Orthopedic Surgery Mock Exam - Set E9DF28

The patient has recurrent instability and is at a high rate of further dislocations due to his young age. Therefore, therapy and bracing are unlikely to decrease his dislocation rate. The radiographs are normal, and there is no Hill-Sachs lesion or bony Bankart lesion. His instability severity index score is 3, and; therefore, a bony procedure such as Latarjet is not necessary. Furthermore, the rate of complication following a Latarjet procedure, especially nerve
injury and hardware problems, exceeds that of arthroscopic Bankart repair.

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:

The posterior and superior acromioclavicular ligaments provide the most restraint to posterior translation of the acromioclavicular joint and must be preserved during a Mumford procedure. Anterior and superior acromioclavicular joint ligaments are the opposite of the
nd prevent anterior translation of the clavicle. Injuries to the conoid and trapezoid ligaments are more pronounced with grade III or higher acromioclavicular separations, with superior migration of the clavicle relative to the acromion.
Correct answer : B

The patient has a displaced radial neck fracture. Displaced radial neck fractures with angulation of more than 30° to 45° require reduction. Methods of attempted closed reduction include wrapping the arm with an Esmarch’s bandage and applying direct pressure over the maximum deformity of the radial head. More aggressive methods include a Kirschner wire used as a joystick or intramedullary reduction as described by the Metaizeau technique. Open reduction should be avoided because of complications such as stiffness or osteonecrosis. Indications for open reduction are irreducible displacement of more than 45° with severe restriction of forearm rotation.
REFERENCES: Leung AG, Peterson HA: Fractures of the proximal radial head and neck in children with emphasis on those that involve the articular cartilage. J Pediatr Orthop
2000;20:7-14.
Radomisli TE, Rosen AL: Controversies regarding radial neck fractures in children. Clin Orthop 1998;353:30-39.
Skaggs DL, Mirzayan R: The posterior fat pad sign in association with occult fracture of the elbow in children. J Bone Joint Surg Am 1999;81:1429-1433.
Gonzalez-Herranz P, Alvarez-Romera A, Burgos J, et al: Displaced radial neck fractures in children treated by closed intramedullary pinning (Metaizeau technique). J Pediatr Orthop 1997;17:325-331.

The examination and MRI scan confirm a subscapularis rupture and dislocation of the long head of the biceps tendon. The greatest return of function will result from repair of the subscapularis and tenodesis of the biceps tendon. Physical therapy alone will result in inadequate healing of the subscapularis and will not address the biceps tendon. While biceps tenotomy is an option, it will not provide the same level of pain relief and return of function as a tenodesis in a young, active man. There is no evidence for a supraspinatus tear.
REFERENCES: Deutsch A, Altchek DW, Veltri DM, Potter HG, Warren RF: Traumatic tears of the subscapularis tendon: Clinical diagnosis, magnetic resonance imaging findings, and operative treatment. Am J Sports Med 1997;25:13-22.
Gerber C, Hersche O, Farron A: Isolated rupture of the subscapularis tendon. J Bone Joint Surg Am 1996;78:1015-1023.

This unstable ankle is associated with a complete disruption of the syndesmosis. With the information available, it is not likely that a high fibular fracture is present. One has to assume that the injury is limited to the syndesmosis. Although the deltoid ligament may be torn, one cannot determine this until the time of surgery. At surgery, if the mortise reduces well following insertion of screw(s), then the deltoid is left alone. If the talus does not reduce, then there may be deltoid tissue that needs to be removed before the reduction can be accomplished.

When performing revision TKA, the management of gap imbalance and joint line is of critical importance. The flexion gap is generally driven by femoral component size; increasing femoral component size by tightening the flexion gap and downsizing the femoral component size increases the flexion gap. Resecting more distal femur will open up the extension gap; augmenting the femur distally will tighten up the extension gap. Resecting more tibia affects both flexion and extension gaps equally.

This adolescent has symptomatic hallux valgus, and surgery is warranted. The motion at the metatarsophalangeal and talometatarsal joints is normal, and there is no evidence of hypermobility despite her generalized ligamentous laxity. Therefore, the modified Lapidus procedure is not indicated. With this deformity, a distal metatarsal osteotomy is ideal.

