Menu

1. General Principles & Basic Science MCQs

Practice Set 279 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 5561

Topic: Biology, Genetics & Bone Healing

Demineralized bone matrix (DBM) is commonly used as a biological adjunct in spinal fusion. Which of the following best characterizes its bone healing properties?

. Osteoconductive and osteogenic
. Osteoinductive and osteogenic
. Osteoconductive and osteoinductive
. Osteogenic only
. Osteoinductive only

Correct Answer & Explanation

. Osteoconductive and osteoinductive

Explanation

DBM provides a collagen scaffold (osteoconductive) and contains bone morphogenetic proteins that stimulate bone formation (osteoinductive). However, it lacks live bone cells and is therefore not osteogenic.

Question 5562

Topic: 1. General Principles & Basic Science

Parathyroid hormone (PTH) regulates serum calcium levels through multiple systemic mechanisms. What is its direct physiological effect on the kidney?

. Decreases calcium reabsorption and decreases phosphate excretion
. Increases calcium reabsorption and increases phosphate excretion
. Increases both calcium and phosphate reabsorption
. Decreases both calcium and phosphate reabsorption
. Increases production of 24,25-dihydroxyvitamin D

Correct Answer & Explanation

. Increases calcium reabsorption and increases phosphate excretion

Explanation

In the kidney, PTH directly increases tubular reabsorption of calcium and increases phosphate excretion (phosphaturia). It also stimulates the conversion of 25-hydroxyvitamin D to its active form, 1,25-dihydroxyvitamin D.

Question 5563

Topic: Biomechanics & Biomaterials

Galvanic corrosion occurs when two dissimilar metals are placed in physical contact within a conductive fluid environment. Which of the following metal combinations is most likely to result in significant galvanic corrosion in orthopedic implants?

. Titanium alloy and Cobalt-Chromium
. Stainless steel and Titanium alloy
. Cobalt-Chromium and Trabecular metal (Tantalum)
. Two distinct Titanium alloy components
. Cobalt-Chromium and Zirconium

Correct Answer & Explanation

. Stainless steel and Titanium alloy

Explanation

Mixing stainless steel and titanium alloy implants in the same construct creates a large electrochemical potential difference, leading to severe galvanic corrosion. In contrast, mixing titanium and cobalt-chromium is generally well tolerated.

Question 5564

Topic: Biology, Genetics & Bone Healing

Cigarette smoking strongly inhibits bone healing and significantly increases the rate of nonunion. Which of the following is the primary physiological mechanism driving this adverse effect?

. Direct stimulation of osteoclast activity by nicotine
. Inhibition of angiogenesis and cellular hypoxia secondary to carbon monoxide and nicotine
. Depletion of systemic calcium reserves
. Upregulation of matrix metalloproteinases in the fracture callus
. Suppression of bone morphogenetic protein-2 (BMP-2) synthesis

Correct Answer & Explanation

. Inhibition of angiogenesis and cellular hypoxia secondary to carbon monoxide and nicotine

Explanation

Nicotine acts as a potent vasoconstrictor, while carbon monoxide competitively binds hemoglobin to reduce oxygen delivery. Together, they cause significant tissue hypoxia and inhibit angiogenesis, which critically impairs the fracture healing process.

Question 5565

Topic: 1. General Principles & Basic Science

Muscle strain injuries most commonly occur at the myotendinous junction. Biomechanically, what microscopic structural feature of this junction makes it uniquely susceptible to these injuries?

. The abrupt transition from type I to type II collagen
. High regional vascularity leading to structural mechanical weakness
. The interdigitation of muscle cell membrane with tendon collagen, causing peak stress concentration
. The complete absence of proteoglycans at the interface
. The change from a highly rigid to a highly elastic tissue without a buffer zone

Correct Answer & Explanation

. The interdigitation of muscle cell membrane with tendon collagen, causing peak stress concentration

Explanation

The myotendinous junction features complex microscopic interdigitation between muscle fibers and tendon collagen. This geometric arrangement creates a localized site of significant stress concentration during eccentric loading, predisposing it to failure.

Question 5566

Topic: 1. General Principles & Basic Science

The deep zone of articular cartilage is best characterized by which of the following combinations of properties?

