors believed that during these passes, the nerve was injured and concluded that placing K-wires should not occur without radiologic visualization.
Figure A is a postoperative lateral radiograph after tension banding of the olecranon. Perforation of the anterior ulnar cortex can be seen by the K-wire which can cause damage to the AIN nerve. Illustration A is a schematic of the path of the AIN, its branches, and its function.
Incorrect Answers:
Answer 1: Both ulnar and median nerves provide innervation muscles that flex the radoiocarpal joint.
Answer 2: AIN has no cutaneous sensory fibers. Median nerve disruption would result in this deficit.
Answer 3: Disruption of the superficial radial serve would result in this deficit.. Answer 4: Disruption of the deep branch of the ulnar nerve would result in this deficit.

A computed tomography (CT) scan has been shown to be indicated for evaluation of all of the following aspects of acetabular fractures, EXCEPT:

1) Determination of surgical planning

2) Intra-articular loose bodies

3) Marginal impaction

4) Fracture piece size and position

5) Determination of pre-existing degenerative changes

CT scanning is indicated in acetabular fractures for determination of surgical approach and techniques, evaluation of marginal impaction and presence of intra-articular loose bodies (especially after hip dislocation), and evaluation of fracture piece sizes and relative positions.
Kellam et al reviewed their initial experience with CT scanning and acetabular fractures, and noted a 25% change in surgical planning when CT was utilized versus plain radiographs; they also noted the ability to detect marginal impaction and fracture size/position was improved with CT.

A 69-year-old woman falls while getting out of her car and lands on her right shoulder sustaining a 4-part proximal humerus fracture. She subsequently undergoes surgery to treat the fracture, with immediate postoperative radiographs shown in Figure A. Six months following surgery, she denies shoulder pain, but she is unable to actively raise her hand above her shoulder. Which of the following is the most likely cause of this limitation?
1) Joint infection

2) Retroversion of the prosthesis

3) Glenoid arthritis

4) Axillary nerve injury

5) Greater tuberosity malunion

The radiograph demonstrates a humeral hemiarthroplasty. Malunion of the greater tuberosity is a known complication of this procedure, and the most likely cause for loss of shoulder elevation.
Frankle et al in 2004 reported a 25% rate of greater tuberosity malunion. They discuss surgical techniques to improve fixation of the tuberosities following hemiarthroplasty for proximal humerus fractures.
Frankle et al in 2002 evaluated 5 different techniques to reattach the tuberosities following shoulder hemiarthroplasty in human cadavers. Findings suggested that a circumferential medial cerclage should be placed around the tuberosities to enhance the stability of the tuberosity repair.
Bosch et al reviewed 39 consecutive 3 or 4 part proximal humerus fractures that were treated with either primary hemiarthroplasty or secondary hemiarthroplasty following a primary ORIF. Patients who underwent primary
hemiarthroplasty reported better clinical outcomes. The authors concluded that elderly patients with 3 or 4 part humerus fractures are best treated with early arthroplasty.

An acetabular fracture with all segments of the articular surface detached from the intact posterior ilium is defined as what fracture pattern?

1) Transverse

2) Both column

3) Anterior column posterior hemitransverse

4) Posterior column with posterior wall

5) Anterior column with anterior wall

A both column acetabular fracture is defined as an acetabular fracture with no articular surface in continuity with the remaining posterior ilium (and therefore, axial skeleton). The spur sign is a radiological sign seen with these fractures, and is the posterio-inferior aspect of the intact posterior ilium. The spur sign and other radiographic findings consistent with a both column acetabular fracture can be seen in Illustration A (AP), Illustration B (obturator oblique), and Illustration C (iliac oblique).

A large posteromedial tibial plateau fracture pattern, as seen with the bicondylar tibial plateau fracture shown in Figures A and B, is important to recognize because of which of the following factors?
1) Association with posteromedial corner of the knee injury

2) Association with anterior tibial artery injury

3) Possible need for dual plate fixation

4) Possible need for single extensile anterior approach to the knee

5) Increased risk of deep venous thrombosis

Figures A and B show a bicondylar tibial plateau fracture with a large posteromedial fracture piece. This has clinical importance, as currently available plate/screw constructs often have poor fixation of this fracture segment, and this pattern often requires a second, posteromedial, approach and placement of a second plate/screw construct.
The referenced article by Barei et al notes a prevalence of posteromedial fracture pieces of nearly 33% of all bicondylar tibial plateau fractures. They also recommend supplementary or alternative fixation techniques when this pattern is recognized.
The referenced article by Higgins et al notes a 59% incidence of this fracture pattern (consisting of nearly 25% of the total joint surface) in bicondylar tibial plateau fractures, and recommends appropriate fixation to combat the vertical shear instability through a separate approach.
The last referenced study by Higgings et al notes a significantly increased rate of late fracture displacement in a biomechanical model with a single lateral locking plate as compared to a dual plate construct.

At the elbow, the anterior bundle of the medial collateral ligament inserts at which site?

1) Radial tuberosity

2) 3mm distal to the tip of the coronoid

3) Anteromedial process of the coronoid

4) Medial border of the olecranon fossa

5) Radial side of ulna at origin of annular ligament

The anterior bundle of the medial collateral ligament of the elbow inserts at the anteromedial process of the coronoid, also known as the sublime tubercle.
Fractures at this site have been shown to have worse results with nonoperative
treatment, due to increased rates of instability and post-traumatic arthrosis.
The referenced articles by Ring and Steinmann are great reviews of the topic of coronoid fractures. They review the diagnosis, treatment options, rehabilitation, and outcomes of these injuries. They focus on the importance of the coronoid in elbow stability, especially with base fractures, or ones that involve the sublime tubercle.
Illustration A depicts the anterior bundle of the MCL inserting at the sublime tubercle.

In the Lauge-Hansen classification system, a pronation-abduction ankle fracture has what characteristic fibular fracture pattern?

1) Transverse fracture below the level of the syndesmosis

2) Short oblique fracture running from anteroinferior to posteriosuperior

3) Short oblique fracture running from posteroinferior to anteriosuperior

4) Comminuted fracture at or above the level of the syndesmosis

5) Wagstaff fracture

In the Lauge-Hansen classification, the characteristic fibular fracture pattern in a pronation-abduction injury is a comminuted fibular fracture above the level of the syndesmosis. In the first stage of this injury pattern, the deltoid fails in tension, or an avulsion fracture of the medial malleolus occurs. In the second stage, the anterior inferior tibiofibular ligament ruptures, or a small bony avulsion of this ligament's insertion/origin occurs. The final stage includes the creation of a comminuted fibular fracture above the level of the syndesmosis.
The referenced article by Siegel et al noted that extraperiosteal bridge plating of these ankle injuries was safe and had excellent radiographic and clinical outcomes at final follow-up.

A 38-year-old male sustains the closed injury shown in Figures A and B. When treating this injury with an intramedullary nail, addition of blocking screws into which of the following positions can prevent the characteristic malunion deformity?
1) Anterior to the nail in the proximal segment; medial to the nail in the proximal segment

2) Anterior to the nail in the proximal segment; lateral to the nail in the proximal segment

3) Posterior to the nail in the proximal segment; lateral to the nail in the proximal segment

4) Anterior to the nail in the distal segment; lateral to the nail in the distal segment

5) Posterior to the nail in the distal segment; medial to the nail in the proximal segment

Figures A and B show a proximal tibia fracture, which is prone to malreduction/malunion into a characteristic valgus and procurvatum (apex anterior) deformity. Placement of screws in this instance posterior to the nail (medial to lateral) and lateral to the nail (anterior to posterior) in the proximal segment will prevent iatrogenic malalignment.
Intramedullary nails will not effect a reduction in metaphyseal proximal tibia fractures. Valgus and apex anterior deformities in these injuries may be caused by deforming muscular forces, limb positioning in hyper flexion, as well as iatrogenic deformity created by improper nail insertion technique. Blocking (Poller) screws are utilized to redirect intramedullary nails by creating an artificial cortex to guide the nail into appropriate position.
The referenced biomechanical study by Krettek et al noted that addition of blocking screws added increased stability to metaphyseal fractures.
Ricci et al noted no malalignment intraoperatively or at final follow-up of proximal tibia fractures treated with intramedullary nails if blocking screws were used.

In an uninjured proximal tibia which statement best describes the shape and position of the medial tibial plateau relative to the lateral tibial plateau?

1) More concave and more proximal

2) More convex and more proximal

3) More concave and more distal

4) More convex and more distal

5) Symetric in conture and more distal

The medial tibial plateau is more concave and more distal relative to the lateral tibial plateau.
Watson et al report "the medial tibial plateau has a more concave shape and is larger in both length and width than the lateral tibial plateau, which has a slightly convex shape. The lateral tibial plateau lies proximal to the medial plateau. The convexity of the lateral plateau helps differentiate it from the medial plateau on a lateral radiograph of the proximal tibia."
Illustration A shows the relative concavity of the medial and lateral proximal tibia.

On average, the radial nerve travels from the posterior compartment of the arm and enters the anterior compartment at which of the following sites?

1) Spiral groove of the humerus

2) At the arcuate ligament of Osborne

3) 10 cm distal to the lateral acromion

4) 10 cm proximal to radiocapitellar joint

5) At the origin of the deep head of the triceps

The radial nerve enters the anterior compartment through the intercompartmental fascia on average 10 cm proximal to the radiocapitellar joint. It has never been found to remain in the posterior compartment within
7.5cm of this joint, leading to this area being named the "safe zone". During the posterior approach to the humerus, the radial nerve is found in the spiral groove in the middle third of the posterior humerus, medial to the lateral head and proximal to the deep head of the triceps. When performing an ORIF of a
humerus fracture from a posterior approach it should be identified and protected.
Illustration A shows the radial nerve as seen during the posterior approach to the humerus. Illustration B shows the radial nerve along with a ruler showing the transition at 10cm proximal to the radiocapitellar joint.

A 45-year-old female pedestrian is hit by an automobile. A clinical photo and radiograph are shown in Figure A and B. What is the most
important factor in a surgeon's decision of determining between limb salvage and amputation?
1) Level of education

2) Lack of plantar sensation

3) Contralateral lower extremity open fracture(s)

4) Severity of soft tissue injury

5) Amount of tibial bone loss

The clinical photo and radiograph are consistent with a Grade III open tibia fracture.
The referenced study by the LEAP group reviews 527 patients with severe lower extremity fractures and found that the most important factor in determining the ability to salvage the extremity remains the severity of the soft tissue injury of that extremity. Bone loss has been shown to have no effect on the eventual outcome (amputation versus salvage). Similarly, plantar sensation at presentation has no bearing on final outcome, and in the LEAP study, often either partially or fully returned.

During an open reduction internal fixation of a humerus fracture using the posterior approach, a surgeon can identify the posterior antebrachial cutaneous nerve and trace it proximally to which of the following nerves?

1) Ulnar

2) Musculocutaneous

3) Radial

4) Median

5) Axillary

The posterior antebrachial cutaneous nerve (PABCN) branches from the radial nerve in the axilla.
The posterior antebrachial cutaneous nerve branches from the radial nerve just distal to the posterior brachial cutaneous nerve (PBCN) in the axilla and they course through the arm in closely to each other. In the proximal forearm, the posterior antebrachial cutaneous nerve is found on the lateral border of the brachioradialis muscle. The terminal branches innervate the posterior aspect of the forearm distally.
Gerwin et al recommended identifying the lower lateral brachial cutaneous nerve first when approaching the humerus posteriorly. It can be traced proximally to safely identify the radial nerve before any proximal exposure of the shaft is done. Gerwin et al in their review also found that the radial nerve crossed the posterior aspect of the humerus an average of 20.7 +/- 1.2 centimeters proximal to the medial epicondyle to 14.2 +/- 0.6 centimeters
proximal to the lateral epicondyle.
In their review, Zlotolow et al. review the multiple surgical approaches to the humerus.
Illustration A depicts the course of the PABCN and its relation to the PBCN and the radial nerve

A 37-year-old male sustains the closed injury seen in figure A. What technique can be utilized to avoid the characteristic deformity seen in this fracture pattern if an intramedullary nail is used for treatment?
1) Medial starting point

2) Lateral starting point

3) Aiming the nail posteriorly in the proximal segment

4) Anterior blocking screw in the proximal segment

5) Medial blocking screw in the proximal segment

Figure A shows a proximal metaphyseal tibia fracture, which characteristically is malreduced into valgus and apex anterior (procurvatum) deformity. Some techniques to avoid these deformities are: provisional reduction with unicortical plates/clamps, semi-extended nailing, suprapatellar nailing, usage of a more lateral starting point, usage of an external fixator or femoral distractor, and usage of blocking screws - posterior screw and/or a lateral screw in the proximal segment.
The two referenced studies draw attention to the high rate of malalignment with nailing of this fracture pattern; the first study reported a 58% malalignment rate, and the second reported an 84% rate (>5 degrees in either coronal or sagittal planes).

A 19-year-old male sustains the isolated, closed injury seen in Figure A. He is subsequently treated as shown in Figure B. When utilizing this technique, what forces are generated at the articular surface?
1) Neutralization

2) Torque

3) Two-point bending

4) Shear

5) Compression

Figure A and B show a simple transverse olecranon fracture appropriately treated with a tension-band construct. This construct converts distraction forces at the joint generated by the pull of the triceps into compression forces. The change of force into compression requires active motion of the elbow extensor mechanism.

Antegrade femoral nailing has an increased rate of which of the following when compared to retrograde femoral nailing?

1) Varus malalignment

2) Union rate

3) Operative time

4) Subsequent operative procedures

5) Hip pain

In the referenced study by Ricci et al, antegrade femoral nailing was shown to have an increased rate of hip pain as compared to retrograde femoral nailing, while having a similar rate of union, time to union, rate of malalignment, and operative time. Hip pain was signficantly higher in the antegrade nailing group, while knee pain was significantly greater in the retrograde group.
The referenced study by Winquist et al noted a 99.1% union rate with intramedullary nailing.
The referenced study by Moed et al noted a 6% nonunion rate in non-reamed retrograde femoral nailing with nail dynamization at 6-12 weeks and early weightbearing.

A 25-year-old male is involved in a motor vehicle accident and presents with the injury shown in Figure A. Early fixation of this fracture pattern is associated with all of the following EXCEPT?
1) Decreased length of hospital stay

2) Improved functional outcome

3) Greater organ dysfunction

4) Higher likelihood of being discharged to home as opposed to a rehab facility

5) Improved fracture reduction

Early fixation of acetabular fractures is associated with lesser organ dysfunction, so therefore answer three is not true.
Plaisier et al showed the timing of acetabular and pelvic ring fracture fixation greatly impacted patient outcome. Patients who had fixation within 24 hours of injury showed shorter length of stay in the hospital and ICU (decreased number of ventilator days), improved functional outcomes including a highly likelihood of being discharged to home as opposed to a rehabilitation facility, and lesser organ dysfunction.
The reference by Matta et al is a classic article that shows that patients fixed within 3 weeks of injury showed both a higher rate of anatomical reduction and lower overall complication rate than patients with similar fracture patterns treated after 3 weeks.

A 33-year-old man requires a transfemoral amputation because of a mangling injury to his leg. Six months after the amputation he has persistent difficulty with ambulation because his distal femur moves into a subcutaneous position in his lateral thigh. It persists despite a
well-fitted prosthesis. What technical error is the most likely cause of his dysfunction?

1) Inadequate posterior skin flap

2) Inadequate anterior skin flap

3) Failure to bevel the distal femur

4) Lack of abductor myodesis to femur

5) Lack of adductor myodesis to femur

Adductor myodesis is a critical part of a transfemoral amputation. If it is not performed, then the abductors and hip flexors can cause the femur to abduct, leading to severe problems with gait. The gait disturbance persists despite proper prosthetic fitting. A transfemoral amputation is usually performed with equal anterior and posterior flaps.
Pinzur et al highlight the fact that amputations are reconstructive procedures and should leave the patient with a functional residual limb.

An 18-year-old football player presents to the emergency department after sustaining an ankle injury. His radiograph is shown in figure A. What is the most appropriate definitive treatment?
1) Open reduction and internal fixation of the medial malleolus with syndesmosis reduction and suture-button repair

2) Repair of the anterior talo-fibular ligament

3) Open reduction internal fixation of the fibula with syndesmosis reduction and suture-button repair

4) Open reduction internal fixation of the medial malleolus and fibula

5) Open reduction internal fixation of the fibula and medial malleolus with syndesmosis reduction and suture-button repair

The radiograph demonstrates an ankle fracture-dislocation. There is diastasis of the distal tibia and fibula, indicating a syndesmosis injury.
Zalavras et al stated failure to recognize and treat the syndesomsis injury leads to inferior outcomes, and should be assessed after fibula and medial malleolar fixation. Treatment of choice is reduction of the syndesmosis and fixation.

A patient sustains a severe lower extremity injury. What can be said about his outcome at 2 years if he chooses reconstruction over amputation?

