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1. General Principles & Basic Science MCQs

Practice Set 62 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 1221

Topic: 1. General Principles & Basic Science

In obstetric brachial plexus injury, return of which of the following muscle by 3 months is considered an indicator of plexus recovery:

. Biceps
. Triceps
. Brachioradialis
. Latissimus

Correct Answer & Explanation

. Biceps

Explanation

Biceps recovery at 3 months is considered the single most important indicator of recovery in obstetric plexus palsy.

Question 1222

Topic: Biology, Genetics & Bone Healing
Which type of collagen is the predominant structural protein synthesized by hypertrophic chondrocytes during the endochondral ossification phase of fracture healing?
. Type I collagen
. Type II collagen
. Type III collagen
. Type IV collagen
. Type X collagen

Correct Answer & Explanation

. Type X collagen

Explanation

Hypertrophic chondrocytes specifically synthesize Type X collagen during endochondral ossification. This marks the transition from cartilage matrix production to calcification and subsequent bone formation.

Question 1223

Topic: Biomechanics & Biomaterials

Galvanic corrosion in orthopedic implants occurs when two dissimilar metals are placed in physical contact within a conductive fluid environment. Which of the following metal combinations carries the highest risk of significant galvanic corrosion?

. Titanium alloy and Cobalt-Chromium alloy
. Stainless steel and Titanium alloy
. Cobalt-Chromium alloy and Zirconium
. Tantalum and Titanium alloy
. Stainless steel and Cobalt-Chromium alloy

Correct Answer & Explanation

. Stainless steel and Cobalt-Chromium alloy

Explanation

Mixing stainless steel with titanium or cobalt-chromium alloys creates a strong galvanic cell due to significant differences in their electrochemical potentials. This combination is generally avoided in orthopedic surgery to prevent accelerated corrosion and subsequent implant failure.

Question 1224

Topic: Surgical Anatomy & Approaches

During an ilioinguinal approach to the acetabulum, massive bleeding is encountered near the posterior aspect of the superior pubic ramus. This is most likely due to an injury of the corona mortis, which is an anastomotic vessel connecting the external iliac system to which of the following arteries?

. Internal pudendal artery
. Superior gluteal artery
. Obturator artery
. Inferior gluteal artery
. Femoral artery

Correct Answer & Explanation

. Obturator artery

Explanation

The corona mortis is a vascular anastomosis between the external iliac (or inferior epigastric) and obturator vessels. It is located on the posterior aspect of the superior pubic ramus and is at high risk during anterior pelvic approaches.

Question 1225

Topic: Biology, Genetics & Bone Healing

A 32-year-old female presents with an expansile lytic lesion in the distal femur. Biopsy confirms a Giant Cell Tumor of bone. She is prescribed denosumab prior to surgery. What is the mechanism of action of this medication?

. Inhibits VEGF to decrease tumor vascularity
. Binds to RANKL to inhibit osteoclast-like giant cell formation
. Directly induces apoptosis of mononuclear neoplastic cells
. Inhibits matrix metalloproteinases to prevent local invasion
. Stimulates osteoblast differentiation via BMP-2 pathways

Correct Answer & Explanation

. Binds to RANKL to inhibit osteoclast-like giant cell formation

Explanation

Denosumab is a human monoclonal antibody that binds to RANKL, preventing its interaction with the RANK receptor on osteoclasts and giant cells. This effectively halts the severe osteolysis characteristic of Giant Cell Tumors.

Question 1226

Topic: 1. General Principles & Basic Science

In articular cartilage, which zone contains the highest concentration of proteoglycans and chondrocytes that are oriented perpendicular to the articular surface?

. Superficial zone
. Transitional (Middle) zone
. Deep zone
. Calcified cartilage zone
. Subchondral bone plate

Correct Answer & Explanation

. Deep zone

Explanation

The deep zone of articular cartilage contains the highest concentration of proteoglycans and the lowest water content. The collagen fibers and chondrocytes in this zone are arranged perpendicular to the articular surface to effectively resist compressive forces.

Question 1227

Topic: Biology, Genetics & Bone Healing

Bone morphogenetic proteins (BMPs) play a crucial role in bone healing via osteoinduction. Which of the following BMPs is an FDA-approved recombinant agent commonly used to enhance anterior lumbar interbody fusion (ALIF)?

