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Arab Orthopaedic Board MCQs - Part 25

27 Apr 2026 105 min read 88 Views
Arab Ortho Board MCQs - Part 24

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We review everything you need to understand about Arab Orthopaedic Board MCQs - Part 25. Practice Arab Orthopaedic Board MCQs Part 25. Review orthopedic surgery questions 1201 to 1250 for your board exam preparation.

Arab Orthopaedic Board MCQs - Part 25

Comprehensive 100-Question Exam


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Question 1

A 28-year-old male sustains a vertically oriented femoral neck fracture (Pauwels III). Biomechanical studies show which fixation construct provides the highest load to failure and greatest resistance to shear forces for this specific fracture pattern?





Explanation

Biomechanical studies demonstrate that a sliding hip screw (SHS) with an anti-rotation screw provides superior fixation for vertically oriented (Pauwels III) femoral neck fractures compared to multiple cancellous screws, primarily by better resisting the high shear forces across the vertical fracture line.

Question 2

A 4-month-old female is diagnosed with developmental dysplasia of the hip (DDH) after an ultrasound shows an alpha angle of 40 degrees and 20% coverage. She is placed in a Pavlik harness. Which complication is most closely associated with excessive hip flexion in the harness?





Explanation

Excessive hip flexion (>120 degrees) in a Pavlik harness can impinge the femoral nerve against the inguinal ligament, leading to femoral nerve palsy. Excessive abduction is strongly associated with avascular necrosis (AVN) of the femoral head.

Question 3

A 45-year-old male presents with right arm pain, weakness in elbow extension, and diminished triceps reflex. Sensation is decreased over the long finger. Which cervical nerve root is most likely affected?





Explanation

The C7 nerve root supplies the triceps (elbow extension), wrist flexors, and finger extensors. Sensory distribution is classically to the middle finger. The triceps reflex is primarily mediated by the C7 nerve root.

Question 4

In total hip arthroplasty, which bearing surface combination exhibits the lowest linear wear rate but carries the unique risk of stripe wear and squeaking?





Explanation

Ceramic-on-ceramic bearings have the lowest linear and volumetric wear rates of all combinations. However, they are uniquely associated with audible 'squeaking' and can exhibit stripe wear during edge loading due to micro-separation.

Question 5

A 25-year-old carpenter sustains a laceration over the volar aspect of the proximal phalanx of the index finger, resulting in loss of PIP and DIP flexion. This injury corresponds to which flexor tendon zone, traditionally known as 'no man's land'?





Explanation

Zone II extends from the proximal edge of the A1 pulley to the insertion of the Flexor Digitorum Superficialis (FDS) on the middle phalanx. It contains both FDS and FDP tendons in a tight fibro-osseous sheath and was historically termed 'no man's land' due to the high rate of adhesions and poor functional outcomes following repair.

Question 6

A 22-year-old football player sustains a hyperplantarflexion injury to his midfoot. Weight-bearing radiographs reveal a 3 mm diastasis between the bases of the first and second metatarsals. What is the primary stabilizing ligament of this articulation?





Explanation

The Lisfranc ligament is an interosseous/plantar ligament that connects the lateral aspect of the medial cuneiform to the medial base of the second metatarsal. It is the thickest, strongest, and primary stabilizer of the Lisfranc joint complex.

Question 7

A 15-year-old boy presents with knee pain. Radiographs show a destructive, bone-forming lesion in the distal femur metaphysis with a 'sunburst' periosteal reaction. A biopsy confirms high-grade conventional osteosarcoma. What is the standard treatment protocol?





Explanation

The standard of care for high-grade, conventional osteosarcoma is neoadjuvant (pre-operative) multi-agent chemotherapy, followed by wide surgical resection (limb-salvage when possible), and then adjuvant (post-operative) chemotherapy tailored by the percentage of histologic necrosis in the resected specimen.

Question 8

During secondary bone healing, which factor is most crucial for the transition from a soft cartilaginous callus to a hard bony callus?





Explanation

The transition from soft (cartilaginous) callus to hard (bony) callus during endochondral ossification requires adequate vascular ingrowth (angiogenesis), which brings in chondroclasts, osteoprogenitor cells, and oxygen required for matrix mineralization.

Question 9

A 20-year-old soccer player undergoes an anterior cruciate ligament (ACL) reconstruction using a bone-patellar tendon-bone (BTB) autograft. What is the most common complication specifically associated with this graft choice compared to hamstring autograft?





Explanation

Bone-patellar tendon-bone (BTB) autograft is highly associated with donor site morbidity, most notably anterior knee pain and pain with kneeling, compared to hamstring autografts.

Question 10

A 35-year-old male is admitted with a closed tibia fracture. Eight hours later, he develops severe pain out of proportion to the injury, exacerbated by passive stretch of the toes. Intracompartmental pressure monitoring is planned. What is the generally accepted threshold for performing a fasciotomy?





Explanation

The threshold for diagnosing acute compartment syndrome and indicating a fasciotomy is a delta pressure (Diastolic Blood Pressure - Compartment Pressure) of less than 30 mmHg. This measurement accounts for systemic perfusion pressure, making it more accurate than absolute compartment pressure alone.

Question 11

A 13-year-old obese boy presents with a 3-week history of right groin and thigh pain, and a limp. Examination reveals obligate external rotation of the right hip during passive flexion. Radiographs confirm a mild Slipped Capital Femoral Epiphysis (SCFE). What is the most appropriate initial management?





Explanation

The gold standard treatment for a stable SCFE is in situ percutaneous pinning with a single cannulated screw to prevent further slip. Attempted closed reduction is strongly contraindicated due to the high risk of causing avascular necrosis (AVN) of the femoral head.

Question 12

A 50-year-old woman complains of numbness in her ring and small fingers, and weakness in her hand. Examination shows a positive Froment's sign when she is asked to hold a piece of paper between her thumb and index finger. Which muscle is compensating to produce the positive Froment's sign?





