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1. General Principles & Basic Science MCQs

Practice Set 215 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 4281

Topic: 1. General Principles & Basic Science

A surgeon performs a cross-finger flap from the dorsum of the middle finger to reconstruct a volar soft tissue defect exposing the flexor tendon on the index finger. What is the most appropriate management of the donor site on the dorsum of the middle finger?

. Primary closure by wide undermining
. Split-thickness skin graft over bare bone
. Full-thickness skin graft over preserved paratenon
. Healing by secondary intention
. Coverage with a local rotational flap

Correct Answer & Explanation

. Full-thickness skin graft over preserved paratenon

Explanation

When elevating a cross-finger flap from the dorsum of a donor digit, it is essential to leave the paratenon overlying the extensor tendon intact. The resulting donor site defect is then typically covered with a full-thickness (or thick split-thickness) skin graft placed directly onto the vascularized paratenon. Attempting to graft over bare tendon will result in graft failure and tendon desiccation.

Question 4282

Topic: Biology, Genetics & Bone Healing

During surgery for a highly comminuted intra-articular distal radius fracture, the surgeon utilizes an osteoconductive bone graft substitute to fill a large metaphyseal void. Which of the following best defines the primary mechanism of osteoconduction?

. Recruitment of mesenchymal stem cells via BMPs
. Providing a physical scaffold for host bone ingrowth
. Supplying viable osteoblasts to the defect site
. Inducing a sterile inflammatory response to stimulate angiogenesis
. Generating a piezoelectric effect under mechanical load

Correct Answer & Explanation

. Providing a physical scaffold for host bone ingrowth

Explanation

Bone graft properties are divided into osteoconduction, osteoinduction, and osteogenesis. Osteoconduction refers to the material's ability to act as a 3D physical scaffold or matrix for creeping substitution and ingrowth of host capillaries and osteoprogenitor cells. Osteoinduction (e.g., BMPs) recruits and stimulates cells to become osteoblasts. Osteogenesis (e.g., fresh autograft) directly supplies living bone-forming cells.

Question 4283

Topic: Surgical Anatomy & Approaches

A structural tricortical bone graft is harvested from the anterior iliac crest to reconstruct a scaphoid nonunion. Postoperatively, the patient reports significant numbness and a burning sensation over the anterolateral aspect of his thigh. Which nerve was most likely injured during the graft harvest?

. Ilioinguinal nerve
. Iliohypogastric nerve
. Lateral femoral cutaneous nerve
. Femoral nerve
. Genitofemoral nerve

Correct Answer & Explanation

. Lateral femoral cutaneous nerve

Explanation

The lateral femoral cutaneous nerve (LFCN) is at risk during anterior iliac crest bone graft harvest. It typically exits the pelvis under the inguinal ligament approximately 1-2 cm medial to the anterior superior iliac spine (ASIS). Injury to the LFCN results in meralgia paresthetica, characterized by pain, burning, and numbness over the anterolateral thigh. Staying at least 2-3 cm posterior to the ASIS during harvest minimizes this risk.

Question 4284

Topic: 1. General Principles & Basic Science
A 35-year-old male undergoes a flexor tendon repair using the wide-awake local anesthesia no tourniquet (WALANT) technique. The surgeon injects a mixture of lidocaine and epinephrine. Forty-five minutes later, the patient's digit appears excessively pale, and the surgeon decides to reverse the vasoconstriction. Which of the following describes the mechanism of action of the most appropriate rescue agent?
. Non-selective beta-adrenergic receptor agonist
. Selective alpha-1 adrenergic receptor agonist
. Non-selective alpha-adrenergic receptor antagonist
. Direct smooth muscle relaxant via nitric oxide donation
. Selective beta-2 adrenergic receptor antagonist

Correct Answer & Explanation

. Non-selective alpha-adrenergic receptor antagonist

Explanation

The rescue agent for epinephrine-induced digital ischemia is phentolamine. Phentolamine is a competitive, non-selective alpha-adrenergic receptor antagonist (blocking both alpha-1 and alpha-2 receptors). It effectively reverses the alpha-receptor-mediated vasoconstriction caused by epinephrine, restoring blood flow to the digit.

Question 4285

Topic: 1. General Principles & Basic Science

When utilizing cortical bone autograft for structural reconstruction in the upper extremity, it undergoes incorporation via a process known as creeping substitution. At approximately what time point post-implantation is a cortical autograft mechanically at its weakest?

