1. General Principles & Basic Science MCQs

A 4-year-old boy presents with refusal to walk, bleeding gums, and petechiae. Radiographs reveal a densely sclerotic metaphyseal line and a lucent zone immediately diaphyseal to it. A deficiency in a vitamin required for which of the following cellular processes is the likely cause?

A 72-year-old male presents with increasing hat size, hearing loss, and bowing of his tibiae. Radiographs show mixed lytic and sclerotic lesions. The primary cellular defect in this disease process is localized to which of the following?

Bone morphogenetic proteins (BMPs) are used clinically to augment bone healing. Which specific intracellular signaling molecules are directly phosphorylated by activated BMP receptors?

A neonate is diagnosed with malignant infantile osteopetrosis. The defective gene most commonly associated with this autosomal recessive condition encodes for which of the following?

The slope of the linear elastic region of a material's stress-strain curve represents which of the following biomechanical properties?

What is the most abundant non-collagenous protein found in the extracellular matrix of mature bone?

A 40-year-old patient presents with a swollen, painful knee. Synovial fluid analysis reveals a WBC count of 85,000 cells/mcL with 92% polymorphonuclear leukocytes. Glucose level in the fluid is markedly lower than serum levels. What is the most likely diagnosis?

A modular total hip arthroplasty fails due to micro-motion at the head-neck taper junction, leading to wear debris and local tissue reaction. Which type of corrosion primarily occurs as a result of this mechanical disruption of the passivation layer?

Continuous endogenous secretion of parathyroid hormone (PTH) primarily stimulates osteoclastogenesis by binding directly to receptors on which of the following cells?

A 68-year-old female, who has been on alendronate for 12 years, presents with a 3-month history of insidious, dull aching pain in her left thigh, aggravated by weight-bearing. She denies any specific trauma. Physical examination reveals tenderness over the lateral aspect of her proximal femur. Radiographs show significant cortical thickening of the left subtrochanteric femur with a small, incomplete transverse lucency in the lateral cortex. What is the most appropriate next step in management?

Sclerostin is a key regulatory protein in bone metabolism targeted by novel osteoporosis medications. Which of the following best describes its mechanism of action in reducing bone formation?

In orthopedic biomechanics, what term describes the phenomenon where a viscoelastic material (like a ligament) demonstrates a continuous increase in strain over time when subjected to a constant load?

A 5-year-old boy presents with a limp, fever, and refusal to bear weight on his right leg. According to the Kocher criteria, which combination of clinical and laboratory findings yields the highest probability of septic arthritis of the hip?

A 4-year-old girl refuses to bear weight on her left leg. She has a temperature of 38.6°C (101.5°F), an ESR of 45 mm/hr, a serum WBC count of 14,000/mm3, and refuses to move the hip. According to the Kocher criteria, what is the probability that she has septic arthritis?

In a patient with late aseptic loosening of a cemented total knee arthroplasty, which biological pathway is most directly responsible for the macrophage-induced periprosthetic osteolysis?

Bone morphogenetic proteins (BMPs) play a crucial role in bone healing. Which specific signaling pathway do BMPs primarily utilize to exert their osteoinductive effect?

During the repair of a zone II flexor tendon laceration in the index finger, a surgeon meticulously preserves specific portions of the flexor tendon sheath to prevent biomechanical failure and bowstringing. Which two annular pulleys are the most critical to preserve?

A surgeon treats a severely comminuted midshaft femur fracture using a locked intramedullary nail, achieving relative stability. By which physiological mechanism will this fracture primarily heal?