Explanation

Froment's sign occurs in ulnar nerve palsy. The paralyzed adductor pollicis (ulnar nerve) is compensated for by the flexor pollicis longus (innervated by the Anterior Interosseous Nerve branch of the median nerve), causing hyperflexion of the thumb interphalangeal joint during pinch.

Question 13

A 65-year-old male presents with bilateral leg pain and heaviness that worsens with walking and improves when he leans forward on a shopping cart. MRI shows severe L4-L5 central spinal stenosis. Which anatomic structure is the primary cause of dorsal compression in this condition?





Explanation

Degenerative central spinal stenosis is classically caused by a combination of bulging intervertebral disc anteriorly, facet joint hypertrophy laterally, and a hypertrophied (and often buckled) ligamentum flavum posteriorly/dorsally. Thus, the ligamentum flavum causes the dorsal compression.

Question 14

According to the Musculoskeletal Infection Society (MSIS) criteria, which of the following is considered a 'major' criterion (definitive evidence) for the diagnosis of a periprosthetic joint infection?





Explanation

Under the MSIS criteria for periprosthetic joint infection, a major criterion is either: 1) a sinus tract communicating with the prosthesis, or 2) a pathogen isolated by culture from at least two separate tissue or fluid samples. The other options are considered minor criteria.

Question 15

In an anteroposterior compression (APC) type II pelvic ring injury (open book), the pubic symphysis is diastatic > 2.5 cm. Which posterior pelvic ligaments are disrupted, and which remain intact?





Explanation

In an APC-II injury, the pubic symphysis diastasis (>2.5 cm) is accompanied by tearing of the anterior sacroiliac ligaments, the sacrotuberous ligaments, and the sacrospinous ligaments. The strong posterior sacroiliac ligaments remain intact, leading to rotational instability but vertical stability.

Question 16

A 42-year-old 'weekend warrior' sustains an acute Achilles tendon rupture. He opts for non-operative management. What is the most critical component of the early functional rehabilitation protocol to minimize the re-rupture rate?





Explanation

Modern non-operative management of Achilles tendon ruptures heavily relies on functional rehabilitation. This includes early weight-bearing in plantarflexion (using functional braces with heel wedges) and early controlled active range of motion. This active approach produces re-rupture rates comparable to operative management.

Question 17

A patient is scheduled for an elective total knee arthroplasty. He is currently taking Rivaroxaban for atrial fibrillation. What is the mechanism of action of this medication?





Explanation

Rivaroxaban (Xarelto) is a direct oral anticoagulant (DOAC) that functions as a direct and reversible inhibitor of Factor Xa, interrupting the intrinsic and extrinsic pathway of the blood coagulation cascade. Dabigatran, conversely, is a direct thrombin (Factor IIa) inhibitor.

Question 18

A 32-year-old manual laborer presents with chronic dorsal wrist pain and decreased grip strength. Radiographs reveal sclerosis and fragmentation of the lunate, with a negative ulnar variance of 3mm. Which procedure is most appropriate to unload the lunate in this early-stage patient?





Explanation

The patient has early-stage Kienböck's disease (avascular necrosis of the lunate) associated with ulnar minus variance. Joint-leveling procedures, such as a radial shortening osteotomy or ulnar lengthening, decrease the compressive forces across the radiolunate joint and are indicated in early stages prior to carpal collapse.

Question 19

A 6-year-old boy is diagnosed with Legg-Calvé-Perthes disease. Which of the following radiographic signs is considered a 'head at risk' sign according to Catterall, indicating a potentially poorer prognosis?





Explanation

Catterall 'head at risk' signs for Legg-Calvé-Perthes disease indicate impending collapse and poor prognosis. They include the Gage sign (a small V-shaped radiolucency in the lateral portion of the epiphysis and adjacent metaphysis), lateral calcification, lateral subluxation, a horizontal physis, and metaphyseal cysts.

Question 20

A 30-year-old female presents with knee pain. Radiographs show an eccentric, lytic lesion in the epiphysis of the proximal tibia extending to the subchondral bone, with no sclerotic margin. Biopsy shows multinucleated giant cells in a stroma of mononuclear cells. Which monoclonal antibody is approved for treating unresectable or recurrent forms of this tumor?





Explanation

The lesion described is a Giant Cell Tumor of bone (GCT). The mononuclear stromal cells express RANKL, which recruits and stimulates osteoclast-like giant cells causing osteolysis. Denosumab is a monoclonal antibody against RANKL and is highly effective in treating unresectable or recurrent GCTs.

Question 21

An 18-month-old child presents with an untreated developmental dysplasia of the hip (DDH) and undergoes an open reduction and spica casting. Intraoperatively, the surgeon carefully positions the hip. Which of the following maneuvers is the most critical intraoperative factor to prevent avascular necrosis (AVN) of the femoral head?





Explanation

Extreme abduction (the traditional 'frog-leg' position) causes increased mechanical pressure on the vulnerable capital femoral epiphysis and its blood supply, significantly increasing the risk of iatrogenic AVN. The safe zone of Ramsey mandates immobilizing the hip in the 'human position' (moderate abduction and flexion).

Question 22

A 45-year-old male sustains an anteroposterior compression type III (APC-III) pelvic ring injury following a crush accident. After initial resuscitation, an anterior external fixator is placed. What is the primary biomechanical limitation of an anterior external fixator in this specific injury pattern?





Explanation

An APC-III injury involves complete disruption of both the anterior ring (symphysis pubis) and the posterior sacroiliac complex (anterior and posterior SI ligaments, sacrotuberous, sacrospinous). An anterior external fixator cannot adequately control the highly unstable posterior ring. Posterior stabilization (e.g., SI screws or posterior plating) is mandatory.

Question 23

A 30-year-old female presents with a lytic, eccentrically located lesion in the distal femur extending to the subchondral bone. A biopsy confirms Giant Cell Tumor (GCT) of bone. She is treated preoperatively with denosumab. What is the exact mechanism of action of denosumab in this context?





Explanation

Denosumab is a human monoclonal antibody that specifically binds to and inhibits RANK ligand (RANKL). In Giant Cell Tumors, the neoplastic stromal cells overexpress RANKL, which recruits and activates the multinucleated giant cells (osteoclast-like cells) responsible for massive bone resorption. Denosumab blocks this interaction, reducing the tumor's osteolysis and giant cell population.

Question 24

A 25-year-old manual laborer presents with an acute scaphoid proximal pole fracture and requests surgical fixation. What is the anatomical basis for the high rate of avascular necrosis and nonunion specifically associated with proximal pole fractures?





Explanation

The primary blood supply to the scaphoid comes from the dorsal carpal branch of the radial artery, which enters the scaphoid at the distal pole and waist, flowing in a retrograde direction to the proximal pole. Fractures at the proximal pole disrupt this retrograde flow, heavily predisposing the proximal fragment to ischemia and AVN.

Question 25

During an ACL reconstruction using a bone-patellar tendon-bone autograft, the surgeon chooses to drill the femoral tunnel via an accessory anteromedial portal rather than a transtibial approach. Which of the following is a recognized risk of this technique?





Explanation

Drilling the femoral tunnel independently through an anteromedial portal allows for more anatomic (lower and more horizontal) placement of the ACL graft. However, it carries a higher risk of posterior wall blowout (a short, compromised tunnel) and requires the knee to be hyperflexed (at least 110-120 degrees) during drilling to avoid articular cartilage damage and ensure adequate tunnel length.

Question 26

A 68-year-old male undergoes a primary Total Hip Arthroplasty via a posterior approach. Postoperatively, he exhibits a complete foot drop and inability to extend his toes. Which specific neural structure is most commonly injured to produce this deficit during THA?





Explanation

The common peroneal division of the sciatic nerve is the most frequently injured nerve during a THA (most commonly from stretch during leg lengthening or retractor placement). It is more susceptible than the tibial division because it is tethered at the fibular head, is positioned more laterally, and has less connective tissue support within the sciatic sheath.

Question 27

A 72-year-old male with progressive clumsiness in his hands and a wide-based gait is diagnosed with cervical spondylotic myelopathy (Nurick grade 4). MRI demonstrates multi-level continuous compression from C3 to C6, predominantly due to ossification of the posterior longitudinal ligament (OPLL). Cervical lordosis is preserved. Which surgical approach is generally most appropriate?





Explanation

In patients with multi-level (3 or more) spinal cord compression primarily due to OPLL, especially when cervical lordosis is preserved, a posterior approach (laminectomy and fusion or laminoplasty) is preferred. Multi-level anterior corpectomies for continuous OPLL carry unacceptably high risks of dural tears, cerebrospinal fluid leaks, and construct failure.

Question 28

Articular cartilage provides a nearly frictionless surface and absorbs tremendous loads. Which specific extracellular matrix component is primarily responsible for retaining water to provide compressive stiffness?





Explanation

Aggrecan is the most abundant large proteoglycan in articular cartilage. Its highly negatively charged glycosaminoglycan (GAG) side chains (chondroitin sulfate and keratin sulfate) attract cations and water via the Donnan osmotic effect. This swelling pressure, constrained by the collagen network, provides cartilage with its compressive stiffness.

Question 29

A 55-year-old woman undergoes volar locking plate fixation for a volarly displaced, intra-articular distal radius fracture. Eight weeks postoperatively, she suddenly loses the ability to actively flex the interphalangeal joint of her thumb. Which structure was most likely injured?





Explanation

Flexor pollicis longus (FPL) tendon rupture is a well-documented complication of volar plating of the distal radius. It typically occurs due to attritional wear when the plate is placed too distally (anterior to the watershed line), causing the FPL tendon to rub against the prominent distal edge of the plate.

Question 30

A 13-year-old obese boy presents with a 3-week history of left knee pain and a limp. Examination reveals obligatory external rotation of the left hip with passive flexion. Radiographs confirm a stable Slipped Capital Femoral Epiphysis (SCFE). Which of the following best describes the true anatomical displacement occurring in a SCFE?





Explanation

In a SCFE, the capital femoral epiphysis remains essentially in its normal position within the acetabulum. The true pathology is the displacement of the femoral neck (metaphysis), which translates anteriorly and laterally (externally rotates) relative to the epiphysis. On standard radiographs, this makes the epiphysis appear to have slipped posteriorly and medially.

Question 31

A 55-year-old diabetic male presents with a heavily swollen, erythematous, but relatively painless right foot. He denies trauma. Radiographs show early fragmentation, debris, and subluxation at the tarsometatarsal (Lisfranc) joints. What is the most appropriate initial management for this presentation?





Explanation

This patient presents with acute Eichenholtz stage I (fragmentation phase) Charcot neuroarthropathy. The gold standard for initial management of an acute, active Charcot foot is total contact casting and offloading to halt the destructive process and prevent further deformity until the acute inflammation subsides and the bones coalesce (Stage II/III).

Question 32

During a total knee arthroplasty, the surgeon trials the components and notes that the knee is perfectly balanced and stable in full extension, but feels excessively tight in 90 degrees of flexion. What is the most appropriate surgical step to correct this specific mismatch?





Explanation

A knee that is balanced in extension but tight in flexion has an isolated tight flexion gap. With an anterior referencing system, downsizing the femoral component will decrease the anteroposterior dimension by resecting more posterior condylar bone, thereby enlarging the flexion gap without altering the distal femoral cut (which controls the extension gap).

Question 33

To significantly decrease the wear rate of ultra-high-molecular-weight polyethylene (UHMWPE) in total joint arthroplasty, it is subjected to high-dose irradiation. However, this process requires a secondary step to prevent long-term failure. What is the primary purpose of this secondary step (e.g., melting or annealing)?





Explanation

Highly cross-linking UHMWPE via gamma irradiation significantly improves wear resistance but generates free radicals. If left untreated, these free radicals react with oxygen in vivo, leading to oxidation, delamination, and embrittlement. A secondary thermal treatment (melting or annealing) or doping with Vitamin E is necessary to quench these free radicals and ensure oxidative stability.

Question 34

During surgical fasciectomy for Dupuytren's contracture, the neurovascular bundle is at risk of iatrogenic injury. Which pathological fascial cord is classically responsible for displacing the neurovascular bundle toward the midline, placing it directly in harm's way?





Explanation

The spiral cord is formed by the amalgamation of the pretendinous band, spiral band, lateral digital sheet, and Grayson's ligament. As it contracts, it pulls the neurovascular bundle proximally, centrally (toward the midline), and superficial to the cord itself, putting the bundle at high risk of transection during dissection.

Question 35

A 22-year-old professional rugby player presents with recurrent anterior shoulder instability. A 3D CT scan of the shoulder reveals an anterior glenoid bone loss of 28%. Which surgical procedure is most highly indicated for this patient to prevent further dislocations?





Explanation

In the presence of critical anterior glenoid bone loss (>20-25%), soft-tissue repairs (Bankart) have an unacceptably high failure rate. The Latarjet procedure (transfer of the coracoid process to the anterior glenoid) is the gold standard. It restores the bony arc and provides a dynamic 'sling effect' from the attached conjoined tendon.

Question 36

A 32-year-old previously healthy male sustains an isolated, closed, transverse fracture of the middle third of the femoral shaft in a motor vehicle collision. He is hemodynamically stable without head or chest trauma. What is the optimal timing for intramedullary nailing of this fracture?





Explanation

In a hemodynamically stable patient without severe physiological insults (polytrauma, severe head, or chest injuries requiring damage control orthopedics), early definitive fixation of femoral shaft fractures (within 24 hours) is the standard of care. It significantly reduces the rates of pulmonary complications (ARDS, pneumonia), mortality, and hospital length of stay.

Question 37

A 15-year-old boy presents with worsening distal thigh pain. Radiographs show a destructive, permeative metaphyseal lesion with a 'sunburst' periosteal reaction and a Codman's triangle. Core needle biopsy confirms high-grade conventional osteosarcoma. What is the current standard treatment protocol?





Explanation

The standard of care for high-grade conventional osteosarcoma is neoadjuvant (preoperative) chemotherapy, followed by wide surgical resection (limb salvage is preferred when feasible), and subsequently adjuvant (postoperative) chemotherapy. Osteosarcoma is generally considered radioresistant, so radiation therapy is primarily reserved for unresectable tumors or positive margins.

Question 38

A 14-year-old female gymnast complains of mechanical lower back pain and bilateral L5 radicular symptoms. Lateral lumbar radiographs demonstrate a Grade II forward slip of L5 on S1. What is the most likely pathological mechanism underlying this specific type of spondylolisthesis?





Explanation

Isthmic spondylolisthesis is the most common type of spondylolisthesis in children and adolescents, particularly in athletes subjected to repetitive hyperextension forces (e.g., gymnastics, football linemen). It is caused by a fatigue stress fracture or elongation (spondylolysis) of the pars interarticularis, almost exclusively at the L5 level.

Question 39

A 45-year-old highly active male is undergoing an elective Total Hip Arthroplasty. The surgeon opts for a ceramic-on-ceramic (CoC) bearing surface. Which of the following represents the primary biomechanical advantage of CoC compared to conventional metal-on-polyethylene bearings?





Explanation

Ceramic-on-ceramic (CoC) bearings provide the lowest volumetric wear rate of any current bearing couple due to their extreme hardness, wettability, and smoothness. This makes them highly desirable for young, active patients. However, they carry a risk of catastrophic fracture, can produce squeaking, and are highly intolerant of component malpositioning (which leads to edge loading and stripe wear).

Question 40

A 28-year-old man sustains a high-energy tibial plateau fracture with severe soft tissue crushing. Clinical suspicion for acute compartment syndrome is high. Which of the following objective measurements is widely accepted as the absolute threshold for performing an emergent four-compartment fasciotomy?





Explanation

The Delta P concept is the most accurate parameter for diagnosing acute compartment syndrome, particularly in hypotensive patients. A Delta P (diastolic blood pressure minus intracompartmental pressure) of less than 30 mmHg indicates that tissue perfusion is critically compromised, mandating an emergent fasciotomy.

Question 41

A 65-year-old man undergoes a right total hip arthroplasty via a posterior approach. Six weeks postoperatively, he experiences an anterior dislocation of the prosthesis while getting out of a low chair. Which of the following combinations of component positioning is most likely responsible for an anterior dislocation?





Explanation

Anterior dislocation in total hip arthroplasty typically occurs when the hip is placed in extension and external rotation, and is strongly associated with excessive combined anteversion (excessive acetabular anteversion and excessive femoral anteversion). Conversely, posterior dislocations are associated with inadequate anteversion or excessive retroversion.

Question 42

A 28-year-old male is brought to the trauma bay after a motorcycle collision. Radiographs demonstrate an anteroposterior compression type III (APC-III) pelvic ring injury with severe diastasis of the pubic symphysis and completely disrupted sacroiliac joints. He is hypotensive despite fluid resuscitation. What is the most common anatomical source of massive hemorrhage in this fracture pattern?





Explanation

While arterial bleeding (e.g., from the superior gluteal or internal pudendal arteries) can occur and is often life-threatening, venous bleeding from the presacral venous plexus and fracture cancellous surfaces accounts for 80-90% of hemorrhage in pelvic ring injuries. This is why pelvic binders and volume reduction are critical first steps.

Question 43

Which of the following patients presenting with a unilateral slipped capital femoral epiphysis (SCFE) has the strongest clinical indication for prophylactic pinning of the contralateral, asymptomatic hip?