. 2 to 4 weeks
. 6 to 12 months
. 18 to 24 months
. 3 to 5 years
. It maintains consistent mechanical strength throughout the incorporation process

Correct Answer & Explanation

. 6 to 12 months

Explanation

Cortical autograft heals by creeping substitution, where osteoclasts first resorb the bone (cutting cones) followed by osteoblasts laying down new bone. This initial resorptive phase increases graft porosity, making the cortical autograft mechanically weakest between 6 months and 1 year after implantation. It may take 1 to 2 years to regain its structural integrity.

Question 4286

Topic: Biomechanics & Biomaterials

A surgeon chooses to use calcium phosphate cement to fill a metaphyseal void following the reduction of a distal radius fracture. Which of the following correctly describes a biomechanical or physical property of calcium phosphate cement?

. It cures via an endothermic reaction, protecting surrounding tissue
. It provides high tensile and shear strength
. It is rapidly resorbed within 4 to 6 weeks, matching the rate of new bone formation
. It cures via an exothermic reaction and provides high compressive strength
. It is primarily osteoinductive, promoting cell differentiation

Correct Answer & Explanation

. It cures via an exothermic reaction and provides high compressive strength

Explanation

Calcium phosphate cement cures in vivo via an exothermic reaction into a hydroxyapatite-like structure. It is highly osteoconductive and provides excellent compressive strength (equivalent to or greater than cancellous bone), making it ideal for filling metaphyseal voids. However, it lacks tensile/shear strength and resorbs very slowly (often taking years), unlike calcium sulfate which resorbs rapidly.

Question 4287

Topic: Biology, Genetics & Bone Healing
Bone morphogenetic proteins (BMPs) are commonly used as osteoinductive agents in bone grafting procedures. At the cellular level, BMPs initiate signal transduction by binding to cell surface receptors that possess which of the following intrinsic enzymatic activities?
. Tyrosine kinase
. Serine/threonine kinase
. Guanylyl cyclase
. Phospholipase C
. Adenylyl cyclase

Correct Answer & Explanation

. Serine/threonine kinase

Explanation

Bone morphogenetic proteins (BMPs) are members of the transforming growth factor-beta (TGF-β) superfamily. They bind to Type I and Type II transmembrane receptors that possess intrinsic serine/threonine kinase activity. Once activated, these receptors phosphorylate downstream intracellular signaling molecules called Smads (typically Smad 1, 5, and 8), which then translocate to the nucleus to regulate gene transcription.

Question 4288

Topic: Biology, Genetics & Bone Healing
Following primary repair of an acute Zone II flexor tendon laceration, the healing tendon progresses through inflammatory, fibroblastic, and remodeling phases. During the fibroblastic (proliferation) phase, which collagen type is predominantly synthesized initially by fibroblasts before being gradually replaced in the remodeling phase?
. Type I collagen
. Type II collagen
. Type III collagen
. Type IV collagen
. Type IX collagen

Correct Answer & Explanation

. Type III collagen

Explanation

Tendon healing in the initial fibroblastic (proliferative) phase, which spans approximately days 5 to 28, is characterized by the production of Type III collagen. This forms a disorganized, mechanically weak matrix. During the subsequent remodeling phase, this Type III collagen is gradually replaced by the stronger, longitudinally oriented Type I collagen, increasing the tendon's tensile strength.

Question 4289

Topic: Biomechanics & Biomaterials

A surgeon incorporates calcium sulfate pellets as a bone graft substitute to fill a benign bone cyst defect in the hand. Three weeks postoperatively, the patient presents with non-purulent, serous drainage from the wound. Inflammatory markers are normal and cultures are negative. What is the most likely cause of this drainage?

. Exothermic necrosis of surrounding soft tissue during setting
. Allergic reaction to the carrier matrix
. Rapid dissolution of calcium sulfate leading to a hyperosmotic serous effusion
. Undiagnosed low-grade mycobacterial infection
. Premature weight-bearing causing micromotion and inflammatory exudate

Correct Answer & Explanation

. Rapid dissolution of calcium sulfate leading to a hyperosmotic serous effusion

Explanation

Calcium sulfate is an osteoconductive bone graft substitute known for its very rapid absorption rate, which often outpaces new bone formation. Its dissolution can create a localized hyperosmotic environment, drawing fluid into the area and resulting in a sterile, serous wound exudate in up to 30% of patients. It does not set with an exothermic reaction (unlike calcium phosphate or PMMA).

Question 4290

Topic: 1. General Principles & Basic Science
In the process of Wallerian degeneration following a severe peripheral nerve injury in the upper extremity, the distal nerve segment undergoes organized cellular changes to prepare for potential regenerating axons. Which specialized cells are primarily responsible for clearing myelin debris and subsequently proliferating to form the parallel arrays known as 'Bands of Büngner'?
. Fibroblasts
. Macrophages
. Schwann cells
. Astrocytes
. Oligodendrocytes

Correct Answer & Explanation

. Schwann cells

Explanation

During Wallerian degeneration of the distal nerve stump, Schwann cells (along with recruited macrophages) play a critical role in clearing axonal and myelin debris. Subsequently, these Schwann cells proliferate and align longitudinally within the preserved endoneurial tubes to form the Bands of Büngner, which act as a biologic guide to direct regenerating axonal sprouts.

