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1. General Principles & Basic Science MCQs

Practice Set 703 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 14041

Topic: 1. General Principles & Basic Science
Unlike articular hyaline cartilage, which of the following represents the most abundant collagen type found in the menisci of the knee?
. Type I
. Type II
. Type III
. Type IX
. Type X

Correct Answer & Explanation

. Type I

Explanation

The meniscus is composed of fibrocartilage, which relies on high tensile strength to withstand hoop stresses. Approximately 90% of the collagen in the meniscus is Type I, distinguishing it from the predominantly Type II collagen of hyaline cartilage.

Question 14042

Topic: Biology, Genetics & Bone Healing

Nitrogen-containing bisphosphonates, such as alendronate, inhibit osteoclast function by interfering with which of the following biochemical pathways?

. RANKL-RANK interaction
. Wnt/beta-catenin signaling
. Mevalonate pathway
. Cathepsin K activity
. Carbonic anhydrase II

Correct Answer & Explanation

. Mevalonate pathway

Explanation

Nitrogen-containing bisphosphonates inhibit farnesyl pyrophosphate synthase within the mevalonate pathway. This prevents the prenylation of small regulatory GTPases (like Ras and Rho), ultimately leading to osteoclast apoptosis.

Question 14043

Topic: 1. General Principles & Basic Science

Following a complete peripheral nerve transection and successful epineural primary repair, at what approximate rate does axonal regeneration proceed distally?

. 0.1 mm/day
. 1 mm/day
. 3 mm/day
. 5 mm/day
. 10 mm/day

Correct Answer & Explanation

. 1 mm/day

Explanation

After completing Wallerian degeneration, the proximal axonal stump sprouts and regenerates distally. Under optimal conditions, this regeneration occurs at approximately 1 mm per day, or about 1 inch per month.

Question 14044

Topic: Biomechanics & Biomaterials

Which of the following best defines the biomechanical phenomenon of 'creep' in orthopedic biomaterials?

. Progressive deformation of a material under a constant load over time
. Decrease in stress over time when a material is held at a constant strain
. Microstructural failure due to cyclic loading below the yield strength
. Loss of mechanical strength due to environmental corrosion
. Energy lost as heat during the loading and unloading cycle

Correct Answer & Explanation

. Progressive deformation of a material under a constant load over time

Explanation

Creep is defined as the progressive, time-dependent plastic deformation of a material subjected to a constant stress (load). Conversely, stress relaxation refers to the decrease in stress over time under a constant strain.

Question 14045

Topic: Biology, Genetics & Bone Healing

A 55-year-old woman with end-stage renal disease presents with diffuse bone pain. Labs show elevated PTH, hypocalcemia, and hyperphosphatemia. Which bone histomorphometric finding is most characteristic of her primary skeletal pathology?

. Increased osteoid seams and decreased mineralization rate
. Mosaic pattern of prominent cement lines
. Thickened cortical bone with narrowed medullary cavity
. Defective osteoclast ruffled borders
. Extensive woven bone and dissecting osteitis

Correct Answer & Explanation

. Extensive woven bone and dissecting osteitis

Explanation

The patient has renal osteodystrophy with secondary hyperparathyroidism, leading to osteitis fibrosa cystica. The hallmark histologic features include dissecting osteitis, marrow fibrosis, and replacement of lamellar bone with extensive woven bone.

Question 14046

Topic: Biology, Genetics & Bone Healing

Which of the following local biologic factors has the most potent osteoinductive effect, driving the differentiation of mesenchymal stem cells directly into osteoblasts?

. Platelet-derived growth factor (PDGF)
. Bone morphogenetic protein-2 (BMP-2)
. Transforming growth factor-beta (TGF-beta)
. Insulin-like growth factor-1 (IGF-1)
. Fibroblast growth factor (FGF)

Correct Answer & Explanation

. Bone morphogenetic protein-2 (BMP-2)

Explanation

BMPs (especially BMP-2 and BMP-7) are potent osteoinductive cytokines. They uniquely stimulate the differentiation of undifferentiated mesenchymal stem cells into osteoprogenitor cells and mature osteoblasts.

Question 14047

Topic: 1. General Principles & Basic Science
A patient with vascular Ehlers-Danlos syndrome is at high risk for catastrophic arterial or hollow organ rupture. This specific subtype is caused by a genetic mutation affecting which of the following collagen types?
. Type I
. Type II
. Type III
. Type IV
. Type V

Correct Answer & Explanation

. Type III

Explanation

Vascular Ehlers-Danlos syndrome (Type IV EDS) is caused by mutations in the COL3A1 gene, resulting in defective Type III collagen. Type III collagen is critical for the structural integrity of extensible tissues like blood vessels, intestines, and uterus.