Explanation

Endocrine disorders (such as hypothyroidism, renal osteodystrophy, and growth hormone deficiency) carry a very high risk (up to 100% in some series) for the development of bilateral SCFE. Patients with these underlying conditions or very young patients (<10 years old) have the strongest indication for prophylactic contralateral pinning.

Question 44

In the highly organized structure of healthy articular cartilage, which layer is characterized by the highest concentration of proteoglycans, the lowest water content, and collagen fibers arranged perpendicularly to the joint surface?





Explanation

The deep (radial) zone of articular cartilage contains the largest diameter collagen fibers oriented perpendicular to the articular surface. It also has the highest concentration of proteoglycans and the lowest water content, optimizing it to resist compressive forces.

Question 45

A 35-year-old male presents with a slow-growing, painful soft tissue mass on the plantar aspect of his foot. Biopsy reveals a biphasic tumor containing both epithelial and spindle cell components. Which of the following chromosomal translocations is characteristic of this pathology?





Explanation

The patient has a synovial sarcoma, which frequently presents in the extremities of young adults and can be biphasic (epithelial and spindle cells). It is genetically characterized by the t(X;18)(p11;q11) translocation, resulting in the SYT-SSX fusion gene. t(11;22) is found in Ewing sarcoma, t(12;16) in myxoid liposarcoma, and t(2;13) in alveolar rhabdomyosarcoma.

Question 46

During the physical examination of a patient with suspected cervical spondylotic myelopathy, the examiner supports the patient's hand and firmly flicks the distal phalanx of the middle finger downward. A positive response is noted as reflex flexion of the interphalangeal joint of the thumb. What is the name of this clinical sign?





Explanation

Hoffmann's sign is an upper motor neuron sign elicited by flicking the distal phalanx of the middle finger, leading to reflex flexion of the thumb and/or index finger. It indicates cervical cord compression or other upper motor neuron pathology.

Question 47

A patient with a chronic, irreversible high radial nerve palsy requires tendon transfer surgery to restore wrist and digit extension. What is the most widely utilized and standard tendon transfer to restore wrist extension?





Explanation

The Pronator Teres (PT) to Extensor Carpi Radialis Brevis (ECRB) transfer is the workhorse procedure for restoring wrist extension in radial nerve palsy. The ECRB is preferred over the ECRL because of its more central insertion, which provides balanced dorsiflexion of the wrist without excessive radial deviation.

Question 48

Following arthroscopic rotator cuff repair, healing at the tendon-bone interface progresses through inflammatory, proliferative, and remodeling phases. During the early proliferative phase of healing at the footprint, which type of collagen is predominately synthesized?





Explanation

During the proliferative phase of tendon-bone healing (and tendon healing in general), fibroblasts rapidly synthesize Type III collagen, which forms disorganized granulation tissue. During the remodeling phase, this is gradually replaced by stronger, highly organized Type I collagen.

Question 49

A 55-year-old male with poorly controlled diabetes presents with a swollen, warm, and erythematous left foot without any open ulcers. Radiographs demonstrate extensive subchondral fragmentation, joint subluxation, and intra-articular loose debris without significant osteosclerosis. According to the Eichenholtz classification of Charcot arthropathy, what stage does this clinical and radiographic picture represent?





Explanation

Eichenholtz Stage I is the developmental or fragmentation stage, characterized radiographically by osteochondral fragmentation, joint subluxation, and debris formation. Stage 0 is clinically warm and swollen but with normal radiographs. Stage II (coalescence) features absorption of fine debris and early sclerosis. Stage III (reconstruction) shows rounding of bone ends and solid consolidation.

Question 50

A 32-year-old female sustains a high-energy distal femur fracture. A CT scan confirms an isolated coronal shear fracture of the lateral femoral condyle (Hoffa fracture). Which of the following muscle attachments provides the primary deforming force on the distal fracture fragment?





Explanation

In a lateral Hoffa fracture, the popliteus and the lateral head of the gastrocnemius muscles remain attached to the posterior condylar fragment, exerting a strong posterior and inferior deforming force that necessitates rigid internal fixation (typically with posteroanterior or anteroposterior lag screws).

Question 51

In the management of Legg-Calvé-Perthes disease, the Herring lateral pillar classification is widely used to determine prognosis and guide treatment. During which stage of the disease must this classification be assessed to accurately predict outcome?





Explanation

The Herring lateral pillar classification is most accurate and prognostically significant when assessed during the early fragmentation stage of Legg-Calvé-Perthes disease, as it determines the height of the preserved lateral pillar which is crucial to preventing femoral head extrusion.

Question 52

Cross-linking of ultra-high molecular weight polyethylene (UHMWPE) is heavily utilized in total hip arthroplasty to reduce wear. However, increasing the radiation dose to achieve higher cross-linking has which of the following detrimental effects on the mechanical properties of the polyethylene liner?





Explanation

Highly cross-linked polyethylene drastically reduces volumetric wear. However, the radiation process used to induce cross-linking significantly decreases mechanical properties, most notably fatigue strength, ultimate tensile strength, and fracture toughness, which can increase the risk of rim fracture or structural failure in certain applications.

Question 53

A 25-year-old male sustains a closed comminuted tibial shaft fracture. Clinical examination for acute compartment syndrome is equivocal due to a concomitant traumatic brain injury. Intracompartmental pressures are measured. Which of the following hemodynamic parameters is the most reliable threshold indicator for performing an emergent fasciotomy?





Explanation

The delta pressure (Diastolic Blood Pressure minus Compartment Pressure) is considered the most reliable indicator for diagnosing acute compartment syndrome. A delta pressure of less than 30 mmHg (some literature states <20-30 mmHg) strongly suggests inadequate tissue perfusion and is an indication for fasciotomy.

Question 54

The primary blood supply to the scaphoid bone is tenuous, predisposing the proximal pole to avascular necrosis after a fracture. This critical blood supply originates from branches of the radial artery and enters the bone at which specific anatomical location?





