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1. General Principles & Basic Science MCQs

Practice Set 361 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 7201

Topic: Biology, Genetics & Bone Healing

Recombinant human parathyroid hormone (teriparatide) is utilized in the treatment of severe osteoporosis. What is the underlying mechanism by which it exerts an anabolic effect on bone?

. Direct inhibition of osteoclast apoptosis
. Intermittent administration stimulates osteoblast survival and bone formation
. Continuous administration suppresses RANKL expression
. Direct binding to osteoclasts to inhibit acid secretion
. Stimulation of sclerostin release from osteocytes

Correct Answer & Explanation

. Direct inhibition of osteoclast apoptosis

Explanation

While continuous PTH exposure upregulates RANKL and causes net bone resorption, intermittent administration of PTH (teriparatide) stimulates osteoblast proliferation and survival, resulting in net bone formation.

Question 7202

Topic: 1. General Principles & Basic Science

Which of the following arteries provides the predominant blood supply to the weight-bearing portion of the adult femoral head?

. Artery of the ligamentum teres
. Anterior branch of the obturator artery
. Lateral epiphyseal branch of the medial femoral circumflex artery
. Ascending branch of the lateral femoral circumflex artery
. Inferior gluteal artery

Correct Answer & Explanation

. Artery of the ligamentum teres

Explanation

The medial femoral circumflex artery (MFCA) is the primary blood supply to the femoral head. Specifically, its lateral epiphyseal branches penetrate the joint capsule to supply the critical superior and weight-bearing regions.

Question 7203

Topic: 1. General Principles & Basic Science

Which of the following characteristics accurately describes the superficial zone of normal articular cartilage compared to the deeper zones?

. Highest concentration of proteoglycans
. Lowest concentration of water
. Collagen fibers oriented perpendicularly to the joint surface
. Highest concentration of collagen
. Primarily composed of Type I collagen

Correct Answer & Explanation

. Highest concentration of proteoglycans

Explanation

The superficial zone of articular cartilage has the highest water and collagen content, and the lowest proteoglycan content. The collagen fibers are oriented parallel to the joint surface to resist shear forces.

Question 7204

Topic: Surgical Anatomy & Approaches

The sciatic nerve typically exits the greater sciatic foramen inferior to the piriformis muscle. In the most common anatomical variant (Beaton and Anson Type B), how does the sciatic nerve traverse the piriformis?

. The entire nerve passes superior to the piriformis.
. The entire nerve pierces the belly of the piriformis.
. The common peroneal division pierces the piriformis while the tibial division passes inferiorly.
. The tibial division pierces the piriformis while the common peroneal division passes inferiorly.
. The common peroneal division passes superior to the piriformis while the tibial division passes inferiorly.

Correct Answer & Explanation

. The entire nerve passes superior to the piriformis.

Explanation

In the most common anatomical variation of the sciatic nerve (approx. 10-15% of the population), the common peroneal division pierces the piriformis muscle, while the tibial division exits normally beneath the muscle.

Question 7205

Topic: Biology, Genetics & Bone Healing

Which of the following transcription factors is essential for the commitment of mesenchymal stem cells to the osteoblast lineage?

. Sox9
. Runx2 (Cbfa1)
. PPAR-gamma
. MyoD
. HIF-1 alpha

Correct Answer & Explanation

. Sox9

Explanation

Runx2 (also known as Cbfa1) is the master transcription factor required for osteoblast differentiation. Sox9 drives chondrogenesis, while PPAR-gamma drives adipogenesis.

Question 7206

Topic: 1. General Principles & Basic Science

What is the primary function of Cathepsin K in osteoclastic bone resorption?

. Dissolution of hydroxyapatite crystals
. Cleavage of type I collagen in an acidic environment
. Binding of RANKL to RANK
. Formation of the ruffled border
. Transport of protons into the Howship lacuna

Correct Answer & Explanation

. Dissolution of hydroxyapatite crystals

Explanation

Cathepsin K is a lysosomal protease secreted by osteoclasts that degrades type I collagen and other bone matrix proteins. It functions optimally in the acidic environment created by the vacuolar H+-ATPase pump.

