1. General Principles & Basic Science MCQs

Sclerostin, a key negative regulator of bone formation targeted by drugs like romosozumab, exerts its effect by binding to LRP5/6 and inhibiting which of the following pathways?

According to the Sunderland classification of nerve injuries, a third-degree injury involves disruption of the axon and which of the following supporting structures?

A patient is prescribed a bisphosphonate for osteoporosis. At the cellular level, nitrogen-containing bisphosphonates (e.g., alendronate) inhibit osteoclast function primarily by targeting which of the following enzymes?

The primary structural component of articular cartilage is Type II collagen, but its compressive stiffness and load-bearing capacity are primarily provided by the osmotic swelling pressure of which molecule?

Which of the following orthopedic implant materials has a modulus of elasticity most similar to that of cortical bone, thereby minimizing stress shielding?

In the process of bone remodeling, osteoclasts create an acidic microenvironment in the resorption pit by actively pumping protons. Which enzyme is critical for generating these protons within the osteoclast cytoplasm?

A 45-year-old patient undergoes revision total hip arthroplasty. The surgeon utilizes a titanium alloy femoral stem and a cobalt-chromium femoral head. Over time, the release of metal ions at the modular head-neck junction leads to adverse local tissue reactions. Which of the following electrochemical processes is most primarily responsible for this degradation due to the contact of dissimilar metals?

According to Perren's strain theory of bone healing, different types of tissues can tolerate varying amounts of strain before failing. Which of the following represents the maximum tissue strain tolerated by lamellar bone?

Bone Morphogenetic Protein-2 (BMP-2) is utilized clinically to enhance spinal fusion and fracture healing. Upon binding to its cell surface receptor, BMP-2 primarily initiates intracellular osteogenic signaling through which of the following pathways?

A surgeon uses a stainless steel screw through a titanium plate for internal fixation of a diaphyseal femur fracture.

What type of corrosion is most likely to occur due to this construct?

In the process of secondary bone healing following a diaphyseal fracture, which specific phase is characterized by the peak of angiogenesis, maximum tissue cellularity, and the replacement of soft cartilaginous callus by hard woven bone?

Which of the following biomechanical material properties is represented by the total area under the stress-strain curve up to the point of failure?

In healthy articular cartilage, which zone is characterized by the highest concentration of water and collagen fibers that are oriented strictly parallel to the joint surface?

A 4-year-old boy presents with progressive severe bowing of his lower extremities and a waddling gait. Laboratory tests reveal normal serum calcium, significantly low serum phosphate, normal parathyroid hormone (PTH), and elevated alkaline phosphatase. What is the most likely genetic mutation responsible for this condition?

In the pathogenesis of periprosthetic joint infection, biofilm formation provides bacteria with a physical barrier against host defenses and antibiotics. What is the primary extracellular polymeric substance produced by Staphylococcus epidermidis to facilitate this structural adhesion?