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1. General Principles & Basic Science MCQs

Practice Set 504 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 10061

Topic: Biomechanics & Biomaterials

Regarding advanced biomaterials for bone regeneration, which property of a porous scaffold is most critical for facilitating successful osteoinduction and bone ingrowth, beyond simple biocompatibility and mechanical strength?

. High Young's modulus to match cortical bone
. Microporosity of 1-10 µm for nutrient diffusion
. Macroporosity with interconnected pores of 100-500 µm
. Biodegradation rate that is significantly faster than new bone formation
. Hydrophobicity to repel inflammatory cells

Correct Answer & Explanation

. Macroporosity with interconnected pores of 100-500 µm

Explanation

Macroporosity with interconnected pores of 100-500 µm is most critical for bone regeneration. Pores in this range allow for the ingrowth of osteogenic cells, vascularization, and subsequent bone formation. Microporosity is important for nutrient diffusion but insufficient for cell ingrowth. A high Young's modulus can lead to stress shielding. A biodegradation rate matched to new bone formation is ideal, not significantly faster. Hydrophobicity is generally undesirable; a more hydrophilic surface often promotes cell adhesion.

Question 10062

Topic: 1. General Principles & Basic Science

Which of the following accurately describes the role of satellite cells in skeletal muscle physiology?

. They are terminally differentiated muscle fibers responsible for contraction.
. They are specialized neurons that innervate muscle fibers at the neuromuscular junction.
. They are multipotent stem cells located between the basal lamina and sarcolemma, crucial for muscle repair and growth.
. They are fibroblasts responsible for synthesizing the extracellular matrix of muscle tissue.
. They are immune cells that clear cellular debris after muscle injury.

Correct Answer & Explanation

. They are multipotent stem cells located between the basal lamina and sarcolemma, crucial for muscle repair and growth.

Explanation

Satellite cells are quiescent, multipotent stem cells located beneath the basal lamina and above the sarcolemma of skeletal muscle fibers. Upon muscle injury or during growth, they become activated, proliferate, and differentiate into new myofibers or fuse with existing ones, thereby playing a critical role in muscle regeneration, repair, and hypertrophy. The other options describe muscle fibers, neurons, fibroblasts, or immune cells, respectively.

Question 10063

Topic: Biomechanics & Biomaterials

Which biomechanical property best describes the time-dependent deformation of a material under a constant load, exemplified by the continued lengthening of a tendon when subjected to sustained tensile force?

. Elasticity
. Plasticity
. Viscosity
. Creep
. Stress relaxation

Correct Answer & Explanation

. Creep

Explanation

Creep is the time-dependent increase in deformation (strain) of a material under a constant applied load (stress). Tendons and ligaments, being viscoelastic materials, exhibit creep. Elasticity refers to reversible deformation. Plasticity refers to permanent deformation after load removal. Viscosity describes resistance to flow. Stress relaxation is the time-dependent decrease in stress within a material when it is held at a constant strain.

Question 10064

Topic: Biology, Genetics & Bone Healing

In the process of bone graft incorporation, which of the following mechanisms describes the process by which a graft material serves as a scaffold for the ingrowth of host osteogenic cells and blood vessels, ultimately leading to new bone formation on its surface?

. Osteoinduction
. Osteogenesis
. Osteoconduction
. Osseointegration
. Osteoclasis

Correct Answer & Explanation

. Osteoconduction

Explanation

Osteoconduction describes the ability of a bone graft material to serve as a passive scaffold for the ingrowth of new bone from the surrounding host tissue. It provides a framework for osteoblasts, capillaries, and mesenchymal stem cells to migrate, proliferate, and differentiate. Osteoinduction is the active stimulation of undifferentiated mesenchymal stem cells to differentiate into osteoblasts and form bone. Osteogenesis refers to the formation of new bone by viable cells within the graft itself. Osseointegration is the direct structural and functional connection between ordered, living bone and the surface of a load-bearing implant. Osteoclasis is bone resorption.