Question 7207

Topic: Biomechanics & Biomaterials

On a stress-strain curve, the total area under the curve up to the point of material failure represents which of the following mechanical properties?

. Toughness
. Stiffness
. Ductility
. Yield strength
. Viscoelasticity

Correct Answer & Explanation

. Toughness

Explanation

Toughness is the ability of a material to absorb energy and plastically deform before fracturing, represented by the total area under the stress-strain curve. Stiffness is represented by the slope of the elastic region (Young's modulus).

Question 7208

Topic: 1. General Principles & Basic Science

Which zone of articular cartilage is characterized by the highest water content and collagen fibers oriented parallel to the joint surface?

. Superficial (tangential) zone
. Middle (transitional) zone
. Deep (radial) zone
. Calcified zone
. Tidemark

Correct Answer & Explanation

. Superficial (tangential) zone

Explanation

The superficial zone of articular cartilage has the highest water content, the lowest proteoglycan concentration, and collagen fibers aligned parallel to the joint surface to resist shear forces.

Question 7209

Topic: 1. General Principles & Basic Science

Following a complete peripheral nerve transection, which cells are primarily responsible for clearing myelin debris during Wallerian degeneration in the distal nerve stump?

. Schwann cells and macrophages
. Astrocytes and microglia
. Oligodendrocytes
. Fibroblasts
. Endothelial cells

Correct Answer & Explanation

. Schwann cells and macrophages

Explanation

Wallerian degeneration involves the breakdown of the axon and myelin distal to a nerve injury. Schwann cells initially degrade myelin, followed by recruited macrophages which clear the remaining debris to allow for axonal regeneration.

Question 7210

Topic: 1. General Principles & Basic Science

In the load-deformation curve of a healthy tendon, the initial non-linear 'toe region' is primarily due to:

. Breaking of collagen cross-links
. Uncrimping of resting type I collagen fibers
. Plastic deformation of the extracellular matrix
. Fluid extrusion from the ground substance
. Elastic deformation of individual collagen fibrils

Correct Answer & Explanation

. Breaking of collagen cross-links

Explanation

The toe region corresponds to the stretching out, or 'uncrimping,' of the naturally crimped type I collagen fibers when a load is first applied. Once uncrimped, the tendon enters the linear elastic region.

Question 7211

Topic: Biology, Genetics & Bone Healing

Commercially prepared demineralized bone matrix (DBM) is best described as possessing which of the following biological properties?

. Osteogenic only
. Osteoconductive and osteoinductive
. Osteogenic and osteoinductive
. Osteoinductive only
. Osteoconductive, osteoinductive, and osteogenic

Correct Answer & Explanation

. Osteogenic only

Explanation

DBM provides a collagenous scaffold (osteoconductive) and contains viable bone morphogenetic proteins (BMPs) (osteoinductive). Because it lacks living cells, it is not osteogenic.

Question 7212

Topic: Biomechanics & Biomaterials

Which type of wear in total joint arthroplasty is characterized by the transfer of material from one surface to another due to localized micro-welding and subsequent tearing?

. Abrasive wear
. Adhesive wear
. Third-body wear
. Fretting wear
. Fatigue wear

Correct Answer & Explanation

. Abrasive wear

Explanation

Adhesive wear occurs when two surfaces slide against each other, creating localized micro-welds that break and tear material away. Abrasive wear occurs when a harder surface or particle plows into a softer surface.

Question 7213

Topic: 1. General Principles & Basic Science

During the remodeling phase of ligament healing, the structural integrity of the extracellular matrix improves primarily due to which of the following processes?

. Replacement of type I collagen with type II collagen
. Replacement of type III collagen with type I collagen
. A massive increase in proteoglycan content
. Rapid proliferation of fibroblasts
. Angiogenesis and hematoma formation

Correct Answer & Explanation

. Replacement of type I collagen with type II collagen

Explanation

In the initial phases of healing, fibroblasts predominantly synthesize disorganized type III collagen. During remodeling, this is gradually replaced by stronger, highly cross-linked type I collagen.

Question 7214

Topic: Biology, Genetics & Bone Healing

Primary (strain-free) bone healing relies on absolute stability and achieves union via which of the following mechanisms?

