OITE & ABOS Board Review: Fracture, Hip & Knee MCQs

Question 1

Figure 9 shows the AP radiograph of a 65-year-old man who has knee pain and swelling. What is the most likely diagnosis?

Explanation

DISCUSSION: Although all the choices are known causes of joint degeneration (secondary osteoarthritis), only chondrocalcinosis shows distinct linear calcification of the cartilage due to deposition of calcium pyrophosphate crystals. Gout is a recurrent acute arthritis resulting from the deposition of monosodium urate from supersaturated hyperuricemic body fluids. Hemochromotosis is characterized by focal or generalized deposition of iron within body tissues. Arthritis may be present but is less common than other manifestations such as liver cirrhosis, skin pigmentation, diabetes mellitus, and cardiac disease. Rheumatoid arthritis is a nonspecific, usually symmetric inflammation of peripheral joints resulting in destruction of articular and periarticular structures. Ochronosis is a hereditary enzyme deficiency (homogentisic acid oxidase) resulting in deposition of homogentisic acid polymers in articular cartilage.
REFERENCES: Barrack RL, Booth RE Jr, Lonner JH, et al (eds): Orthopaedic Knowledge Update: Hip and Knee Reconstruction 3. Rosemont, IL, American Academy of Orthopaedic Surgeons, 2006, p 188.
Berkow R (ed): The Merck Manual, ed 14. Rathway, NJ, Merck, 1984, pp 910, 1176, 1200.

Question 2

If a surgeon inadvertently burrs through the midlateral wall of C5 during a anterior corpectomy, what structure is at greatest risk for injury?

Explanation

DISCUSSION: The vertebral artery is contained within the vertebral foramen and thus tethered alongside the vertebral body, making it vulnerable to injury if a drill penetrates the lateral wall. The C5 root passes over the C5 pedicle and is not in the vicinity. The C6 root passes under the C5 pedicle but is posterior to the vertebral artery and is only vulnerable at the very posterior-inferior corner. The carotid artery and the vagus nerve are both within the carotid sheath and well anterior.
REFERENCES: Pfeifer BA, Freidberg SR, Jewell ER: Repair of injured vertebral artery in anterior cervical procedures. Spine 1994;19:1471-1474.
Gerszten PC, Welch WC, King JT: Quality of life assessment in patients undergoing nucleoplasty-based percutaneous discectomy. J Neurosurg Spine 2006;4:36-42.

Question 3

In patients with displaced radial neck fractures treated with open reduction and internal fixation with a plate and screws, the plate must be limited to what surface of the radius to avoid impingement on the proximal ulna?

Explanation

DISCUSSION: The radial head is covered by cartilage on 360 degrees of its circumference. However, with the normal range of forearm rotation of 160 to 180 degrees, there is a consistent area that is nonarticulating. This area is found by palpation of the radial styloid and Lister’s tubercle. The hardware should be kept within a 90-degree arc on the radial head subtended by these two structures.
REFERENCES: Smith GR, Hotchkiss RN: Radial head and neck fractures: Anatomic guidelines for proper placement of internal fixation. J Shoulder Elbow Surg 1996;5:113-117.
Caputo AE, Mazzocca AD, Santoro VM: The nonarticulating portion of the radial head: Anatomic and clinical correlations for internal fixation. J Hand Surg Am 1998;23:1082-1090.

Question 4

A 57-year-old man reports right hip pain that has been progressive for the past several months. The pain is exacerbated by weight-bearing activities and improves somewhat with rest. A radiograph is shown in Figure 10a and a coronal T 1 -weighted MRI scan is shown in Figure 10b. What is the most likely diagnosis?

Explanation

DISCUSSION: These are classic findings of osteonecrosis of the hip. The radiograph reveals the subchondral sclerotic pattern commonly seen in osteonecrosis and is quite extensive in this patient. The MRI scan reveals the typical serpentine-like region of low signal intensity with a central zone where the signal is similar to fat.
REFERENCES: Resnick D (ed): Diagnosis of Bone and Joint Disorders. Philadelphia, PA,

WB Saunders, 2002, pp 3160-3162.
Sugano N: Osteonecrosis, in Fitzgerald R Jr, Kaufer H, Malkani A (eds): Orthopaedics. Philadelphia, PA, Mosby International, 2002, pp 877-887.

Question 5

The arrow in Figure 11 points toward a finding consistent with which of the following?

Explanation

DISCUSSION: The finding of a unilateral absent pedicle is often referred to as a winking owl sign and is a manifestation of pedicle destruction from metastatic disease. As the vertebral body is destroyed from the neoplastic process, it extends into the pedicle and destroys the cortical rim that normally creates the oval ring of the pedicle on an AP image.
REFERENCES: McLain R, Weinstein J (eds): Rothman-Simeone: The Spine, ed 4. Philadelphia, PA, WB Saunders, 1999, p 1173.
Koval KJ (ed): Orthopaedic Knowledge Update 7. Rosemont, IL, American Academy of Orthopaedic Surgeons, 2002, p 674.

Question 6

The attachments of the transverse carpal ligament include which of the following structures?

Explanation

DISCUSSION: The transverse carpal ligament is the volar boundary of the carpal tunnel. It attaches to the scaphoid and trapezium radially and the pisiform and the hook of the hamate ulnarly. The ulna and trapezoid do not receive attachments of the transverse carpal ligament.
REFERENCES: Hollinshead W: Anatomy for Surgeons: The Back and Limbs, ed 3. Philadelphia, PA, Harper and Row, 1982, vol 3, pp 471-472.
Hoppenfeld S, deBoer P: Surgical Exposures in Orthopaedics, ed 2. Philadelphia, PA, Lippincott-Raven, 1994, pp 168-170.

Question 7

A 23-year-old woman falls from a bicycle and sustains a right knee injury. Figures 12a through 12d show radiographs and MRI scans of the knee. What is the most likely diagnosis?

Explanation

DISCUSSION: The radiographs and MRI scans both show an avulsion of the anterior cruciate ligament, which has been described by Meyers and McKeever in three different fracture patterns. Type I fractures are nondisplaced or have minimal displacement of the anterior margin. Type II fractures have superior displacement of their anterior aspect with an intact posterior hinge. Type III fractures are completely displaced. Although the injury is visible on the radiographs, it is more subtle in adults than children. Thus, MRI is helpful in clarifying this injury in adults. Open or arthroscopic reduction and internal fixation is recommended for type II and type III fractures that do not respond to closed reduction.
REFERENCES: Meyers MH, McKeever FM: Fracture of the intercondylar eminence of the tibia. J Bone Joint Surg Am 1970;52:1677-1684.
Wiss DA, Watson JT: Fractures of the tibial plateau, in Rockwood CA, Green DP, Bucholz RW, et al (eds): Rockwood and Green’s Fractures in Adults. Philadelphia, PA, Lippincott-Raven, 1996, pp 1920-1953.
Lubowitz JH, Elson WS, Guttmann D: Arthroscopic treatment of tibial plateau fractures: Intercondylar eminence avulsion fractures. Arthroscopy 2005;21:86-92.

Question 8

A 25-year-old man has a mass on the medial aspect of the left knee. He reports that the mass has been present for several years, but a recent increase in physical activity has resulted in periodic tenderness. Radiographs are shown in Figures 13a and 13b. What is the most likely diagnosis?

Explanation

DISCUSSION: The radiographs reveal a sessile lesion projecting from the medial aspect of the distal femur. The lesion shares the cortex with the bone and the base communicates with the medullary space of the femur. This is the classic appearance of an osteochondroma, the most common benign tumor of bone.
REFERENCES: Menendez LR (ed): Orthopaedic Knowledge Update: Musculoskeletal Tumors. Rosemont, IL, American Academy of Orthopaedic Surgeons, 2002, pp 103-111.
Parsons TW: Benign bone tumors, in Fitzgerald R Jr, Kaufer H, Malkani A (eds): Orthopaedics. Philadelphia, PA, Mosby International, 2002, pp 1027-1035.

