Arab Orthopaedic Board MCQs - Part 17

A 12-year-old obese boy presents with acute right groin pain and an inability to bear weight on his right leg, even with crutches. Radiographs confirm a severe Slipped Capital Femoral Epiphysis (SCFE). According to the Loder classification, what is the primary determinant of this patient's high risk for avascular necrosis (AVN)?

During a posterior-stabilized total knee arthroplasty, using a measured resection technique, the surgeon assesses the gaps with trial components. The knee is symmetric and perfectly balanced in extension, but it is symmetrically tight in flexion. What is the most appropriate next step to balance the knee without altering the extension gap?

A 35-year-old male is brought to the ED after a high-speed motorcycle crash. His blood pressure is 70/40 mmHg. Pelvic radiographs reveal an anteroposterior compression (APC) Type III pelvic ring injury with complete disruption of the symphysis and bilateral sacroiliac joints. A massive transfusion protocol is initiated. What is the most appropriate immediate orthopedic intervention?

In the microstructure of normal hyaline articular cartilage, which zone possesses the highest concentration of proteoglycans, the lowest concentration of water, and collagen fibrils that are oriented strictly perpendicular to the articular surface?

A 15-year-old boy presents with distal femur pain. Imaging reveals a destructive metaphyseal lesion with a 'sunburst' periosteal reaction and a Codman's triangle. Core needle biopsy confirms high-grade intramedullary osteosarcoma. Which of the following genetic mutations or translocations is most strongly associated with the pathogenesis of this tumor?

A 25-year-old rugby player presents with an inability to actively flex the distal interphalangeal (DIP) joint of his ring finger after grabbing an opponent's jersey. Radiographs reveal a bony avulsion fragment localized at the level of the proximal interphalangeal (PIP) joint. According to the Leddy and Packer classification, what type of injury is this, and what is the typical status of the vincula?

During an anterior cruciate ligament (ACL) reconstruction, a surgical error results in the femoral tunnel being placed too anteriorly (shallow) in the intercondylar notch. What specific kinematic abnormality will this graft exhibit during knee range of motion?

A 40-year-old male is involved in a severe motor vehicle collision. Cervical spine CT demonstrates a traumatic spondylolisthesis of the axis (Hangman's fracture) with severe anterior angulation and 6 mm of translation of C2 on C3. There is an associated unilateral C2-C3 facet dislocation. According to the Levine-Edwards classification, what is the most appropriate management?

A 55-year-old patient with poorly controlled diabetes mellitus presents with a warm, swollen, and erythematous right foot without an open ulcer. Radiographs demonstrate significant midfoot joint effusion, bone fragmentation, subluxation, and periarticular debris. According to the Eichenholtz classification of Charcot arthropathy, what stage does this represent, and what is the primary treatment?

A 6-week-old female infant undergoes a screening ultrasound for developmental dysplasia of the hip (DDH). The standard coronal view yields an alpha angle of 35 degrees and a beta angle of 85 degrees. According to the Graf classification, what is the diagnosis and the most appropriate next step in management?

A 60-year-old female underwent volar locking plate fixation for a comminuted distal radius fracture. Eight months postoperatively, she returns complaining of a sudden inability to actively flex the interphalangeal joint of her thumb. Which of the following technical errors during the index surgery is the most likely culprit?

A 45-year-old male presents to the ED with severe radicular lower back pain, bilateral lower extremity paresthesias, and saddle anesthesia. An urgent MRI confirms a massive L4-L5 central disc extrusion. A bladder scan is performed to assess for neurogenic urinary retention. What is the widely accepted minimum post-void residual (PVR) volume that is highly suggestive of Cauda Equina Syndrome in this clinical context?

A 55-year-old male who underwent a total hip arthroplasty with a ceramic-on-ceramic bearing surface two years ago now complains of a loud, high-pitched 'squeaking' sound during walking. He denies pain. Which of the following component alignment issues is most consistently implicated in the etiology of this phenomenon?

According to Perren's strain theory, successful fracture healing depends on the deformation limits of different tissues within the fracture gap. What is the maximum interfragmentary strain threshold that permits the formation of lamellar bone (primary bone healing)?

A 30-year-old laborer is diagnosed with a Scaphoid Nonunion Advanced Collapse (SNAC) wrist following an unrecognized scaphoid fracture five years prior. As the degenerative cascade of SNAC progresses through its predictable stages, which of the following joints is characteristically the LAST to develop arthritic changes?

A 24-year-old gymnast sustains a hyper-plantarflexion midfoot injury. Weight-bearing radiographs reveal widening of the interval between the first and second metatarsal bases, alongside a small bony 'Fleck sign'. The critical Lisfranc ligament, which is disrupted in this injury, connects which two specific osseous structures?

A 7-year-old boy presents with a painless limp and is diagnosed with Legg-Calve-Perthes disease in the fragmentation stage. Radiographs reveal that exactly 60% of the lateral pillar of the femoral head maintains its normal radiolucent height. According to the Herring Lateral Pillar Classification, what group is this hip, and what is its prognosis without intervention?

A 30-year-old male sustains a severely comminuted closed fracture of the tibial shaft. He complains of excruciating leg pain that is unresponsive to IV opioids. His blood pressure is 120/80 mmHg. Intracompartmental pressure monitoring is performed. Which of the following measured values represents the most universally accepted absolute threshold indicating the need for emergent four-compartment fasciotomy?

A 65-year-old female with known breast cancer presents with functional, weight-bearing thigh pain. Radiographs demonstrate a purely lytic lesion in the peritrochanteric region of the proximal femur. The lesion spans 50% (1/3 to 2/3) of the cortical diameter. Using Mirels' criteria for impending pathologic fractures, what is her calculated score and the associated clinical recommendation?

A 75-year-old male presents with severe neck pain following a low-energy ground-level fall. Cervical CT demonstrates a displaced Anderson and D'Alonzo Type II odontoid fracture. What distinct anatomical feature of the dens makes this specific fracture pattern highly prone to nonunion, particularly in the elderly population?