The clinical description and MR image point to an injury to the posterior cruciate ligament (PCL). This ligament is thought to be primarily composed of anterolateral and posteromedial bundles, with the former tightening in flexion and the latter in extension. Because of alterations in knee kinematics and increased varus alignment in PCL insufficiency, contact stresses and cartilage loads increase in the patellofemoral and medial compartments. Although good outcomes may be obtained with transtibial, open inlay, and arthroscopic inlay techniques, one major difference is the creation of the “killer-turn” during the transtibial approach. This sharp turn in the graft as it emerges from the tibia appears to lead to more pronounced attenuation and thinning of the graft during cyclic loading. The scenario describes a patient with chronic PCL and posterolateral corner (PLC) injury, as evidenced by the varus thrust and abnormal Dial test finding. A valgus-producing osteotomy may be effective, and, in fact, may be the only treatment necessary to address chronic PLC injury. Accordingly, an opening lateral osteotomy would not be appropriate. Of the remaining responses, an osteotomy that increases tibial slope would also address the PCL deficiency by reducing posterior tibial sag. Vascular injury is an uncommon, but potentially devastating, complication associated with PCL surgery and may occur regardless of the technique used.
Numerous strategies have been described to reduce the risk, including use of a posteromedial accessory incision to allow finger retraction of the popliteal neurovascular bundle, oscillating drills to prevent excessive soft-tissue entanglement, and tapered (rather than square) drill bits that may minimize cut-out of sharp edges as drilling reaches the posterior tibial cortex. Knee extension lessens, rather than increases, the distance between the posterior tibia and the neurovascular bundle and increases, not lessens, risk for _vascular injury._

DISCUSSION: The arthroscopic photo shows a grasper removing a loose body from the posterolateral compartment through an accessory posterolateral portal. The blunt arthroscopic trocar is placed through the intercondylar notch in the direction of the posterior horn of the lateral meniscus. The trocar passes between the ACL and the posterior aspect of the lateral femoral condyle into the posterolateral compartment.
REFERENCES: Wu WH, Richmond JC: Arthroscopy of the knee: Basic setup and techniques, in McGinty JB (ed): Operative Arthroscopy, ed 3. Philadelphia, PA, Lippincott-Raven, 2003, pp 215-216. Kramer DE, Bahk MS, et al: Posterior knee arthroscopy: Anatomy, technique, application. J Bone Joint Surg Am 2006;88:110-121.

Moed et al performed a study to determine the clinical outcome in patients in whom a displaced fracture of the posterior wall of the acetabulum had been treated by open reduction and internal fixation. They were able to show good to excellent clinical results for patients who underwent anatomic reduction and internal fixation of posterior wall acetabulum fractures as assessed using radiographs. Fractures in elderly patients and patients who sustained extensive comminution were more likely to have worse clinical result.
In a separate study, Moed et al. evaluated the results of 67 patients who underwent ORIF of a posterior wall fractures by assessing the accuracy of postoperative AP pelvis, obturator oblique films, iliac oblique films, and CT scans. They found that postoperative pelvic CT scan was the most accurate way to judge final fracture reduction and was able to pick up residual fracture displacements that were not seen on postoperative plain radiographs. They concluded that the accuracy of reduction as assessed on postoperative CT scan was the most reliable indicator of clinical outcomes.

Squamous cell carcinoma of the fingertip/nail region is uncommon but remains the most common malignancy in the hand. A high degree of suspicion is needed to diagnose this condition. Biopsy and radiographs are necessary initially. The subsequent treatment depends on the extent of the lesion at the time of presentation. Treatment can vary from Mohs micrographic surgery (MMS) to digital amputation. Amputation is recommended when bone involvement is present. In this patient, because the distal phalanx tip is involved and no further bone involvement proximally was observed, an amputation at the IP joint level is recommended. More proximal involvement would require a more proximal amputation level. Curettage and bone graft is not appropriate for this malignant lesion. External beam radiation therapy is not a first-line treatment option for this condition. Metastatic spread is uncommon. MMS is inappropriate when bone invasion has occurred.