Question 4291

Topic: Surgical Anatomy & Approaches

During the surgical management of an anterior pelvic ring injury via an ilioinguinal approach, the surgeon encounters significant hemorrhage over the superior pubic ramus. This is most likely originating from the corona mortis, an anastomotic vascular connection typically linking which two vessel systems?

. Femoral artery and internal iliac artery
. External iliac system and obturator system
. Internal pudendal artery and inferior gluteal artery
. Superior gluteal artery and internal iliac artery
. Inferior epigastric artery and femoral vein

Correct Answer & Explanation

. External iliac system and obturator system

Explanation

The corona mortis ('crown of death') is a vascular anastomosis between the external iliac (or inferior epigastric) vessels and the internal iliac (obturator) vessels. It is located on the posterior aspect of the superior pubic ramus, approximately 5 cm from the pubic symphysis, and can cause life-threatening hemorrhage if inadvertently disrupted during anterior pelvic ring surgery.

Question 4292

Topic: Infection, Pharmacology & VTE

A surgeon is utilizing a posteromedial approach to internally fix a complex shear fracture of the medial tibial plateau. To correctly perform the deep dissection and avoid damaging vital structures, the internervous/intermuscular interval should be developed between which of the following structures?

. Semimembranosus and semitendinosus
. Medial head of the gastrocnemius and the pes anserinus
. Soleus and popliteus
. Tibialis posterior and flexor digitorum longus
. Sartorius and gracilis

Correct Answer & Explanation

. Medial head of the gastrocnemius and the pes anserinus

Explanation

The posteromedial approach to the proximal tibia utilizes an intermuscular interval between the medial head of the gastrocnemius (which is retracted laterally/posteriorly to protect the neurovascular bundle) and the pes anserinus tendons (semitendinosus, gracilis, and sartorius, which are retracted medially/anteriorly). The semimembranosus tendon lies deep and must be carefully managed in this plane.

Question 4293

Topic: Surgical Anatomy & Approaches

The direct anterior approach (DAA) to the hip is popular for its theoretical advantage of utilizing a true internervous and intermuscular plane. The superficial surgical interval in the DAA is between muscles supplied by which two nerves?

. Femoral nerve and Obturator nerve
. Femoral nerve and Superior gluteal nerve
. Superior gluteal nerve and Inferior gluteal nerve
. Sciatic nerve and Femoral nerve
. Obturator nerve and Sciatic nerve

Correct Answer & Explanation

. Femoral nerve and Superior gluteal nerve

Explanation

The direct anterior approach (Smith-Petersen) exploits the internervous plane between the sartorius (innervated by the femoral nerve) and the tensor fasciae latae (innervated by the superior gluteal nerve) superficially. Deep to this, the interval is between the rectus femoris (femoral nerve) and the gluteus medius/minimus (superior gluteal nerve).

Question 4294

Topic: Surgical Anatomy & Approaches

During an ilioinguinal approach for a transverse acetabular fracture, significant arterial hemorrhage occurs near the superior pubic ramus. The bleeding is most likely originating from an anastomosis between which two vessels?

. External iliac artery and internal pudendal artery
. Superior gluteal artery and inferior epigastric artery
. Internal iliac artery and superior gluteal artery
. External iliac vein and femoral vein
. Inferior epigastric artery and obturator artery

Correct Answer & Explanation

. Inferior epigastric artery and obturator artery

Explanation

This anastomosis is known as the corona mortis (crown of death). It is a vascular connection between the inferior epigastric (or external iliac) and obturator vessels, crossing the superior pubic ramus where it is vulnerable during pelvic surgery.

Question 4295

Topic: Biology, Genetics & Bone Healing

A 70-year-old female on alendronate for 8 years presents with vague thigh pain. Radiographs reveal a thickened lateral cortex with a transverse radiolucent line in the subtrochanteric region of her femur. What is the most appropriate prophylactic surgical management?

. Discontinuation of alendronate and strict non-weight bearing
. Prophylactic dynamic hip screw fixation
. Prophylactic cephalomedullary nailing
. Prophylactic plating with a locking compression plate
. External beam radiation and teriparatide therapy

Correct Answer & Explanation

. Prophylactic cephalomedullary nailing

Explanation

This patient has an impending atypical femur fracture associated with long-term bisphosphonate use. The gold standard surgical management for a symptomatic, impending atypical subtrochanteric fracture is full-length intramedullary nailing (cephalomedullary nail).

