Biology, Genetics & Bone Healing MCQs

A 25-year-old man presents with progressive knee pain. Radiographs reveal an eccentric, entirely lytic epiphyseal lesion in the proximal tibia with no sclerotic border. A biopsy demonstrates sheets of mononuclear cells interspersed with numerous osteoclast-like giant cells. Due to the proximity to the joint, a specific monoclonal antibody is considered for systemic treatment prior to curettage to downstage the tumor. This medication exerts its effect by binding directly to which of the following?

An 18-year-old man sustains a transverse midshaft femur fracture that is surgically stabilized with an intramedullary nail, leaving a minor gap at the fracture site. This mechanical environment promotes secondary (indirect) bone healing. Following the initial inflammatory phase and soft callus formation, endochondral ossification begins. During the hard callus phase, which of the following types of bone is initially deposited by osteoblasts?

A 45-year-old man undergoes a posterolateral lumbar fusion. Recombinant human bone morphogenetic protein-2 (rhBMP-2) is utilized. Which of the following best describes the intracellular signaling mechanism immediately following BMP binding to its receptor?

A 65-year-old woman with severe osteoporosis requires spinal instrumentation. To maximize pedicle screw pull-out strength in osteoporotic bone, which of the following alterations in screw design is most effective?

A 70-year-old man presents with aseptic loosening of his cementless total hip arthroplasty 15 years after the index procedure. Radiographs show extensive periprosthetic osteolysis. The primary biological mechanism involves particulate wear debris stimulating macrophages to release cytokines. Which of the following is the final common pathway leading to bone resorption in this condition?

A 35-year-old patient with a displaced transverse midshaft tibial fracture is treated with an intramedullary nail. The construct allows for a moderate amount of interfragmentary motion. According to Perren's strain theory, what type of tissue will primarily form in the fracture gap if the interfragmentary strain is between 2% and 10%?

A 45-year-old man undergoes a posterolateral lumbar fusion using a structural cortical allograft. What is the primary mechanism by which this structural allograft will incorporate over the next 12 months?

A 35-year-old woman presents with severe knee pain. Radiographs reveal an eccentric, lytic, epiphyseal-metaphyseal lesion in the distal femur extending to the subchondral bone. Biopsy shows mononuclear cells and multinucleated giant cells. Which of the following describes the mechanism of action of the most appropriate targeted medical therapy for a recurrent or unresectable form of this disease?

A 32-year-old woman presents with progressive knee pain and swelling. Radiographs display an eccentric, expansile, purely lytic lesion in the distal femoral epiphysis extending to the subchondral bone plate without a sclerotic margin. Histologic examination demonstrates a proliferation of neoplastic mononuclear stromal cells mixed with numerous multinucleated giant cells. For surgically unsalvageable or recurrent disease, targeted systemic therapy would appropriately focus on inhibiting which of the following molecular targets?

Denosumab is a targeted biological therapy frequently used in the treatment of osteoporosis and giant cell tumor of bone. Which of the following best describes its specific mechanism of action?

Bone morphogenetic proteins (BMPs) are potent osteoinductive growth factors utilized in spine fusion and fracture nonunions. Upon binding to their specific cell-surface serine/threonine kinase receptors, which primary intracellular signaling pathway is activated to promote osteoblast differentiation?

A 65-year-old woman is prescribed romosozumab for severe osteoporosis. This medication primarily increases bone mineral density through which of the following cellular mechanisms?

Bone morphogenetic proteins (BMPs) belong to the TGF-beta superfamily and play a critical role in osteoinduction. Which of the following intracellular signaling molecules is directly phosphorylated and activated by the BMP receptor upon ligand binding?

A diaphyseal femur fracture is stabilized with a locked intramedullary nail. Which of the following modes of bone healing is expected to predominate?

Osteoclasts resorb bone by creating an acidic environment in the sealed zone. Which of the following enzymes is primarily responsible for generating the hydrogen ions required for this process?

Nitrogen-containing bisphosphonates (e.g., alendronate) are commonly prescribed for osteoporosis. They primarily inhibit osteoclast function and induce apoptosis by interfering with which of the following intracellular pathways?

Primary (direct) bone healing relies on absolute stability and occurs without radiographically visible callus formation. Which of the following histologic features is characteristic of primary bone healing?

Which of the following genetic mutations is most likely to cause infantile malignant osteopetrosis due to the inability of osteoclasts to acidify the Howship lacuna?

Sclerostin is a key regulatory glycoprotein produced primarily by mature osteocytes. It reduces bone formation by antagonizing which of the following intracellular signaling pathways?

A 65-year-old postmenopausal woman with severe osteoporosis is treated with denosumab to reduce her fracture risk. Which of the following describes the precise mechanism of action of this medication in modulating bone metabolism?