DISCUSSION: The patient has developmental dysplasia of the hip (DDH). There is anterolateral deficiency of the acetabulum as is evidenced by the increased acetabular index and the reduced center- edge angle. The patient has some arthritis of the hip with narrowing of the joint space and cyst formation visible on the radiograph. Although all of the mentioned choices may be acceptable treatments for dysplasia of the hip, periacetabular osteotomy is the best and most appropriate option for this young patient. Periacetabular osteotomy allows correction of the problem and can even improve the joint space as the new region of the acetabulum is rotated into the weight-bearing region. Hip fusion is very poorly tolerated by young patients, especially women. Femoral osteotomy alone is unlikely to address the problem because the major problem is on the acetabular side. Although the patient has arthritis, because of the young age of the patient, prosthetic replacement is not an attractive option. The outcome of periacetabular osteotomy even for patients with moderate arthritis has been favorable, deferring the need for total hip arthroplasty by a mean of 6.5 years.

REFERENCES: Weinstein SL, Mubarak SJ, Wenger DR: Developmental hip dysplasia and dislocation: Part 1. Instr Course Lect 2004;53:523-530.
Parvizi J, Burmeister H, Ganz R: Previous Bernese periacetabular osteotomy does not compromise the results of total hip arthroplasty. Clin Orthop Relat Res 2004;423:118-122.

Figure 74

Normal activities increase forces over the hip to three times body weight. Jogging increases forces across the hip by five to eight times body weight

Isometric quadriceps contraction between 15 and 30 degrees of flexion creates significant strain in the ACL and potential damage to the reconstructed graft. Isolated quadriceps contraction with knee flexion of greater than 60 degrees, hamstring contraction at any angle of knee flexion, and active knee motion between 35 and 90 degrees of flexion create substantially less strain in the properly implanted ACL graft.
REFERENCES: Beynnon BD, Gleming BC, Johnson RL, Nichols CE, Renstrom PA, Pope MH: Anterior cruciate ligament strain behavior during rehabilitation exercises in vivo. Am J Sports Med 1995;23:24-34.
Beynnon BD, Johnson RJ, Fleming BC, Stankewaich CJ, Renstrom PA, Nichols CE: The strain behavior of the anterior cruciate ligament during squatting and active flexion-extension: A comparison of an open and a closed kinetic chain exercise. Am J Sports Med 1997;25:823-829.

Elbow flexion is central to management of brachial plexus management because it serves the most important function of feeding.

The images delineate progressive osteoporotic collapse. As outlined by Kado and associates, Schlaich and associates, and Gold and associates, the progression of spinal deformity and the functional consequences of vertebral compression fractures are persistent even in those patients who are pain free. Vertebral compression fractures are associated with deteriorating gait, early satiety, further future fracture risk, and deteriorating lung function.

The axillary nerve is at most risk in this area of the glenohumeral joint as it passes adjacent to and just inferior to the 6 o’clock position. Although performing capsular shifts within and up to 1 cm from the glenoid rim is generally considered safe, taking large amounts of capsule (>1 cm) in this region in an effort to tighten the capsule can inadvertently damage the nerve as it crosses there.
The musculocutaneous nerve does not cross in this region, although it can be injured during dissection around the coracoid, such as in arthroscopic Latarjet procedures. The musculocutaneous nerve branches to the lateral cutaneous nerve and provides sensory innervation to the lateral aspect of the forearm.
70
The suprascapular nerve crosses superior and posterior to the glenoid and is at greatest risk during transglenoid screw placement in the anteroposterior directions. The suprascapular nerve innervates the supraspinatus and the infraspinatus. The radial nerve courses behind the humeral shaft and can be damaged during bicortical fixation in the anterior to posterior direction in this region. A radial nerve palsy would result in wrist extension weakness.

The coupled action of the rotator cuff prevents superior migration and controls anterior and posterior translation by depressing the humeral head.

Scientific References

: Poppen NK, Walker PS: Normal and abnormal motion of the shoulder. J Bone Joint Surg Am 1976;58:195-201.
Abrams JS: Special shoulder problems in the throwing athlete: Pathology, diagnosis, and nonoperative management. Clin Sports Med 1991;10:839-861.

The longitudinal fibers forming layer 1 of the palmar aponeurosis insert into the dermis and, when contracted, give rise to skin pits. The pretendinous bands give rise to the central cord. C ontractures of the natatory ligament give rise to the natatory cord. Vertical fibers and septae do not give rise to pits.

The most common reason for a nerve deficit following shoulder arthroplasty is a temporary neuropraxia due to stretch. Correct Answer: Temporary neuropraxia due to stretch

- diabetes.

