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1. General Principles & Basic Science MCQs

Practice Set 372 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 7421

Topic: Biology, Genetics & Bone Healing

What is the primary function of the Volkmann's canals in cortical bone?

. To house osteocytes and their canaliculi
. To connect adjacent Haversian canals and provide vascular and neural communication
. To provide channels for nutrient diffusion to chondrocytes
. To serve as a reservoir for bone marrow
. To facilitate communication between trabeculae in cancellous bone

Correct Answer & Explanation

. To house osteocytes and their canaliculi

Explanation

Volkmann's canals are horizontal channels that connect adjacent Haversian canals (which run longitudinally) and also connect Haversian canals to the periosteal and endosteal surfaces. They contain blood vessels and nerves, facilitating the intricate vascular and neural network within cortical bone. Lacunae house osteocytes, and canaliculi connect lacunae. Cancellous bone structure is different.

Question 7422

Topic: 1. General Principles & Basic Science

Regarding muscle physiology, which statement about Type IIx (fast glycolytic) muscle fibers is correct?

. They have high mitochondrial density and are fatigue-resistant.
. They are primarily involved in sustained, low-intensity activities.
. They generate force rapidly but fatigue quickly.
. They have a high oxidative capacity.
. They are red in color due to high myoglobin content.

Correct Answer & Explanation

. They have high mitochondrial density and are fatigue-resistant.

Explanation

Type IIx (fast glycolytic) muscle fibers are characterized by a high rate of force generation, rapid contraction speed, and high anaerobic capacity, but they fatigue very quickly due to low mitochondrial density and low oxidative capacity. They are white in color due to low myoglobin content. Type I (slow oxidative) fibers are fatigue-resistant, have high mitochondrial density, and are red. Type IIa (fast oxidative-glycolytic) fibers are intermediate.

Question 7423

Topic: 1. General Principles & Basic Science

What is the primary function of the Golgi tendon organ?

. Detect muscle stretch and initiate the stretch reflex.
. Monitor muscle length and rate of change of length.
. Sense muscle tension and inhibit muscle contraction if tension is too high.
. Detect pain from muscle injury.
. Regulate muscle spindle sensitivity.

Correct Answer & Explanation

. Detect muscle stretch and initiate the stretch reflex.

Explanation

The Golgi tendon organ (GTO) is a proprioceptor located in the musculotendinous junction. Its primary function is to sense muscle tension. When tension becomes excessive, the GTO sends inhibitory signals via Ib afferents to the motor neurons of the same muscle, causing it to relax, thereby protecting the muscle and tendon from injury. Muscle spindles detect muscle length and stretch.

Question 7424

Topic: Physiology & Rehabilitation

Which of the following statements regarding the role of calcium in muscle contraction is FALSE?

. Calcium is stored in the sarcoplasmic reticulum.
. Calcium binds to troponin C, initiating the conformational change.
. Calcium release into the sarcoplasm is triggered by an action potential.
. Calcium directly binds to myosin heads to facilitate cross-bridge formation.
. ATP is required for calcium reuptake into the sarcoplasmic reticulum.

Correct Answer & Explanation

. Calcium is stored in the sarcoplasmic reticulum.

Explanation

Calcium does not directly bind to myosin heads to facilitate cross-bridge formation. Instead, calcium binds to troponin C, which then causes a conformational change in the troponin-tropomyosin complex, exposing the myosin-binding sites on the actin filaments. Myosin heads then bind to actin, initiating the power stroke. All other statements are correct regarding the role of calcium in excitation-contraction coupling.

Question 7425

Topic: Biology, Genetics & Bone Healing

Which type of collagen is predominantly found in fibrocartilage, such as that of the meniscus or intervertebral disc?

. Type I collagen
. Type II collagen
. Type III collagen
. Type IV collagen
. Type IX collagen

Correct Answer & Explanation

. Type I collagen

Explanation

Fibrocartilage, found in structures like the menisci, intervertebral discs, and labrum, is primarily composed of Type I collagen, providing significant tensile strength. Type II collagen is characteristic of hyaline cartilage. Type III is found in skin and blood vessels. Type IV is found in basement membranes. Type IX is a minor component of hyaline cartilage.

