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1. General Principles & Basic Science MCQs

Practice Set 15 of 789

This practice set contains high-yield board review questions covering key concepts in 1. General Principles & Basic Science. Each clinical scenario is designed to test your diagnostic and management skills relevant to this subspecialty.

Question 281

Topic: Biology, Genetics & Bone Healing

Teriparatide therapy reduces the risk of future vertebral compression fractures primarily through which mechanism of action?

. Directly stimulating osteoblast formation and action
. Inhibiting osteoclast-mediated bone resorption
. Binding to and neutralizing RANK ligand
. Inhibiting the secretion of sclerostin
. Binding to hydroxyapatite crystals to directly increase density

Correct Answer & Explanation

. Directly stimulating osteoblast formation and action

Explanation

Teriparatide is a recombinant parathyroid hormone (PTH 1-34) that acts as a potent anabolic agent when given intermittently. It directly stimulates osteoblast activity, leading to new bone formation and improved trabecular microarchitecture.

Question 282

Topic: Biology, Genetics & Bone Healing

Which of the following conditions represents an absolute medical contraindication to initiating oral bisphosphonate therapy in a patient with an osteoporotic compression fracture?

. History of deep vein thrombosis
. Severe renal impairment (Creatinine Clearance < 30 mL/min)
. Well-controlled gastroesophageal reflux disease (GERD)
. Previous history of breast cancer
. Mild asymptomatic hypercalcemia

Correct Answer & Explanation

. Severe renal impairment (Creatinine Clearance < 30 mL/min)

Explanation

Bisphosphonates are excreted unchanged via the kidneys and can accumulate, causing toxicity. They are absolutely contraindicated in patients with severe renal impairment, typically defined as a creatinine clearance of less than 30 to 35 mL/min.

Question 283

Topic: Biology, Genetics & Bone Healing

An 80-year-old female with known osteoporosis presents with severe back pain and an acute L2 compression fracture. Under what specific circumstance would open operative decompression and stabilization be indicated over percutaneous cement augmentation?

. 15% loss of anterior vertebral body height
. Failure of conservative treatment after 4 weeks
. Presence of severe axial back pain upon weight-bearing
. Progressive neurologic deficit secondary to retropulsed bone
. Presence of an intravertebral vacuum cleft on extension views

Correct Answer & Explanation

. Progressive neurologic deficit secondary to retropulsed bone

Explanation

A progressive neurologic deficit caused by canal compromise from retropulsed bone fragments is a clear indication for surgical decompression. Cement augmentation alone cannot decompress the neural elements and carries a risk of exacerbating the stenosis.

Question 284

Topic: Biology, Genetics & Bone Healing
According to the World Health Organization (WHO) criteria, severe (or established) osteoporosis is defined by a fragility fracture and a Dual-energy X-ray absorptiometry (DEXA) T-score of:
. > -1.0
. Between -1.0 and -2.5
. โ‰ค -2.5
. Between 0 and -1.0
. โ‰ค -1.5 without a fracture

Correct Answer & Explanation

. โ‰ค -2.5

Explanation

The WHO defines osteoporosis as a DEXA T-score of -2.5 or lower. The designation of "severe" or "established" osteoporosis is applied when a patient has a T-score of โ‰ค -2.5 combined with one or more fragility fractures.

Question 285

Topic: Biology, Genetics & Bone Healing

Denosumab is highly effective for patients with severe osteoporosis and recurrent vertebral fractures. What is its precise mechanism of action?

. Inhibition of the Wnt signaling pathway via sclerostin binding
. Activation of osteoprotegerin production by osteoblasts
. Stimulation of the parathyroid hormone receptor on osteoblasts
. Binding and inhibition of RANK Ligand (RANKL)
. Inhibition of cathepsin K to prevent matrix degradation

Correct Answer & Explanation

. Binding and inhibition of RANK Ligand (RANKL)

Explanation

Denosumab is a fully human monoclonal antibody that specifically binds to and inhibits RANK Ligand (RANKL). This prevents RANKL from activating the RANK receptor on osteoclast precursors, thereby profoundly inhibiting osteoclast formation, function, and survival.

Question 286

Topic: Infection, Pharmacology & VTE

A 75-year-old female presents with severe, unremitting back pain after a fall from standing height. MRI shows an acute L1 compression fracture. She has failed 6 weeks of conservative management. What is an absolute contraindication to performing a vertebroplasty?

. Involvement of the posterior vertebral body wall
. Retropulsion of bone into the spinal canal without neurologic deficit
. Active osteomyelitis at the affected level
. Patient age greater than 80 years
. Cortical disruption of the superior endplate

Correct Answer & Explanation

. Active osteomyelitis at the affected level

Explanation

Active infection (osteomyelitis or discitis) and uncorrectable coagulopathy are absolute contraindications to vertebroplasty and kyphoplasty. Asymptomatic retropulsion and posterior wall involvement are relative contraindications.

