Arab Orthopaedic Board MCQs - Part 29

A 6-year-old boy presents with a Gartland type III supracondylar humerus fracture. On initial presentation, his hand is 'pink and pulseless', with brisk capillary refill but an absent radial pulse. He is taken immediately to the operating room for closed reduction and percutaneous pinning. Post-operatively in the recovery room, his hand remains pink with brisk capillary refill, but the radial pulse remains absent. What is the most appropriate next step in management?

A 45-year-old active man who underwent a total hip arthroplasty (THA) with a ceramic-on-ceramic bearing 2 years ago presents complaining of an audible, high-pitched squeak from his hip when he bends to tie his shoes. Radiographs reveal an acetabular cup inclination angle of 60 degrees. What is the primary pathophysiological mechanism responsible for this squeaking?

A 14-year-old girl is undergoing a posterior spinal fusion for a Lenke type 1A adolescent idiopathic scoliosis. During the rod rotation maneuver, motor evoked potentials (MEPs) drop by 80% bilaterally in the lower extremities, while somatosensory evoked potentials (SSEPs) remain at baseline. The anesthesiologist confirms that the mean arterial pressure (MAP) is currently 90 mmHg and no paralytics have been administered. What is the most appropriate immediate surgical step?

A 25-year-old man presents with a symptomatic proximal pole scaphoid non-union and is scheduled for structural bone grafting. The high rate of osteonecrosis in the proximal pole is due to its precarious blood supply. The primary vascular supply to the proximal pole of the scaphoid is derived from which of the following?

A 22-year-old collegiate football player presents with midfoot pain after another player fell on his heel while his foot was plantarflexed. Physical examination reveals plantar ecchymosis. Weight-bearing radiographs demonstrate 2 mm of widening between the 1st and 2nd metatarsal bases. Anatomically, the native Lisfranc ligament connects which of the following two structures?

During the process of endochondral ossification, growth plate chondrocytes undergo a period of hypertrophy before programmed cell death and subsequent vascular invasion. Which of the following collagen types is predominantly and specifically synthesized by these hypertrophic chondrocytes to facilitate matrix mineralization?

A 30-year-old recreational athlete sustains an acute anterior cruciate ligament (ACL) tear. He is discussing graft options with his surgeon, specifically comparing bone-patellar tendon-bone (BPTB) autograft and hamstring autograft. Which of the following is an established long-term functional advantage of BPTB autograft over hamstring autograft?

A 3-month-old infant is being treated with a Pavlik harness for developmental dysplasia of the hip (DDH). At the two-week follow-up, the mother reports the infant has stopped kicking her left leg. Examination reveals absent active hip and knee flexion on the left, but ankle and toe movements remain completely intact. What is the most likely iatrogenic cause of this presentation?

A 45-year-old male is brought to the trauma bay in hemorrhagic shock after a high-speed motorcycle crash. Pelvic radiographs demonstrate an Anteroposterior Compression Type III (APC III) injury. Which of the following ligamentous complexes are completely disrupted in this specific injury pattern?

During a primary total knee arthroplasty (TKA), after making the standard bony cuts and placing the trial components, the surgeon assesses the gaps. The knee is perfectly balanced in full extension, but the joint is overly tight and fails to reach full flexion. Which of the following is the most appropriate surgical step to balance this knee?

A 24-year-old woman presents with worsening knee pain. Radiographs reveal an eccentric, lytic epiphyseal lesion extending to the subchondral bone of the distal femur. Biopsy reveals neoplastic mononuclear cells interspersed with numerous reactive multinucleated giant cells. If the tumor is deemed surgically unresectable, medical management with Denosumab is indicated. What is the precise molecular target of this medication?

A 55-year-old woman requires open reduction and internal fixation of a displaced volar Barton fracture. The surgeon elects to use the standard volar Henry approach to the distal radius. Which of the following anatomical intervals is utilized during the superficial dissection of this approach?