C ompared to normal palmar fascia, the fibrous bands in Dupuytrenâs disease have an increased ratio of type III to type I
collagen, and an overall increase in the amount of type III collagen.

■
Interspinous devices are utilized to mitigate the symptoms of neurogenic claudication secondary to lumbar spinal stenosis with forced forward flexion. Interspinous devices can be classified as a distracting device or a stabilizing device. The inhibition of extension with a blocking device widens the central canal and foraminal height and decreases the load on the facet joints. Various types of interspinous devices have been shown to decrease the ODI and VAS scores.

The most common reason for recurrent or persistent symptoms of first dorsal compartment stenosis is failure to recognize and release a separate extensor pollicis brevis subsheath. The superficial radial sensory nerve may be injured in surgery for De Quervain disease, but the resulting neuroma is often more painful than the original symptoms and is of a different character. Abductor pollicis longus laceration would result in loss of radial abduction of the thumb. Early motion of the thumb is recommended following release of the first dorsal compartment.

Temperature, humidity, mixing rate, and added agents affect the rate of polymerization. The materials with which the polymer and powder contact are not known to affect this rate.

A slipped capital femoral epiphysis is most common in adolescent boys who are overweight. Examination must include evaluation of the hip, thigh, and knee and usually reveals limited internal rotation of the hip. At times, the condition is associated with concomitant renal or endocrine abnormalities or a history of radiation therapy to the region. The cross-over sign is 51 a radiographic finding indicative of acetabular retroversion and is seen in pincer-type femoroacetabular impingement. The posterior wall sign is seen in pincer-type femoroacetabular impingement when the center of the femoral head is lateral to the lateral border of the posterior wall of the acetabulum. It is indicative of acetabulum posterior wall deficiency. Patients who undergo solid organ transplantation frequently are treated with steroid immunosuppression. This treatment is a well-known risk factor for osteonecrosis of
the femoral head. Protrusio acetabula are frequently seen in patients with systemic inflammatory arthropathy. In patients with rheumatoid arthritis involving the hip, the status of the cervical spine must be considered before proceeding with surgery.
RECOMMENDED READINGS
1. [Aronsson DD, Loder RT, Breur GJ, Weinstein SL. Slipped capital femoral epiphysis: current concepts. J Am Acad Orthop Surg. 2006 Nov;14(12):666-79. Review. PubMed PMID: 17077339.](http://www.ncbi.nlm.nih.gov/pubmed/17077339)[View Abstract at PubMed](http://www.ncbi.nlm.nih.gov/pubmed/17077339)
2. Nepple JJ, Prather H, Trousdale RT, Clohisy JC, Beaulé PE, Glyn-Jones S, Rakhra K, Kim YJ. Diagnostic imaging of femoroacetabular impingement. J Am Acad Orthop Surg. 2013;21 Suppl 1:S20-6. doi: 10.5435/JAAOS-21-07-S20. PubMed PMID:
[23818187.](http://www.ncbi.nlm.nih.gov/pubmed/23818187)[View Abstract at PubMed](http://www.ncbi.nlm.nih.gov/pubmed/23818187)
3. [Lavernia CJ, Sierra RJ, Grieco FR. Osteonecrosis of the femoral head. J Am Acad Orthop Surg. 1999 Jul-Aug;7(4):250-61. Review. PubMed PMID: 10434079. ](http://www.ncbi.nlm.nih.gov/pubmed/10434079)[View](http://www.ncbi.nlm.nih.gov/pubmed/10434079)[ ](http://www.ncbi.nlm.nih.gov/pubmed/10434079)[Abstract at PubMed](http://www.ncbi.nlm.nih.gov/pubmed/10434079)
4. McBride MT, Muldoon MP, Santore RF, Trousdale RT, Wenger DR. Protrusio acetabuli: diagnosis and treatment. J Am Acad Orthop Surg. 2001 Mar-Apr;9(2):79-
[88/. Review. PubMed PMID: 11281632.](http://www.ncbi.nlm.nih.gov/pubmed/11281632)[View Abstract at PubMed](http://www.ncbi.nlm.nih.gov/pubmed/11281632)

C hildren ages 4 to 8 (40 lbs to 60 lbs) are at risk for airbag injuries and should not be in the front seat. In addition, they require booster seats to allow proper fitting of the shoulder harness on the upper torso. Rear-facing seats are only appropriate for infants. C hildren should not be in the front seat until after age 12 and over 100 lbs.