1) He has a higher risk of rehospitalization

2) He has a higher chance of returning to work

3) He will have a higher overall SIP (Sickness Impact Profile) score

4) His psychosocial SIP score will improve with time

5) He will have a better SIP score if he did not complete high school

Severe lower extremity injury patients undergoing reconstruction have a higher rate of rehospitalization at 2 years. This question is based on data published by the LEAP study group, a multi-centered study of severe extremity injuries treated with either amputation or reconstruction.
Bosse et al found that at 2 years the SIP score and return to work were not statistically signficantly different between amputation and reconstruction groups. Reconstruction patients had a higher risk of rehospitalization. The psychosocial subscale of SIP did not improve with time. Risk factors for poorer SIP score were: rehospitalization for a major complication, a low educational level, nonwhite race, poverty, lack of private health insurance, poor social-support network, low self-efficacy (the patient's confidence in being able to resume life activities), smoking, and involvement in disability-compensation litigation.
MacKenize et al evaluated factors influential in returning to work (RTW) after severe lower extremity injury. Characteristics that correlated with higher rates of RTW included younger age, higher education, higher income, the presence of strong social support, and employment in a white-collar job that was not physically demanding. Receipt of disability compensation had a strong negative effect on RTW.

Lateral malleolus fractures can be treated with a variety of techniques, including posterior antiglide plating or lateral neutralization plating. What is an advantage of using lateral neutralization plating instead of posterior antiglide plating?

1) Decreased joint penetration of distal screws

2) Increased rigidity

3) Decreased need for delayed hardware removal

4) Decreased peroneal irritation

5) Improved distal fixation

Posterior antiglide plating is a technique that involves placement of a plate on the posterior aspect of the distal fibula, using the plate as a reduction tool and direct buttress against distal fracture fragment displacement.
Schaffer et al showed from a biomechanical standpoint that posterior antiglide plating was superior to lateral neutralization plating for distal fibula fracture fixation.
Weber et al reported a (30/70) 43% rate of plate removal secondary to peroneal discomfort. In addition, peroneal tendon lesions were found in 9 of the 30 patients.

Varus malalignment after a talar neck fracture with medial comminution causes a decrease in what motion?

1) Tibiotalar dorsiflexion

2) Tibiotalar plantarflexion

3) Subtalar eversion

4) Subtalar inversion

5) Internal rotation

Varus alignment at the talar neck results in a decrease in subtalar eversion before impingement occurs. Varus talar neck alignment can cause a fixed internal rotation position of the midfoot as the navicular follows the talar head. This can lead to a more rigid hindfoot which is specifically manifested as a decreased eversion range of motion.
Illustration A is a diagram of the hindfoot that shows how malalignment can affect the hindfoot.
Herscovici et al review the appropriate management of complex ankle and hindfoot injuries in this instructional course lecture.
Daniels et al performed a cadaveric study where they osteotomized the talar neck and then studied ankle motion with and without removal of a medially
based wedge of bone. They found that subtalar eversion was specifically decreased.
Sanders et al found that secondary reconstructive procedures following talar neck fractures were most commonly performed to treat subtalar arthritis or misalignment.

Which of the following nonunions is appropriately treated with exchange reamed nailing without bone graft augmentation?

1) Infected tibial shaft nonunion 6 months status post intramedullary nail fixation

2) Oligotrophic humeral shaft nonunion 7 months status post non-operative management

3) Hypertrophic tibial shaft nonunion 7 months status post intramedullary nail fixation

4) Comminuted open tibial shaft nonunion with segmental bone loss 8 months status post intramedullary nail fixation

5) Supracondylar femoral shaft nonunion 6 months status post intramedullary nail fixation with 4 distal locking screws

Exchange nailing is indicated for nonunions of diaphyseal femoral and tibia fractures in the absence of infection, comminution, or segmental bone loss. Hypertrophic nonunions need better stability (increased nail diameter) to
achieve union. Where as atrophic nonunions often need better biology (bone graft, flap coverage, etc.)
The referenced article by Brinker et al reviews the indications for exchange nailing. They argue, on the basis of the available literature, that exchange nailing is an excellent choice for aseptic nonunions of noncomminuted diaphyseal femoral and tibia fractures.
Zelle et al. demonstrated 95% success with reamed exchange nailing for the treatment of aseptic tibial shaft nonunions that were initially treated with nonreamed intramedullary nailing.

A 32-year-old man presents to the emergency department with a humeral shaft fracture. He has wrist drop as well as impaired finger and thumb extension. Which motor function would be expected to recover last?

1) Elbow extension

2) Forearm supination

3) Wrist extension in radial deviation

4) Middle finger MCP extension

5) Index finger MCP hyperextension

The patient is presenting with radial nerve palsy secondary to his humerus fracture. Motor recovery proceeds in a proximal to distal direction.
Abrams et al detailed the order of innervation of the radial nerve and found the following order (proximal to distal): brachioradialis, extensor carpi radialis longus, supinator, extensor carpi radialis brevis, extensor digitorum communis, extensor carpi ulnaris, extensor digiti quinti, abductor pollicis longus, extensor policis longus, extensor policis brevis, and extensor indicis proprius.
Branovacki et al found a slightly different pattern: brachioradialis, extensor carpi radialis longus, superficial sensory, extensor carpi radialis brevis, supinator, extensor digitorum/extensor carpi ulnaris, extensor digiti minimi, abductor pollicis longus, extensor pollicis brevis, extensor pollicis longus and extensor indicis proprius.
While both extensor digitorum and extensor indicis proprius extend the index
finger MCP joint, only extensor indicis proprius hyperextends the index finger past neutral.

A 22-year-old female is involved in a motor vehicle collision and sustains the injury shown in Figures A through D. According to these images, what is the acetabular fracture classification?
1) Anterior column posterior hemitransverse

2) Both column

3) Transverse

4) Transverse with posterior wall

5) Anterior column

Figures A through D show a comminuted both column acetabular fracture. In this injury, both columns are involved, with the acetabulum losing all connection to the axial skeleton (sacrum). This differentiates it from all other patterns, where at least part of the acetabular cartilage maintains connection to the sacrum.
Figure C shows the ischial spur, which is classically known as the spur sign and most easily seen on the obturator oblique radiograph.
Incorrect Answers:
Answer 1: This injury has axial skeleton attachment to the acetabular cartilage through the posterior column.
Answer 3: This injury has axial skeleton attachment to the acetabular cartilage through the anterior and posterior columns.
Answer 4: This injury has axial skeleton attachment to the acetabular cartilage through the anterior column as well as the posterior column, depending on fracture pattern.
Answer 5: This injury has no posterior column involvement, and therefore the posterior column maintains the axial skeleton attachment to the acetabulum.

A 27-year-old man sustains a displaced femoral neck fracture and undergoes urgent open reduction internal fixation. What is the most prevalent complication after this injury?

1) Flexion contracture

2) Hip instability

3) Nonunion

4) Abductor lurch

5) Osteonecrosis

Femoral neck fractures in young patients are difficult to treat, and AVN is a significant concern. Despite advances in both imaging and implants, this injury often leads to functional impairment.
Haidukewych et al followed treatment of femoral neck fractures in young
patients. They found almost 10% of displaced fractures were associated with the development of nonunion, where as 27% were associated with the development of osteonecrosis. Their results were influenced by fracture displacement and the quality of reduction. Varus malreduction most closely correlates with failure of fixation after reduction and cannulated screw fixation.
Swiontkowski reviews both the treatment and post operative complications in intracapsular hip fractures. In this Current Concept Review, the rate of AVN was discussed as being related to the pre-operative degree of displacement seen on radiographs.
Incorrect Responses:
Answers 1 & 4: While each of these complications do occur, they are less common and are related to the approach and degree of surgical dissection. Answer 2: Hip instability is relatively uncommon.
Answer 3: Nonunion rate is significant but lower than the AVN rate. It is has been associated with the degree of initial displacement and varus malreduction.

A patient with an intertrochanteric hip fracture undergoes reduction and dynamic hip screw application. The post-operative radiographs demonstrate that the lag screw is superior in the femoral head with a tip-apex distance of 40 millimeters. This patient is at increased risk of what complication?

1) lag screw cutout

2) osteonecrosis

3) osteoarthritis

4) peri-prosthetic fracture

5) lag screw breakage

Baumgaertner et al in their classic study in 1995 determined that the position of the lag screw in the femoral head influenced the risk of cutout of a dynamic hip screw construct in treatment of intertrochanteric fractures. They had no cutouts if the tip-apex distance on the combined AP and lateral radiographs was less than 25 millimeters. Subsequent studies demonstrated a decreased cutout rate once people were aware of the tip-apex distance importance.

A 37-year-old male sustains the injury shown in Figure A following a motorcycle crash. During the approach, what limb position minimizes tension placed on the sciatic nerve?
1) Hip at 45 degrees, knee flexed to 90 degrees

2) Hip at 60 degrees, knee flexed to 90 degrees

3) Hip at 90 degrees, knee extended

4) Hip at 0 degrees, knee flexed to 90 degrees

5) Hip at 90 degrees, knee flexed to 90 degrees

During the Kocher-Langenbeck approach, the sciatic nerve is at the least amount of tension with the hip extended and the knee flexed to 90 degrees.
The CT exhibits a posterior wall acetabular fracture, which is fixed via a Kocher-Langenbeck approach. The sciatic nerve, which comes out of the greater sciatic notch, is at the least amount of tension with the hip extended and knee flexed to 90 degrees.
Borrelli et al examined the intraneural pressure of the sciatic nerve with the hip and knee in various different positions. The authors noted that the highest tension was placed on the sciatic nerve when the hip was flexed to 90 degrees and the knee was fully extended. As a result, the leg is typically position with the hip in extension (or minimal flexion) and the knee in about 90 degrees of flexion when performing acetabular surgery via a posterior approach.
Figure A shows an axial pelvic CT cut with a posterior wall acetabular fracture. Incorrect answers:
Answer 1,2,3,5: With any degree of hip flexion, it places tension on the sciatic
nerve, answer 4 (hip flex to 90 and knee fully extended), specifically places the highest amount of intraneural pressure on the nerve.

A 21-year-old male sustains the open injury shown in Figure A, which is associated with a 12 centimeter laceration over the fracture site. This laceration is able to be closed during initial surgery. What adjunct treatment has been shown to improve outcomes when using an intramedullary nail?
1) rhBMP-7

2) Adjunctive fracture plating

3) Calcium phosphate

4) Antibiotic impregnated cement beads

5) rhBMP-2

rhBMP-2 has been shown in two randomized controlled studies to have improved clinical outcomes in grade III open tibial fractures.
Swiontkowski et al and Govender et al have shown in two separate clinical studies that use of this product has: significantly fewer invasive interventions (e.g., bone-grafting and nail exchange), significantly faster fracture-healing than did the control patients, increased healing (union) rates, fewer hardware failures, fewer infections, and faster wound-healing (83% compared with 65%
had wound-healing at six weeks).

Which of the following statements is true regarding treatment of intertrochanteric hip fractures with an intramedullary nail versus a sliding hip screw?

1) The use of intramedullary nail has increased in the last ten years

2) The use of sliding hip screws has increased in the last ten years

3) Medicare reimbursement is more for a sliding hip screw

4) Intramedullary nails have demonstrated superior outcomes in randomized-controlled studies

5) Sliding hip screw is superior for treatment of reverse obliquity intertrochanteric fractures

The use of intramedullary (cephalomedullary) devices has increased in the last ten years despite a lack of evidence to support superiority over extramedullary implants (sliding hip screws)
Intertrochanteric hip fractures remain one of the most common injuries managed by Orthopaedic surgeons. The optimal form of surgical stabilization for these injuries has been a topic of debate, however several recent studies have demonstrated equivalent outcomes with long cephalomedullary nails and sliding hip screws.
Anglen et al. reviewed the database of orthopaedic surgeons taking their oral board examination. The authors found that the use of intramedullary nails for intertrochanteric hip fractures dramatically increased from 3% in 1999 to 67% in 2006. The authors calls attention to the fact that reimbursement was higher until 2010 for intramedullary nails despite a lack of evidence demonstrating superiority.
Forte et al. evaluated geographic variation in the use of intramedullary nails to treat intertrochanteric hip fractures. The authors found significant regional variation in the use of these devices despite similarities in the treatment populations.
Barton et al. conducted a Level 1 prospective randomized controlled study comparing long cephalomedullary nails with sliding hips screws in the treatment of unstable intertrochanteric fractures (AO/OTA 31-A2). The authors
found no significant difference in any of the measured variables when comparing the two devices.
Incorrect Answers:
Answer 2: The use of the sliding hip screw has decreased despite equivalence with cephalomedullary nails
Answer 3: Until 2010 Medicare reimbursement was more for cephalomedullary nails.
Answer 4: Intramedullary nails have not been shown to have superior outcomes in multiple studies
Answer 5: Sliding screws have been shown to have worse outcomes for reverse obliquity fractures

A 34-year-old man is brought to the trauma bay following a motorcycle collision with a left femoral shaft fracture and an open right tibial plateau fracture. Radiographs are provided in figures A and
B. He is proceeding to the operating room for an emergent splenectomy. The mean arterial pressure is 51 mmHg following 6 units of packed red blood cells as well as crystalloid replacement. Base deficit is 10 mmol/L. Neurosurgery is concerned for evolving subdural hematoma and is recommending serial head CT scans. Which of the following is the best immediate treatment option to address his fractures?
1) Irrigation and debridement of open tibia plateau fracture and traction stabilization of femur and tibia plateau fractures

2) Irrigation and debridement with open reduction internal fixation of tibial plateau fracture and intramedullary nail fixation of femur fracture

3) Irrigation and debridement with open reduction internal fixation of tibial plateau fracture and plate fixation of femur fracture

4) Irrigation and debridement with external fixation of tibia plateau fracture and reamed intramedullary nail fixation of femur fracture

5) Irrigation and debridement with external fixation of tibia plateau fracture and external fixation of femur fracture

Radiographs demonstrate a femoral shaft and high-energy tibia plateau fracture. The patient is medically unstable and the best treatment is expeditious debridement of the open fracture and stabilization of the fractures with definitive fixation at a later date. Early stabilization reduces the risk of cardiopulmonary complications including fat embolism syndrome.
Roberts et al recommends damage control orthopaedics emphasizing fracture stabilization without definitive surgical treatment in the unstable trauma patient. They note that this treatment method adds little physiological stress to the traumatized patient.
Turen et al discusses the importance of early fixation of long bone fractures to mobilize the multiple extremity trauma patient and mitigate cardiopulmonary complications. They note, however, that understanding of the complexities of the multiply injured patient is necessary to avoid intensive surgical treatments that are likely to adversely affect outcome.

A 79-year-old woman with osteoporosis presents with a displaced, severely comminuted olecranon fracture involving the proximal 40%. Which of the following represents the most appropriate surgical treatment?

1) Intramedullary screw

2) Kirschner wire tension band

3) Total elbow arthroplasty

4) Fragment excision and triceps advancement

5) Dorsal bridge plating

Multiple treatments exist for olecranon fractures. Tension band construct (Illustration A) and intramedullary screw or k-wire placement are typically reserved for non-comminuted olecranon fractures, whereas plate and screw
fixation (Illustration B) is used for comminuted fractures.
Hak et al review olecranon fracture treatment and state that fragment excision and triceps advancement is most appropriate in elderly, osteoporotic patients with severely comminuted fractures involving the proximal 30-40% of the olecranon.
Veillette et al state that when performing a triceps advancement for treatment of an olecranon fracture, between 50% and 70% of the olecranon articular surface can be excised without compromising elbow stability provided the coronoid and distal trochlea are preserved.
When excision and triceps advancement is performed, the triceps should be attached adjacent to the articular surface.

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Because this patient is young, substantial bilateral acetabular dysplasia is present, and the joint space is well preserved, periacetabular osteotomy is the treatment of choice (Figure 2). Arthroscopic evaluation and treatment is insufficient to address the mechanical deformity. Although a hip injection can be diagnostically helpful, it would not alter the treatment plan in this scenario. The patient’s young age would make observation and subsequent THA less desirable. Femoral osteotomies also were performed to address rotational deformity.
42

DISCUSSION: The patient has risk factors, symptoms, and signs of Ogilvie syndrome of acute colonic pseudo- obstruction. This unusual but potentially catastrophic complication is characterized by functional colonic obstruction without an associated mechanical blockage. This disorder has been associated with advanced age, male gender, the use of narcotic pain medications, and patients who have undergone hip arthroplasty. The first step in management of any complication is diagnosis, and the diagnosis is most rapidly made using radiographs that show dilation of the large intestine.

REFERENCES: Nelson JD, Urban JA, Salsbury TL, et al: Acute colonic pseudo-obstruction (Ogilvie syndrome) after arthroplasty in the lower extremity. J Bone Joint Surg Am 2006;88:604-610.
Clarke HD, Berry DJ, Larson DR: Acute pseudo-obstruction of the colon as a postoperative complication of hip
arthroplasty. J Bone Joint Surg Am 1997;79:1642-1647.

The surgical treatment of periprosthetic fractures of total hip replacement with a loose implant and progressive bone loss is associated with a high complication rate. The recent literature would favor the use of long "Wagner-type" stems, which have a long distal taper that may optimally engage the remaining femoral shaft isthmus. Plating options are problematic, because the intramedullary stem limits the ability to use screws with the plate. Using long distally fixed stems circumvents this problem by enhancing
fracture healing and creating a long-term prosthetic solution in these most difficult cases.