A 45-year-old man feels an acute pop in the back of his knee while performing a deep squat. MRI demonstrates a complete radial tear at the posterior root of the medial meniscus, with 4 mm of medial meniscal extrusion seen on the coronal sequence. Biomechanically, this specific injury is most functionally equivalent to which of the following?

During fracture fixation, achieving adequate screw purchase is paramount. Which of the following structural parameters has the greatest mathematical influence on the direct pull-out strength of a cortical bone screw?

A 9-year-old girl presents with left groin pain and a limp. Examination reveals obligate external rotation of the left hip during passive flexion. Radiographs confirm a severe left slipped capital femoral epiphysis (SCFE). Which of the following patient factors represents the strongest recognized indication for prophylactic in-situ pinning of her contralateral, asymptomatic right hip?

A 28-year-old male construction worker falls from a ladder and sustains a displaced fracture of the talar neck. Radiographs demonstrate dislocation of both the subtalar and tibiotalar joints. According to the Hawkins classification, what is the approximate expected rate of avascular necrosis (AVN) of the talar body for this specific injury?

A 65-year-old man presents with deteriorating handwriting, dropping objects, and gait instability. On physical examination, tapping the brachioradialis tendon at the distal radius elicits paradoxical flexion of the fingers without the normal elbow flexion or forearm supination. This specific localizing sign is known as:

A 42-year-old weekend warrior sustains an acute Achilles tendon rupture 4 cm proximal to the calcaneal insertion. This area is notoriously hypovascular and often referred to as the 'watershed area' of the Achilles tendon. Which artery provides the predominant vascular supply to this specific watershed region?

Romosozumab is a recently FDA-approved, highly effective anabolic agent for the treatment of severe osteoporosis. It promotes massive increases in bone mineral density by binding to and inhibiting which of the following molecular targets, thereby upregulating the Wnt/β-catenin signaling pathway in osteoblasts?

A 35-year-old new mother presents with severe pain over the radial styloid. Finkelstein's test is markedly positive. After failing conservative management, she is scheduled for surgical release of the first dorsal compartment (De Quervain's tenosynovitis). Which of the following nerve branches is at the highest risk of iatrogenic injury during the superficial surgical dissection of this procedure?

A 55-year-old male presents with progressive clumsiness in his hands and a broad-based gait. Imaging reveals Ossification of the Posterior Longitudinal Ligament (OPLL) in the cervical spine. Which of the following radiographic findings is a relative contraindication to performing a cervical laminoplasty alone in this patient?

A 68-year-old female experiences recurrent posterior dislocations after a primary right total hip arthroplasty via a posterior approach. CT imaging demonstrates the acetabular cup is placed in 45 degrees of abduction and 5 degrees of retroversion. The femoral stem is in 10 degrees of anteversion. What is the primary cause of her instability?

Nine months after undergoing open reduction and internal fixation of a supracondylar femur fracture with a lateral locking plate, a 45-year-old male presents with persistent thigh pain. Radiographs reveal an intact construct with a 5 mm fracture gap and absent callus formation. What is the most likely mechanical cause of this atrophic nonunion?

During a Zone II flexor tendon repair, preserving the biomechanical advantage of the flexor sheath is critical to maintain functional excursion and limit bowstringing. Which two pulleys are most critical to preserve or reconstruct?

A 14-year-old boy presents with knee pain. MRI shows an expansile, multi-cystic lesion in the distal femur metaphysis with multiple fluid-fluid levels. Core needle biopsy reveals blood-filled spaces. Which histologic feature most reliably differentiates telangiectatic osteosarcoma from an aneurysmal bone cyst (ABC) in this setting?

In a 7-year-old boy diagnosed with Legg-Calve-Perthes disease, radiographs demonstrate that the lateral pillar of the femoral head maintains 65% of its original height. According to the Herring Lateral Pillar Classification, which group does this represent?