. Highest water content and parallel collagen fibers
. Highest concentration of proteoglycans and parallel collagen fibers
. Highest concentration of proteoglycans and perpendicular collagen fibers
. Lowest water content and random collagen fiber orientation
. Highest concentration of collagen and perpendicular collagen fibers

Correct Answer & Explanation

. Highest concentration of proteoglycans and perpendicular collagen fibers

Explanation

The deep zone of articular cartilage contains the highest concentration of proteoglycans and the lowest water content. Its Type II collagen fibers are oriented perpendicularly to the subchondral bone to resist compressive loads.

Question 5567

Topic: Biology, Genetics & Bone Healing

Which cytokine serves as the primary decoy receptor for RANKL, thereby inhibiting osteoclastogenesis and reducing bone resorption?

. Interleukin-1 (IL-1)
. Macrophage colony-stimulating factor (M-CSF)
. Osteoprotegerin (OPG)
. Tumor necrosis factor-alpha (TNF-alpha)
. Sclerostin

Correct Answer & Explanation

. Osteoprotegerin (OPG)

Explanation

Osteoprotegerin (OPG) is a glycoprotein secreted by osteoblasts that acts as a decoy receptor for RANKL. By binding RANKL, OPG prevents it from interacting with RANK on osteoclast precursors, inhibiting osteoclast differentiation.

Question 5568

Topic: Biomechanics & Biomaterials

When a constant load is applied to a viscoelastic ligament over an extended period of time, the tissue gradually elongates. This biomechanical phenomenon is known as:

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

Correct Answer & Explanation

. Creep

Explanation

Creep describes the time-dependent elongation of viscoelastic tissues under a constant load. Conversely, stress relaxation is the decrease in internal stress over time when the tissue is held at a constant length.

Question 5569

Topic: 1. General Principles & Basic Science

Which of the following geometric alterations to a cortical screw design will most significantly increase its pullout strength?

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

Correct Answer & Explanation

. Decreasing the thread pitch

Explanation

Screw pullout strength is increased by maximizing the volume of bone engaged by the threads. This is achieved by increasing the outer diameter, decreasing the inner diameter, or decreasing the thread pitch (more threads per unit length).

Question 5570

Topic: Physiology & Rehabilitation

Type I (slow-twitch) skeletal muscle fibers are primarily characterized by which type of metabolism and fatigue resistance?

. Oxidative metabolism; high resistance to fatigue
. Glycolytic metabolism; high resistance to fatigue
. Oxidative metabolism; low resistance to fatigue
. Glycolytic metabolism; low resistance to fatigue
. Anaerobic metabolism; moderate resistance to fatigue

Correct Answer & Explanation

. Oxidative metabolism; high resistance to fatigue

Explanation

Type I muscle fibers rely on oxidative metabolism and have a high density of mitochondria and myoglobin. This allows them to maintain sustained, low-intensity contractions with a very high resistance to fatigue.

Question 5571

Topic: 1. General Principles & Basic Science
According to Sunderland's classification of peripheral nerve injuries, a fourth-degree injury involves disruption of all the following structures EXCEPT the:
. Axon
. Myelin sheath
. Endoneurium
. Perineurium
. Epineurium

Correct Answer & Explanation

. Perineurium

Explanation

A Sunderland fourth-degree nerve injury completely disrupts the axon, endoneurium, and perineurium, leaving only the epineurium intact. Because severe internal scarring occurs, surgical intervention is almost always required for recovery.

Question 5572

Topic: Biology, Genetics & Bone Healing

During secondary fracture healing, peak expression of Type II collagen occurs during which of the following stages?

. Hematoma formation
. Inflammatory phase
. Soft callus formation
. Hard callus formation
. Remodeling phase

Correct Answer & Explanation

. Soft callus formation

Explanation

Soft callus formation is characterized by chondrogenesis and the production of a cartilaginous matrix rich in Type II collagen. This is later replaced by woven bone (Type I collagen) during hard callus formation.

Question 5573

Topic: Biomechanics & Biomaterials

Which of the following combinations of implant alloys placed in direct physical contact poses the highest risk of significant galvanic corrosion?

. Titanium alloy and Commercially pure titanium
. Cobalt-chromium and Titanium alloy
. Stainless steel and Titanium alloy
. Cobalt-chromium and Ceramic
. Tantalum and Titanium alloy

Correct Answer & Explanation

. Stainless steel and Titanium alloy

Explanation

Stainless steel and titanium have widely separated resting potentials on the galvanic series, resulting in a high risk of galvanic corrosion when they are coupled. In contrast, mixing cobalt-chromium and titanium is generally well-tolerated.

