Menu

1. General Principles & Basic Science MCQs

Practice Set 359 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 7161

Topic: Biology, Genetics & Bone Healing

Demineralized bone matrix (DBM) products primarily rely on which of the following components for their osteoinductive properties?

. Mesenchymal stem cells
. Hydroxyapatite scaffolding
. Bone morphogenetic proteins (BMPs)
. Platelet-derived growth factor (PDGF)
. Type I collagen network

Correct Answer & Explanation

. Mesenchymal stem cells

Explanation

Demineralized bone matrix (DBM) is processed by removing the mineral component of bone, which exposes the underlying osteoinductive proteins, primarily Bone Morphogenetic Proteins (BMPs). DBM serves as an osteoconductive and osteoinductive graft but inherently lacks live osteogenic cells.

Question 7162

Topic: 1. General Principles & Basic Science

Which of the following alterations to a cortical screw design most significantly increases its pull-out strength in diaphyseal bone?

. Increasing the inner root diameter
. Increasing the pitch
. Increasing the outer thread diameter
. Decreasing the thread depth
. Decreasing the number of threads per inch

Correct Answer & Explanation

. Increasing the inner root diameter

Explanation

Pullout strength of a screw is most dependent on the outer (major) diameter of the thread. Other factors increasing pullout strength include decreased pitch (more threads per unit length) and increased length of engagement.

Question 7163

Topic: Biology, Genetics & Bone Healing

According to Perrenโ€™s strain theory, what is the maximum interfragmentary strain that can be tolerated for the formation of lamellar bone without an intervening cartilage stage?

. 1%
. 2%
. 10%
. 15%
. 100%

Correct Answer & Explanation

. 1%

Explanation

Primary bone healing occurs without a cartilaginous callus when interfragmentary strain is strictly below 2%. Strain between 2% and 10% allows for secondary healing via endochondral ossification.

Question 7164

Topic: Biomechanics & Biomaterials

A patient undergoes internal fixation with a titanium alloy plate. Compared to stainless steel, titanium alloy exhibits which of the following mechanical properties?

. Higher modulus of elasticity and decreased fatigue strength
. Higher modulus of elasticity and increased fatigue strength
. Lower modulus of elasticity and decreased biocompatibility
. Lower modulus of elasticity and decreased stress shielding
. Lower modulus of elasticity and increased stress shielding

Correct Answer & Explanation

. Higher modulus of elasticity and decreased fatigue strength

Explanation

Titanium alloy has a lower modulus of elasticity compared to stainless steel, bringing it closer to that of cortical bone. This leads to less stress shielding of the underlying bone, preserving bone density.

Question 7165

Topic: 1. General Principles & Basic Science

During the remodeling phase of tendon healing, which of the following biochemical changes predominantly occurs?

. Replacement of Type I collagen with Type II collagen
. Replacement of Type I collagen with Type III collagen
. Replacement of Type III collagen with Type I collagen
. Decreased cross-linking of collagen fibers
. Increased cellularity and angiogenesis

Correct Answer & Explanation

. Replacement of Type I collagen with Type II collagen

Explanation

During the remodeling phase of tendon healing, the initial, structurally weaker Type III collagen is gradually replaced by stronger, highly cross-linked Type I collagen. This process increases the ultimate tensile strength of the tendon.

Question 7166

Topic: Surgical Anatomy & Approaches

During the volar (Henry) approach to the radius, the surgeon dissects between the brachioradialis and the flexor carpi radialis. What is the internervous plane at the proximal portion of this exposure?

. Radial nerve and Median nerve
. Radial nerve and Ulnar nerve
. Median nerve and Musculocutaneous nerve
. Median nerve and Ulnar nerve
. Radial nerve and Musculocutaneous nerve

Correct Answer & Explanation

. Radial nerve and Median nerve

Explanation

The proximal internervous plane for the volar approach to the radius is between the brachioradialis (innervated by the radial nerve) and the pronator teres (innervated by the median nerve).