Question 14048

Topic: Biomechanics & Biomaterials

When a stainless steel screw is placed through a titanium plate, galvanic corrosion may occur. Which of the following factors primarily determines the rate of this electrochemical degradation?

. The modulus of elasticity of the metals
. The difference in the anodic index between the two metals
. The thickness of the passivation layer on the stainless steel
. The ultimate tensile strength of the titanium
. The degree of cyclic loading applied to the construct

Correct Answer & Explanation

. The difference in the anodic index between the two metals

Explanation

Galvanic corrosion occurs when two dissimilar metals are in contact within an electrolytic environment. The rate and severity of corrosion are driven by the difference in their electrochemical potentials, known as the anodic index.

Question 14049

Topic: 1. General Principles & Basic Science

Osteoclasts utilize which of the following specific enzymes to create an acidic microenvironment and dissolve the inorganic hydroxyapatite mineral of bone?

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

Correct Answer & Explanation

. Carbonic anhydrase II

Explanation

Carbonic anhydrase II catalyzes the formation of hydrogen ions (protons) that are pumped into the ruffled border, creating a low pH environment that dissolves inorganic hydroxyapatite. In contrast, Cathepsin K degrades the organic collagen matrix.

Question 14050

Topic: Physiology & Rehabilitation

Compared to isometric and concentric muscle contractions, what is the biomechanical and metabolic profile of an eccentric muscle contraction?

. Generates the least force and requires the most ATP
. Generates the most force and requires the most ATP
. Generates the most force and requires the least ATP
. Generates less force than concentric but uses more ATP
. Force generation and ATP consumption are equal across all types

Correct Answer & Explanation

. Generates the most force and requires the least ATP

Explanation

Eccentric contractions (muscle lengthening under tension) can generate the highest maximal force of the three contraction types. They also do so more efficiently, consuming the least amount of ATP.

Question 14051

Topic: Biology, Genetics & Bone Healing

Boundary lubrication of articular cartilage is highly dependent on the glycoprotein lubricin (PRG4). Which of the following cells are primarily responsible for synthesizing lubricin?

. Type A synoviocytes and macrophages
. Type B synoviocytes and superficial zone chondrocytes
. Hypertrophic chondrocytes and osteoblasts
. Deep zone chondrocytes and endothelial cells
. Fibroblasts and mast cells

Correct Answer & Explanation

. Type B synoviocytes and superficial zone chondrocytes

Explanation

Lubricin (proteoglycan 4) is primarily synthesized by superficial zone chondrocytes and Type B synoviocytes. It binds to the articular surface to provide boundary lubrication, preventing wear under high-load conditions.

Question 14052

Topic: 1. General Principles & Basic Science
Tranexamic acid (TXA) is frequently used in orthopedic surgery to reduce perioperative blood loss. What is the specific mechanism of action of this medication?
. Directly inhibits Factor Xa
. Irreversibly binds to COX-1 on platelets
. Reversibly blocks the lysine-binding sites on plasminogen
. Activates antithrombin III
. Inhibits the synthesis of Vitamin K-dependent coagulation factors

Correct Answer & Explanation

. Reversibly blocks the lysine-binding sites on plasminogen

Explanation

Tranexamic acid is an antifibrinolytic agent that acts as a synthetic analog of lysine. It reversibly binds to the lysine-binding sites on plasminogen, thereby preventing its conversion to active plasmin and inhibiting fibrin clot degradation.

Question 14053

Topic: Infection, Pharmacology & VTE
Rivaroxaban is an oral anticoagulant increasingly used for DVT prophylaxis following total joint arthroplasty. At which specific point in the coagulation cascade does it exert its primary effect?
. Direct inhibition of Thrombin (Factor IIa)
. Direct inhibition of Factor Xa
. Potentiation of Antithrombin III
. Inhibition of Vitamin K epoxide reductase
. Inhibition of von Willebrand factor cross-linking

Correct Answer & Explanation

. Direct inhibition of Factor Xa

Explanation

Rivaroxaban and Apixaban are direct oral anticoagulants (DOACs) that specifically bind to and inhibit Factor Xa. This interrupts the common pathway of the coagulation cascade, preventing the conversion of prothrombin to thrombin.

