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1. General Principles & Basic Science MCQs

Practice Set 679 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 13561

Topic: 1. General Principles & Basic Science
Articular cartilage provides a low-friction gliding surface for joints. Which specific type of collagen constitutes the vast majority of the collagen framework in hyaline articular cartilage?
. Type I
. Type II
. Type III
. Type IX
. Type X

Correct Answer & Explanation

. Type II

Explanation

Type II collagen comprises 90-95% of the collagen in hyaline articular cartilage. Type I is predominantly found in bone, tendon, and fibrocartilage. Type X collagen is localized specifically to the calcified zone of articular cartilage and the hypertrophic zone of the growth plate.

Question 13562

Topic: 1. General Principles & Basic Science

The healing potential of a meniscal tear is heavily dependent on its blood supply. Which of the following arterial vessels primarily provide the blood supply to the peripheral portions of the menisci?

. Middle genicular artery
. Superior medial and lateral genicular arteries
. Inferior medial and lateral genicular arteries
. Descending genicular artery
. Anterior tibial recurrent artery

Correct Answer & Explanation

. Inferior medial and lateral genicular arteries

Explanation

The primary blood supply to the peripheral 10-30% of the meniscus (the 'red-red' zone, which has the highest healing potential) is derived from the medial and lateral inferior genicular arteries. The middle genicular artery supplies the cruciate ligaments.

Question 13563

Topic: 1. General Principles & Basic Science

During a transfemoral (above-knee) amputation, an adductor myodesis is routinely performed to optimize stump mechanics and ambulation potential. To prevent the most common post-operative deformity, the adductor magnus is securely anchored to which aspect of the residual femur?

. Anterior cortex
. Posterior cortex
. Medial cortex
. Lateral cortex

Correct Answer & Explanation

. Lateral cortex

Explanation

In a transfemoral amputation, the loss of adductor muscle mass leads to an overpowering by the intact abductors (gluteus medius/minimus), creating an abduction contracture. To prevent this, the adductor magnus tendon is anchored to the lateral cortex of the distal residual femur under tension (myodesis), which stabilizes the femur in adduction and improves gait mechanics.

Question 13564

Topic: 1. General Principles & Basic Science

Which zone of articular cartilage has the largest diameter collagen fibrils arranged perpendicular to the joint surface, the highest concentration of proteoglycans, and the lowest water content?

. Superficial (tangential) zone
. Transitional (middle) zone
. Deep (radial) zone
. Calcified zone
. Tidemark

Correct Answer & Explanation

. Deep (radial) zone

Explanation

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

Question 13565

Topic: 1. General Principles & Basic Science

Which of the following lower extremity amputations is associated with the highest percentage of energy expenditure above baseline during walking?

. Syme amputation
. Unilateral transtibial amputation
. Bilateral transtibial amputation
. Unilateral transfemoral amputation
. Knee disarticulation

Correct Answer & Explanation

. Unilateral transfemoral amputation

Explanation

Energy expenditure during walking increases with more proximal amputation levels. Unilateral transfemoral amputations require approximately 60-65% increased energy expenditure above baseline. This is higher than a unilateral transtibial (25%) and bilateral transtibial (41%). Bilateral transfemoral amputation is the highest overall (~200%), but is not listed.

Question 13566

Topic: 1. General Principles & Basic Science
During the remodeling phase of tendon healing, the biomechanical strength of the tendon improves significantly. This is primarily due to which of the following molecular changes?
. Replacement of Type I collagen with Type III collagen
. Conversion of Type III collagen to Type I collagen and increased cross-linking
. Increased synthesis of unorganized ground substance and proteoglycans
. Intense inflammatory cell infiltration and neovascularization
. Proliferation of epitenon-derived myofibroblasts

Correct Answer & Explanation

. Conversion of Type III collagen to Type I collagen and increased cross-linking

Explanation

Tendon healing occurs in three phases: inflammation, proliferation, and remodeling. During the remodeling phase (starting around 6 weeks), the relatively weak and disorganized Type III collagen laid down during the proliferative phase is gradually replaced by highly organized, heavily cross-linked Type I collagen, increasing tensile strength.

Question 13567

Topic: 1. General Principles & Basic Science

According to Sunderland's classification of peripheral nerve injuries, a third-degree injury involves disruption of the axon and which of the following structures, while leaving the perineurium intact?

. Myelin sheath only
. Endoneurium
. Perineurium
. Epineurium
. Whole fascicle

Correct Answer & Explanation

. Perineurium

Explanation

Sunderland classification: 1st degree = neuropraxia (myelin injury); 2nd degree = axonotmesis (axon severed, all connective tissues intact); 3rd degree = axon + endoneurium disrupted (perineurium intact); 4th degree = axon + endoneurium + perineurium disrupted (epineurium intact); 5th degree = complete transection (neurotmesis).

