Full Question & Answer Text (for Search Engines)
Question 1:
A 13-year-old male presents with right knee pain and an antalgic gait. Physical exam reveals obligatory external rotation with hip flexion. Radiographs demonstrate posterior and inferior slippage of the right proximal femoral epiphysis. Which of the following is considered a definitive indication for prophylactic in-situ pinning of the contralateral asymptomatic hip in this condition?
Options:
- Male sex
- Endocrine disorder such as hypothyroidism
- Slip angle greater than 50 degrees
- Age greater than 14 years
- Duration of symptoms less than 3 weeks
Correct Answer: Endocrine disorder such as hypothyroidism
Explanation:
Slipped Capital Femoral Epiphysis (SCFE) frequently occurs bilaterally. Prophylactic pinning of the contralateral hip is indicated in patients with underlying endocrinopathies (e.g., hypothyroidism, renal osteodystrophy) or in very young patients (under 10 years old), due to the exceptionally high risk of bilateral involvement in these cohorts.
Question 2:
During an anterior intrapelvic (modified Stoppa) approach for an acetabular fracture, significant hemorrhage is encountered from a vascular anastomosis over the superior pubic ramus. This structure represents an anastomosis between which two vascular systems?
Options:
- External iliac artery and internal iliac artery
- External iliac artery and superior gluteal artery
- Internal pudendal artery and obturator artery
- Inferior epigastric artery and obturator artery
- Superior gluteal artery and obturator artery
Correct Answer: Inferior epigastric artery and obturator artery
Explanation:
The corona mortis ('crown of death') is a highly variable vascular anastomosis between the obturator and external iliac systems. Most commonly, it connects the inferior epigastric artery or vein (branches of the external iliac system) to the obturator artery or vein (branches of the internal iliac system). It is typically located 5-6 cm from the pubic symphysis along the superior pubic ramus.
Question 3:
A 65-year-old female with a history of primary total hip arthroplasty (metal-on-polyethylene) 8 years ago presents with new-onset groin pain. Radiographs show a well-fixed stem and cup with no osteolysis. A joint aspiration yields fluid with a normal cell count but elevated cobalt and chromium ions. MRI demonstrates a solid periprosthetic soft-tissue mass. What is the most likely pathophysiologic mechanism for this presentation?
Options:
- Polyethylene wear debris inducing macrophage activation
- Mechanically assisted crevice corrosion at the head-neck junction
- Third-body wear from retained PMMA cement
- Galvanic corrosion between the titanium stem and cobalt-chromium shell
- Delayed low-virulence infection by Cutibacterium acnes
Correct Answer: Mechanically assisted crevice corrosion at the head-neck junction
Explanation:
The scenario describes trunnionosis, which is mechanically assisted crevice corrosion at the modular head-neck junction (the trunnion). Even in metal-on-polyethylene bearings, fretting and crevice corrosion at this modular interface can generate metal ions (elevated cobalt and chromium) and debris, leading to an adverse local tissue reaction (ALTR) or pseudotumor.
Question 4:
A 55-year-old male of East Asian descent presents with progressive clumsiness in his hands and a broad-based gait. Lateral cervical spine radiographs show a continuous line of ossification posterior to the vertebral bodies from C3 to C6. Which genetic factor or pathway is most strongly associated with the pathogenesis of this condition?
Options:
- Mutation in the COL1A1 gene
- HLA-B27 antigen
- Runx2/Cbfa1 upregulation
- Mutation in the FGFR3 gene
- t(X;18) translocation
Correct Answer: Runx2/Cbfa1 upregulation
Explanation:
Ossification of the posterior longitudinal ligament (OPLL) involves ectopic bone formation and is prevalent in East Asian populations. Genetic studies show a strong association with the upregulation of osteogenic genes such as Runx2/Cbfa1, as well as bone morphogenetic proteins (BMPs) and TGF-beta. HLA-B27 is associated with ankylosing spondylitis, COL1A1 with osteogenesis imperfecta, and FGFR3 with achondroplasia.