Question 14054

Topic: Biology, Genetics & Bone Healing

A 65-year-old female with osteoporosis is started on alendronate. At the cellular level, what is the primary mechanism of action of this nitrogen-containing bisphosphonate?

. Inhibition of RANKL binding to RANK
. Inhibition of farnesyl pyrophosphate synthase
. Direct apoptosis of osteoblasts
. Binding to sclerostin to promote bone formation
. Stimulation of the Wnt/beta-catenin pathway

Correct Answer & Explanation

. Inhibition of farnesyl pyrophosphate synthase

Explanation

Nitrogen-containing bisphosphonates like alendronate inhibit farnesyl pyrophosphate synthase in the mevalonate pathway. This disrupts osteoclast intracellular signaling, leading to osteoclast apoptosis and decreased bone resorption.

Question 14055

Topic: Biomechanics & Biomaterials

A surgeon places a titanium screw through a stainless steel plate during fracture fixation. Which of the following modes of corrosion is most likely to occur at the interface of these two implants?

. Fretting corrosion
. Crevice corrosion
. Galvanic corrosion
. Pitting corrosion
. Fatigue corrosion

Correct Answer & Explanation

. Galvanic corrosion

Explanation

Galvanic corrosion occurs when two dissimilar metals are placed in physical contact within a conductive fluid like body serum. The less noble metal undergoes accelerated corrosion due to an electrochemical electron transfer.

Question 14056

Topic: Physiology & Rehabilitation

During the normal human gait cycle, the gluteus maximus exhibits its peak electromyographic (EMG) activity during which phase?

. Initial contact (heel strike) to loading response
. Mid-stance
. Terminal stance
. Pre-swing
. Initial swing

Correct Answer & Explanation

. Initial contact (heel strike) to loading response

Explanation

The gluteus maximus peaks in activity from initial contact to early loading response. It acts eccentrically to decelerate the forward momentum of the trunk and prevent hip flexion collapse.

Question 14057

Topic: Biomechanics & Biomaterials

A resident is tensioning a hamstring autograft for an ACL reconstruction. They apply a constant load to the graft for 5 minutes and observe that the graft gradually lengthens. Which viscoelastic property does this describe?

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

Correct Answer & Explanation

. Creep

Explanation

Creep is the progressive deformation (lengthening) of a viscoelastic material over time when subjected to a constant load. Stress relaxation, conversely, is the decrease in internal stress over time under a constant strain.

Question 14058

Topic: Biology, Genetics & Bone Healing

A 7-year-old boy presents with bleeding gums, petechiae, and metaphyseal widening on radiographs. A deficiency in which of the following cellular processes is the primary cause of his skeletal abnormalities?

. Mineralization of osteoid by osteoblasts
. Hydroxylation of proline and lysine residues
. Cleavage of procollagen terminals
. Cross-linking of tropocollagen by lysyl oxidase
. Binding of calcium to osteocalcin

Correct Answer & Explanation

. Hydroxylation of proline and lysine residues

Explanation

The patient has scurvy due to severe Vitamin C deficiency. Vitamin C is an essential cofactor for prolyl and lysyl hydroxylase, and its absence prevents the hydroxylation of proline and lysine, leading to unstable collagen triple helices.

Question 14059

Topic: Biology, Genetics & Bone Healing

Demineralized bone matrix (DBM) primarily relies on which of the following to facilitate local bone formation?

. Providing live osteoprogenitor cells
. Providing an osteoconductive scaffold exclusively
. Releasing osteoinductive bone morphogenetic proteins (BMPs)
. Stimulating an immunomodulatory response
. Enhancing immediate structural mechanical support

Correct Answer & Explanation

. Releasing osteoinductive bone morphogenetic proteins (BMPs)

Explanation

DBM is manufactured by removing the mineral content of allograft bone, which exposes the underlying osteoinductive proteins, particularly BMPs. It lacks structural strength and contains no viable osteogenic cells.

Question 14060

Topic: Infection, Pharmacology & VTE
A patient undergoing total knee arthroplasty is prescribed apixaban for VTE prophylaxis. Which step in the coagulation cascade is directly inhibited by this medication?
. Conversion of fibrinogen to fibrin
. Activation of antithrombin III
. Factor Xa
. Vitamin K epoxide reductase
. Direct inhibition of thrombin (Factor IIa)

Correct Answer & Explanation

. Factor Xa

Explanation

Apixaban and rivaroxaban are direct, highly selective, and reversible inhibitors of Factor Xa. They block the conversion of prothrombin to thrombin without requiring antithrombin III as a mediator.

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