Menu

Biology, Genetics & Bone Healing MCQs

Practice Set 185 of 212

This practice set contains high-yield board review questions covering key concepts in Biology, Genetics & Bone Healing. Each clinical scenario is designed to test your diagnostic and management skills relevant to this subspecialty.

Question 3681

Topic: Biology, Genetics & Bone Healing

Which metabolic bone disorder is characterized by elevated serum alkaline phosphatase, normal serum calcium and phosphate, and disorganized bone remodeling leading to bone pain, deformity, and increased fracture risk?

. Osteoporosis
. Osteomalacia
. Hyperparathyroidism
. Paget's disease of bone
. Rickets

Correct Answer & Explanation

. Paget's disease of bone

Explanation

Paget's disease of bone (osteitis deformans) is characterized by a focal disorder of bone remodeling, with abnormally high osteoclast activity followed by compensatory osteoblast activity, leading to disorganized, enlarged, and weak bone. This results in elevated serum alkaline phosphatase (a marker of osteoblast activity) while serum calcium and phosphate levels typically remain normal. Clinical features include bone pain, deformity (e.g., bowing of long bones), pathological fractures, and neurologic complications due to nerve compression. Osteoporosis involves decreased bone mass but normal bone histology. Osteomalacia and rickets (in children) are due to defective mineralization, often with low phosphate and/or calcium. Hyperparathyroidism involves elevated PTH and altered calcium/phosphate levels.

Question 3682

Topic: Biology, Genetics & Bone Healing

What type of bone graft offers osteoinductive, osteoconductive, and osteogenic properties?

. Allograft
. Demineralized bone matrix (DBM)
. Autograft (cancellous)
. Ceramic bone substitutes
. Bone morphogenetic proteins (BMPs)

Correct Answer & Explanation

. Autograft (cancellous)

Explanation

Autograft (cancellous) is considered the 'gold standard' for bone grafting because it possesses all three essential properties: osteoconduction (provides a scaffold for new bone growth), osteoinduction (contains growth factors that stimulate host mesenchymal stem cells to differentiate into osteoblasts), and osteogenesis (contains living osteocytes and osteoblasts from the donor site that can immediately form new bone). Allografts are primarily osteoconductive and osteoinductive but lack viable osteogenic cells. DBM is primarily osteoinductive and osteoconductive. Ceramic bone substitutes are mainly osteoconductive. BMPs are purely osteoinductive.

Question 3683

Topic: Biology, Genetics & Bone Healing

What is the most common cause of osteonecrosis of the jaw (ONJ) in orthopedic patients?

. Corticosteroid use
. Radiation therapy to the head and neck
. Bisphosphonate therapy
. Infection
. Trauma to the jaw

Correct Answer & Explanation

. Bisphosphonate therapy

Explanation

In orthopedic patients, bisphosphonate therapy is the most common cause of osteonecrosis of the jaw (ONJ), often referred to as bisphosphonate-related osteonecrosis of the jaw (BRONJ). Bisphosphonates, especially IV forms used in metastatic bone disease or osteoporosis, inhibit osteoclast activity, which can impair bone remodeling and healing in the jaw, particularly after dental procedures or trauma. While radiation and infection can cause ONJ, bisphosphonate use is a specific and significant risk factor in the orthopedic population. Corticosteroids and trauma are less commonly implicated as primary causes compared to bisphosphonates.

Question 3684

Topic: Biology, Genetics & Bone Healing

What is the primary mechanism of action of parathyroid hormone (PTH) in bone metabolism?

. Directly stimulates osteoblasts to form new bone.
. Inhibits osteoclast activity, leading to decreased bone resorption.
. Increases serum calcium by promoting bone resorption and renal reabsorption.
. Decreases serum calcium by promoting calcium excretion.
. Promotes calcium absorption from the intestines by inhibiting vitamin D.

Correct Answer & Explanation

. Increases serum calcium by promoting bone resorption and renal reabsorption.

Explanation

Parathyroid hormone (PTH) plays a crucial role in calcium homeostasis. Its primary mechanism of action related to bone metabolism is to increase serum calcium levels. It achieves this by stimulating osteoclasts (indirectly, via osteoblasts) to resorb bone, releasing calcium into the bloodstream. It also increases calcium reabsorption in the renal tubules and stimulates the synthesis of calcitriol (active vitamin D), which in turn enhances intestinal calcium absorption. PTH does not directly stimulate osteoblasts for net new bone formation in a sustained manner, nor does it inhibit osteoclasts or decrease serum calcium.

