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1. General Principles & Basic Science MCQs

Practice Set 636 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 12701

Topic: Biomechanics & Biomaterials

The 'creep' property of a material refers to its time-dependent deformation under constant stress. In the context of orthopedic implants, a material with high creep resistance is generally preferred for components subjected to:

. Acute, high-impact loads.
. Cyclic, low-magnitude loads.
. Sustained, constant loads.
. Rapid, dynamic torsional loads.
. Loads primarily in shear.

Correct Answer & Explanation

. Sustained, constant loads.

Explanation

High creep resistance is desirable for implants subjected to sustained, constant loads, such as the acetabular component of a total hip arthroplasty, where the body weight can exert a continuous load. Creep deformation over time under these constant loads can lead to dimensional changes, implant loosening, or failure. Fatigue resistance is more relevant for cyclic loads, and yield strength/ultimate tensile strength for acute high-impact loads.

Question 12702

Topic: Biology, Genetics & Bone Healing

What is the primary mechanism of action for bisphosphonates in treating osteoporosis?

. Stimulating osteoblast proliferation and bone formation.
. Inhibiting parathyroid hormone (PTH) release.
. Directly binding to and inactivating osteoclasts.
. Inducing osteoclast apoptosis and inhibiting their activity.
. Increasing calcium absorption from the gut.

Correct Answer & Explanation

. Inducing osteoclast apoptosis and inhibiting their activity.

Explanation

Bisphosphonates are potent antiresorptive agents. They are taken up by osteoclasts during bone resorption and then disrupt the osteoclast's mevalonate pathway, leading to impaired osteoclast function, reduced survival, and ultimately apoptosis (programmed cell death). This effectively decreases the rate of bone resorption, allowing osteoblast-mediated formation to catch up, leading to increased bone mineral density. They do not directly stimulate osteoblasts, inactivate PTH, or increase gut calcium absorption.

Question 12703

Topic: 1. General Principles & Basic Science

The 'tidemark' in articular cartilage represents the interface between which two zones?

. Superficial tangential zone and middle transitional zone.
. Middle transitional zone and deep radial zone.
. Deep radial zone and calcified cartilage.
. Calcified cartilage and subchondral bone.
. Articular surface and superficial tangential zone.

Correct Answer & Explanation

. Middle transitional zone and deep radial zone.

Explanation

The tidemark is a wavy, basophilic line that demarcates the boundary between the deep radial zone (uncalcified cartilage) and the calcified cartilage layer within articular cartilage. It is an important histological landmark and represents a region of active remodeling, playing a role in the integrity of the cartilage-bone interface. The calcified cartilage, in turn, interfaces with the subchondral bone, separated by a cement line.

Question 12704

Topic: 1. General Principles & Basic Science

Regarding the structural hierarchy of a tendon, what is the smallest organizational unit that contains collagen fibrils?

. Tendon fascicle
. Endotenon
. Collagen fiber
. Fibril bundle
. Tendon proper

Correct Answer & Explanation

. Fibril bundle

Explanation

The hierarchical organization of a tendon is: Tropocollagen molecules aggregate to form collagen microfibrils, which aggregate to form collagen fibrils. Collagen fibrils then form fibril bundles. Multiple fibril bundles make up a collagen fiber. Collagen fibers are grouped into fascicles, which are surrounded by endotenon. The entire tendon is surrounded by epitenon. So, the fibril bundle is the smallest unit containing multiple collagen fibrils.

Question 12705

Topic: 1. General Principles & Basic Science

A patient undergoes a peripheral nerve repair. Which factor is LEAST likely to positively influence the outcome of nerve regeneration?

. Younger patient age.
. Sharp transection of the nerve.
. Short gap between nerve ends.
. Proximal nerve injury (e.g., brachial plexus).
. Primary repair without tension.

Correct Answer & Explanation

. Proximal nerve injury (e.g., brachial plexus).

Explanation

Proximal nerve injuries (e.g., at the brachial plexus or root level) generally have a poorer prognosis for regeneration compared to distal injuries. This is because the distance for axonal regrowth to the target muscle or sensory receptor is much longer, increasing the likelihood of misdirection, neuroma formation, and muscle atrophy before reinnervation. Younger age, sharp transection (clean injury), short gaps, and tension-free primary repair all positively influence outcomes.