Question 7426

Topic: 1. General Principles & Basic Science

What is the primary biomechanical function of the subchondral bone in a healthy joint?

. To provide structural rigidity to the overlying articular cartilage
. To serve as a metabolic reservoir for chondrocytes
. To dissipate compressive loads and prevent direct stress on articular cartilage
. To enhance lubrication of the joint
. To regulate the diffusion of nutrients to the cartilage

Correct Answer & Explanation

. To provide structural rigidity to the overlying articular cartilage

Explanation

The subchondral bone acts as a shock absorber, dissipating compressive loads applied across the joint and protecting the overlying articular cartilage from excessive stress. While it does provide structural support, its primary biomechanical role is energy absorption. Nutrient diffusion primarily occurs from synovial fluid. It is not a direct metabolic reservoir for chondrocytes in the same way as synovial fluid.

Question 7427

Topic: 1. General Principles & Basic Science

Regarding the healing of a meniscal tear, which zone has the highest potential for intrinsic repair?

. White-white zone (avascular zone)
. Red-white zone (borderline vascularity)
. Red-red zone (vascularized periphery)
. Transitional zone (between red-red and red-white)
. Central articular zone

Correct Answer & Explanation

. White-white zone (avascular zone)

Explanation

The red-red zone, which is the peripheral 10-30% of the meniscus, has a direct blood supply from the capsular arteries. Tears in this zone have the highest potential for healing through repair due to the presence of blood-borne healing factors. The red-white zone has limited potential, and the white-white zone is avascular with very poor intrinsic healing capacity.

Question 7428

Topic: 1. General Principles & Basic Science

Which of the following statements about the role of synovial fluid is FALSE?

. It provides lubrication to articular cartilage.
. It supplies nutrients to articular cartilage.
. It removes metabolic waste products from articular cartilage.
. Its viscosity decreases with increasing shear rate (non-Newtonian fluid).
. It contains abundant fibroblasts for repair.

Correct Answer & Explanation

. It provides lubrication to articular cartilage.

Explanation

Synovial fluid is acellular, containing very few cells, primarily synoviocytes, macrophages, and lymphocytes, but not abundant fibroblasts for repair. Its primary roles are lubrication (due to hyaluronic acid and lubricin), nutrition, and waste removal for the avascular articular cartilage. It is a non-Newtonian fluid, meaning its viscosity changes with shear rate, becoming less viscous with movement, which is beneficial for joint function.

Question 7429

Topic: 1. General Principles & Basic Science

Which of the following nerve injuries carries the best prognosis for recovery?

. Neurotmesis
. Axonotmesis
. First-degree neuropraxia
. Second-degree neuropraxia
. Third-degree neuropraxia

Correct Answer & Explanation

. Neurotmesis

Explanation

First-degree neuropraxia (Sunderland classification, equivalent to Seddon's neuropraxia) involves a temporary conduction block with intact axons and connective tissue sheaths. Recovery is complete, usually within days to weeks. Axonotmesis involves axonal damage but intact endoneurium, with Wallerian degeneration and potential for recovery. Neurotmesis involves complete severance of the nerve, requiring surgical repair with the poorest prognosis. Sunderland's classification has 5 degrees, with neuropraxia generally encompassing the mildest forms (1st degree).

Question 7430

Topic: Biology, Genetics & Bone Healing

A common mechanism for bone loss in metabolic conditions involves an imbalance in the RANKL/OPG ratio. An increase in which of these would lead to increased bone resorption?

. Increased OPG production
. Decreased RANKL production
. Increased RANKL expression by osteoblasts and stromal cells
. Increased binding of OPG to RANK
. Decreased activation of RANK receptors

Correct Answer & Explanation

. Increased OPG production

Explanation

An increase in RANKL expression by osteoblasts and stromal cells leads to more RANKL available to bind to RANK receptors on osteoclast precursors, thereby increasing osteoclast differentiation, activation, and survival, resulting in increased bone resorption. Increased OPG production or increased binding of OPG to RANK would inhibit osteoclast activity. Decreased RANKL production or decreased activation of RANK receptors would also lead to reduced bone resorption.