Question 7167

Topic: Biology, Genetics & Bone Healing

Which of the following terms best describes the process by which a structural cortical allograft is slowly resorbed by osteoclasts and replaced by host osteoblasts?

. Osteoinduction
. Osteoconduction
. Creeping substitution
. Distraction osteogenesis
. Endochondral ossification

Correct Answer & Explanation

. Osteoinduction

Explanation

Creeping substitution is the simultaneous process of bone resorption by host osteoclasts and deposition by host osteoblasts into a graft. Cortical allografts undergo this process slowly, initially losing structural strength before full incorporation.

Question 7168

Topic: Biology, Genetics & Bone Healing

Which bone morphogenetic protein (BMP) is an FDA-approved osteoinductive agent for use in open tibial shaft fractures treated with intramedullary nailing?

. 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 use in acute open tibial shaft fractures treated with an IM nail, as well as anterior lumbar interbody fusion. BMP-7 (OP-1) was previously utilized for recalcitrant tibial nonunions under an HDE.

Question 7169

Topic: Biomechanics & Biomaterials

When a constant load is applied to a viscoelastic material such as a ligament over a prolonged period, the material will undergo a time-dependent increase in length. This phenomenon is known as:

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

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 internal stress over time when the material is held at a constant length.

Question 7170

Topic: Biomechanics & Biomaterials

A surgeon uses a stainless steel screw to secure a titanium plate during fracture fixation. The construct is at high risk for which of the following complications?

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

Correct Answer & Explanation

. Crevice corrosion

Explanation

Galvanic corrosion occurs when two dissimilar metals (e.g., stainless steel and titanium) are placed in contact within a conductive fluid environment like the human body. The less noble metal acts as an anode and undergoes accelerated corrosion.

Question 7171

Topic: 1. General Principles & Basic Science

In which zone of articular cartilage are the collagen fibers oriented perpendicular to the articular surface to provide the greatest resistance to compressive forces?

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

Correct Answer & Explanation

. Superficial (tangential) zone

Explanation

In the deep (radial) zone of articular cartilage, collagen fibers are oriented perpendicularly to the articular surface and cross into the tidemark. This structural orientation provides the primary resistance to compressive loads.

Question 7172

Topic: Biology, Genetics & Bone Healing

Activation of the Wnt/beta-catenin signaling pathway in osteoblasts primarily results in which of the following effects?

. Increased bone resorption via RANKL expression
. Inhibition of osteoblast differentiation
. Increased bone formation and osteoblast survival
. Differentiation of mesenchymal stem cells into chondrocytes
. Apoptosis of osteocytes

Correct Answer & Explanation

. Increased bone resorption via RANKL expression

Explanation

The Wnt/beta-catenin signaling pathway promotes osteoblast differentiation, proliferation, and survival, leading to increased bone formation. Sclerostin, targeted by drugs like romosozumab, is a natural inhibitor of this pathway.

Question 7173

Topic: Biomechanics & Biomaterials

Which of the following biomechanical principles is the primary advantage of utilizing a locked plating construct over a conventional compression plate in osteoporotic bone?

. Increased frictional force between the plate and bone
. Dependence on the pullout strength of individual screws
. Functioning as a fixed-angle construct that resists toggling
. Dynamic compression of the fracture gap
. Lower modulus of elasticity of the entire construct

Correct Answer & Explanation

. Increased frictional force between the plate and bone

Explanation

Locked plating constructs function as single-beam, fixed-angle devices where the screw heads thread directly into the plate. This resists toggling and secondary loss of reduction, making them mechanically superior in osteoporotic bone where friction-based conventional plates often fail.

Question 7174

Topic: Biomechanics & Biomaterials

Which of the following best describes the phenomenon of 'creep' in the viscoelastic behavior of ligaments?