Scapulothoracic dissociation is a rare, violent traumatic injury in which the scapula is torn away from the chest wall but the skin remains intact. Massive swelling and ecchymosis are common. Neurovascular injury is the rule with possible subclavian or axillary artery disruption and severe partial or complete brachial plexus paralysis. The diagnosis is made on a nonrotated chest radiograph that shows significant lateral displacement of the medial scapular border from the sternal notch. A right midshaft clavicular fracture is present but is not considered the most significant finding.
REFERENCES: Ebraheim NA, An HS, Jackson WT, et al: Scapulothoracic dissociation. J Bone Joint Surg Am 1988;70:428-432.
Ebraheim NA, Pearlstein SR, Savolaine ER, et al: Scapulothoracic dissociation. J Orthop Trauma 1987;1:18-23.
Sampson LN, Britton JC, Eldrup-Jorgensen J, et al: The neurovascular outcome of scapulothoracic dissociation. J Vasc Surg 1993;17:1083-1088.
Oreck SL, Burgess A, Levine AM: Traumatic lateral displacement of the scapula: A radiographic sign of neurovascular disruption. J Bone Joint Surg Am 1984;66:758-763.

The diagnostic criteria for chronic exertional compartment syndrome is pressure >15 mm Hg at rest, or
>30 mm Hg at 1 minute post exercise, or >20 mm Hg at 5 minutes post-exercise. The anterior and lateral compartments are the only ones that meet strict diagnostic criteria for chronic exertional compartment syndrome. The superficial posterior compartment, although close to meeting criteria, is not responsible _for the patient's symptoms and falls below current thresholds for diagnosis._

The National Collegiate Athletic Association's (NCAA) 2011 revised health and safety guidelines regarding concussion management recommend no return to play on the same day of an injury. In particular, athletes sustaining a concussion should not return to play the same day as their injury. Before resuming exercise, athletes must be asymptomatic or returned to baseline symptoms at rest and have no
symptoms with cognitive effort. They must be off of medications that could mask or alter concussion symptoms. Neurocognitive testing can be a helpful tool in determining brain function even after all symptoms of concussion have resolved. With a comparison baseline test, this evaluation, in conjunction with a physician's examination, may reduce risk for second impact syndrome. The athlete's clinical neurologic examination findings (cognitive, cranial nerve, balance testing) must return to baseline before resuming exercise. Research has shown that among youth athletes, it may take longer for tested functions to return to baseline (compared with the recovery rate in adult athletes). Brain MRI scan has no role in evaluating athletes for return to play in this situation.

The clinical scenario is consistent with a femoral shaft fracture in a patient that is not stable from a neurosurgical perspective. Therefore, the most appropriate treatment at this time is placement of an external fixator.
When evaluating polytrauma patients with long bone fractures, timing of surgery must be approached considering all clinical conditions. One factor most likely to adversely affect long term outcome in polytrauma patients with severe brain injury is intra-operative hypotension; therefore, whenever a patient has a subdural hematoma that requires close observation, definitive surgery of long bone fractures should be delayed.
Flierl et al. review the immunopathophysiology of traumatic brain injury and the role of the orthopaedic surgeon in avoiding a "second hit" injury to the brain by appropriately timing the fixation of femoral shaft fractures. They recommend a multidisciplinary approach, taking individual patient-specific factors into consideration and in general, DCO principles for severe head-injured patients (GCS 3-13) and "early total care" principles for patients with mild head injury (GCS 14-15).
Illustration A is a visual representation of the treatment algorithm recommended in the article.
Incorrect Answers:
Answer choice 1 is incorrect because it does not appropriately address the fracture and there is no indication for bead placement.
Answer choices 2 and 3 are incorrect as this patient is not stable for prolonged surgery.
Answer 4 is incorrect as this patient is already under general anesthesia and external fixation is a better option than traction for stabilization of the fracture.

This patient has an aneurysmal bone cyst of the vertebra. Selective arterial embolization is a minimally invasive treatment that often succeeds in arresting the lesions. Many times it is the only treatment needed. Selective arterial embolization can also be used as part of a strategy to be followed by curettage and reconstruction to decrease operative bleeding.
This lesion will continue to expand and might cause neurologic compromise or mechanical instability. Radiation therapy poses risks of later malignant degeneration. There are other ways of treating this lesion. Radical en bloc resection may unnecessarily injure neurologic structures.
While curettage is often necessary, there is no reason to introduce the risk of radiation therapy.

**
Osteocalcin is the most specific marker of the osteoblast phenotype and is expressed only in mature osteoblasts. TGF-B is a growth factor involved in the differentiation of multiple cell lines. For bone, TGF-B plays a role in stem cell differentiation into mesenchymal stem cells along osteoblast pathways. COLIIA1 is the gene for Type II Collagen and is involved in chondrocyte differentiation. cFOS is involved in osteoclast differentiation. In regards to
bone metabolism, IL-1 stimualtes osteoclastic bone resorption.

Symptomatic stenosis of the thoracic and lumbar spine is seen in almost half of all achondroplastic patients, although not all patients require surgery.
Atlantoaxial instability is rare in achondroplasia, although it is not uncommon in other dysplasias. Basilar invagination is not present in achondroplasia.
Kyphosis is often transient in achondroplasia and rarely persists beyond the second year. Kyphosis is rarely symptomatic. Spondylolisthesis is rare in achondroplasia.

These are important concepts when balancing the knee following total knee replacement.
The distal femoral cut only effects the extension gap.
The proximal tibia cut effects the flexion and extension gaps. The posterior femoral condyle cut effects the flexion only.
Attention to these principles is very important to prevent both contractures and flexion instability. Correct Answer: The distal femoral cut only effects the extension gap.

"Ream and run" shoulder arthroplasty can allow for arthroplasty without the complications of a polyethylene glenoid. Ten-year conversion to total shoulder arthroplasty has been shown in one study to be 12%. Recovery is reported to be slower and requires more rehabilitation than arthroplasty done with glenoid resurfacing. Careful patient selection has been emphasized by the pioneering surgeon.

The clinical presentation is consistent with end-stage arthritis in a valgus knee. All of the factors listed are risk factors for peroneal nerve palsy EXCEPT female gender, which is not a risk factor.
Peroneal nerve palsy is a potential serious complication of TKA in patients with a pre-operative valgus knee deformity. Peroneal nerve palsy is likely caused by lengthening of the lateral aspect of the knee and subsequent traction on the peroneal nerve. It is generally recommended that patients be evaluated
carefully for symptoms postoperatively. If peroneal nerve palsy symptoms are discovered, the knee should be flexed to relax the tension that is effectively being placed on the nerve. If peri-operative nerve exploration or decompression is undertaken, the posterior border of the biceps-femoris tendon is the proper site of identification.
Idusuyi et al. published a retrospective review of 32 postoperative peroneal nerve palsies in thirty patients in which they identified possible risk factors. Prior proximal tibial osteotomy, lumbar laminectomy (thought to be a “double-crush” phenomenon), and preoperative valgus alignment of 12 degrees or more were all identified as risk factors. Other concerns included epidural anesthesia for postop pain control, preoperative flexion contractures and tourniquette time greater than 120 minutes also increased concern.
Favorito et al reviewed valgus total knee arthroplasty and reported that the most common complications of patients with a valgus deformity include: tibiofemoral instability (2% to 70%), recurrent valgus deformity (4% to 38%), postoperative motion deficits requiring manipulation (1% to 20%), wound problems (4% to 13%), patellar stress fracture or osteonecrosis (1% to 12%), patellar tracking problems (2% to 10%), and peroneal nerve palsy (3% to 4%).
Figure A demonstrates and AP radiograph of the knee showing end-stage arthritis with severe lateral compartment narrowing.
Incorrect Answers:

: Pre-operative flexion contracture >10 degrees is a risk factor for postoperative peroneal nerve palsy due to stretching the nerve, causing neurologic ischemia.
Answer 2: History of lumbar laminectomy is thought to place patients at risk for postoperative peroneal nerve palsy because of the "double-crush" phenomenon.
Answer 4: Valgus deformity >12 degrees increases the risk for postoperative peroneal nerve palsy due to stretching the nerve beyond functional tolerance postoperatively.
Answer 5: Epidural anesthesia has been found to be significantly associated with post-operative peroneal nerve palsy. Idusuyi et al postulate that the decrease in proprioception and sensory stimuli that accompany epidural anesthesia postoperatively allow the limb to rest in an unprotected state, thus placing the limb at risk for neurologic ischemia from local compression.

An 82-year-old woman falls and sustains the fracture shown in figure A. She denies any history of dislocation or prodromal pain prior to her fall. What is the most appropriate treatment?
1) Toe-touch weightbearing

2) Open reduction internal fixation with a cable plate

3) Revision of the femur with a long, cementless stem

4) Revision of the femur with a long, cemented stem

5) Girdlestone resection arthroplasty

The radiograph demonstrates a periprosthetic femur fracture extending to the tip of the stem. The long spiral fracture is consistent with a loose implant. The bone stock is sufficient. Therefore, this fracture pattern would classify as a B2 using the Vancouver classification system. The Vancouver classification for periprosthetic femoral fractures is simple yet incorporates all the pertinent factors such a location, stem fixation, and bone stock. Type A is a trochanteric fracture- lesser or greater. These can be treated non-operatively usually and ORIF if symptomatic. Type B fractures are around or just below the stem and are subdivided into three types. Type B1 is a fracture with a well fixed stem.
The treatment is cable plating or allograft struts or a combination of the two. Type B2 is a fracture with a loose stem with good bone stock. The treatment is a cementless porous coated long stem atleast two diameter length past the
fracture site. Type B3 is a fracture with a loose stem and comminution. For younger patients, use cementless porous coated long stems with allograft struts. For older patients, consider a tumor prosthesis. Cement fixation is sometimes necessary Type C is a fracture well below the stem tip. These can be treated independently of the prosthesis.
Springer et al showed optimal outcomes with revision involving long extensively-coated femoral stems for Vancouver B fractures.
Masri et al review the classification and treatment of periprosthetic femur fractures.

A 67 year-old woman sustained an ACL tear while playing basketball when she was 35 years-old. She has noted progressive leg deformity and episodes of giving way, and now has pain preventing activity. Non-operative management has failed to provide relief. Treatment should consist of?
1) Opening wedge high tibial osteotomy with autograft

2) Closing wedge proximal tibial osteotomy

3) Medial interpositional arthroplasty

4) Medial unicompartmental knee arthroplasty

5) Total knee arthroplasty

The radiograph seen in Figure A reveals varus alignment of the knee, with medial tibial deficiency; from this X-ray the patient appears to have unicompartmental arthritis. Treatment options for unicompartmental arthritis include high tibial osteotomy, interpositional arthroplasty, unicondylar knee replacement and total knee replacement. Interpositional arthroplasty became popular in the 1950’s when early outcomes analysis seemed to indicate good results; long term follow up in one study found 0/12 excellent results, with all patients requiring conversion to TKA. This procedure is no longer recommended due to the poor long term outcomes.
While an osteotomy is still used for young and active patients, unicompartmental or total knee arthroplasty have largely replaced this treatment in older patients. Advantages of UKA and TKA include more predictable relief of pain, quicker recovery, and better long-term results. Criteria for UKA include limited unicompartmental disease, no more than a fixed 10 degrees of varus or 5 degrees of valgus deformity from neutral and an intact anterior cruciate ligament with no signs of medial lateral subluxation of the femur on the tibia; this patient is therefore not a good candidate for this procedure.
Total knee arthroplasty can be used to provide predictable pain relief in a patient with unicompartmental and tricompartmental degenerative disease and varus malformation of the knee and for this patient is the best option.

A 65-year old healthy male has just undergone primary total knee arthroplasty. Which of the following is associated with use of a closed suction drain in this procedure?

1) Increased incidence of wound dehiscence

2) Increased incidence of transfusion

3) Decreased incidence of infection

4) Decreased incidence of hematoma formation requiring return to OR

5) Decreased pain scores on post-op days 1 and 2

The cited meta-analysis by Parker et al evaluated 18 studies with 3495 patients (3689 wounds) and demonstrated that closed suction drainage increases the transfusion requirements after elective hip and knee arthroplasty (relative risk, 1.43; 95% confidence interval, 1.19 to 1.72). They found no significant effect on wound hematoma, infection, or operations for wound complications.

A 75-year-old man underwent total hip arthroplasty 10 years ago. He now reports mild groin pain which has been increasing lately. What is the most likely explanation for the finding in Figure A indicated with the arrows?
1) Osteosarcoma

2) Galvanic corrosion of the modular components

3) Polyethlene wear particles tracking through the effective joint space

4) Joint sepsis

5) Occult fracture

Osteolysis of the pelvis is a common complication associated with total hip arthroplasty. Osteolysis affects sockets with and without cement, and has been attributed to the biologic reaction to wear debris. With well-fixed cementless sockets, an expansile pattern of osteolysis is usually seen.
The radiographic appearance has a radiolucent area that starts at the implant-bone interface and expands into the cancellous bone away from the implant.
This pattern of osteolysis can be explained with the concept of effective joint space. This concept states that joint fluid and wear particles will flow according to pressure gradients and follow the path of least resistance.
The Level 5 review article by Chiang discusses osteolysis in further depth.

All of the following are risk factors for post-operative total knee arthroplasty periprosthetic supracondylar femur fractures EXCEPT:

1) Rheumatoid arthritis

2) Parkinson's disease

3) Chronic steroid therapy

4) Revision knee arthroplasty

5) Male gender

Rheumatoid arthritis, Parkinson's disease, chronic steroid therapy, osteopenia, and female gender have all been found to be risk factors for postoperative periprosthetic supracondylar femur fractures. Male gender has not been found to be a risk factor.
Su et al discuss risk factors for supracondylar periprosthetic femoral fractures which include rheumatoid arthritis, neurologic disorders such as Parkinson's disease, chronic steroid therapy, and revision knee arthroplasty. Analysis of the Mayo Clinic joint registry by Berry found that females are at increased risk of postoperative periprosthetic fracture, likely due to the increased incidence of osteoporosis. There is controversy regarding anterior cortical notching (Illustration A) and increased risk for periprosthetic fracture.
Lesh et al performed a biomechanical study on the consequences of anterior femoral notching. Using cadaveric matched femora with and without full thickness anterior cortex defects above TKA implants, they found that notching decreased both bending and torsional strength in the supracondylar region of the femur. They also found that fracture orientation differed between the two groups following the application of a bending load.
Ritter et al in a series of 670 total knee arthroplasties, of which 27% had notching (
A 64-year-old woman with osteoarthritis underwent bilateral total knee replacement 3 years ago. Current radiographs are shown in Figure A. She reports a 3-month history of bilateral knee pain while at rest and increasing swelling in the knees. Her ESR and CRP are elevated and bilateral knee aspiration cultures reveal Staphylococcus aureus. What is the most likely outcome if the patient undergoes simultaneous, bilateral knee resection arthroplasty with cement spacer and a course of intravenous antibiotics?
1) Prosthesis reimplantation with need for multiple surgical debridements at 2-year follow-up

2) 20% risk of above knee amputation

3) Retention of antibiotic cement spacer and low chance of successful prosthesis reimplantation at 2-year follow-up

4) 50% rate of conversion to knee fusion following resection arthroplasty

5) Successful prosthesis reimplantation at 2-year follow-up with less than 20% revision rate

This patient presents with bilateral total knee arthroplasty infection.
Wolff et al report Level 4 evidence of 18 patients followed an average of 5 years after bilateral TKA infection. Eleven patients were initially treated with attempts to salvage the original prosthesis (polyethylene l liner exchange, I&D, IV antibiotics and chronic oral suppressive antibiotics. With prosthesis retention, 9/11 (81%) developed recurrent infection at a mean of 15 months. The other 10 patients initially underwent resection arthroplasty with cement spacer and a course of IV antibiotics. Seven of the 10 (70%) underwent reimplantation at a mean of 3 months (6 weeks to 5 months) and none of the patients required revision at mean of two years follow up. Satisfaction rates were significantly higher among this group of patients. The authors advocate the protocol of bilateral TKA resection arthroplasty with cement antibiotic spacer and course of IV antibiotics followed by prosthesis reimplantation.

During insertion of a cementless femoral stem, a nondisplaced fracture is noticed along the femoral calcar. Which of the following is the most appropriate next step in surgical management?

1) Continued insertion of the stem, cerclage wiring around the fracture site, and non-weight bearing x6 weeks

2) Continued insertion of the stem, reduction of the hip, and non-weight bearing activity restrictions following surgery

3) Removal of the stem, cerclage wiring around the fracture site, and re-insertion of a stem

4) Removal of the stem and conversion to a cemented femoral stem

5) Removal of the stem, open reduction internal fixation of the femur with planned delayed femoral stem insertion following fracture healing

Appropriate care of an intraoperative fracture during total hip arthroplasty requires removal of the stem to adequately evaluate the fracture. The fracture should then be stabilized with cerclage wiring, and a long stem should be inserted to ensure stability of the stem in the postoperative period.
Tsiridis et al review the identification, classification, and management of intraoperative and postoperative periprosthetic hip fractures. Postoperative fractures around stable components may be treated with open surgical fixation. All intra-operative fractures should be considered inherently unstable, and should be treated with a long stem that bypasses the femoral fracture as well as cerclage wiring.
Incorrect Answers:
Answer 1: If there is a fracture while inserting the final femoral stem, it should be removed, a cerclage wire should be placed, then the final stem should be inserted.
Answer 2: The fracture creates an unstable situation with the femoral stem, and this should be stabilized intraoperatively to prevent settling, continued pain, and possible instability.
Answer 4: Simple conversion to a cemented stem with a proximal fracture, without cerclage placement, will lead to a loss of hoop stresses as the fracture can continue to displace during pressurization.
Answer 5: There is no need to delay femoral implant insertion to a second stage.

