1. General Principles & Basic Science MCQs

Boundary lubrication is crucial for minimizing friction in articular cartilage, particularly under conditions of low loads and low speeds. Which of the following molecules is primarily responsible for boundary lubrication at the articular surface?

In Paget disease of bone, the primary cellular abnormality is excessive osteoclastic resorption followed by disorganized osteoblastic bone formation. This hyperactive osteoclast state is most frequently associated with a mutation in which of the following?

A skeletal traction pin is placed in the proximal tibia, and a constant 15-pound weight is applied over several days. The progressive, time-dependent increase in deformation of the bone and soft tissues under this constant load is defined as:

Demineralized bone matrix (DBM) is frequently used in orthopedic surgery to augment fracture healing. Which of the following best describes the primary biological mechanism by which DBM promotes bone formation?

Skeletal muscle fibers are broadly classified into slow-twitch (Type I) and fast-twitch (Type II) fibers based on their metabolic and contractile properties. Which of the following profiles best characterizes Type I muscle fibers?

During the pathogenesis of periprosthetic joint infection, bacteria form a biofilm on the implant surface. The irreversible adherence of bacteria and subsequent biofilm maturation is primarily mediated by the production of:

Following peripheral nerve transection, Wallerian degeneration occurs distal to the injury site. Which cell type is predominantly responsible for phagocytosing and clearing myelin debris during the first 1 to 2 weeks of this process?

A 4-year-old boy presents with severe bilateral genu varum. Laboratory evaluation reveals low serum phosphate, normal serum calcium, and elevated alkaline phosphatase. Parathyroid hormone (PTH) levels are normal. Which of the following is the most likely diagnosis?

During the single-leg stance phase of the normal gait cycle, the hip abductor muscles must generate significant force to maintain a level pelvis. This abductor force is approximately equivalent to:

In articular cartilage, proteoglycans are vital for providing compressive stiffness. Aggrecan monomers attach to a central backbone to form massive proteoglycan aggregates. Which molecule forms this central backbone?

According to Perren's strain theory, the mechanical environment dictates the type of bone healing. Absolute stability, requiring interfragmentary strain to be less than 2%, exclusively permits which type of healing?

Titanium alloys (e.g., Ti-6Al-4V) are frequently used in orthopedics due to their excellent biocompatibility and favorable modulus of elasticity. Which of the following is a primary mechanical disadvantage of titanium alloys compared to stainless steel or cobalt-chromium?

During the post-operative rehabilitation of an acutely lacerated and repaired zone II flexor tendon, the tensile strength of the repair generally reaches its weakest point at what time frame?

A researcher is evaluating the mechanical properties of a newly designed intramedullary nail.

Which parameter on the stress-strain curve represents the material's stiffness (Young's modulus)?

Nitrogen-containing bisphosphonates, such as alendronate, are widely used to treat osteoporosis and prevent skeletal-related events in metastatic bone disease. What is their primary molecular mechanism of action?

An orthopedic resident applies a dynamic flexion splint to a patient with knee stiffness. Over time, the force required to maintain the knee at a constant angle of deformation gradually decreases. This viscoelastic phenomenon is known as:

A surgeon uses a 316L stainless steel screw to secure a Ti-6Al-4V titanium alloy plate. Several months later, rapid localized corrosion is noted at the screw-plate interface. Which type of corrosion is most directly caused by using these two dissimilar metals?