Question 9

A previously asymptomatic 40-year-old man injures his shoulder in a fall. Examination shows that he is unable to lift the hand away from his back while maximally internally rotated. An axial MRI scan of the shoulder is shown in Figure 14. What is the most likely diagnosis?

Explanation

DISCUSSION: The MRI scan shows detachment of the subscapularis from its insertion on the lesser tuberosity. The examination finding is consistent with a positive lift-off test, also indicating a tear of the subscapularis.
REFERENCES: Lyons RP, Green A: Subscapularis tendon tears. J Am Acad Orthop Surg 2005;13:353-363.
Warner JJ, Higgins L, Parsons IM, et al: Diagnosis and treatment of anterosuperior rotator cuff tears. J Shoulder Elbow Surg 2001;10:37-46.

Question 10

A patient is treated with volar plating for a distal radius fracture. The CT scan shown in Figure 15 is obtained after union of the fracture because the patient reports ongoing symptoms. The prominent hardware is most likely injuring what tendon?

Explanation

DISCUSSION: Extensor tendon injuries have been reported after volar plating of distal radius fractures. The CT scan shows prominent dorsal hardware a few millimeters ulnar to Lister’s tubercle. The second compartment, the ECRL and ECRB, is radial to Lister’s tubercle. The ECU runs along the distal ulna. The contents of the fourth dorsal compartment run just ulnar to Lister’s tubercle. The EDC tendon is likely irritated in this patient. The EPB runs along the radial border of the radius and is well away from prominent hardware.
REFERENCES: Benson EC, Decarvalho A, Mikola EA, et al: Two potential causes of EPL rupture after distal radius volar plate fixation. Clin Orthop Relat Res 2006;451:218-222.
Cooney WP, Linscheid RL, Dobyns JH (eds): The Wrist: Diagnosis and Operative Treatment. Philadelphia, PA, Mosby-Year Book, 1998.

Question 11

A 9-year-old child sustains a proximal tibial physeal fracture with a hyperextension mechanism. What structure is at most risk for serious injury?

Explanation

DISCUSSION: The most serious injury associated with proximal tibial physeal fracture is vascular trauma. The popliteal artery is tethered by its major branches near the posterior surface of the proximal tibial epiphysis. During tibial physeal displacement, the popliteal artery is susceptible to injury. Injuries to the other structures are less common.
REFERENCE: Beaty JH, Kasser JR: Rockwood and Wilkins Fractures in Children. Philadelphia, PA, JB Lippincott, 2006, p 961.

Question 12

A 25-year-old tennis player has shoulder pain and weakness to external rotation. MRI scans are shown in Figures 16a and 16b. What is the most likely cause of his weakness?

Explanation

DISCUSSION: The MRI scans show a paralabral cyst, which is most commonly associated with labral tears. Compression of the suprascapular nerve results in weakness of the supraspinatus and/or infraspinatus depending on the level of compression.
REFERENCES: Piatt BE, Hawkins RJ, Fritz RC, et al: Clinical evaluation and treatment of spinoglenoid notch ganglion cysts. J Shoulder Elbow Surg 2002;11:600-604.
Inokuchi W, Ogawa K, Horiuchi Y: Magnetic resonance imaging of suprascapular nerve palsy.

J Shoulder Elbow Surg 1998;7;223-227.

Question 13

The posterior approach to the proximal radius uses what intermuscular interval?

Explanation

DISCUSSION: Knowledge of intermuscular and internervous planes allows safe exposures throughout the body. The posterior (Thompson) approach to the proximal forearm uses the interval between the extensor carpi radialis brevis and extensor digitorum communis. The anterior (Henry) approach to the proximal forearm uses the interval between the brachioradialis and the flexor carpi radialis.
REFERENCES: Spinner M: Injuries to the Major Branches of Peripheral Nerves of the Forearm, ed 2. Philadelphia, PA, WB Saunders, 1978, pp 66-77.
Henry AK: Extensile Exposure, ed 3. New York, NY, Churchill Livingstone, 1995.

Question 14

Which of the following statements best describes the anatomic considerations of the popliteal artery posterior to the knee joint?

Explanation

DISCUSSION: Popliteal artery injury during total knee arthroplasty is relatively rare. Knee flexion, the position that occurs during most of the arthroplasty procedure, allows the popliteal vessels to fall posteriorly, further away from harm. Anatomically, the popliteal artery lies anterior to the popliteal vein and 9 mm posterior to the posterior aspect of the tibial plateau in

90 degrees of flexion.
REFERENCES: Barrack RL, Booth RE Jr, Lonner JH, et al (eds): Orthopaedic Knowledge Update: Hip and Knee Reconstruction 3. Rosemont, IL, American Academy of Orthopaedic Surgeons, 2006, p 151.
Anderson JE: Grant’s Atlas of Anatomy, ed 7. Baltimore, MD, Lippincott Williams & Wilkins, 1978, pp 4-53.

Question 15

A 62-year-old woman reports diffuse aches and pains of the hip and pelvis. She denies any significant trauma but does have a history of chronic anemia. Figure 17a shows a radiograph of the pelvis, and Figures 17b and 17c show T 2 -weighted MRI scans. What is the most likely diagnosis?

Explanation

DISCUSSION: The radiograph reveals diffuse osteopenia and areas in the proximal femora that are moth-eaten in appearance. The extent of the marrow-replacing process is evident on the MRI scans, which reveal signal abnormality throughout the entire pelvis and both proximal femora. This represents a marrow-packing process, of which multiple myeloma is the best choice. This diagnosis is also supported by the anemia noted on the patient’s history. Metastatic carcinoma and lymphoma also may have a similar presentation.
REFERENCE: Resnick D (ed): Diagnosis of Bone and Joint Disorders. Philadelphia, PA,

WB Saunders, 2002, pp 2189-2216.

Question 16

What structure is located at the tip of the arrow in Figure 18?

Explanation

DISCUSSION: The structure shown is the exiting nerve root at the L3-4 disk, which is the right L3 root.
REFERENCE: An H: Diagnostic imaging of the spine, in Principles and Techniques of Spine Surgery. Baltimore, MD, Lippincott Williams & Wilkins, 1998, pp 102-125.

Question 17

What structure is located at the tip of the arrow in Figure 18?

Explanation

DISCUSSION: The structure shown is the exiting nerve root at the L3-4 disk, which is the right L3 root.
REFERENCE: An H: Diagnostic imaging of the spine, in Principles and Techniques of Spine Surgery. Baltimore, MD, Lippincott Williams & Wilkins, 1998, pp 102-125.

Question 18

A patient undergoes the procedure shown in Figure 19. An important part of this procedure is preservation of what wrist ligament?

Explanation

DISCUSSION: Proximal row carpectomy is a salvage wrist procedure that yields a surprisingly stable construct. This has been attributed to two factors: 1) the congruency of the head of the capitate in the lunate fossa (this articulation is less congruent than the native lunate/lunate fossa relationship, but surprisingly stable), and 2) preservation of the radioscaphocapitate ligament, the most radial of the palmar extrinsic ligaments, which prevents ulnar subluxation after proximal row carpectomy.
REFERENCE: Jebson PJ, Engber WD: Proximal row carpectomy. Tech Hand Up Extrem Surg 1999;3:32-36.

Question 19

A 23-year-old woman reports right knee pain and fullness. The pain is worse with activity but also present at rest. Radiographs are shown in Figures 20a and 20b. What is the most likely diagnosis?

Explanation

DISCUSSION: The radiographs reveal a predominantly lytic, destructive lesion of the distal femur, although there is a hint of some blastic change as well. The lesion has violated the cortex, and there is mineralization outside the cortex laterally. The lateral radiograph suggests a soft-tissue density. These aggressive changes on radiographs in this age group are strongly suggestive of osteosarcoma.
REFERENCES: Sanders TG, Parsons TW: Radiographic imaging of musculoskeletal neoplasia. Cancer Control 2001;8:221-231.
Menendez LR (ed): Orthopaedic Knowledge Update: Musculoskeletal Tumors. Rosemont, IL, American Academy of Orthopaedic Surgeons, 2002, pp 175-186.

