MCQs – Basic 5

Modern Study Review (AI-Generated)

High-Yield Summary

This topic is a staple of the Royal College exam, focusing heavily on biomaterials, fracture fixation principles, metabolic bone physiology, and transfusion medicine. The single most important trade-off in clinical scenarios often lies between implant material properties—specifically, the choice between titanium and cobalt chrome based on modulus of elasticity versus wear resistance. While the exam favors classic biomechanical principles such as plate placement on the tension side, modern practice increasingly incorporates advanced biomaterials and refined cementing techniques. Understanding vitamin D metabolism and coagulation factor stability is critical for perioperative management and patient safety.

High-Yield Decision Matrix

Active Recall Q&A

Proteoglycan and Cartilage Biochemistry

Q: What components typically make up a proteoglycan?
A: A proteoglycan typically consists of a core protein and glycosaminoglycans such as chondroitin sulfate, keratan sulfate, and dermatan sulfate.
Related Pearl: Aggrecan is the main proteoglycan in cartilage and forms large aggregates by binding hyaluronic acid via link proteins, critical for cartilage resilience.

Q: Is hyaluronic acid part of the proteoglycan structure?
A: No, hyaluronic acid is a glycosaminoglycan but is not part of the proteoglycan per se; it binds proteoglycans to form aggregates.
Related Pearl: The proteoglycan-hyaluronic acid aggregate structure is essential for cartilage’s load-bearing and hydration properties.

Fracture Fixation and Implant Materials

Q: Why are plates placed on the tension side of fractures?
A: Plates are placed on the tension side because they are loaded best in tension and can act as a tension band system.
Related Pearl: Placing plates on the compression side risks implant failure due to compressive loading, which plates tolerate poorly.

Q: How does forged cobalt chrome compare to cast cobalt chrome?
A: Forged cobalt chrome is stronger than cast cobalt chrome.
Related Pearl: Forging refines the metal grain structure, improving fatigue resistance and mechanical strength.

Q: When does fatigue failure of a metal implant occur?
A: Fatigue failure occurs with cyclic loading past the endurance limit, usually within the elastic range, not the plastic range.
Related Pearl: Fatigue failure is a microscopic crack propagation process accelerated by repetitive loading below yield strength.

Q: How does titanium compare to cobalt chrome in modulus of elasticity and wear resistance?
A: Titanium has a lower modulus of elasticity and is less resistant to surface wear, making it a poor bearing surface compared to cobalt chrome.
Related Pearl: Titanium’s lower modulus reduces stress shielding but limits its use in articulating surfaces due to wear debris generation.

Q: What is the histiocytic response difference between titanium and cobalt chrome?
A: Titanium elicits less histiocytic response than cobalt chrome.
Related Pearl: Reduced histiocytic response may decrease inflammatory reactions around titanium implants.

Embryology and Endocrinology

Q: When does ossification begin in the embryo?
A: Ossification begins between 7 and 12 weeks of embryonic development.
Related Pearl: Primary ossification centers appear first in long bones during this period, critical for skeletal formation.

Q: Where is parathyroid hormone (PTH) synthesized and secreted?
A: PTH is synthesized and secreted by the chief cells of the parathyroid gland.
Related Pearl: PTH regulates calcium homeostasis by increasing bone resorption, renal calcium reabsorption, and activating vitamin D.

Vitamin D Metabolism and Calcium Absorption

Q: Where is 1,25 dihydroxyvitamin D produced?
A: It is produced in the proximal tubule of the kidney.
Related Pearl: This active form of vitamin D increases intestinal calcium absorption and bone mineralization.

Q: Where is 25 hydroxyvitamin D produced?
A: It is produced in the liver.
Related Pearl: 25(OH)D is the main circulating form and is used to assess vitamin D status clinically.

Q: How does vitamin D affect calcium absorption?
A: Vitamin D facilitates production of calcium-binding protein in the intestinal mucosa, increasing calcium absorption.
Related Pearl: This mechanism is essential for maintaining serum calcium levels and bone health.

Coagulation and Transfusion Medicine

Q: What happens to factor VIII and factor V in stored blood?
A: Factor VIII is negligible at 72 hours; factor V is negligible by 3-5 days in stored blood.
Related Pearl: This degradation limits the efficacy of stored blood for coagulation support over time.

Q: What electrolyte disturbances can massive transfusion with citrated blood cause?
A: It can cause hypocalcemia, which may lead to cardiac arrhythmias; hyperkalemia can also occur but hypocalcemia is more common.
Related Pearl: Citrate chelates calcium, necessitating monitoring and supplementation during massive transfusion protocols.

