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1. General Principles & Basic Science MCQs

Practice Set 330 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 6581

Topic: 1. General Principles & Basic Science

Which portion of the knee meniscus contains the highest concentration of blood vessels, giving it the greatest potential for healing after surgical repair?

. Inner third (white-white zone)
. Middle third (red-white zone)
. Outer third (red-red zone)
. Anterior horn specifically
. Posterior root attachment only

Correct Answer & Explanation

. Inner third (white-white zone)

Explanation

The peripheral 10% to 30% (outer third or red-red zone) of the meniscus is vascularized by the perimeniscal capillary plexus. This vascularity confers a much higher healing potential compared to the avascular inner zones.

Question 6582

Topic: Biology, Genetics & Bone Healing

During the remodeling phase of tendon healing, the biomechanical strength of the tendon increases primarily due to the transition from:

. Type II to Type I collagen
. Type III to Type I collagen
. Type I to Type III collagen
. Type X to Type II collagen
. Type I to Type II collagen

Correct Answer & Explanation

. Type II to Type I collagen

Explanation

During the initial proliferative phase of tendon healing, immature Type III collagen is primarily deposited. In the remodeling phase, this is replaced by organized Type I collagen, significantly increasing the tensile strength of the tissue.

Question 6583

Topic: Biology, Genetics & Bone Healing

An autologous iliac crest bone graft provides osteoconduction, osteoinduction, and osteogenesis. Which of the following materials possesses ONLY osteoconductive properties?

. Demineralized bone matrix (DBM)
. Recombinant human BMP-2
. Calcium phosphate cement
. Vascularized fibula graft
. Bone marrow aspirate concentrate

Correct Answer & Explanation

. Demineralized bone matrix (DBM)

Explanation

Calcium phosphate cement acts solely as an osteoconductive scaffold. Demineralized bone matrix (DBM) is osteoinductive, while autografts provide osteoconductive, osteoinductive, and osteogenic properties.

Question 6584

Topic: Biology, Genetics & Bone Healing

Which of the following bone morphogenetic proteins (BMPs) is an FDA-approved osteoinductive agent specifically indicated as an adjunct for the treatment of acute, open tibial shaft fractures stabilized with an intramedullary nail?

. BMP-2
. BMP-3
. BMP-4
. BMP-7
. BMP-9

Correct Answer & Explanation

. BMP-2

Explanation

Recombinant human BMP-2 (rhBMP-2) is FDA-approved for acute, open tibial shaft fractures treated with an intramedullary nail. BMP-7 (rhBMP-7/OP-1) was previously approved under a humanitarian device exemption for recalcitrant tibial nonunions.

Question 6585

Topic: 1. General Principles & Basic Science

In normal hyaline articular cartilage, which of the following best describes the structural and biochemical characteristics of the deep zone?

. Highest water content and collagen fibers parallel to the joint surface
. Lowest proteoglycan content and random collagen fiber orientation
. Highest proteoglycan content and collagen fibers perpendicular to the joint surface
. Contains the highest density of chondrocytes with high metabolic activity
. Primarily composed of Type X collagen and devoid of proteoglycans

Correct Answer & Explanation

. Highest water content and collagen fibers parallel to the joint surface

Explanation

The deep zone of articular cartilage contains the highest concentration of proteoglycans and the lowest water content. Its collagen fibers (primarily Type II) are oriented perpendicular to the joint surface to effectively resist compressive loads.

Question 6586

Topic: Biomechanics & Biomaterials

In the biomechanical evaluation of orthopedic implant materials, the total area under the stress-strain curve represents which of the following material properties?

. Stiffness
. Yield strength
. Ductility
. Toughness
. Ultimate tensile strength

Correct Answer & Explanation

. Stiffness

Explanation

The total area under the stress-strain curve represents the toughness of a material, which is the total amount of energy it can absorb before mechanical failure. Stiffness, in contrast, is represented by the slope of the linear elastic region.

Question 6587

Topic: Biology, Genetics & Bone Healing

Primary bone healing (contact healing) achieved through rigid internal fixation with absolute stability is characterized primarily by which of the following microscopic processes?

. Endochondral ossification
. Intramembranous ossification
. Formation of a fibrocartilaginous callus
. Osteoclastic cutting cones crossing the fracture site
. Woven bone deposition by invading periosteal cells

Correct Answer & Explanation

. Endochondral ossification

Explanation

Primary bone healing occurs without callus formation under conditions of absolute stability and intimate bone contact. It is driven by Haversian remodeling, where osteoclastic cutting cones cross the fracture site followed directly by osteoblastic bone deposition.