Question 287

Topic: Biology, Genetics & Bone Healing

Which medication provides the most rapid, specific analgesic effect for acute osteoporotic vertebral compression fractures within the first few weeks of injury?

. Oral alendronate
. Intravenous zoledronic acid
. Subcutaneous teriparatide
. Intranasal calcitonin
. Subcutaneous denosumab

Correct Answer & Explanation

. Intranasal calcitonin

Explanation

Intranasal calcitonin has been shown to provide a significant, early analgesic effect in acute osteoporotic vertebral compression fractures. It is often prescribed early in the fracture course specifically for this symptom-modifying property.

Question 288

Topic: Biology, Genetics & Bone Healing

A 68-year-old woman with a T-score of -3.0 sustains a T11 compression fracture. She is started on a daily subcutaneous medication that acts as an anabolic agent to stimulate bone formation. What is the mechanism of action of this medication?

. Inhibition of osteoclast action via RANKL binding
. Direct apoptosis of osteoclasts via bisphosphonate accumulation
. Recombinant human parathyroid hormone (PTH) analog action
. Sclerostin inhibition
. Selective estrogen receptor agonism

Correct Answer & Explanation

. Recombinant human parathyroid hormone (PTH) analog action

Explanation

Teriparatide is a recombinant human PTH analog administered daily subcutaneously. It acts as an anabolic agent by stimulating osteoblast activity and directly forming new bone.

Question 289

Topic: 1. General Principles & Basic Science

During a kyphoplasty for an L2 compression fracture, the surgeon notices a sudden drop in the patient's blood pressure, tachycardia, and a decrease in oxygen saturation immediately after cement injection. What is the most likely cause?

. Fat embolism syndrome
. Polymethylmethacrylate (PMMA) pulmonary embolism
. Epidural hematoma
. Anaphylaxis to radiopaque contrast dye
. Acute myocardial infarction

Correct Answer & Explanation

. Polymethylmethacrylate (PMMA) pulmonary embolism

Explanation

PMMA cement pulmonary embolism is a recognized, potentially life-threatening complication of vertebroplasty/kyphoplasty. It is caused by cement extravasation into the paravertebral venous plexus, tracking into the inferior vena cava and pulmonary arteries.

Question 290

Topic: Biology, Genetics & Bone Healing

A 78-year-old patient with severe osteoporosis presents with multiple wedge compression fractures.

According to the World Health Organization (WHO) definition, severe osteoporosis is diagnosed when a patient has a fragility fracture and a DEXA T-score of:

. -1.0 or less
. -1.5 or less
. -2.0 or less
. -2.5 or less
. -3.0 or less

Correct Answer & Explanation

. -2.5 or less

Explanation

The WHO defines osteoporosis as a DEXA T-score of -2.5 or lower. Severe (or established) osteoporosis is defined as a T-score of -2.5 or lower in the presence of one or more fragility fractures.

Question 291

Topic: Biology, Genetics & Bone Healing

When evaluating a patient's risk for future osteoporotic fractures using the FRAX tool, which of the following is NOT included as a primary variable in the calculation?

. Current smoking status
. Previous fragility fracture
. Serum Vitamin D level
. Use of systemic glucocorticoids
. Rheumatoid arthritis

Correct Answer & Explanation

. Serum Vitamin D level

Explanation

The FRAX (Fracture Risk Assessment Tool) algorithm evaluates 11 clinical risk factors including age, sex, BMI, prior fracture, parental hip fracture, current smoking, glucocorticoid use, rheumatoid arthritis, secondary osteoporosis, alcohol intake, and femoral neck BMD. Serum Vitamin D levels are not a variable.

Question 292

Topic: 1. General Principles & Basic Science

Romosozumab is a newer pharmacological agent used in patients with severe osteoporosis and multiple compression fractures. Its primary mechanism of action is:

. Inhibiting RANK ligand to prevent osteoclast maturation
. Binding to hydroxyapatite and inducing osteoclast apoptosis
. Monoclonal antibody targeting and inhibiting sclerostin
. Exogenous administration of parathyroid hormone
. Selective estrogen receptor modulation

Correct Answer & Explanation

. Monoclonal antibody targeting and inhibiting sclerostin

Explanation

Romosozumab is a humanized monoclonal antibody that binds to and inhibits sclerostin. This has a dual effect: increasing bone formation (anabolic) and decreasing bone resorption (anticatabolic).

Question 293

Topic: 1. General Principles & Basic Science
The "intravertebral vacuum cleft sign" seen on radiographs or CT of a vertebral body compression fracture is highly indicative of:
. Acute pyogenic osteomyelitis
. Tuberculosis of the spine (Pott's disease)
. Osteonecrosis of the vertebral body
. Multiple myeloma
. Paget's disease of bone

Correct Answer & Explanation

. Osteonecrosis of the vertebral body

Explanation

The intravertebral vacuum cleft sign represents gas (mostly nitrogen) filling a non-healing void, indicative of avascular necrosis (osteonecrosis) within the vertebral body. It is strongly associated with delayed vertebral collapse (Kรผmmell disease) and pseudarthrosis.

