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1. General Principles & Basic Science MCQs

Practice Set 64 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 1261

Topic: Biomechanics & Biomaterials

A 55-year-old active man undergoes a total hip arthroplasty. The surgeon opts for a highly cross-linked polyethylene (HXLPE) liner. Which of the following best describes the mechanical trade-off associated with the increased cross-linking of the polyethylene?

. Increased wear resistance with decreased fatigue strength
. Decreased wear resistance with increased fracture toughness
. Increased oxidation resistance with increased yield strength
. Decreased oxidation resistance with decreased wear resistance
. Increased wear resistance with increased fracture toughness

Correct Answer & Explanation

. Increased wear resistance with decreased fatigue strength

Explanation

Highly cross-linked polyethylene undergoes irradiation to increase wear resistance by forming cross-links between polymer chains. However, this process decreases bulk mechanical properties such as fatigue strength, fracture toughness, and yield strength.

Question 1262

Topic: Biology, Genetics & Bone Healing

During the process of secondary bone healing, which of the following mechanical and biological environments most strongly promotes the differentiation of mesenchymal stem cells into chondrocytes, leading to endochondral ossification?

. Absolute rigid stability with high oxygen tension
. High oxygen tension with low mechanical strain
. Moderate cyclic mechanical strain and low oxygen tension
. Extremely high shear stress and high oxygen tension
. Complete absence of vascularity and strain

Correct Answer & Explanation

. Moderate cyclic mechanical strain and low oxygen tension

Explanation

Secondary bone healing involves callus formation via endochondral ossification. A relatively low oxygen (hypoxic) environment combined with moderate cyclic mechanical strain promotes the differentiation of mesenchymal stem cells into chondrocytes to form a cartilaginous callus.

Question 1263

Topic: 1. General Principles & Basic Science

Which of the following is the proper sequence (or order) of the classes of macromolecules in articular cartilage in regard to the percentage of dry weight of the components (highest to lowest):

. Collagen, proteoglycans, noncollagenous proteins/glycoproteins
. Proteoglycans, collagen, noncollagenous proteins/glycoproteins
. Proteoglycans, noncollagenous proteins/glycoproteins, collagen
. Collagen, noncollagenous proteins/glycoproteins, proteoglycans
. Noncollagenous proteins/glycoproteins, collagen, proteoglycans

Correct Answer & Explanation

. Collagen, proteoglycans, noncollagenous proteins/glycoproteins

Explanation

Articular cartilage has three principal classes of macromolecules: Collagen โ€“ 60% Proteoglycans โ€“ 25% to 35% Noncollagenous proteins/glycoproteins โ€“ 15% to 20%

Question 1264

Topic: 1. General Principles & Basic Science
Which of the following articular cartilage collagens form cross-banded fibrils?
. Types VI and X
. Types I, III, and V
. Types II, IX, and XI
. Types II, VI, and X
. Types II, VI, IX, X, and XI

Correct Answer & Explanation

. Types II, IX, and XI

Explanation

Three articular cartilage collagens that form cross bands are types II, IX, and XI. Of particular note: Type XI binds to type II. Type IX binds to the cross-banded fibrils in the superficial layer. Type VI attaches to the matrix around the chondrocytes. Type X is near the calcified layer and is probably involved in mineralization of the calcified layer.

Question 1265

Topic: 1. General Principles & Basic Science

Which of the following molecules binds with type II collagen and may aid in the stabilization of the type II collagen network in articular cartilage:

. Transforming growth factor beta
. Decorin and fibromodulin
. Biglycan
. Anchorin C II
. C artilage oligomeric protein (C OMP)

Correct Answer & Explanation

. Decorin and fibromodulin

Explanation

Decorin and fibromodulin bind to type II collagen and likely stabilize the type II collagen network. The other responses refer to: Biglycan: Binds with type VI collagen Anchorin C II: Helps attach chondrocytes to the collagen fibrils COMP: Binds to chondrocytes

Question 1266

Topic: 1. General Principles & Basic Science

A high collagen concentration and a low proteoglycan concentration is found in which of the following zones of articular cartilage:

. Superficial zone
. Transitional zone
. Middle (radial or deep) zone
. C alcified cartilage zone
. Tidemark zone

Correct Answer & Explanation

. Superficial zone

Explanation

The superficial zone has a number of important characteristics: Thinnest articular cartilage layer Two layers: Most superficial โ€“ fine collagen fibrils (lamina splendens) Deep layer โ€“ flattened fibroblast-like chondrocytes (parallel to joint surface) Forms a cartilage skin Important chemical properties: High collagen and low proteoglycan concentration Fibronectin and water concentrations are highest in this zone Great tensile stiffness and strength Seals off the cartilage from the immune system

Question 1267

Topic: 1. General Principles & Basic Science

A high concentration of fibronectin and water is found in which of the following articular cartilage zones:

. Superficial zone
. Transitional zone
. Middle (radial or deep) zone
. C alcified cartilage zone
. Tidemark zone

Correct Answer & Explanation

. Superficial zone

Explanation

The superficial zone has a number of important characteristics: Thinnest articular cartilage layer Two layers: Most superficial โ€“ fine collagen fibrils (lamina splendens) Deep layer โ€“ flattened fibroblast-like chondrocytes (parallel to joint surface) Forms a cartilage skin Important chemical properties: High collagen and low proteoglycan concentration Fibronectin and water concentrations are highest in this zone Great tensile stiffness and strength Seals off the cartilage from the immune system

Question 1268

Topic: 1. General Principles & Basic Science

Which of the following zones of the articular cartilage most likely seals the cartilage off from the immune system:

. Superficial zone
. Transitional zone
. Middle (radial or deep) zone
. C alcified zone
. Tidemark zone

Correct Answer & Explanation

. Superficial zone

Explanation

The superficial zone has a number of important characteristics: Thinnest articular cartilage layer Two layers: Most superficial โ€“ fine collagen fibrils (lamina splendens) Deep layer โ€“ flattened fibroblast-like chondrocytes (parallel to joint surface) Forms a cartilage skin Important chemical properties: High collagen and low proteoglycan concentration Fibronectin and water concentrations are highest in this zone Great tensile stiffness and strength Seals off the cartilage from the immune system

Question 1269

Topic: 1. General Principles & Basic Science

Which of the following statements is true concerning the transitional zone of articular cartilage:

. Cells are ellipsoid shaped and parallel to the articular surface.
. The extracellular matrix has a high water and a low proteoglycan content.
. The chondrocytes have a high concentration of organelles such as rough endoplasmic reticulum and Golgi apparatus.
. The extracellular matrix has the largest diameter collagen fibers and the highest concentration of proteoglycans.
. The collagen fibers are perpendicular to the surface and resist shear stresses.

Correct Answer & Explanation

. The chondrocytes have a high concentration of organelles such as rough endoplasmic reticulum and Golgi apparatus.

Explanation

The transitional zone lies between the superficial and middle zones of the articular cartilage. The following important points should be remembered: The chondrocytes have a high concentration of synthetic organelles such as rough endoplasmic reticulum and Golgi apparatus. The collagen fibers are larger than in the superficial zone. The proteoglycan concentration is higher than the superficial zone.

Question 1270

Topic: 1. General Principles & Basic Science

The chondrocytes in which of the following articular cartilage zones have the lowest metabolic activity:

. Superficial zone
. Transitional zone
. Middle (radial or deep) zone
. C alcified cartilage zone
. Tidemark zone

Correct Answer & Explanation

. C alcified cartilage zone

Explanation

The chondrocytes in the calcified cartilage zone show the least metabolic activity. In contrast, the chondrocytes of the other areas are very active: Superficial zone Fine collagen fibrils (lamina splendens) High collagen and low proteoglycan concentration Fibronectin and water concentrations are highest in this zone Transitional zone The chondrocytes have a high concentration of synthetic organelles such as rough endoplasmic reticulum and Golgi apparatus. The collagen fibers are larger than in the superficial zone. The proteoglycan concentration is higher than the superficial zone. Middle (radial or deep) zone Largest diameter collagen fibrils Highest proteoglycan content

Question 1271

Topic: Biology, Genetics & Bone Healing

Which of the following molecules causes the expression of matrix metalloproteinases that can degrade the articular cartilage extracellular matrix:

. Insulin-dependent growth factor I
. Transforming growth factor beta
. Interleukin I
. Bone morphogenetic protein 2
. Bone morphogenetic protein 7

Correct Answer & Explanation

. Interleukin I

Explanation

Interleukin I has the potential to increase expression of matrix metalloproteinases that can dissolve the extracellular matrix. The other responses are anabolic factors: Insulin-dependent growth factor I Transforming growth factor beta Bone morphogenetic protein 2 Bone morphogenetic protein 7

Question 1272

Topic: 1. General Principles & Basic Science

Which of the following resist tensile and shear deformation forces in articular cartilage:

. Biglycan
. Type II collagen fibers
. Glycosaminoglycans
. Anchorin II
. Tidemark

Correct Answer & Explanation

. Type II collagen fibers

Explanation

Type II collagen fibers resist tensile and shear deformation forces in the articular cartilage. In contrast, the glycosaminoglycan aggregates resist articular cartilage compression and fluid flow.

Question 1273

Topic: 1. General Principles & Basic Science

Which of the following resist articular cartilage compression and fluid flow:

. Biglycan
. Type II collagen fibers
. Glycosaminoglycan aggregates
. Anchorin II
. Tidemark

Correct Answer & Explanation

. Glycosaminoglycan aggregates

Explanation

Type II collagen fibers resist tensile and shear deformation forces in the articular cartilage. In contrast, the glycosaminoglycan aggregates resist articular cartilage compression and fluid flow.

Question 1274

Topic: 1. General Principles & Basic Science

Which of the following are characteristic of osteoarthritis:

. Synovial proliferation, cysts/erosions on both sides of the joint
. Synovial proliferation, periarticular osteopenia, symmetric joint space loss
. Asymmetric joint space loss, subchondral sclerosis and cysts, osteophyte formation
. Subluxation, bone fragmentation, dissolution of the articular surfaces
. Periarticular erosions, preservation of the articular surface

Correct Answer & Explanation

. Asymmetric joint space loss, subchondral sclerosis and cysts, osteophyte formation

Explanation

The characteristic findings in osteoarthritis are: Asymmetric loss of the joint space Subchondral sclerosis and cysts Osteophyte formation As the cartilage degenerates, progressive bone remodeling occurs. The other responses refer to other synovial proliferative disorders: Pigmented villonodular synovitis: Synovial proliferation, cysts/erosions on both sides of the joint Rheumatoid arthritis: Synovial proliferation with lymphocytic infiltration, periarticular osteopenia, symmetric joint space loss Charcot neuropathy: Subluxation, bone fragmentation, dissolution of the articular surfaces Gout: Periarticular erosions, soft tissue masses, preservation of the articular surfaces

Question 1275

Topic: 1. General Principles & Basic Science

Which of the following chemical changes occur in the first phase (earliest) of osteoarthritis:

. Constant collagen, decreased proteoglycan, constant water
. Constant collagen, decreased proteoglycan, increased water
. Decreased collagen, decreased proteoglycan, decreased water
. Decreased collagen, decreased proteoglycan, increased water
. Constant collagen, constant proteoglycan, increased water

Correct Answer & Explanation

. Constant collagen, decreased proteoglycan, increased water

Explanation

The cause of osteoarthritis is unknown. From a chemical standpoint, one of the earliest findings is a decrease in the proteoglycan and an increase in the water content. One should remember: Constant type II collagen content Decreased proteoglycan concentration and decreased chain length Increased water content The decreased proteoglycan content results in increased permeability of the cartilage. A reduction of the stiffness makes the articular cartilage less able to bear loads.

