Menu

1. General Principles & Basic Science MCQs

Practice Set 722 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 14421

Topic: 1. General Principles & Basic Science

Which of the following geometric modifications to a standard cortical screw design would most effectively increase its pullout strength from bone?

. Decreasing the outer diameter
. Increasing the core diameter
. Increasing the outer diameter
. Increasing the pitch distance
. Using a cannulated rather than solid design

Correct Answer & Explanation

. Increasing the outer diameter

Explanation

The pullout strength of a screw is most significantly influenced by its outer (thread) diameter. Increasing the outer diameter, decreasing the core diameter, and decreasing the pitch (resulting in more threads per inch) all increase overall pullout strength.

Question 14422

Topic: 1. General Principles & Basic Science

A peripheral nerve injury is classified as Sunderland third-degree. Which of the following neural anatomical structures remains intact?

. Axon
. Myelin sheath
. Endoneurium
. Perineurium
. No neural structures remain intact

Correct Answer & Explanation

. Perineurium

Explanation

In a Sunderland third-degree injury, the axon, myelin sheath, and endoneurium are completely disrupted, but the perineurium and epineurium remain intact. A second-degree injury (axonotmesis) would additionally preserve the endoneurium.

Question 14423

Topic: Biomechanics & Biomaterials

Among commonly used metallic orthopedic implants, which material possesses a modulus of elasticity most closely resembling that of human cortical bone?

. Stainless steel
. Cobalt-chromium alloy
. Titanium alloy
. Tantalum
. Nitinol

Correct Answer & Explanation

. Titanium alloy

Explanation

Titanium alloys have a modulus of elasticity (approximately 110 GPa) that is significantly closer to that of cortical bone (15-20 GPa) than stainless steel (approx. 200 GPa) or cobalt-chromium (approx. 220 GPa). This helps to minimize the negative biomechanical effects of stress shielding.

Question 14424

Topic: 1. General Principles & Basic Science

Tranexamic acid (TXA) is frequently utilized in orthopedic surgery to mitigate intraoperative blood loss. What is its precise mechanism of action?

. Directly inhibits thrombin formation
. Activates factor Xa in the coagulation cascade
. Competitively inhibits plasminogen activation
. Promotes platelet aggregation via ADP receptor agonism
. Irreversibly inhibits cyclooxygenase-1

Correct Answer & Explanation

. Competitively inhibits plasminogen activation

Explanation

TXA is a synthetic analog of the amino acid lysine. It competitively inhibits the activation of plasminogen to plasmin, thereby preventing the premature degradation of fibrin clots (anti-fibrinolysis).

Question 14425

Topic: Biology, Genetics & Bone Healing

The direct (primary) healing of a fracture requires rigid fixation and absolute stability. Which of the following conditions is an absolute requirement for primary bone healing to occur?

. Endochondral ossification
. Robust cartilaginous callus formation
. Interfragmentary gap of less than 0.1 mm
. Motion allowing 2-10% strain at the fracture site
. High oxygen tension allowing a cartilage template to form

Correct Answer & Explanation

. Interfragmentary gap of less than 0.1 mm

Explanation

Primary bone healing via Haversian remodeling (cutting cones) requires absolute mechanical stability and direct bone contact with a gap of less than 0.1 mm and <2% interfragmentary strain. It completely bypasses the intermediate stages of callus formation and endochondral ossification.

Question 14426

Topic: 1. General Principles & Basic Science

Synovial fluid is analyzed from a patient presenting with an acutely swollen and painful knee. Which of the following laboratory profiles is most highly specific for an acute bacterial septic joint?

. WBC 10,000 cells/mm3 with 50% polymorphonuclear cells
. WBC 25,000 cells/mm3 with 60% polymorphonuclear cells
. WBC 75,000 cells/mm3 with 95% polymorphonuclear cells
. WBC 5,000 cells/mm3 with a highly positive string sign
. Presence of positively birefringent rhomboid crystals

Correct Answer & Explanation

. WBC 75,000 cells/mm3 with 95% polymorphonuclear cells

Explanation

A synovial fluid WBC count exceeding 50,000 cells/mm3 with a polymorphonuclear (PMN) cell predominance of >90% is highly suggestive of a bacterial septic joint. Inflammatory (non-infectious) arthropathies typically present with lower WBC counts and lower PMN percentages.

Question 14427

Topic: Biology, Genetics & Bone Healing

Which specific histological zone of a direct tendon enthesis serves as a mechanical buffer to smoothly transfer stress from the flexible tendon to the rigid bone?