. BMP-1
. BMP-2
. BMP-4
. BMP-6
. BMP-12

Correct Answer & Explanation

. BMP-2

Explanation

Recombinant human BMP-2 (rhBMP-2) is heavily utilized and FDA-approved for specific applications, including anterior lumbar interbody fusion (ALIF) and acute open tibial shaft fractures, due to its potent osteoinductive capabilities.

Question 1228

Topic: Biology, Genetics & Bone Healing

Bone morphogenetic protein-2 (BMP-2) promotes osteoblast differentiation and bone formation primarily by binding to cell membrane receptors and activating which of the following intracellular signaling pathways?

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

Correct Answer & Explanation

. Smad 1/5/8

Explanation

BMPs bind to serine/threonine kinase receptors on the cell membrane, which subsequently phosphorylate and activate the intracellular Smad 1/5/8 pathway to upregulate osteogenic transcription factors like Runx2.

Question 1229

Topic: 1. General Principles & Basic Science

The optimal position for hallux interphalangeal joint arthrodesis is:

. 5° to 10° of plantarflexion
. 5° to 10° of dorsiflexion
. Neutral flexion
. Slight supination of the toe
. 10° of valgus

Correct Answer & Explanation

. 5° to 10° of plantarflexion

Explanation

The optimal position for hallux interphalangeal joint arthrodesis is 5° to 10° of plantarflexion, neutral varus-valgus, and neutral rotation. The plantarflexion helps the toe pad to contact the ground during gait.

Question 1230

Topic: 1. General Principles & Basic Science
Which nerve is NOT one of the terminal branches of Baxter's nerve, also known as the first branch of the lateral plantar nerve:
. Nerve to the medial calcaneal periosteum (sensory)
. Lateral dorsal cutaneous nerve (sensory)
. Nerve to the flexor digitorum brevis muscle (motor)
. Nerve to the abductor digiti minimi muscle (motor)
. None of the above

Correct Answer & Explanation

. Lateral dorsal cutaneous nerve (sensory)

Explanation

The three terminal branches of Baxter's nerve are the nerve to the medial calcaneal periosteum, the nerve to the flexor digitorum brevis, and the nerve to the abductor digiti minimi. The lateral dorsal cutaneous nerve is a branch of the sural nerve.

Question 1231

Topic: 1. General Principles & Basic Science

Exposure of tendons to ciprofloxacin in vitro causes all of the following except:

. A decrease in fibroblast proliferation
. An increase in proteoglycan synthesis
. A decrease in proteoglycan synthesis
. An increase in matrix degrading proteolytic activity
. A decrease in collagen synthesis

Correct Answer & Explanation

. A decrease in fibroblast proliferation

Explanation

Ciprofloxacin was shown to cause a decrease in fibroblast proliferation, proteoglycan synthesis, and collagen synthesis. Matrix degrading proteolytic activity was increased.

Question 1232

Topic: 1. General Principles & Basic Science
In children between ages 7 and 11 with bilateral flexible flatfeet and without any pathologic findings, the use of custom-made orthotics or off-the-shelf orthotics demonstrate:
. Significant improvement in motor proficiency compared to controls treated without orthotics
. Significant improvement in visual analog pain scores compared to controls treated without orthotics
. Significant improvement in exercise efficiency compared to controls treated without orthotics
. Significant negative effects on the child's self-perception compared to controls treated without orthotics
. No significant difference compared to controls with regards to motor proficiency, pain, exercise efficiency, or self-perception

Correct Answer & Explanation

. No significant difference compared to controls with regards to motor proficiency, pain, exercise efficiency, or self-perception

Explanation

In a randomized controlled trial comparing children with flatfeet treated with custom orthotics, off-the-shelf orthotics, and no treatment, there were no differences in the above parameters found. The study concluded that no significant difference was found with regard to motor proficiency, pain, exercise efficiency, or self-perception.

Question 1233

Topic: Biology, Genetics & Bone Healing
During the remodeling phase of fracture healing, woven bone is replaced by lamellar bone. Which type of collagen is the predominant organic component of the extracellular matrix in mature lamellar bone?
. Type I
. Type II
. Type III
. Type IV
. Type X

Correct Answer & Explanation

. Type I

Explanation

Type I collagen makes up roughly 90% of the organic matrix of mature bone. It provides tensile strength and serves as the primary scaffolding for mineralization.

Question 1234

Topic: 1. General Principles & Basic Science

Which of the following rehabilitation principles is most universally recommended over absolute immobilization following a Zone II flexor tendon repair to optimize outcomes and prevent adhesions?