Intravenous antibiotics alone will not adequately treat this infection. At 8 weeks after surgery, the hardware must be removed because Staphylococcus aureus is a virulent microbe. VAC therapy alone is not adequate without debridement and hardware removal, but it may play a role in postoperative wound care. Calcanectomy is a salvage procedure for calcaneal osteomyelitis or recalcitrant heel ulceration.
REFERENCES: Benirschke SK, Kramer PA: Wound healing complications in closed and open calcaneal fractures. J Orthop Trauma 2004;18:1-6.
Lim EV, Leung JP: Complications of intra-articular calcaneal fractures. Clin Orthop
2001;391:7-16.
Folk JW, Starr AJ, Early JS: Early wound complications of operative treatment of calcaneus fractures: Analysis of 190 fractures. J Orthop Trauma 1999;13:369-372.

Anterior dislocation is the most common type of sternoclavicular dislocation. The medial end of the clavicle is displaced anterior or anterosuperior to the anterior margin of the sternum. In a study by Omer, 31% of athletic injuries have been known to cause a dislocation of the sternoclavicular joint. The serendipity view can show this dislocation, as will CT of the chest. This view requires the x-ray beam to be aimed at the manubrium with 40 degrees of cephalic tilt. An anterior sternoclavicular joint dislocation will appear superiorly displaced, while a posterior sternoclavicular joint dislocation is inferiorly displaced on the serendipity view.
REFERENCES: Rockwood CA Jr, Matsen FA III (eds): The Shoulder. Philadelphia, PA, WB Saunders, 1998, vol 1, pp 566-572.
Omer GE Jr: Osteotomy of the clavicle in surgical reduction of anterior sternoclavicular dislocation. J Trauma 1967;7:584-590.

Key features of Pagetâs disease
Remodeling disease caused by excessive osteoclastiCactivity
Rarely diagnosed in patients younger than 40 years of age; most patients diagnosed after age 50
Most common sites include pelvis, femur, spine, skull, and tibia
Less common sites include clavicles, scapulae, ribs, and facial bones
Rarely found in the hands and feet
PagetiCbone
is more susceptible to fracture is less compact
is more vascular
tends to bow in weight bearing areas
GeographiCclustering (up to 4% in patients older than 55 years of age) England
Northern Europe North America Australia, New Zealand
Rare in Asia, China, Indonesia, Malaysia, and sub-Saharan Africa
Possibly a slow viral disease
RNA paramyxovirus (e.g., respiratory syncytial virus and measles) Correct Answer: Sub-Saharan Africa

Age and having three or more comorbidities is associated with a higher rate of complications in patients undergoing a lumbar fusion for lumbar degenerative spondylolisthesis. Race,gender, and hospital size have not been found to be associated with higher complication rates.

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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:

Although the angle of trunk rotation (ATR) does not convert directly to a C obb angle, there are population-based figures for mean curve at each ATR. The mean C obb angle for curves having a 7° ATR is 20°.

The goal in this patient is to provide safe, effective, and long-acting analgesia. Meperidine is recommended in this circumstance. It is an opioid that provides intermediate and long-term analgesia. Additionally, it does not cause the associated histamine release and bronchospasm that can occur in patients with asthma and atopia.
Ketamine would provide short-term analgesia, but would also alter the level of consciousness.
Morphine is well known for precipitating bronchospasm in patients with atopia and asthma. Therefore, it would not be the best choice in the scenario presented.
Methohexital (a barbiturate) and midazolam (a benzodiazepine) both cause decreased awareness and have no analgesic properties.

