Menu

1. General Principles & Basic Science MCQs

Practice Set 720 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 14381

Topic: Surgical Anatomy & Approaches

During an ilioinguinal approach for an acetabular fracture, severe hemorrhage occurs over the superior pubic ramus. This bleeding is most likely originating from an anastomosis between the obturator vessels and which of the following?

. Internal pudendal vessels
. External iliac or inferior epigastric vessels
. Superior gluteal vessels
. Internal iliac vessels
. Femoral vessels

Correct Answer & Explanation

. External iliac or inferior epigastric vessels

Explanation

The 'corona mortis' is a vascular anastomosis between the obturator and external iliac (or inferior epigastric) systems. It crosses the superior pubic ramus and is highly susceptible to iatrogenic injury during anterior pelvic approaches.

Question 14382

Topic: Biomechanics & Biomaterials
Increasing the radiation cross-linking of ultra-high molecular weight polyethylene (UHMWPE) used in total joint arthroplasty has which of the following biomechanical effects?
. Increases fatigue resistance
. Increases ductility
. Decreases wear resistance
. Decreases fracture toughness
. Increases ultimate tensile strength

Correct Answer & Explanation

. Decreases fracture toughness

Explanation

Highly cross-linked polyethylene significantly decreases volumetric wear but at the cost of decreasing fracture toughness, ductility, and fatigue resistance. This makes it more susceptible to rim fractures under certain loading conditions.

Question 14383

Topic: Biology, Genetics & Bone Healing

Which of the following is the primary mechanism of action of Teriparatide in the treatment of osteoporosis?

. Inhibition of osteoclast RANKL binding
. Activation of the Wnt/beta-catenin pathway via sclerostin inhibition
. Direct stimulation of osteoblast activity via intermittent PTH receptor activation
. Inhibition of cathepsin K
. Incorporation into bone matrix to induce osteoclast apoptosis

Correct Answer & Explanation

. Direct stimulation of osteoblast activity via intermittent PTH receptor activation

Explanation

Teriparatide is a recombinant human parathyroid hormone (PTH 1-34) analog. When administered intermittently, it exerts an anabolic effect by directly stimulating osteoblast activity and new bone formation.

Question 14384

Topic: 1. General Principles & Basic Science

In articular cartilage, which layer is characterized by the highest concentration of collagen fibers arranged parallel to the joint surface to resist shear stress?

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

Correct Answer & Explanation

. Superficial (tangential) zone

Explanation

The superficial (tangential) zone of articular cartilage has densely packed collagen fibrils oriented parallel to the articular surface. This unique arrangement primarily functions to resist high shear stresses during joint motion.

Question 14385

Topic: Biomechanics & Biomaterials

When comparing titanium alloy (Ti-6Al-4V) to stainless steel (316L) for orthopedic implants, which biomechanical property of titanium provides a more favorable stress transfer to surrounding bone?

. Higher ultimate tensile strength
. Lower modulus of elasticity
. Higher yield strength
. Greater ductility
. Increased galvanic corrosion

Correct Answer & Explanation

. Lower modulus of elasticity

Explanation

Titanium alloy has a significantly lower modulus of elasticity compared to stainless steel, making it much closer to the modulus of cortical bone. This reduces stress shielding and promotes better load sharing with the surrounding bone.

Question 14386

Topic: Surgical Anatomy & Approaches

During a standard anterior (Smith-Petersen) approach to the hip, the internervous plane lies between muscles innervated by which of the following pairs of nerves?

. Femoral nerve and Superior gluteal nerve
. Superior gluteal nerve and Inferior gluteal nerve
. Obturator nerve and Sciatic nerve
. Femoral nerve and Obturator nerve
. Sciatic nerve and Superior gluteal nerve

Correct Answer & Explanation

. Femoral nerve and Superior gluteal nerve

Explanation

The Smith-Petersen approach utilizes the true internervous plane between the sartorius (femoral nerve) and the tensor fasciae latae (superior gluteal nerve) superficially, and the rectus femoris (femoral nerve) and gluteus medius (superior gluteal nerve) deep.

Question 14387

Topic: Biology, Genetics & Bone Healing

A 65-year-old female sustains a subtrochanteric femur fracture after a minor fall. She has a 10-year history of alendronate use. What is the primary mechanism of action of this medication?