Question 1276

Topic: 1. General Principles & Basic Science
Which of the following is characteristic of the second stage of osteoarthritis?
. Reduction in proteoglycan concentration
. Decrease in water content
. Formation of type I collagen
. Chondrocyte proliferation
. Reduction in interleukin I levels

Correct Answer & Explanation

. Reduction in proteoglycan concentration

Explanation

The cause of osteoarthritis is unknown. From a chemical standpoint, one of the earliest findings is a decrease in the proteoglycan and an increase in the water content. One should remember: constant type II collagen content, decreased proteoglycan concentration and decreased chain length, and increased water content. In the second stage, there is a cellular responseโ€”chondrocyte proliferation. Clusters of chondrocytes producing new matrix are visible. In this stage, there is nitric oxide and interleukin I production. These are catabolic factors that increase matrix metalloproteinase activity. Degradative enzymes break down types IX and XI collagen, which may compromise the stability of the type II collagen framework.

Question 1277

Topic: 1. General Principles & Basic Science
Which of the following is characteristic of the second stage of osteoarthritis?
. Increased interleukin I levels
. Decrease in water content
. Formation of type I collagen
. Increased proteoglycan concentration
. Reduced chondrocyte proliferation and synthesis

Correct Answer & Explanation

. Reduced chondrocyte proliferation and synthesis

Explanation

The cause of osteoarthritis is unknown. From a chemical standpoint, one of the earliest findings is a decrease in the proteoglycan and an increase in the water content. One should remember: constant type II collagen content, decreased proteoglycan concentration and decreased chain length, and increased water content. In the second stage, there is a cellular responseโ€”chondrocyte proliferation. Clusters of chondrocytes producing new matrix are visible. In this stage, there is nitric oxide and interleukin I production. These are catabolic factors that increase matrix metalloproteinase activity. Degradative enzymes break down types IX and XI collagen, which may compromise the stability of the type II collagen framework.

Question 1278

Topic: 1. General Principles & Basic Science
Which of the following is characteristic of the second stage of osteoarthritis?
. Decrease in water content
. Decreased proteoglycan synthesis
. Increased nitric oxide production
. Reduced matrix metalloproteinase production
. Production of type I collagen

Correct Answer & Explanation

. Increased nitric oxide production

Explanation

The cause of osteoarthritis is unknown. From a chemical standpoint, one of the earliest findings is a decrease in the proteoglycan and an increase in the water content. One should remember: constant type II collagen content, decreased proteoglycan concentration and decreased chain length, and increased water content. In the second stage, there is a cellular responseโ€”chondrocyte proliferation. Clusters of chondrocytes producing new matrix are visible. In this stage, there is nitric oxide and interleukin I production. These are catabolic factors that increase matrix metalloproteinase activity. Degradative enzymes break down types IX and XI collagen, which may compromise the stability of the type II collagen framework.

Question 1279

Topic: 1. General Principles & Basic Science

Which of the following is characteristic of the third and final stage of osteoarthritis:

. Decreased water content
. Increased proteoglycan content
. Reduced interleukin I levels
. Reduced nitric oxide levels
. Reduced chondrocyte proliferation and function

Correct Answer & Explanation

. Reduced chondrocyte proliferation and function

Explanation

In the last stage of osteoarthritis, there is reduced chondrocyte proliferation and function, which may be secondary to reduced ability to respond to anabolic factors (down regulation). There may be accumulation of molecules that bind to the anabolic factors (and keep the factors from the chondrocytes) such as decorin and insulin-dependent growth factor binding protein.

Question 1280

Topic: 1. General Principles & Basic Science

A patient presents for surgical treatment of a third web space neuroma. She inquires as to the potential for complications from the procedure. You inform her that the recurrence rate following excision is approximately:

. 2%
. 5%
. 15%
. 25%
. 35%

Correct Answer & Explanation

. 15%

Explanation

The reported recurrence rate following excision of a primary interdigital neuroma is approximately 15%. The recurrence rate should always be communicated to the patient preoperatively.

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