Menu

1. General Principles & Basic Science MCQs

Practice Set 648 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 12941

Topic: Biomechanics & Biomaterials

To minimize the risk of galvanic corrosion, which combination of orthopedic implant metals should strictly be avoided in a single construct?

. Cobalt-chrome and Titanium
. Stainless steel and Titanium
. Tantalum and Titanium
. Stainless steel and Cobalt-chrome
. Titanium and Titanium alloy

Correct Answer & Explanation

. Cobalt-chrome and Titanium

Explanation

Combining stainless steel and titanium in the same implant construct creates a high risk for galvanic corrosion due to their significant differences in electrochemical potential. If mixed metals are necessary, cobalt-chrome and titanium are generally safe to combine.

Question 12942

Topic: 1. General Principles & Basic Science
Following surgical repair of a flexor tendon, what type of collagen is predominantly synthesized during the initial proliferative phase (first 3 weeks) before remodeling occurs?
. Type I
. Type II
. Type III
. Type IX
. Type X

Correct Answer & Explanation

. Type III

Explanation

During the initial proliferative phase of tendon healing, fibroblasts predominantly synthesize Type III collagen, which forms disorganized and weaker granulation tissue. During the remodeling phase, this is gradually replaced by the stronger, longitudinally organized Type I collagen.

Question 12943

Topic: Biology, Genetics & Bone Healing

The FRAX (Fracture Risk Assessment) tool is utilized to estimate a patient's 10-year probability of experiencing an osteoporotic fracture. Which of the following conditions is included as a specific risk factor in the FRAX algorithm?

. Osteoarthritis
. Systemic lupus erythematosus
. Rheumatoid arthritis
. Psoriatic arthritis
. Ankylosing spondylitis

Correct Answer & Explanation

. Rheumatoid arthritis

Explanation

Rheumatoid arthritis is heavily associated with secondary osteoporosis and is explicitly included as a risk factor in the FRAX calculation algorithm. Other forms of arthritis, such as osteoarthritis, are not included in the tool.

Question 12944

Topic: 1. General Principles & Basic Science

Prolonged pneumatic tourniquet use during orthopedic surgery can lead to ischemic nerve injury. Based on current evidence, what is the maximum recommended continuous inflation time before a deflation period is required?

. 60 minutes
. 90 minutes
. 120 minutes
. 150 minutes
. 180 minutes

Correct Answer & Explanation

. 120 minutes

Explanation

The widely accepted maximum safe duration for continuous tourniquet inflation is 120 minutes (2 hours). If the surgery extends beyond this, a deflation period of 10 to 15 minutes is recommended to allow for tissue reperfusion before reinflation.

Question 12945

Topic: 1. General Principles & Basic Science

Cortical allografts are commonly used in massive structural reconstructive surgery. Which phase of the "creeping substitution" process is primarily responsible for the significant mechanical weakness often observed in these grafts 6 to 18 months postoperatively?

. Inadequate initial sterile sterilization
. Excessive osteoblastic woven bone formation
. Revascularization and osteoclastic resorption outpacing formation
. Premature fatigue failure of the internal fixation
. Host immunological rejection of the allograft

Correct Answer & Explanation

. Revascularization and osteoclastic resorption outpacing formation

Explanation

During creeping substitution of a cortical allograft, vascular invasion and osteoclastic resorption temporarily outpace new bone formation by osteoblasts. This transient porosity leads to a significant decrease in mechanical strength, peaking between 6 and 18 months postoperatively.

Question 12946

Topic: Biology, Genetics & Bone Healing

A 35-year-old patient undergoes open reduction internal fixation of a nonunion with an autologous cortical bone graft. Which of the following best describes the initial phase of graft incorporation for this type of graft?

. Osteoblastic bone formation
. Osteoclastic resorption
. Chondrocyte proliferation
. Woven bone formation
. Hematoma organization

Correct Answer & Explanation

. Osteoclastic resorption

Explanation

Cortical autografts are primarily osteoconductive and incorporate via a process called creeping substitution. The process begins with osteoclastic resorption of the Haversian canals, which initially weakens the graft mechanically, followed later by osteoblastic bone formation.

Question 12947

Topic: Biology, Genetics & Bone Healing

A 24-year-old patient presents with a history of recurrent fractures and anemia. Radiographs demonstrate diffusely sclerotic bone with a 'rugger jersey' spine and 'Erlenmeyer flask' deformity of the distal femurs. A defect in which of the following mechanisms is most likely responsible?

. Type 1 collagen synthesis
. Carbonic anhydrase II activity
. Fibroblast growth factor receptor 3 (FGFR3)
. Runx2/Cbfa1 transcription
. Vitamin D receptor function

Correct Answer & Explanation

. Carbonic anhydrase II activity

Explanation

The clinical and radiographic presentation is classic for osteopetrosis (marble bone disease). The underlying defect is a failure of osteoclastic bone resorption, often due to a mutation in carbonic anhydrase II, leading to an inability to acidify Howship's lacunae.