. Parallel collagen fibers
. Uncalcified fibrocartilage
. Calcified fibrocartilage
. Woven bone
. Tidemark

Correct Answer & Explanation

. Uncalcified fibrocartilage

Explanation

A direct enthesis transitions through four distinct zones: tendon, uncalcified fibrocartilage, calcified fibrocartilage, and bone. The uncalcified fibrocartilage zone is crucial for providing a gradual transition in mechanical stiffness, thereby dissipating stress and preventing avulsion failure.

Question 14428

Topic: Biology, Genetics & Bone Healing

Denosumab is effectively utilized in the management of osteoporosis and giant cell tumors of bone. It functions as a targeted monoclonal antibody that directly binds and inhibits which of the following?

. Osteoprotegerin (OPG)
. Receptor activator of nuclear factor kappa-B ligand (RANKL)
. Sclerostin
. Parathyroid hormone (PTH) receptors
. Transforming growth factor beta (TGF-b)

Correct Answer & Explanation

. Receptor activator of nuclear factor kappa-B ligand (RANKL)

Explanation

Denosumab is a fully human monoclonal antibody that binds directly to and neutralizes RANKL. By preventing RANKL from binding to its receptor (RANK) on osteoclasts, it halts osteoclast maturation, function, and survival.

Question 14429

Topic: Physiology & Rehabilitation

Which of the following physiological characteristics is most strongly associated with Type I (slow-twitch) muscle fibers?

. Anaerobic glycolysis metabolism
. Rapid rate of fatigue
. High concentration of myoglobin and mitochondria
. Large motor neuron size
. Low capillary density

Correct Answer & Explanation

. High concentration of myoglobin and mitochondria

Explanation

Type I muscle fibers are "slow-twitch" and optimized for prolonged, aerobic endurance activities. To support oxidative metabolism, they inherently contain high concentrations of mitochondria and myoglobin, along with an extensive capillary network.

Question 14430

Topic: Biology, Genetics & Bone Healing

During the initial phase of distraction osteogenesis (Ilizarov technique), how long is the typical "latency period" maintained before the distraction phase begins?

. 0-1 days
. 5-7 days
. 14-21 days
. 4-6 weeks
. 8-12 weeks

Correct Answer & Explanation

. 5-7 days

Explanation

The latency period in distraction osteogenesis typically lasts 5-7 days immediately following the osteotomy. This purposeful delay allows a reparative fibrovascular callus to form, which is subsequently organized into woven bone during the active distraction phase.

Question 14431

Topic: Biomechanics & Biomaterials

A bone-patellar tendon-bone graft is tensioned and fixed during an anterior cruciate ligament reconstruction. Over the next 10 minutes, the surgeon notes that the tension in the graft steadily decreases despite the length remaining perfectly constant. Which of the following viscoelastic properties does this describe?

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

Correct Answer & Explanation

. Stress relaxation

Explanation

Stress relaxation is the decrease in stress (or tension) over time when a viscoelastic material is held at a constant strain (length). Creep, by contrast, is the increase in strain (length) over time when held at a constant stress (load).

Question 14432

Topic: Biology, Genetics & Bone Healing

Which of the following best describes the biological process by which a massive structural cortical bone allograft is incorporated into the host bone?

. Osteoinduction
. Osteogenesis
. Creeping substitution
. Endochondral ossification
. Intramembranous ossification

Correct Answer & Explanation

. Creeping substitution

Explanation

Structural allografts incorporate via creeping substitution, where host osteoclasts resorb the dead graft bone and osteoblasts lay down new woven bone in its place. This process is slow, occurs entirely via the host's cellular machinery, and is often incomplete in massive cortical allografts.

Question 14433

Topic: 1. General Principles & Basic Science

A patient sustains a mid-shaft humerus fracture and presents with a dense radial nerve palsy. Assuming the nerve has undergone axonotmesis, what is the expected approximate rate of axonal regeneration after the initial latent period and Wallerian degeneration?

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

Correct Answer & Explanation

. 1 mm/day

Explanation

Following Wallerian degeneration of the distal segment, regenerating axons advance at a rate of approximately 1 mm per day (or 1 inch per month). This is a critical basic science principle for predicting the timeline of clinical recovery and planning surgical interventions.

Question 14434

Topic: Biomechanics & Biomaterials
A surgeon is selecting an intramedullary nail for a tibial shaft fracture and wishes to minimize stress shielding of the diaphyseal bone. Which of the following orthopedic implant materials has a modulus of elasticity that most closely approximates that of cortical bone?
. Stainless steel
. Cobalt-chromium alloy
. Titanium alloy
. Polymethylmethacrylate (PMMA)
. Ultra-high-molecular-weight polyethylene (UHMWPE)

Correct Answer & Explanation

. Titanium alloy

Explanation

Titanium alloy has a modulus of elasticity closer to that of cortical bone compared to stiffer metals like stainless steel or cobalt-chromium. This lower stiffness reduces stress shielding and promotes better load sharing with the healing host bone.

