Menu

1. General Principles & Basic Science MCQs

Practice Set 232 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 4621

Topic: Biology, Genetics & Bone Healing

According to Perren's strain theory regarding fracture healing, what biological response is observed when the interfragmentary strain at a fracture site is between 2% and 10%?

. Primary bone healing via cutting cones
. Resorption of the fracture ends without callus formation
. Callus formation and secondary bone healing
. Granulation tissue formation followed by persistent nonunion
. Woven bone formation directly converting to lamellar bone without intermediate tissues

Correct Answer & Explanation

. Callus formation and secondary bone healing

Explanation

Perren's strain theory states that the type of tissue that forms at a fracture site is dependent on the strain. Absolute stability (<2% strain) allows for primary bone healing (cutting cones) without callus. Relative stability (2-10% strain) stimulates callus formation (secondary bone healing). Strain greater than 10-15% leads to the formation of fibrous or granulation tissue, ultimately resulting in a nonunion if the strain is not reduced.

Question 4622

Topic: Biology, Genetics & Bone Healing

Articular cartilage is structurally organized into distinct zones. Which zone is specifically adapted to resist the highest shear forces and is characterized by a dense concentration of collagen fibers oriented parallel to the articular surface?

. 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 comprises the top 10-20% of articular cartilage. It has a high concentration of densely packed collagen type II fibers that are aligned parallel to the joint surface. This specific structural orientation provides the highest tensile strength and the greatest resistance to shear forces within the joint.

Question 4623

Topic: 1. General Principles & Basic Science

During fracture healing via secondary intention, a soft callus is eventually replaced by hard callus, which consists of woven bone.

Which of the following characteristics best describes woven bone when compared to mature lamellar bone?

. Highly organized, parallel collagen fibers
. Lower osteocyte cell density
. Slow, organized deposition rate
. Isotropic mechanical properties
. Anisotropic mechanical properties

Correct Answer & Explanation

. Isotropic mechanical properties

Explanation

Woven bone is characterized by randomly oriented collagen fibers, a high cell density (more osteocytes), and rapid formation. Because the collagen fibers lack a specific directional orientation, woven bone has isotropic mechanical properties, meaning it exhibits equal mechanical strength in all directions. In contrast, lamellar bone is highly organized, slowly formed, and anisotropic (stronger in the direction of the loaded axis).

Question 4624

Topic: 1. General Principles & Basic Science
Tranexamic acid (TXA) is frequently administered during total joint arthroplasty to minimize perioperative blood loss. Which of the following describes the primary mechanism of action of tranexamic acid?
. Irreversible inhibition of cyclooxygenase enzymes
. Reversible competitive blockade of lysine binding sites on plasminogen
. Direct inhibition of Factor Xa in the coagulation cascade
. Allosteric activation of antithrombin III
. Inhibition of ADP-induced platelet aggregation

Correct Answer & Explanation

. Reversible competitive blockade of lysine binding sites on plasminogen

Explanation

Tranexamic acid (TXA) is a synthetic analog of the amino acid lysine. It acts as an antifibrinolytic agent by reversibly and competitively binding to the lysine receptor sites on plasminogen. This prevents plasminogen from converting into the active enzyme plasmin, thereby inhibiting the degradation of fibrin clots.

Question 4625

Topic: Biology, Genetics & Bone Healing

A 30-year-old female is diagnosed with an expansile, lytic lesion in her distal femur that extends to the subchondral bone. Biopsy confirms a Giant Cell Tumor (GCT) of bone. She is treated preoperatively with denosumab.

What is the molecular target of denosumab in the treatment of this tumor?

. The RANK receptor on the surface of osteoclast precursors
. Receptor Activator of Nuclear factor Kappa-B Ligand (RANKL) secreted by neoplastic stromal cells
. Osteoprotegerin (OPG)
. Vascular Endothelial Growth Factor (VEGF)
. Matrix Metalloproteinases (MMPs)

Correct Answer & Explanation

. Receptor Activator of Nuclear factor Kappa-B Ligand (RANKL) secreted by neoplastic stromal cells

Explanation

In a Giant Cell Tumor of bone, the actual neoplastic cells are the mononuclear spindle-like stromal cells. These cells secrete excessive amounts of RANKL, which recruits and activates the reactive multinucleated giant cells (osteoclasts) that cause bone destruction. Denosumab is a monoclonal antibody that specifically targets and binds to RANKL, preventing it from interacting with the RANK receptor on osteoclast precursors, thereby halting bone lysis.