Question 20

What is the structure indicated by the letter “A” in Figure 21?

Explanation

DISCUSSION: The ligaments shown are the components of the lateral collateral ligament complex, and the structure indicated by the letter “A” is the radial collateral ligament. The lateral ulnar collateral ligament is the structure indicated by the letter “C” and the annular ligament is indicated by the letter “B.” The transverse ligament is a component of the medial collateral ligament complex.
REFERENCES: Morrey BF: Anatomy of the elbow joint, in Morrey BF (ed): The Elbow and Its Disorders. Philadelphia, PA, WB Saunders, 1993, p 30.
O’Driscoll SW, Bell DF, Morrey BF: Posterolateral rotatory instability of the elbow. J Bone Joint Surg Am 1991;73:440-446.

Question 21

A 16-year-old boy sustains a twisting injury to the left knee while wrestling. MRI scans are shown in Figures 22a through 22c. What is the most likely diagnosis?

Explanation

DISCUSSION: The MRI scans show a displaced bucket-handle medial meniscus tear that can be visualized on coronal, sagittal, and axial views. The sagittal view shows the typical “double posterior cruciate ligament sign,” in which the low-signal bucket-handle fragment parallels the normal low-signal posterior cruciate ligament. The coronal and axial images both show the displaced medial meniscus in the notch.
REFERENCES: Sanders TG, Miller MD: A systematic approach to magnetic resonance imaging interpretation of sports medicine injuries of the knee. Am J Sports Med 2005;33:131-148.
Miller TT: Magnetic resonance imaging of the knee, in Insall JN, Scott WN (eds): Surgery of the Knee, ed 4. Philadelphia, PA, Churchill Livingstone, 2006, vol 1, pp 201-224.

Question 22

A 48-year-old woman reports bilateral thigh pain that is limiting her function as a librarian. A radiograph and a bone scan are shown in Figures 23a and 23b. What is the most likely diagnosis?

Explanation

DISCUSSION: The radiograph reveals bilateral severe acetabular protrusio. The bone scan and history confirm involvement of multiple joints, including the knees and the hindfoot. Although the first four choices can all cause the acetabular protrusio, the associated multiple joint involvement suggests the diagnosis of rheumatoid arthritis. Arthrokatadysis, or primary protrusio acetabuli, is often associated with osteomalacia but not other joint disease. Developmental dysplasia is a common cause of bilateral hip pathology but does not have acetabular protrusio.
REFERENCES: Resnick D: Diagnosis of Bone and Joint Disorders, ed 3. Philadelphia, PA,

WB Saunders, 1995, pp 956-957.
Wheeless’ Textbook of Orthopaedics: Acetabular Protrusio. www.wheelessonline.com/ortho/acetabular_protrusio

Question 23

At the level of tibial bone resection in total knee arthroplasty, where does the common peroneal nerve lie?

Explanation

DISCUSSION: At the level of tibial bone resection in total knee arthroplasty, the common peroneal nerve lies superficial to the lateral head of the gastrocnemius and is therefore protected by this structure. In an MRI study of 60 knees, the mean distance from the bony posterolateral corner of the tibia to the nerve was 1.49 cm, with no distance less than 0.9 cm. The distance from the bone to nerve was greater in larger legs.
REFERENCES: Clarke HD, Schwartz JB, Math KR, et al: Anatomic risk of peroneal nerve injury with the “pie crust” technique for valgus release in total knee arthroplasty. J Arthroplasty 2004;19:40-44.
Anderson JE: Grant’s Atlas of Anatomy, ed 7. Baltimore, MD, Lippincott Williams & Wilkins, 1978, pp 4-52, 4-53.

Question 24

Figures 24a through 24c show the coronal T 1 -weighted, T 2 -weighted fat-saturated, and T 1 -weighted fat-saturated gadolinium MRI scans of the proximal thigh of a 52-year-old woman who reports a mass in the medial thigh and groin area. She notes that the fullness has grown in size over the course of many months. Based on these findings, what is the most likely diagnosis?

Explanation

DISCUSSION: The images show a complex, lobular lesion of the thigh that has signal characteristics that follow fat. The size of the lesion, the areas of stranding within the mass, along with mild uptake on the gadolinium sequences and the mild edema within the lesion on the T₂-weighted image make liposarcoma the most likely diagnosis and simple intramuscular lipoma far less likely. All other diagnoses listed would not follow fat characteristics shown on the MRI sequences.
REFERENCE: Sanders TG, Parsons TW: Radiographic imaging of musculoskeletal neoplasia. Cancer Control 2001;8:221-231.

Question 25

The arrows in the axial T 1 -weighted MRI scan shown in Figure 25 show which of the following structures?

Explanation

DISCUSSION: The arrows in the figure show the deep branch of the ulnar nerve (more radial) and the superficial branch of the ulnar nerve within Guyon’s canal. Guyon’s canal is approximately 4 cm long beginning at the proximal extent of the transverse carpal ligament and ends at the aponeurotic arch of the hypothenar muscles. Many structures comprise the boundaries of Guyon’s canal. The floor, for example, consists of the transverse carpal ligament, the pisohamate and pisometacarpal ligaments, and the opponens digiti minimi. Within Guyon’s canal, the ulnar nerve bifurcates into the superficial and deep branches. The ulnar artery is immediately adjacent and radial to the ulnar nerve. The median nerve is visualized within the carpal tunnel, and the palmar cutaneous branch is more radial to Guyon’s canal and volar to the carpal tunnel. The radial and ulnar digital nerves to the little finger are branches off of the superficial branch of the ulnar nerve distal to its emergence from Guyon’s canal. The ulnar artery is the round structure located radial to the branches of the ulnar nerve within Guyon’s canal. Adjacent to the ulnar artery are two small veins. The dorsal cutaneous branch of the ulnar nerve branches from the ulnar nerve in the distal forearm, well proximal to Guyon’s canal. The common digital artery to the fourth web branches from the superficial palmar arch distal to Guyon’s canal. The hook of the hamate is clearly seen in the figure, orienting the observer to the ulnar side of the wrist.
REFERENCES: Gross MS, Gelberman RH: The anatomy of the distal ulnar tunnel. Clin Orthop Relat Res 1985;196:238-247.
Denman EE: The anatomy of the space of Guyon. The Hand 1978;10:69-76.

Question 26

An 82-year-old man has had episodic right thigh pain after undergoing a total hip arthroplasty 10 years ago. Initial postoperative radiographs are shown in Figures 26a and 26b, and current radiographs are shown in Figures 26c and 26d. What is the most likely cause of his pain?

Explanation

DISCUSSION: These radiographs are dominated by the subsidence of the femoral component. There is also evidence of polyethylene wear and femoral osteolysis in the region of the greater trochanter. There is no evidence of proximal (calcar) stress shielding, and there is a thick distal pedestal. Engh and associates defined two major signs of osseointegration - the absence of radiolucent lines around the porous-surfaced portion of the implant and new bone bridging the gap between the endosteal surface and the porous portion of the implant. Implant migration indicates failure of ingrowth. Osteolysis is a periprosthetic loss of bone secondary to particulate debris and it is often clinically silent unless it is accompanied by pathologic fracture. It is often globular. Acetabular loosening is based on radiolucent lines and implant migration. The current radiographs demonstrate subsidence of the stem with pedestal formation.
REFERENCES: Engh CA, Massin P, Suthers KE: Roentgenographic assessment of biologic fixation of porous-surface femoral components. Clin Orthop Relat Res 1990;257:107-128.
Engh CA, Hooten JP, Zettl-Schaffer KF, et al: Evaluation of bone ingrowth in proximally and extensively porous-coated anatomic medullary locking prostheses retrieved at autopsy. J Bone Joint Surg Am 1995;77:903-910.