Question 5574

Topic: 1. General Principles & Basic Science

Which mechanism of joint lubrication is most critical for protecting articular surfaces under high-load, low-speed conditions, such as initial standing from a seated position?

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

Correct Answer & Explanation

. Boundary lubrication

Explanation

Boundary lubrication predominates under high-load and low-speed conditions when the fluid film breaks down. It relies on a monomolecular layer of lubricin (PRG4) to coat the articular surfaces and prevent direct wear.

Question 5575

Topic: Biology, Genetics & Bone Healing

A massive structural cortical allograft is utilized to reconstruct a large segmental bone defect. The graft is incorporated into the host primarily via which biologic process?

. Rapid revascularization and endochondral ossification
. Membranous ossification without resorption
. Creeping substitution
. Osteoinduction driven by high endogenous BMP levels
. Chondrogenesis and subsequent remodeling

Correct Answer & Explanation

. Creeping substitution

Explanation

Structural cortical allografts incorporate slowly via creeping substitution, a process where host osteoclasts resorb the dead graft bone while host osteoblasts simultaneously lay down new woven bone. Deep revascularization is often minimal.

Question 5576

Topic: 1. General Principles & Basic Science

Microscopically, which of the following is a primary structural difference between ligaments and tendons?

. Ligaments possess a higher concentration of Type II collagen
. Ligaments feature a more strictly parallel alignment of collagen fibers
. Ligaments contain slightly more elastin and have a more interlacing collagen architecture
. Ligaments have inherently greater vascularity and healing potential
. Ligaments are entirely devoid of mechanoreceptors

Correct Answer & Explanation

. Ligaments contain slightly more elastin and have a more interlacing collagen architecture

Explanation

Compared to tendons, ligaments possess a slightly higher elastin content and a more variable, interlacing collagen fiber orientation. This unique structure allows ligaments to resist complex, multidirectional tensile forces.

Question 5577

Topic: 1. General Principles & Basic Science

During the propagation of a typical neuronal action potential, the rapid depolarization phase is directly mediated by the influx of which of the following ions?

. Potassium
. Calcium
. Sodium
. Chloride
. Magnesium

Correct Answer & Explanation

. Sodium

Explanation

The rapid depolarization phase of an action potential is driven by the opening of voltage-gated sodium channels, allowing a massive influx of sodium ions. Subsequent repolarization is driven by the efflux of potassium ions.

Question 5578

Topic: Biology, Genetics & Bone Healing

According to Wolff's Law, bone adapts its architecture in response to mechanical stress. The primary mechanosensory cell responsible for detecting fluid shear stress in the bone matrix is the:

. Osteoblast
. Osteoclast
. Osteocyte
. Mesenchymal stem cell
. Chondrocyte

Correct Answer & Explanation

. Osteocyte

Explanation

Osteocytes, residing within the lacunocanalicular network, act as the primary mechanosensors in bone. They detect fluid shear stress caused by mechanical loading and orchestrate remodeling by signaling osteoblasts and osteoclasts.

Question 5579

Topic: 1. General Principles & Basic Science
During the normal process of tendon healing, the transition from disorganized Type III collagen synthesis to more aligned Type I collagen synthesis begins prominently during which phase?
. Inflammatory phase
. Proliferative (fibroblastic) phase
. Remodeling phase
. Maturation phase
. Hemostasis phase

Correct Answer & Explanation

. Proliferative (fibroblastic) phase

Explanation

The proliferative phase (peaking around 2-4 weeks) is characterized by high cellularity and the synthesis of primarily Type III collagen, which gradually transitions into the production of stronger Type I collagen as remodeling begins.

Question 5580

Topic: Biomechanics & Biomaterials

The unique ability of articular cartilage to withstand massive compressive loads is primarily determined by the biomechanical interaction between:

. Type I collagen and hydroxyapatite
. Aggrecan-associated swelling pressure and the tensile restraint of the Type II collagen network
. Hyaluronic acid viscosity and boundary lubricin
. Chondrocyte hypertrophy and matrix metalloproteinases
. Elastin fibers and synovial fluid glycoproteins

Correct Answer & Explanation

. Aggrecan-associated swelling pressure and the tensile restraint of the Type II collagen network

Explanation

Compressive stiffness in articular cartilage is derived from the Donnan osmotic swelling pressure generated by negatively charged aggrecan molecules attracting water. This swelling is tightly restrained by the strong, tensile Type II collagen network.

Test Yourself

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

On this Page