1. General Principles & Basic Science MCQs

During the process of secondary fracture healing, the initial cartilaginous soft callus is gradually replaced by a hard woven bone callus. Which of the following cell types is primarily responsible for the production of the initial woven bone via endochondral ossification?

Intermittent, low-dose administration of parathyroid hormone (PTH) analogs, such as teriparatide, is utilized for severe osteoporosis. While continuous elevated PTH causes net bone resorption, intermittent administration primarily stimulates bone formation by directly activating receptors on which cell type?

During primary cortical bone healing via cutting cones, which of the following cell types is located at the very leading edge of the remodeling unit?

A surgeon places a 316L stainless steel screw through a titanium alloy plate to fix a fracture. What type of corrosion is most likely to occur at the interface between the two different metals?

Which of the following geometric modifications to a standard cortical screw will most significantly increase its pullout strength in diaphyseal bone?

In normal articular cartilage, which zone is characterized by the highest concentration of water, the lowest concentration of proteoglycans, and collagen fibers oriented parallel to the joint surface?

According to current prophylactic guidelines, what is the most appropriate perioperative antibiotic regimen for a patient with a known, documented Type I IgE-mediated anaphylactic allergy to penicillin undergoing a primary total knee arthroplasty?

During the controlled descent phase of a barbell squat, the quadriceps muscle lengthens while continuing to generate tension to control the rate of knee flexion. What type of muscle contraction is primarily occurring in the quadriceps?

A 14-year-old patient presents with multiple fragility fractures, hepatosplenomegaly, and progressive cranial nerve palsies. Radiographs show diffusely dense, 'marble-like' bones with absent medullary canals. The primary cellular defect in this condition involves the impairment of which of the following?

Following an inadvertently intravascular injection of bupivacaine during a hematoma block, a patient develops perioral numbness, tinnitus, and generalized seizures. This local anesthetic systemic toxicity (LAST) is primarily mediated by the blockade of which of the following channels in the central nervous and cardiovascular systems?

Which of the following lubrication mechanisms relies primarily on the glycoprotein lubricin (PRG4) to prevent cartilage-to-cartilage contact under conditions of high load and low relative velocity?

A 65-year-old female with severe, T-score -3.5 osteoporosis is started on daily subcutaneous teriparatide therapy. This medication increases bone mineral density primarily through which of the following mechanisms?

During a normal adult walking gait cycle, the peak maximum muscle contraction of the ankle plantar flexors (gastrocnemius-soleus complex) occurs during which specific phase?

Articular cartilage is a complex, avascular tissue structurally divided into four distinct zones. Which of the following best describes the primary characteristics of the deep (radial) zone?

Biofilm formation on orthopedic implants represents a major barrier to eradicating periprosthetic joint infections. During which distinct phase of biofilm development are the offending bacteria most highly resistant to systemic antibiotic therapy?

Denosumab has emerged as an effective medical therapy for unresectable or recurrent giant cell tumor of bone (GCTB). What is the exact molecular mechanism of action of this drug in the treatment of GCTB?

Primary (direct) bone healing relies on Haversian remodeling across the fracture site without the formation of an intermediate cartilaginous or fibrous callus. Which of the following mechanical conditions is an absolute prerequisite for primary bone healing to occur?

A 5-year-old boy presents with progressive bowing of his legs, a waddling gait, and short stature. Laboratory evaluation reveals normal serum calcium, critically low serum phosphate, normal parathyroid hormone (PTH), and markedly elevated alkaline phosphatase. Genetic testing identifies a mutation in the PHEX gene. What is the primary pathophysiologic mechanism driving this patient's metabolic bone disease?