Question 10065

Topic: Biology, Genetics & Bone Healing
Regarding cellular events in secondary fracture healing, what is the primary role of the mesenchymal stem cells (MSCs) that migrate into the fracture hematoma during the inflammatory and reparative phases?
. To directly form woven bone without cartilage intermediate.
. To phagocytose cellular debris and inflammatory mediators.
. To differentiate into chondrocytes and osteoblasts, forming the soft and hard callus.
. To secrete growth factors that attract osteoclasts for remodeling.
. To form the initial granulation tissue rich in Type III collagen.

Correct Answer & Explanation

. To differentiate into chondrocytes and osteoblasts, forming the soft and hard callus.

Explanation

During secondary fracture healing, mesenchymal stem cells (MSCs) are recruited to the fracture site and differentiate into chondrocytes to form the soft callus (cartilage) and into osteoblasts to form the hard callus (woven bone). This process involves both endochondral and intramembranous ossification. The initial granulation tissue does form and contain Type III collagen, but the specific role of MSCs is their differentiation potential. Phagocytosis is by macrophages, and osteoclasts are for resorption.

Question 10066

Topic: Biology, Genetics & Bone Healing

In the context of bone remodeling, which cell type is primarily responsible for sensing mechanical loads and initiating appropriate adaptive responses by signaling to osteoblasts and osteoclasts?

. Osteoclasts
. Osteoblasts
. Bone lining cells
. Osteocytes
. Chondrocytes

Correct Answer & Explanation

. Osteocytes

Explanation

Osteocytes, embedded within the bone matrix and interconnected by canaliculi, are recognized as the primary mechanosensors of bone. They detect changes in mechanical strain and fluid flow, then translate these signals into biochemical cues (e.g., sclerostin, RANKL, OPG, prostaglandins, nitric oxide) that regulate the activity of osteoblasts (bone formation) and osteoclasts (bone resorption), thereby coordinating bone remodeling to adapt to mechanical demands. Osteoblasts form bone, osteoclasts resorb bone, and bone lining cells are quiescent osteoblasts.

Question 10067

Topic: Infection, Pharmacology & VTE

During implant-associated infections, bacteria often form biofilms. Which of the following is a key characteristic of biofilm-dwelling bacteria that contributes significantly to their increased resistance to antibiotics and host immune responses?

. Increased metabolic activity and rapid division rates.
. Enhanced expression of efflux pumps for antibiotic removal.
. Formation of an extracellular polymeric substance (EPS) matrix.
. Transition to a planktonic (free-floating) lifestyle.
. Up-regulation of specific virulence factors for host cell invasion.

Correct Answer & Explanation

. Formation of an extracellular polymeric substance (EPS) matrix.

Explanation

A key characteristic of bacteria within a biofilm is the production of an extracellular polymeric substance (EPS) matrix. This matrix, composed of polysaccharides, proteins, and DNA, encases the bacteria, providing a physical barrier against antibiotics and immune cells, reducing their penetration and efficacy. It also creates a unique microenvironment that alters bacterial metabolism and gene expression, contributing to increased resistance. Biofilm bacteria often have reduced metabolic activity, not increased. While efflux pumps and virulence factors can contribute to resistance, the EPS matrix is fundamental to biofilm-mediated resistance.

Question 10068

Topic: 1. General Principles & Basic Science

Which of the following describes the unique composition of the superficial zone of articular cartilage, contributing to its low friction and resistance to shear forces?

. High concentration of large aggregating proteoglycans like aggrecan.
. Predominance of perpendicularly oriented collagen fibers (Type II).
. Presence of superficial zone protein (SZP) / lubricin and a relatively high water content.
. Chondrocytes arranged in columns with abundant Type X collagen.
. High mineral content and low cellularity.

Correct Answer & Explanation

. Presence of superficial zone protein (SZP) / lubricin and a relatively high water content.

Explanation

The superficial (tangential) zone of articular cartilage is characterized by chondrocytes that are flattened and collagen fibers (primarily Type II) that are oriented parallel to the articular surface. Crucially, it contains Superficial Zone Protein (SZP), also known as lubricin, which is a glycoprotein that contributes significantly to the low friction and wear resistance of the articular surface. This zone also has a higher water content and lower proteoglycan content than deeper zones. Aggrecan is more abundant in deeper zones, Type X collagen in hypertrophic cartilage, and mineral content is absent in healthy articular cartilage.