Question 6588

Topic: Biomechanics & Biomaterials

During surgical lengthening of a contracted Achilles tendon, the surgeon applies a constant tension to the tendon over several minutes, noting that it progressively stretches. This viscoelastic property is best defined as:

. Hysteresis
. Creep
. Stress relaxation
. Fatigue
. Anisotropy

Correct Answer & Explanation

. Hysteresis

Explanation

Creep is a viscoelastic property where a tissue progressively deforms (stretches) under a constant load over time. In contrast, stress relaxation occurs when the force required to maintain a constant deformation decreases over time.

Question 6589

Topic: Biology, Genetics & Bone Healing

During bone transport using the Ilizarov method (distraction osteogenesis), the new bone formed in the distraction gap is generated primarily through which of the following processes?

. Primary cortical healing
. Endochondral ossification
. Intramembranous ossification
. Appositional chondrogenesis
. Metaphyseal remodeling

Correct Answer & Explanation

. Primary cortical healing

Explanation

The newly formed bone in the gap during distraction osteogenesis forms primarily via intramembranous ossification under continuous tension. This process successfully bypasses a cartilaginous intermediate phase when stable distraction rates are maintained.

Question 6590

Topic: Biomechanics & Biomaterials

A surgeon considers using a titanium alloy screw to secure a stainless steel plate for a fracture. This combination is generally avoided due to the risk of accelerated degradation of the stainless steel. What is the primary mechanism of this degradation?

. Fretting corrosion
. Crevice corrosion
. Galvanic corrosion
. Pitting corrosion
. Stress corrosion cracking

Correct Answer & Explanation

. Fretting corrosion

Explanation

Galvanic corrosion occurs when two dissimilar metals are placed in physical contact within a conductive fluid environment. The less noble metal (stainless steel) acts as an anode and undergoes accelerated electrochemical corrosion when paired with titanium.

Question 6591

Topic: 1. General Principles & Basic Science

Which of the following mechanisms is predominantly responsible for the boundary lubrication of articular cartilage under conditions of high physiological loading and low sliding speeds?

. Squeeze-film lubrication
. Elastohydrodynamic lubrication
. Secretion of lubricin (PRG4) by superficial zone chondrocytes
. Hydrostatic pressurization of interstitial fluid
. Hyaluronan mediated hydrodynamic levitation

Correct Answer & Explanation

. Squeeze-film lubrication

Explanation

Boundary lubrication operates under high loads and low speeds to prevent direct surface-to-surface wear. It is primarily mediated by lubricin (Proteoglycan 4), a highly specialized glycoprotein secreted by superficial zone chondrocytes and synoviocytes.

Question 6592

Topic: Biology, Genetics & Bone Healing

During bone resorption, osteoclasts utilize a specific enzyme to degrade the organic collagenous matrix of bone within the acidic environment of the sealing zone. Which of the following is the primary enzyme responsible for this process?

. Carbonic anhydrase II
. Alkaline phosphatase
. Cathepsin K
. Matrix metalloproteinase-13 (MMP-13)
. Tartrate-resistant acid phosphatase (TRAP)

Correct Answer & Explanation

. Carbonic anhydrase II

Explanation

Cathepsin K is a highly specialized lysosomal cysteine protease secreted by osteoclasts that degrades Type I collagen in the acidic environment of the resorption pit. Carbonic anhydrase II generates the protons needed to acidify the environment, but does not degrade collagen directly.

Question 6593

Topic: Biology, Genetics & Bone Healing

A patient who underwent external beam radiation therapy for a soft tissue sarcoma subsequently sustains a pathologic fracture of the irradiated femur. Which of the following best characterizes the cellular environment impairing fracture healing in this patient?

. Hyperemia with excessive osteoclastic activity
. Depletion of local osteoblast progenitors and endarteritis obliterans
. Overproduction of transforming growth factor-beta (TGF-b) leading to hypertrophic nonunion
. Unregulated intramembranous ossification without cartilaginous intermediate
. Excessive release of vascular endothelial growth factor (VEGF)

Correct Answer & Explanation

. Hyperemia with excessive osteoclastic activity

Explanation

Radiation therapy impairs bone healing primarily through a profound decrease in local cellularity, depletion of osteogenic progenitor cells, and microvascular thrombosis (endarteritis obliterans). This ischemic and hypocellular environment typically results in an atrophic nonunion.

Question 6594

Topic: 1. General Principles & Basic Science

In the extracellular matrix of articular cartilage, aggrecan monomers form large supramolecular aggregates by non-covalently binding to which of the following backbones?