The posterior cruciate ligament (PCL) provides primary restraint to posterior tibial translation. During a physical examination or biomechanical testing, at which degree of knee flexion is the anterolateral (AL) bundle of the PCL most taut?

Bone morphogenetic proteins (BMPs) initiate osteogenesis by binding to serine-threonine kinase receptors. Which intracellular signaling molecules are directly phosphorylated by the BMP receptor complex and subsequently translocate to the nucleus to regulate gene expression?

A 55-year-old male with poorly controlled diabetes mellitus presents with a deformed, non-tender midfoot. Radiographs reveal coalescing bone fragments, absorption of fine bone debris, and early fusion of large fragments. According to the Eichenholtz classification of Charcot arthropathy, what stage is currently demonstrated?

Which of the following scenarios represents an absolute indication for operative fixation of a 'floating shoulder' (ipsilateral fractures of the clavicle and scapular neck)?

A 65-year-old male presents with bilateral leg pain that worsens after walking 2 blocks. Physical examination shows absent Achilles reflexes but intact knee reflexes, with palpable pedal pulses. Which of the following historical findings most reliably differentiates neurogenic claudication from vascular claudication?

During a primary total knee arthroplasty, the surgeon performs a trial reduction and observes lateral tracking of the patella. Which of the following technical errors regarding component positioning is most likely responsible for this finding?

Congenital pseudarthrosis of the tibia (CPT) classically presents with anterolateral bowing of the tibia and subsequent fracture. Which systemic condition is most strongly associated with CPT?

A patient with long-standing scaphoid nonunion presents with progressive wrist pain. Radiographs demonstrate early arthritic changes characteristic of Scaphoid Nonunion Advanced Collapse (SNAC). Which joint is typically the first to develop degenerative changes in the SNAC progression?

A 12-year-old active boy complains of vague knee pain and occasional catching. Radiographs reveal an osteochondritis dissecans (OCD) lesion. What is the single most common anatomic location for an OCD lesion in the knee?

A 28-year-old male sustains a severe hyperdorsiflexion injury to the ankle. Radiographs reveal a displaced talar neck fracture with subluxation of the subtalar joint. The tibiotalar and talonavicular joints remain congruent. According to the Hawkins classification, what is the stage of this injury and its approximate associated risk of avascular necrosis (AVN)?

Articular cartilage is a highly specialized connective tissue. While water accounts for 65-80% of its wet weight, the remaining solid matrix (dry weight) is primarily composed of collagens and proteoglycans. Which of the following best represents the approximate composition of the dry weight of adult hyaline articular cartilage?

A 15-year-old male presents with a painful, swollen mass in his proximal humerus. Biopsy demonstrates uniform, small blue round cells with PAS-positive cytoplasmic glycogen. Genetic analysis is requested to confirm the diagnosis. Which of the following chromosomal translocations is most characteristic of Ewing sarcoma?

A 6-year-old boy presents to the emergency department after falling off monkey bars. Radiographs demonstrate a completely displaced, extension-type supracondylar humerus fracture with no bony contact between the proximal and distal fragments. Upon closed reduction in the operating room, the surgeon notes the medial periosteal hinge is intact. According to the Gartland classification, what type of fracture is this?

In the Young-Burgess classification, an Anteroposterior Compression (APC) Type II pelvic ring injury results in the 'open book' deformity. This is characterized by diastasis of the symphysis pubis and rupture of the anterior sacroiliac, sacrotuberous, and sacrospinous ligaments. Which critical ligamentous complex remains INTACT in an APC II injury, thereby preventing vertical instability?

A 65-year-old man presents with a painful total knee arthroplasty 2 years after index surgery. Joint aspiration reveals a synovial WBC count of 3,500 cells/uL with 75% PMNs. Which of the following synovial fluid biomarkers is most specific for diagnosing a periprosthetic joint infection by targeting an antimicrobial peptide released by neutrophils?

A 14-year-old boy presents with an ankle injury after falling while skateboarding. Radiographs show a Salter-Harris III fracture of the anterolateral distal tibia. What is the mechanism of injury and the deforming force acting on this fracture fragment?