Question 13568

Topic: Surgical Anatomy & Approaches

A surgeon utilizes the direct anterior approach (Smith-Petersen) for a total hip arthroplasty, exploiting the internervous plane between the sartorius and the tensor fasciae latae (TFL). Which nerve is most at risk during the superficial dissection of this approach?

. Femoral nerve
. Superior gluteal nerve
. Lateral femoral cutaneous nerve
. Obturator nerve
. Sciatic nerve

Correct Answer & Explanation

. Lateral femoral cutaneous nerve

Explanation

The direct anterior approach utilizes the internervous plane between the Sartorius (innervated by the femoral nerve) and the TFL (innervated by the superior gluteal nerve). The Lateral Femoral Cutaneous Nerve (LFCN) courses over the sartorius and is at significant risk of neuropraxia or transection during the superficial dissection.

Question 13569

Topic: Biology, Genetics & Bone Healing

Teriparatide is an anabolic pharmacological agent used for the treatment of severe osteoporosis. What is its specific mechanism of action?

. Inhibits osteoclast activity by binding strongly to hydroxyapatite
. Binds to RANK ligand to prevent osteoclast activation
. Acts as a selective estrogen receptor modulator (SERM)
. Functions as a recombinant human parathyroid hormone (PTH) analog to stimulate osteoblast activity
. Inhibits sclerostin to enhance Wnt signaling and bone formation

Correct Answer & Explanation

. Functions as a recombinant human parathyroid hormone (PTH) analog to stimulate osteoblast activity

Explanation

Teriparatide is a recombinant form of parathyroid hormone (PTH 1-34). When administered intermittently in low doses, it exhibits an anabolic effect by directly stimulating osteoblast activity and bone formation, unlike bisphosphonates or denosumab, which are antiresorptive agents.

Question 13570

Topic: Physiology & Rehabilitation

During the normal gait cycle, the knee relies on the 'screw-home' mechanism for locking in full terminal extension. Which muscle is primarily responsible for 'unlocking' the knee from extension to initiate flexion?

. Biceps femoris
. Semimembranosus
. Popliteus
. Gastrocnemius
. Plantaris

Correct Answer & Explanation

. Popliteus

Explanation

The popliteus muscle acts to internally rotate the tibia on a fixed femur (or externally rotate the femur on a fixed tibia) to unlock the knee from its terminal extension (screw-home) position. This action is essential to initiate knee flexion from a fully extended stance.

Question 13571

Topic: Biology, Genetics & Bone Healing

According to Perren's strain theory, what is the maximum strain tolerated by lamellar bone before failure of formation occurs?

. 1%
. 2%
. 10%
. 30%
. 100%

Correct Answer & Explanation

. 2%

Explanation

Lamellar bone can only tolerate up to 2% strain before rupturing. Woven bone tolerates up to 10% strain, while granulation tissue can tolerate up to 100%.

Question 13572

Topic: 1. General Principles & Basic Science

In articular cartilage, which layer contains the highest concentration of proteoglycans and the lowest concentration of water?

. 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 the highest concentration of proteoglycans and the lowest water content. The superficial zone has the highest water content and collagen concentration but the lowest proteoglycan content.

Question 13573

Topic: Biology, Genetics & Bone Healing

Bone morphogenetic proteins (BMPs) primarily induce osteoblastic differentiation through which of the following intracellular signaling pathways?

. Wnt/beta-catenin
. RANK/RANKL
. SMAD 1/5/8
. JAK/STAT
. Notch

Correct Answer & Explanation

. SMAD 1/5/8

Explanation

BMPs bind to serine/threonine kinase receptors on the cell surface, initiating an intracellular signaling cascade primarily mediated by the phosphorylation of SMAD 1, 5, and 8 proteins. These then complex with SMAD 4 to enter the nucleus and regulate gene transcription.

Question 13574

Topic: 1. General Principles & Basic Science

A 55-year-old diabetic male presents with an acutely swollen, erythematous leg with pain out of proportion to exam. Which of the following intraoperative findings is considered the definitive hallmark of necrotizing fasciitis?

. Purulent drainage from the deep fascia
. Lack of bleeding and lack of resistance to blunt fascial dissection
. Presence of gram-positive cocci in clusters
. Intramuscular gas pockets on ultrasonography
. Hypervascularity of the subcutaneous fat

Correct Answer & Explanation

. Lack of bleeding and lack of resistance to blunt fascial dissection

Explanation

The surgical hallmark of necrotizing fasciitis is the presence of grayish, necrotic fascia that lacks normal bleeding and offers no resistance to blunt manual dissection (the "finger test"). The characteristic fluid is often "dishwater pus" rather than frank purulence.