DISCUSSION: The purpose of this question is to draw attention to the early risks of therapeutic anticoagulation that will be instituted by an intensivist or pulmonologist to treat a life-threatening pulmonary embolus. The temporary vena cava filter is a recent innovation but will effectively reduce the risk of further pulmonary emboli. This requires reversal of anticoagulation for safe insertion of the filter and creates a safe situation for additional surgical solutions. Sciatic nerve compromise was caused by the expanding hematoma in this patient, which could be mitigated by exploration both to assess the nerve and to remove a large hematoma that presents its own long- term risks.
REFERENCES: Della Valle CJ, Steiger DJ, Di Cesare PE: Thromboembolism after hip and knee arthroplasty: Diagnosis and treatment. J Am Acad Orthop Surg 1998;6:327-336.
Weil Y, Mattan Y, Goldman V, et al: Sciatic nerve palsy due to hematoma after thrombolysis therapy for acute pulmonary embolism after total hip arthroplasty. J Arthroplasty 2006;21:456-459.
American Academy of Orthopaedic Surgeons Guideline on the Prevention of Symptomatic Pulmonary Embolism in Patients Undergoing Total Hip or Knee Arthroplasty, [www.aaos.org/research/guidelines/](http://www.aaos.org/research/guidelines/) PEguide.asp

Pseudohypoparathyroidism (AHO) - end-organ insensitivity; in AHO, germline mutation that leads to loss of function of Galpha S (GNAS1); causes end-organ resistance to PTH
1/. PHP - short stature, short metacarpals (4th and 5th), rounded facies a. Mental retardation, tetany
b. Sex-linked dominant
2/. Laboratory features a. Hypocalcemia
b. Hyperphopshatemia c. Normal PTH

The patient appears to be experiencing a recurrent gout flare. The best way to confirm the diagnosis is to aspirate the joint and send it for culture, cell count, and crystal examination. This will identify the diagnosis of infection, gout, or pseudogout. An MRI scan will confirm the presence of an effusion, but it will not reveal the cause. A splint may result in pain improvement, but it will not contribute to a diagnosis or definitive treatment. Sedimentation rate and
61
C-reactive protein levels can be elevated in either inflammatory or infectious processes, but these are non-specific and cannot differentiate between the two.

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.

Anterior posterior compression (APC) injuries have the highest mortality rates of the fracture patterns listed.
APC injuries have high rates of concomitant thoracic and abdominal visceral injuries leading to the highest rates of mortality among pelvic fractures. Lateral compression (LC) fractures have particularly high incidences of associated brain and head injury with lower mortality than APC injuries. Overall, as the grade of pelvic ring injury increases the rates of associated injuries increases, regardless of exact mechanism of injury. The overall mortality rate for any pelvic trauma is roughly 15%, with APC III mortality around 37%, and overall
APC mortality rates around 26%. LC of any grade has an estimated mortality around 13%. Vertical shear and CMI have estimated mortality of 25% and 17.1%, respectively. The lowest mortality rates are following acetabular fractures with estimates around 1.5%.
Dalal et al retrospectively reviewed 340 trauma patients with pelvic injuries to analyze organ injury, resuscitative requirements, and outcomes. They found the highest mortality rates were in APC III and that more severe APC injuries had greater organ damage and mortality. They conclude that the mechanical force type and classification of injury are predictors of organ injury pattern, resuscitation needs, and mortality.
Eastridge et al reviewed 1,014 injured pedestrians for pelvic injuries, associated injuries, and relationship of treatments to outcomes. They found the highest mortality rates were associated with APC III and LC III injuries patterns at 50%. They conclude that pelvic fractures are a sign of significant energy imparted on the body and severity of associated injuries lead to the high rates of morbidity and mortality.
Illustration A and B show an APC III and LC III injury, respectively. Incorrect Answers:
Answer 2, 3, 4, and 5: LC III, acetabular fracture, vertical shear, and combined
mechanism injuries all have lower mortality rates than APC injuries.

This is a classic presentation of an acute traumatic distal biceps tendon rupture. In the dominant extremity of a manual laborer, this injury can result in approximately 40% loss of supination strength. Although not required, an MRI scan can confirm
the diagnosis. In general, a single incision anterior or two incision anterior/ posterior repair can be utilized for surgical intervention with similar success rates. Although the percentage of complications is similar between surgical approaches, the type of complications can vary. Anterior only repairs have a
20
higher risk of traction injury to the lateral antebrachial cutaneous nerve (LABC) secondary to the degree of retraction required for exposure in muscular patients. Posterior repairs have a higher risk for radiographic heterotopic bone formation. Fortunately, most LABC injuries are neuropraxias and resolve with observation, but resolution may take up to 6 months. In this case, ongoing observation is appropriate, with surgical exploration being considered only in chronic cases. Patients should be appropriately counseled about this issue prior to surgery.