Question 12948

Topic: Biomechanics & Biomaterials

In comparing orthopedic implant materials, which of the following alloys has a Young's modulus of elasticity most similar to that of human cortical bone?

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

Correct Answer & Explanation

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

Explanation

Young's modulus is a measure of a material's stiffness. Cortical bone has a modulus of approximately 15-20 GPa. Among metallic implants, Titanium alloy (approx. 110 GPa) is closer to cortical bone than Stainless Steel (~200 GPa) or Cobalt-Chromium (~210-240 GPa), resulting in less stress shielding compared to stiffer metals.

Question 12949

Topic: Biology, Genetics & Bone Healing

A complete direct ligamentous insertion into bone transitions through four distinct histomorphological zones to dissipate stress. What is the correct order of these zones from ligament to bone?

. Ligament, calcified fibrocartilage, uncalcified fibrocartilage, bone
. Ligament, uncalcified fibrocartilage, calcified fibrocartilage, bone
. Ligament, woven bone, lamellar bone, cortical bone
. Ligament, Sharpey's fibers, periosteum, bone
. Ligament, loose connective tissue, calcified fibrocartilage, bone

Correct Answer & Explanation

. Ligament, uncalcified fibrocartilage, calcified fibrocartilage, bone

Explanation

Direct ligamentous insertions transition through four distinct zones to minimize stress concentration at the attachment site: (1) Ligament/tendon, (2) Uncalcified fibrocartilage, (3) Calcified fibrocartilage (separated from zone 2 by the tidemark), and (4) Bone.

Question 12950

Topic: 1. General Principles & Basic Science

In human articular cartilage, which zone is characterized by the highest concentration of proteoglycans, the lowest concentration of water, and collagen fibrils oriented perpendicular to the articular surface?

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

Correct Answer & Explanation

. Deep (radial) zone

Explanation

The deep (radial) zone of articular cartilage is characterized by collagen fibrils oriented vertically (perpendicular) to the joint surface, providing resistance to compressive forces. It has the highest concentration of proteoglycans and the lowest water content of the uncalcified zones.

Question 12951

Topic: 1. General Principles & Basic Science
Tranexamic acid (TXA) is routinely utilized in orthopedic surgery to minimize perioperative blood loss. Which of the following best describes its mechanism of action?
. Direct inhibition of Factor Xa
. Competitive inhibition of plasminogen activation
. Irreversible inhibition of cyclooxygenase
. Activation of antithrombin III
. Promotion of platelet aggregation via von Willebrand factor

Correct Answer & Explanation

. Competitive inhibition of plasminogen activation

Explanation

Tranexamic acid is a synthetic analog of the amino acid lysine. It reversibly and competitively binds to the lysine-binding sites on plasminogen, preventing its activation to plasmin, thereby inhibiting fibrinolysis and stabilizing the blood clot.

Question 12952

Topic: Infection, Pharmacology & VTE

In periprosthetic joint infections, Staphylococcus aureus evades the host immune system and antibiotics primarily through the formation of a biofilm. What is the initial stage of biofilm formation on an orthopedic implant?

. Irreversible attachment via exopolysaccharide production
. Reversible attachment of planktonic bacteria to the surface
. Quorum sensing and microcolony formation
. Maturation of the extracellular polymeric substance (EPS)
. Dispersion of bacteria into the surrounding tissue

Correct Answer & Explanation

. Reversible attachment of planktonic bacteria to the surface

Explanation

Biofilm formation follows a distinct sequence: (1) Reversible attachment of planktonic (free-floating) bacteria to the implant surface, (2) Irreversible attachment mediated by adhesins, (3) Microcolony formation via quorum sensing, (4) Maturation with production of the extracellular polymeric substance (EPS) matrix, and (5) Dispersion.

Question 12953

Topic: Surgical Anatomy & Approaches

A patient sustains a closed midshaft humerus fracture and presents with a wrist drop. If the radial nerve injury is classified as an axonotmesis, which of the following components of the nerve remains intact?

. Axon only
. Axon and Myelin
. Endoneurium, perineurium, and epineurium
. Epineurium only
. No components remain intact

Correct Answer & Explanation

. Endoneurium, perineurium, and epineurium

Explanation

In axonotmesis (Sunderland second degree), the axon and myelin sheath are disrupted, causing Wallerian degeneration distal to the injury. However, the connective tissue framework (endoneurium, perineurium, and epineurium) remains completely intact, allowing for spontaneous axonal regeneration at approximately 1 mm/day.

Question 12954

Topic: Biomechanics & Biomaterials

When evaluating the biomechanics of cortical bone screws, which of the following alterations to the screw design would most significantly increase its pullout strength?

. Decreasing the outer (major) diameter
. Increasing the inner (core/minor) diameter
. Decreasing the thread pitch
. Decreasing the length of thread engagement
. Using a self-tapping tip instead of a standard tip

Correct Answer & Explanation

. Decreasing the outer (major) diameter

Explanation

Screw pullout strength is primarily determined by the volume of bone caught between the threads. It is directly proportional to the major (outer) diameter, the length of thread engagement, and inversely proportional to the thread pitch (finer pitch = more threads engaged, hence decreasing pitch increases pullout strength).