. A decrease in stress over time under a constant strain
. An increase in strain over time under a constant stress
. The failure of a material after repeated cyclic loading
. The loss of energy during a loading and unloading cycle
. The increase in stiffness with an increased rate of loading

Correct Answer & Explanation

. A decrease in stress over time under a constant strain

Explanation

Creep is defined as the progressive deformation (increase in strain) of a viscoelastic material over time when subjected to a constant load (stress). In contrast, stress relaxation is a decrease in stress over time under constant strain.

Question 7175

Topic: Biology, Genetics & Bone Healing

Primary (strain-free) bone healing is characterized by which of the following processes?

. Endochondral ossification
. Formation of a cartilaginous soft callus
. Direct osteoclastic cutting cones crossing the fracture site
. High strain environment (>10%)
. Woven bone formation bridging the fracture gap

Correct Answer & Explanation

. Endochondral ossification

Explanation

Primary bone healing occurs under conditions of absolute stability (strain <2%) and involves direct intramembranous healing via osteoclastic cutting cones. Subsequent osteoblast bone deposition occurs without intermediate callus formation.

Question 7176

Topic: Biology, Genetics & Bone Healing

Increasing the working length of a bridging plate construct leads to which of the following biomechanical changes?

. Increased axial stiffness
. Decreased axial stiffness
. Increased torsional stiffness
. Decreased construct micromotion
. Increased risk of implant failure due to stress shielding

Correct Answer & Explanation

. Increased axial stiffness

Explanation

Increasing the working length (the distance between the innermost screws on either side of the fracture) decreases the axial stiffness of the construct. This makes the fixation more flexible, promoting secondary bone healing through callus formation.

Question 7177

Topic: Biology, Genetics & Bone Healing

Bone morphogenetic proteins (BMPs) primarily induce osteoblast differentiation through which of the following intracellular signaling molecules?

. Beta-catenin
. Smad
. RANKL
. NF-kappa B
. STAT3

Correct Answer & Explanation

. Beta-catenin

Explanation

BMPs bind to serine/threonine kinase receptors on the cell surface, which subsequently phosphorylate intracellular Smad proteins (typically Smad 1, 5, and 8). These proteins then translocate to the nucleus to regulate the transcription of osteogenic genes.

Question 7178

Topic: 1. General Principles & Basic Science

In articular cartilage, which zone is characterized by the highest concentration of water, collagen fibers oriented parallel to the articular surface, and flattened chondrocytes?

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

Correct Answer & Explanation

. Superficial (tangential) zone

Explanation

The superficial zone of articular cartilage features collagen fibers aligned parallel to the surface to resist shear stress. It contains flattened chondrocytes and possesses the highest water content compared to deeper zones.

Question 7179

Topic: 1. General Principles & Basic Science

Which enzyme is essential for osteoclasts to create the acidic environment required for the dissolution of bone mineral in the resorption pit (Howship's lacuna)?

. Alkaline phosphatase
. Tartrate-resistant acid phosphatase
. Matrix metalloproteinase-9
. Carbonic anhydrase II
. Cathepsin K

Correct Answer & Explanation

. Alkaline phosphatase

Explanation

Carbonic anhydrase II generates protons (H+) from carbon dioxide and water. These protons are then actively pumped across the ruffled border into the resorption pit to lower the pH and dissolve hydroxyapatite.

Question 7180

Topic: 1. General Principles & Basic Science

According to the muscle length-tension curve, maximum active muscle force is generated at which of the following resting lengths?

. Maximal unphysiologic stretch
. Resting length where actin and myosin overlap is optimal
. Completely shortened length
. Zero overlap of actin and myosin
. Maximum passive tension length

Correct Answer & Explanation

. Maximal unphysiologic stretch

Explanation

The length-tension relationship dictates that maximum active force is produced at the optimal resting length of the sarcomere. At this length, there is maximal overlap of actin and myosin filaments for optimal cross-bridge formation.

Test Yourself

Switch to an interactive, timed exam simulation to truly master this topic.

On this Page