Question 3685

Topic: Biology, Genetics & Bone Healing

A 23-year-old man presents with right posterolateral knee pain, worse at night and relieved by NSAIDs. Imaging and histology are shown. The histologic specimen demonstrates a cellular, vascular stroma with plump osteoblasts producing immature woven bone. What is the currently preferred minimally invasive treatment for this lesion?

. Intralesional injection of corticosteroids
. Percutaneous radiofrequency ablation
. En bloc resection with wide margins
. Radiation therapy
. Systemic chemotherapy

Correct Answer & Explanation

. Percutaneous radiofrequency ablation

Explanation

Correct Answer: BThe clinical presentation, imaging (cortically based lytic lesion with surrounding sclerosis/edema), and histology (vascular stroma with osteoblasts and woven bone) are classic for an osteoid osteoma. Percutaneous radiofrequency ablation (RFA), typically under CT guidance, has become the preferred treatment method, offering high success rates with minimal morbidity compared to open surgical excision.

Question 3686

Topic: Biology, Genetics & Bone Healing

A 23-year-old man presents with right posterolateral knee pain that is worse at night and dramatically relieved by NSAIDs. Imaging reveals a well-circumscribed, cortically based lytic lesion in the proximal fibula with surrounding edema. Histology demonstrates a cellular stroma with plump osteoblasts producing immature woven bone. What is the preferred definitive treatment for this condition?

. Wide surgical resection
. Percutaneous radiofrequency ablation
. Intralesional curettage and bone grafting
. Neoadjuvant chemotherapy followed by resection
. Radiation therapy

Correct Answer & Explanation

. Percutaneous radiofrequency ablation

Explanation

Correct Answer: Percutaneous radiofrequency ablationThe clinical presentation (night pain relieved by NSAIDs), radiographic appearance (cortically based lytic lesion with surrounding sclerosis/edema), and histology (plump osteoblasts producing woven bone in a vascular stroma) are classic for an osteoid osteoma. Percutaneous radiofrequency ablation (RFA), typically performed under CT guidance, has become the preferred, minimally invasive treatment of choice for most osteoid osteomas, offering high success rates and low morbidity compared to open surgical resection or curettage.

Question 3687

Topic: Biology, Genetics & Bone Healing

A 23-year-old man presents with right posterolateral knee pain that is worse at night and relieved by NSAIDs. Imaging and histology are provided. The histologic specimen is most likely to demonstrate which of the following?

. Sheets of small round blue cells
. A cellular stroma with plump osteoblasts producing immature woven bone
. Atypical chondrocytes in a lobular pattern
. Multinucleated giant cells in a background of mononuclear stromal cells
. Dead bone with abundant acute inflammatory cells

Correct Answer & Explanation

. A cellular stroma with plump osteoblasts producing immature woven bone

Explanation

Correct Answer: A cellular stroma with plump osteoblasts producing immature woven boneThe clinical presentation, imaging (cortically based lytic lesion with surrounding edema), and histology are diagnostic of an osteoid osteoma. Histologically, it consists of a highly vascularized nidus of interlacing trabeculae of osteoid and woven bone lined by plump, benign osteoblasts.

Question 3688

Topic: Biology, Genetics & Bone Healing

A 23-year-old man complains of right posterolateral knee pain that is worse at night and relieved by NSAIDs. Imaging and histology are shown. The histology demonstrates a cellular, vascular stroma with plump osteoblasts producing immature woven bone. What is the preferred modern treatment modality for this lesion?

. En bloc resection with wide margins
. Percutaneous radiofrequency ablation
. Intralesional curettage and bone grafting
. Neoadjuvant chemotherapy followed by resection
. Radiation therapy

Correct Answer & Explanation

. Percutaneous radiofrequency ablation

Explanation

Correct Answer: BThe clinical presentation (night pain relieved by NSAIDs), radiographic appearance (cortically based lytic lesion with surrounding sclerosis), and histology (vascular stroma with osteoblasts and woven bone) are diagnostic of an osteoid osteoma. The preferred modern treatment for most osteoid osteomas is CT-guided percutaneous radiofrequency ablation, which is minimally invasive and highly effective. En bloc resection is rarely required today.

Question 3689

Topic: Biology, Genetics & Bone Healing

Bone morphogenetic proteins (BMP-2 and BMP-7) are utilized clinically to promote bone healing and fusion. Upon binding to their respective transmembrane receptors, which intracellular signaling molecules are directly phosphorylated to translocate to the nucleus and induce osteogenic gene expression?

