1. General Principles & Basic Science MCQs

Demineralized bone matrix (DBM) is used during a spinal fusion. Which of the following components is primarily responsible for the osteoinductive properties of this graft material?

A patient requires revision of a femoral shaft fracture nonunion. The original stainless steel plate is left in place, and a titanium screw is used for supplementary fixation. Which of the following processes is most likely to occur at the interface of these two metals?

During the inflammatory phase of fracture healing, which of the following cell types is primarily responsible for the initial clearing of necrotic tissue and secretion of cytokines to recruit mesenchymal stem cells?

Calcium phosphate cements are often used to fill metaphyseal bone defects. Which of the following statements best describes their primary biomechanical advantage and clinical limitation?

A novel therapeutic agent for osteoporosis works by binding to sclerostin. What is the downstream effect of this medication on bone metabolism?

A patient presents with hypophosphatemic rickets. Laboratory evaluation reveals elevated levels of Fibroblast Growth Factor 23 (FGF23). What is the primary physiological effect of FGF23 on the kidneys?

Polymethylmethacrylate (PMMA) is utilized for implant fixation in a cemented total knee arthroplasty. Which of the following statements regarding the properties of PMMA is accurate?

A 25-year-old patient with increased bone density and cranial nerve impingement is diagnosed with sclerosteosis. This condition is caused by a mutation that affects a protein normally secreted by osteocytes. By which of the following mechanisms does this normal protein function?

Which of the following best describes the mechanical behavior of cortical bone, whereby its strength and stiffness increase as the rate of loading increases?

Cortical bone demonstrates different mechanical properties depending on the direction of the applied load. It is stronger in longitudinal compression than in transverse loading. Which biomechanical term best defines this property?

A newborn is evaluated for absent clavicles and delayed closure of the cranial sutures. Genetic testing is expected to reveal a mutation in a key transcription factor essential for osteoblast differentiation. Which of the following is the most likely mutated gene?

A surgeon plans to perform a revision fixation using a stainless steel plate adjacent to an existing titanium screw. Which of the following complications is most likely to occur due to the combination of these two different metals in a physiologic environment?

Which of the following non-collagenous bone matrix proteins is vitamin K-dependent and plays a major role in regulating bone mineralization by binding to calcium and hydroxyapatite?

Continuous, high-dose administration of parathyroid hormone (PTH) results in net bone resorption. Through which cellular mechanism does PTH primarily stimulate osteoclast activity?

In a stress-strain curve for a metallic implant, the point at which the material ceases to deform elastically and begins to deform permanently is known as which of the following?

During the incorporation of a cortical structural allograft, the process by which osteoclasts resorb the dead bone and osteoblasts subsequently lay down new vital bone is termed:

To dissolve the inorganic hydroxyapatite matrix during bone resorption, osteoclasts create an acidic environment in the sealed zone (Howship's lacuna). Which of the following enzymes is primarily responsible for generating the hydrogen ions needed for this process?

Absolute stability achieved through rigid internal fixation with a compression plate leads to which type of fracture healing?

A 65-year-old woman presents with generalized bone pain and proximal muscle weakness. Laboratory studies show hypocalcemia, hypophosphatemia, elevated alkaline phosphatase, and low 25-hydroxyvitamin D. Bone biopsy would most likely show:

Bone morphogenetic proteins (BMPs) play a crucial role in osteoinduction during bone healing. BMPs exert their cellular effects primarily by binding to transmembrane receptors and activating which intracellular signaling molecules?