Explanation

The primary blood supply to the scaphoid (accounting for 70-80% of its vascularity) comes from dorsal branches of the radial artery that enter the bone along the dorsal ridge distal to the waist. This intraosseous blood flow is retrograde, explaining the high rate of avascular necrosis in proximal pole fractures.

Question 55

When comparing the structural properties of a standard 10-mm central third bone-patellar tendon-bone (BTB) autograft to the native intact anterior cruciate ligament (ACL) at time zero, which of the following statements is most accurate?





Explanation

A 10-mm BTB graft has an ultimate failure load of approximately 2,900 N and a stiffness of 685 N/mm. The native ACL has an ultimate failure load of approximately 2,160 N and a stiffness of 242 N/mm. Thus, the 10-mm BTB autograft is both stronger (higher ultimate load) and stiffer than the native ACL at time zero.

Question 56

In the Lenke classification system for adolescent idiopathic scoliosis, a Type 1 (Main Thoracic) curve pattern is defined strictly by which of the following parameters regarding structurality?





Explanation

According to the Lenke classification, a Type 1 curve is defined by a main thoracic major curve that is structural, while the proximal thoracic and the thoracolumbar/lumbar curves are minor and non-structural (bending out to < 25 degrees).

Question 57

Denosumab is used as a medical treatment for large or unresectable giant cell tumors of bone (GCTB). By what specific molecular mechanism does denosumab halt the progression of this disease?





Explanation

Giant cell tumor of bone consists of neoplastic mononuclear stromal cells that overexpress RANKL. This overexpression recruits and activates normal monocytes to become reactive, bone-resorbing multinucleated giant cells. Denosumab is a monoclonal antibody that binds directly to RANKL, halting this interaction and stopping bone destruction.

Question 58

During secondary bone healing, endochondral ossification is heavily reliant on the differentiation of mesenchymal stem cells into chondrocytes within the soft callus. Which of the following transcription factors is the primary master regulator driving this chondrogenic differentiation?





Explanation

Sox9 is the master transcription factor responsible for the commitment and differentiation of mesenchymal stem cells into chondrocytes during endochondral ossification. Runx2 and Osterix are master regulators for osteoblast differentiation.

Question 59

A 6-week-old infant with developmental dysplasia of the hip (DDH) is placed in a Pavlik harness. Two weeks later, the parents report the infant is not kicking the affected leg. On exam, the anterior straps are noted to be excessively tight, positioning the hip in greater than 120 degrees of flexion. Which complication has most likely occurred?





Explanation

Excessive flexion in a Pavlik harness (typically > 120 degrees) can compress the femoral nerve against the inguinal ligament, leading to a temporary femoral nerve palsy (manifested by decreased knee extension/kicking). Excessive abduction (tight posterior straps) increases the risk of avascular necrosis.

Question 60

A 50-year-old female presents with stage IIb adult-acquired flatfoot deformity, characterized by a flexible deformity with significant forefoot abduction (>40% uncovering of the talonavicular joint on AP weight-bearing radiographs). Which surgical combination is most appropriate to correct this multi-planar deformity?





Explanation

Stage IIb posterior tibial tendon dysfunction indicates a flexible flatfoot with significant forefoot abduction. While an FDL transfer and MDCO correct the valgus hindfoot, the forefoot abduction requires a lateral column lengthening (e.g., Evans osteotomy) to restore the talonavicular coverage and correct the transverse plane deformity. Stage III (rigid) requires a triple arthrodesis.

Question 61

A 62-year-old man presents with a painful, swollen left hip 5 years after undergoing a primary total hip arthroplasty (THA) with a metal-on-polyethylene bearing. Radiographs reveal no evidence of loosening or osteolysis. Aspiration yields cloudy, non-purulent fluid with a normal white blood cell count. Laboratory evaluation reveals a significantly elevated serum cobalt level with a relatively normal serum chromium level. What is the most likely diagnosis?





Explanation

The clinical presentation is classic for 'trunnionosis', which involves mechanically assisted crevice corrosion (MACC) at the head-neck junction of a total hip arthroplasty. This occurs even with metal-on-polyethylene bearings, specifically at the modular junction. It characteristically produces elevated serum cobalt levels that are out of proportion to chromium levels, leading to an adverse local tissue reaction (ALTR). Infection would typically show an elevated WBC count in the aspirate. Polyethylene wear typically causes osteolysis, which is not seen here.

Question 62

Which of the following clinical scenarios is the most widely accepted indication for prophylactic in situ pinning of the contralateral, asymptomatic hip in a patient with a slipped capital femoral epiphysis (SCFE)?





Explanation

Prophylactic pinning of the contralateral hip is generally recommended for patients with underlying endocrine or metabolic disorders (such as hypothyroidism, panhypopituitarism, or renal osteodystrophy) due to an exceedingly high risk (up to 100% in some series) of bilateral involvement. Routine prophylactic pinning in idiopathic SCFE remains controversial, though it is sometimes considered in very young patients (e.g., <10 years old) or those likely to be non-compliant.

Question 63

A 55-year-old man undergoes a C3-C7 posterior cervical laminectomy and instrumented fusion for cervical myelopathy. On postoperative day 2, he develops profound new weakness in his right deltoid and biceps (muscle grade 2/5) but denies any new sensory changes, and his myelopathic symptoms in the lower extremities are improving. What is the most widely accepted primary pathophysiologic mechanism for this specific complication?





Explanation

The patient is experiencing a C5 nerve root palsy, a known complication occurring in roughly 5-10% of patients following cervical decompression (especially laminectomy). The most widely accepted mechanism is the posterior drift or 'shift' of the spinal cord following decompression, which tethers the C5 nerve root. The C5 root is particularly vulnerable due to its short, transverse course and the lack of redundant length compared to lower cervical roots. Most cases recover spontaneously over several months with observation and physical therapy.

Question 64

In the Young-Burgess classification of pelvic ring injuries, which of the following specifically differentiates an Anteroposterior Compression (APC) Type III injury from an APC Type II injury?





