1. General Principles & Basic Science MCQs

A patient with blue sclerae, hearing loss, and multiple childhood fractures is diagnosed with osteogenesis imperfecta. This condition is most commonly caused by a genetic mutation affecting which of the following?

The nutrient artery of a long bone provides the primary blood supply to the medullary cavity and the inner two-thirds of the diaphyseal cortex. In what direction does the blood flow through the cortical bone?

Adult articular cartilage is avascular and alymphatic. By which mechanism do chondrocytes in the deep zone of adult articular cartilage primarily receive their nutrients?

A modular total hip arthroplasty prosthesis develops corrosion at the trunnion-head interface. The repetitive micromotion between the two mechanically loaded parts disrupts the protective oxide layer, leading to corrosion. Which term best describes this phenomenon?

A 5-year-old child presents with bowing of the lower extremities and a waddling gait. Laboratory tests reveal low serum phosphate, normal serum calcium, and elevated alkaline phosphatase. Genetic testing shows a mutation in the PHEX gene. The overproduction of which factor is directly responsible for the renal phosphate wasting in this patient?

A surgeon decides to use a stainless steel screw to secure a titanium alloy plate for a complex femoral shaft fracture. Two years later, the implant fails and the screw is found to be heavily degraded. Which specific type of corrosion is most likely responsible for this failure?

A 65-year-old woman with a history of fragility fractures is started on a nitrogen-containing bisphosphonate (alendronate). At the cellular level, what is the primary molecular target of this medication?

Recombinant human Bone Morphogenetic Protein-2 (rhBMP-2) is utilized during an anterior lumbar interbody fusion. BMPs exert their cellular osteoinductive effects primarily by activating which of the following intracellular signaling pathways?

A researcher is studying the distinct zonal architecture of healthy human articular cartilage. Which zone is characterized by the highest concentration of water and the lowest concentration of proteoglycans?

During revision of a loose total hip arthroplasty, periprosthetic tissue is retrieved. Histological analysis reveals abundant macrophages with phagocytosed polyethylene particles. Which cytokine is primarily responsible for initiating the cascade that leads to osteoclast activation and aseptic loosening in this scenario?

A patient undergoes an ACL reconstruction with a hamstring autograft. The graft is pre-tensioned on a board before implantation. Over a period of 20 minutes under a constant load, the graft demonstrates a gradual increase in length. This biomechanical phenomenon is best described as:

What enzyme is primarily responsible for generating the acidic environment necessary for osteoclastic bone resorption at the ruffled border?

In which zone of articular cartilage are the collagen fibers oriented parallel to the joint surface to resist shear forces?

A 12-year-old boy presents with multiple bony prominences near his knee and shoulder joints. Genetic testing confirms a mutation in the EXT1 gene. This gene is primarily responsible for the synthesis of which of the following?

Which of the following modifications to a cortical screw design will most effectively increase its pullout strength from bone?

During the remodeling phase of tendon healing, the cellularity decreases and collagen fibers align along the direction of stress. Which cell type is most responsible for this ongoing matrix synthesis and remodeling?

Which of the following combinations of orthopedic implant metals has the highest risk of galvanic corrosion when placed in direct contact within the body?

The primary mechanism of lubrication in healthy articular cartilage under high-load conditions (e.g., standing or walking) is best described as: