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1. General Principles & Basic Science MCQs

Practice Set 598 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 11941

Topic: 1. General Principles & Basic Science

In the ultrastructure of normal articular cartilage, the deepest zone (calcified zone) is separated from the deep (radial) zone by which of the following histological landmarks?

. Tidemark
. Cement line
. Lamina splendens
. Proteoglycan-rich extracellular matrix
. Sharpey's fibers

Correct Answer & Explanation

. Tidemark

Explanation

The tidemark separates the deep (radial) zone of uncalcified articular cartilage from the calcified cartilage zone. The cement line separates the calcified cartilage from the underlying subchondral bone.

Question 11942

Topic: Biomechanics & Biomaterials

When combining a titanium alloy (Ti-6Al-4V) femoral stem with a cobalt-chromium (CoCr) modular head in total hip arthroplasty, the construct is at risk for which specific type of corrosion at the trunnion?

. Crevice corrosion
. Fretting corrosion
. Galvanic corrosion
. Pitting corrosion
. Intergranular corrosion

Correct Answer & Explanation

. Crevice corrosion

Explanation

Galvanic corrosion occurs when two dissimilar metals (like Ti alloy and CoCr) are in contact in an electrolytic solution (body fluid), leading to the preferential corrosion of the less noble metal. Fretting corrosion can also occur concurrently due to micromotion.

Question 11943

Topic: Biomechanics & Biomaterials

A viscoelastic material is subjected to a constant load over a prolonged period. The observation that the material continues to deform progressively over time under this constant load is defined as:

. Stress relaxation
. Creep
. Hysteresis
. Fatigue
. Strain rate dependency

Correct Answer & Explanation

. Stress relaxation

Explanation

Creep is the progressive deformation of a viscoelastic material when subjected to a constant load. Stress relaxation is the decrease in internal stress over time when the material is held at a constant deformation.

Question 11944

Topic: 1. General Principles & Basic Science

Which of the following glycosaminoglycans (GAGs) is the primary non-sulfated backbone to which multiple aggrecan monomers attach to form the large proteoglycan aggregates in articular cartilage?

. Chondroitin sulfate
. Keratan sulfate
. Hyaluronic acid
. Dermatan sulfate
. Heparan sulfate

Correct Answer & Explanation

. Chondroitin sulfate

Explanation

Hyaluronic acid (hyaluronan) is a non-sulfated glycosaminoglycan that serves as the central backbone. Aggrecan monomers attach to it via link proteins to form massive proteoglycan aggregates that provide cartilage with its compressive stiffness.

Question 11945

Topic: 1. General Principles & Basic Science

In a randomized controlled trial comparing two surgical techniques, the researchers fail to find a statistically significant difference between the groups, although a true difference exists in reality. Which of the following statistical concepts describes this outcome?

. Type I error
. Type II error
. Selection bias
. Confounding
. Attrition bias

Correct Answer & Explanation

. Type I error

Explanation

A Type II error occurs when a study fails to reject the null hypothesis when it is actually false (a false negative). The probability of making a Type II error is denoted by beta, and statistical power is defined as 1 minus beta.

Question 11946

Topic: Biology, Genetics & Bone Healing

Recombinant human bone morphogenetic protein-2 (rhBMP-2) is utilized to enhance bone healing. Its intracellular signaling cascade is primarily mediated by which of the following families of proteins?

. Wnt/Beta-catenin
. Smad
. JAK/STAT
. MAPK/ERK
. Notch

Correct Answer & Explanation

. Wnt/Beta-catenin

Explanation

BMPs bind to serine/threonine kinase receptors on the cell surface, which then phosphorylate intracellular Smad proteins (typically Smad 1, 5, and 8). These form a complex with Smad 4 and translocate to the nucleus to regulate target gene transcription.

Question 11947

Topic: Biology, Genetics & Bone Healing

Romosozumab is an anabolic medication used in the treatment of osteoporosis. It exerts its effect by binding to and inhibiting which of the following molecules?

. RANKL
. Cathepsin K
. Sclerostin
. Parathyroid hormone receptor
. Fibroblast growth factor 23 (FGF23)

Correct Answer & Explanation

. RANKL

Explanation

Romosozumab is a monoclonal antibody that binds to and inhibits sclerostin. Sclerostin is naturally produced by osteocytes to inhibit the Wnt/beta-catenin pathway, so inhibiting it leads to increased osteoblastic bone formation.