. Endochondral ossification
. Intramembranous ossification
. Haversian remodeling with cutting cones
. Chondrocyte hypertrophy and apoptosis
. Callus formation and mineralization

Correct Answer & Explanation

. Endochondral ossification

Explanation

Primary bone healing occurs without a cartilaginous callus when absolute stability (e.g., compression plating) is achieved. It proceeds directly via osteoclastic cutting cones followed by osteoblastic bone deposition (Haversian remodeling).

Question 7215

Topic: 1. General Principles & Basic Science

Which lubrication mechanism predominates in articular cartilage under conditions of high contact load and low sliding velocity?

. Hydrodynamic lubrication
. Elastohydrodynamic lubrication
. Boundary lubrication
. Squeeze-film lubrication
. Weeping lubrication

Correct Answer & Explanation

. Hydrodynamic lubrication

Explanation

Boundary lubrication is mediated by molecules like lubricin (PRG4) on the cartilage surface and operates under high-load, low-velocity conditions. Fluid-film lubrication typically dominates during high-velocity motions.

Question 7216

Topic: Biomechanics & Biomaterials

Fretting corrosion in orthopedic implants is most commonly observed at which of the following interfaces?

. Between a titanium stem and a cobalt-chrome head
. Between a bone screw head and a bone plate hole
. Between an un-cemented stem and surrounding cortical bone
. Between a polyethylene liner and a metal acetabular shell
. Between a ceramic head and a polyethylene liner

Correct Answer & Explanation

. Between a titanium stem and a cobalt-chrome head

Explanation

Fretting corrosion occurs due to repetitive micromotion between two closely apposed metal surfaces, mechanically removing the passive oxide layer. It is classically seen at the screw-plate interface.

Question 7217

Topic: 1. General Principles & Basic Science

The primary blood supply to the adult femoral head is derived from the:

. Artery of the ligamentum teres
. Medial femoral circumflex artery
. Lateral femoral circumflex artery
. Inferior gluteal artery
. Superior gluteal artery

Correct Answer & Explanation

. Artery of the ligamentum teres

Explanation

The medial femoral circumflex artery (MFCA) provides the dominant blood supply to the adult femoral head via its lateral epiphyseal branches. The artery of the ligamentum teres contributes a negligible amount in adults.

Question 7218

Topic: Physiology & Rehabilitation

Which of the following characteristics best describes Type I (slow-twitch) skeletal muscle fibers?

. High glycolytic capacity and rapid fatigue
. Low myoglobin content and fast twitch speed
. High oxidative capacity and resistance to fatigue
. Low mitochondria density and high force production
. Anaerobic metabolism and high glycogen stores

Correct Answer & Explanation

. High glycolytic capacity and rapid fatigue

Explanation

Type I muscle fibers are 'slow-twitch' fibers that rely on aerobic metabolism. They are rich in mitochondria and myoglobin, granting them high oxidative capacity and significant resistance to fatigue.

Question 7219

Topic: Biology, Genetics & Bone Healing

Parathyroid hormone (PTH) stimulates bone resorption primarily by binding to receptors on the surface of which cell type?

. Osteoclast precursors
. Mature osteoclasts
. Osteoblasts
. Macrophages
. Chondrocytes

Correct Answer & Explanation

. Osteoclast precursors

Explanation

PTH binds to the PTH1R receptor on osteoblasts. This stimulates osteoblasts to upregulate RANKL and downregulate OPG, indirectly driving osteoclast differentiation and bone resorption.

Question 7220

Topic: 1. General Principles & Basic Science

Which of the following geometric modifications most significantly increases the pull-out strength of a bone suture anchor?

. Decreasing the thread pitch
. Increasing the inner core diameter while keeping outer diameter constant
. Decreasing the outer diameter of the threads
. Increasing the thread pitch
. Inserting the anchor parallel to the direction of pull

Correct Answer & Explanation

. Decreasing the thread pitch

Explanation

Decreasing the thread pitch means having more threads per inch, which increases the surface area of bone-thread engagement and maximizes pull-out strength. Increasing the outer diameter or decreasing the inner core diameter also improves fixation.

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