Question 5:
A patient sustains a severe laceration to the anterior wrist, completely transecting the median nerve 2 cm proximal to the carpal tunnel. Despite the complete median nerve laceration, the patient retains a robust ability to oppose the thumb. Which of the following neural anomalies best explains this physical exam finding?
Options:
- Martin-Gruber anastomosis
- Marinacci anastomosis
- Riche-Cannieu anastomosis
- Berrettini anastomosis
- Linburg-Comstock anomaly
Correct Answer: Riche-Cannieu anastomosis
Explanation:
The Riche-Cannieu anastomosis is a neural connection between the deep branch of the ulnar nerve and the recurrent motor branch of the median nerve in the hand. This anomaly allows ulnar nerve innervation of typical median-innervated thenar muscles (e.g., opponens pollicis), preserving thumb opposition despite a high median nerve injury. Martin-Gruber is a median-to-ulnar anastomosis in the forearm.
Question 6:
A 48-year-old male with poorly controlled diabetes mellitus presents with a swollen, erythematous, and warm right foot without ulceration. He denies trauma. Radiographs reveal fragmentation of the navicular, subchondral debris, and loss of the medial longitudinal arch. Inflammatory markers are mildly elevated. According to the Eichenholtz classification, what is the most appropriate initial management?
Options:
- Immediate surgical arthrodesis of the midfoot
- Intravenous antibiotics and bone biopsy
- Total contact casting and strict non-weight bearing
- Custom orthotics and full weight-bearing
- Below-knee amputation
Correct Answer: Total contact casting and strict non-weight bearing
Explanation:
The patient is in Eichenholtz Stage 1 (Developmental/Fragmentation phase) of Charcot neuroarthropathy, characterized by erythema, swelling, warmth, and radiographic fragmentation and debris. The gold standard treatment is rigid immobilization and offloading, typically with a total contact cast (TCC), until the acute inflammatory phase resolves and the foot progresses to Stage 2 (Coalescence).
Question 7:
A 15-year-old male presents with acute thigh pain after a minor trip. Radiographs show a purely lytic, expansile metaphyseal lesion of the distal femur with a pathologic fracture. MRI demonstrates multiple fluid-fluid levels. Biopsy reveals blood-filled spaces with septations. Which microscopic finding definitively differentiates telangiectatic osteosarcoma from an aneurysmal bone cyst (ABC)?
Options:
- Presence of multinucleated giant cells
- Fibrous septa lacking an endothelial lining
- Highly atypical, pleomorphic stromal cells producing osteoid
- USP6 gene rearrangement
- Extensive areas of hemosiderin-laden macrophages
Correct Answer: Highly atypical, pleomorphic stromal cells producing osteoid
Explanation:
Telangiectatic osteosarcoma (TOS) closely mimics an aneurysmal bone cyst (ABC) clinically and radiographically (both show lytic lesions with fluid-fluid levels). The definitive differentiating feature is histological: in TOS, the septa contain highly malignant, pleomorphic cells producing sarcomatous osteoid. USP6 gene rearrangement is characteristic of primary ABCs, not TOS.
Question 8:
A 72-year-old female with severe osteoporosis is started on romosozumab. This medication increases bone mineral density by binding to and inhibiting sclerostin. Sclerostin normally functions to inhibit which of the following cellular pathways?
Options:
- RANK/RANKL signaling pathway
- Wnt/beta-catenin signaling pathway
- Osteoprotegerin (OPG) pathway
- Bone morphogenetic protein (BMP) pathway
- Insulin-like growth factor 1 (IGF-1) pathway
Correct Answer: Wnt/beta-catenin signaling pathway
Explanation:
Sclerostin is a glycoprotein secreted primarily by osteocytes that inhibits bone formation by binding to LRP5/6 receptors on osteoblasts, thereby antagonizing the canonical Wnt/beta-catenin signaling pathway. Romosozumab is a monoclonal antibody that neutralizes sclerostin, unblocking the Wnt pathway and strongly stimulating bone formation.
Question 9:
A 24-year-old soccer player sustains a twisting injury to his knee. Radiographs reveal a small cortical avulsion fracture off the lateral tibial plateau, just distal to the joint line. Which ligamentous structure has its distal insertion at this fracture site?