Question 27

A 37-year-old patient with type I diabetes mellitus has a flexor tenosynovitis of the thumb flexor tendon sheath following a kitchen knife puncture wound to the volar aspect of the thumb. Left unattended, this infection will likely first spread proximally creating an abscess in which of the following spaces of the palm?

Explanation

DISCUSSION: Flexor tenosynovitis of the thumb flexor tendon sheath can spread proximally and form an abscess within the thenar space of the palm. The flexor pollicis longus tendon does not pass through the central space of the palm or the hypothenar space of the palm. The flexor pollicis longus tendon does pass through the carpal tunnel, but this is not a palmar space. The three palmar spaces include the hypothenar space, the thenar space, and the central space. The posterior adductor space would likely only be involved secondarily after spread from a thenar space infection.
REFERENCES: Hollinshead W: Anatomy for Surgeons: The Back and Limbs, ed 3. Philadelphia, PA, Harper and Row, 1982, vol 3, pp 478-479.
Lee D, Ferlic R, Neviaser R: Hand infections, in Berger R, Weiss AP (eds): Hand Surgery. Philadelphia, PA, Lippincott Williams & Wilkins, 2004, pp 1784-1785.

Question 28

What tendon is closest to an appropriately placed anterolateral portal for ankle arthroscopy?

Explanation

DISCUSSION: The appropriate placement of the anterolateral portal provides access to the lateral gutter of the joint while avoiding the superficial peroneal nerve. The safest location for the portal is approximately 4 mm lateral to the peroneus tertius tendon, the closest of the tendons listed to the anterolateral portal. Because the superficial peroneal nerve location is variable, attempts to visualize, palpate, or transilluminate the nerve are mandatory.
REFERENCE: Ogut T, Akgun I, Kesmezacar H, et al: Navigation for ankle arthroscopy: Anatomical study of the anterolateral portal with reference to the superficial peroneal nerve. Surg Radiol Anat 2004;26:268-274.

Question 29

A 52-year-old woman reports nagging shoulder pain that has been present for months and is slowly progressive in nature. The patient also reports nocturnal pain and notes that the pain is not activity related. Figures 27a and 27b show the radiograph and bone scan, and Figures 27c through 27e show T 1 -weighted, T 2 -weighted, and gadolinium MRI scans, respectively. Based on these findings, what is the most likely diagnosis?

Explanation

DISCUSSION: The radiograph reveals a metaphyseal lesion with some stippled mineralization suggesting a chondroid tumor. The bone scan shows increased uptake, beyond what is expected for a simple enchondroma, and beyond the limits of the lesion. The MRI sequences shows a lobular lesion on the T₁- and T₂-weighted (bright on the T₂ sequence) images with inhomogeneous uptake of gadolinium; both findings are typical for a chondroid lesion. The history of pain, the positive bone scan, the age of the patient, the size of the lesion, and the central location (enostotic) of the lesion all suggest a malignant cartilage tumor. The images are not consistent with the other diagnoses. In particular, plasmacytoma is more uniformly bright on T₂-weighted images and often has a negative bone scan.
REFERENCES: Menendez LR (ed): Orthopaedic Knowledge Update: Musculoskeletal Tumors. Rosemont, IL, American Academy of Orthopaedic Surgeons, 2002, pp 187-194.
Resnick D (ed): Diagnosis of Bone and Joint Disorders. Philadelphia, PA, WB Saunders, 2002, pp 3897-3904.

Question 30

Figure 28 shows an arthroscopic view of a right shoulder in the lateral position through a posterior portal. What is the area between structure B (biceps) and SS (subscapularis tendon)?

Explanation

DISCUSSION: The rotator cuff interval is located between the supraspinatus and subscapularis and the biceps tendon is deep to the interval. It is a triangular area where the base is the coracoid process and the apex is the transverse humeral ligament at the biceps sulcus. Closure or tightening of this area is often helpful in patients with shoulder instability. Conversely, this area is often contracted in patients with adhesive capsulitis and may need to be released.
REFERENCES: Selecky MT, Tibone JE, Yang BY, et al: Glenohumeral joint translation after arthroscopic thermal capsuloplasty of the rotator interval. J Shoulder Elbow Surg 2003;12:139-143.
Harryman DT, Sidles JA, Harris SL, et al: The role of the rotator interval capsule in passive motion and stability of the shoulder. J Bone Joint Surg Am 1992;74:53-66.

Question 31

New painful paresthesias near the site of the incision after an ulnar nerve transposition is the result of injury to what nerve?

Explanation

DISCUSSION: Branches of the medial antebrachial cutaneous nerve can often be identified during routine ulnar nerve surgery crossing the medial aspect of the elbow. It should be preserved to avoid development of painful paresthesias.
REFERENCE: Dellon AL, Mackinnon SE: Injury to the medial antebrachial cutaneous nerve during cubital tunnel surgery. J Hand Surg Br 1985;10:33-36.

Question 32

A 23-year-old man reports pain on the superior aspect of his right shoulder with repetitive overhead activities and when lying on his right side. Figure 29 shows an axial MRI scan. What is the most likely diagnosis based on the MRI findings?

Explanation

DISCUSSION: Os acromiale represents a failure of fusion of the anterior acromial apophysis and has been reported in approximately 8% of the population. Patients with a symptomatic os acromiale often report impingement-type symptoms with pain over the superior acromion, especially with overhead activities or sleeping. When nonsurgical management is unsuccessful, surgical options include excision, open reduction and internal fixation, and arthroscopic decompression.
REFERENCES: Kurtz CA, Humble BJ, Rodosky MW, et al: Symptomatic os acromiale. J Am Acad Orthop Surg 2006;14:12-19.
Ortiguera CJ, Buss DD: Surgical management of the symptomatic os acromiale. J Shoulder Elbow Surg 2002;11:521-528.

Question 33

Following a chevron bunionectomy performed through a dorsal approach, a patient has persistent numbness on the dorsal and medial aspect of the hallux. What nerve has most likely been injured?

Explanation

DISCUSSION: The dorsomedial cutaneous nerve of the hallux, which is a distal branch of the superficial peroneal nerve, supplies sensation to the skin on the dorsal and medial half of the hallux and may be injured during a chevron bunionectomy. Injury to the nerve leads to particularly painful neuromas that directly impinge on the shoe. For this reason, direct medial approaches are typically preferred for access to the medial aspect of the metatarsophalangeal joint.
REFERENCE: Miller SD: Dorsomedial cutaneous nerve syndrome: Treatment with nerve transection and burial into bone. Foot Ankle Int 2001;22:198-202.

Question 34

A 74-year-old man reports progressive left hip pain with weight-bearing activities. A radiograph is shown in Figure 30. What is the most likely underlying diagnosis?

Explanation

DISCUSSION: The radiograph shows enlargement of the bone, coarse trabeculation, a blastic appearance, and thickening of the cortex, revealing the classic appearance of Paget’s disease in the sclerotic phase, the most common presentation. While lymphoma may present as a blastic lesion, it will not have the same enlargement, coarse trabeculation of bone, and the significant sclerosis seen here.
REFERENCES: Menendez LR (ed): Orthopaedic Knowledge Update: Musculoskeletal Tumors. Rosemont, IL, American Academy of Orthopaedic Surgeons, 2002, pp 211-215.
Resnick D (ed): Diagnosis of Bone and Joint Disorders. Philadelphia, PA, WB Saunders, 2002, pp 1947-2000.