A 72-year-old male presents 2 years status post fixation of an impending pathologic right femur fracture due to metastatic renal cell carcinoma. He is minimally ambulatory due to pain. Despite radiation therapy, there has been progression of the lesion with extensive cortical bone loss, which is shown in Figure A. A proximal femoral replacement arthroplasty is performed without complications, and is demonstrated in Figure B. Which of the following is true regarding this patients post-operative course?
1) Deep prosthetic infection is the most common complication

2) Mean Harris Hip score will likely not improve

3) The patient will most likely continue to be minimally ambulatory

4) Aseptic failure rate at 5 years is >50%

5) Pre-operative radiation decreases the risk of infection post-operatively

Deep prosthetic infection is the most common complication after hip arthroplasty performed for salvage of failed internal fixation after pathologic proximal femoral fracture secondary to malignancy.
Jacofsky et al reviewed the complications in 42 patients with a mean age of 63 who were treated with hip arthroplasty for salvage of failed treatment of a pathologic proximal femoral fracture. Multiple different constructs were used.
The most common complication was deep prosthetic infection, which occurred in nearly 10% of the patients studied. All infections occured in patients whom had previously received radiation. The mean Harris Hip score improved from 42 to 83 points post-operatively, and 41 of the 42 patients were ambulatory at follow-up. Implant survivorship free of revision for any reason at 5 years was 90%, and free of revision for aseptic failure or radiographic failure was 97%.
Figure A shows a lytic lesion of the proximal femur with an intramedullary implant. Figure B shows a proximal femoral replacement.

All of the following are true for a patient who underwent a metal-on-metal total hip arthroplasty (THA) EXCEPT?

1) they will have production of ionically charged wear particles

2) there is a higher cancer risk than with metal-on-polyethylene THA

3) they will have elevated levels of cobalt and chromium in the serum

4) they will have elevated levels of cobalt and chromium in the urine

5) there is a higher frictional torque than with ceramic on ceramic THA

Metal-on-metal articulations in THA are characterized by ionically charged wear particles. Elevated serum and urine concentrations of metallic elements including chromium, cobalt, and molybdenum are found in patients with metal-on-metal joint replacements as compared with controls. To date, there is no correlation between metal serum levels and cancer risk. As such, the link between metal on metal arthroplasty and an elevated cancer risk has not been supported by hard data. Finally, metal-on-metal THA has higher frictional torque than ceramic on ceramic THA.
The reference by Brockett et al is a biomechanical analysis of the friction of various hip arthroplasty components. Ceramic on ceramic was found to have the lowest coefficient of friction, followed by ceramic on metal.

A 62-year-old woman is undergoing a revision total knee arthroplasty for aseptic component loosening. The surgeon has all the trial components in place and recognizes that the soft tissues are balanced in the coronal plane, but the knee is 10 degrees from reaching full extension. He proceeds to correct the contracture by
making an additional 2mm cut off of the tibia and is successful in achieving full extension. What is the most likely effect of this additional resection?

1) Loss of full flexion

2) Flexion instability

3) Extension instability

4) Valgus instability

5) Varus instability

This patient presents with asymmetric gapping because she is tight in extension and balanced in flexion. Ries discusses that resection of the proximal tibia in this situation is a common pitfall in surgical technique as it “will resolve the flexion contracture but produce instability in flexion”. The preferred method of restoring the distal femoral joint line to achieve full extension and maintain flexion stability is to cut “more of the distal part of the femur, as this will not affect the flexion space”. Similarly, there is an asymmetric gap if full extension is achieved, but flexion is limited. The lack of full flexion can be treated with distal femoral augments and a thinner tibial insert.

A 67-year-old diabetic male presents 4 months status post right total knee arthroplasty (TKA) complaining of pain and stiffness for the last four weeks. A clinical photograph is shown in Figure A. Radiographs and a bone scan are shown in Figures B, C and D. Blood work shows an ESR of 14mm/hr (normal 0-12mm/hr) and a CRP of 2mg/L (normal 1-3mg/L). Knee aspiration yields WBC of 1000, 30% PMNs, and a negative gram stain. He finished a 14-day course of antibiotics prescribed to him by his primary care physician one week ago. Which of the following is the most appropriate next step in management?
1) Broad-spectrum, empiric oral antibiotics

2) Repeat aspiration after one week

3) Irrigation and debridement of the right knee with a polyethylene liner exchange

4) One-stage irrigation and debridement of the right knee with a component exchange

5) Two-stage component removal, antibiotic spacer placement and subsequent revision

The clinical scenario describes a patient with an equivocal presentation of a periprosthetic joint infection (PJI) and recent history of antibiotic use. As such, a repeat aspiration in one week is indicated.
The work-up of a suspected PJI after TKA includes an evaluation of radiological (x-ray +/- bone scan and PET scan) and laboratory (ESR and CRP) parameters as well as analysis of joint aspirate fluid (cell count and differential, culture, gram stain +/- PCR).
Barrack et al. evaluated the utility of routine aspiration of a symptomatic TKA before reoperation and found aspiration to have a sensitivity of 75%, specificity of 96%, and accuracy of 90%. Previous antibiotic use increased the
risk of a false negative result, and reaspiration at a later date was found to significantly improve the value of this test in such cases.
Parvizi et al. published an AAOS Clinical Practice Guideline (CPG) on the diagnosis of PJI of the hip and knee using evidence from the literature. They found sufficient evidence to make strong recommendations for the use of ESR, CRP, joint aspiration, intraoperative gram stain, frozen sections of peri-implant tissues, multiple intraoperative cultures and withholding antibiotics until after cultures have been obtained.
The Workgroup Convened by the Musculoskeletal Infection Society proposed diagnostic criteria for PJI after the evaluating the available evidence and suggested that a definite PJI exists when: (1) there is a sinus tract communicating with the prosthesis; or (2) a pathogen is isolated by culture from 2 or more separate tissue or fluid samples obtained from the affected prosthetic joint; or (3) when 4 of the following 6 criteria exist: (a) elevated serum erythrocyte sedimentation rate and serum C-reactive protein (CRP) concentration, (b) elevated synovial white blood cell count, (c) elevated synovial polymorphonuclear percentage (PMN%), (d) presence of purulence in the affected joint, (e) isolation of a microorganism in one culture of periprosthetic tissue or fluid, or (f) greater than 5 neutrophils per high-power field in 5 high-power fields observed from histologic analysis of periprosthetic tissue at ×400 magnification.
Figure A is a clinical photograph demonstrating a swollen, erythematous right knee with a well-healed incision from a previous TKA. Figure B and C are AP and lateral radiographs of the right knee with no obvious acute findings. Figure D is a bone scan demonstrating increased uptake in the post-operative knee, which is consistent with the 4 month follow-up.
Incorrect Answers:
Answer 1, 3, 4 & 5: Broad-spectrum antibiotics, I & D +/- liner exchange, one stage and two stage revision would not be appropriate at this time point as the diagnosis remains unclear.

Internal rotation of the femoral component during total knee arthroplasty can result in which of the following?

1) Increased need for lateral release

2) Decreased post-operative pain

3) Increased polyethylene thickness

4) Decreased post-operative Q angle

5) Elevation of the native joint line

Internal rotation of the femoral component during total knee arthroplasty causes increased lateral patellar subluxation forces, which effectively increases the Q angle. Femoral component rotation, in isolation, does not affect the position of the joint line or dictate the necessary polyethylene thickness.
Internal rotation of the femoral component can be a source of increased pain post-operatively. Sodha et al compared the rates and results of lateral release before and after femoral component placement. The rates of lateral release in internally rotated femoral components was 24% for varus deformities and 33% for valgus deformities. When the femoral component was externally rotated, based off the transepicondylar axis in 246 TKA's, lateral release rates of 7% in varus deformities and 29% in valgus deformities were noted.
Illustration A demonstrates internal rotation of the femoral component, and increased lateral patellar subluxation.

The schematic shown in Figure A displays a ceramic-on-ceramic total hip arthroplasty articulation with impingement. Which of the
following modifications would increase the primary arc range of motion?
1) Addition of a collar on the femoral head

2) Exchanging the ceramic liner with a hooded polyethylene liner

3) Increasing the femoral head size

4) Increasing the femoral offset

5) Increasing the acetabular anteversion

The assessment of hip stability involves four major areas: component design, component alignment, soft tissue tensioning, and soft tissue function. The primary determinant of primary arc range is the head-neck ratio, which is defined as the ratio of the femoral head diameter to the femoral neck diameter. Increasing the size of the femoral head will increase the excursion distance of the femoral head to dislocate, thus making the hip more stable.
Illustration A shows how a greater head-to-neck ratio may improve range of motion before impingement. Increasing femoral component offset increases the abductor moment arm and reduces the resulting hip joint reactive force but does not affect primary arc range of motion impingement.
The article by Yoon et al reports that ceramic-on-ceramic constructs are susceptible to osteolysis resulting from particulate debris. The histologic reaction to the smaller ceramic particles was similar as the reaction to larger particles such as polyethylene. The debris in the listed study was found to be largely from the articulation and was also thought to be secondary to a decreased head-neck ratio leading to impingement.

A patient who has previously undergone a high tibial osteotomy 10 years prior is scheduled for a total knee arthroplasty (TKA). Which of the following factors is most likely to be present and may complicate the arthroplasty?

1) Collateral ligament instability

2) Patella alta

3) Patella baja

4) Patellar tendon insufficiency

5) Severe varus deformity

TKA after a high tibial osteotomy (HTO) can be more difficult to perform than a primary knee replacement because of a shift of the proximal tibial articular surface in relation to the medullary canal, retained hardware, previous skin incisions, scar tissue, and altered patellofemoral mechanics caused by patella baja and contraction of the patella tendon. The frequency of valgus deformity is greater following HTO.
Parvizi et al reviewed 166 TKA's performed following a high tibial osteotomy. A higher rate of component loosening was observed with 8% revision at 5.9 years follow-up. Male gender, preoperative limb malalignment, young age, and collateral ligament instability were associated with higher rates of failure.
Meding et al reviewed 39 patients who had bilateral TKA performed following unilateral high tibial osteotomy. There were no differences between the two
groups including postoperative complications, range of motion, revision surgery, and patient satisfaction scores.

Osteopenia has what effect on the strength of the bone-cement interface in comparison to normal bone?

1) no effect

2) improved mechanical integrity (higher fracture resistance)

3) diminished mechanical integrity (low fracture resistance)

4) reduced depth of cement penetration into bone

5) less affected by cement pressurization

The increased porosity seen in osteopenia and osteoporosis actually helps create a stronger bone-cement interface. Graham et al studied the effects of bone porosity, trabecular orientation, cement pressure, and cement penetration depth on fracture toughness at the bone-cement interface in bovine femora. They found that improved mechanical integrity (higher fracture resistance) is correlated with increased bone porosity (worsening osteopenia) and maximum cement penetration depth. The authors also found that with increased cement pressurization, the cement penetration depth was increased and the fracture resistance was also increased. In conclusion, "a lack of porosity is associated with reduced mechanical integrity of the cemented interface and may contribute to the relatively poorer results of cement fixation in young male patients." The fracture resistance of the bone-cement interface is greatly improved when the ability of the cement to flow into the intertrabecular spaces is enhanced."

Figure A demonstrates a total knee prosthesis design. Which of the following motions is constrained in this particular design:
1) Complete anterior-posterior translation constraint only

2) Partial varus-valgus angulation constraint only

3) Partial varus-valgus angulation and partial internal-external rotation constraint

4) Complete internal-external rotation constraint only

5) Complete varus-valgus angulation and anterior-posterior translation constraint

Figure A demonstrates a non-linked, constrained total knee arthroplasty prosthesis. This drawing depicts the degree of coronal plane and rotational constraint provided by the tall, wide tibial spine in the deep femoral box. This design constrains varus-valgus (allows 2°-3°) and internal-external rotation (allows 2°). A linked, rotating-hinge prosthesis (Illustration A) constrains anterior-posterior translation in addition to varus-valgus and internal-external rotation.
The article by Scuderi reports that in revision TKA, the goal is to restore the original anatomy, restore function, and provide a stable joint. To this point of stability, it is preferable to implant the prosthesis that provides adequate stability with the least mechanical constraint possible to avoid bone-implant stresses that may cause early loosening. Therefore, it is preferable to use a posterior-stabilized (cruciate substituting) articulation (Illustration B) if the knee remains stable without constrained components.
McAuley et al suggest that more predictable results are obtained with the use of cruciate-substituting components. However, if there is functional loss of the medial collateral ligament or lateral collateral ligament, inability to balance the flexion and extension spaces, or a severe valgus deformity, then a constrained
condylar prosthesis is needed.
Rodriguez et al reports Level 4 evidence of 44 patients revised with varus-valgus constrained implants followed for an average of 5.5 years. There was a theoretical concern that the increased constraint of the prosthesis would lead to component loosening, however their series had only one femoral component and no tibial components that loosened.

A surgeon is planning to revise a left hip resurfacing component to a total hip arthroplasty. He wishes to decrease the joint reaction force of the left hip by increasing the femoral offset. Which of the following labeled measurements found in Figure A best describes femoral offset?
1) Line 1

2) Line 2

3) Line 4

4) Line 5

5) Line A

In total hip arthroplasty, the femoral component offset is measured as distance between the center of the femoral head and a line drawn down the center of the femoral shaft(Line 4 shown in Figure A). Increased femoral offset is also shown in Illustration A.
The review article by Bourne et al states that offset is relevant to soft tissue balancing around the hip and the forces generated at the hip joint.
Lateralization of the femoral shaft restores offset, reduces femoropelvic impingement, and increases abductor muscle tension leading to a decreased joint reaction force. However, increasing femoral offset may have the unwanted effect of increasing rotational torque on the stem leading to aseptic loosening and increasing trochanteric bursitis.

A 62-year-old woman presents for her 1-year follow-up after a revision right total hip arthroplasty. She has no complaints of pain and has returned to all her activities of daily living. An AP radiograph is shown in Figure A. The black arrow in the radiograph indicates she is at higher risk for which of the following?
1) Aseptic loosening

2) Aseptic lymphocytic vasculitis-associated lesions (ALVAL)

3) Dislocation

4) Third body wear

5) Catastrophic ceramic bearing failure

The radiographs reveal a constrained system by the metal ring of the constrained liner, and subsequent broken ring representing a dissociation of the liner. Ring failure is associated with increased risk of hip dislocation. The incidence of dislocation ranges from 0.5% to 10% after primary and up to 28% after revision THA. Procedures described to treat this instability include reorientation of femoral or acetabular component position, trochanteric reattachment or advancement, capsulorrhaphy, the use of an elevated acetabular liner, conversion to a bipolar prosthesis, lengthening of the femoral neck, resection arthroplasty, or the use of a constrained acetabular component.
In the Level 4 study by Shapiro et al, 85 constrained THAs were implanted during revision THA for chronic instability. There was a 2.4% dislocation rate in this cohort and both of these were secondary to constrained liner dissociation. Illustration A shows a radiograph of a constrained hip dislocation secondary to
fracture of the constraining ring on the neck of the liner. An example of a broken constraining ring is shown in Illustration B.

Which of the following characteristics of stromelysin is incorrect?

1) Belongs to the family of proteolytic enzymes called metalloproteinases

2) Secreted by chondrocytes

3) Inhibited by Tissue Inhibitor of Metalloproteinase

4) Inhibited by plasmin

5) Degrades cartilage and is thought to play a role in degenerative joint disease

Stromelysin is not inhibited by plasmin.
Metalloproteinases (MMPs) are a family of proteolytic enzymes which utilizes a metal during the catalytic process. Stromelysin and plasmin are two examples of metalloproteinases, both secreted by chondrocytes, which have degradative action against cartilage. It is believed that these metalloproteinases play a role in articular degeneration and degenerative joint disease. Tissue inhibitor of metalloproteinase inhibits the degradative action of stromelysin. Tissue inhibitor of metalloproteinase (TIMPs) counteract the proteolytic enzymes produced by chondrocytes.
Tetlow et al performed an experiment on the superficial zone of cartilage in in osteoarthritis specimens. They found cells that immunostain for IL-1beta, TNFalpha, and 6 different MMP's which support the concept that cytokine-MMP associations reflect a modified chondrocyte phenotype and an intrinsic process of cartilage degradation in OA.

What preoperative knee deformity puts a patient at most risk for a postoperative peroneal nerve palsy after total knee arthroplasty?