Question 10069

Topic: Biology, Genetics & Bone Healing
What is the primary mechanism by which platelet-rich plasma (PRP) is theorized to promote tissue healing in orthopedic applications?
. Directly stimulating differentiation of mesenchymal stem cells into chondrocytes or osteoblasts.
. Delivering high concentrations of antibiotics to the injury site.
. Providing a structural scaffold for tissue regeneration.
. Releasing various growth factors, cytokines, and chemokines from alpha granules.
. Inducing a potent inflammatory response to clear damaged tissue.

Correct Answer & Explanation

. Releasing various growth factors, cytokines, and chemokines from alpha granules.

Explanation

Platelet-Rich Plasma (PRP) is an autologous blood product with a supra-physiological concentration of platelets. When activated, platelets release a multitude of growth factors (e.g., PDGF, TGF-β, VEGF, EGF, IGF-1) and other bioactive proteins from their alpha granules. These factors are crucial for promoting cell proliferation, differentiation, angiogenesis, and extracellular matrix synthesis, thereby enhancing tissue healing and regeneration. While it may indirectly influence MSCs or induce some inflammation, its primary mechanism is the delivery of these signaling molecules. It does not provide antibiotics or a structural scaffold directly.

Question 10070

Topic: Biology, Genetics & Bone Healing
Which type of collagen is predominantly found in healthy mature cortical bone, providing its high tensile strength?
. Type I collagen
. Type II collagen
. Type III collagen
. Type IV collagen
. Type X collagen

Correct Answer & Explanation

. Type I collagen

Explanation

Type I collagen is the most abundant protein in the human body and is the primary organic component (approximately 90%) of bone, skin, tendons, and ligaments. Its highly organized triple-helical structure provides immense tensile strength to cortical bone. Type II collagen is found in cartilage. Type III collagen is found in extensible connective tissues like blood vessels and early wound healing. Type IV collagen forms the basement membranes. Type X collagen is associated with hypertrophic cartilage.

Question 10071

Topic: Biology, Genetics & Bone Healing

A novel orthopedic implant is being developed with a surface modification designed to enhance osteointegration by mimicking the natural extracellular matrix. Which of the following strategies would be most effective at promoting specific cell adhesion and differentiation?

. Creating a smooth, polished surface to minimize bacterial colonization.
. Coating the surface with an inert polymer to reduce immune response.
. Incorporating RGD (Arginine-Glycine-Aspartic acid) peptides into the surface.
. Increasing the overall hydrophobicity of the implant material.
. Developing a microporous surface solely for enhanced nutrient diffusion.

Correct Answer & Explanation

. Incorporating RGD (Arginine-Glycine-Aspartic acid) peptides into the surface.

Explanation

Incorporating RGD (Arginine-Glycine-Aspartic acid) peptides into the implant surface is a highly effective strategy for promoting specific cell adhesion and differentiation. The RGD sequence is a common recognition motif for integrins, which are cell-surface receptors that mediate cell-extracellular matrix interactions. By providing RGD motifs, the implant surface can selectively bind to host cells (e.g., osteoblasts, mesenchymal stem cells) and trigger intracellular signaling pathways that promote osteointegration. Smooth surfaces can hinder cell adhesion, inert polymers might lack bioactivity, hydrophobicity generally discourages cell adhesion, and while microporosity is helpful, specific biological cues are more potent for directed cell behavior.

Question 10072

Topic: Biology, Genetics & Bone Healing

In the advanced stages of intervertebral disc degeneration, what is the primary change in the nucleus pulposus extracellular matrix that compromises its ability to withstand compressive loads?

. Increased collagen Type I content and reduced proteoglycans.
. Increased water content due to osmotic swelling.
. Decreased production of aggrecan and increased catabolism of proteoglycans.
. Hypertrophy of chondrocytes and mineralization.
. Proliferation of fibroblasts and increased vascularization.