Question 35

The anatomy of the sciatic nerve as it exits the pelvis is best described as exiting through the

Explanation

DISCUSSION: The sciatic nerve is formed by the roots of the lumbosacral plexus. It exits the pelvis through the greater sciatic notch and appears in the buttock anterior to the piriformus. From that point, the sciatic nerve passes posteriorly over the superior gemellus, obturator internus, inferior gemellus, and quadratus femoris before it passes deep to the biceps femoris. The tendon of the obturator internus passes through the lesser sciatic notch.
REFERENCES: Hoppenfeld S, deBoer P: Surgical Exposures in Orthopaedics: The Anatomic Approach. Philadelphia, PA, JB Lippincott, 1984, p 347.
Anderson JE: Grant’s Atlas of Anatomy, ed 7. Baltimore, MD, Lippincott Williams & Wilkins, 1978, pp 4-34, 4-36.
Hollingshead WH: Anatomy for Surgeons: The Back and Limbs, ed 2. Hagerstown, MD, Harper & Row, 1969, pp 607-609.

Question 36

What complication is more likely following excessive medial retraction of the anterior covering structures during the anterolateral (Watson-Jones) approach to the hip?

Explanation

DISCUSSION: The femoral nerve is the most lateral structure in the anterior neurovascular bundle. The femoral artery and vein lie medial to the nerve. Retractors placed in the anterior acetabular lip should be safe, although neurapraxia of the femoral nerve may occur if retraction is prolonged or forceful leading to quadriceps weakness. The femoral artery and nerve are well protected by the interposed psoas muscle. Damage to the lateral femoral cutaneous nerve, causing numbness over the anterolateral thigh, can occur while developing the interval between the tensor fascia latae and sartorious in the anterior (Smith-Petersen) approach but less likely in the Watson-Jones approach. Superior gluteal injury and accompanying abductor insufficiency may occur during excessive splitting of the glutei during the direct lateral (Hardinge) approach. Foot drop secondary to sciatic injury is more common with a posterior exposure or posterior retractor placement.
REFERENCES: Hoppenfeld S, deBoer P: Surgical Exposures in Orthopaedics: The Anatomic Approach. Philadelphia, PA, JB Lippincott, 1984, p 325.
Anderson JE: Grant’s Atlas of Anatomy, ed 7. Baltimore, MD, Lippincott Williams & Wilkins, 1978, pp 4-17, 4-18.

Question 37

In the most common condition causing a winged scapula, which of the following nerves is affected?

Explanation

DISCUSSION: A winged scapula is most often associated with Parsonage-Turner syndrome, a condition thought to be due to an inflammatory or immune-mediated mechanism. Certain muscles are predisposed, particularly the serratus anterior muscle innervated by the long thoracic nerve. Other less common nerve lesions (eg, the spinal accessory and dorsal scapular nerves) may also cause winged scapulae.
REFERENCES: Kline DG, Hudson AR: Nerve Injuries: Operative Results for Major Nerve Injuries, Entrapments and Tumors. Philadelphia, PA, WB Saunders, 1995.
van Alfen N, van Engelen BG: The clinical spectrum of neuralgic amyotrophy in 246 cases. Brain 2006;129:438-450.

Question 38

A 17-year-old woman seen in the emergency department reports right knee pain and swelling that has progressively worsened over the past several weeks. Radiographs are shown in Figures 31a and 31b. What is the most likely diagnosis?

Explanation

DISCUSSION: The radiographs reveal a blastic lesion of the proximal tibial metaphysis with cortical destruction, mineralization extending into the soft tissue laterally, indistinct margins, and destruction of the normal trabecular pattern. In this age group, with this aggressive appearance, osteosarcoma is the most likely diagnosis. Chondroblastoma and giant cell tumor are generally geographic and lytic. Chondrosarcoma is rare in this age group and would likely be a secondary lesion from an underlying chondroid tumor that is not present here. Whereas infection can have a wide variety of appearances, it tends to be more lytic in the acute presentation.
REFERENCES: Sanders TG, Parsons TW: Radiographic imaging of musculoskeletal neoplasia. Cancer Control 2001;8:221-231.
Menendez LR (ed): Orthopaedic Knowledge Update: Musculoskeletal Tumors. Rosemont, IL, American Academy of Orthopaedic Surgeons, 2002, pp 175-186.

Question 39

A 26-year-old man has had hand pain and progressive swelling in the knuckle for the past several months. He denies any trauma to the hand. The ring finger metacarpophalangeal joint is tender, and there is loss of motion in the digit. Figure 32a shows the radiograph and Figures 32b through 32d show the T 1 -weighted, T 2 -weighted, and gadolinium MRI scans, respectively. What is the most likely diagnosis?

Explanation

DISCUSSION: The radiograph reveals a subchondral lesion in the metacarpophalangeal joint that is lytic and expansile. The MRI scans show a mass that is moderate in intensity on the

T₂-weighted image and has some gadolinium uptake. There are no cystic components in this lesion. The subchondral location and expansile nature are highly suggestive of giant cell tumor of bone. A lesion with this appearance might also represent an aneurysmal bone cyst, given the amount of expansion present.
REFERENCES: Menendez LR (ed): Orthopaedic Knowledge Update: Musculoskeletal Tumors. Rosemont, IL, American Academy of Orthopaedic Surgeons, 2002, pp 113-118.
Parsons TW: Benign bone tumors, in Fitzgerald R Jr, Kaufer H, Malkani A (eds): Orthopaedics. Philadelphia, PA, Mosby International, 2002, pp 1027-1035.

Question 40

Which of the following best describes the relationship of the median nerve to the flexor carpi radialis tendon just proximal to the carpal canal?

Explanation

DISCUSSION: The median nerve has an intimate association with the palmaris longus and the flexor carpi radialis at the proximal aspect of the carpal canal. The median nerve lies just ulnar and dorsal to the flexor carpi radialis tendon.
REFERENCES: Hoppenfeld S, deBoer P: Surgical Exposures in Orthopaedics, ed 2. Philadelphia, PA, Lippincott-Raven, 1994, pp 118-131.
Henry A: Extensile Exposure, ed 3. Edinburgh, UK, Churchill Livingstone, 1995, pp 100-107.

Question 41

Which of the following muscles has dual innervation?

Explanation

DISCUSSION: The brachialis muscle typically receives dual innervation. The major portion is innervated by the musculocutaneous nerve. Its inferolateral portion is innervated by the radial nerve. The others listed have single innervation. The anterior approach to the humerus, which requires splitting of the brachialis, capitalizes on this dual innervation.
REFERENCE: Mahakkanukrauh P, Somsarp V: Dual innervation of the brachialis muscle.

Clin Anat 2002;15:206-209.

Question 42

Figure 33a shows a line drawing of a normal hemipelvis. The anterior acetabular rim is bold. Figure 33b illustrates a hemipelvis with a crossover sign, which is indicative of what acetabular pathology?

Explanation

DISCUSSION: In a normal AP pelvis radiograph, the anterior rim of the acetabulum runs medially and distally, diverging from the posterior rim which runs much more vertically. In excessive acetabular retroversion, the anterior rim (bold line in Figure 33b) and posterior rim start laterally, and as these lines progress medially and distally, the anterior line crosses the posterior line. This predisposes to femoral acetabular impingement.
REFERENCES: Reynolds D, Lucas J, Klaue K: Retroversion of the acetabulum: A cause of hip pain. J Bone Joint Surg Br 1999;81:281-288.
Espinosa N, Rothenfluh DA, Beck M, et al: Treatment of femoro-acetabular impingement: Preliminary results of labral refixation. J Bone Joint Surg Am 2006;88:925-935.

Question 43

Which of the following structures is most vulnerable during a medial sesamoidectomy of the hallux?

Explanation

DISCUSSION: The plantar-medial cutaneous nerve is at risk with the surgical approach to the medial sesamoid. It is found directly underlying an incision made at the junction of the glabrous skin of the hallux and must be identified before the approach can proceed. Transection will result in a painful neuroma that impinges on the plantar-medial surface of the toe and cause problems with shoe wear. The only other structure that lies near the surgical field is the abductor hallucis tendon which lies dorsal to the incision.
REFERENCE: Sarrafian SK: Anatomy of the Foot and Ankle, Descriptive, Topographic, Functional, ed 2. Philadelphia, PA, JB Lippincott, 1993, p 377.