1) Valgus deformity only

2) Valgus and flexion contracture

3) Varus and flexion contracture

4) Varus deformity only

5) Flexion contracture only

Conditions that have been associated with an increased prevalence of peroneal nerve injury include a significant fixed valgus deformity and flexion contracture. Immediate treatment of a peroneal nerve palsy post-operatively includes dressing removal and flexion of the knee 20-30 degrees.
Ayers et al report a 0.58% cumulative prevalence of peroneal nerve palsy
after TKA in their review article. They state that possible mechanisms of nerve injury include traction during correction of a valgus deformity, ischemia when stretching of the surrounding soft tissue causing occlusion of small vessels, and compression by a tight dressing or splint.
In a more recent review article, Nercessian et al report a peroneal nerve palsy incidence of 0.3-1.3% after primary total knee arthroplasty. Their reviewed studies reported a preoperative valgus deformity of 18-23.3 degrees, and flexion deformity of 15.5-22 degrees as being risk factors for peroneal nerve palsy after TKA.

Osteolysis occurs because there is a histiocytic response by macrophages to wear debris. What size particles are implicated in osteolysis?

1) less than 1 micron (submicron)

2) approximately 10 microns

3) approximately 100 microns

4) approximately 1000 microns

5) approximately 5000 microns

Osteolysis is the histiocytic response by macrophages to wear debris particles, which are often less than 1 micron in size.
Osteolysis is a particle-induced biological process occurring at the bone-metal or bone-cement interface around total joints resulting in rapidly expanding focal lesions that may or may not cause loosening. Its slower counterpart, aseptic loosening, involves the identical biological process. Wear particles generated within the joint space are phagocytosed and stored within cells in the joint capsule. Sub-micron particles are retained within macrophages and are implicated in osteolysis.
Campbell et al. described an isolation method to recover ultra-high-molecular-weight polyethylene (UHMWPE) particles from tissues around failed total hip replacements. This process yielded particles that had rounded or elongated shapes. Additionally, the majority of particles isolated were reported to be submicron in size.
Mckellop reviews four topics in wear including Modes, Mechanisms, Damage and Debris. Four Modes that creates debris are described. Wear Mode 1 occurs
when the two bearing surfaces are articulating against each other in the manner intended by the implant designer. Mode 2 occurs when a bearing surface articulates against a non-bearing surface. Mode 3 occurs when third-body abrasive particles have become entrapped between the two bearing surfaces, and Mode 4 occurs when two non-bearing surfaces are wearing against each other.
Incorrect Answers:
As reported by Campbell et al. the majority of particles recovered from prosthetic joints with osteolysis were submicron in size. Answer choices 2, 3, & 4 contain values greater than a micron and are therefore incorrect.

A 62-year-old female underwent a primary total knee arthroplasty of the left knee 10 days ago. She presents to clinic with skin necrosis of the midline incision. There is no deep infection present upon aspiration of the knee joint. She undergoes superficial irrigation and debridement and is left with exposed patellar tendon as shown in Figure A. What is the most appropriate next step in management?
1) Split thickness skin grafting

2) Twice daily wet-to-dry dressing changes with Dakin's solution until healing by secondary intention

3) Latissimus dorsi free flap transfer

4) Vacuum-assisted closure device until healing by secondary intention

5) Medial gastrocnemius muscle flap transfer and skin grafting

Medial gastrocnemius muscle flap transfer and skin grafting is the most appropriate choice of the options listed (postoperative image shown in Illustration A).
Level 4 evidence by Ries describes 9 patients sustained skin necrosis after total knee arthroplasty. Seven of these cases were over the patella tendon or tibial tubercle, of whom 6 were treated with medial gastrocnemius flap coverage. Successful wound healing and salvage of the TKA was achieved in all cases. Ries concluded that necrosis of the proximal wound including the area over the patella can be treated by local wound care and skin grafting.
However, skin necrosis over the tibial tubercle or patellar tendon requires muscle flap coverage to prevent extensor mechanism disruption and deep infection.

A 58-year-old man has significant pain and stiffness after undergoing right total knee arthoplasty 6 months ago. A current radiograph and bone scan are shown in Figures A and B. Labs show an ESR of 45mm/hr (normal 0-20) and a CRP of 13.5 mg/l(normal
1) Two-stage component removal, antibiotic spacer placement and subsequent revision

2) Observation with repeat ESR and CRP in one week

3) Surgical debridement and polyethylene exchange only

4) Repeat aspiration and culture

5) One-stage irrigation and debridement with exchange of all components

The clinical scenario describes a patient with an equivocal presentation of an infected total knee. The radiographs are normal and the bone scan shows uptake as would be expected 6 months out. A repeat aspiration is indicated in cases of equivocal laboratory aspiration data.
Mason et al in 2003 reviewed 440 revision TKA's of which 86 had preoperative aspirations. The aspirations yield 55 aseptic failures and 31 septic failures. The mean WBC of the aseptic group was 645 cells/mm(3) compared to 25,951 cells/mm(3) for the septic group (P=1100 cells/mm3 and PMN > 64% are suggestive of infection. When both tests were below these respective values, the negative predictive value was 98.2%.

Figures A and B are pre-operative and intra-operative radiographs of a 67-year-old male that has undergone a left total hip arthroplasty under general anesthesia. The patient had no motor deficits preoperatively. During the operation, the trial acetabular and femoral components were positioned and reduced with no complication. Intraoperative leg lengths were equal. Before implanting the real components, the surgeon and anaesthesiologist performed a wake up test, which revealed that the patient was unable to dorsiflex the left foot. What would be the most appropriate next step in the management of this patient?
1) Urgent electromyogram and nerve conduction study

2) Continue with sized trial components and observe the motor function in surgical recovery area

3) Remove all implants and insertion of cement spacer

4) Perform a shortening subtrochanteric osteotomy

5) Urgent neurology consult

This patient has undergone a left THA with significant leg lengthening. The biggest concern is stretch to the sciatic nerve. The most appropriate step at this stage would be to perform a subtrochanteric osteotomy to decrease leg length and sciatic nerve stretch.
Patients with DDH that have undergone a large limb-lengthening procedure are at a greater risk due to the significant stretch of the sciatic nerve. Intraoperative procedures that have been shown to prevent this outcome include good pre-operative planning, limb lengthening
A 45-year-old woman is scheduled to undergo a TKA. Which of the following implant designs theoretically reduces poylethylene wear and reduces bone-implant-interface stress?

1) Mobile-bearing TKA

2) Posterior stabilized fixed bearing TKA

3) Cruciate retaining fixed bearing TKA

4) Constrained TKA

5) Mobile-bearing hinged TKA

Total knee arthroplasties continue to be performed in patients who are younger and more active. As a result of this trend, better wear performance is imperative for long-term durability. Research continues to be done to determine optimal wear characteristics of different polyethylene and metal surfaces. Mobile-bearing knee systems are distinguished from conventional, fixed-bearing systems in that they allow dual-surface articulation between an ultra-high molecular weight polyethylene insert and metallic femoral and tibial tray components. This results in increased sagittal femorotibial conformity of most mobile-bearing implants, which reduces polyethylene shear stresses and should lessen polyethylene wear rates. By allowing more contact area, the surface and subsurface stresses in the poly bearing are significantly reduced (recall that pressure = force / area).
The ICL by Callaghan et al review the early findings of studies of fixed versus mobile bearing implants. Research is progressing as long term data continues to be collected and analyzed. Despite theoretical advantages, there has been no documented improvement in survivorship between mobile and fixed bearing TKA's in short and intermediate term studies.

Which of the following intra-operative techniques during total knee arthroplasty (TKA) decreases the need for lateral retinacular release?

1) Internal rotation of femoral component

2) External rotation of femoral component

3) Internal rotation of tibial component

4) Lateralization of patellar component

5) Insertion of a posterior cruciate retaining device

The only answer choice above that decreases the need for a lateral release during TKA is external rotation of the femoral component. Internal rotation of the femoral component increases lateral subluxation forces on the patella, and will increase the need for a lateral release.
Akagi et al looked at the relationship of femoral component rotation on lateral releases on 44 consecutive patients undergoing TKA. Twenty-two patients had femoral component set parallel to the posterior condylar axis, while twenty-two patients had femoral components set at 3-5 degrees of external rotation to the posterior condylar axis. Only 6% of patients in the externally rotated group required a lateral release, vs 33% of the neutrally aligned group.
Parker et al showed that extensor mechanism failure is the most common reason for revision TKA. They discuss the morbidity of patellar tracking which can be caused by either internal rotation of the femoral or tibial component. Furthermore, they recommend intra-operative assessment of patellar tracking with both trial and final implants. If maltracking is present in the presence of an inflated thigh tourniquet, they recommend tourniquet deflation before lateral release as this can alter patellar maltracking. A lateral release should only be considered if lateral tilt or maltracking continues in the presence of properly aligned femoral and tibial components.

When placing acetabular screws to supplement cementless acetabular fixation in total hip arthroplasty, placing screws in which zone poses the highest risk to damaging the external iliac vasculature?

1) anterior-inferior zone

2) anterior-superior zone

3) posterior-inferior zone

4) posterior-superior zone

5) oblique zone

The acetabulum is divided into four quadrants with two bisecting lines. One from the ASIS to center of acetabular socket and the second is perpendicular to it. This is a source of repeat questions concerning the danger/safe zones of various quadrants for placement of acetabular screws. anterosuperior quadrant may injure the external iliac artery and vein. The anteroinferior quadrant may injure the obturator artery, nerve, or vein. The posterosuperior quadrant may injure the sciatic nerve, superior gluteal nerve and vessels and is considered the "safe zone". Posteroinferior quadrant may injure the inferior gluteal, internal pudendal structures. In general, posterior quadrants are safe except if long screws are placed posteroinferiorly. See illustration A. Wasielewski et al conclude "quadrant system provides the surgeon with a simple intraoperative guide to the safe transacetabular placement of screws during primary and revision acetabular arthroplasty."

Which of the following factors MOST places the knee at risk of patellar maltracking in total knee arthroplasty?

1) Thickness of patellar resection

2) Cruciate retaining component

3) Medial placement of patellar component

4) Preoperative patellar tilt

5) Lateral placement of patellar component

Level 4 evidence by Kawano et al found that lateral patellar component position has been shown to directly correlate with lateral subluxation and maltracking. The study also found that there was no significant influence of the thickness of the patellar resection and preoperative patellar tilt on postoperative patellar tracking.
Avoiding implantation of the patellar component in a lateral position is paramount to tracking. Lateral positioning of the patellar component is shown in Illustration A.
An ideal percentage for patella component placement was calculated as 40-45% with the following equation: Distance of medial resected edge to central peg/length of patellar resection surface *100.

During a primary total knee arthroplasty, trial of components demonstrates a knee that is balanced in flexion and loose in extension. Which of the following will balance the flexion and extension gap?

1) Distal femur resection only

2) Distal femur augmentation and use of the same size polyethylene

3) Downsize femoral component and use a thinner polyethylene insert

4) Proximal tibia resection only

5) Distal femur augmentation and thicker polyethylene insert

The goal in sagittal balancing of TKA is to obtain a gap that is equal in flexion and extension. General principles to remember: 1. Changing the distal femur only affects extension, 2. Changing the femoral component size only affects flexion, and 3. Changing the proximal tibia/polyethylene insert affects both extension and flexion. In the above scenario, distal femoral augmentation will correct the "looseness in extension" without changing the "balanced flexion".
The above principles are reviewed by Ries et al along with soft tissue balancing principles for stability in the coronal plane.

A 69-year-old female 16 years status post total knee arthroplasty complains of knee pain. A radiograph is provided in Figure A. Which of the following is true regarding the pathogenesis of the bony abnormality seen in the distal femur?
1) It is related to the toughness of the polyethylene liner

2) It is more likely to occur with highly cross-linked polyethylene compared to conventional polyethylene

3) It is caused by macrophage activation by polyethylene particles

4) It is most frequently caused by infection

5) It occurs more frequently in patients taking immunosuppressive medications.

The radiograph demonstrates polyethylene wear and osteolysis around the femoral component of a total knee replacement. Osteolysis is caused by macrophage activation from polyethylene particles. Ingham et al reviews the pathologic role of macrophages in osteolysis. Answer #1 is incorrect because toughness of the polyethylene is not related to wear rate, but does affect its overall mechanical strength. Answer #2 is incorrect because highly cross-
linked polyethylene liners have lower wear rates compared to conventional polyethylene. The listed reference by Huang concludes that there is an increased rate of osteolysis in mobile bearing TKA. This is a contradictory finding as mobile-bearing designs were created to decrease the stress and subsequent wear of the polyethylene

A 41-year-old male has steroid-induced avascular necrosis of the hip and decides to undergo metal on polyethylene total hip arthroplasty. His 80-year-old, sedentary father had a total hip replacement 5 years ago. With comparison to his father, the patient should be informed of the following risk?

1) Increased risk of sciatic nerve palsy

2) Increased longevity of prothesis

3) Increased risk for polyethylene wear and osteolysis

4) Reduced range of motion

5) Lower likelihood of revision surgery

A younger, active patient will sustain more polyethylene wear and osteolysis due to greater activity levels and more years of use.
Kim et al prospectively studied 98 consecutive patients with osteonecrosis of the femoral head with an average follow-up was 9.3 years. Although there was no aseptic loosening of the components, they reported a high rate of linear wear of the polyethylene liner and a high rate of osteolysis in these high-risk young patients (16% in cemented femoral stems, 24% in uncemented stems).

In evaluating methods of polyetheylene sterilization for hip arthroplasty, gamma-irradiation in air compared to irradiation in an inert substance results in which of the following?

1) No difference in regards to outcome

2) Higher rate of cross-linking when irradiated in air

3) Lower rate of oxidation when irradiated in air

4) Accelerated wear and failure when irradiated in air

5) Better wear resistance and longevity when irradiated in air

The standard of care is irradiation of polyethylene (PE) in an inert gas (e.g. argon, nitrogen or vacuum packaging). Irradiation of PE in air (i.e. oxygen present) results in oxidized PE while irradiation in the absence of oxygen results in greater cross-linking.
The quoted studies by McKellop et al and Sychtez et al both demonstrate that irradiation in air results in early PE delamination and cracking and accelerated failure due to increased oxidation.

A 67-year-old man who underwent total hip arthroplasty (THA) 4 years ago fell on to his right hip. His pre-injury right hip film is seen in Figure A while films of his current injury are seen in Figures B and C. Prior to the fall he had no thigh or hip pain. His ESR and CRP are within normal limits. During intraoperative assessment, the acetabular and femoral stems are found to be well fixed. What is the next best course of action?
1) Revision of the acetabular component and ORIF of the femur with locking plates and cerclage wires

2) Revison of the femoral component, bypassing the fracture by two cortical diameters

3) Revision of the femoral component with impaction grafting and cerclage wires

4) Revision to a cemented component, bypassing the fracture by two cortical diameters

5) ORIF of the femur with locking plates and cerclage wires

This patient has a periprosthetic hip fracture at the level of the stem with a stable prosthesis, indicated open reduction and internal fixation as the treatment of choice.
The Vancouver Classification can be helpful in clinical decision-making regarding fixation versus revision of periprosthetic hip fractures of the proximal femur. A stable implant, by nature, does not need to be revised in the setting of adequate bone stock for fixation, but the ultimate test of stability should be in the operating room. Many fixation strategies are appropriate, but many implants include locking plate fixation for concerns of stress-shielded bone around the implant as well as use of unicortical fixation at the level of the stem.
Pike et al review the current trends in treating B1 fractures including locking plates with strut allografts, minimally invasive plate osteosynthesis (MIPO) and locking plates spanning femoral THA and TKA stems in selected patients. The authors conclude that no studies currently provide evidence establishing one
technique over the other and recommend treatment on a case by case basis.
Illustration A shows a possible fixation construct for this patient's fracture. The Vancouver Classification is seen in Illustration B and Illustration C represents an algorithm for treatment options.
Incorrect Answers:
1-4: All other answer choice include revising the implants, which is unnecessary based on this question stem.

While performing a cementless total hip arthroplasty in a healthy 68-year-old female, the surgeon notes an audible change while impacting the final broach. The broach is removed and a 1cm longitudinal crack originating at the calcar is visualized. Bone stock is otherwise preserved. What is the next best step in management?

1) Insert standard press-fit stem, weight bearing as tolerated postoperatively

2) Apply cerclage wire, insert standard press-fit stem, weight bearing as tolerated postoperatively

3) Insert long porous-coated stem, touch down weight bearing postoperatively

4) Insert long cemented stem, weight bearing as tolerated postoperatively

5) Insert long porous-coated stem, augment with cortical allograft and cerclage wires, touch down weight bearing postoperatively.