Question 12955

Topic: Surgical Anatomy & Approaches

During the direct anterior approach (Smith-Petersen) to the hip, the superficial surgical interval exploits a true internervous plane between which two muscles?

. Tensor fasciae latae and Gluteus medius
. Sartorius and Tensor fasciae latae
. Rectus femoris and Pectineus
. Adductor longus and Gracilis
. Gluteus maximus and Gluteus medius

Correct Answer & Explanation

. Sartorius and Tensor fasciae latae

Explanation

The direct anterior approach (Smith-Petersen) utilizes a true internervous plane. The superficial interval is between the Sartorius (femoral nerve) and the Tensor Fasciae Latae (superior gluteal nerve). The deep interval is between the Rectus Femoris (femoral nerve) and the Gluteus Medius (superior gluteal nerve).

Question 12956

Topic: Biology, Genetics & Bone Healing

Teriparatide, a recombinant human parathyroid hormone (PTH) analog, is used in the treatment of severe osteoporosis. What is the primary mechanism by which it increases bone mineral density?

. Inhibition of osteoclast-mediated bone resorption
. Downregulation of RANKL expression
. Intermittent administration stimulates osteoblastic bone formation
. Continuous administration stimulates osteoblastic bone formation
. Binding directly to the Wnt/beta-catenin pathway

Correct Answer & Explanation

. Intermittent administration stimulates osteoblastic bone formation

Explanation

Teriparatide (PTH 1-34) is an anabolic agent. While continuous exposure to elevated PTH leads to osteoclastic bone resorption, intermittent daily administration has a paradoxically anabolic effect, primarily stimulating osteoblast activity and new bone formation.

Question 12957

Topic: Biomechanics & Biomaterials

An orthopedic surgeon considers using a titanium alloy screw to secure a stainless steel plate in a fracture construct. What is the primary biological or mechanical reason this mixed-metal combination is generally avoided?

. Excessive stress shielding
. Increased risk of third-body wear
. Risk of galvanic corrosion
. Inability to achieve a rigid construct
. Differences in the coefficient of thermal expansion

Correct Answer & Explanation

. Risk of galvanic corrosion

Explanation

Mixing dissimilar metals, such as stainless steel and titanium, within a conductive medium (body fluid) creates an electrochemical cell, leading to galvanic corrosion. The more anodic metal will corrode at an accelerated rate, potentially leading to implant failure or adverse local tissue reactions.

Question 12958

Topic: Biology, Genetics & Bone Healing

Which of the following genetic mutations is most commonly associated with malignant infantile osteopetrosis, leading to defective osteoclast acidification?

. COMP
. FGFR3
. TCIRG1
. COL1A1
. RUNX2

Correct Answer & Explanation

. TCIRG1

Explanation

Malignant infantile osteopetrosis is an autosomal recessive disorder most commonly caused by mutations in the TCIRG1 gene (encoding the a3 subunit of the vacuolar H+-ATPase) or the CLCN7 gene. This results in the inability of osteoclasts to secrete protons and acidify the Howship's lacuna, fundamentally impairing bone resorption.

Question 12959

Topic: Biomechanics & Biomaterials

In orthopedic biomechanics, the pullout strength of a cortical screw is directly proportional to which of the following geometric factors?

. Inner root diameter
. Thread pitch
. Outer thread diameter
. Screw head diameter
. Insertion torque

Correct Answer & Explanation

. Outer thread diameter

Explanation

Screw pullout strength represents the force required to pull the screw axially out of the bone. It is directly proportional to the outer (major) diameter of the thread, the length of thread engagement in the bone, and the shear strength of the bone material. It is inversely proportional to the thread pitch (distance between threads).

Question 12960

Topic: Biology, Genetics & Bone Healing

A 65-year-old man presents with progressive bowing of his right tibia and increasing hat size. Laboratory studies show normal serum calcium and phosphorus but markedly elevated alkaline phosphatase. What is the primary cellular abnormality initiating this disease process?

. Defective osteoid mineralization by osteoblasts
. Overactive osteoclasts causing excessive bone resorption
. Decreased production of Type I collagen by osteocytes
. Accumulation of unmineralized osteoid due to vitamin D deficiency
. Monoclonal proliferation of plasma cells stimulating osteoclasts

Correct Answer & Explanation

. Overactive osteoclasts causing excessive bone resorption

Explanation

The patient has Paget's disease of bone. The disease process is initiated by a pronounced, localized increase in osteoclastic bone resorption (the lytic phase), which is subsequently followed by a compensatory but highly disorganized burst of osteoblastic bone formation (mixed and sclerotic phases). The initial defect is the intensely overactive osteoclasts, which are often large and hypernucleated.

Test Yourself

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

On this Page