Question 44

What structure is most at risk for injury from a retractor against the tracheoesophageal junction during an anterior approach to the cervical spine?

Explanation

DISCUSSION: Although any of these structures can be injured by pressure from the medial blade of a self-retaining retractor, the recurrent laryngeal nerve runs cephalad in the interval between the esophagus and trachea and is vulnerable to pressure if caught between the retractor and an inflated endotracheal tube balloon.
REFERENCES: Ebraheim NA, Lu J, Skie M, et al: Vulnerability of the recurrent laryngeal nerve in the anterior approach to the lower cervical spine. Spine 1997;22:2664-2667.
Kilburg C, Sullivan HG, Mathiason MA: Effect of approach side during anterior cervical discectomy and fusion on the incidence of recurrent laryngeal nerve injury. J Neurosurg Spine 2006;4:273-277.

Question 45

A 40-year-old man has had hip pain with increased activity over the past year. Examination reveals restriction of motion and tenderness with combined hip flexion, adduction, and internal rotation. An AP radiograph is shown in Figure 34. What is the most likely diagnosis?

Explanation

DISCUSSION: Femoral acetabular impingement (FAI) is a pathologic entity leading to pain, reduced range of motion in flexion and internal rotation, and development of secondary arthritis of the hip. There are two types of FAI: cam impingement and pincher impingement. Cam impingement is seen when a nonspherical femoral head produces a cam effect when the prominent portion to the femoral head rotates into the joint. This mechanism produces shear forces that damage articular cartilage. Radiographs reveal early joint degeneration and flattening of the head neck junction (the so-called “pistol grip deformity”) as seen in this image. The pincher type of impingement involves abnormal contact between the femoral head neck junction and the acetabulum, in the presence of a spherical femoral head.
REFERENCES: Beall DP, Sweet CF, Martin HD, et al: Imaging findings of femoraoacetabular impingement syndrome. Skeletal Radiol 2005;34:691-701.
Mardones RM, Gonzalez C, Chen Q, et al: Surgical treatment of femoroacetabular impingement: Evaluation of the effect of the size of the resection. J Bone Joint Surg Am 2006;88:84-91.

Question 46

Figure 35 shows the radiograph of a 44-year-old woman with rheumatoid arthritis who reports neck pain. Below what threshold number is surgical stabilization warranted for the interval shown by the arrow?

Explanation

DISCUSSION: The posterior atlanto-dens interval represents the space available for the spinal cord and a distance of less than 14 mm is predictive of neurologic progression, thus warranting consideration for fusion, even in the absence of symptoms.
REFERENCE: Boden SD, Dodge LD, Bohlman HH, et al: Rheumatoid arthritis of the cervical spine: A long-term analysis with predictors of paralysis and recovery. J Bone Joint Surg Am 1993;75:1282-1297.

Question 47

An axillary nerve lesion may cause weakness in the deltoid and the

Explanation

DISCUSSION: While the most prominent functional deficit from axillary nerve lesions occurs from denervation of the deltoid, denervation of the teres minor also occurs.
REFERENCE: Hollinshead WH: Anatomy for Surgeons: The Back and Limbs. New York, NY, Harper & Row, 1969.

Question 48

Figure 36 shows an AP radiograph of a 65-year-old man who reports activity-related groin pain. History reveals that he underwent total hip arthroplasty 12 years ago. What is the most likely diagnosis?

Explanation

DISCUSSION: The AP radiograph demonstrates extensive periacetabular osteolysis. The central hole eliminator has dissociated from the shell and migrated into a lytic defect in the ischium. In a retrieval study, most periacetabular osteolytic lesions had a clear communication pathway with the joint space. Lesions with communication to the joint via several pathways or through a central dome hole (as in this patient) were larger and more likely to be associated with cortical erosion. Although periprosthetic tumors have been described, they are rare and particle-induced inflammation around a prosthesis does not seem to increase the risk for carcinogenesis.
REFERENCES: Visuri T, Pulkkinen P, Paavolainen P: Malignant tumors at the site of total hip prosthesis: Analytic review of 46 cases. J Arthroplasty 2006;21:311-323.
Bezwada HP, Shah AR, Zambito K, et al: Distal femoral allograft reconstruction for massive osteolytic bone loss in revision total knee arthroplasty. J Arthroplasty 2006;21:242-248.
Kitamura N, Naudie DD, Leung SB, et al: Diagnostic features of pelvic osteolysis on computed tomography: The importance of communication pathways. J Bone Joint Surg Am 2005;87:1542-1550.

Question 49

A 21-year-old man who was injured in a snowboarding accident 18 months ago now reports wrist pain. An MRI scan is shown in Figure 37. Based on the image findings, what is the most likely diagnosis?

Explanation

DISCUSSION: The coronal MRI scan of the wrist shows the scaphoid. There is a subtle fracture line with a step-off at the radial surface consistent with a nonunion. The signal intensity is markedly different between the two fragments of the scaphoid. This strongly suggests osteonecrosis. Preiser’s disease is osteonecrosis typically involving most or all of the scaphoid. Kienbock’s disease involves the lunate. Intraosseous ganglia are easily diagnosed on MRI but typically have a fluid-filled area surrounded by denser bone in the periphery. Scapholunate dissociation can be seen on MRI as an injury to the scapholunate ligament and widening of the scapholunate interval, neither of which is seen on this image.
REFERENCE: Perlik PC, Guilford WB: Magnetic resonance imaging to assess vascularity of scaphoid nonunions. J Hand Surg Am 1991;16:479-484.

Question 50

An 82-year-old woman reports activity-related knee pain. History reveals that she underwent total knee arthroplasty 16 years ago. AP and lateral radiographs and a bone scan are shown in Figures 38a through 38c. What is the most likely diagnosis?

Explanation

DISCUSSION: The radiographs reveal a large femoral metaphyseal lytic lesion with

well-defined borders. Joint space narrowing medially is consistent with polyethylene wear.

The most likely diagnosis is particle-mediated osteolysis. Metastatic tumors and primary sarcomas adjacent to an arthroplasty are extremely rare. In addition, malignant tumors and infection would more likely reveal a destructive lesion with poorly defined borders and increased uptake on a bone scan. Stress shielding with massive bone loss has not been described in knee arthroplasty literature, although this entity has been observed in fully porous-coated femoral implants in total hip arthroplasty.
REFERENCES: Robinson EJ, Mulliken BD, Bourne RB, et al: Catastrophic osteolysis in total knee replacement: A report of 17 cases. Clin Orthop Relat Res 1995;321:98-105.
Archibeck MJ, Jacobs JJ, Roebuck KA, et al: The basic science of periprosthetic osteolysis. Instr Course Lect 2001;50:185-195.
Bugbee WD, Culpepper WJ, Engh CA Jr, et al: Long-term clinical consequences of stress-shielding after total hip arthroplasty without cement. J Bone Joint Surg Am 1997;79:1007-1012.

Question 51

A 28-year-old male sustains a high-energy Pauwels III (vertical shear) femoral neck fracture. Which of the following fixation constructs provides the highest biomechanical stability against the predominant deforming forces in this fracture pattern?

Explanation

Pauwels III femoral neck fractures (angle > 50 degrees) experience massive vertical shear forces. A sliding hip screw (SHS) provides superior biomechanical resistance to shear compared to cancellous screws, and adding a derotational screw controls the rotational instability inherent to the SHS.

Question 52

A 68-year-old female presents with complaints of instability and knee effusion 6 months after a posterior-stabilized total knee arthroplasty (TKA). Examination reveals a stable knee in full extension and 90 degrees of flexion, but marked laxity at 30 to 45 degrees of flexion. What is the most likely intraoperative technical error that caused this presentation?

Explanation

Mid-flexion instability in TKA is classically caused by joint line elevation. This occurs when excessive distal femoral resection is compensated by inserting a thicker polyethylene insert, which balances extension but leaves the mid-flexion arc loose.