Question 14435

Topic: Biology, Genetics & Bone Healing

Recombinant human bone morphogenetic protein-2 (rhBMP-2) is utilized off-label to enhance bone healing in specific nonunions. Binding of BMP-2 to its transmembrane serine/threonine kinase receptor primarily activates which of the following intracellular signaling pathways?

. JAK-STAT pathway
. Wnt/beta-catenin pathway
. MAP kinase pathway
. Smad pathway
. Notch signaling pathway

Correct Answer & Explanation

. Smad pathway

Explanation

BMPs are members of the TGF-beta superfamily and exert their cellular effects primarily through the canonical Smad intracellular signaling pathway. Once phosphorylated by the receptor, Smad complexes translocate to the nucleus to drive transcription of osteogenic genes.

Question 14436

Topic: Biology, Genetics & Bone Healing

A 72-year-old female with severe osteoporosis is treated with denosumab to reduce her fracture risk. Which of the following best describes the mechanism of action of this medication?

. It directly inhibits osteoclast farnesyl pyrophosphate synthase
. It is a monoclonal antibody that binds and neutralizes RANK ligand
. It stimulates the Wnt signaling pathway via sclerostin inhibition
. It acts as a selective estrogen receptor modulator
. It provides intermittent parathyroid hormone receptor stimulation

Correct Answer & Explanation

. It is a monoclonal antibody that binds and neutralizes RANK ligand

Explanation

Denosumab is a fully human monoclonal antibody that binds directly to RANKL (Receptor Activator of Nuclear factor Kappa-B Ligand). This prevents RANKL from binding to the RANK receptor on osteoclasts, thereby potently inhibiting osteoclast formation, function, and survival.

Question 14437

Topic: 1. General Principles & Basic Science

Accidental intravascular injection of bupivacaine during a regional nerve block can lead to severe and refractory cardiac toxicity. This cardiovascular collapse is primarily due to the drug's effect on which of the following ion channels?

. Voltage-gated calcium channels
. Ligand-gated calcium channels
. Voltage-gated potassium channels
. Voltage-gated sodium channels
. Ligand-gated sodium channels

Correct Answer & Explanation

. Voltage-gated sodium channels

Explanation

Local anesthetics like bupivacaine exert their anesthetic effects by blocking voltage-gated sodium channels in peripheral nerves. In the myocardium, profound blockade of these same voltage-gated sodium channels by bupivacaine can cause severe arrhythmias and cardiovascular collapse.

Question 14438

Topic: 1. General Principles & Basic Science

During the excitation-contraction coupling of skeletal muscle, calcium is released from the sarcoplasmic reticulum. To initiate the power stroke, this calcium must bind directly to which of the following regulatory proteins?

. Tropomyosin
. Myosin heavy chain
. Troponin C
. Troponin I
. Actin

Correct Answer & Explanation

. Troponin C

Explanation

Calcium binds specifically to Troponin C, which causes a conformational change in the troponin-tropomyosin complex. This shift exposes the myosin-binding sites on the actin filament, allowing cross-bridge formation and subsequent muscle contraction to occur.

Question 14439

Topic: Infection, Pharmacology & VTE

A 40-year-old male presents with an acutely swollen and painful knee. Aspiration yields opaque synovial fluid. Which of the following synovial fluid cell count profiles is most diagnostic of a bacterial septic arthritis?

. WBC 15,000 cells/mm3 with 40% PMNs
. WBC 35,000 cells/mm3 with 60% PMNs
. WBC 60,000 cells/mm3 with 95% PMNs
. WBC 10,000 cells/mm3 with 20% PMNs and positive birefringence
. WBC 2,000 cells/mm3 with 10% PMNs

Correct Answer & Explanation

. WBC 60,000 cells/mm3 with 95% PMNs

Explanation

Septic arthritis is typically characterized by a synovial fluid white blood cell (WBC) count greater than 50,000 cells/mm3 with a polymorphonuclear (PMN) cell predominance of greater than 75% to 90%. Counts above 50,000 with a severe left shift mandate urgent treatment for joint sepsis.

Question 14440

Topic: 1. General Principles & Basic Science

According to the ALARA (As Low As Reasonably Achievable) principles for intraoperative radiation safety, the inverse square law dictates exposure. If an orthopedic surgeon steps back from the fluoroscopy C-arm from a distance of 1 meter to 2 meters, their radiation exposure is reduced to what fraction of the original dose?

. One-half
. One-third
. One-fourth
. One-eighth
. One-sixteenth

Correct Answer & Explanation

. One-fourth

Explanation

The inverse square law states that radiation exposure is inversely proportional to the square of the distance from the source. Therefore, doubling the distance from the radiation source reduces the exposure dose to one-fourth (1/2^2) of its original value.

Test Yourself

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

On this Page