Explanation

In the Young-Burgess classification, APC II injuries involve disruption of the symphysis pubis (or anterior ring) along with the anterior sacroiliac, sacrotuberous, and sacrospinous ligaments. The posterior sacroiliac ligaments remain intact, providing some rotational instability but maintaining vertical stability. In an APC III injury, the posterior sacroiliac ligaments are completely disrupted, resulting in both rotational and vertical instability (a completely unstable hemipelvis).

Question 65

A 30-year-old male sustains a high radial nerve palsy following a mid-shaft humerus fracture. After 9 months with no electromyographic evidence of recovery, tendon transfers are planned. Using the classic Brand transfer for radial nerve palsy, which of the following tendon transfers is primarily used to restore thumb extension?





Explanation

The classic Brand transfer for radial nerve palsy utilizes the Pronator Teres (PT) to Extensor Carpi Radialis Brevis (ECRB) for wrist extension, the Flexor Carpi Radialis (FCR) to the Extensor Digitorum Communis (EDC) for finger extension, and the Palmaris Longus (PL) to the Extensor Pollicis Longus (EPL) for thumb extension. Note that the FCR is transferred to the EPL in some modifications (like the modified Boyes transfer), but the standard Brand transfer uses PL to EPL.

Question 66

A 22-year-old overhead athlete presents with recurrent anterior shoulder instability. Magnetic resonance imaging (MRI) reveals a 'J-sign'. This specific radiographic finding corresponds to which of the following anatomical injuries?





Explanation

The 'J-sign' on an MRI (particularly an MR arthrogram) of the shoulder is indicative of a Humeral Avulsion of the Glenohumeral Ligament (HAGL) lesion. This lesion occurs when the inferior glenohumeral ligament (IGHL) is avulsed from its attachment on the anatomic neck of the humerus. Normal anatomy shows a U-shaped axillary pouch; when the humeral attachment is torn, contrast leaks inferiorly, forming a J-shape.

Question 67

When differentiating an osteoblastoma from an osteoid osteoma based on histological and clinical features, which of the following characteristics is definitive for an osteoblastoma?





Explanation

Osteoid osteoma and osteoblastoma are histologically very similar (both contain interlacing trabeculae of osteoid surrounded by osteoblasts). The primary differentiating factor is size: osteoblastomas are defined as being greater than 2 cm in diameter, while osteoid osteomas are less than 2 cm (often <1 cm). Additionally, osteoblastomas tend to occur in the posterior elements of the spine, are less likely to have a thick sclerotic reactive rim, and the pain is typically progressive and less dramatically responsive to NSAIDs compared to osteoid osteoma.

Question 68

A 25-year-old athlete sustains a hyper-plantarflexion injury to the midfoot. Radiographs show a 'fleck sign' at the base of the second metatarsal. The primary ligament disrupted in this injury normally connects which two osseous structures?





Explanation

The 'fleck sign' represents an avulsion fracture of the base of the second metatarsal at the attachment of the Lisfranc ligament. The Lisfranc ligament is an interosseous ligament that connects the lateral aspect of the medial cuneiform to the medial aspect of the base of the second metatarsal. It is critical for the stability of the midfoot.

Question 69

According to the Ponseti method for the treatment of idiopathic clubfoot, the initial casting phase prioritizes the correction of the cavus deformity. Which specific manipulation is required to achieve this correction?





Explanation

The deformities in clubfoot are remembered by the acronym CAVE (Cavus, Adductus, Varus, Equinus). Cavus is the first deformity to be corrected. It is caused by a plantarflexed first ray relative to the hindfoot. To correct this, the first ray must be elevated, which effectively supinates the forefoot so that it is in alignment with the supinating hindfoot. Pronating the forefoot (a common mistake) worsens the cavus.

Question 70

A 45-year-old male presents with chronic back pain and new-onset radicular symptoms in his right leg. Radiographs reveal an isthmic spondylolisthesis with a 25% slip of L5 on S1. If this patient has a single radiculopathy corresponding to the most commonly affected nerve root in this specific condition, which nerve root is involved?





Explanation

In isthmic spondylolisthesis at L5-S1, the defect is in the pars interarticularis (the isthmus). The slippage of L5 forward on S1 causes narrowing of the L5-S1 neural foramen. Additionally, hypertrophic fibrocartilaginous tissue at the pars defect further compromises the foramen, leading to compression of the exiting L5 nerve root. This contrasts with a central disc herniation at L5-S1, which would typically compress the traversing S1 nerve root.

Question 71

In 2013, the American Society for Bone and Mineral Research (ASBMR) updated the criteria for diagnosing atypical femur fractures (AFF) associated with long-term bisphosphonate use. Which of the following is NOT considered a major criterion for the diagnosis of an AFF?





Explanation

According to the ASBMR criteria, to be defined as an atypical femur fracture, all major criteria must be met. These include: 1) location anywhere from just distal to the lesser trochanter to just proximal to the supracondylar flare; 2) associated with no or minimal trauma; 3) transverse or short oblique configuration; 4) complete fractures extend through both cortices and may be associated with a medial spike; incomplete fractures involve only the lateral cortex; 5) non-comminuted or minimally comminuted. Significant comminution is a negative criterion (i.e., its presence argues against an AFF).

Question 72

During a primary posterior-stabilized total knee arthroplasty (TKA), the surgeon checks the flexion and extension gaps. The knee achieves full, symmetric extension but is significantly tight in flexion, preventing achieving 90 degrees of flexion. What is the most appropriate step to balance the knee?





Explanation

When a TKA is tight in flexion but balanced and full in extension, the flexion gap needs to be enlarged without altering the extension gap. Decreasing the femoral component size (which resects more posterior femoral condyle with an anterior referencing system, or shifts the component anteriorly with a posterior referencing system while using a smaller size) effectively increases the flexion gap. Increasing the posterior slope of the tibia can also increase the flexion gap but alters tibial geometry and is limited by component constraints. Releasing the PCL is not the answer because it is a posterior-stabilized TKA, so the PCL has already been resected. Recutting the distal femur affects only the extension gap.