Question 53

A 55-year-old male undergoes a total hip arthroplasty utilizing a ceramic-on-ceramic bearing surface. Two years postoperatively, he complains of a loud squeaking noise from the hip during specific movements. What is the most significant risk factor for this complication?

Explanation

Squeaking in ceramic-on-ceramic total hip arthroplasties is strongly associated with edge loading of the bearing surfaces. This most commonly results from acetabular component malposition, specifically excessive cup anteversion or vertical inclination.

Question 54

During a posteromedial approach to the tibia for open reduction and internal fixation of a Schatzker IV tibial plateau fracture, the dissection utilizes the interval between the medial head of the gastrocnemius and the pes anserinus. Which of the following structures is at greatest risk of iatrogenic injury during the superficial dissection?

Explanation

The posteromedial approach to the tibial plateau requires careful superficial dissection. The saphenous nerve and the great saphenous vein run superficially in this region and are at significant risk of injury during the surgical approach.

Question 55

A 40-year-old male is diagnosed with Ficat Stage II avascular necrosis of the femoral head. If non-operative management fails, preserving the native joint is dependent on the viability of the femoral head's blood supply. What is the primary arterial supply to the weight-bearing dome of the adult femoral head?

Explanation

The primary blood supply to the adult femoral head originates from the medial femoral circumflex artery (MFCA). Specifically, the deep branch of the MFCA supplies the superior, weight-bearing dome via the lateral epiphyseal arteries.

Question 56

A 22-year-old athlete presents with recurrent instability two years after an anterior cruciate ligament (ACL) reconstruction using a bone-patellar tendon-bone autograft. Imaging shows an intact but non-functional graft. What is the most common technical cause of ACL reconstruction failure?

Explanation

Non-anatomic tunnel placement is the most frequent technical error leading to ACL reconstruction failure. For example, placing the femoral tunnel too anteriorly results in a graft that is excessively tight in flexion and loose in extension, ultimately leading to stretching or rupture.

Question 57

A 35-year-old male sustains a Gustilo-Anderson IIIB open tibial shaft fracture following a motorcycle collision. After emergent debridement and external fixation, soft tissue coverage is required. Based on classic orthopedic trauma principles, soft tissue flap coverage should ideally be performed within what timeframe to minimize the risk of deep infection?

Explanation

Godina's classic study demonstrated that early soft tissue coverage (within 72 hours) for severe open tibia fractures significantly decreases the rates of deep infection and nonunion compared to delayed coverage.

Question 58

An 80-year-old female falls and sustains a periprosthetic femur fracture around a cemented total hip arthroplasty stem. Radiographs demonstrate a fracture at the tip of the stem. The stem is radiographically loose, but there is excellent surrounding proximal bone stock. How is this fracture classified, and what is the standard treatment?

Explanation

This is a Vancouver B2 fracture, characterized by a fracture around a loose stem in the presence of adequate bone stock. The standard of care is revision arthroplasty using a long cementless stem that bypasses the fracture site to achieve stable diaphyseal fixation.

Question 59

During the physical examination of a patient with a traumatic knee injury, the dial test reveals a 15-degree increase in external rotation on the injured side compared to the normal side when tested at 30 degrees of knee flexion. However, at 90 degrees of knee flexion, the external rotation is symmetric bilaterally. What is the correct diagnosis?

Explanation

A positive dial test (asymmetry of >10 degrees of external rotation) exclusively at 30 degrees of flexion indicates an isolated posterolateral corner (PLC) injury. If the test is positive at both 30 and 90 degrees, it suggests a combined PCL and PLC injury.

Question 60

A 45-year-old male undergoes open reduction and internal fixation of a displaced transverse patella fracture using a tension band wiring technique. Which biomechanical principle best explains the efficacy of this fixation method?

Explanation

Tension band wiring operates by placing the implant on the tension side (the anterior surface) of the patella. During knee flexion, it converts the distracting tensile forces of the extensor mechanism into dynamic compressive forces at the articular surface, promoting primary bone healing.

Question 61

A 24-year-old hockey player presents with groin pain exacerbated by hip flexion and internal rotation. Radiographs reveal a cam-type femoroacetabular impingement (FAI). Which of the following anatomic abnormalities is the primary driver of this specific type of impingement?

Explanation

Cam-type femoroacetabular impingement is caused by an aspherical femoral head with decreased head-neck offset, often quantified by an elevated alpha angle. Pincer-type FAI is typically caused by acetabular abnormalities such as overcoverage or retroversion.

Question 62

A 16-year-old female suffers an acute, traumatic lateral patellar dislocation. Which of the following soft-tissue structures is the primary restraint to lateral patellar translation at 0 to 20 degrees of knee flexion, and is nearly universally ruptured in this injury?

Explanation

The medial patellofemoral ligament (MPFL) provides approximately 50-60% of the restraint against lateral patellar displacement in early knee flexion (0 to 20 degrees). MPFL rupture is the essential pathologic lesion in an acute lateral patellar dislocation.

Question 63

In a 30-year-old patient with a displaced femoral neck fracture, which of the following biomechanical factors most significantly increases the risk of nonunion and fixation failure?

Explanation

A higher Pauwels angle indicates a more vertical fracture line, which translates to increased shear forces across the fracture site. This significantly increases the risk of varus collapse, nonunion, and fixation failure in young patients.

Question 64

When treating an intertrochanteric femur fracture with a sliding hip screw, maintaining a Tip-Apex Distance (TAD) of less than 25 mm is primarily associated with a decreased risk of which of the following complications?

Explanation

Baumgaertner et al. demonstrated that a Tip-Apex Distance (TAD) of less than 25 mm is the most important surgeon-controlled variable to prevent lag screw cut-out in the treatment of intertrochanteric fractures.

Question 65

During a posterior-stabilized total knee arthroplasty, the surgeon notes that the knee is well-balanced in extension but is overly tight in flexion. Which of the following is the most appropriate step to balance the knee?

Explanation

A knee that is tight in flexion but balanced in extension has a tight flexion gap. Downsizing the femoral component or increasing the posterior tibial slope will increase the flexion gap without altering the extension gap.

Question 66

A surgeon performs a total hip arthroplasty via the direct anterior approach. Which of the following internervous planes is utilized during the deep surgical dissection?

Explanation

The direct anterior approach to the hip utilizes the internervous plane between the tensor fasciae latae (supplied by the superior gluteal nerve) and the sartorius/rectus femoris (supplied by the femoral nerve).

Question 67

A 68-year-old woman presents with vague, aching thigh pain for 3 months. She has been taking alendronate for 8 years. Radiographs reveal focal lateral cortical thickening of the subtrochanteric femur with a transverse radiolucent line. What is the most appropriate prophylactic surgical management?

Explanation

Incomplete atypical femur fractures associated with long-term bisphosphonate use that are symptomatic (painful) should be treated with prophylactic cephalomedullary or intramedullary nailing to span the entire bone and prevent complete displacement.

Question 68

A 25-year-old man sustains a traumatic knee dislocation. Following closed reduction, his Ankle-Brachial Index (ABI) is measured at 0.85. What is the most appropriate next step in management?

Explanation

An ABI less than 0.9 in the setting of a knee dislocation is highly suspicious for a popliteal artery injury. The most appropriate next step is advanced vascular imaging, typically CT angiography, to localize and characterize the lesion.

Question 69

Which of the following is true regarding a Hoffa fracture (coronal shear fracture) of the distal femur?

Explanation

Hoffa fractures are coronal shear fractures that most commonly involve the lateral condyle and are highly associated with supracondylar femur fractures. They require open reduction and rigid internal fixation, typically with anterior-to-posterior lag screws.

Question 70

A 60-year-old man with a metal-on-metal total hip arthroplasty presents with groin pain and a palpable anterior mass. Aspiration yields thick, sterile fluid. What is the most likely histologic finding of the periarticular tissue?

Explanation

Adverse local tissue reaction (ALTR) or metallosis from metal-on-metal bearings is characterized histologically by an Aseptic Lymphocyte-Dominated Vasculitis-Associated Lesion (ALVAL), showing perivascular lymphocytic infiltration.