. Wnt and beta-catenin
. Smad 1, 5, and 8
. ERK and MAPK
. RANK and TRAF6
. JAK and STAT

Correct Answer & Explanation

. Smad 1, 5, and 8

Explanation

BMPs exert their osteoinductive effects primarily through the canonical Smad pathway. Binding to serine/threonine kinase receptors leads to the phosphorylation of Smad 1, 5, and 8, which then complex with Smad 4 to regulate target gene transcription.

Question 3690

Topic: Biology, Genetics & Bone Healing

A 40-year-old male sustains a diaphyseal radius and ulna fracture, treated with open reduction and internal fixation using dynamic compression plates to achieve absolute stability. Which primary mode of bone healing is expected to occur in this mechanically rigid environment?

. Endochondral ossification
. Intramembranous ossification
. Primary bone healing via Haversian cutting cones
. Secondary bone healing via cartilaginous callus formation
. Fibrocartilaginous distraction osteogenesis

Correct Answer & Explanation

. Primary bone healing via Haversian cutting cones

Explanation

Rigid internal fixation with absolute stability eliminates interfragmentary motion, facilitating primary (direct) bone healing. This process occurs via Haversian remodeling driven by osteoclastic cutting cones followed by osteoblastic bone deposition, completely bypassing callus formation.

Question 3691

Topic: Biology, Genetics & Bone Healing

In the context of distraction osteogenesis via the Ilizarov method, what is the optimal latency period prior to initiating distraction after the corticotomy?

. 0 to 1 day
. 2 to 3 days
. 5 to 7 days
. 10 to 14 days
. 21 days

Correct Answer & Explanation

. 5 to 7 days

Explanation

A latency period of 5 to 7 days is optimal for establishing early vascularization and primitive callus formation before distraction begins. Shorter latency risks poor regenerate formation, while longer latency risks premature consolidation.

Question 3692

Topic: Biology, Genetics & Bone Healing

The Taylor Spatial Frame utilizes a specialized software program to calculate strut adjustments based on a 6-axis deformity analysis. Which of the following is NOT a required radiographic or clinical parameter for the software to generate a prescription?

. Anteroposterior offset
. Axial translation
. Bone density score (DEXA)
. Lateral offset
. Rotational offset

Correct Answer & Explanation

. Bone density score (DEXA)

Explanation

The software requires precise mechanical parameters including AP, lateral, and axial offsets, as well as rotational and angular data relative to a reference ring. Bone density scores (DEXA) are not inputted into the spatial frame software for kinematic calculations.

Question 3693

Topic: Biology, Genetics & Bone Healing

A 32-year-old female presents with a purely lytic, eccentric lesion in the distal femur extending to the subchondral bone. Biopsy confirms giant cell tumor of bone. Neoadjuvant therapy with denosumab is considered. What is the mechanism of action of this drug?

. Monoclonal antibody against RANK ligand (RANKL)
. Inhibits osteoclast ruffled border proton pumps
. Binds to VEGF to inhibit angiogenesis
. Tyrosine kinase inhibitor of c-KIT
. Direct cytotoxic effect on multinucleated giant cells

Correct Answer & Explanation

. Monoclonal antibody against RANK ligand (RANKL)

Explanation

Denosumab is a human monoclonal antibody that binds to RANKL, preventing it from activating RANK on the surface of osteoclasts and their precursors. In giant cell tumors, it halts the tumor-induced osteolysis mediated by the reactive giant cells.

Question 3694

Topic: Biology, Genetics & Bone Healing

A 32-year-old male presents with knee pain. Radiographs reveal an eccentric, lytic epiphyseal lesion in the distal femur. Biopsy reveals multinucleated giant cells and mononuclear stromal cells.

Which cell population harbors the neoplastic mutation, and what marker do they overexpress?

. Multinucleated giant cells expressing RANKL
. Mononuclear stromal cells expressing RANK
. Mononuclear stromal cells expressing RANKL
. Multinucleated giant cells expressing RANK
. Macrophages expressing CD68

Correct Answer & Explanation

. Mononuclear stromal cells expressing RANKL

Explanation

In Giant Cell Tumor of bone, the mononuclear spindle-like stromal cells are the true neoplastic cells. They express RANKL, which recruits and stimulates normal osteoclast precursors to form the reactive multinucleated giant cells.

Question 3695

Topic: Biology, Genetics & Bone Healing

Which of the following skeletal dysplasias is characterized by a mutation in the RUNX2 (CBFA1) gene, delayed closure of cranial sutures, and supernumerary teeth?

. Osteogenesis Imperfecta
. Cleidocranial dysplasia
. Diastrophic dysplasia
. Achondroplasia
. Multiple epiphyseal dysplasia

Correct Answer & Explanation

. Cleidocranial dysplasia

Explanation

Cleidocranial dysplasia is an autosomal dominant condition caused by a RUNX2 mutation, leading to defective intramembranous ossification. Hallmarks include absent or hypoplastic clavicles, delayed cranial suture closure, and supernumerary teeth.

Question 3696

Topic: Biology, Genetics & Bone Healing

A 32-year-old woman presents with knee pain. Radiographs show an eccentric, lytic epiphyseal-metaphyseal lesion of the distal femur. Biopsy confirms a Giant Cell Tumor. If she is treated with denosumab preoperatively, which histological change is most expected?

. Increased mitotic figures in mononuclear cells
. Depletion of multinucleated osteoclast-like giant cells
. Extensive cartilage matrix production
. Transformation into a high-grade sarcoma
. Appearance of atypical spindle cells

Correct Answer & Explanation

. Depletion of multinucleated osteoclast-like giant cells

Explanation

Denosumab is a monoclonal antibody against RANKL. It prevents the RANK-RANKL interaction, leading to the rapid depletion of the reactive multinucleated giant cells and promotion of woven bone formation, while the underlying neoplastic mononuclear stromal cells persist.

Question 3697

Topic: Biology, Genetics & Bone Healing

In a Giant Cell Tumor of bone, which specific cell population harbors the pathognomonic H3F3A mutation and is considered the true neoplastic component?

. The multinucleated osteoclast-like giant cells
. The mononuclear spindle-shaped stromal cells
. The reactive histiocytes
. The recruited osteoblasts
. The perivascular pericytes

Correct Answer & Explanation

. The mononuclear spindle-shaped stromal cells

Explanation

The mononuclear spindle-shaped stromal cells are the true neoplastic cells in a Giant Cell Tumor of bone and typically harbor a mutation in the H3F3A gene. These cells secrete RANKL, which subsequently recruits and activates the non-neoplastic, reactive multinucleated giant cells.

Question 3698

Topic: Biology, Genetics & Bone Healing

In the management of a massive, unresectable recurrent giant cell tumor of the sacrum, which of the following targeted medical therapies is the most appropriate primary treatment?

. Imatinib
. Denosumab
. Zoledronic acid
. Rituximab
. Methotrexate

Correct Answer & Explanation

. Denosumab

Explanation

Denosumab is a monoclonal antibody against RANKL, which is overexpressed by the neoplastic mononuclear stromal cells in GCT. It effectively inhibits the recruitment and function of reactive osteoclast-like giant cells, making it the treatment of choice for unresectable cases.

Question 3699

Topic: Biology, Genetics & Bone Healing

Which of the following structural defects is primarily responsible for the clinical manifestations seen in patients with Osteogenesis Imperfecta?

. Defect in type II collagen synthesis
. Defect in type I collagen folding or synthesis
. Impaired osteoclast carbonic anhydrase II function
. Mutation in the RUNX2 gene
. Mutation in the Fibroblast Growth Factor Receptor 3 gene

Correct Answer & Explanation

. Defect in type I collagen folding or synthesis

Explanation

Osteogenesis imperfecta is most commonly caused by mutations in the COL1A1 or COL1A2 genes. This leads to quantitative or qualitative defects in Type I collagen, which is the major structural protein in bone, sclera, and dentin.

Question 3700

Topic: Biology, Genetics & Bone Healing

A 28-year-old female presents with knee pain. Radiographs show an eccentric, lytic epiphyseal lesion extending to the subchondral bone. Biopsy confirms a tumor characterized by mononuclear stromal cells and multinucleated giant cells. Which of the following best describes the mechanism of the targeted medical therapy for this condition?

. Inhibition of RANKL
. Inhibition of osteoprotegerin
. Tyrosine kinase inhibition
. Inhibition of VEGF
. Bisphosphonate-mediated apoptosis

Correct Answer & Explanation

. Inhibition of RANKL

Explanation

Giant cell tumor of bone is driven by RANKL-expressing neoplastic stromal cells that recruit osteoclast-like giant cells. Denosumab, a monoclonal antibody that inhibits RANKL, is the targeted medical therapy used for advanced or unresectable cases.

Test Yourself

Switch to an interactive, timed exam simulation to truly master this topic.

On this Page