Question 12706

Topic: 1. General Principles & Basic Science

Which type of joint receptor is primarily responsible for sensing extreme joint positions and potential tissue damage?

. Ruffini endings
. Pacinian corpuscles
. Golgi-Mazzoni corpuscles
. Free nerve endings
. Merkel nerve endings

Correct Answer & Explanation

. Free nerve endings

Explanation

Free nerve endings are ubiquitous in joint capsules, ligaments, synovium, and fat pads. They are polymodal, sensing noxious stimuli, inflammation, and extremes of mechanical deformation, thus acting as nociceptors and providing a sense of 'danger' or tissue damage. Ruffini endings sense static joint position and joint movement. Pacinian corpuscles detect dynamic changes in joint movement and pressure. Golgi-Mazzoni corpuscles are similar to Pacinian corpuscles. Merkel endings are primarily cutaneous mechanoreceptors.

Question 12707

Topic: Biology, Genetics & Bone Healing

What is the primary mechanism by which parathyroid hormone (PTH) initially increases serum calcium levels?

. Directly stimulating calcium absorption from the gut.
. Inhibiting calcium excretion by the kidneys.
. Increasing osteoblast activity to release calcium from bone matrix.
. Stimulating osteoclast activity and bone resorption.
. Converting calcidiol to calcitriol in the liver.

Correct Answer & Explanation

. Stimulating osteoclast activity and bone resorption.

Explanation

Parathyroid hormone (PTH) primarily increases serum calcium levels by stimulating osteoclast activity, which leads to the breakdown of bone matrix and release of calcium into the bloodstream. While PTH also acts on the kidneys to increase calcium reabsorption and stimulate calcitriol synthesis (which then enhances gut absorption), its immediate and direct effect on bone involves stimulating osteoclasts (indirectly, via osteoblasts, but resulting in resorption) to raise serum calcium. Osteoblasts are responsible for bone formation.

Question 12708

Topic: 1. General Principles & Basic Science

Which type of bone graft has both osteoconductive and osteoinductive properties, along with osteogenic potential?

. Autogenous cancellous bone graft
. Corticocancellous allograft
. Demineralized bone matrix (DBM)
. Synthetic calcium sulfate
. Hydroxyapatite ceramic

Correct Answer & Explanation

. Autogenous cancellous bone graft

Explanation

Autogenous cancellous bone graft is considered the 'gold standard' because it possesses all three essential properties for bone healing: osteogenesis (living osteoblasts and mesenchymal stem cells within the graft), osteoinduction (bone morphogenetic proteins and other growth factors), and osteoconduction (a scaffold for new bone growth). Allografts are primarily osteoconductive and osteoinductive (if DBM), but lack living cells (osteogenic). Synthetics are typically only osteoconductive.

Question 12709

Topic: Infection, Pharmacology & VTE

A 40-year-old male with a history of intravenous drug use presents with septic arthritis of the sacroiliac joint. He is febrile and has severe gluteal pain, worsened by hip flexion and abduction. What is the most appropriate initial management?

. Oral antibiotics
. CT-guided aspiration for culture and drainage
. Open surgical debridement
. Pain management and observation
. Systemic corticosteroids

Correct Answer & Explanation

. CT-guided aspiration for culture and drainage

Explanation

For suspected septic arthritis of the sacroiliac (SI) joint, especially in a high-risk patient like an intravenous drug user, the immediate priority after clinical suspicion is to confirm the diagnosis and identify the causative organism. A CT-guided aspiration allows for accurate fluid sampling for culture and Gram stain, as well as initial drainage of pus. Once the pathogen is identified, targeted intravenous antibiotics can be initiated. Oral antibiotics alone are insufficient for septic arthritis, and open surgical debridement is reserved for cases that fail percutaneous drainage or have extensive abscess formation.

Question 12710

Topic: Biology, Genetics & Bone Healing

A surgeon is evaluating a non-union in a long bone. The fracture site shows hypertrophic callus but no bridging across the gap, indicating inadequate stability. What is the primary biological stimulant for callus formation in bone healing?