The patient has sustained an intraoperative proximal femur fracture and should be managed with placement of cerclage wire to prevent propagation of the fracture, insertion of the press-fit stem as planned, followed by weight bearing as tolerated postoperatively.
Intraoperative periprosthetic femur fractures occur in 1-18% of primary total hip arthroplasties (THA). Risk factors include the use of minimally invasive
techniques, press-fit cementless stems, revision surgeries, female sex, metabolic bone disease, Paget disease and intraoperative technical errors. Management of these fractures depends on timing of recognition (intraoperative or postoperative) and appropriate classification of the fracture (Vancouver classification for intraoperative fractures; Illustration A), which is dictated by fracture location, bone quality and implant stability. fMinimally displaced fractures at the calcar (Type A2) occur most often during broaching and are managed with removal of the broach, application of a cerclage wire around the fracture followed by insertion of the implant. Weight bearing does not need to be restricted postoperatively, as these minimally displaced calcar fractures are stable following cerclage wiring and implant placement. If implant stability is compromised or bone quality is poor (Type A3), a long diaphyseal stem may be used to bypass the defect. Minimally displaced fractures at the implant tip discovered immediately postoperatively may be managed with touch down weight bearing alone.
Berry reviewed management of perioperative fractures during THA. Minor cracks can be managed intraoperatively with cerclage fixation. Fractures noted postoperatively that do not affect implant stability or femoral integrity may be successfully managed with limited weight bearing and observation. Unstable implants or loss of femoral integrity require fracture fixation with either cerclage, strut grafts, plates or conversion to a long-stem implant.
Zhao et al investigated risk factors for intraoperative periprosthetic femoral fractures during cementless THA. A Corail stem (compared to Synergy), the anterolateral approach (compared to posterolateral), advanced age and a low Metaphyseal-Diaphyseal Index score (MDI score; Illustration B) were associated with increased risk of fracture. The MDI score was 25.89 (+/-8.11) in the fracture group versus 32.94 (+/-14.22) in the non-fracture group (p = 0.016). All fractures were treated with cerclage wire application and cementless implant insertion, followed by protected weight bearing postoperatively for 6 weeks, with no revisions required.
Illustration A depicts the Vancouver classification for perioperative periprosthetic femur fractures. Type A involves the proximal metaphysis [labelled A-C], type B involves the diaphysis [D-F]and type C fractures are distal to the stem tip and not amenable to insertion of the longest revision stem [G]. Each type is further sub-classified into type I if there is only a cortical perforation, type 2 is there is a nondisplaced crack and type 3 is there is a displaced unstable fracture pattern. Illustration B is an image from Zhao et al demonstrating radiographic measurements. The MDI is calculated by (D/F) / (G1+G2) where D = canal width 20mm above the mid-lesser trochanter line, F
= canal width 20mm below the mid-lesser trochanter line, G1 and G2 = two
cortical thicknesses at the same level as line F.
Incorrect Answers:
Answer 1: A cerclage wire should be placed prior to insertion of the stem, to prevent fracture propagation, loss of metaphyseal fit and ultimately stem subsidence.
Answer 3: Long porous-coated press-fit stems are usually reserved for periprosthetic fractures with extensive proximal bone loss (type A3) in which metaphyseal fixation is not possible, and therefore is not the best choice for this patient.
Answer 4: A long cemented stem is unnecessary for this periprosthetic fracture pattern. However, if a standard cemented stem is chosen, a cerclage wire should first be applied to reduce the fracture and prevent cement from entering the fracture site and potentially causing a nonunion.
Answer 5: Augmentation with cortical allograft is reserved for unstable periprosthetic fractures with diaphyseal bone loss (type B3) and therefore is not appropriate for this patient.

During revision total hip arthroplasty (THA), adjunctive motor-evoked potentials (MEPs) and electromyography (EMG) are utilized to monitor the sciatic and peroneal nerves. During the procedure, a conduction abnormality arises in the sciatic nerve. Which of the following actions would decrease tension on the sciatic nerve?

1) Provide traction to the leg

2) Pulsatile irrigation in the wound to remove blood clots

3) Flex the hip

4) Extend the hip

5) Extend the knee

The only answer choice that would decrease tension on the sciatic nerve is hip extension.
Satcher et al used motor-evoked potentials (MEPs) and electromyography (EMG) monitoring during 27 consecutive total hip revision cases to identify intraoperative events that caused conduction abnormalities of the sciatic and peroneal nerves. Leg positioning was the most commonly associated factor that increased sciatic nerve pressure, causing changes in monitored parameters in 4 patients. The position that caused the most conduction abnormality was hip flexion during posterior acetabular retraction in these patients.
Incorrect Answers:
1,2,3,5: During hip flexion, the nerve can impinge on the acetabular retractor. Providing traction to the leg, pulsatile irrigation, hip flexion, and knee extension would all increase sciatic nerve pressure.

In animal models, which of the following is true when comparing hydroxyapatite(HA)-coated femoral stems to identical non-HA porous-coated stems after implantation?

1) Grit-blasted stems have decreased rates of loosening

2) Hydroxyapatite-coated stems have shorter time to biologic fixation

3) Harris hip scores are higher after porous-coated stem insertion

4) Transient thigh pain is increased after hydroxyapatite-coated stem insertion

5) Porous-coated stems show increased rates of calcar atrophy

Hydroxyapatite-coated femoral stems have shown shorter times to biologic fixation in animal models, however clinical studies have yet to support their superiority to other stem designs.
Eckardt et al evaluated the influence of a proximal hydroxyapatite coating in comparison with a grit-blasted titanium surface of an anatomic hip stem in a canine model. Radiographically, animals with uncoated prostheses showed characteristic signs of loosening more frequently. Histomorphometrically, an average of 65% of the surface of HA-coated implants had bone contact, but this was present on only 14.7% of the surface of grit-blasted prostheses.
Kim et al followed 50 patients who underwent simultaneous bilateral hip arthroplasty in which a a proximally porous-coated titanium stem with hydroxyapatite coating was implanted on one side, and a proximally porous-coated titanium stem without hydroxyapatite coating was implanted on the other side. At a mean follow-up of 6.6 years, there was no difference in the rate of thigh pain, Harris hip score, or severity of calcar atrophy.
More recently, Camazzola et al performed a prospective randomized trial comparing hydroxyapatite-coated and non-hydroxyapatite-coated femoral total hip arthroplasty components in 61 patients. At 13 year follow-up, All femoral stems were well fixed on x-ray with no evidence of loosening. There was no statistically significant difference in the revision rates or in the Harris hip score between the two groups, and all femoral stems were well fixed radiographically. They concluded that there is no clinical advantage to the use of a hydroxyapatite coating on the femoral component for primary total hip arthroplasty.

A 60-year-old male tennis player undergoes a unicompartmental knee arthroplasty (UKA) shown in Figures A and B. Which of the following statements regarding this procedure is true?
1) Compared to total knee arthroplasty (TKA), UKA more closely approximates native knee kinematics

2) Patients undergoing a UKA and TKA have equivalent blood loss and pain
medication requirements

3) Compared to their TKA counterparts, UKA patients have a slower return to function

4) There is no difference in range of motion at short or long term follow-up when compared with TKA

5) Postoperative hospital stay is equivalent for UKA and TKA patients

Figures A and B depict radiographs of a unicompartmental knee arthroplasty (UKA). UKA kinematics have been shown to most closely approximate native knee kinematics.
In an in vitro cadaver study, Patil et al found that TKA significantly changed knee kinematics while the unicompartmental replacement preserved normal knee kinematics.
Fisher et al performed a retrospective study comparing the short-term outcomes of small-incision unicompartmental knee arthroplasty (UKA) with standard total knee arthroplasty (TKA) in 91 consecutive patients older than 70 years. They found: 1) Blood loss was significantly more for the TKA group, as was the need for blood transfusion. 2) Patients with unicompartmental replacements had a much quicker return of function and discontinuation of pain medication. 3) While knee scores and ROM were similar preoperatively, both were better in the unicompartmental group at each postoperative time interval. 4) Narcotic use and length of hospital stay were also significantly less for the unicompartmental group. Therefore answers 2,3,4 and 5 are false.

With regard to unicompartmental knee arthroplasty, all of the following are true EXCEPT:

1) Females have a higher revision rate

2) BMI greater than 32 is not a risk factor for early implant failure

3) Presence of osteopenia contributes to premature implant failure

4) Lateral compartment arthroplasties have higher failure rates than medial compartment arthroplasties

5) Progressive arthritis within the remaining compartments of the knee is low 5 years post-operatively

Lateral compartment arthroplasties have not been shown to have higher failure rates than medial compartment arthroplasties.
Heck et al determined survivorship and risk factors for failure in their study of 294 UKA's with an average follow-up of 6 years. No statistically significant difference in the need for revision was demonstrated between those knees in which a medial as compared with a lateral compartmental arthroplasty had been performed. Female gender had a RR of revision of 1.7 compared to men. They also found that the average patient requiring revision had a BMI of 32.6 kg/m2, and an association between obesity (wt >81kg) and revision was statistically significant. However more recent data, summarized below, has called this particular finding into question.
Pandit et al sought to determine whether potential and previously described contraindications to UKA should apply to patients with a mobile-bearing UKR. With regards to BMI, they found no significant clinical or functional outcome difference, failure rate or survival between 551 UKRs performed in ideal weight patients (44-82kg) compared to non-ideal (82-185kg).
Weale et al evaluated the radiographic changes in 50 UKA's at 5 years postop. They found no correlation between the post-op tibiofemoral angle and the extent of recurrent varus recorded at five years, and stated that changes in alignment may be indicative of minor polyethylene wear or of subsidence of the tibial component. They also found that the incidence of progressive osteoarthritis within the knee was very low after UKA.

Which of the following factors is most likely to increase the risk of hip dislocation after a total hip arthroplasty (THA)?

1) Large head-to-neck ratio

2) Use of a skirted femoral head

3) Femoral component in 15 degrees of anteversion

4) Acetabular cup in 15 degrees of anteversion

5) Acetabular cup in 50 degrees of abduction

The use of a skirted femoral head actually decreases the head to neck ratio as seen in illustration A, and leads to increased risk of hip impingement and dislocation after THAs. Illustration B shows an example of a smaller head-to-neck ratio causing decreased hip arc of motion before impingement occurs.
Barrack looked at implant design and orientation and its role in hip impingement and dislocations after THAs. Ways to minimize the risk of impingement and dislocation included avoiding the use of skirted heads, maximing head-to-neck ratio, and using chamfered acetabular liners whenever possible. With the use of computer modeling studies, he found that optimal femoral component anteversion is 10-20 degrees, while optimal acetabular component positioning is 10-20 degrees of anteversion and 45-55 degrees of abduction.
Illustration A shows how a skirted femoral head decreases the head to neck ratio. Illustration B shows an example of a smaller head-to-neck ratio causing decreased hip arc of motion before impingement occurs.

During total hip arthroplasty, which of the following techniques increases range of motion prior to impingement?

1) Using implants with a smaller femoral head

2) Using implants with a larger femoral head to neck ratio

3) Using a ultra high molecular weight polyethylene liner on the acetabulum

4) Decreasing femoral offset

5) Cementing the femoral stem

Using implants with a larger femoral head to neck ratio increases range of motion prior to impingement and improves stability.
The efficacy of using a larger size diameter femoral head to improve stability has been recognized since the early 1970s. With the larger head (larger head to neck ratio), the distance to travel before subluxation and dislocation is greater, and more ROM is allowed before the neck impinges on the shell wall and levers the head from the shell.
Amstutz et al. evaluated the outcomes of 140 THAs using size 36mm femoral heads or larger. Patients were divided into 3 groups: revision for dislocation, revision for reasons other than dislocation, and primary THA. Six cases required revision surgery for instability and all were found to have mal-oriented acetabular components. After revision, all the hips were stable and none required the use of a constrained acetabular liner. The authors concluded that large diameter femoral heads provide additional stability not only for patients with recurrent dislocations, but for any revision.
Sikes et al. compared 52 THA cases at high risk of dislocation to a matched cohort. The high risk patients were all treated with a large diameter metal on metal components while the matched group received the standard metal on poly. The large head group had 0 disclocations compared to 2 in the standard head size. Ultra high molecular weight polyethylene liners (answer #3) are used in almost all metal on plastic THA today and have greater resistance to wear than prior generation of liners. However, they have no effect on ROM and impingement. Decreased femoral offset (#4) would result in decreased tension in the abductors and could result in increased risk of dislocation, but has no effect on impingement of the femoral neck on the acetabular cup. Cemented (#5) versus press fit stems should have no effect on ROM and impingement.

Which of the following motions shows the greatest difference between a normal and ACL deficient knee?

1) Posterior femoral translation at 30° flexion

2) Posterior femoral translation at 60° flexion

3) Axial rotation in full extension

4) Axial rotation at 50° flexion

5) Varus angulation at 30 ° flexion

The study by Dennis et al, found a different axial rotation pattern in ACL deficient (ACL-D) knees compared to normal knees after 30° of knee flexion. Axial rotation was the same between the two groups in less than 30° of flexion. They also found normal and ACL deficient (ACL-D) knee patients demonstrated a similar pattern of posterior femoral translation during progressive knee flexion (0-120°). Additionally, the study showed increased variability in knee kinematic patterns observed in ACL-D knees as compared to the normal knees. Posterior femoral translation is substantially greater laterally than medially in both normal and ACL deficient patients, creating a medial pivot type of axial rotation pattern. With knee flexion, the normal tibia typically internally rotates relative to the femur and conversely, externally rotates with knee extension (i.e., screw home mechanism)

Figure A shows a ceramic head removed during a total hip revision. The component shows damage to the femoral head which was most likely caused by which of the following?
1) Third body debris

2) Chronic infection

3) Impingement of the femoral stem neck on the acetabular socket

4) Lift-off separation of the femoral head during hip range of motion

5) Insertion of the head on the femoral stem at time of initial surgery

Ceramic-on-ceramic articulation has been an attractive alternative to metal-on-polyethylene articulation because it exhibits low-friction, load-tolerant behavior with satisfactory wear characteristics. Stripe-wear as found in Figure A is a distinct type of impingement from the classic impingement of the femoral head on the acetabular socket found in episodes of instability (ie. lift-off separation) during gait.
Yammamoto et al in a retrieval study of 3 ceramic bearings and found significant stripe scars/wear at the rim of the alumina, but not at the weight bearing portion of the head. They concluded that stripe wear is caused by the femoral head making contact with the rim of the socket when the head undergoes lift-off separation from the socket.
Manaka et al found that the locations of the stripes were similar in retrieved and simulator ceramic heads. However, the stripes from the simulator were narrower than the short-term retrievals and much narrower than some longterm retrievals.

A 57-year-old man complains of knee pain that is exacerbated with weight bearing and ambulation. He underwent surgery on his knee 10 years ago following a motor vehicle collision. On physical exam he has medial and lateral joint line tenderness and no instability. Radiographs are provided in figures A and B. Conservative therapy with NSAID's and viscosupplementation is initiated. If he continues to develop further degenerative changes and needs arthroplasty what type of implant should be utilized?
1) Unicompartmental mobile bearing knee arthroplasty

2) Posterior cruciate retaining total knee arthroplasty

3) Posterior stabilized total knee arthroplasty

4) Constrained nonhinged total knee arthroplasty

5) Constrained hinged total knee arthroplasty

The radiographs and clinical presentation are consistent with a patient who has undergone a previous patellectomy and is now developing degenerative arthritis of the knee. Patellectomy is an indication to use a posterior stabilized implant. The PS implant will offer better femoral rollback and reduce the risk of potential anteroposterior instability that may occur with use a cruciate retaining prosthesis.
Paletta et al review a series of patients undergoing TKA following patellectomy and compared them to a series of TKA patients who did not have a previous history of patellectomy. Most importantly they showed better outcomes in patellectomy patients who had a posterior-stabilized implant placed at the time of TKA.
Incorrect Answers:
Answer 1: UKA is not suitable for a patient with medial and lateral pain nor a patient with previous patellectomy
Answer 2: Posterior cruciate retaining knee following patellectomy risks anteroposterior instability
Answer 4 & 5: Constrained knee options are not necessary for patellectomy as there is no loss of varus/valgus stability.

A 66-year-old male is undergoing a total knee arthroplasty using a fixed bearing posterior stabilized component. During intraoperative trialing of the components it is noted that the flexion gap is loose, and extension gap is appropriate. If this is not corrected, what postoperative complication is this patient most at risk of having?

1) Spin out of the polyethylene

2) Periprosthetic fracture

3) Posterior knee dislocation

4) Osteolysis

5) Patellar instability

A posteriorly stabilized knee has a post built into the polyethylene bearing that articulates with the box of the femoral component in flexion to act as a cam
mechanism. If the knee is too loose in flexion, it is possible for the femoral component to "jump the post", causing a posterior dislocation.
Clarke and Scuderi review flexion instability as a mode of failure in knee replacements. They describe how this is usually due to lack of adequate balance at the time of surgery. They also report that revision surgery is usually the only way to correct symptomatic flexion instability.

A 56-year-old gentleman presents to your office one year after undergoing total hip arthroplasty with the implant seen in Figure A. He is concerned about the potential complications given the recent media attention his implant has received. He is currently asymptomatic. Which of the following statements is accurate regarding his prosthesis and future care?
1) He should have bi-annual LFTs measured, as metal ions are metabolized by the liver.

2) His risk of developing cancer is dramatically increased.

3) There is no correlation between activity level and serum levels of metal ions.

4) His prosthesis design is safe in women of child-bearing age as the ions cannot be transmitted via pregnancy.

5) His prosthesis design puts him at an increased risk for dislocation.