Correct Answer & Explanation

. Decreased production of aggrecan and increased catabolism of proteoglycans.

Explanation

In advanced intervertebral disc degeneration, the primary change in the nucleus pulposus is a progressive decrease in the production of aggrecan (the main proteoglycan) and an increase in its catabolism. This leads to a reduction in the overall proteoglycan content, which in turn reduces the disc's ability to retain water. The loss of water-retaining capacity significantly compromises the nucleus pulposus's osmotic pressure and its ability to withstand compressive loads, leading to disc height loss and instability. While some collagen changes occur, the fundamental issue for load-bearing is proteoglycan loss and subsequent dehydration. Mineralization, vascularization, and chondrocyte hypertrophy are more characteristic of endplate changes or other tissues.

Question 10073

Topic: Biology, Genetics & Bone Healing

Which of the following best describes the molecular basis for the 'stress-shielding' phenomenon observed in bone adjacent to stiff metallic orthopedic implants?

. Direct mechanical trauma from the implant to the bone.
. Reduced bone remodeling due to a lack of strain-induced osteocyte signaling.
. Increased osteoclast activity in response to foreign body reaction.
. Enhanced osteoblast proliferation leading to cortical thinning.
. Conversion of compact bone into cancellous bone due to altered stress distribution.

Correct Answer & Explanation

. Reduced bone remodeling due to a lack of strain-induced osteocyte signaling.

Explanation

Stress-shielding occurs when a stiff orthopedic implant carries a disproportionately high share of the mechanical load, thereby reducing the stress (and strain) experienced by the adjacent bone. According to Wolff's Law, bone adapts to the loads placed upon it. When bone is 'shielded' from normal physiological stresses, osteocytes (the mechanosensors) detect reduced strain. This leads to reduced signaling for bone formation by osteoblasts and/or increased signaling for bone resorption by osteoclasts, resulting in a net loss of bone mass (osteopenia) in the shielded regions. It's a biological adaptation to altered mechanical environment, not direct trauma, foreign body reaction, or a direct increase in osteoblast proliferation.

Question 10074

Topic: Surgical Anatomy & Approaches

A 24-year-old athlete sustains a traction injury to the shoulder, presenting with weakness in forward elevation and isolated sensory loss over the lateral aspect of the proximal arm. An MRI reveals a compressive lesion within the quadrangular space.

What anatomical structure forms the medial border of this space?

. Teres minor
. Teres major
. Surgical neck of the humerus
. Long head of the triceps
. Lateral head of the triceps

Correct Answer & Explanation

. Surgical neck of the humerus

Explanation

The quadrangular space transmits the axillary nerve and the posterior circumflex humeral artery. Its borders are: Superiorly - Teres minor; Inferiorly - Teres major; Medially - Long head of the triceps; Laterally - Surgical neck of the humerus. The patient's symptoms (deltoid weakness and lateral arm sensory loss) are classic for axillary nerve pathology.

Question 10075

Topic: 1. General Principles & Basic Science

When repairing a bucket-handle tear of the medial meniscus, a surgeon places sutures in the extreme peripheral 'red-red' zone. The primary arterial supply to this peripheral 10-30% of the meniscus is derived directly from which of the following?

. Middle genicular artery
. Medial inferior genicular artery
. Descending branch of the lateral circumflex femoral artery
. Popliteal artery
. Anterior tibial recurrent artery

Correct Answer & Explanation

. Medial inferior genicular artery

Explanation

The vascular supply to the peripheral 10-30% of the medial meniscus is primarily provided by the medial inferior genicular artery and the medial superior genicular artery. The lateral meniscus is supplied by the lateral inferior genicular artery. The middle genicular artery pierces the posterior capsule to supply the cruciate ligaments.

Question 10076

Topic: Surgical Anatomy & Approaches

During a deltopectoral approach to the shoulder for a hemiarthroplasty, the internervous plane is developed. Which of the following statements regarding the handling of the cephalic vein during this approach is anatomically correct?