. Type II collagen
. Fibronectin
. Hyaluronic acid (Hyaluronan)
. Chondroitin sulfate
. Link protein

Correct Answer & Explanation

. Type II collagen

Explanation

Aggrecan monomers, consisting of a core protein with chondroitin and keratan sulfate side chains, bind to a central hyaluronic acid backbone. This critical interaction is stabilized by link proteins, creating large aggregates that entrap water for compressive resilience.

Question 6595

Topic: 1. General Principles & Basic Science

Which of the following design modifications will most effectively increase the pullout strength of an orthopedic cortical screw placed into diaphyseal bone?

. Increasing the inner (core) diameter
. Decreasing the outer (thread) diameter
. Increasing the pitch (distance between threads)
. Increasing the length of thread engagement
. Changing the head design from hexagonal to star-shaped

Correct Answer & Explanation

. Increasing the inner (core) diameter

Explanation

Screw pullout strength is directly proportional to the outer diameter of the thread, the length of thread engagement in bone, and the shear strength of the bone itself. Decreasing thread pitch (more threads per inch) also increases pullout strength.

Question 6596

Topic: 1. General Principles & Basic Science

The administration of nonsteroidal anti-inflammatory drugs (NSAIDs) during the acute phase of fracture healing has been shown in animal models to delay union. This effect is primarily mediated through the inhibition of which of the following?

. Cyclooxygenase-2 (COX-2) dependent prostaglandin E2 (PGE2) synthesis
. Interleukin-1 (IL-1) mediated macrophage activation
. Bone morphogenetic protein-2 (BMP-2) transcription
. Tumor necrosis factor-alpha (TNF-a) receptor binding
. Matrix metalloproteinase (MMP) secretion

Correct Answer & Explanation

. Cyclooxygenase-2 (COX-2) dependent prostaglandin E2 (PGE2) synthesis

Explanation

NSAIDs delay fracture healing by inhibiting COX-2, an enzyme critical for the synthesis of prostaglandins like PGE2. PGE2 is essential for early local inflammatory signaling, angiogenesis, and subsequent osteoblastic differentiation during endochondral ossification.

Question 6597

Topic: Biomechanics & Biomaterials

When a constant deformation is applied to a viscoelastic material such as a ligament, the force required to maintain that deformation decreases over time. This phenomenon is known as:

. Creep
. Stress relaxation
. Hysteresis
. Fatigue failure
. Isotropy

Correct Answer & Explanation

. Creep

Explanation

Stress relaxation is the decrease in stress over time when a viscoelastic material is held at a constant strain. Creep is the progressive deformation over time under a constant load.

Question 6598

Topic: Biology, Genetics & Bone Healing

A 68-year-old woman is treated with a monoclonal antibody for severe osteoporosis. The drug binds to a specific receptor on osteoblast lineage cells to inhibit osteoclastogenesis. What is the molecular target of this medication?

. Sclerostin
. Receptor activator of nuclear factor kappa-B ligand (RANKL)
. Cathepsin K
. Osteoprotegerin (OPG)
. Macrophage colony-stimulating factor (M-CSF)

Correct Answer & Explanation

. Sclerostin

Explanation

Denosumab is a monoclonal antibody that binds to RANKL, preventing it from interacting with RANK on osteoclasts. This mimics the action of OPG, thereby inhibiting osteoclast maturation and survival.

Question 6599

Topic: 1. General Principles & Basic Science

In normal articular cartilage, which of the following best describes the structural arrangement of collagen fibers in the superficial zone?

. Perpendicular to the joint surface
. Randomly oriented
. Parallel to the joint surface
. Oblique to the joint surface
. Arranged in a radial pattern

Correct Answer & Explanation

. Perpendicular to the joint surface

Explanation

In the superficial zone of articular cartilage, collagen fibers are oriented parallel to the joint surface to resist shear forces. In the deep zone, they are oriented perpendicularly to resist compressive loads.

Question 6600

Topic: Biology, Genetics & Bone Healing

A 4-year-old child presents with bowing of the lower extremities and widening of the physes. Laboratory studies reveal hypocalcemia, hypophosphatemia, and markedly elevated alkaline phosphatase. A defect in which of the following processes is most likely responsible?

. Type I collagen synthesis
. Osteoclast ruffled border formation
. Mineralization of osteoid
. Fibroblast growth factor 23 (FGF23) production
. Carbonic anhydrase II function

Correct Answer & Explanation

. Type I collagen synthesis

Explanation

The clinical and laboratory findings are consistent with rickets, which is characterized by defective mineralization of osteoid and cartilage matrix at the growth plate. This is most commonly due to Vitamin D deficiency.

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