Question 11948

Topic: Infection, Pharmacology & VTE

During a two-stage exchange arthroplasty for a periprosthetic joint infection caused by methicillin-resistant Staphylococcus aureus, rifampin is often added to the antibiotic regimen due to its biofilm penetration. What is the mechanism of action of rifampin?

. Inhibition of cell wall synthesis
. Binding to the 30S ribosomal subunit
. Binding to the 50S ribosomal subunit
. Inhibition of DNA gyrase
. Inhibition of DNA-dependent RNA polymerase

Correct Answer & Explanation

. Inhibition of cell wall synthesis

Explanation

Rifampin works by binding to and inhibiting bacterial DNA-dependent RNA polymerase, thereby preventing transcription of messenger RNA. It is highly effective against staphylococci residing in biofilms.

Question 11949

Topic: 1. General Principles & Basic Science
Which of the following skeletal muscle fiber types is characterized by a high mitochondrial density, high myoglobin content, and reliance primarily on oxidative phosphorylation for energy?
. Type I
. Type IIa
. Type IIx
. Type IIb
. Type III

Correct Answer & Explanation

. Type I

Explanation

Type I (slow-twitch) muscle fibers are highly oxidative, fatigue-resistant fibers with abundant mitochondria and myoglobin. This makes them appear red and ideal for sustained postural activities.

Question 11950

Topic: Biology, Genetics & Bone Healing

Nitrogen-containing bisphosphonates (e.g., alendronate) inhibit osteoclast function and induce apoptosis by disrupting the mevalonate pathway. Which specific enzyme do they directly inhibit?

. Carbonic anhydrase II
. Cathepsin K
. Farnesyl pyrophosphate synthase
. HMG-CoA reductase
. Tartrate-resistant acid phosphatase

Correct Answer & Explanation

. Carbonic anhydrase II

Explanation

Nitrogen-containing bisphosphonates specifically inhibit farnesyl pyrophosphate (FPP) synthase in the mevalonate pathway. This prevents the prenylation of small GTP-binding proteins essential for osteoclast function and survival.

Question 11951

Topic: Biomechanics & Biomaterials

Titanium alloy (Ti-6Al-4V) is frequently used in orthopedic implants due to its excellent biocompatibility. Compared to 316L stainless steel, titanium alloy is characterized by:

. Higher modulus of elasticity
. Lower modulus of elasticity
. Greater resistance to abrasive wear
. Higher density
. Greater ductility

Correct Answer & Explanation

. Higher modulus of elasticity

Explanation

Titanium alloys have a lower modulus of elasticity (closer to that of cortical bone) compared to stainless steel and cobalt-chromium alloys, reducing stress shielding. However, titanium is highly notch-sensitive and has poor resistance to abrasive wear.

Question 11952

Topic: Biology, Genetics & Bone Healing

A patient presents with bleeding gums, petechiae, and poor wound healing. Radiographs show osteopenia and dense metaphyseal bands. The deficiency causing this condition impairs bone formation by disrupting which specific intracellular process?

. Glycosylation of procollagen
. Hydroxylation of proline and lysine residues
. Cleavage of registration peptides
. Cross-linking of tropocollagen via lysyl oxidase
. Transcription of type I collagen mRNA

Correct Answer & Explanation

. Glycosylation of procollagen

Explanation

Vitamin C (ascorbic acid) is an essential cofactor for prolyl hydroxylase and lysyl hydroxylase. Deficiency (scurvy) prevents the hydroxylation of proline and lysine residues, which is critical for the stable triple-helix formation of collagen.

Question 11953

Topic: Biomechanics & Biomaterials

The myotendinous junction is the most common site of strain injuries in skeletal muscle. Structurally, the cell membrane of the muscle fiber at this junction is highly folded. What is the primary biomechanical advantage of this folding?

. Decreases the modulus of elasticity
. Increases the surface area to reduce applied shear stress
. Facilitates calcium ion transfer during contraction
. Provides a reservoir for satellite cells
. Converts tensile stress into compressive stress

Correct Answer & Explanation

. Decreases the modulus of elasticity

Explanation

The extensive folding of the sarcolemma at the myotendinous junction significantly increases the surface area over which force is transmitted. This effectively decreases the shear stress acting on the interface, reducing the risk of failure.

Question 11954

Topic: 1. General Principles & Basic Science

The principal blood supply to the diaphyseal cortex of a long bone is derived from the nutrient artery. In a normal mature long bone, the blood flow through the diaphyseal cortex is directed in which pattern?

. Centrifugal (endosteal to periosteal)
. Centripetal (periosteal to endosteal)
. Longitudinal only
. Bidirectional simultaneously
. Randomly arborized

Correct Answer & Explanation

. Centrifugal (endosteal to periosteal)

Explanation

In normal mature long bones, the predominant direction of arterial blood flow across the diaphyseal cortex is centrifugal. Blood moves from the high-pressure intramedullary (endosteal) system toward the lower-pressure periosteal system.

Question 11955

Topic: Biomechanics & Biomaterials
In the manufacturing of ultra-high-molecular-weight polyethylene (UHMWPE) for total joint arthroplasty, the polymer is exposed to gamma irradiation followed by a melting or annealing process. What is the primary purpose of this post-irradiation thermal treatment?
. To increase the ultimate tensile strength
. To eliminate free radicals and prevent oxidation
. To decrease the degree of cross-linking
. To lower the modulus of elasticity
. To sterilize the final packaged component

Correct Answer & Explanation

. To eliminate free radicals and prevent oxidation

Explanation

Gamma irradiation induces cross-linking, which dramatically improves wear resistance but also generates free radicals. Post-irradiation thermal treatment (melting or annealing) is performed to quench these free radicals, thereby preventing long-term in vivo oxidation and degradation.

Question 11956

Topic: Biology, Genetics & Bone Healing

Which of the following molecules acts as a soluble decoy receptor to inhibit osteoclastogenesis by preventing the interaction between osteoblasts and osteoclast precursors?

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

Correct Answer & Explanation

. Macrophage colony-stimulating factor (M-CSF)

Explanation

Osteoprotegerin (OPG) is secreted by osteoblasts and acts as a decoy receptor for RANKL. By binding RANKL, OPG prevents it from binding to RANK on osteoclast precursors, thereby inhibiting osteoclast differentiation and bone resorption.

Question 11957

Topic: 1. General Principles & Basic Science

In which histological zone of normal articular cartilage is the water content the highest and the concentration of proteoglycans the lowest?

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

Correct Answer & Explanation

. Superficial (tangential) zone

Explanation

The superficial zone of articular cartilage contains the highest water content and the lowest concentration of proteoglycans. Its collagen fibers are arranged parallel to the joint surface to resist shear forces.

Question 11958

Topic: Biomechanics & Biomaterials

A ligament stretched to a constant length over time will exhibit a gradual decrease in the force required to maintain that specific length. This viscoelastic property is known as:

. Creep
. Stress relaxation
. Hysteresis
. Fatigue failure
. Isotropic behavior

Correct Answer & Explanation

. Creep

Explanation

Stress relaxation is a viscoelastic property where the stress (force) within a material decreases over time when it is held at a constant strain (length). Creep, in contrast, is continued deformation under a constant load.

Question 11959

Topic: Biomechanics & Biomaterials

Compared to stainless steel and cobalt-chromium alloys, titanium alloy (Ti-6Al-4V) used in orthopedic implants is characterized by:

. A higher modulus of elasticity
. Greater notch sensitivity
. Better resistance to abrasive wear
. Increased risk of galvanic corrosion when used alone
. A higher density

Correct Answer & Explanation

. A higher modulus of elasticity

Explanation

Titanium alloy is highly notch sensitive, meaning surface scratches can significantly reduce its fatigue strength. However, it has a lower modulus of elasticity (closer to bone) than stainless steel or cobalt-chromium, reducing stress shielding.

Question 11960

Topic: Biology, Genetics & Bone Healing

Nitrogen-containing bisphosphonates (e.g., alendronate) inhibit osteoclast function primarily by targeting which of the following enzymes in the mevalonate pathway?

. Carbonic anhydrase II
. Cathepsin K
. Farnesyl pyrophosphate synthase
. Tartrate-resistant acid phosphatase
. Matrix metalloproteinase-9

Correct Answer & Explanation

. Carbonic anhydrase II

Explanation

Nitrogen-containing bisphosphonates inhibit farnesyl pyrophosphate synthase in the mevalonate pathway. This prevents the prenylation of small GTPase proteins essential for osteoclast survival and cytoskeletal organization, leading to osteoclast apoptosis.

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