1. General Principles & Basic Science MCQs

In total joint arthroplasty, the phenomenon where microscopic asperities on the surface of an implant cold-weld together and are subsequently torn away during continuous motion is classified as which type of wear?

The kinetic energy transferred to tissues by a ballistic projectile is mathematically related to the mass of the bullet and its velocity. If the velocity of a bullet is doubled while the mass remains constant, the kinetic energy transferred increases by a factor of:

During normal human gait, the center of gravity undergoes sinusoidal vertical displacements. Which of the following mechanisms (a primary determinant of gait) acts during midstance to minimize the maximum vertical height of the center of gravity, thereby reducing energy expenditure?

According to the Sunderland classification of peripheral nerve injuries, which of the following best characterizes a third-degree nerve injury?

Bone morphogenetic proteins (BMPs) are extensively used in orthopedics for their osteoinductive properties. Which of the following best describes the intracellular signaling pathway activated directly upon BMP binding to its cell surface receptor?

Articular cartilage relies on a specific structural organization to resist load and shear forces. Which collagen type provides the primary tensile strength of articular cartilage, and in which histologic zone is it found in the highest concentration?

A 3-year-old unimmunized child presents with a swollen, erythematous knee and a fever of 39°C. Arthrocentesis yields cloudy fluid with a WBC count of 85,000 cells/µL. Gram stain reveals Gram-negative coccobacilli. Which of the following is the most likely causative organism, and what is the optimal empiric antibiotic therapy?

A 45-year-old male undergoes tendon lengthening. Which viscoelastic property describes the continuous increase in length of the tendon over time under a constant load?

Recombinant human bone morphogenetic protein-2 (rhBMP-2) is approved for use in anterior lumbar interbody fusion (ALIF). What is the FDA-approved carrier for rhBMP-2 in this procedure?

A 35-year-old female presents with a lytic epiphyseal lesion of the distal femur. Biopsy confirms a Giant Cell Tumor (GCT) of bone. If medical therapy is initiated, which molecular pathway is targeted by the drug of choice?

Articular cartilage is highly specialized to resist compressive forces. In which zone of articular cartilage are the type II collagen fibers oriented perpendicular to the joint surface?

A 30-year-old carpenter lacerates his flexor digitorum profundus (FDP) and flexor digitorum superficialis (FDS) tendons in "Zone II" of his index finger. Why is this region classically referred to as "no man's land"?

Which type of bone healing occurs under conditions of absolute stability, such as following rigid compression plating of a simple transverse radius fracture?

A hamstring graft used for anterior cruciate ligament reconstruction is subjected to a constant physiological load over time, resulting in a gradual, time-dependent increase in deformation. Which of the following viscoelastic properties does this describe?

A 4-year-old boy presents with profound bowing of the lower extremities and a waddling gait. Laboratory studies reveal normal serum calcium, significantly decreased serum phosphate, elevated alkaline phosphatase, and normal parathyroid hormone levels. What is the most likely genetic mutation responsible for this condition?

Which of the following pharmacological agents acts by primarily binding and inhibiting sclerostin, thereby upregulating the Wnt/beta-catenin signaling pathway to dramatically increase osteoblastic bone formation?

During fracture fixation, a surgeon considers combining stainless steel screws with a titanium plate. Why is this combination strictly avoided in orthopedic surgery?