Options:
- Fibular collateral ligament
- Popliteofibular ligament
- Anterolateral ligament
- Posterior oblique ligament
- Arcuate ligament
Correct Answer: Anterolateral ligament
Explanation:
The radiograph describes a Segond fracture, an avulsion fracture of the anterolateral proximal tibia that is pathognomonic for an anterior cruciate ligament (ACL) tear. The Segond fragment represents the tibial bony insertion of the anterolateral ligament (ALL) and the anterolateral joint capsule.
Question 10:
A 9-year-old boy falls from a height and sustains a transepiphyseal fracture of the proximal femur (Delbet Type I) with dislocation of the femoral head. Following prompt open reduction and internal fixation, what is the most likely and devastating complication to occur?
Options:
- Nonunion
- Avascular necrosis (AVN) of the femoral head
- Coxa vara
- Chondrolysis
- Femoral nerve palsy
Correct Answer: Avascular necrosis (AVN) of the femoral head
Explanation:
Pediatric femoral neck fractures are classified by the Delbet classification. Delbet Type I (transepiphyseal fracture/separation) is the rarest but carries the highest risk of avascular necrosis (AVN) of the femoral head, approaching 80-100% when displaced or accompanied by dislocation, due to the complete disruption of the epiphyseal blood supply.
Question 11:
During a primary total knee arthroplasty, the surgeon inadvertently internally rotates the femoral component by 5 degrees relative to the surgical transepicondylar axis. Which of the following is the most likely clinical consequence of this technical error?
Options:
- Medial patellar subluxation
- Increased tension on the medial collateral ligament in flexion
- Lateral patellar tracking and potential subluxation
- Excessive femoral rollback in deep flexion
- Gap imbalance causing a tight extension gap and loose flexion gap
Correct Answer: Lateral patellar tracking and potential subluxation
Explanation:
Internal rotation of the femoral component in a TKA shifts the trochlear groove medially, which effectively increases the Q-angle. This relative change leads to lateral patellar maltracking, thereby increasing the risk of lateral patellar subluxation or dislocation. It also typically creates an asymmetric flexion gap that is tight medially.
Question 12:
A 14-year-old female gymnast presents with chronic lower back pain. Lateral lumbar radiographs demonstrate a Grade II isthmic spondylolisthesis at L5-S1. The pelvic incidence (PI) is measured at 75 degrees. Which of the following statements regarding her spinopelvic parameters is most accurate?
Options:
- Pelvic incidence is a dynamic parameter that decreases with forward flexion
- High pelvic incidence increases shear forces at the lumbosacral junction, predisposing to slip progression
- Pelvic incidence is calculated as the difference between pelvic tilt and sacral slope
- A high pelvic incidence necessitates a compensatory decrease in lumbar lordosis to maintain sagittal balance
- Surgical reduction of the spondylolisthesis will significantly decrease the pelvic incidence
Correct Answer: High pelvic incidence increases shear forces at the lumbosacral junction, predisposing to slip progression
Explanation:
Pelvic incidence (PI) is a fixed morphologic parameter (PI = Pelvic Tilt + Sacral Slope) that does not change with posture. A high PI (>60 degrees) correlates with a high sacral slope, which increases the shear forces across the pars interarticularis at the L5-S1 junction. This strongly predisposes patients to the development and progression of isthmic spondylolisthesis. A high PI requires a compensatory *increase* in lumbar lordosis.
Question 13:
An 8-week-old female is being treated with a Pavlik harness for developmental dysplasia of the hip (DDH). During follow-up, the mother notes that the infant is no longer kicking her right leg. Examination reveals decreased active knee extension on the right. What is the most likely cause of this finding?
Options:
- Excessive hip abduction in the harness
- Hyperflexion of the hip in the harness
- Ischemic necrosis of the proximal femoral epiphysis
- Brachial plexus traction injury
- Deep infection of the hip joint
Correct Answer: Hyperflexion of the hip in the harness
Explanation:
The infant has developed a femoral nerve palsy, a known complication of Pavlik harness treatment. It is caused by excessive hyperflexion of the hip, which compresses the femoral nerve against the inguinal ligament. Treatment involves adjusting the anterior straps to decrease hip flexion. Excessive hip abduction, by contrast, risks avascular necrosis (AVN) of the femoral head.