Question 13575

Topic: 1. General Principles & Basic Science

Within the microanatomy of articular cartilage, which zone possesses the highest concentration of proteoglycans, the lowest concentration of water, and collagen fibrils that are oriented perpendicular to the joint 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 contains the highest concentration of proteoglycans and the lowest concentration of water. The collagen fibrils (Type II) in this zone are large in diameter and oriented strictly perpendicular to the joint surface to resist compressive loads. Conversely, the superficial zone has the highest water content, lowest proteoglycan content, and collagen fibrils oriented parallel to the joint surface to resist shear forces.

Question 13576

Topic: Biology, Genetics & Bone Healing

Denosumab has revolutionized the medical management of unresectable or locally advanced Giant Cell Tumors of bone. What is the specific cellular mechanism of action of this monoclonal antibody?

. It directly binds to and inhibits the RANK receptor on the surface of osteoclast-like giant cells
. It binds and neutralizes RANK ligand (RANKL) secreted by the neoplastic mononuclear stromal cells
. It stimulates osteoprotegerin (OPG) production, competitively inhibiting osteoclastic activity
. It directly induces apoptosis of the multinucleated giant cells via the caspase-3 pathway
. It inhibits matrix metalloproteinases (MMPs) within the tumor microenvironment

Correct Answer & Explanation

. It binds and neutralizes RANK ligand (RANKL) secreted by the neoplastic mononuclear stromal cells

Explanation

Giant Cell Tumor (GCT) of bone consists of neoplastic mononuclear stromal cells that express high levels of RANK Ligand (RANKL), which recruits and activates normal multinucleated giant cells (osteoclasts) that cause the massive bone destruction seen in the tumor. Denosumab is a fully human monoclonal antibody that binds directly to RANKL, preventing it from binding to the RANK receptor on osteoclast precursors. This effectively halts osteoclast activation and bone destruction.

Question 13577

Topic: 1. General Principles & Basic Science

In the principles of orthopedic internal fixation, the pull-out strength of a cortical bone screw is most significantly and directly proportional to which of the following screw characteristics?

. Inner (core) diameter
. Outer (thread) diameter
. Pitch
. Thread count per inch
. Flute angle

Correct Answer & Explanation

. Outer (thread) diameter

Explanation

The pull-out strength of a bone screw is a measure of its resistance to being pulled out of the bone axially. The primary formula for pull-out strength incorporates the shear strength of the bone, the length of thread engagement, and the outer diameter of the screw. Therefore, increasing the outer diameter directly and linearly increases the pull-out strength. The core diameter determines the bending strength of the screw, not the pull-out strength.

Question 13578

Topic: 1. General Principles & Basic Science

In which zone of mature articular cartilage are the collagen fibers oriented perpendicular to the joint surface and the proteoglycan concentration highest?

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

Correct Answer & Explanation

. Deep (radial) zone

Explanation

The deep (radial) zone of articular cartilage contains collagen fibers that are oriented perpendicular to the articular surface. This zone provides the greatest resistance to compressive forces because it contains the highest concentration of proteoglycans and the lowest concentration of water.

Question 13579

Topic: 1. General Principles & Basic Science

The primary blood supply to the adult femoral head is derived from the medial circumflex femoral artery (MCFA). Which specific branch of the MCFA is the main contributor to the weight-bearing dome?

. Anterior ascending artery
. Lateral epiphyseal artery
. Inferior metaphyseal artery
. Acetabular branch of the obturator artery
. Superior gluteal artery

Correct Answer & Explanation

. Lateral epiphyseal artery

Explanation

The lateral epiphyseal artery, a terminal branch of the medial circumflex femoral artery (MCFA), provides the vast majority of the blood supply to the weight-bearing dome of the adult femoral head.

Question 13580

Topic: Infection, Pharmacology & VTE

During a total knee arthroplasty for a severe varus deformity, the knee is found to be tight medially in both flexion and extension. After releasing the deep medial collateral ligament (MCL), what is the next appropriate step in the medial soft tissue release sequence?

. Superficial MCL release off the tibia
. Posteromedial corner and capsule release
. Pes anserinus release
. Medial head of the gastrocnemius release
. Semimembranosus release

Correct Answer & Explanation

. Posteromedial corner and capsule release

Explanation

In a varus knee, the standard sequential medial release to balance both the flexion and extension gaps starts with osteophyte removal and deep MCL release. If the knee remains tight in both flexion and extension, the next structure released is the posteromedial corner and capsule, followed by the superficial MCL, and finally the pes anserinus if further balancing is required.

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