Menu

1. General Principles & Basic Science MCQs

Practice Set 300 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 5981

Topic: Biomechanics & Biomaterials

A patellar tendon graft is used for ACL reconstruction and is tensioned on the back table. Over time, while held at a constant tension, the graft gradually elongates. Which biomechanical property does this describe?

. Stress relaxation
. Creep
. Hysteresis
. Isotropy
. Fatigue failure

Correct Answer & Explanation

. Creep

Explanation

Creep is the progressive deformation (elongation) of a viscoelastic material when subjected to a constant load or tension over time. Stress relaxation, conversely, is the decrease in stress over time when the material is held at a constant length.

Question 5982

Topic: 1. General Principles & Basic Science
Tranexamic acid (TXA) is widely used in orthopedic surgery to reduce perioperative blood loss. What is the precise mechanism of action of TXA?
. Direct inhibition of Factor Xa
. Irreversible inhibition of cyclooxygenase
. Competitive inhibition of plasminogen activation to plasmin
. Enhancement of antithrombin III activity
. Promotion of platelet aggregation at the injury site

Correct Answer & Explanation

. Competitive inhibition of plasminogen activation to plasmin

Explanation

TXA is a synthetic lysine analog that competitively binds to the lysine-binding sites on plasminogen. This prevents plasminogen from converting to plasmin, thereby inhibiting the degradation of fibrin clots.

Question 5983

Topic: Biology, Genetics & Bone Healing

Recombinant human Bone Morphogenetic Protein-2 (rhBMP-2) is utilized in spinal fusions to induce osteoinduction. The intracellular signaling pathway activated by BMP-2 binding to its serine/threonine kinase receptor is primarily mediated by which of the following?

. Wnt/beta-catenin
. JAK/STAT
. Smad 1/5/8
. MAPK/ERK
. cAMP/PKA

Correct Answer & Explanation

. Smad 1/5/8

Explanation

BMPs bind to cell surface receptors that phosphorylate receptor-regulated Smads, specifically Smad 1, 5, and 8. These complex with Smad 4, translocate to the nucleus, and upregulate the transcription of osteogenic genes like Runx2.

Question 5984

Topic: 1. General Principles & Basic Science

A surgeon is evaluating the pullout strength of various cortical screws for rigid internal fixation. Which of the following geometric modifications to a screw will yield the greatest increase in pullout strength?

. Decreasing the major (outer) diameter
. Increasing the major (outer) diameter
. Increasing the minor (inner) diameter
. Increasing the pitch
. Decreasing the length of engagement

Correct Answer & Explanation

. Increasing the major (outer) diameter

Explanation

Pullout strength is directly proportional to the outer (major) diameter of the screw, the length of engagement in the bone, and the shear strength of the bone material. Increasing the major diameter most significantly increases pullout resistance.

Question 5985

Topic: 1. General Principles & Basic Science

Articular cartilage relies on its distinct zones to resist mechanical forces. Which zone contains collagen fibers oriented parallel to the articular surface, providing the highest resistance to shear stress?

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

Correct Answer & Explanation

. Superficial (tangential) zone

Explanation

The superficial zone of articular cartilage is composed of densely packed collagen fibers oriented parallel to the joint surface. This specific orientation provides the tissue with its ability to resist high shear forces during joint motion.

Question 5986

Topic: Biology, Genetics & Bone Healing

Nitrogen-containing bisphosphonates, such as alendronate, are a first-line treatment for osteoporosis. They cause osteoclast apoptosis by inhibiting which specific enzyme in the mevalonate pathway?

. HMG-CoA reductase
. Farnesyl pyrophosphate (FPP) synthase
. Carbonic anhydrase II
. Cathepsin K
. Tartrate-resistant acid phosphatase (TRAP)

Correct Answer & Explanation

. Farnesyl pyrophosphate (FPP) synthase

Explanation

Nitrogen-containing bisphosphonates inhibit farnesyl pyrophosphate (FPP) synthase in the mevalonate pathway. This prevents the prenylation of small GTPase proteins (like Ras and Rho), leading to osteoclast dysfunction and apoptosis.

Question 5987

Topic: Biomechanics & Biomaterials
Highly cross-linked ultra-high-molecular-weight polyethylene (UHMWPE) was developed to improve the longevity of total hip arthroplasty (THA). The primary advantage of cross-linking is the reduction of which type of wear?
. Fatigue wear
. Abrasive and adhesive wear
. Corrosive wear
. Third-body wear
. Galvanic wear

Correct Answer & Explanation

. Abrasive and adhesive wear

Explanation

Cross-linking UHMWPE significantly increases its resistance to adhesive and abrasive wear, which are the main modes of wear generating osteolytic particles in THA. However, highly cross-linked polyethylene has reduced mechanical properties, making it more susceptible to fatigue wear.

