1. General Principles & Basic Science MCQs

Camurati-Engelmann Disease (Progressive Diaphyseal Dysplasia) is characterized by which of the following clinical and radiographic features?

A 30-year-old man complains of progressively worsening deep bone pain and joint contractures in his right leg. Radiographs display dense, eccentric, undulating cortical hyperostosis along the femur and tibia, classically described as resembling "flowing candle wax." Which gene mutation is primarily associated with this sporadic localized dysplasia?

A 35-year-old male presents with chronic, aching pain and stiffness in his left lower extremity. Radiographs reveal a dense, irregular, eccentric cortical hyperostosis extending linearly along the femoral diaphysis. What is the genetic basis of this disorder?

A 30-year-old man presents with chronic, deep, aching pain in his right thigh and stiffness in his knee. Radiographs reveal an irregular, linear area of cortical thickening running along the medial aspect of the femur, resembling flowing wax. Which gene mutation is classically implicated in the sporadic pathogenesis of this condition?

A 6-year-old boy is brought in for cosmetic evaluation of a right-sided chest wall asymmetry and ipsilateral short, webbed fingers. Examination reveals absence of the sternocostal head of the pectoralis major muscle. Which of the following upper extremity anomalies is most frequently associated with this patient's syndrome?

A 2-week-old infant is diagnosed with bilateral radial agenesis. Unlike many other syndromes with radial deficiencies, the infant has perfectly normal thumbs on both hands. Blood work reveals severe thrombocytopenia. Which of the following best describes the inheritance pattern and implicated gene for this condition?

A neonate is evaluated for bilateral absence of the radius, but uniquely, both thumbs are fully formed and present. Laboratory analysis reveals profound thrombocytopenia. Which genetic anomaly is characteristic of this syndrome?

A 10-year-old boy presents with a short neck, low posterior hairline, and severely limited cervical motion. Radiographs confirm multiple fused cervical vertebrae. Which of the following evaluations is most critical in the initial workup of this patient to rule out a common associated anomaly?

A 35-year-old man complains of chronic dull aching pain and stiffness in his right thigh and knee. Radiographs reveal undulating cortical hyperostosis extending along the femur, resembling dripping candle wax. This disorder is classically associated with loss-of-function mutations in which gene?

A 15-year-old girl is incidentally found to have an expansive, radiolucent, 'ground-glass' lesion in the proximal femur with endosteal scalloping. An incisional biopsy is performed. What is the classic histopathological hallmark of this localized skeletal condition?

A 14-year-old girl presents with a painless, progressive flexion contracture of the proximal interphalangeal (PIP) joint of her right little finger. Passive extension of the PIP joint is possible when the metacarpophalangeal (MCP) joint is held in flexion. Abnormal insertion of which structure is most commonly implicated in this localized condition?

A 3-year-old child presents with a history of recurrent, painful soft tissue swellings in the neck and back that eventually harden. On physical examination, there is noticeable shortening and valgus deviation of the bilateral great toes. Which of the following gene mutations is the primary cause of this condition?

A 35-year-old man presents with progressive joint stiffness and localized pain in his right lower extremity. Radiographs reveal unilateral, undulating cortical hyperostosis along the medial aspect of the femur and tibia, resembling "dripping candle wax." What is the underlying genetic mutation associated with this specific radiologic finding?

A 4-year-old boy presents with disproportionate focal enlargement of his right index and middle fingers, noticeable since birth. The overgrowth is prominent on the volar aspect, causing dorsal deviation, and MRI reveals substantial fibrofatty infiltration along the median nerve territory. Which signaling pathway is typically altered in this focal overgrowth condition?

When planning a corrective osteotomy for a tibial diaphyseal deformity, an opening wedge osteotomy is designed at a level distal to the center of rotation of angulation (CORA). To restore the mechanical axis without creating a secondary translational deformity, what must be incorporated into the surgical plan?

During normal human walking, at which phase of the gait cycle does the gluteus maximus exhibit its peak muscle activity?

According to the principles of deformity correction (Paley's rules), if an osteotomy is performed at a level distinct from the center of rotation of angulation (CORA), but the hinge axis is placed exactly on the CORA, what is the geometric result?

A patient presents with a severe limp secondary to hip osteoarthritis. Gait analysis reveals that during the stance phase on the right leg, the patient significantly leans their trunk laterally over the right hip. Which biomechanical alteration primarily explains the benefit of this compensatory mechanism?

At what phases of the normal gait cycle does the vertical ground reaction force reach its two primary peaks?

According to Paley's rules of deformity correction, an opening wedge osteotomy performed exactly at the Center of Rotation of Angulation (CORA) will result in: