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Biology, Genetics & Bone Healing MCQs

Practice Set 1 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 1

Topic: Biology, Genetics & Bone Healing
Ligament healing typically progresses through inflammatory, proliferative, and remodeling phases. During the remodeling phase of a healing medial collateral ligament (MCL), which critical structural transition occurs?
. Type I collagen is replaced by Type II collagen
. Type II collagen is replaced by Type I collagen
. Type III collagen is replaced by Type I collagen
. Type I collagen is replaced by Type III collagen
. Type III collagen is replaced by Type IV collagen

Correct Answer & Explanation

. Type III collagen is replaced by Type I collagen

Explanation

During the proliferative phase of ligament healing, mechanically weaker Type III collagen is laid down rapidly. In the remodeling phase, this Type III collagen is gradually replaced by stronger, highly organized Type I collagen.

Question 2

Topic: Biology, Genetics & Bone Healing

Which vitamin deficiency is associated with rickets in children and osteomalacia in adults?

. Vitamin A
. Vitamin K
. Vitamin C
. Vitamin D
. Vitamin B12

Correct Answer & Explanation

. Vitamin D

Explanation

Vitamin D deficiency leads to impaired mineralization of bone, causing rickets in children (growth plate abnormalities) and osteomalacia in adults (softening of mature bone).

Question 3

Topic: Biology, Genetics & Bone Healing

Which of the following factors increases the risk of developing osteoporosis?

. High calcium intake
. Regular weight-bearing exercise
. Post-menopausal status
. Obesity
. High testosterone levels

Correct Answer & Explanation

. Post-menopausal status

Explanation

Estrogen deficiency after menopause significantly accelerates bone loss, making post-menopausal women highly susceptible to osteoporosis.

Question 4

Topic: Biology, Genetics & Bone Healing

A 68-year-old woman on long-term alendronate therapy presents with sudden onset thigh pain after a minor trip. Radiographs show a transverse fracture in the subtrochanteric region with lateral cortical thickening. This fracture pattern is primarily attributed to which cellular mechanism?

. Hyperactive osteoblast function
. Suppression of osteoclastic bone resorption
. Overexpression of parathyroid hormone
. Deficiency in type I collagen synthesis
. Malignant transformation of osteocytes

Correct Answer & Explanation

. Suppression of osteoclastic bone resorption

Explanation

Bisphosphonates inhibit osteoclast function, severely suppressing bone turnover and impairing the physiological repair of microdamage. Over years of therapy, this leads to the accumulation of microfractures on the tension side (lateral cortex) of the femur, eventually resulting in an atypical complete fracture.

Question 5

Topic: Biology, Genetics & Bone Healing

A 45-year-old woman presents with an unresectable recurrence of a giant cell tumor of the sacrum. She is started on denosumab therapy. What is the specific mechanism of action of this medication?

. Inhibits vascular endothelial growth factor (VEGF)
. Binds to the RANK ligand (RANKL) preventing it from activating the RANK receptor
. Stimulates osteoblast production of unmineralized osteoid
. Directly induces apoptosis in mature osteoclasts
. Inhibits the mammalian target of rapamycin (mTOR) pathway

Correct Answer & Explanation

. Binds to the RANK ligand (RANKL) preventing it from activating the RANK receptor

Explanation

Denosumab is a fully human monoclonal antibody that binds directly to RANKL, preventing its interaction with the RANK receptor on osteoclast precursors. This prevents osteoclast formation, function, and survival, severely inhibiting the bone resorption characteristic of giant cell tumors.

Question 6

Topic: Biology, Genetics & Bone Healing

A 65-year-old woman is prescribed alendronate after a dual-energy X-ray absorptiometry (DEXA) scan reveals a T-score of -2.7 in her lumbar spine. Which of the following describes the primary molecular target of this bisphosphonate therapy?

. Inhibition of osteoblast apoptosis
. Stimulation of the Wnt/beta-catenin signaling pathway
. Inhibition of the farnesyl pyrophosphate synthase enzyme
. Binding to RANKL to prevent osteoclast activation
. Direct enhancement of intestinal calcium absorption

Correct Answer & Explanation

. Inhibition of the farnesyl pyrophosphate synthase enzyme

Explanation

Nitrogen-containing bisphosphonates (such as alendronate) inhibit the farnesyl pyrophosphate synthase enzyme within the mevalonate pathway. This disruption prevents the prenylation of small GTPases in osteoclasts, leading to impaired osteoclast function and enhanced apoptosis.

Question 7

Topic: Biology, Genetics & Bone Healing

A tibial shaft fracture is treated with absolute stability using a properly tensioned compression plate. Which of the following best describes the primary mode of bone healing expected in this scenario?

. Endochondral ossification with a large cartilaginous callus
. Intramembranous ossification via cutting cones without visible callus
. A combination of endochondral and intramembranous ossification
. Fibrous tissue formation followed by direct mineralization
. Appositional bone growth from the periosteum alone

Correct Answer & Explanation

. Intramembranous ossification via cutting cones without visible callus

Explanation

Absolute stability minimizes interfragmentary strain and allows for primary bone healing. This occurs via Haversian remodeling (cutting cones) directly across the fracture site, which skips the cartilaginous phase and forms no visible callus.

Question 8

Topic: Biology, Genetics & Bone Healing
During the proliferative phase of rotator cuff tendon healing after repair, which collagen type initially predominates before tissue remodeling occurs?
. Type I collagen
. Type II collagen
. Type III collagen
. Type IV collagen
. Type X collagen

Correct Answer & Explanation

. Type III collagen

Explanation

Tendon healing involves a proliferative phase characterized by the rapid deposition of Type III collagen. During the subsequent remodeling phase, this is gradually replaced by stronger, highly organized Type I collagen.

Question 9

Topic: Biology, Genetics & Bone Healing

The "Female Athlete Triad" is characterized by the interrelatedness of low energy availability, menstrual dysfunction, and low bone mineral density. The primary physiological driver of bone loss in this syndrome is:

. Hypercortisolism secondary to physical stress
. Hypoestrogenism secondary to disruption of the hypothalamic-pituitary-ovarian axis
. Hyperparathyroidism secondary to inadequate calcium intake
. Direct inhibition of osteoblasts by lactic acid accumulation
. Chronic vitamin D deficiency

Correct Answer & Explanation

. Hypoestrogenism secondary to disruption of the hypothalamic-pituitary-ovarian axis

Explanation

Low energy availability suppresses the hypothalamic release of GnRH, leading to decreased LH/FSH and subsequent hypoestrogenism. This lack of estrogen accelerates bone resorption and halts bone formation, leading to low bone mineral density.

Question 10

Topic: Biology, Genetics & Bone Healing

The most common adverse side effect of dietary supplementation with creatine in athletes is:

. Friable tendons
. Muscle cramping
. Myopathy
. Diabetes
. Osteoporosis

Correct Answer & Explanation

. Muscle cramping

Explanation

Creatine has recently become a popular dietary supplement among athletes. The long-term effects of creatine are not known. However, it appears to cause muscle cramping and heat intolerance.

Question 11

Topic: Biology, Genetics & Bone Healing

Following a diaphyseal fracture treated with rigid plate fixation (absolute stability), healing primarily occurs via which of the following mechanisms?

. Endochondral ossification
. Intramembranous ossification
. Haversian remodeling (cutting cones)
. Callus formation
. Fibrous tissue differentiation

Correct Answer & Explanation

. Haversian remodeling (cutting cones)

Explanation

Rigid plate fixation provides absolute stability, minimizing interfragmentary strain to near zero. This leads to primary bone healing via direct Haversian remodeling (cutting cones) without an intermediate cartilage phase or visible callus.

Question 12

Topic: Biology, Genetics & Bone Healing
Schmorl's nodes may be seen on radiographic studies in all of the following disorders except:
. Spina bifida
. Scheuermann's kyphosis
. Degenerative disk disease
. Trauma
. Osteoporosis

Correct Answer & Explanation

. Spina bifida

Explanation

Schmorl's nodes are seen in association with several disorders including Scheuermann's kyphosis, degenerative disk disease, trauma, and osteoporosis. Schmorl's nodes are not commonly seen in patients with spina bifida.

Question 13

Topic: Biology, Genetics & Bone Healing

The use of recombinant human bone morphogenetic protein-2 (rhBMP-2) in minimally invasive transforaminal lumbar interbody fusion (MIS TLIF) has been associated with which of the following specific postoperative complications?

. Anterior thigh pain
. Postoperative radiculitis
. Aseptic meningitis
. Retrograde ejaculation
. Spontaneous dural closure

Correct Answer & Explanation

. Postoperative radiculitis

Explanation

The use of rhBMP-2 in the posterior or transforaminal lumbar space has a well-documented risk of causing postoperative radiculitis, seroma formation, and ectopic bone growth leading to neuroforaminal stenosis.

Question 14

Topic: Biology, Genetics & Bone Healing

Aggressive osteoblastomas are distinguished from conventional osteoblastomas primarily by which histologic feature?

. Presence of plump, epithelioid osteoblasts
. Lack of osteoid matrix production
. Extensive areas of spontaneous necrosis
. Prominent hyaline cartilage matrix
. High mitotic rate with atypical mitoses

Correct Answer & Explanation

. Presence of plump, epithelioid osteoblasts

Explanation

Aggressive osteoblastomas are characterized by the presence of plump, epithelioid osteoblasts. Despite their aggressive local behavior, they lack the atypical mitoses and destructive permeation seen in osteosarcoma.

Question 15

Topic: Biology, Genetics & Bone Healing

A 35-year-old female presents with an unresectable giant cell tumor of the sacrum. Which targeted pharmacologic therapy is most appropriate to induce tumor consolidation?

. Imatinib
. Denosumab
. Zoledronic acid
. Rituximab
. Methotrexate

Correct Answer & Explanation

. Denosumab

Explanation

Denosumab is a monoclonal antibody against RANKL, which is overexpressed by the neoplastic stromal cells of GCT. It prevents osteoclast-like giant cell formation and induces profound tumor bone consolidation.

Question 16

Topic: Biology, Genetics & Bone Healing

What is the most critical factor in preventing local recurrence of a sacral chordoma following surgical management?

. Adjuvant chemotherapy
. Neoadjuvant radiation therapy
. Obtaining wide, negative margins en bloc
. Postoperative bisphosphonate therapy
. Preoperative embolization

Correct Answer & Explanation

. Obtaining wide, negative margins en bloc

Explanation

Chordomas are notoriously chemoresistant and radioresistant. Complete en bloc excision with wide, negative margins is the most important factor in preventing local recurrence and achieving long-term survival.

Question 17

Topic: Biology, Genetics & Bone Healing

A 22-year-old male presents with dull, aching back pain that is not completely relieved by NSAIDs. Imaging reveals an expansile, radiolucent lesion measuring 3.5 cm in the posterior elements of L3. Histology shows disorganized osteoid surrounded by plump osteoblasts. Which of the following differentiates this lesion from an osteoid osteoma?

. Presence of a cartilaginous cap
. Size greater than 2 cm
. Location in the anterior vertebral body
. Absence of woven bone
. Malignant transformation potential

Correct Answer & Explanation

. Size greater than 2 cm

Explanation

Osteoblastoma and osteoid osteoma share similar histologic features, including vascular connective tissue and woven bone lined by osteoblasts. They are primarily distinguished by size, with osteoblastoma defined as being larger than 2 cm.

Question 18

Topic: Biology, Genetics & Bone Healing

A 32-year-old female undergoes curettage of an epiphyseal lytic lesion in the proximal tibia. Histology shows numerous multinucleated giant cells in a background of mononuclear stromal cells. If systemic therapy is required for unresectable disease, which cell surface receptor is targeted by the most appropriate pharmacological agent?

. HER2
. VEGFR
. RANKL
. PDGFR
. CD20

Correct Answer & Explanation

. RANKL

Explanation

The diagnosis is a giant cell tumor of bone. Denosumab, a monoclonal antibody, targets RANKL expressed by the neoplastic mononuclear stromal cells, preventing the recruitment and activation of osteoclast-like giant cells.

Question 19

Topic: Biology, Genetics & Bone Healing

A 65-year-old man with a history of renal cell carcinoma presents with acute myelopathy due to a pathologic fracture of L2. Decompression and stabilization are planned. Which preoperative intervention is most critical?

. Systemic chemotherapy
. Bisphosphonate infusion
. Preoperative selective arterial embolization
. Neoadjuvant radiation therapy
. Administration of high-dose denosumab

Correct Answer & Explanation

. Preoperative selective arterial embolization

Explanation

Renal cell carcinoma and thyroid carcinoma metastases are notoriously hypervascular. Preoperative selective arterial embolization is highly recommended to significantly reduce intraoperative blood loss during surgical decompression.

Question 20

Topic: Biology, Genetics & Bone Healing

A 35-year-old woman presents with a destructive lytic lesion in the sacrum. Biopsy reveals multinucleated giant cells intermixed with mononuclear stromal cells. The stromal cells are positive for H3F3A mutation. What is the most effective medical adjunct to surgery?

. Zoledronic acid
. Methotrexate
. Denosumab
. Imatinib
. Doxorubicin

Correct Answer & Explanation

. Denosumab

Explanation

The diagnosis is a Giant Cell Tumor (GCT) of bone, confirmed by the H3F3A mutation in the neoplastic stromal cells. Denosumab, a RANKL inhibitor, is highly effective in downregulating the osteoclast-like giant cells and creating a calcified rim, aiding in surgical resection.

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