Question 71

During intramedullary nailing of a proximal third tibial shaft fracture, utilizing a standard infrapatellar entry portal most commonly leads to which of the following malalignments?

Explanation

Proximal third tibia fractures are notorious for displacing into valgus and procurvatum (apex anterior) during intramedullary nailing with a standard infrapatellar starting point, due to the pull of the patellar tendon and the eccentric starting point.

Question 72

A 72-year-old woman presents with acute onset of knee pain and swelling 3 weeks after a primary total knee arthroplasty. Aspiration reveals 65,000 WBCs/mcL with 95% neutrophils. What is the most appropriate surgical treatment?

Explanation

In the setting of an acute early periprosthetic joint infection (less than 4 weeks post-op) with well-fixed components, Open Debridement, Antibiotics, and Implant Retention (DAIR) with polyethylene exchange is the standard of care.

Question 73

A 35-year-old male sustains a posterior hip dislocation in a motor vehicle accident. Which of the following clinical presentations is most characteristic of this injury?

Explanation

A posterior hip dislocation characteristically presents with the affected lower extremity in a shortened, adducted, and internally rotated position. Anterior dislocations present shortened, abducted, and externally rotated.

Question 74

Which of the following is the most absolute indication for operative fixation of a closed patella fracture?

Explanation

The inability to perform a straight leg raise indicates a disruption of the extensor mechanism, which is an absolute indication for operative repair in patella fractures regardless of the degree of displacement.

Question 75

A 22-year-old man sustains a closed bilateral femoral shaft fracture. He undergoes reamed intramedullary nailing 12 hours after injury. On post-operative day 2, he develops petechiae, confusion, and hypoxia. What is the primary pathophysiologic mechanism of this syndrome?

Explanation

Fat Embolism Syndrome (FES) presents with the classic triad of hypoxia, neurologic abnormalities, and a petechial rash. It is caused by the release of marrow fat droplets into the venous circulation during trauma or intramedullary instrumentation.

Question 76

In the management of posterior wall acetabular fractures, which of the following radiographic findings is an absolute indication for open reduction and internal fixation?

Explanation

An intra-articular incarcerated fragment following reduction of a hip dislocation with a posterior wall fracture is an absolute indication for surgical intervention to prevent rapid joint destruction.

Question 77

During a medial parapatellar approach for a total knee arthroplasty, taking the arthrotomy too far distally and laterally risks injury to which of the following structures?

Explanation

Extending a medial parapatellar arthrotomy too distally and laterally on the tibial tubercle risks avulsing the patellar tendon insertion. The infrapatellar branch of the saphenous nerve is typically encountered more medially and is cut during the superficial approach.

Question 78

During an ilioinguinal approach to the acetabulum, the surgeon encounters massive bleeding over the superior pubic ramus near the symphysis. This bleeding is most likely originating from an anastomosis between which two vascular systems?

Explanation

The 'corona mortis' is a critical vascular anastomosis between the external iliac system (inferior epigastric artery/vein) and the internal iliac system (obturator artery/vein), located approximately 5 cm from the pubic symphysis.

Question 79

A 35-year-old male sustains a vertically oriented, displaced femoral neck fracture (Pauwels type III). Which of the following fixation constructs provides the most biomechanically stable fixation against vertical shear forces and varus collapse?

Explanation

For unstable, vertically oriented femoral neck fractures (Pauwels type III), a sliding hip screw with a derotation screw offers superior biomechanical stability against vertical shear and varus collapse compared to multiple cancellous screws.

Question 80

A 65-year-old woman presents with an audible and palpable "clunk" during active extension of her knee, 1 year after undergoing a posterior-stabilized total knee arthroplasty (TKA). What is the primary cause of this phenomenon?

Explanation

Patellar clunk syndrome occurs primarily in posterior-stabilized TKA designs when a fibrosynovial nodule forms at the superior pole of the patella. This nodule engages the intercondylar box in flexion and abruptly "clunks" out during active extension.

Question 81

A 45-year-old male sustains a high-energy Schatzker IV tibial plateau fracture featuring a displaced posteromedial shear fragment. Which surgical approach is most appropriate for direct visualization and buttress plating of this specific fragment?

Explanation

The posteromedial approach interval is between the pes anserinus tendons anteriorly and the medial head of the gastrocnemius posteriorly. It allows direct access to posteromedial shear fragments for optimal anti-glide or buttress plating.

Question 82

A patient experiences recurrent posterior dislocations following a primary total hip arthroplasty. Radiographs and a CT scan demonstrate the acetabular component is well-fixed but placed in 5 degrees of retroversion. Which of the following is the most appropriate definitive management?

Explanation

Recurrent posterior instability driven by acetabular retroversion requires correction of the underlying mechanical malposition. Revision of the well-fixed but malpositioned acetabular shell to appropriate anteversion is the definitive treatment.

Question 83

A 28-year-old male presents with an acutely swollen knee after a severe hyperextension injury. Examination reveals a positive Lachman, positive posterior drawer, and gross varus/valgus instability. His ankle-brachial index (ABI) is measured at 0.85. What is the most appropriate next step in management?

Explanation

An ABI less than 0.9 in the setting of a knee dislocation is highly suspicious for a vascular injury. CT angiography is the gold standard next step to precisely localize the popliteal artery lesion before surgical intervention.

Question 84

A 25-year-old male polytrauma patient sustains a comminuted femoral shaft fracture, bilateral flail chest, and severe pulmonary contusions. His serum lactate is 4.5 mmol/L and pH is 7.21 despite initial fluid resuscitation. What is the most appropriate initial management of the femur fracture?

Explanation

This patient is physiologically unstable (high lactate, acidosis) and falls into the "borderline" or "in extremis" category. Damage control orthopedics (DCO) with rapid application of a spanning external fixator is indicated to minimize the second hit of systemic inflammation.

Question 85

A 30-year-old male is involved in a motor vehicle collision and sustains a posterior hip dislocation associated with a femoral head fracture and a posterior wall acetabular fracture. According to the Pipkin classification, what type of injury is this?

Explanation

A Pipkin Type IV fracture is defined as a femoral head fracture associated with an acetabular fracture. Type I and II relate to the fovea, while Type III involves an associated femoral neck fracture.

Question 86

Following an anterior cruciate ligament (ACL) reconstruction using a bone-patellar tendon-bone autograft, a patient complains of a significant loss of knee flexion, though full extension is maintained. Which of the following technical errors is the most likely cause of this specific complication?

Explanation

An anteriorly placed femoral tunnel during ACL reconstruction results in a graft that becomes overly tight in flexion, causing a significant loss of knee flexion. Conversely, an anterior tibial tunnel typically restricts extension.

Question 87

When treating a stable intertrochanteric femur fracture with a sliding hip screw, which of the following radiographic parameters is most strongly predictive of lag screw cut-out?

Explanation

The Tip-Apex Distance (TAD) described by Baumgaertner is the most reliable predictor of lag screw cut-out. A TAD greater than 25 mm significantly increases the risk of fixation failure.

Question 88

An 82-year-old female presents with a displaced periprosthetic distal femur fracture (Lewis and Rorabeck Type II) above a well-fixed total knee arthroplasty. Review of operative records confirms the femoral component has a closed intercondylar box design. What is the most appropriate surgical management?

Explanation

The fracture is above a well-fixed TKA (Type II), meaning revision arthroplasty is unnecessary. Because the TKA has a closed intercondylar box, retrograde nailing is contraindicated, making lateral locked plating the gold standard.

OITE & ABOS Orthopedic Exam MCQs: Trauma, Foot & Knee Board Review Part 132

OITE & ABOS Orthopedic Board Review: Fracture, Hip, Knee MCQs Part 64

Key Takeaway

OITE & ABOS Orthopedic Board Review: Fracture, Hip, Knee MCQs Part 64

Chapter Index