1. General Principles & Basic Science MCQs

According to Perren's strain theory, what is the maximum amount of interfragmentary strain that can be tolerated to allow for primary bone healing (osteonal reconstruction) without the formation of a visible fracture callus?

Titanium alloys (e.g., Ti-6Al-4V) are frequently used in orthopedic implants due to their excellent biocompatibility and fatigue strength. Which of the following characteristics best explains the superior in vivo corrosion resistance of titanium compared to stainless steel?

Staphylococcus aureus is a leading cause of periprosthetic joint infection. The persistence of these infections is largely attributed to the formation of a biofilm. Which of the following is the primary constituent of the extracellular polymeric substance (EPS) matrix in a mature S. aureus biofilm?

A 68-year-old female presents with diffuse bone pain and proximal muscle weakness. Laboratory evaluation reveals hypocalcemia, hypophosphatemia, and elevated alkaline phosphatase. A transiliac bone biopsy with double tetracycline labeling would most likely demonstrate which of the following?

During normal human walking, the articular cartilage of the knee is subjected to varying loads and sliding speeds. Which lubrication mechanism is most predominant during the swing phase of the gait cycle, when the joint experiences high sliding speeds and relatively low loads?

Bupivacaine is commonly used for regional anesthesia and postoperative pain control in orthopedics. Its primary mechanism of action involves the blockade of which of the following neuronal ion channels?

Bone morphogenetic proteins (BMPs) are signaling molecules belonging to the TGF-beta superfamily that promote bone formation. Which of the following BMPs is an FDA-approved osteoinductive agent commonly used in acute open tibial shaft fractures?

During a heavy eccentric contraction, such as the lowering phase of a bicep curl, the muscle generates active tension while lengthening. Which of the following describes the fundamental structural and functional unit of the muscle fiber that lengthens during this process?

The anterior cruciate ligament (ACL) of the knee is primarily composed of water and a highly organized extracellular matrix of collagen. Which of the following cell types is predominantly responsible for the synthesis, maintenance, and repair of this extracellular matrix?

Cefazolin is a first-generation cephalosporin routinely utilized for surgical site infection prophylaxis in clean orthopedic procedures. It exerts its bactericidal effect against susceptible organisms through which of the following mechanisms?

A 45-year-old male sustains a nonunion of the tibial shaft. A treatment plan involving demineralized bone matrix (DBM) is chosen. Which of the following best describes the osteogenic potential and primary mechanism of bone formation associated with DBM?

A 25-year-old structural engineer asks about the biomechanical properties of a new titanium alloy compared to stainless steel for a fracture plate. When evaluating the stress-strain curve of the material, which of the following best represents the total energy absorbed by the material before structural failure?

Biochemical analysis of articular cartilage is performed comparing samples from a normal 80-year-old patient and a 65-year-old patient with severe osteoarthritis (OA). Which of the following biochemical changes is characteristic of aging cartilage rather than osteoarthritic cartilage?

A 30-year-old female presents with facial nerve palsy and hearing loss. Radiographs demonstrate marked cortical thickening and sclerosis of the skull and long bones. Genetic testing reveals a mutation in the SOST gene. The protein encoded by this gene normally regulates bone mass by antagonizing which of the following intracellular signaling pathways?

A 65-year-old male undergoes revision total hip arthroplasty for a painful, sterile joint effusion 7 years after the index procedure with a modular titanium-alloy stem and a cobalt-chromium head. Intraoperatively, significant black debris is noted precisely at the head-neck junction. Which mechanism is primarily responsible for the generation of this debris?

A physical therapist designs a rehabilitation protocol for a patient recovering from a hamstring strain. The protocol emphasizes muscle contractions where the muscle lengthens while developing tension. This type of contraction, which is known to generate the highest forces and is most associated with delayed-onset muscle soreness (DOMS), is known as:

An orthopedic surgeon is selecting an intramedullary nail for an unstable femur fracture. The surgeon considers a solid titanium nail versus a hollow titanium nail of the exact same outer diameter. The solid nail has a higher bending stiffness. According to the principles of biomechanics, the bending stiffness of a solid cylindrical implant is proportional to its radius raised to what power?