. Inhibition of RANKL
. Inhibition of farnesyl pyrophosphate synthase
. Stimulation of Wnt signaling
. Decoy receptor for RANK
. Direct inhibition of cathepsin K

Correct Answer & Explanation

. Inhibition of farnesyl pyrophosphate synthase

Explanation

Nitrogen-containing bisphosphonates like alendronate inhibit farnesyl pyrophosphate synthase within the mevalonate pathway. This disruption causes osteoclast apoptosis and prevents bone resorption.

Question 14388

Topic: Biology, Genetics & Bone Healing

According to Perren's strain theory, what is the maximum amount of interfragmentary strain compatible with the formation of woven bone during secondary fracture healing?

. 1%
. 2%
. 10%
. 30%
. 100%

Correct Answer & Explanation

. 2%

Explanation

Perren's strain theory dictates that lamellar bone forms at <2% strain, and woven bone forms at 2-10% strain. Granulation tissue is required to tolerate high strains (up to 100%) before it differentiates into stiffer tissues.

Question 14389

Topic: Infection, Pharmacology & VTE
A 70-year-old patient scheduled for elective total knee arthroplasty takes rivaroxaban for atrial fibrillation. What is the precise mechanism of action of this medication?
. Direct thrombin inhibitor
. Vitamin K epoxide reductase inhibitor
. Direct Factor Xa inhibitor
. Antithrombin III activator
. ADP receptor antagonist

Correct Answer & Explanation

. Direct Factor Xa inhibitor

Explanation

Rivaroxaban and apixaban are direct Factor Xa inhibitors, which block the convergence point of the intrinsic and extrinsic coagulation pathways. Dabigatran, in contrast, is a direct thrombin (Factor IIa) inhibitor.

Question 14390

Topic: Biology, Genetics & Bone Healing

A 68-year-old female taking denosumab for osteoporosis is planned for an elective lumbar fusion. What is the mechanism of action of her osteoporosis medication?

. Inhibits osteoblast apoptosis
. Binds to and neutralizes RANKL
. Inhibits the mevalonate pathway
. Acts as an agonist at the estrogen receptor
. Directly inhibits cathepsin K

Correct Answer & Explanation

. Binds to and neutralizes RANKL

Explanation

Denosumab is a monoclonal antibody that binds directly to RANKL. This prevents RANKL from binding to the RANK receptor on osteoclasts, profoundly inhibiting osteoclast formation and bone resorption.

Question 14391

Topic: Physiology & Rehabilitation

During a drop jump exercise, the quadriceps muscle actively resists gravity to decelerate the body. What type of muscle contraction is occurring in the quadriceps?

. Isokinetic
. Isometric
. Concentric
. Eccentric
. Plyometric

Correct Answer & Explanation

. Eccentric

Explanation

An eccentric contraction occurs when a muscle generates force while actively lengthening to decelerate a joint. Eccentric contractions generate the highest peak forces and are heavily implicated in muscle strain injuries.

Question 14392

Topic: Surgical Anatomy & Approaches

A patient with a closed humeral shaft fracture develops a radial nerve palsy. An EMG at 3 weeks shows fibrillation potentials in the brachioradialis but no voluntary motor unit action potentials. This indicates at least what degree of nerve injury according to Sunderland's classification?

. First-degree (Neurapraxia)
. Second-degree (Axonotmesis)
. Third-degree
. Fourth-degree
. Fifth-degree (Neurotmesis)

Correct Answer & Explanation

. Second-degree (Axonotmesis)

Explanation

Fibrillation potentials indicate denervation resulting from Wallerian degeneration. This implies at least a second-degree injury (axonotmesis), differentiating it from a first-degree injury (neurapraxia) which involves only focal demyelination without axonal loss.

Question 14393

Topic: 1. General Principles & Basic Science

Which of the following phases of creeping substitution occurs first following the placement of a cancellous bone autograft?

. Osteoblastic apposition
. Inflammation
. Revascularization
. Osteoclastic resorption
. Woven bone remodeling

Correct Answer & Explanation

. Inflammation

Explanation

The stages of creeping substitution for a cancellous graft occur in a specific order: inflammation, revascularization, osteoinduction/osteoconduction, and remodeling. Inflammation is the immediate first response driven by surgical trauma and hematoma formation.