There is currently much debate over metal-on-metal (MOM) hip replacements and the optimal management of these patients in the post-operative period.
While data is currently limited, it has been shown that activity level does not affect serum metal ion levels.
Heisel et al. in their article from JBJS 2005 present level II evidence where they looked at the relationship between patient activity and cobalt and chromium ion levels. They found no correlation between patient activity and serum levels of cobalt or chromium, or urine levels of chromium.
Incorrect answers:

Skin grafts are especially useful for patients with Dupuytren disease who have severe, diffuse disease and recurrences, particularly with multiple joint involvement. Although rarely required for primary cases, if disease is infiltrative and diffuse, skin grafts can be useful. Full-thickness skin grafts are preferred, providing more aesthetic and durable skin coverage while exhibiting less tendency to retract than partial-thickness grafts. Most authors have observed that recurrence is uncommon beneath a graft, although a recent article by Roush and Stern did not find that full-thickness skin grafting prevented recurrences. Grafts rarely do not “take” even though they often are placed directly over neurovascular bundles and the flexor sheath.
RECOMMENDED READINGS
19. [Hall PN, Fitzgerald A, Sterne GD, Logan AM. Skin replacement in Dupuytren's disease. J Hand Surg Br. 1997 Apr;22(2):193-7. PubMed PMID: 9149986. ](http://www.ncbi.nlm.nih.gov/pubmed/%209149986)[View Abstract at PubMed](http://www.ncbi.nlm.nih.gov/pubmed/%209149986)
20. [Heuston JT. The control of recurrent Dupuytren's contracture by skin replacement. Br J Plast Surg. 1969 Apr;22(2):152-6. PubMed PMID: 4891593. ](http://www.ncbi.nlm.nih.gov/pubmed/4891593)[View Abstract at PubMed](http://www.ncbi.nlm.nih.gov/pubmed/4891593)
21. MCCASH CR. THE OPEN PALM TECHNIQUE IN DUPUYTREN'S CONTRACTURE. Br J Plast
[Surg. 1964 Jul;17:271-80. PubMed PMID: 14191131. ](http://www.ncbi.nlm.nih.gov/pubmed/14191131)[View Abstract at PubMed](http://www.ncbi.nlm.nih.gov/pubmed/14191131)
22. [Roush TF, Stern PJ. Results following surgery for recurrent Dupuytren's disease. J Hand Surg Am. 2000 Mar;25(2):291-6. PubMed PMID: 10722821. ](http://www.ncbi.nlm.nih.gov/pubmed/10722821)[View Abstract at PubMed](http://www.ncbi.nlm.nih.gov/pubmed/10722821)

C acnes is the most common organism recovered in prosthetic shoulder infections (33%), Coagulase-negative Staphylococcus is second (21%), Methicillin-sensitive S aureus (13%), and S epidermidis (10%). MRSA accounts for 5% and Enterococcus species, 1.5%.
54

Collagen type X is produced only by hypertrophic chondrocytes during enchondral ossification (growth plate, fracture callus, heterotopic ossification) and is associated with calcification of cartilage in the deep zone of articular cartilage. Collagen type I is the predominant collagen in bone, ligament, and tendon. Collagen type II is the predominant collagen in articular cartilage. Proteoglycan aggrecan and hyaluronic acid are components of the extracellular matrix and are involved in the compressive strength characteristics of articular cartilage.
REFERENCES: Buckwalter JA, Mankin HJ: Articular cartilage: Tissue design and chondrocyte matrix interactions. Instr Course Lect 1998;47:477-486.
Poole AR, Kojima J, Yasuda T, Mwale F, Kobayasai M, Laverty S: Composition and structure of articular cartilage: A template for tissue repair. Clin Orthop 2001;391:S26-S33.

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The photograph shows the planned incision for an extensile lateral approach to the calcaneus. The lateral calcaneal artery, usually a branch of the peroneal artery, provides blood supply to the majority of the full-thickness flap of an extensile lateral approach. Other branches also contribute,including the lateral malleolar and lateral tarsal arteries, although to a lesser degree.

A chronic mallet finger results in proximal retraction of the extensor mechanism and overpull of the central slip. Isolated central slip rupture does not cause this deformity. Rupture of the flexor digitorum sublimis can cause Swan-neck deformity. MP arthroplasty is not associated with this deformity. The sequalae of dorsal proximal interphalangeal joint dislocation (e.g., volar plate laxity or deficiency) leads to Swan-neck deformity.

The elbow usually is stable after reduction in most elbow dislocations. Ross and associates reported that supervised motion begun immediately after reduction was effective in uncomplicated dislocations. The elbow will become stiff if immobilization is applied for an extended period of time. Immediate open treatment is not indicated for a simple elbow dislocation.
REFERENCES: Ross G, McDevitt ER, Chronister R, et al: Treatment of simple elbow dislocation using an immediate motion protocol. Am J Sports Med 1999;27:308-311.
O’Driscoll SW, Jupiter JB, King GJ, et al: The unstable elbow. J Bone Joint Surg Am 2000;82:724-738.

The patient has exertional heat exhaustion (EHE). In cases of exertional heat illness with elevated core body temperature, it is critical to differentiate between EHE and exertional heat stroke (EHS). Patients suffering from EHE often complain of dizziness, nausea, cramping and headache. Vital signs can show mild tachycardia and normal to low blood pressure. EHS is defined by elevated core body temperature >40°C (104°F) and organ failure. Rapid cooling is critical in the setting of EHS, but not EHE. In the setting of EHE, the patient should be placed in a cool, shaded area and given fluids. Studies suggest that the presence of carbohydrate (<8%) in combination with electrolytes mildly promotes fluid retention better than drinking water alone.

Humphreys and associates in a retrospective review of TLIF vs PLIF found fusion rates, surgical time, and length of hospital stay were similar with both procedures. The only benefits associated with TLIF were less blood loss and preservation of the paraspinal muscle sleeve. Manos and associates in a cadaver study found no difference in the volume of disk material evacuated or the area of endplate exposed in either procedure.
RECOMMENDED READINGS
[Humphreys SC, Hodges SD, Patwardhan AG, Eck JC, Murphy RB, Covington LA. Comparison of posterior and transforaminal approaches to lumbar interbody fusion. Spine (Phila Pa 1976). 2001 Mar 1;26(5):567-71. PubMed PMID: 11242386. ](http://www.ncbi.nlm.nih.gov/pubmed/11242386)[View Abstract at PubMed](http://www.ncbi.nlm.nih.gov/pubmed/11242386)
Manos R, Sukovich W, Weistroffer J: Transforaminal lumbar interbody fusion: Minimally invasive versus open disc excision and endplate preparation. Presented at the 12th International Meeting of Advanced Spine Techniques, Banff, Alberta, Canada, July 7-9, 2005.

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This girl sustained a fracture dislocation of the elbow with a severely displaced and rotated radial neck fracture. Required treatment was open reduction and internal fixation (ORIF). Less severely displaced radial neck fractures can be treated with closed reduction, percutaneous pinning, or flexible nail manipulation. In this scenario, interposed capsular tissue and rotation of the radial head were indications for ORIF. ORIF is associated with a higher risk for poor outcomes. Complications following ORIF of radial neck fractures in children include posterior interosseous neuropraxia, valgus angulation, premature closure of the radial head physis, AVN of the radial head, nonunion, and elbow stiffness. Stiffness is most common. Compartment syndrome, infection, and anterior interosseous nerve palsy are less common complications.

Four proteins that regulate osteoclast activation have been discovered:
1/. RANK binds to a receptor on osteoclast precursor cells and positively effects their final differentiation into osteoclasts.
2/. Osteoprotegerin is a soluble decoy receptor that resembles RANK and inhibits osteoclasts.
3/. Tumor necrosis factor-related activation induced cytokine (TRANC E)
4/. Osteoclast differentiation factor
Note:
C bfa1 is a transcription factor (coded by the C bfa1 gene) that is necessary and sufficient for differentiation of cells into osteoblasts and facilitates chondrocyte differentiation during enchondral bone formation.

Ankle sprains are the most common musculoskeletal injury; however, most of these sprains do not progress to chronic instability. Initial injuries are treated with RICE (rest, ice, compression, elevation), range of motion, weight bearing
as tolerated, and proprioceptive therapy. Lace-up ankle braces are most effective during the subacute period after a sprain. Structured physical therapy focused on proprioception is recommended for 6 weeks. Examination findings for ankle ligament instability are unreliable because of associated subtalar joint motion. Casting is not as effective as functional rehabilitation. Stress radiographs are recommended, but a clear pathologic range of measurements is not defined. Generalized ligament laxity can result in false-positive findings of instability; therefore, contralateral stress radiographs are often necessary for comparison. The difference in anterior drawer measurement between both ankles should not exceed 5mm. Likewise, the difference in talar tilt measurement between both ankles should be 5 or fewer degrees. Patients with mechanical symptoms, a joint effusion, or continued pain may have an intra-articular pathology such as a loose body or osteochondral lesion. Ankle instability can exist without ligamentous laxity. Symptoms of chronic instability can result from osteochondral lesions of talus, peroneal tendon pathology, loose bodies, anterior ankle impingement, and fracture nonunions. Although there is not sufficient evidence to recommend arthroscopy prior to all ligament reconstructions, arthroscopy is recommended when other pathology is suspected.
RECOMMENDED READINGS
[Colville MR. Surgical treatment of the unstable ankle. J Am Acad Orthop Surg. 1998 Nov-Dec;6(6):368-77. Review. PubMed PMID: 9826420. ](http://www.ncbi.nlm.nih.gov/pubmed/9826420)[View Abstract at PubMed](http://www.ncbi.nlm.nih.gov/pubmed/9826420)
[DiGiovanni CW, Brodsky A. Current concepts: lateral ankle instability. Foot Ankle Int. 2006 Oct;27(10):854-66. Review. PubMed PMID: 17054892. ](http://www.ncbi.nlm.nih.gov/pubmed/17054892)[View Abstract at PubMed](http://www.ncbi.nlm.nih.gov/pubmed/17054892)
[Maffulli N, Ferran NA. Management of acute and chronic ankle instability. J Am Acad Orthop Surg. 2008 Oct;16(10):608-15. Review. PubMed PMID: 18832604. ](http://www.ncbi.nlm.nih.gov/pubmed/18832604)[View Abstract at PubMed](http://www.ncbi.nlm.nih.gov/pubmed/18832604)

The radiographs reveal bilateral bone infarcts with subchondral collapse. The images are diagnostic for bone infarct. Other hematological conditions are associated with multiple bone infarcts, including sickle-cell disease, hemophilia, aplastic anemia, thalassemia, and acute lymphoblastic leukemia. Postsurgical radiation therapy is considered for Paget disease, but the radiographic appearance is not consistent with that diagnosis.
RECOMMENDED READINGS
57. [Lotke PA, Ecker ML. Osteonecrosis of the knee. J Bone Joint Surg Am. 1988 Mar;70(3):470-3. Review. PubMed PMID: 3279040.](http://www.ncbi.nlm.nih.gov/pubmed/3279040)[View Abstract at PubMed](http://www.ncbi.nlm.nih.gov/pubmed/3279040)
58. [Sorich MM, Cherian JJ, McElroy MJ, Banerjee S, Jones LC, Minniti CP, Mont MA. Osteonecrosis of the Hip in Hematologic Disease: A Review of Conditions and Treatment Options. J Long Term Eff Med Implants. 2015;25(4):253-68. PubMed PMID: 26852634.](http://www.ncbi.nlm.nih.gov/pubmed/26852634)[View Abstract at PubMed](http://www.ncbi.nlm.nih.gov/pubmed/26852634)
59. Karim AR, Cherian JJ, Jauregui JJ, Pierce T, Mont MA. Osteonecrosis of the knee: review. Ann Transl Med. 2015 Jan;3(1):6. doi: 10.3978/j.issn.2305-5839.2014.11.13. Review. PubMed PMID: 25705638.
[View Abstract at PubMed](http://www.ncbi.nlm.nih.gov/pubmed/25705638)
CLINICAL SITUATION FOR QUESTIONS 78 AND 79
Figures 78a through 78d are the radiograph, CT scans, and biopsy specimen of a 45-year-old man with a history of treatment for localized low-grade pelvic chondrosarcoma with limb salvage. He now has recurrent pain about his hip.

Of the possible
hoices, only adult-acquired flatfoot is associated with tarsal tunnel syndrome. The so-called "heel pain triad" includes adult-acquired flatfoot, plantar fasciitis, and tarsal tunnel syndrome, in which failure of the dynamic and static supports of the medial longitudinal arch increase traction on the tibial nerve.
PREFERRED RESPONSE: 1

Intra-articular hyaluronic acid is no longer recommended as an effective method of treatment for patients with symptomatic knee arthritis based on the revised AAOS clinical guidelines from 2013. The previous review from
2009 guidelines was reported as inconclusive.
Nonoperative treatment modalities whose use is supported by the literature include: activity modifications, weight loss, quadriceps strengthening, patellar taping, NSAIDs, tylenol (Now 3000mg/24hr is recommended from 4000mg/24hr), and intra-articular steroids. Treatment options that are NOT supported by the literature (or are considered inconclusive) include: intra-articular hyaluronic acid injections, lateral heel wedges for medial knee OA, glucosamine and chondroitin, needle lavage, and arthroscopy in patients with primary OA.
Illustration A shows a chart showing the rates of accuracy of intra-articular knee injections.
Incorrect Answers:

: Weight loss is considered a moderate recommendation according to the AAOS clinical guidelines.
Answer 2: Activity modification is strongly recommended according to the AAOS clinical guidelines.
Answer 3: Quadriceps strengthening is strongly recommended according to the AAOS clinical guidelines.
Answer 5: The use of intra-articular corticosteroid injections cannot be recommended for or against according to the latest AAOS clinical guidelines.

All of the following are intraoperative techniques to treat a flexion contracture in total knee arthroplasty EXCEPT:

1) Resect osteophytes

2) Release posterior capsule

3) Resect more distal femur

4) Downsize the femoral component

5) Tenotomize the hamstrings

Of the options listed, downsizing the femoral component would NOT be an intraoperative technique to treat a flexion contracture in total knee arthroplasty.
Flexion contractures (an extension gap issue) can be addressed by resecting osteophytes, resecting the posterior capsule/gastrocnemius, resecting additional distal femur, and tenotomizing the hamstrings. Downsizing the femoral component would only change the flexion gap and have no impact on a flexion contracture (an extension gap issue.) Downsizing the femoral component means decreasing the size of the implant in the anterior-posterior dimension only. There is no change in the proximal-distal dimension, and thus changing the size of the femoral implant only affects the flexion gap, and not the extension gap or a flexion contracture.
Bellemans et al. propose an algorithm to treat preoperative flexion contractures greater than 5 degrees. The steps include:
Step 1: Mediolateral ligament balancing with meticulous osteophyte removal and over resection of distal femur by 2 mm.
Step 2: Add posterior capsular release.
Step 3: Add distal femoral resection up to 4 mm. Step 4: Add hamstring tenotomy.
For flexion contractures less than 15 degrees they report steps 1 and 2 were sufficient for 100% of the cases in their study. Steps 3 and 4 were only necessary for some contractures greater than 35 degrees.
Illustration A shows how changing the femoral component size only affects the flexion gap.
Incorrect Answers
Answers 1,2, 3, and 5 are all methods to treat a flexion contractures in total knee arthroplasty.

A 64-year-old healthy female patient underwent right total hip replacement (THR) through a posterior approach 6 months ago. She has now dislocated posteriorly 3 times, each followed by closed reduction under anesthesia in the operating room. A radiograph is provided in Figure A. Treatment should include:
1) Hip spica casting

2) Revision of the femoral component to a modular stem with retention of the acetabular component

3) Revision of the acetabular component

4) Hip abduction bracing

5) Revision to a constrained liner with retention of the acetabular and femoral prostheses

The optimal acetabular component alignment is 30-50 degrees of abduction and 15-20 degrees of anteversion. This patient has a vertical acetabular component that requires revision.
Reasons for recurrent THA instability include infection, non-compliance with precautions, component malposition, impingement and inadequate soft tissue tension. Strategies that do not address the underlying cause of recurrent dislocation will not definitively treat the instability. Non-operative measures cannot account for drastic component malposition.
Figure A shows an AP pelvis after right total hip arthroplasty. The acetabular component is vertically positioned. The femoral component is in slight varus but not enough to warrant revision on its own. The version of each component cannot be definitively determined on this single film. The acetabular component has a significant amount of version that could be ante- or retroversion.
Incorrect Answers:

■
The patient's history and examination findings are consistent with a lumbar disk herniation at the L5-S1 level. Weakness of the gastrocnemius and gluteus maximus are consistent with an S1 lumbar radiculopathy. Nerve root tension signs are also consistent with a disk herniation at L5-S1, which typically affects the traversing S1 nerve root.