Question 4296

Topic: Surgical Anatomy & Approaches

The direct anterior (Smith-Petersen) approach for total hip arthroplasty utilizes a true internervous plane between which of the following muscle groups?

. Sartorius (Femoral n.) and Tensor fasciae latae (Superior gluteal n.)
. Rectus femoris (Femoral n.) and Iliacus (Femoral n.)
. Gluteus maximus (Inferior gluteal n.) and Gluteus medius (Superior gluteal n.)
. Pectineus (Femoral/Obturator n.) and Adductor longus (Obturator n.)
. Tensor fasciae latae (Superior gluteal n.) and Gluteus medius (Superior gluteal n.)

Correct Answer & Explanation

. Sartorius (Femoral n.) and Tensor fasciae latae (Superior gluteal n.)

Explanation

The direct anterior approach utilizes the internervous and intermuscular plane between the sartorius (femoral nerve) and the tensor fasciae latae (superior gluteal nerve) superficially, and the rectus femoris (femoral nerve) and gluteus medius (superior gluteal nerve) deep.

Question 4297

Topic: Biomechanics & Biomaterials
In total hip arthroplasty, the use of highly cross-linked polyethylene (HXLPE) compared to conventional ultra-high molecular weight polyethylene (UHMWPE) alters the wear profile. Which of the following trade-offs is most characteristic of increasing the radiation dose during HXLPE manufacturing?
. Increased wear rate and increased fatigue strength
. Decreased wear rate and decreased fatigue strength
. Decreased wear rate and increased oxidation potential
. Increased wear rate and increased oxidation potential
. No change in wear rate but decreased fatigue strength

Correct Answer & Explanation

. Decreased wear rate and decreased fatigue strength

Explanation

Highly cross-linking polyethylene significantly decreases the volumetric wear rate, lowering the risk of osteolysis. However, it inversely decreases the material's mechanical properties, such as fatigue strength and fracture toughness.

Question 4298

Topic: Surgical Anatomy & Approaches

What is the most common neurologic complication following a reverse total shoulder arthroplasty (RSA) for rotator cuff arthropathy, and what is its most common mechanism?

. Axillary nerve palsy due to retractor compression or overstretching
. Suprascapular nerve palsy due to over-lengthening
. Musculocutaneous nerve palsy due to anterior escape
. Radial nerve palsy due to cement extrusion
. Spinal accessory nerve palsy due to patient positioning

Correct Answer & Explanation

. Axillary nerve palsy due to retractor compression or overstretching

Explanation

Axillary nerve neurapraxia is the most common neurologic complication following RSA. It typically results from overstretching during inferior capsular release or direct retractor compression at the inferior glenoid neck.

Question 4299

Topic: Surgical Anatomy & Approaches

A 40-year-old laborer undergoes an open subpectoral biceps tenodesis. Postoperatively, he presents with profound weakness in wrist extension, finger extension, and numbness over the dorsal web space of the hand. Which of the following technical errors most likely occurred during the procedure?

. Retractor placement too far superior and lateral
. Retractor placement too deep and medial, penetrating the coracobrachialis
. Drill bit plunging through the posterior cortex of the humerus
. Excessive distal traction on the biceps tendon
. Entrapment of the musculocutaneous nerve in the interference screw

Correct Answer & Explanation

. Drill bit plunging through the posterior cortex of the humerus

Explanation

The radial nerve runs posterior to the humerus in the spiral groove and is at risk if a drill plunges through the posterior cortex during a subpectoral biceps tenodesis (especially with bicortical button fixation). Deficits in wrist/finger extension and dorsal web space numbness are classic for a radial nerve injury. Medial retractor placement endangers the musculocutaneous nerve.

Question 4300

Topic: 1. General Principles & Basic Science

A 28-year-old male bodybuilder feels a tearing sensation in his anterior axilla while bench-pressing. Physical examination reveals a loss of the anterior axillary fold. MRI confirms a complete rupture of the sternocostal head of the pectoralis major. Where does the sternocostal head normally insert on the humerus relative to the clavicular head?

. Proximal and anterior
. Proximal and posterior (deep)
. Distal and anterior
. Distal and posterior
. Directly medial to the clavicular head

Correct Answer & Explanation

. Proximal and posterior (deep)

Explanation

The pectoralis major tendon twists 90 degrees before inserting on the lateral lip of the bicipital groove. The clavicular head inserts distally and anteriorly, while the sternocostal head twists to insert proximally and posteriorly (deep) to the clavicular head insertion. The sternocostal head is most commonly torn during the eccentric phase of heavy lifting.

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