. Vascularity
. Interfragmentary strain
. Oxygen tension
. Local growth factors
. Systemic hormones

Correct Answer & Explanation

. Interfragmentary strain

Explanation

While all options play a role in bone healing, interfragmentary strain (the amount of motion or micromovement at the fracture site) is the primarymechanicalstimulant for callus formation. Too much strain (inadequate stability) can lead to a hypertrophic non-union where abundant callus forms but fails to bridge the gap (as described). A moderate, controlled amount of strain stimulates robust callus formation, while very rigid fixation (minimal strain) leads to primary bone healing with little to no callus. Vascularity, oxygen tension, local growth factors, and systemic hormones are criticalbiologicalfactors, but strain is the key mechanical driver of callus.

Question 12711

Topic: Biology, Genetics & Bone Healing

A surgeon is considering different bone graft options for a non-union. Which type of bone graft provides the most robust osteoinductive and osteoconductive properties?

. Autograft (cancellous)
. Allograft (demineralized bone matrix - DBM)
. Allograft (cortical)
. Synthetic bone graft (e.g., calcium phosphate)
. Bone morphogenetic protein (BMP)

Correct Answer & Explanation

. Autograft (cancellous)

Explanation

Autogenous cancellous bone graft is considered the 'gold standard' for bone grafting due to its unparalleled biological properties. It possesses osteogenic potential (containing viable osteoblasts and mesenchymal stem cells), osteoinductive properties (containing growth factors like BMPs), and osteoconductive properties (providing a scaffold for new bone growth). No other graft material possesses all three properties to the same robust degree. Demineralized bone matrix (DBM) is osteoinductive and osteoconductive but not osteogenic. Cortical allograft is primarily osteoconductive. Synthetic grafts are mainly osteoconductive. BMPs are highly osteoinductive but require a carrier and lack osteogenic cells.

Question 12712

Topic: Biology, Genetics & Bone Healing

A 70-year-old male presents with worsening bowing of his right tibia and increasing warmth and pain in the affected leg. Radiographs show cortical thickening, bone expansion, and a 'blade of grass' or 'V-shaped' osteolytic front in the tibia. Serum alkaline phosphatase is significantly elevated, and urinary hydroxyproline levels are also high. What is the most appropriate initial pharmacological treatment?

. Calcium and Vitamin D supplementation
. Oral bisphosphonates (e.g., alendronate)
. Teriparatide (recombinant PTH)
. Calcitonin
. Denosumab

Correct Answer & Explanation

. Oral bisphosphonates (e.g., alendronate)

Explanation

The clinical and radiographic findings, along with elevated alkaline phosphatase and urinary hydroxyproline, are characteristic of Paget's disease of bone. Bisphosphonates are the first-line treatment for symptomatic Paget's disease, as they inhibit osteoclast activity, reducing bone turnover, pain, and biochemical markers. Calcium and Vitamin D are general supplements but not specific treatments for Paget's. Teriparatide is an anabolic agent for severe osteoporosis. Calcitonin is less potent than bisphosphonates. Denosumab is also an anti-resorptive agent but typically reserved for cases where bisphosphonates are contraindicated or ineffective.

Question 12713

Topic: Infection, Pharmacology & VTE

A 5-year-old child presents with a high fever, refusal to bear weight on his left leg, and exquisite tenderness over the distal metaphysis of the left femur. Laboratory tests show elevated ESR, CRP, and WBC count. Radiographs initially appear normal. What is the most likely diagnosis, and what is the next most appropriate diagnostic step?

. Transient synovitis; rest and NSAIDs
. Septic arthritis; joint aspiration
. Osteomyelitis; MRI with contrast
. Juvenile idiopathic arthritis; rheumatology referral
. Stress fracture; bone scan

Correct Answer & Explanation

. Osteomyelitis; MRI with contrast

Explanation

The constellation of fever, refusal to bear weight, localized bony tenderness, and elevated inflammatory markers in a child is highly suggestive of acute osteomyelitis. While radiographs may initially be normal, MRI with contrast is the most sensitive and specific imaging modality to confirm the diagnosis, localize the infection, and assess for abscess formation. Septic arthritis presents with joint pain and refusal to bear weight but typically involves joint effusions and pain with range of motion. Transient synovitis is a diagnosis of exclusion, usually with lower inflammatory markers and no specific bony tenderness. Juvenile idiopathic arthritis is a chronic condition. A stress fracture would not present with acute fever and high inflammatory markers.