Question 14:
A 28-year-old male falls on an outstretched hand and complains of radial-sided wrist pain. Radiographs reveal a scapholunate gap of 4 mm and a scaphoid 'ring sign.' If left untreated, the carpal kinematics will become chronically altered. In this ensuing condition (DISI), what are the resultant resting positions of the scaphoid and lunate, respectively?
Options:
- Scaphoid flexed, Lunate flexed
- Scaphoid extended, Lunate flexed
- Scaphoid flexed, Lunate extended
- Scaphoid extended, Lunate extended
- Both bones remain neutral but translate ulnarly
Correct Answer: Scaphoid flexed, Lunate extended
Explanation:
Scapholunate dissociation disrupts the scapholunate interosseous ligament. Normal carpal kinematics dictate that the scaphoid tends to flex and the triquetrum tends to extend. When the SL ligament tears, the scaphoid falls into pathologic flexion (volar tilt), while the lunate follows the intact lunotriquetral ligament into extension (dorsal tilt). This creates a Dorsal Intercalated Segment Instability (DISI) pattern.
Question 15:
A 55-year-old female presents with a progressive flatfoot deformity and medial ankle pain. Examination reveals a flexible flatfoot, an inability to perform a single-limb heel rise, and greater than 50% uncovering of the talonavicular joint on weight-bearing AP radiographs. She has a positive Silfverskiold test demonstrating isolated gastrocnemius tightness. What is the most appropriate surgical management for this Johnson and Strom Stage IIb posterior tibial tendon dysfunction?
Options:
- Posterior tibial tendon debridement and synovectomy
- Flexor digitorum longus transfer, medial displacement calcaneal osteotomy, lateral column lengthening, and gastrocnemius recession
- Triple arthrodesis and Achilles tendon lengthening
- Tibiotalocalcaneal (TTC) arthrodesis
- Spring ligament repair without osseous intervention
Correct Answer: Flexor digitorum longus transfer, medial displacement calcaneal osteotomy, lateral column lengthening, and gastrocnemius recession
Explanation:
Stage IIb PTTD is characterized by a flexible deformity with significant forefoot abduction (>40% talonavicular uncovering). Surgical treatment typically requires soft tissue reconstruction (FDL transfer), hindfoot valgus correction (medial displacement calcaneal osteotomy), forefoot abduction correction (lateral column lengthening such as an Evans osteotomy), and addressing equinus (gastrocnemius recession). Rigid deformities (Stage III) require arthrodesis.
Question 16:
A 30-year-old male presents with a slow-growing, painful mass near his knee joint. MRI reveals a soft-tissue mass adjacent to but not communicating with the joint capsule. A core needle biopsy shows a biphasic tumor with both epithelial and spindle cell components. Which chromosomal translocation is highly characteristic of this malignancy?
Options:
- t(11;22)(q24;q12)
- t(X;18)(p11;q11)
- t(12;16)(q13;p11)
- t(2;13)(q35;q14)
- t(9;22)(q34;q11)
Correct Answer: t(X;18)(p11;q11)
Explanation:
The vignette describes a biphasic synovial sarcoma, which is characterized by the t(X;18)(p11;q11) chromosomal translocation resulting in the SYT-SSX fusion gene. t(11;22) is seen in Ewing sarcoma; t(12;16) in myxoid liposarcoma; t(2;13) in alveolar rhabdomyosarcoma; and t(9;22) in extraskeletal myxoid chondrosarcoma.
Question 17:
Articular cartilage is composed of an extracellular matrix and chondrocytes arranged in highly organized distinct zones. Which of the following best describes the structural and biochemical properties of the superficial (tangential) zone of normal articular cartilage?
