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1. General Principles & Basic Science MCQs

Practice Set 339 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 6761

Topic: 1. General Principles & Basic Science

In human diarthrodial joints, articular cartilage utilizes several lubrication mechanisms. Under conditions of high load and very low speed (or at rest), which mechanism predominantly protects the articular surfaces?

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

Correct Answer & Explanation

. Elastohydrodynamic lubrication

Explanation

Boundary lubrication predominates under high-load, low-speed conditions where fluid films break down. It relies on a monomolecular layer of surface-active glycoproteins, primarily lubricin, bound to the articular surface.

Question 6762

Topic: 1. General Principles & Basic Science

Which of the following best describes the process of creeping substitution in cortical bone grafts?

. Direct differentiation of mesenchymal stem cells into osteoblasts
. Initial osteoclastic resorption followed by osteoblastic bone formation
. Simultaneous woven bone formation and resorption
. Chondrogenesis followed by endochondral ossification
. Appositional bone growth without resorption

Correct Answer & Explanation

. Direct differentiation of mesenchymal stem cells into osteoblasts

Explanation

Creeping substitution in cortical bone grafts involves initial osteoclastic resorption of the graft bone, followed by osteoblastic new bone formation along the resorbed surfaces.

Question 6763

Topic: Biomechanics & Biomaterials

A tendon undergoes continuous deformation over time when subjected to a constant physiological load. This viscoelastic property is termed:

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

Correct Answer & Explanation

. Stress relaxation

Explanation

Creep is the time-dependent deformation of a viscoelastic material under a constant load. Stress relaxation, conversely, is a decrease in stress over time under constant deformation.

Question 6764

Topic: 1. General Principles & Basic Science

In which zone of articular cartilage are the collagen fibers oriented primarily parallel to the joint surface?

. Superficial (tangential) zone
. Middle (transitional) zone
. Deep (radial) zone
. Calcified zone
. Subchondral bone plate

Correct Answer & Explanation

. Superficial (tangential) zone

Explanation

The superficial (tangential) zone of articular cartilage contains collagen fibers oriented parallel to the joint surface to resist shear forces.

Question 6765

Topic: Biology, Genetics & Bone Healing

Absolute stability with interfragmentary compression of a fracture leads to primary bone healing. Which of the following is the primary cellular mechanism responsible for this type of healing?

. Endochondral ossification
. Intramembranous ossification
. Cutting cone formation
. Callus formation
. Chondrocyte hypertrophy

Correct Answer & Explanation

. Endochondral ossification

Explanation

Primary bone healing occurs via cutting cones (Haversian remodeling) directly across the fracture site under conditions of absolute stability, bypassing callus formation.

Question 6766

Topic: Biomechanics & Biomaterials

The torsional rigidity of a solid intramedullary nail is proportional to its radius raised to which power?

. First power
. Second power
. Third power
. Fourth power
. Fifth power

Correct Answer & Explanation

. First power

Explanation

Torsional rigidity of a solid cylinder is determined by its polar moment of inertia, which is proportional to the radius to the fourth power (r^4).

Question 6767

Topic: 1. General Principles & Basic Science

During peripheral nerve repair, the epineurial suture technique primarily coapts which structure?

. Endoneurium
. Perineurium
. Epineurium
. Fascicles
. Schwann cell basement membrane

Correct Answer & Explanation

. Endoneurium

Explanation

Epineurial repair approximates the outermost layer of the nerve, the epineurium, which mechanically encloses the entire nerve consisting of multiple fascicles.

Question 6768

Topic: 1. General Principles & Basic Science

Squeeze-film lubrication in human synovial joints is most effective during which type of activity?

. High-load, low-velocity activities
. Low-load, high-velocity activities
. Constant tangential sliding
. Swinging phase of gait
. Unloaded joint motion

Correct Answer & Explanation

. High-load, low-velocity activities

Explanation

Squeeze-film lubrication occurs when joint surfaces are pressed together under high loads and low velocities, utilizing fluid viscosity to prevent direct cartilage-to-cartilage contact.

Question 6769

Topic: Physiology & Rehabilitation

Which type of muscle contraction generates the highest maximum tension?

. Concentric isotonic
. Eccentric
. Isometric
. Isokinetic
. Plyometric

Correct Answer & Explanation

. Concentric isotonic

Explanation

Eccentric contractions, where the muscle lengthens under tension, can generate greater maximal force than isometric or concentric contractions.

Question 6770

Topic: 1. General Principles & Basic Science

Which of the following parameter changes will most significantly increase the pullout strength of a cortical bone screw?

. Decreasing the outer (major) diameter
. Increasing the inner (minor) diameter
. Increasing the thread pitch
. Increasing the outer (major) diameter
. Decreasing the length of engagement

Correct Answer & Explanation

. Decreasing the outer (major) diameter

Explanation

Pullout strength is most significantly increased by increasing the outer (major) diameter of the screw. Increasing the length of engagement in bone also substantially improves pullout strength.

Question 6771

Topic: Biomechanics & Biomaterials

Galvanic corrosion is most likely to occur under which of the following conditions in orthopedic implants?