Question 12714

Topic: Biology, Genetics & Bone Healing

Which phase of bone healing is characterized by the formation of a soft callus by chondroblasts and fibroblasts, bridging the fracture gap?

. Inflammation phase
. Soft callus formation phase
. Hard callus formation phase
. Remodeling phase
. Revascularization phase

Correct Answer & Explanation

. Soft callus formation phase

Explanation

Bone healing traditionally involves several overlapping phases. The 'soft callus formation phase' (also known as the reparative or proliferation phase) immediately follows the inflammatory phase. During this phase, fibroblasts and chondroblasts proliferate, forming a fibrous and cartilaginous callus that bridges the fracture gap, providing initial stability. The inflammatory phase is characterized by hematoma formation and cell recruitment. The hard callus phase involves endochondral ossification and woven bone formation. The remodeling phase is the longest, replacing woven bone with lamellar bone. Revascularization occurs throughout these phases.

Question 12715

Topic: Infection, Pharmacology & VTE

A 60-year-old male with a history of alcohol abuse presents with acute, severe pain, swelling, and redness in his right first metatarsophalangeal (MTP) joint. Synovial fluid aspiration reveals needle-shaped, negatively birefringent crystals. What is the most appropriate initial pharmacological treatment for the acute attack?

. Allopurinol
. Febuxostat
. Probenecid
. Colchicine
. Prednisone

Correct Answer & Explanation

. Colchicine

Explanation

The clinical presentation and presence of needle-shaped, negatively birefringent crystals in the synovial fluid are diagnostic of acute gouty arthritis. For an acute attack, the primary goal is rapid pain and inflammation control. Colchicine, NSAIDs, and corticosteroids (such as oral prednisone or intra-articular injection) are the mainstays of acute treatment. Allopurinol, febuxostat, and probenecid are urate-lowering therapies used for long-term management to prevent recurrent attacks, but they are generally contraindicated during an acute flare as they can paradoxically worsen the attack by mobilizing urate crystals.

Question 12716

Topic: Infection, Pharmacology & VTE

A 60-year-old diabetic male undergoes an open reduction and internal fixation of a distal tibia fracture. Six months post-operatively, he presents with persistent drainage from the surgical site, pain, and erythema. Plain radiographs show sequestrum formation and involucrum. Laboratory markers indicate mildly elevated CRP, but ESR is normal. A deep tissue culture grows Staphylococcus aureus. What is the most appropriate definitive management for this chronic osteomyelitis?

. Long-term oral antibiotics alone
. Intravenous antibiotics for 6 weeks followed by oral antibiotics for 3 months
. Surgical debridement, sequestrectomy, bone grafting, and targeted antibiotic therapy
. Amputation of the affected limb
. Hyperbaric oxygen therapy

Correct Answer & Explanation

. Surgical debridement, sequestrectomy, bone grafting, and targeted antibiotic therapy

Explanation

The presence of persistent drainage, radiographic evidence of sequestrum and involucrum, and a positive deep tissue culture confirm chronic osteomyelitis. For chronic osteomyelitis, surgical debridement (including sequestrectomy, removal of infected hardware, and debridement of necrotic bone), followed by reconstruction (e.g., bone grafting, muscle flaps if needed) and prolonged targeted antibiotic therapy (intravenous initially, then oral) is the cornerstone of definitive treatment. Long-term oral antibiotics alone are insufficient due to the presence of devitalized bone and biofilm. Amputation is a salvage procedure. Hyperbaric oxygen therapy is an adjunct, not a standalone definitive treatment.

Question 12717

Topic: Infection, Pharmacology & VTE

A 70-year-old female presents with acute, severe pain in her right knee, accompanied by warmth, swelling, and redness. She is afebrile. Synovial fluid aspiration reveals rhomboid-shaped, positively birefringent crystals. What is the most likely diagnosis?