Options:
- Lowest water content, highest proteoglycan content, collagen fibers oriented perpendicular to the joint surface
- Highest water content, lowest proteoglycan content, collagen fibers oriented parallel to the joint surface
- Highest water content, highest proteoglycan content, random collagen orientation
- Lowest water content, lowest proteoglycan content, chondrocytes arranged in vertical columns
- Highly calcified matrix, delineating the tidemark from subchondral bone
Correct Answer: Highest water content, lowest proteoglycan content, collagen fibers oriented parallel to the joint surface
Explanation:
The superficial (tangential) zone of articular cartilage constitutes the top 10-20% of the cartilage thickness. It has the highest water content, highest collagen content, and lowest proteoglycan content. The densely packed Type II collagen fibers are arranged parallel to the articular surface to strongly resist shear forces.
Question 18:
A 28-year-old professional baseball pitcher complains of deep shoulder pain and a 'dead arm' sensation. An MR arthrogram reveals a superior labral tear that extends into the root of the long head of the biceps tendon, with significant displacement of the biceps anchor into the glenohumeral joint. According to the Snyder classification, what is the best description and optimal surgical treatment of this injury in an active patient?
Options:
- Type II SLAP tear; treat with simple labral debridement
- Type II SLAP tear; treat with superior labral repair using suture anchors
- Type III SLAP tear; treat with resection of the bucket-handle tear
- Type IV SLAP tear; treat with biceps tenodesis and labral debridement/repair
- Type V SLAP tear; treat with a standard Bankart repair
Correct Answer: Type IV SLAP tear; treat with biceps tenodesis and labral debridement/repair
Explanation:
A Type IV SLAP tear is defined as a bucket-handle tear of the superior labrum that propagates into the long head of the biceps tendon (LHBT). In an active patient with significant involvement of the LHBT (typically >30%), biceps tenodesis combined with labral debridement or repair is the recommended treatment. Type II is simply detachment of the superior labrum/biceps anchor. Type III is a bucket-handle tear with an intact biceps anchor.
Question 19:
A 42-year-old male suffers a high-energy varus-directed force to his knee during a motor vehicle collision. Radiographs reveal a displaced fracture of the medial tibial plateau with depression and separation of the medial fragment. Which of the following vascular structures is at the highest risk of injury in this specific fracture pattern?
Options:
- Anterior tibial artery at the level of the interosseous membrane
- Posterior tibial artery in the distal third of the leg
- Popliteal artery at the level of the popliteal trifurcation
- Peroneal artery traversing the lateral compartment
- Medial inferior genicular artery
Correct Answer: Popliteal artery at the level of the popliteal trifurcation
Explanation:
This is a Schatzker Type IV medial tibial plateau fracture. Occurring via a high-energy varus stress, medial plateau fractures are notorious for severe associated soft tissue injuries, including peroneal nerve palsies and lateral collateral ligament disruption. Critically, there is a high risk of damage to the popliteal artery/trifurcation due to posterior subluxation of the knee or the displacement of the medial plateau fragment.
Question 20:
A 70-year-old male presents 2 years after a primary total hip arthroplasty with a draining sinus tract communicating with the hip joint. According to the 2018 Musculoskeletal Infection Society (MSIS) / International Consensus Meeting (ICM) criteria for periprosthetic joint infection (PJI), which of the following is true regarding this patient's diagnosis?
Options:
- A synovial fluid leukocyte count >3,000 cells/uL is strictly required to confirm PJI
- A sinus tract communicating with the joint is a major criterion and definitively diagnoses PJI
- Two positive periprosthetic tissue cultures with different organisms are required for definitive diagnosis
- Elevated serum CRP and ESR are mandatory for diagnosis
- An elevated synovial alpha-defensin test is required as a major criterion
Correct Answer: A sinus tract communicating with the joint is a major criterion and definitively diagnoses PJI
Explanation:
According to the 2018 MSIS/ICM criteria, the presence of a sinus tract communicating with the prosthesis OR two positive tissue/fluid cultures isolating the exact same organism are considered 'major criteria.' The presence of either of these major criteria is definitively diagnostic for a periprosthetic joint infection (PJI) without the need for minor criteria scoring (such as ESR, CRP, synovial WBC count, or alpha-defensin).
