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1. General Principles & Basic Science MCQs

Practice Set 716 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 14301

Topic: 1. General Principles & Basic Science

In normal adult articular cartilage, which zone contains the highest concentration of collagen, the lowest concentration of proteoglycans, and chondrocytes aligned parallel to the joint surface?

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

Correct Answer & Explanation

. Superficial (tangential) zone

Explanation

The superficial zone primarily resists shear stress and is characterized by collagen fibers and chondrocytes aligned parallel to the articular surface. It possesses the highest water and collagen content but the lowest proteoglycan content.

Question 14302

Topic: Biology, Genetics & Bone Healing

A 50-year-old patient receives a demineralized bone matrix (DBM) allograft for a diaphyseal nonunion. The primary mechanism by which DBM aids in fracture healing is mediated by which of the following processes?

. Osteogenesis
. Osteoinduction
. Osteoconduction
. Contact healing
. Gap healing

Correct Answer & Explanation

. Osteoinduction

Explanation

DBM primarily functions through osteoinduction, acting via bone morphogenetic proteins (BMPs) contained within the matrix. These proteins stimulate local mesenchymal stem cells to differentiate into bone-forming osteoblasts.

Question 14303

Topic: 1. General Principles & Basic Science
What type of collagen is the predominant structural component of the annulus fibrosus of the intervertebral disc?
. Type I
. Type II
. Type III
. Type IX
. Type X

Correct Answer & Explanation

. Type I

Explanation

The annulus fibrosus is subjected to high tensile stresses and is composed predominantly of Type I collagen. In contrast, the inner nucleus pulposus is rich in Type II collagen to resist compressive forces.

Question 14304

Topic: Biomechanics & Biomaterials

When a viscoelastic material like a tendon is subjected to a constant deformation (strain) over time, the force required to maintain that deformation gradually decreases. What is this biomechanical phenomenon called?

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

Correct Answer & Explanation

. Stress relaxation

Explanation

Stress relaxation occurs when a viscoelastic material is held at a constant length, leading to a gradual decrease in the internal stress (force) over time. Creep, conversely, is the continuous deformation of a material under a constant load.

Question 14305

Topic: Biology, Genetics & Bone Healing

Which of the following best describes the molecular mechanism of action of Teriparatide in the treatment of osteoporosis?

. Inhibits the RANK-RANKL interaction to prevent osteoclastogenesis
. Binds selectively to hydroxyapatite and induces osteoclast apoptosis
. Acts as a recombinant parathyroid hormone to stimulate osteoblast activity
. Modulates estrogen receptors to decrease bone resorption
. Inhibits sclerostin to enhance Wnt signaling pathways

Correct Answer & Explanation

. Acts as a recombinant parathyroid hormone to stimulate osteoblast activity

Explanation

Teriparatide is a recombinant human parathyroid hormone (PTH 1-34) analog. When administered in intermittent, low doses, it exhibits a strong anabolic effect by preferentially stimulating osteoblast activity over osteoclast activity.

Question 14306

Topic: Biomechanics & Biomaterials

Galvanic corrosion in orthopedic implants occurs when dissimilar metals are placed in contact within a conductive fluid environment. Which combination of metals is generally considered the most susceptible to this type of severe corrosion?

. Titanium and titanium alloy
. Stainless steel and cobalt-chromium
. Cobalt-chromium and cobalt-chromium alloy
. Titanium and porous tantalum
. Zirconium and titanium

Correct Answer & Explanation

. Stainless steel and cobalt-chromium

Explanation

Galvanic corrosion is driven by the difference in electropotential between two dissimilar metals in an electrolyte solution. Mixing stainless steel with cobalt-chromium creates a high potential difference and a significant risk for clinically relevant galvanic corrosion.

Question 14307

Topic: Physiology & Rehabilitation

A muscle contraction in which the muscle generates tension while actively lengthening is defined as which of the following?

. Concentric
. Eccentric
. Isometric
. Isokinetic
. Isotonic

Correct Answer & Explanation

. Eccentric

Explanation

An eccentric contraction occurs when a muscle lengthens while generating force, often acting to decelerate a joint. This specific type of contraction generates the highest maximum force compared to isometric or concentric contractions.

Question 14308

Topic: 1. General Principles & Basic Science

Articular cartilage acquires its primary compressive stiffness from the interaction between water and which of the following extracellular matrix components?