Biomechanics and Disc Degeneration

Q: How is stress defined in biomechanics?
A: Stress is defined as force per unit area; it is distinct from load.
Related Pearl: Understanding stress distribution is critical for implant design and fracture fixation strategies.

Q: What is the water content of the nucleus and annulus in young adult intervertebral discs?
A: The nucleus is 85% water, and the annulus is 78% water in young adults.
Related Pearl: High water content provides disc elasticity and shock absorption; loss contributes to degeneration.

Q: How does water content change in discs with aging?
A: Water content falls to about 70% in both nucleus and annulus due to proteoglycan and collagen network changes.
Related Pearl: Dehydration of the disc matrix leads to decreased disc height and increased risk of herniation.

Pharmacology and Bone Cement

Q: Which clotting factors does warfarin inhibit?
A: Warfarin inhibits vitamin K-dependent clotting factors II, VII, IX, and X.
Related Pearl: Warfarin’s effect prolongs PT/INR and requires monitoring to avoid bleeding complications.

Q: Which drugs can prolong PT by interacting with warfarin?
A: Metronidazole, septra (trimethoprim-sulfamethoxazole), and cimetidine prolong PT by interacting with warfarin.
Related Pearl: These drugs inhibit warfarin metabolism, increasing bleeding risk.

Q: What cardiac effects does methylmethacrylate monomer have?
A: It may have a direct cardiodepressant effect.
Related Pearl: Awareness of this effect is important during cemented arthroplasty to monitor for hypotension or arrhythmias.

Q: How does methylmethacrylate volume change during mixing and polymerization?
A: Volume increases by 3-5% when mixed and decreases by 5-7% during polymerization.
Related Pearl: Volume changes can affect cement mantle integrity and implant fixation.

Malignant Hyperthermia

Q: What causes malignant hyperthermia?
A: It is caused by uncontrolled release of calcium from the sarcoplasmic reticulum in skeletal muscle.
Related Pearl: Early recognition and treatment with dantrolene are critical to prevent fatal outcomes.

Classic Clinical Notes

• Proteoglycan typically consists of a core protein and glycosaminoglycans such as chondroitan sulfate and keratin sulfate and dermatin sulfate. Hyaluronic acid is a glycosaminoglycan, but it is not part of the proteoglycan per se. Many of these proteoglycans (which are usually aggrecan) bind via a link protein to hyaluronic acid to form a proteoglycan aggregate.

• Place plates on the tension side of fractures because they are loaded best in tension and can act as tension band system.

• Forged cobalt chrome is stronger than cast cobalt chrome.

• Fatigue failure of a metal implant occurs with cyclic loading past the endurance limit, which is usually in the elastic range, not plastic range.

• Titanium has a lower modulus of elasticity than cobalt chrome. It is less resistant to surface wear, making it a poor bearing surface. The histiocytic response to titanium is apparently less than for cobalt chrome.

• Ossification of the embryo begins between 7 and 12 weeks.

• PTH is synthesized and secreted by the chief cells of the parathyroid gland.

• 1, 25 dihydroxyvitamin D (and 24,25 dihydroxyvitamin D) is made in the proximal tubule of the kidney.

• 25 hidroxyvitamin D is made in the liver.

• Vitamin D facilitates production of calcium binding protein in the intestinal mucosa – increases intestinal absorption of calcium.

• In stored blood, factor VIII is negligible at 72 hours, factor V by 3-5 days.

• Massive transfusion with citrated blood – will cause hypocalcemia which can cause cardiac arrhythmias; hyperkalemia can result from broken down blood cells, but more common to have hypocalcemia.

• Stress is defined as force/unit area (it is not the same measurement as load).

• Disc degeneration; in the young adult – nucleus is 85% water, and the annulus is 78% water. The water content of both falls to about 70% with aging. This is largely due to changes in the proteoglycan and collagen network.

• Warfarin acts to inhibit the production of vitamin K-dependent clotting factors – II, VII, IX, X. Metronidazole, septra, and cimetidine all prolong the PT by interacting with warfarin.

• Methylmethacrylate monomer may have a direct effect on cardiac system (cardiodepressant); as the cement is mixed, it increases in volume about 3-5%; as the monomer polymerizes, the volume decreases 5-7%.

• Malignant hyperthermia is caused by a uncontrolled release of calcium in the skeletal muscles from the sarcoplasmic reticulum.

Last Updated on January 25, 2026 by Christian Veillette