. Gout
. Septic arthritis
. Calcium pyrophosphate dihydrate (CPPD) crystal deposition disease (pseudogout)
. Rheumatoid arthritis flare
. Osteoarthritis flare

Correct Answer & Explanation

. Calcium pyrophosphate dihydrate (CPPD) crystal deposition disease (pseudogout)

Explanation

The presence of rhomboid-shaped, positively birefringent crystals in the synovial fluid is diagnostic of calcium pyrophosphate dihydrate (CPPD) crystal deposition disease, commonly known as pseudogout. Gout is characterized by needle-shaped, negatively birefringent crystals. Septic arthritis requires ruling out with cell count and culture, but crystal findings point away from it. Rheumatoid arthritis is a chronic inflammatory polyarthritis, and an acute flare would not typically show these crystals. Osteoarthritis is degenerative and does not typically involve crystal deposition unless it's a co-existing condition.

Question 12718

Topic: 1. General Principles & Basic Science

A junior colleague asks for advice on preparing for the orthopedic viva exam. Which piece of advice most directly addresses how to impress examiners and score well?

. Memorize every textbook page word-for-word.
. Practice answering questions out loud, focusing on a structured, concise delivery with clear headings (even if verbal) and prioritizing key information.
. Only study rare and complex cases.
. Avoid eye contact to show concentration.
. Talk continuously without pausing for the examiner's input.

Correct Answer & Explanation

. Practice answering questions out loud, focusing on a structured, concise delivery with clear headings (even if verbal) and prioritizing key information.

Explanation

For viva exams, the ability to articulate knowledge in a structured, concise, and logical manner is key. Practicing out loud with a focus on clear presentation (e.g., 'My differential diagnosis would include...', 'Initial investigations would be...') allows candidates to demonstrate systematic thinking, essential for high marks. Examiners value clarity, conciseness, and the ability to prioritize information, rather than just raw memorization or continuous talking.

Question 12719

Topic: 1. General Principles & Basic Science

When asked about the management of osteomyelitis. To achieve a high score, your response should emphasize:

. Only the surgical debridement aspects.
. Prolonged antibiotic therapy without identifying the organism.
. A multidisciplinary approach involving infection specialists, meticulous surgical debridement, appropriate targeted antibiotic therapy (often IV followed by oral), and consideration of bone reconstruction.
. Exclusively focusing on hyperbaric oxygen therapy.
. Stating it's a difficult condition to treat.

Correct Answer & Explanation

. A multidisciplinary approach involving infection specialists, meticulous surgical debridement, appropriate targeted antibiotic therapy (often IV followed by oral), and consideration of bone reconstruction.

Explanation

Osteomyelitis management is complex and requires a holistic, multidisciplinary approach. A high-scoring answer would detail the need for appropriate imaging, meticulous surgical debridement (often repeated), precise microbiological diagnosis via tissue samples, and targeted, prolonged antibiotic therapy guided by sensitivity. Involving infection specialists is key. This demonstrates a comprehensive understanding of a challenging condition, beyond just surgery or antibiotics in isolation.

Question 12720

Topic: Infection, Pharmacology & VTE

When discussing the complications of a musculoskeletal infection (e.g., septic arthritis), what aspect is most indicative of a thorough understanding beyond just listing the sequelae?

. Naming all possible causative organisms.
. Recalling the specific volume of joint fluid aspirated.
. Explaining the pathophysiology of joint destruction, identifying factors influencing prognosis, and detailing long-term consequences and rehabilitation needs.
. Focusing only on the acute pain management.
. Stating that the patient will likely need surgery.

Correct Answer & Explanation

. Explaining the pathophysiology of joint destruction, identifying factors influencing prognosis, and detailing long-term consequences and rehabilitation needs.

Explanation

A deep understanding of septic arthritis involves more than just recognizing the infection. It requires explaining the mechanisms of articular cartilage destruction, identifying prognostic factors (e.g., delay to diagnosis, organism virulence), and outlining the potential long-term sequelae such as joint stiffness, degenerative changes, and the need for ongoing rehabilitation or even reconstructive surgery. This shows a comprehensive grasp of the disease process and its implications.

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