Question 5988

Topic: Infection, Pharmacology & VTE
A patient is prescribed rivaroxaban for DVT prophylaxis following a total knee arthroplasty. What is the mechanism of action of this pharmacological agent?
. Directly inhibits thrombin (Factor IIa)
. Directly inhibits Factor Xa
. Binds to antithrombin III to inhibit Factor Xa
. Inhibits vitamin K epoxide reductase
. Inhibits ADP binding to the P2Y12 receptor

Correct Answer & Explanation

. Directly inhibits Factor Xa

Explanation

Rivaroxaban and apixaban are direct oral anticoagulants that work by specifically and reversibly binding to and inhibiting free and clot-bound Factor Xa. Unlike heparin, they do not require antithrombin III to exert their effect.

Question 5989

Topic: Biology, Genetics & Bone Healing

During embryonic skeletal development and fracture repair, multipotent mesenchymal stem cells must commit to the osteoblastic lineage. Which of the following transcription factors is the master regulator for osteoblast differentiation?

. Sox9
. Runx2 (Cbfa1)
. MyoD
. PPAR-gamma
. HIF-1 alpha

Correct Answer & Explanation

. Runx2 (Cbfa1)

Explanation

Runx2 (also known as Cbfa1) is the essential transcription factor required for mesenchymal stem cells to differentiate into osteoblasts. A deficiency or mutation in Runx2 leads to cleidocranial dysplasia and absent bone formation.

Question 5990

Topic: Biology, Genetics & Bone Healing

According to Perren's strain theory of fracture healing, the tissue that forms at a fracture site is dictated by the amount of interfragmentary strain. If the local mechanical strain is between 2% and 10%, which type of tissue will predominantly form?

. Lamellar bone (primary healing)
. Granulation tissue
. Fibrocartilage (callus)
. Woven bone
. Hyaline cartilage

Correct Answer & Explanation

. Woven bone

Explanation

Perren's strain theory states that tissues tolerate specific levels of strain before rupturing. Granulation tissue tolerates up to 100% strain, fibrocartilage tolerates 2-10% strain, and bone forms only when the strain is less than 2%.

Question 5991

Topic: Biology, Genetics & Bone Healing

Romosozumab is an anabolic pharmacological agent used to treat severe osteoporosis. It exerts its effect by binding to and inhibiting a specific glycoprotein, thereby activating the Wnt signaling pathway. What is the target of romosozumab?

. Sclerostin
. RANKL
. Dickkopf-1 (Dkk-1)
. Parathyroid hormone (PTH)
. Cathepsin K

Correct Answer & Explanation

. Sclerostin

Explanation

Romosozumab is a monoclonal antibody that binds to and inhibits sclerostin, a glycoprotein produced by osteocytes that normally downregulates bone formation. Inhibiting sclerostin releases the block on the Wnt/beta-catenin pathway, promoting robust osteoblast activity.

Question 5992

Topic: Biomechanics & Biomaterials

Mixing stainless steel and titanium implants within the same surgical construct can lead to galvanic corrosion. In this scenario, what happens to the stainless steel component?

. It acts as the cathode and undergoes rapid oxidation
. It acts as the anode and undergoes accelerated corrosion
. It forms a protective passivation layer of chromium oxide
. It undergoes fretting wear but not electrochemical corrosion
. It transfers electrons directly to the titanium, preventing ion release

Correct Answer & Explanation

. It acts as the anode and undergoes accelerated corrosion

Explanation

In a galvanic couple between stainless steel and titanium, titanium is more noble (cathodic) and stainless steel is less noble (anodic). The anodic stainless steel will preferentially lose electrons and undergo accelerated corrosion.

Question 5993

Topic: 1. General Principles & Basic Science
Tendon healing occurs in three distinct phases: inflammatory, proliferative, and remodeling. During the remodeling phase, what is the most significant change in the collagen composition of the extracellular matrix?
. Replacement of Type I collagen with Type II collagen
. Replacement of Type II collagen with Type I collagen
. Replacement of Type III collagen with Type I collagen
. Replacement of Type I collagen with Type III collagen
. Replacement of Type IX collagen with Type I collagen

Correct Answer & Explanation

. Replacement of Type III collagen with Type I collagen

Explanation

During the initial proliferative phase of tendon healing, fibroblasts rapidly synthesize Type III collagen, which forms disorganized scar tissue. In the remodeling phase, this is gradually replaced by stronger, longitudinally aligned Type I collagen.

Question 5994

Topic: Biomechanics & Biomaterials

A researcher is studying the mechanical properties of different orthopedic materials compared to human cortical bone. Which of the following implant materials possesses a Young's modulus (modulus of elasticity) that is closest to that of cortical bone?

. Cobalt-chromium alloy
. 316L Stainless steel
. Titanium alloy (Ti-6Al-4V)
. Tantalum
. Alumina ceramic

Correct Answer & Explanation

. Titanium alloy (Ti-6Al-4V)

Explanation

Cortical bone has a Young's modulus of roughly 15-20 GPa. Titanium alloys have a modulus of around 100-110 GPa, which is much closer to cortical bone than stainless steel (approx. 200 GPa) or cobalt-chromium (approx. 240 GPa), reducing the risk of stress shielding.

Question 5995

Topic: Infection, Pharmacology & VTE

During a massive rotator cuff repair, a patient receives an interscalene block and subsequently develops seizures followed by cardiac arrest. The anesthesiologist diagnoses severe bupivacaine toxicity. What is the most appropriate specific treatment to reverse the cardiotoxicity?

. Intravenous epinephrine push
. Intravenous 20% lipid emulsion
. High-dose intravenous naloxone
. Intravenous calcium gluconate
. Intravenous flumazenil

Correct Answer & Explanation

. Intravenous 20% lipid emulsion

Explanation

Bupivacaine is highly lipophilic and can cause catastrophic, refractory cardiac arrhythmias if injected intravascularly. Intravenous 20% lipid emulsion therapy is the standard of care to create a "lipid sink" that rapidly extracts the local anesthetic from the myocardial tissues.

Question 5996

Topic: 1. General Principles & Basic Science

Nonsteroidal anti-inflammatory drugs (NSAIDs) are often avoided in the acute phase of fracture healing due to concerns about nonunion. What is the specific cellular mechanism by which NSAID use impairs fracture healing?

. Inhibition of osteoclast apoptosis
. Inhibition of cyclooxygenase-2 (COX-2) mediated prostaglandin synthesis
. Downregulation of BMP-2 receptor expression on osteoblasts
. Direct toxicity to mesenchymal stem cells
. Premature calcification of the fracture hematoma

Correct Answer & Explanation

. Inhibition of cyclooxygenase-2 (COX-2) mediated prostaglandin synthesis

Explanation

NSAIDs inhibit cyclooxygenase enzymes, specifically COX-2, which is required for the synthesis of prostaglandins (like PGE2) at the fracture site. PGE2 is critical for initiating the inflammatory cascade, angiogenesis, and subsequent enchondral ossification.

Question 5997

Topic: Biology, Genetics & Bone Healing

A 65-year-old woman with severe osteoporosis is started on romosozumab, a monoclonal antibody that binds to sclerostin. What is the primary downstream effect of this medication on bone metabolism?

. Inhibition of the RANKL pathway leading to osteoclast apoptosis
. Increased accumulation of intracellular beta-catenin in osteoblasts
. Direct inhibition of cathepsin K in the Howship lacuna
. Stimulation of calcium-sensing receptors on the parathyroid gland
. Inhibition of bone morphogenetic protein (BMP) signaling

Correct Answer & Explanation

. Increased accumulation of intracellular beta-catenin in osteoblasts

Explanation

Sclerostin normally inhibits the Wnt signaling pathway by binding to LRP5/6 receptors. Blocking sclerostin allows Wnt signaling to proceed, leading to beta-catenin accumulation, which promotes osteoblast differentiation and bone formation.

Question 5998

Topic: 1. General Principles & Basic Science

An orthopedic surgeon is designing a new cortical screw to be used in diaphyseal bone. To maximize the pullout strength of the screw, which of the following geometric modifications should be made?

. Decrease the outer diameter of the screw
. Increase the inner (root) diameter of the screw
. Decrease the thread pitch
. Increase the length of the unthreaded shaft
. Increase the thread pitch

Correct Answer & Explanation

. Decrease the thread pitch

Explanation

Pullout strength is directly proportional to the outer diameter and length of thread engagement, and inversely proportional to the thread pitch. Decreasing the thread pitch increases the number of threads engaged in the cortical bone, thereby increasing pullout strength.

Question 5999

Topic: 1. General Principles & Basic Science
A 55-year-old man undergoes a total knee arthroplasty. To minimize perioperative blood loss, intravenous tranexamic acid (TXA) is administered. What is the primary mechanism of action of this agent?
. Irreversible inhibition of cyclooxygenase
. Competitive inhibition of plasminogen activation
. Direct inhibition of Factor Xa
. Activation of antithrombin III
. Inhibition of ADP-induced platelet aggregation

Correct Answer & Explanation

. Competitive inhibition of plasminogen activation

Explanation

TXA is a synthetic analog of the amino acid lysine that reversibly binds to the lysine receptor sites on plasminogen. This competitively inhibits the activation of plasminogen to plasmin, thereby preventing the degradation of fibrin clots.

Question 6000

Topic: Biomechanics & Biomaterials

During an anterior cruciate ligament reconstruction, the surgeon pulls the soft-tissue graft under a constant load for several minutes before final fixation. The graft gradually lengthens during this period. Which viscoelastic property does this demonstrate?

. Stress relaxation
. Creep
. Hysteresis
. Fatigue failure
. Isotropic deformation

Correct Answer & Explanation

. Creep

Explanation

Creep is the progressive deformation (lengthening) of a viscoelastic material when it is subjected to a constant load over time. Conversely, stress relaxation is the decrease in stress over time when a material is held at a constant length.

Test Yourself

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

On this Page