Biology, Genetics & Bone Healing MCQs

A 72-year-old male complains of deep, aching bone pain in his right leg and an increasing hat size over the past year. Radiographs demonstrate marked cortical thickening and bowing of the tibia. A bone biopsy of the affected tibia is most likely to reveal which histologic characteristic?

A spine surgeon elects to use demineralized bone matrix (DBM) to augment a posterolateral fusion. Based on its biologic processing, DBM provides which of the following combinations of bone-grafting properties?

Denosumab is highly effective in treating postmenopausal osteoporosis by aggressively reducing osteoclast-mediated bone resorption. What is the specific molecular target of this monoclonal antibody?

Patients with end-stage renal disease frequently develop renal osteodystrophy and secondary hyperparathyroidism. Which primary defect in vitamin D metabolism is the primary catalyst for this metabolic bone cascade?

A 10-year-old child presents with recurrent fractures, anemia, and cranial nerve palsies. Radiographs show a "bone-within-a-bone" appearance. A defect in which of the following cellular mechanisms is most likely responsible?

A surgeon utilizes a demineralized bone matrix (DBM) allograft for a spinal fusion. Which of the following biologic properties does DBM possess?

A 4-year-old child fed exclusively boiled cow's milk presents with irritability, bleeding gums, and subperiosteal hematomas. The primary defect in bone formation is related to the impaired function of which of the following enzymes?

A 70-year-old man undergoes total hip arthroplasty for secondary osteoarthritis. Radiographs demonstrate cortical thickening and coarse trabeculae in the proximal femur. Preoperative labs show an isolated elevation of alkaline phosphatase. Histologic evaluation of the femoral head would most likely show:

During secondary fracture healing, the biomechanical stability of the fracture determines the type of tissue that forms in the gap according to Perren's strain theory. If the strain at the fracture gap is between 2% and 10%, which tissue will primarily form?

A 68-year-old female with severe osteoporosis is treated with alendronate. Bisphosphonates inhibit osteoclast-mediated bone resorption by interfering with which of the following intracellular pathways?

A 70-year-old female is prescribed alendronate for osteoporosis. Which of the following best describes the cellular mechanism of action of this medication?

During secondary fracture healing, the transition from the soft callus to the hard callus phase is primarily characterized by which of the following biological processes?

A 4-year-old boy presents with refusal to walk, bleeding gums, and petechiae. Radiographs reveal a densely sclerotic metaphyseal line and a lucent zone immediately diaphyseal to it. A deficiency in a vitamin required for which of the following cellular processes is the likely cause?

A 72-year-old male presents with increasing hat size, hearing loss, and bowing of his tibiae. Radiographs show mixed lytic and sclerotic lesions. The primary cellular defect in this disease process is localized to which of the following?

Bone morphogenetic proteins (BMPs) are used clinically to augment bone healing. Which specific intracellular signaling molecules are directly phosphorylated by activated BMP receptors?

A neonate is diagnosed with malignant infantile osteopetrosis. The defective gene most commonly associated with this autosomal recessive condition encodes for which of the following?

What is the most abundant non-collagenous protein found in the extracellular matrix of mature bone?

Continuous endogenous secretion of parathyroid hormone (PTH) primarily stimulates osteoclastogenesis by binding directly to receptors on which of the following cells?

A 68-year-old female, who has been on alendronate for 12 years, presents with a 3-month history of insidious, dull aching pain in her left thigh, aggravated by weight-bearing. She denies any specific trauma. Physical examination reveals tenderness over the lateral aspect of her proximal femur. Radiographs show significant cortical thickening of the left subtrochanteric femur with a small, incomplete transverse lucency in the lateral cortex. What is the most appropriate next step in management?

Sclerostin is a key regulatory protein in bone metabolism targeted by novel osteoporosis medications. Which of the following best describes its mechanism of action in reducing bone formation?