Question 73

A 35-year-old manual laborer presents with chronic, progressive wrist pain. Radiographs demonstrate advanced Kienbock's disease. According to the Lichtman classification, what specific radiographic finding distinguishes Stage IIIA from Stage IIIB?





Explanation

In the Lichtman classification of Kienbock's disease (avascular necrosis of the lunate), Stage III represents lunate collapse. It is subdivided into IIIA and IIIB. Stage IIIA exhibits lunate collapse but normal carpal alignment. Stage IIIB exhibits lunate collapse along with fixed scaphoid rotary subluxation (often indicated by a cortical ring sign) and a decrease in carpal height ratio, signifying carpal instability. Stage IV includes secondary radiocarpal or midcarpal arthritis.

Question 74

A patient is evaluated for a knee injury using the dial test in the prone position. At 30 degrees of knee flexion, the injured leg shows 15 degrees of increased external rotation compared to the normal leg. At 90 degrees of knee flexion, the external rotation is symmetric between both legs. What is the most likely diagnosis?





Explanation

The dial test assesses the integrity of the posterolateral corner (PLC) and the posterior cruciate ligament (PCL). An increase in external rotation of >10 degrees compared to the contralateral side is considered positive. If the test is positive at 30 degrees of flexion but normal at 90 degrees, it indicates an isolated PLC injury (the intact PCL limits external rotation at 90 degrees). If the test is positive at both 30 and 90 degrees, it indicates a combined PLC and PCL injury.

Question 75

Secondary fracture healing, which involves the formation of an intermediate cartilaginous callus, relies heavily on endochondral ossification. Which of the following mechanical environments most strongly promotes this type of bone healing?





Explanation

Secondary fracture healing occurs via endochondral ossification, where a cartilage template is first formed and then replaced by bone (callus formation). This process is stimulated by relative stability, which allows for controlled micromotion at the fracture site. Techniques like intramedullary nailing or bridge plating provide relative stability. Absolute stability (e.g., rigid compression plating) eliminates micromotion and promotes primary bone healing via cutting cones, without callus formation.

Question 76

A 55-year-old woman presents with adult acquired flatfoot deformity (AAFD) secondary to posterior tibial tendon dysfunction. On examination, she has a flexible hindfoot valgus and is unable to perform a single-leg heel rise on the affected side. Radiographs confirm a flexible pes planovalgus without severe arthritic changes. What is the most appropriate primary surgical intervention for this stage of disease?





Explanation

The patient has Stage II AAFD (flexible deformity, inability to perform single heel rise). The standard surgical treatment for Stage II disease involves soft tissue reconstruction (FDL transfer to the navicular to substitute for the dysfunctional PTT) combined with a bony procedure to correct the biomechanics and protect the transfer, most commonly a medial displacement calcaneal osteotomy (MDCO). Triple arthrodesis is reserved for Stage III (rigid deformity or significant arthritis).

Question 77

In a classic Galeazzi fracture-dislocation (fracture of the distal third of the radius with disruption of the distal radioulnar joint), the radius often undergoes shortening and angulation. Which muscle represents the primary deforming force responsible for shortening of the radius in this injury?





Explanation

In a Galeazzi fracture, the distal radial fragment is subjected to several deforming forces. The primary deforming force causing shortening of the radius is the Brachioradialis, which pulls the distal fragment proximally. The pronator quadratus causes volar displacement and rotation of the distal fragment. Due to these strong deforming forces, Galeazzi fractures are considered 'fractures of necessity' in adults and require open reduction and internal fixation.

Question 78

An infant is being treated with a Pavlik harness for developmental dysplasia of the hip (DDH). The harness is adjusted, but the anterior straps are inadvertently pulled too tight, placing the hips in excessive flexion (greater than 120 degrees). What is the most likely neurologic complication resulting from this specific positioning error?





Explanation

The Pavlik harness must be carefully adjusted. Excessive flexion of the hips (anterior straps too tight, >120 degrees of flexion) compresses the femoral nerve against the inguinal ligament, leading to an iatrogenic femoral nerve palsy. The clinical sign is an absence of active knee extension. Avascular necrosis (AVN) is the most devastating complication overall and is associated with excessive abduction (posterior straps too tight). Sciatic nerve palsy is rare in this context.

Question 79

A 24-year-old male is brought to the emergency department after a high-speed motor vehicle collision where he was wearing a lap belt only. Radiographs of the spine reveal a Chance fracture of L2. Due to the mechanism of this specific spinal injury, the trauma team must maintain a high index of suspicion for which of the following associated injuries?





Explanation

A Chance fracture is a flexion-distraction injury of the spine, classically associated with lap seatbelt use in motor vehicle collisions. The fulcrum of flexion is anterior to the spine (at the abdominal wall), causing severe distraction forces through the posterior and middle columns. This mechanism highly correlates with severe intra-abdominal injuries, particularly hollow viscus injuries (e.g., bowel perforations or mesenteric tears), which are found in up to 40-50% of patients with a Chance fracture.

Question 80

A 28-year-old female undergoes a wide local excision of a slow-growing soft tissue mass adjacent to her knee joint. Histopathology reveals a biphasic tumor with both epithelial and spindle cell components. Molecular testing confirms the diagnosis of synovial sarcoma. Which of the following chromosomal translocations is the hallmark of this specific malignancy?





Explanation

Synovial sarcoma is characterized by the t(X;18)(p11;q11) translocation, which fuses the SYT gene on chromosome 18 with one of the SSX genes (SSX1, SSX2, or SSX4) on the X chromosome. t(11;22) is characteristic of Ewing sarcoma. t(12;16) is found in myxoid liposarcoma. t(2;13) is classic for alveolar rhabdomyosarcoma. t(9;22) is the Philadelphia chromosome seen in chronic myeloid leukemia (and some acute leukemias).

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