. Type II collagen fibers
. Fibronectin
. Aggrecan
. Hyaluronan alone
. Chondrocalcin

Correct Answer & Explanation

. Aggrecan

Explanation

Aggrecan is the primary large proteoglycan in articular cartilage and is highly negatively charged. This negative charge repels other molecules and attracts water (Donnan osmotic effect), creating a swelling pressure that provides exceptional compressive stiffness.

Question 14309

Topic: Biology, Genetics & Bone Healing

A 4-year-old child presents with bowing of the long bones, widening of the physes, and cupping of the metaphyses on X-ray. Laboratory studies show hypophosphatemia, elevated alkaline phosphatase, and normal serum calcium. What is the most likely diagnosis?

. Osteogenesis imperfecta
. Achondroplasia
. X-linked hypophosphatemic rickets
. Scurvy
. Renal osteodystrophy

Correct Answer & Explanation

. X-linked hypophosphatemic rickets

Explanation

X-linked hypophosphatemic rickets (due to a PHEX gene mutation) leads to isolated renal phosphate wasting. Classic radiographic signs include widened physes and metaphyseal cupping, accompanied by hypophosphatemia and strictly normal serum calcium levels.

Question 14310

Topic: Biomechanics & Biomaterials

Bone behaves as a viscoelastic material. Because of this property, how does an intact long bone respond to a rapidly applied, high-strain-rate load compared to a slowly applied load?

. It becomes more elastic and absorbs less energy
. It becomes stiffer and can absorb more energy before failure
. Its ultimate tensile strength decreases significantly
. It demonstrates increased creep properties
. Its modulus of elasticity completely degrades

Correct Answer & Explanation

. It becomes stiffer and can absorb more energy before failure

Explanation

Due to the viscoelastic nature of bone, it exhibits strain-rate dependency. At higher rates of loading, bone becomes significantly stiffer and stronger, allowing it to absorb more energy before fracturing compared to lower loading rates.

Question 14311

Topic: Biology, Genetics & Bone Healing

During the intracellular synthesis of collagen, which vitamin is required as an essential cofactor for the hydroxylation of proline and lysine residues?

. Vitamin A
. Vitamin B12
. Vitamin C
. Vitamin D
. Vitamin E

Correct Answer & Explanation

. Vitamin C

Explanation

Vitamin C (ascorbic acid) is an essential cofactor for the enzymes prolyl hydroxylase and lysyl hydroxylase. Deficiency results in scurvy, characterized by defective collagen triple-helix formation and structural tissue weakness.

Question 14312

Topic: Physiology & Rehabilitation

Which type of joint lubrication is most heavily relied upon by human articular joints during the stance phase of normal walking, when loads are highest and sliding speeds are relatively low?

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

Correct Answer & Explanation

. Boundary lubrication

Explanation

Boundary lubrication is the primary mechanism under high loads and low speeds, depending on molecules like lubricin attached to the articular surfaces to prevent direct cartilage-to-cartilage contact. Fluid-film (elastohydrodynamic) lubrication dominates at higher sliding speeds.

Question 14313

Topic: 1. General Principles & Basic Science

What is the principal mechanism by which Non-Steroidal Anti-Inflammatory Drugs (NSAIDs) are theorized to impair fracture healing?

. Inhibition of osteoclast differentiation and action
. Inhibition of COX-2 mediated prostaglandin synthesis
. Direct cellular toxicity to mesenchymal stem cells
. Downregulation of bone morphogenetic protein 2 (BMP-2)
. Impairment of angiogenesis via VEGF suppression

Correct Answer & Explanation

. Inhibition of COX-2 mediated prostaglandin synthesis

Explanation

NSAIDs inhibit cyclooxygenase (COX) enzymes, specifically COX-2, which is required for the production of prostaglandins (e.g., PGE2). These prostaglandins are essential for normal early fracture callus formation and osteoblastogenesis.

Question 14314

Topic: Biomechanics & Biomaterials

When evaluating the viscoelastic properties of ligaments and tendons, which of the following best describes the biomechanical phenomenon of 'creep'?

. Constant deformation of a material under a varying cyclical load
. Progressive and increasing deformation of a material over time under a constant load
. A steady decrease in internal stress over time while maintained at a constant deformation
. Complete and immediate recovery of the original length after load removal
. Increased material stiffness associated with a rapid loading rate

Correct Answer & Explanation

. Progressive and increasing deformation of a material over time under a constant load

Explanation

Creep is defined as the progressive deformation of a viscoelastic material over time when it is subjected to a constant load. Stress relaxation, conversely, is the decrease in stress over time when the material is held at a constant length or deformation.