Question 4626

Topic: Biomechanics & Biomaterials

When a constant magnitude of load is applied to a viscoelastic material over a prolonged period, the material undergoes increasing progressive deformation. This biomechanical property is known as:

. Stress relaxation
. Hysteresis
. Creep
. Fatigue failure
. Anisotropy

Correct Answer & Explanation

. Creep

Explanation

Creep is defined as the progressive, time-dependent deformation of a viscoelastic material under a constant load. Stress relaxation is the decrease in stress (force) over time when the material is held at a constant deformation. Hysteresis is the energy lost (usually as heat) during the loading and unloading cycle.

Question 4627

Topic: 1. General Principles & Basic Science

In normal mature articular cartilage, which zone is characterized by having the highest concentration of proteoglycans, the lowest concentration of water, and collagen fibers arranged perpendicularly (vertically) to the joint 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 contains collagen fibers oriented perpendicular to the articular surface. It contains the highest concentration of proteoglycans and the lowest water content, making it critical for resisting compressive forces. The superficial zone has water content highest, collagen parallel to surface, and lowest proteoglycan content.

Question 4628

Topic: Biology, Genetics & Bone Healing

Which of the following statements most accurately describes the mechanism and requirements of primary (direct) bone healing?

. It occurs via endochondral ossification and a robust cartilage intermediate.
. It requires absolute stability and occurs via cutting cones crossing the fracture site.
. It relies on controlled micromotion to stimulate abundant bridging callus formation.
. It proceeds primarily through intramembranous ossification mediated solely by the periosteum.
. It is the typical mode of healing seen with intramedullary nailing of comminuted diaphyseal fractures.

Correct Answer & Explanation

. It requires absolute stability and occurs via cutting cones crossing the fracture site.

Explanation

Primary (direct) bone healing occurs without a cartilage intermediate and without the formation of a visible callus. It requires absolute stability (rigid fixation with no micromotion, such as with compression plating) and intimate bone contact. The mechanism involves osteoclastic cutting cones that cross the fracture line, immediately followed by osteoblasts laying down new osteons (Haversian remodeling).

Question 4629

Topic: 1. General Principles & Basic Science

A 55-year-old poorly controlled diabetic patient presents with a warm, swollen, erythematous right foot. Radiographs show periarticular osteopenia and early joint subluxation in the midfoot. Differentiating acute Charcot neuroarthropathy from osteomyelitis is critical. Which of the following advanced diagnostic modalities offers the highest specificity for distinguishing true infection from Charcot arthropathy?

. Erythrocyte sedimentation rate (ESR) alone
. Triple-phase technetium-99m bone scan
. MRI without intravenous gadolinium
. Technetium-99m hexamethylpropyleneamine oxime (HMPAO) scan alone
. Indium-111 labeled leukocyte (WBC) scan combined with technetium-99m sulfur colloid marrow scan

Correct Answer & Explanation

. Indium-111 labeled leukocyte (WBC) scan combined with technetium-99m sulfur colloid marrow scan

Explanation

Differentiating Charcot from osteomyelitis is difficult because both show hyperperfusion and bony changes. A combined Indium-111 WBC scan and Tc-99m sulfur colloid bone marrow scan is highly specific. In Charcot arthropathy, there is increased bone turnover and marrow expansion, leading to matched uptake on both scans. In osteomyelitis, the infection suppresses the normal marrow, leading to mismatched uptake (increased WBC uptake, decreased marrow uptake).

Question 4630

Topic: 1. General Principles & Basic Science

Which zone of articular cartilage has the highest concentration of proteoglycans, the lowest water content, and collagen fibers oriented perpendicular to the joint surface?

. Superficial (tangential) zone
. Transitional (middle) zone
. Deep (radial) zone
. Calcified zone
. Subchondral bone plate

Correct Answer & Explanation

. Deep (radial) zone

Explanation

The deep (radial) zone contains the highest concentration of proteoglycans and the lowest water content. The collagen fibers are thick and oriented perpendicularly to the articular surface to resist compressive loads. The superficial zone has fibers parallel to the surface to resist shear forces.