. It should be retracted medially to preserve venous drainage of the deltoid.
. It should be retracted laterally to preserve venous drainage of the deltoid.
. It is a direct tributary to the external jugular vein.
. It runs in the internervous plane between the axillary and median nerves.
. It must be ligated routinely to expose the subscapularis.

Correct Answer & Explanation

. It should be retracted laterally to preserve venous drainage of the deltoid.

Explanation

The deltopectoral approach uses the internervous plane between the deltoid (axillary nerve) and pectoralis major (medial and lateral pectoral nerves). The cephalic vein lies in this interval. It is generally recommended to retract the cephalic vein laterally with the deltoid to preserve its primary venous tributaries, which originate from the deltoid muscle.

Question 10077

Topic: Surgical Anatomy & Approaches

The volar approach to the radius (Henry approach) utilizes two different internervous planes depending on the region of the forearm. Proximally, the plane is between the brachioradialis and the pronator teres. Which nerves supply these two muscles, respectively?

. Radial and Ulnar
. Median and Radial
. Radial and Median
. Musculocutaneous and Median
. Radial and Anterior Interosseous

Correct Answer & Explanation

. Median and Radial

Explanation

The proximal internervous plane of the volar Henry approach is between the Brachioradialis (innervated by the Radial nerve) and the Pronator Teres (innervated by the Median nerve). The distal internervous plane is between the Brachioradialis (Radial nerve) and the Flexor Carpi Radialis (Median nerve).

Question 10078

Topic: Surgical Anatomy & Approaches

When performing an anterior approach to the hip (Smith-Petersen), the internervous plane is between the sartorius and the tensor fasciae latae superficially. Which of the following structures is at greatest risk of iatrogenic injury during the superficial dissection?

. Femoral nerve
. Lateral femoral cutaneous nerve
. Superior gluteal nerve
. Medial femoral circumflex artery
. Ascending branch of the lateral femoral circumflex artery

Correct Answer & Explanation

. Lateral femoral cutaneous nerve

Explanation

During the anterior approach to the hip (Smith-Petersen), the superficial internervous plane is between the Sartorius (Femoral nerve) and the Tensor Fasciae Latae (Superior Gluteal nerve). The Lateral Femoral Cutaneous Nerve (LFCN) typically crosses over the sartorius 2-3 cm distal to the ASIS and is at high risk of injury during this superficial dissection.

Question 10079

Topic: 1. General Principles & Basic Science

The cruciate anastomosis of the thigh is a vital collateral network that can provide distal limb perfusion in the setting of an acute occlusion of the superficial femoral artery. Which of the following vessels is NOT a component of this anatomotic ring?

. Inferior gluteal artery
. Medial femoral circumflex artery
. Lateral femoral circumflex artery
. First perforating artery of the profunda femoris
. Superior gluteal artery

Correct Answer & Explanation

. Superior gluteal artery

Explanation

The cruciate anastomosis of the upper thigh is formed by the union of four arteries: the inferior gluteal artery (descending branch), the lateral femoral circumflex artery (transverse branch), the medial femoral circumflex artery (transverse branch), and the first perforating artery of the profunda femoris (ascending branch). The superior gluteal artery does not participate directly in the cruciate anastomosis.

Question 10080

Topic: Surgical Anatomy & Approaches

A trauma surgeon is applying a lateral plate to the humerus for a highly displaced midshaft fracture. To safely expose the bone distally, the path of the radial nerve must be meticulously protected. At what approximate distance proximal to the lateral epicondyle does the radial nerve typically pierce the lateral intermuscular septum to enter the anterior compartment of the arm?

. 2-3 cm
. 5-6 cm
. 10-12 cm
. 15-16 cm
. 18-20 cm

Correct Answer & Explanation

. 10-12 cm

Explanation

The radial nerve runs in the spiral groove of the posterior humerus and typically pierces the lateral intermuscular septum approximately 10 to 12 cm proximal to the lateral epicondyle to enter the anterior compartment of the arm. It then travels distally between the brachialis and brachioradialis muscles.

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