Question 14315

Topic: Biomechanics & Biomaterials

Titanium alloys are frequently selected for orthopedic implants due to their biocompatibility. Compared to stainless steel alloys, titanium is characterized by which of the following mechanical properties?

. Higher modulus of elasticity
. Higher ultimate tensile strength
. Lower modulus of elasticity
. Increased susceptibility to galvanic corrosion
. Greater resistance to fatigue failure from fretting

Correct Answer & Explanation

. Lower modulus of elasticity

Explanation

Titanium alloys possess a significantly lower modulus of elasticity than stainless steel or cobalt-chrome, making them biomechanically closer to the modulus of cortical bone. This property reduces stress shielding but renders the implant more flexible.

Question 14316

Topic: Biology, Genetics & Bone Healing

A 4-year-old child presents with diffuse bone pain, gingival bleeding, and metaphyseal radiolucent bands on radiographs. The underlying molecular defect involves a failure in which of the following critical intracellular processes?

. Cross-linking of elastin monomers
. Hydroxylation of proline and lysine residues
. Cleavage of type I procollagen
. Gamma-carboxylation of glutamic acid
. Defective mineralization of osteoid

Correct Answer & Explanation

. Hydroxylation of proline and lysine residues

Explanation

The clinical presentation is consistent with scurvy resulting from Vitamin C deficiency. Vitamin C acts as a necessary cofactor for the hydroxylation of proline and lysine residues, which is an essential step in stabilizing the collagen triple helix.

Question 14317

Topic: Physiology & Rehabilitation

Skeletal muscle fibers are differentiated based on their functional and metabolic capabilities. Which of the following characteristics accurately describes Type I skeletal muscle fibers?

. They rely primarily on anaerobic glycolysis for energy production
. They fatigue rapidly during sustained physical activity
. They have a high density of mitochondria and myoglobin
. They are recruited primarily during explosive, high-power movements
. They exhibit a fast-twitch mechanical response

Correct Answer & Explanation

. They have a high density of mitochondria and myoglobin

Explanation

Type I muscle fibers are slow-twitch, oxidative fibers uniquely adapted for endurance and sustained postural control. They possess a high density of mitochondria, myoglobin, and capillaries, allowing them to rely on aerobic metabolism and strongly resist fatigue.

Question 14318

Topic: Biology, Genetics & Bone Healing

Bone morphogenetic proteins (BMPs) play a crucial role in osteoinduction during fracture healing. They initiate intracellular signaling primarily by binding to transmembrane receptors and activating which of the following downstream pathways?

. Wnt/beta-catenin pathway
. JAK/STAT pathway
. cAMP/PKA pathway
. Smad pathway
. RANK/RANKL pathway

Correct Answer & Explanation

. Smad pathway

Explanation

BMPs are members of the transforming growth factor-beta (TGF-beta) superfamily of signaling molecules. Upon binding to specific serine/threonine kinase receptors on the cell surface, they propagate their osteogenic signal primarily via the phosphorylation of intracellular Smad proteins.

Question 14319

Topic: 1. General Principles & Basic Science

A new diagnostic biomarker for periprosthetic joint infection is being evaluated in different hospital populations. If the prevalence of the infection in the tested population increases, which of the following statistical parameters will correspondingly increase?

. Sensitivity
. Specificity
. Positive predictive value
. Negative predictive value
. Likelihood ratio

Correct Answer & Explanation

. Positive predictive value

Explanation

The positive predictive value (PPV) is heavily dependent on the prevalence of the disease within the tested population. As disease prevalence increases, a positive test is more likely to represent a true positive, thereby increasing the PPV.

Question 14320

Topic: 1. General Principles & Basic Science
Tranexamic acid (TXA) is widely utilized in total joint arthroplasty to minimize perioperative blood loss. Which of the following best describes its primary pharmacological mechanism of action?
. Direct and irreversible inhibition of Factor Xa
. Reversible binding to the platelet glycoprotein IIb/IIIa receptor
. Competitive inhibition of plasminogen activation
. Direct activation of circulating antithrombin III
. Enhancement of cross-linking between fibrin monomers

Correct Answer & Explanation

. Competitive inhibition of plasminogen activation

Explanation

Tranexamic acid is a synthetic lysine analog that acts as a potent antifibrinolytic agent. It functions by competitively binding to the lysine receptor sites on plasminogen, which prevents its activation into plasmin and halts the subsequent degradation of fibrin clots.

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