Question 294

Topic: 1. General Principles & Basic Science

For a patient undergoing kyphoplasty for an osteoporotic compression fracture, the polymethylmethacrylate (PMMA) cement should ideally be injected at which of the following consistencies to minimize the risk of venous extravasation?

. Liquid phase
. Doughy (toothpaste) phase
. Watery phase
. Fully hardened phase
. Powder phase

Correct Answer & Explanation

. Doughy (toothpaste) phase

Explanation

PMMA cement should be injected during the doughy (or toothpaste-like) phase. Injecting while it is too liquid significantly increases the risk of extravasation into the venous plexus, potentially leading to a pulmonary embolism.

Question 295

Topic: 1. General Principles & Basic Science

Which of the following is considered an absolute contraindication to performing a percutaneous vertebroplasty?

. Patient age greater than 85 years
. Chronic compression fracture over 1 year old
. Active systemic or spinal osteomyelitis
. Stable anterior wedge compression fracture
. Concurrent use of bisphosphonates

Correct Answer & Explanation

. Active systemic or spinal osteomyelitis

Explanation

Active systemic infection or localized spinal infection (such as osteomyelitis or discitis) is an absolute contraindication to PMMA injection. Injecting cement into an infected area can trap the infection and worsen the patient's condition.

Question 296

Topic: 1. General Principles & Basic Science

A 74-year-old female undergoes percutaneous vertebroplasty for a T12 compression fracture. Two hours postoperatively, she develops acute dyspnea, tachycardia, and pleuritic chest pain. What is the most likely etiology?

. Epidural hematoma
. Cement pulmonary embolism
. Fat embolism syndrome
. Myocardial infarction
. Spontaneous pneumothorax

Correct Answer & Explanation

. Cement pulmonary embolism

Explanation

Polymethylmethacrylate (PMMA) can extravasate into the paravertebral venous plexus and embolize to the lungs. Symptomatic cement pulmonary embolisms present with sudden acute dyspnea and chest pain shortly after the procedure.

Question 297

Topic: Biology, Genetics & Bone Healing

A patient with multiple osteoporotic compression fractures is evaluated for teriparatide therapy. This medication is strictly contraindicated in patients with a history of which of the following conditions?

. Peptic ulcer disease
. Deep vein thrombosis
. Paget disease of bone
. Rheumatoid arthritis
. Chronic kidney disease stage II

Correct Answer & Explanation

. Paget disease of bone

Explanation

Teriparatide is a recombinant parathyroid hormone analogue with an anabolic effect on bone. It carries a black box warning for osteosarcoma and is contraindicated in patients with Paget disease, prior skeletal radiation, or unexplained elevations of alkaline phosphatase.

Question 298

Topic: Biomechanics & Biomaterials

During a percutaneous vertebroplasty, what volume of PMMA injection is generally sufficient to achieve significant pain relief and stabilization in a typical thoracolumbar vertebral body?

. 0.5 to 1 cc
. 2 to 4 cc
. 8 to 10 cc
. 12 to 15 cc
. Complete 100% filling of the vertebral body volume

Correct Answer & Explanation

. 2 to 4 cc

Explanation

Clinical studies show that pain relief and mechanical stabilization do not require complete filling of the vertebral body. Filling approximately 15% of the vertebral volume, typically 2 to 4 cc in the thoracolumbar spine, is generally sufficient and minimizes leakage risk.

Question 299

Topic: 1. General Principles & Basic Science

A well-documented complication following vertebral augmentation procedures is adjacent segment vertebral fracture. What is the most widely accepted biomechanical mechanism contributing to this complication?

. Thermal necrosis of adjacent intervertebral discs
. Increased stiffness of the augmented vertebra
. Avascular necrosis of adjacent vertebrae due to vascular damage
. Cement extravasation directly into the epidural space
. Accelerated systemic osteoporosis from the PMMA monomer

Correct Answer & Explanation

. Increased stiffness of the augmented vertebra

Explanation

Augmenting an osteoporotic vertebral body with PMMA significantly increases its compressive stiffness. This creates a severe mechanical mismatch, transferring abnormally high stress to the adjacent softer, osteoporotic vertebrae, thereby increasing their fracture risk.

Question 300

Topic: Biology, Genetics & Bone Healing

Which medical therapy has been shown to uniquely provide acute analgesic effects for osteoporotic vertebral compression fractures, in addition to its anti-resorptive properties?

. Oral alendronate
. Intranasal calcitonin
. Subcutaneous teriparatide
. Intravenous zoledronic acid
. Oral raloxifene

Correct Answer & Explanation

. Intranasal calcitonin

Explanation

Intranasal calcitonin is unique among pharmacological osteoporosis treatments for having a documented acute analgesic effect. This effect is believed to be mediated through the release of endogenous endorphins and is useful in the acute phase of fracture management.

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