Question 7431

Topic: Biomechanics & Biomaterials

Which of the following describes the 'creep' phenomenon in viscoelastic materials like bone or ligaments?

. Immediate deformation under a sudden load.
. Time-dependent increase in deformation under a constant load.
. Decrease in stress over time when held at a constant deformation.
. The material's ability to withstand repeated loading cycles.
. The point at which permanent deformation begins.

Correct Answer & Explanation

. Immediate deformation under a sudden load.

Explanation

Creep is the time-dependent increase in deformation (strain) of a material when subjected to a constant load (stress) over time. Stress relaxation, conversely, is the time-dependent decrease in stress when a material is held at a constant deformation. Viscoelastic materials exhibit both creep and stress relaxation. Immediate deformation is elastic or plastic response. Fatigue relates to repeated loading. Yield point marks the onset of plastic deformation.

Question 7432

Topic: Biology, Genetics & Bone Healing

What is the key histological feature distinguishing osteoid from mature bone matrix?

. Presence of collagen fibers
. Presence of osteocytes
. Lack of mineralization
. Higher cellularity
. Presence of Haversian systems

Correct Answer & Explanation

. Presence of collagen fibers

Explanation

Osteoid is the unmineralized organic matrix produced by osteoblasts. Mature bone matrix is osteoid that has subsequently undergone mineralization with hydroxyapatite crystals. Both contain collagen fibers (primarily type I) and osteocytes. Haversian systems are features of cortical bone structure, not a distinction of osteoid itself.

Question 7433

Topic: Biology, Genetics & Bone Healing

A patient with a distal radius fracture is treated with closed reduction and casting. Which of the following cells are the first to arrive and initiate the fracture healing cascade?

. Osteoblasts
. Chondrocytes
. Fibroblasts
. Polymorphonuclear leukocytes (neutrophils)
. Macrophages and lymphocytes

Correct Answer & Explanation

. Osteoblasts

Explanation

In the initial inflammatory phase of fracture healing, the first cells to arrive at the fracture site are polymorphonuclear leukocytes (neutrophils), followed shortly by macrophages and lymphocytes. These cells are crucial for clearing debris and initiating the inflammatory cascade. Osteoblasts and chondrocytes appear later as the repair phase begins.

Question 7434

Topic: Biology, Genetics & Bone Healing

Which major cell type is primarily responsible for the degradation of the cartilaginous callus during endochondral ossification in fracture healing?

. Osteoblasts
. Osteoclasts
. Chondrocytes
. Fibroblasts
. Macrophages

Correct Answer & Explanation

. Osteoblasts

Explanation

During endochondral ossification, osteoclasts are the primary cells responsible for resorbing the calcified cartilage matrix (the cartilaginous callus) to create space for invading blood vessels and subsequent osteoblast-mediated bone formation. Chondrocytes produce the cartilage, and osteoblasts lay down new bone matrix. Macrophages clear debris.

Question 7435

Topic: Biology, Genetics & Bone Healing

What is the primary role of vitamin D in bone metabolism?

. Directly stimulates osteoclast activity.
. Increases intestinal absorption of calcium and phosphate.
. Inhibits parathyroid hormone secretion.
. Promotes collagen synthesis by osteoblasts.
. Enhances renal excretion of calcium.

Correct Answer & Explanation

. Directly stimulates osteoclast activity.

Explanation

The primary role of activated vitamin D (calcitriol) is to increase intestinal absorption of calcium and phosphate, thereby ensuring adequate mineral availability for bone mineralization. It also has direct effects on bone remodeling and kidney function, but intestinal absorption is its most prominent and critical function for bone health. It does not directly stimulate osteoclast activity, but adequate calcium levels are essential for bone turnover.

Question 7436

Topic: Infection, Pharmacology & VTE

A patient with severe osteoarthritis of the knee is prescribed an NSAID. What is the primary mechanism of action of NSAIDs?

. Inhibition of leukotriene synthesis.
. Selective blockade of TNF-alpha.
. Inhibition of cyclooxygenase enzymes (COX-1 and COX-2).
. Stimulation of opioid receptors.
. Enhancement of cartilage repair.