Question 4631

Topic: Biomechanics & Biomaterials

A revision total hip arthroplasty is performed for a fractured modular neck. Examination of the taper junction reveals black debris and pitting. What is the primary initiating mechanism of corrosion at the modular taper junction of a titanium stem and cobalt-chrome head?

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

Correct Answer & Explanation

. Fretting corrosion

Explanation

Fretting corrosion (mechanically assisted crevice corrosion) is the primary initiating mode of failure at modular junctions in total joint arthroplasty. Micro-motion mechanically disrupts the protective passivation (oxide) layer, which then allows crevice and galvanic corrosion to occur.

Question 4632

Topic: Biology, Genetics & Bone Healing

Bone morphogenetic proteins (BMPs) initiate intracellular signaling primarily by binding to transmembrane serine/threonine kinase receptors that directly phosphorylate and activate which of the following downstream mediators?

. Wnt/beta-catenin complex
. Smad proteins
. JAK/STAT pathway
. RANK/RANKL complex
. Notch receptors

Correct Answer & Explanation

. Smad proteins

Explanation

BMPs bind to types I and II serine/threonine kinase receptors. Upon activation, they phosphorylate receptor-regulated Smads (R-Smads 1, 5, and 8), which then bind to the common-partner Smad (Co-Smad 4) to translocate to the nucleus and regulate the transcription of osteogenic target genes.

Question 4633

Topic: Biology, Genetics & Bone Healing

According to Perren's strain theory of bone healing, the type of tissue that forms in a fracture gap is dictated by the mechanical strain environment. What is the maximum tissue strain limit that allows for the formation of lamellar bone?

. < 2%
. 2% - 10%
. 10% - 30%
. 30% - 50%
. > 50%

Correct Answer & Explanation

. < 2%

Explanation

Perren's strain theory states that lamellar bone can only form in low strain environments (< 2% strain). Woven bone tolerates up to 10% strain, fibrocartilage tolerates 10-30%, and granulation tissue can tolerate up to 100% strain before failing.

Question 4634

Topic: Infection, Pharmacology & VTE

When utilizing a posteromedial approach to the proximal tibia for the fixation of a complex tibial plateau fracture, the surgical interval is developed between which of the following structures?

. Medial head of the gastrocnemius and the soleus
. Semimembranosus and the medial collateral ligament
. Medial head of the gastrocnemius and the pes anserinus
. Tibialis posterior and the flexor digitorum longus
. Tibialis anterior and the medial tibial crest

Correct Answer & Explanation

. Medial head of the gastrocnemius and the pes anserinus

Explanation

The posteromedial approach to the proximal tibia involves an internervous interval (though practically an intermuscular interval) between the medial head of the gastrocnemius (innervated by the tibial nerve) posteriorly and the pes anserinus (sartorius, gracilis, semitendinosus) anteriorly. Retracting the pes anteriorly and the medial gastrocnemius posteriorly protects the neurovascular bundle and provides excellent exposure to posteromedial tibial plateau fragments.

Question 4635

Topic: Infection, Pharmacology & VTE

A collegiate football player sustains a valgus injury to the knee, resulting in a complete tear of the medial collateral ligament (MCL). During surgical reconstruction, accurate identification of the superficial MCL footprints is critical. The distal insertion of the superficial MCL is correctly located:

. Immediately deep to the medial meniscus
. Approximately 1.5 cm distal to the joint line on the anteromedial tibia
. Approximately 4 to 5 cm distal to the joint line, deep to the pes anserinus
. Directly on the adductor tubercle of the distal femur
. On the medial aspect of the patellar tendon insertion

Correct Answer & Explanation

. Approximately 4 to 5 cm distal to the joint line, deep to the pes anserinus

Explanation

The superficial medial collateral ligament (sMCL) has its proximal footprint on the posterior aspect of the medial femoral epicondyle. Its distal footprint is located on the medial aspect of the proximal tibia, approximately 4.5 cm (range 4 to 5 cm) distal to the joint line, and lies deep to the pes anserinus. It is the primary restraint to valgus stress at 30 degrees of knee flexion.

Question 4636

Topic: Biology, Genetics & Bone Healing

According to Perren's strain theory of bone healing, the interfragmentary strain threshold determines the type of tissue that forms within a fracture gap. Primary (direct) bone healing without callus formation occurs when the interfragmentary strain is maintained below what percentage?

. 2%
. 10%
. 17%
. 50%
. 100%

Correct Answer & Explanation

. 2%

Explanation

Perren's strain theory dictates that tissues cannot form if the local strain exceeds their tolerance. Granulation tissue tolerates up to 100% strain, fibrous connective tissue up to 17%, and fibrocartilage between 2% and 10%. Lamellar bone can only form directly (primary bone healing via cutting cones) when the interfragmentary strain is strictly below 2%, which is typically achieved with rigid absolute stability (e.g., compression plating).

Question 4637

Topic: 1. General Principles & Basic Science

The microanatomy of adult articular cartilage is divided into specific structural zones. Which of the following statements accurately characterizes the superficial (tangential) zone of articular cartilage?

. It contains the highest concentration of water and collagen fibers oriented parallel to the joint surface.
. It contains the highest concentration of proteoglycans and chondrocytes that are organized into vertical columns.
. It is separated from the deeper cartilage by the tidemark and contains no viable chondrocytes.
. It primarily consists of Type X collagen and resists compressive forces more than shear forces.
. It is the thickest zone and its collagen fibers are oriented perpendicularly to the subchondral bone.

Correct Answer & Explanation

. It contains the highest concentration of water and collagen fibers oriented parallel to the joint surface.

Explanation

The superficial (tangential) zone makes up 10-20% of articular cartilage thickness. It has the highest water content (up to 80%), the lowest proteoglycan content, and features flat chondrocytes with Type II collagen fibers oriented parallel to the joint surface to resist shear stress. The deep zone has the highest proteoglycan content, lowest water content, and collagen fibers arranged vertically to resist compression.

Question 4638

Topic: 1. General Principles & Basic Science

Articular cartilage is a highly specialized tissue organized into four distinct zones to handle complex mechanical loads. Which zone typically contains the highest concentration of proteoglycans, the lowest concentration of water, and collagen fibrils arranged perpendicularly to the articular surface?

. Superficial (tangential) zone
. Middle (transitional) zone
. Deep (radial) zone
. Calcified cartilage zone
. Subchondral bone plate

Correct Answer & Explanation

. Deep (radial) zone

Explanation

The deep (radial) zone of articular cartilage is characterized by the highest concentration of proteoglycans, the lowest concentration of water, and thick collagen fibrils oriented perpendicularly to the subchondral bone, which provides the highest resistance to compressive forces. The superficial zone has the highest water content and collagen arranged parallel to the surface for shear resistance.

Question 4639

Topic: Biomechanics & Biomaterials

Following a traumatic laceration and subsequent zone II flexor tendon repair in the index finger, preservation or reconstruction of the pulley system is mandatory for optimal biomechanics. Which of the following sets of annular pulleys are considered the most mechanically critical to prevent bowstringing and flexion contractures?

. A1 and A3
. A2 and A4
. A3 and A5
. A1, A3, and A5
. C1, C2, and C3

Correct Answer & Explanation

. A2 and A4

Explanation

The A2 and A4 pulleys are the most mechanically critical annular pulleys in the flexor tendon sheath. They arise directly from the periosteum of the proximal and middle phalanges, respectively. Loss of these two pulleys leads to significant bowstringing of the flexor tendons, decreased excursion efficiency, reduced grip strength, and progressive flexion contractures.

Question 4640

Topic: Biology, Genetics & Bone Healing

A massive structural cortical allograft is utilized to reconstruct a large segmental bone defect following tumor resection. The biological process by which the living host bone gradually resorbs the necrotic allograft bone via osteoclastic activity, immediately followed by new osteoblastic bone formation on the remaining allograft scaffold, is termed:

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

Correct Answer & Explanation

. Creeping substitution

Explanation

Creeping substitution is the classical process by which a non-vascularized cortical bone graft is incorporated. It involves the simultaneous resorption of the graft by host osteoclasts and the laying down of new host bone by osteoblasts along the haversian canals. Osteoinduction refers to the stimulation of phenotypic conversion of progenitor cells into osteoblasts. Osteoconduction provides a physical scaffold.

Test Yourself

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

On this Page