Question 14394

Topic: 1. General Principles & Basic Science

In normal adult articular cartilage, which zone is characterized by the highest concentration of water and the lowest concentration of proteoglycans?

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

Correct Answer & Explanation

. Superficial (tangential) zone

Explanation

The superficial zone contains the highest water content (up to 80%) and collagen fibrils aligned parallel to the joint surface to resist shear stress. It also has the lowest concentration of proteoglycans compared to deeper zones.

Question 14395

Topic: Infection, Pharmacology & VTE

Bacterial biofilms make the eradication of prosthetic joint infections highly challenging. Which initial phase of biofilm development involves the reversible attachment of planktonic bacteria to the implant surface?

. Maturation
. Dispersion
. Adhesion
. Microcolony formation
. Quorum sensing

Correct Answer & Explanation

. Adhesion

Explanation

Biofilm formation begins with adhesion, a reversible attachment of planktonic bacteria to a surface via van der Waals forces. This is followed by irreversible attachment, microcolony formation, maturation, and eventual dispersion.

Question 14396

Topic: Biomechanics & Biomaterials

A surgeon incorrectly uses a stainless steel screw to secure a titanium alloy plate during fracture fixation. Which type of corrosion is most likely to occur at the screw-plate interface?

. Fretting corrosion
. Crevice corrosion
. Galvanic corrosion
. Pitting corrosion
. Intergranular corrosion

Correct Answer & Explanation

. Galvanic corrosion

Explanation

Galvanic corrosion occurs when two electrochemically dissimilar metals are placed in direct contact within an electrolytic medium like bodily fluids. The less noble metal acts as an anode and undergoes accelerated corrosion.

Question 14397

Topic: 1. General Principles & Basic Science

Tranexamic acid (TXA) is widely utilized in orthopedic surgery to reduce perioperative blood loss. What is its specific molecular mechanism of action?

. Activates the extrinsic coagulation cascade
. Competitively inhibits plasminogen activation
. Directly cross-links fibrin polymers
. Inhibits cyclooxygenase-1 in platelets
. Stimulates release of von Willebrand factor

Correct Answer & Explanation

. Competitively inhibits plasminogen activation

Explanation

TXA is a synthetic analog of the amino acid lysine. It reversibly binds to the lysine-binding sites on plasminogen, preventing its activation to plasmin and effectively inhibiting fibrinolysis.

Question 14398

Topic: 1. General Principles & Basic Science

A patient undergoing a minor orthopedic procedure under local anesthesia with bupivacaine acutely develops perioral numbness, tinnitus, and subsequent seizures. What is the most appropriate initial specific antidote?

. Flumazenil
. Naloxone
. 20% Intravenous lipid emulsion
. Intravenous calcium gluconate
. Neostigmine

Correct Answer & Explanation

. 20% Intravenous lipid emulsion

Explanation

The patient is exhibiting signs of Local Anesthetic Systemic Toxicity (LAST). The specific and life-saving antidote is 20% intravenous lipid emulsion, which acts as a "lipid sink" to bind the highly lipophilic bupivacaine molecules.

Question 14399

Topic: 1. General Principles & Basic Science

Which of the following vitamins is absolutely essential for the gamma-carboxylation of osteocalcin, allowing it to bind properly to calcium in the bone matrix?

. Vitamin A
. Vitamin C
. Vitamin D
. Vitamin K
. Vitamin E

Correct Answer & Explanation

. Vitamin K

Explanation

Vitamin K acts as an essential cofactor for the gamma-carboxylation of glutamic acid residues on osteocalcin. This post-translational modification is required for osteocalcin to effectively bind to calcium and hydroxyapatite.

Question 14400

Topic: Biology, Genetics & Bone Healing

Demineralized bone matrix (DBM) products are commonly used in orthopedic bone grafting. Which of the following best describes the biologic properties of pure DBM?

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

Correct Answer & Explanation

. Osteoconductive and osteoinductive

Explanation

DBM provides a type I collagen scaffold (osteoconductive) and retains growth factors like BMPs (osteoinductive). Because the processing removes living cells, DBM possesses no osteogenic properties.

Test Yourself

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

On this Page