Correct Answer & Explanation

. Inhibition of leukotriene synthesis.

Explanation

Non-steroidal anti-inflammatory drugs (NSAIDs) primarily exert their analgesic and anti-inflammatory effects by inhibiting cyclooxygenase (COX) enzymes (COX-1 and COX-2). This inhibition reduces the synthesis of prostaglandins, which are key mediators of pain and inflammation. They do not selectively block TNF-alpha (biologics do), stimulate opioid receptors, or directly enhance cartilage repair. Some NSAIDs also inhibit leukotriene synthesis, but COX inhibition is the main mechanism.

Question 7437

Topic: Infection, Pharmacology & VTE

Which antibiotic class is commonly used for prophylactic coverage in orthopedic surgery, particularly against Gram-positive bacteria like Staphylococcus aureus?

. Fluoroquinolones (e.g., Ciprofloxacin)
. Aminoglycosides (e.g., Gentamicin)
. First or second-generation Cephalosporins (e.g., Cefazolin)
. Macrolides (e.g., Azithromycin)
. Tetracyclines (e.g., Doxycycline)

Correct Answer & Explanation

. Fluoroquinolones (e.g., Ciprofloxacin)

Explanation

First or second-generation cephalosporins, such as Cefazolin, are the antibiotics of choice for surgical prophylaxis in most orthopedic procedures. They provide excellent coverage against common surgical site infection pathogens, particularly Gram-positive bacteria like Staphylococcus aureus, while having a relatively narrow spectrum compared to broader agents. Fluoroquinolones and aminoglycosides have broader spectrums and are typically reserved for established infections or specific indications. Macrolides and tetracyclines are generally not first-line for surgical prophylaxis.

Question 7438

Topic: Infection, Pharmacology & VTE

A patient is undergoing revision hip arthroplasty due to a suspected infection. Which laboratory marker is most sensitive for detecting chronic osteomyelitis?

. White Blood Cell (WBC) count
. Erythrocyte Sedimentation Rate (ESR)
. C-Reactive Protein (CRP)
. Procalcitonin
. Serum Creatinine

Correct Answer & Explanation

. White Blood Cell (WBC) count

Explanation

While both ESR and CRP are elevated in infection, ESR tends to remain elevated for a longer duration in chronic infections like osteomyelitis compared to CRP, which normalizes more rapidly. CRP is generally more sensitive for acute infections. WBC count is often normal in chronic osteomyelitis. Procalcitonin is typically used for severe systemic bacterial infections (sepsis). Serum creatinine assesses renal function.

Question 7439

Topic: Biomechanics & Biomaterials

What is the primary role of polymethylmethacrylate (PMMA) bone cement in joint arthroplasty?

. To provide direct biological fixation to bone.
. To act as a load-bearing structural component.
. To fill the space between the implant and bone, allowing for immediate mechanical interlock.
. To release antibiotics for infection prophylaxis.
. To promote osteointegration of the implant.

Correct Answer & Explanation

. To provide direct biological fixation to bone.

Explanation

PMMA bone cement functions as a grout, filling the irregularities between the implant and the bone, and then polymerizes to create a mechanical interlock. It is not a biological adhesive and does not promote osteointegration. It transfers stress between the implant and bone but is not typically considered a primary load-bearing structural component in the same way the implant itself is. While antibiotics can be added to cement, its primary role is mechanical fixation.

Question 7440

Topic: 1. General Principles & Basic Science

Which of the following is considered a relative contraindication to the use of a tourniquet in orthopedic surgery?

. Diabetes mellitus
. Sickle cell trait
. Peripheral vascular disease
. Local skin infection at the tourniquet site
. Hypertension

Correct Answer & Explanation

. Diabetes mellitus

Explanation

Peripheral vascular disease (PVD) is a relative contraindication to tourniquet use due to the risk of exacerbating ischemia, thrombosis, or arterial damage in compromised vessels. While diabetes and sickle cell trait require careful consideration and monitoring, PVD carries a more direct risk of limb ischemia. Local skin infection is an absolute contraindication, not relative. Hypertension is generally managed medically and not a direct contraindication.

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