Biology, Genetics & Bone Healing MCQs

Histological analysis of an actively remodeling bone reveals multinucleated cells situated in Howship's lacunae. The specialized "ruffled border" of these cells, which facilitates bone resorption, is primarily formed by which structural elements?

A 19-year-old female collegiate runner presents with an anterior tibial stress fracture and reports irregular menstrual cycles for the past year. Dual-energy x-ray absorptiometry reveals low bone mineral density. What is the primary underlying physiological mechanism for her condition (Relative Energy Deficiency in Sport)?

A 19-year-old female cross-country runner presents with a femoral neck stress fracture. She has a BMI of 17.5 and reports amenorrhea for the last 8 months. What is the third component of the clinical triad most commonly associated with her condition?

A 13-year-old boy with a history of multiple fractures and blue sclerae is being treated for osteogenesis imperfecta with intravenous bisphosphonates. What is the primary mechanism of action of this medication?

A 4-year-old girl with blue sclerae and a history of multiple low-energy fractures is treated with intravenous pamidronate. What is the primary mechanism of action of this medication in treating her underlying genetic condition?

A 2-year-old boy is evaluated for genu varum. Standing radiographs demonstrate a metaphyseal-diaphyseal angle (Drennan angle) of 18 degrees on the right tibia. What is the most likely diagnosis?

A 3-year-old obese girl presents with unilateral genu varum. Radiographs reveal a metaphyseal-diaphyseal (Drennan) angle of 20 degrees. What is the diagnosis and best initial treatment?

Aseptic loosening due to wear-particle induced osteolysis remains a long-term complication of total hip arthroplasty. At the cellular level, which of the following is the primary direct mediator of osteoclast activation and subsequent bone resorption in this cascade?

In particle-induced periprosthetic osteolysis surrounding a total hip arthroplasty, macrophages ingest wear debris and release inflammatory cytokines. Which downstream biological mediator is primarily responsible for the direct activation of osteoclasts in this process?

A 60-year-old female taking alendronate for 10 years presents with 3 months of lateral thigh pain. Radiographs reveal diffuse cortical thickening of the lateral subtrochanteric femur with a transverse radiolucent 'beak' on the lateral cortex extending halfway through the bone. What is the most appropriate management?

A 72-year-old female presents with thigh pain and a subsequent low-energy transverse femur fracture showing cortical thickening and a lateral cortical beak. She has been taking alendronate for 10 years. What is the primary underlying pathophysiology responsible for this specific fracture pattern?

A 72-year-old woman on long-term alendronate presents with lateral thigh pain. Radiographs reveal focal lateral cortical thickening and a transverse radiolucent line in the subtrochanteric femur. What is the most appropriate management?

A 65-year-old woman on alendronate for 12 years presents with an incomplete, transverse fracture through the lateral cortex of the subtrochanteric femur. She reports progressive thigh pain over the last 3 months. What is the most appropriate management for this symptomatic impending atypical femur fracture?

A 78-year-old woman with a history of severe osteoporosis presents with acute-onset, severe mid-back pain after coughing. MRI confirms an acute T11 compression fracture without posterior wall involvement or neurologic deficit. She has failed 6 weeks of aggressive conservative management including bracing and analgesics. What is the most appropriate next step?

Which of the following best describes the intracellular signaling pathway activated by Bone Morphogenetic Protein (BMP) to promote osteoblast differentiation?

A 65-year-old woman with metastatic breast cancer is treated with an agent to prevent skeletal-related events. The agent is a monoclonal antibody that targets RANKL. Which of the following is the primary cellular effect of this medication?

An infant presents with multiple fractures, cranial nerve palsies, and diffuse osteosclerosis on radiographs. A diagnosis of malignant infantile osteopetrosis is made. The most common genetic mutation associated with this condition affects which of the following osteoclast functions?

A 6-year-old boy presents with refusal to walk, gingival bleeding, and petechiae. Radiographs of the lower extremities show osteopenia, a dense zone of provisional calcification, and an adjacent radiolucent band. The underlying nutritional deficiency impairs which of the following steps in collagen synthesis?

Continuous administration of Parathyroid Hormone (PTH), as seen in primary hyperparathyroidism, leads to net bone resorption. Which of the following best describes the direct action of PTH on bone cells to induce this effect?