The arrow in Figure 2 marks the dorsal sensory branch of the ulnar nerve. Injury to this nerve results in sensory loss of the dorsal ulnar palm and the dorsal small and ring finger digits. The dorsal sensory branch of the ulnar nerve exits the main ulnar nerve at an average distance of 8.3 cm from the proximal border of the pisiform. It becomes subcutaneous on the ulnar aspect of the forearm at an average distance of 5
cm from the proximal edge of the pisiform. It then travels dorsal to the extensor carpi ulnaris tendon to innervate the dorsal ulnar hand and the dorsal ring and small digits. Injuries to this nerve can occur from open and arthroscopic procedures (such as triangular fibrocartilage complex repair) as well as from procedures requiring percutaneous pinning. Care must be taken to identify and protect this nerve to avoid the complications of numbness and possible neuroma formation. The inability to extend the small finger would be caused by an injury to the extensor tendon(s) in this area, and the inability to abduct the small finger would require an injury to the abductor digiti minimi muscle/tendon unit or the ulnar nerve motor branch, which is located on the volar aspect of the proximal palm. Clawing of the small and ring fingers would be caused by absent intrinsic function due to an injury to the ulnar motor nerve branch located on _the volar proximal palm._

A number of factors affect nerve conduction velocity; for example, increased body temperature increases nerve conduction velocity. Nerve conduction velocity is slowed by advancing age, compression, decreased blood flow, and fibrosis (from large imprecise sutures used for nerve repair). There is no _association between hand dominance and nerve conduction velocity._

The MRI scans show a distal biceps tendon avulsion with significant retraction. When addressing these injuries, a single-incision approach has been associated with an increased risk of lateral antebrachial cutaneous nerve injury. A two-incision approach has been associated with an increased risk of heterotopic ossification, second surgeries and posterior interosseous nerve injury.
34

Warfarin (Coumadin) exerts its anticoagulation effect by inhibiting the carboxylation of normal clotting factors. Warfarin is a vitamin K antagonist
that prevents the reductive metabolism of vitamin K epoxide back to its active form, hydroquinone, by inhibiting the enzymes responsible for the reaction. The vitamin K- dependent factors are II, VII, IX, X, proteins C, and S.
The reference by Hyers is a review article discussing the antithrombotic agents that have been used in the last 50 years and also discusses some of the newer ones that have since been developed.
Berry in his review discusses the risk factors, efficacy, and safety of agents used in 2003 after total hip arthroplasty.

: Enoxaparin binds to and increases the activity of antithrombin III. By activating antithrombin III, enoxaparin potentiates the inhibition of coagulation factors Xa and IIa.
Answer 3: Dalteparin is a low molecular weight heparin
Answer 4: Heparin binds to the enzyme inhibitor antithrombin III. The activated AT then inactivates thrombin and other proteases involved in blood clotting, most notably factor Xa.
Answer 5: Hirudin (the active component released by leeches), is often considered the most potent inhibitor of thrombin.

A 25-year-old healthy male is scheduled to undergo a a nine-level posterior spinal fusion for scoliosis. Administering preoperative recombinant erythropoietin would place the patient at increased risk of developing which of the following complications?

1) Acute renal failure

2) Increased bleeding time

3) Thrombotic event

4) Wound complications

5) Delayed spinal fusion

The use of recombinant erythropoietin(EPO) preoperatively for patients undergoing major elective orthopedic surgery has been associated with a higher incidence of deep vein thrombosis (DVT).
Johnson et al present a Level 5 review of recombinant eryrthropoetin (Epoetin alfa). When hypoxia in the body is detected, the kidney is stimulated to produce EPO in the renal cortical interstitial cells. EPO interacts with progenitor stem cells in the bone marrow to increase RBC production. The use of erythropoietin does decrease transfusion rates, but has no effect on renal function, bleeding times, wound complications, or bony healing.
The Level 1 study by Beris et al studied the use of recombinant human erythropoietin as an adjuvant treatment to autologous blood transfusions in elective surgery. They reported a 10% DVT rate with the 300 U/kg recombinant EPO (10%) dosage versus placebo (5% rate).

A 4-year-old female is brought by her parents in regard to a right sided limp that improves during the day and has been present for two months. She is found to have a right knee effusion and associated
soft-tissue swelling with no redness or warmth. Lab work reveals negative Rheumatoid factor, a positive low titer ANA and a normal WBC. Radiographs are normal for her age. What additional work up does she need?

1) Skeletal survey

2) MRI of the pelvis

3) Clotting factor levels

4) Ophthalmology evaluation

5) Bone scan

This patient has a history and physical findings consistent with juvenile idiopathic arthritis (JIA). This type of JIA specifically has a high association
with iridocyclitis, particularly in those with positive ANA studies (approximately
20%). Patients with JIA require an ophthalmology consultation for slit lamp examination to evaluate for anterior uveitis, with any type of pupil asymmetry requiring an immediate consultation. Eye involvement can be indolent and lead to blindness if not promptly identified. Due to early treatment of the uveitis, blindness has become a rare complication.
The Sherry article provides an overview of new treatment methods including intraarticular joint injections of methotrexate and etanercept, which have produced giant leaps in the treatment of the associated joint inflammation and resultant destruction.

A 25-year-old male sustains a transverse humeral shaft fracture and undergoes open reduction and internal fixation with rigid compression plating. What kind of bone healing would be expected with this type of fracture fixation?

1) Primary bone healing through haversian remodeling

2) Secondary healing through callus formation

3) Primary healing through callus formation

4) Endochondral ossification

5) Secondary healing through osteonal cutting cones

Fractures and osteotomies that are stabilized with rigid compression plating undergo primary bone healing, also known as haversian remodeling. Absolute stability constructs, such as a compression plate, allow for bone healing without visible callus formation.
Healing occurs via extension of clusters of osteoclasts (known as osteonal cutting cones) across the fracture site, along with osteoblasts depositing new bone and blood vessels to re-establish the haversian system.
Seconday bone healing occurs when fractures heal through callus formation. Relative stability constructs, such as an intramedullary nail, allow for some motion at the fracture site which leads to healing through a cartilage scaffold (endochondral ossification).
Illustration A demonstrates a transverse fracture stabilized with a compression plate. Illustration B shows a femoral shaft fracture that has healed through callus formation.
Incorrect Answers:
Answer 2: Secondary healing through callus formation occurs when fractures heal with some motion at the fracture site; for example intramedullary nailing of a diaphyseal femur fracture
Answer3: Primary healing is defined by the absence of visible callus
Answer 4: Endochondral ossification is bone generation or healing through a cartilage scaffold
Answer 5: Secondary healing does not occur through osteonal cutting cones as there not enough stability at the fracture site

When analysing complex geometric form and material property distributions, the structure of interest may be divided up into numerous connected subregions or elements within which approximate functions are used to represent the unknown quantity. What is the name for this technique?

1) Breakdown synthesis

2) Finite element method

3) Algebraic conclusion

4) Differential equations

5) Isogeometric analysis

To solve a problem with complex geometric form and material property distributions, the finite element approach is used to break the problem up into smaller “finite elements” with simple geometric form. Usually triangular or quadrilateral elements are used. A computer program is written to balance the forces and moments acting on each element, and match these forces and moments with those of its neighboring elements. For large structures with a large number of elements, the computer must solve thousands of algebraic equations to make sure all the forces are balanced in the interior of the body and at the surface where the forces are applied. In orthopedics, stress analysis of the cement fixation of implants to bone is frequently carried out using finite element analysis.

A load-elongation curve for a tendon is shown in Figure A. Which of the following statements accurately describes the region labeled "X"?
1) The failure region which has crimped tendon fibers

2) The linear region which has parallel oriented tendon fibers

3) The linear region which has crimped tendon fibers

4) The toe region which has parallel oriented tendon fibers

5) The toe region which has crimped tendon fibers

Region "X" in the illustration is the toe region of the load-elongation curve. This region represents the initial elongation during which a small amount of tension causes crimped, randomly arranged fibrils to become aligned parallel along the direction of loading.
Magnusson et al looked at the properties of tendon in relation to muscular activity and training. Collagen composition of tendon is organized in a very hierarchical manner along parallel bundles. Tendon collagen bundles have a more parallel orientation along the long axis than ligaments, making their toe region smaller. Illustration A shows all the regions of the load-elongation curve.

Which of the following molecules binds to the surface of hydroxyapatite crystals and prevents protein prenylation?

1) Calcitonin

2) Parathyroid Hormone

3) Raloxifene

4) Calcium

5) Alendronate

Bisphophonates accumulate in high concentration in bones due to their binding affinity to hydroxyapatite crystals.
There are two types of bisphosphonates with different mechanisms, although both classes ultimately inhibit osteoclast resorption of bone. Nitrogen containing bisphosphonates (alendronate/Fosamax, pamidronate/Aredia, risedronate/Actonel) prevent protein prenylation by inhibiting farnesyl diphosphate synthase, an enzyme in the mevalonate (cholesterol) pathway.
The non-nitrogenous bisphosphonates (etidronate/Didronel, clodronate, tiludronate) are metabolised in the cell to compounds that replace the terminal pyrophosphate moiety of ATP, forming a nonfunctional molecule that competes with adenosine triphosphate (ATP) in the cellular energy metabolism. Due to this disruption in metabolism, the osteoclast initiates apoptosis and dies, leading to an overall decrease in the breakdown of bone.

Which of the following foot radiographs is most consistent with the diagnosis of gout?
1) A

2) B

3) C

4) D

5) E

Figure B is most consistent with a diagnosis of gout.
Gout results from deposition of the monosodium urate crystal. It affects the lower limb, resulting in arthritis of the great toe (podagra). On radiographic evaluation, periarticular erosions in the setting of tophaceous formations may be seen.
Egan et al. describe the characteristic radiographic findings of gout in the foot. This includes asymmetric polyarthropathy, well-defined erosions with sclerotic margins, overhanging bony edges and tophaceous formations.
Figure B shows an AP radiograph of a foot affected by gout. Note the periarticular erosions, soft tissue calcifications (tophi), overhanging bony edges and asymmetric joint wear.
Incorrect Answers:
Answer 1: Figure A is consistent with psoriatic arthritis. Notice the bilateral involvement and the pencil-in-cup deformity seen in the great toe.
Answer 3: Figure C is consistent with Freiberg’s infarction. Note the flattening of the second metatarsal head in addition to joint sclerosis
Answer 4: Figure D is consistent with Charcot arthropathy. Note the involvement of the hindfoot. There is fragmentation and severe joint space narrowing
Answer 5: Figure E is consistent with rheumatoid arthritis. Note the loss of asphericity of the 1st metatarsal head, with concomitant dislocations of the
2nd and 3rd MTP joints

Which of the following sarcomas is correctly paired with its most common translocation?

1) Alveolar rhabdomyosarcoma: t(9;22)

2) Synovial sarcoma: t(11;22)

3) Ewing's sarcoma: t(12;16)

4) Myxoid liposarcoma: t(X;18)

5) Clear cell sarcoma t(12;22)

Chromosomal translocations are characteristically associated with several sub- types of soft tissue sarcomas. The most common clear cell sarcoma translocation is t(12:22). A histologic example is found in illustration A.
Many sarcomas have distinct translocations which can help identify them via cytogenetic testing. The most common are alveolar rhabdomyosarcoma:t(2;13), synovial sarcoma:t(X;18), Ewing’s sarcoma: t(11,22), myxoid liposarcoma:t(12;16), and chondrosarcoma:t(9;22). Histologic examples are in Illustrations B through F, respectively. Osteosarcoma does not have a characteristic translocation.
In a review article, Rabbits described many fusion proteins resulting from chromosomal translocations. As many are nuclear proteins, future molecular
based therapies are being developed to target steps from oncogene transcription to RNA translation. Solomon et al reviewed chromosome aberrations in rare and common tumors. A broader understanding of chromosomal abnormalities and fusion proteins will aid gene-targeted diagnosis and therapies.

A 65-year-old female undergoes a total knee arthroplasty. In addition to chemoprophylaxis for deep vein thrombosis (DVT) prevention she is given pneumatic compression devices. Which of the following is associated with pneumatic compression devices?

1) Increased endothelial fibrinogenesis

2) Decreased bleeding times

3) Increased endothelial injury

4) Increased venous compliance

5) Increased venous blood flow

External pneumatic compression devices have been shown to prevent the formation of DVTs. Modern devices evacuate blood from lower-extremity vessels in an automated fashion. Pneumatic compression may exert its protective effect against thrombus formation in part by increasing venous blood flow. Pneumatic compression devices do
not decrease bleeding time or cause endothelial injury. Pneumatic compression devices enhance endothelial derived fibrinolysis and decrease venous compliance.
Rogers et al present practice management guidelines for DVT prophylaxis in trauma patients. They state that the exact mechanism of action of pneumatic compression devices are not fully understood. However, there is good evidence that they increase mean and peak femoral vein velocity and there are a few studies concluding that the fibrinolytic system is activated.

**Which of the following substances is most osteoinductive?**

1) Calcium phosphate

2) Hydroxyapatite

3) Xenograft collagen sheet

4) Cancellous allograft

5) Cancellous autograft

An ideal bone-graft substitute must provide scaffolding for osteoconduction as well as progenitor cells and growth factors for osteoinduction. Furthermore, the bone graft must be able to integrate with the host. Autogenous bone graft contains osteoblasts, endosteal osteoprogenitor cells capable of synthesizing new bone, and a structural matrix that acts as a scaffold, making it the gold standard for bone grafting. BMP-2 is a commonly utilized adjunct for grafting, and is inherently osteoinductive.
The referenced article by Buckwalter et al is a review on the biology of bone grafting which nicely defines the various osteoinductive and osteoconductive properties of the various bone graft options.

Regarding skeletal muscles, which of the following is true?

1) Force generated is most dependent on muscle length

2) Force generated is most dependent on muscle fiber type

3) Type I muscle is comprised of fast twitch fibrils

4) Duration and speed of contraction are most dependent on cross-sectional area

5) Duration and speed of contraction are most dependent on muscle fiber type

The duration and speed of contraction is most dependent on the muscle fiber type. The force generated by the muscle is most dependent on the cross- sectional area of the muscle.
Fiber types have less to do with the force of contraction and more to do with the duration and speed of contraction. The cross-sectional area of a muscle determines to a great extent the force generated by the muscle and is controlled by the number of myofibrils that contract. Muscle length affects contraction force through the Blix curve. The morphology of a muscle can affect the cross-sectional area by varying the angle of the fibers in relation to the force vector.
Incorrect Answers:

The correct approach to measure pressures in the central compartment of the foot is by directing the needle lateral and plantar through the abductor hallicus, just under the base of the first metatarsal. Abnormal values indicating the need for decompression are an absolute value of 30-45 mmHg or a Δp < 30mmHg (the difference between the patient's diastolic blood pressure and compartment pressures).
The most common symptom of compartment syndrome in the extremities is intense pain. However, compartment syndrome can be difficult to diagnose in children and patients who are comatose, nonverbal, and/or mentally compromised because they may not be able to properly express their level of pain. Additionally, in compartment syndrome of the foot, pain on passive extension of the toes may or may not be present, and swelling and absence of the dorsalis pedis pulse may be expected findings with extensive trauma to the foot, making the clinical diagnosis even more difficult. Thus, for patients with equivocal findings on physical exam, foot compartment pressures should be measured in order to confirm the diagnosis. There are 8 compartments in the foot: lateral, medial, central, and 4 interosseous. The lateral compartment
contains the abductor digiti minimi and flexor digiti minimi brevis, and is measured by directing the needle 1cm medial and plantar under the midshaft of the 5th metatarsal. The medial compartment contains the abductor hallicus and flexor hallicus brevis, and is measured by directing the needle lateral and plantar under the base of the first metatarsal. The central compartment contains the oblique head of the adductor hallucis, and is measured through the same approach as the medial compartment after advancing the needle more deeply. The 4 interosseous compartments entail the 2nd, 3rd, and 4th web spaces, and can be measured by directing the needle plantar into each respective dorsal webspace.
Ojika et al. performed a systematic review on foot compartment syndrome. They found that the most common cause of foot compartment syndrome was crush injury to the foot, and that diagnosis was mostly made through a combination of clinical findings and compartment pressure measurements.
Badhe et al. reported 4 cases where competent sensate patients developed compartment syndromes without any significant pain. They found that pain is not a reliable clinical indicator for underlying compartment syndrome, so in a competent sensate patient, the absence of pain does not exclude compartment syndrome. They concluded that a high index of clinical suspicion must prevail in association with either continuous compartment pressure monitoring or frequent repeated documented clinical examination with a low threshold for pressure measurement.
Flynn et al. looked at the diagnosis and outcome of acute traumatic compartment syndrome of the leg in children. They found that a delay in diagnosis may occur because acute traumatic compartment syndrome manifests itself more slowly in children or because the diagnosis is harder to establish in this age group. They state that the results of the present study should raise awareness of late presentation and the importance of vigilance for developing compartment syndrome in the early days after injury.
Figures A and B are lateral and Harris radiographs of the foot demonstrating a calcaneus fracture. Figure C is a cross-sectional image of the foot. Illustration A is an image depicting the compartments of the foot.
Incorrect Answers:
Answer 1: Path A is the incorrect approach for measuring the central compartment. Additionally, a Δp < 30mmHg (not > 30mmHg) is considered abnormal.
Answer 2: A Δp < 30mmHg (not > 30mmHg) is considered abnormal. Answer 4: Path C is the incorrect approach for measuring the central
compartment. Additionally, a Δp < 30mmHg (not > 30mmHg) is considered abnormal.
Answer 5: Path C is the incorrect approach for measuring the central compartment.

- Sclerosis of the proximal femoral epiphysis with subchondral lucency

- Index proximal IP flexion

- loss of elbow extensor power.
CLINICAL SITUATION FOR QUESTIONS 44 AND 45
A 19-year-old hockey player returns home from college over holiday break and experiences multiple recurrent dislocations only 1 year after an arthroscopic stabilization.