. A titanium plate is used with titanium screws
. A stainless steel screw is placed in contact with a titanium plate
. A fretting interface exists between a screw head and plate hole of the same material
. An implant is subjected to highly repetitive cyclic loading
. There is a lack of oxygen at the fracture site

Correct Answer & Explanation

. A titanium plate is used with titanium screws

Explanation

Galvanic corrosion occurs when two dissimilar metals (e.g., stainless steel and titanium) are in physical contact within a conductive fluid environment like human body fluid.

Question 6772

Topic: Biomechanics & Biomaterials

In total joint arthroplasty, the phenomenon of "third-body wear" is best classified as which type of wear mechanism?

. Adhesive wear
. Abrasive wear
. Fatigue wear
. Corrosive wear
. Fretting wear

Correct Answer & Explanation

. Adhesive wear

Explanation

Third-body wear is a form of abrasive wear caused by hard particles (like bone, cement, or metal debris) caught between the articulating surfaces, which scratch and gouge the softer material.

Question 6773

Topic: Biology, Genetics & Bone Healing

Which cytokine is considered most critical for the initiation of the inflammatory phase of fracture healing?

. Interleukin-1 (IL-1)
. Bone morphogenetic protein-2 (BMP-2)
. Transforming growth factor-beta (TGF-beta)
. Platelet-derived growth factor (PDGF)
. Vascular endothelial growth factor (VEGF)

Correct Answer & Explanation

. Interleukin-1 (IL-1)

Explanation

Interleukin-1 (IL-1), IL-6, and TNF-alpha are key proinflammatory cytokines that act early to initiate the fracture healing cascade following injury.

Question 6774

Topic: Biology, Genetics & Bone Healing

The Hueter-Volkmann principle describes which of the following phenomena in bone mechanics?

. Bone remodels internally in response to mechanical stress
. Compression forces inhibit physeal growth while tension stimulates it
. Piezoelectric charges dictate osteoblast and osteoclast activity
. The convex side of a curved bone generates electronegative charges
. Endochondral ossification requires absolute structural stability

Correct Answer & Explanation

. Bone remodels internally in response to mechanical stress

Explanation

The Hueter-Volkmann principle states that increased compressive forces parallel to the axis of a physis inhibit longitudinal growth, whereas decreased compressive forces or tension stimulate it.

Question 6775

Topic: 1. General Principles & Basic Science

The most abundant proteoglycan in articular cartilage, responsible for its compressive stiffness through osmotic swelling pressure, is:

. Decorin
. Biglycan
. Aggrecan
. Fibromodulin
. Hyaluronan

Correct Answer & Explanation

. Decorin

Explanation

Aggrecan is the primary proteoglycan in articular cartilage. Its highly negatively charged glycosaminoglycan chains attract water, creating a swelling pressure that resists mechanical compression.

Question 6776

Topic: Biomechanics & Biomaterials

Which of the following biomechanical terms best describes the phenomenon where a ligament subjected to a constant, sustained load exhibits a progressive increase in deformation over time?

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

Correct Answer & Explanation

. Stress relaxation

Explanation

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

Question 6777

Topic: Biology, Genetics & Bone Healing

In the standard Ilizarov technique of distraction osteogenesis, new bone formation across the distraction gap primarily occurs through which of the following biological processes?

. Endochondral ossification
. Intramembranous ossification
. Appositional ossification
. Creeping substitution
. Haversian remodeling

Correct Answer & Explanation

. Endochondral ossification

Explanation

Distraction osteogenesis heals primarily via intramembranous ossification under stable fixation. A cartilaginous intermediate (endochondral ossification) is generally absent unless there is excessive micromotion or instability.

Question 6778

Topic: 1. General Principles & Basic Science

Which of the following geometric modifications to an orthopedic screw will most effectively increase its pullout strength in cortical bone?

. Increasing the minor (core) diameter
. Decreasing the thread depth
. Increasing the major (outer) diameter
. Increasing the thread pitch
. Decreasing the thread length

Correct Answer & Explanation

. Increasing the minor (core) diameter

Explanation

Pullout strength is most heavily dependent on the major (outer) diameter of the screw, increasing proportionally to the square of the outer diameter. Decreasing the pitch or increasing the length of engagement also increases pullout strength, but increasing the major diameter has the most profound effect.

Question 6779

Topic: Biomechanics & Biomaterials

On a standard stress-strain curve for a given orthopaedic implant, the total area under the curve prior to the point of structural failure represents the material's:

. Stiffness
. Toughness
. Ductility
. Yield strength
. Fatigue limit

Correct Answer & Explanation

. Stiffness

Explanation

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

Question 6780

Topic: 1. General Principles & Basic Science

Compared to a parallel-fibered muscle of the same overall mass and volume, a multipennate muscle architecture is characterized biomechanically by which of the following?

. Increased maximal excursion and decreased force production
. Decreased maximal excursion and increased force production
. Increased maximal excursion and increased force production
. Decreased maximal excursion and decreased force production
. Equal excursion and force production

Correct Answer & Explanation

. Increased maximal excursion and decreased force production

Explanation

Pennate muscles have shorter muscle fibers arranged at an angle to the axis of force generation, increasing the physiological cross-sectional area. This architecture generates greater force but allows for less overall excursion compared to parallel-fibered muscles.

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