. Absolute immobilization for a minimum of 6 weeks
. Early active or controlled passive motion protocols
. Continuous passive motion machine for 24 hours/day
. Serial casting every 2 weeks
. Immediate return to full heavy lifting at 2 weeks

Correct Answer & Explanation

. Early active or controlled passive motion protocols

Explanation

Early active or controlled passive motion (e.g., modified Duran or Kleinert protocols) enhances intrinsic tendon healing and prevents restrictive adhesion formation. Immobilization leads to poor functional results.

Question 1235

Topic: 1. General Principles & Basic Science

Tranexamic acid (TXA) is now routinely used to reduce blood loss in total joint arthroplasty. What is its primary biochemical mechanism of action?

. Inhibits factor Xa in the intrinsic pathway
. Directly inhibits thrombin generation
. Binds reversibly to plasminogen to prevent fibrin degradation
. Promotes primary platelet aggregation
. Activates the extrinsic coagulation cascade

Correct Answer & Explanation

. Binds reversibly to plasminogen to prevent fibrin degradation

Explanation

Tranexamic acid is a synthetic analog of the amino acid lysine. It competitively inhibits the activation of plasminogen to plasmin, thereby preventing the degradation of fibrin clots (antifibrinolytic effect).

Question 1236

Topic: Physiology & Rehabilitation

Compared to operative management of acute Achilles tendon ruptures, recent level I evidence regarding non-operative management utilizing early functional rehabilitation demonstrates:

. Higher deep vein thrombosis rates in non-operative patients
. Lower rates of wound complications and infections
. Significantly higher re-rupture rates (>20%)
. Decreased range of motion at 1 year post-injury
. Improved peak isokinetic plantar flexion strength

Correct Answer & Explanation

. Lower rates of wound complications and infections

Explanation

Recent trials utilizing early functional rehabilitation show similar re-rupture rates and functional outcomes between operative and non-operative management. However, non-operative management avoids the wound healing complications and infection risks associated with surgery.

Question 1237

Topic: Biomechanics & Biomaterials

During surgical repair of a Zone II flexor digitorum profundus (FDP) laceration, which of the following pulleys is most critical to preserve or reconstruct to prevent bowstringing of the tendon?

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

Correct Answer & Explanation

. A2 and A4

Explanation

The A2 and A4 pulleys arise from the proximal and middle phalanges, respectively, and are the most mechanically important pulleys. Preserving or reconstructing them is critical to prevent bowstringing and ensure proper flexor tendon kinematics.

Question 1238

Topic: Biology, Genetics & Bone Healing
Which type of collagen is predominantly synthesized by chondrocytes during the soft callus phase of secondary fracture healing?
. Type I collagen
. Type II collagen
. Type III collagen
. Type IV collagen
. Type X collagen

Correct Answer & Explanation

. Type II collagen

Explanation

During the soft callus phase of secondary fracture healing, endochondral ossification occurs where chondrocytes primarily synthesize Type II collagen. As the callus calcifies, hypertrophic chondrocytes express Type X collagen before bone (Type I) is deposited.

Question 1239

Topic: 1. General Principles & Basic Science

Which zone of the meniscus has the highest healing potential following repair, and what is its primary blood supply?

. White-white zone; Genicular arteries
. Red-white zone; Popliteal artery
. Red-red zone; Middle genicular artery
. Red-red zone; Medial and lateral inferior genicular arteries
. White-white zone; Middle genicular artery

Correct Answer & Explanation

. Red-red zone; Medial and lateral inferior genicular arteries

Explanation

The peripheral third (red-red zone) of the meniscus is highly vascularized and has excellent healing potential. It receives its blood supply from a perimeniscal capillary plexus originating from the medial and lateral genicular arteries.

Question 1240

Topic: 1. General Principles & Basic Science

Which of the following local anesthetics has the longest duration of action and blocks neural transmission by binding to the intracellular portion of voltage-gated sodium channels?

. Lidocaine
. Mepivacaine
. Bupivacaine
. Chloroprocaine
. Articaine

Correct Answer & Explanation

. Bupivacaine

Explanation

Bupivacaine is an amide local anesthetic notable for its high protein binding, conferring a long duration of action. Like all local anesthetics, it crosses the neural membrane and blocks voltage-gated sodium channels from the inside.

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