A 40-year-old woman sustains a 'terrible triad' injury of the elbow. During surgical reconstruction, what is the generally accepted sequence of repair to best restore elbow stability?

A patient demonstrates increased external rotation of the tibia at 30 degrees of knee flexion, but symmetrical external rotation at 90 degrees of knee flexion. Which structure is most likely injured?

A patient sustains a traumatic spondylolisthesis of the axis (Hangman's fracture). Imaging shows angulation with minimal translation, and the fracture gap widens upon cervical traction. According to the Levine-Edwards classification, what type of fracture is this, and what is the appropriate initial management?

A 32-year-old female presents with a lytic, eccentrically located epiphyseal lesion in the proximal tibia. Biopsy reveals mononuclear cells and multinucleated giant cells. Which of the following is the true neoplastic cell component and its characteristic receptor expression?

In a Scaphoid Nonunion Advanced Collapse (SNAC) pattern of wrist arthritis, which of the following joints is characteristically spared from degenerative changes even in advanced stages?

Which of the following ligaments provides the primary stabilization to the Lisfranc joint complex?

In total hip arthroplasty, the phenomenon where a hard third body (such as a bone fragment or bone cement) becomes embedded in the polyethylene liner and subsequently scratches the femoral head is best described as what type of wear?

A 6-week-old infant is being treated with a Pavlik harness for developmental dysplasia of the hip (DDH). The parents report that the child has stopped kicking the affected leg. On examination, the knee lacks active extension, but ankle motion is intact. What is the most likely cause?

A 25-year-old male is brought to the emergency department after a motorcycle collision with a hemodynamically unstable suspected pelvic ring injury. A circumferential pelvic binder is to be applied. What is the correct anatomical landmark to center the binder for optimal reduction of pelvic volume?

A 55-year-old female with a metal-on-metal total hip arthroplasty presents with groin pain. MRI reveals a large cystic mass around the hip joint. Histopathology of the periprosthetic tissue is most likely to show which of the following characterized by ALVAL (Aseptic Lymphocyte-Dominated Vasculitis-Associated Lesion)?

A 22-year-old rugby player undergoes evaluation for recurrent anterior shoulder instability. Diagnostic arthroscopy reveals a large Hill-Sachs lesion that 'engages' the anterior glenoid rim when the arm is placed in abduction and external rotation. The glenoid bone loss is estimated at 10%. Which of the following surgical procedures is most appropriate to address the Hill-Sachs lesion in conjunction with a Bankart repair?

A 68-year-old male complains of bilateral leg pain that worsens after walking two blocks. The pain is relieved by sitting or leaning forward over a shopping cart. He states that riding a stationary bicycle does not provoke the pain. Examination reveals intact distal pulses. What is the most likely diagnosis?

In a patient diagnosed with high-grade intramedullary osteosarcoma, which of the following factors is considered the most significant prognostic indicator for long-term survival?

A 30-year-old carpenter lacerates his volar index finger at the level of the proximal phalanx. Which flexor tendon zone is involved, and what is a defining characteristic of this zone?

When comparing operative versus non-operative management of acute Achilles tendon ruptures utilizing modern early functional rehabilitation protocols, which of the following statements is most accurate regarding clinical outcomes?

According to Perren's strain theory of bone healing, primary bone healing (direct remodeling without callus) will only occur if the interfragmentary strain is below what threshold?

A 12-year-old boy presents with a left-sided Slipped Capital Femoral Epiphysis (SCFE) and undergoes in situ pinning. Prophylactic pinning of the contralateral right hip is most strongly indicated in which of the following scenarios?

A 45-year-old pedestrian is struck by a motor vehicle and sustains a varus-directed force to the knee. Radiographs reveal a medial tibial plateau fracture with depression. According to the Schatzker classification, what type of fracture is this, and what is the most critical associated complication to monitor for?