DISCUSSION:
Classic posterior elbow dislocations result from a posterolateral rotatory mechanism, whereby the hand is fixed (typically on the ground) while the weight of the body creates a valgus and external rotation moment on the elbow. This results first in tearing of the lateral collateral ligament that proceeds medially through the anterior and posterior joint capsules, ending with potential involvement of the ulnar collateral ligament (but this is not universal). McKee and associates assessed the lateral soft-tissue injury pattern of elbow dislocations
with and without associated fractures at the time of surgery. Injury to the lateral collateral ligament complex was seen in every case, with avulsion from the distal humerus as the most common finding. Midsubstance
tears, proximal avulsions, and distal bony avulsions of the ulnar collateral ligament are less common.

Disorders of the hip can mimic and/or coexist with lumbar spine disorders. The prevalence of hip pain lasting longer than 1 month in patients ages 65 to 74 years is 19%. There is often overlap between their respective signs and symptoms. In a patient with failed back surgery syndrome, hip pathology may have been present before back surgery and not recognized. Osteoarthritis of
the hip typically causes groin and anterior thigh pain. Meralgia paraesthetica is more likely to manifest immediately after surgery. Trochanteric bursitis usually affects the proximal lateral thigh and often can radiate to the distal thigh. Facet joint pain causes low-back pain that can be referred to the gluteal region. Epidural hematoma 6 weeks after surgery is highly unlikely.
RECOMMENDED READINGS
Bolt PM, Wahl MM, Schofferman J: The roles of the hip, spine, sacroiliac joint, and other structures in patients with persistent pain after back surgery. Seminars in Spine surgery 2008;20:14-19.
[Brown MD, Gomez-Marin O, Brookfield KF, Li PS. Differential diagnosis of hip disease versus spine disease. Clin Orthop Relat Res. 2004 Feb;(419):280-4. PubMed PMID: 15021166. ](http://www.ncbi.nlm.nih.gov/pubmed/15021166)[View](http://www.ncbi.nlm.nih.gov/pubmed/15021166)[ ](http://www.ncbi.nlm.nih.gov/pubmed/15021166)[Abstract at PubMed](http://www.ncbi.nlm.nih.gov/pubmed/15021166)

The MR images show a tear through a discoid lateral meniscus. A discoid meniscus is caused by a failure of apoptosis during development in utero and is considered a congenital abnormality. Discoid menisci are prone to tearing and can be caused by minimal trauma. There is no known genetic cause for this condition. Radiographic findings that may be present in the setting of a discoid meniscus include lateral joint space widening, squaring of the lateral femoral condyle, and cupping of the lateral tibial plateau. Contralateral discoid menisci are noted in 20% of patients. There are no other known associated conditions. Treatment _of a symptomatic discoid meniscus should include partial meniscectomy and saucerization or repair._

The patient has a hyperostotic condition of the cervical spine, most likely ankylosing spondylitis. Because of a rigid and osteoporotic spine, relatively minor falls can result in unstable spinal injuries with significant instability and a high risk for neurologic sequelae. The patient has an unstable injury at C6 with an incomplete spinal cord injury, necessitating urgent decompression and stabilization.Studies have shown that, in
patients with ankylosing spondylitis, stand-alone anterior stabilization results in a high failure rate. Halo-thoracic vests carry a high risk of septic and pulmonary issues, especially in the elderly. Uninstrumented fusion will provide insufficient stability in such patients.

- Walking boot and weight bearing as tolerated until pain subsides_

This patient demonstrates the common finding of fixed forefoot varus associated with a flexible flatfoot deformity. It is likely that a gastrocnemius contracture is also present, but this is not always the case. Arthritis of the calcaneocuboid joint rarely occurs following a lengthening calcaneal osteotomy in an adult. C orrection of the forefoot varus is best accomplished with an opening wedge osteotomy of the medial cuneiform. Arthrodesis of the first tarsometatarsal joint may be performed in selected patients
with noted instability at this joint.

- Intraoperative neurological injury

The patient has a valgus deformity and has developed stiffness in both flexion and extension. Given the progressive loss of motion, progression to TKA is indicated. Manipulation under anesthesia would not be efficacious to prevent the progressive loss of motion without correcting the underlying mechanical issues. The patient has global pain; and therefore, unicompartmental knee arthroplasty is not ideal. Stem cell injection in this setting has not been proven.