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Surgical Anatomy & Approaches MCQs

Practice Set 60 of 102

This practice set contains high-yield board review questions covering key concepts in Surgical Anatomy & Approaches. Each clinical scenario is designed to test your diagnostic and management skills relevant to this subspecialty.

Question 1181

Topic: Surgical Anatomy & Approaches

During resection of a soft tissue sarcoma in the proximal thigh, the surgeon carefully traces the femoral nerve. Which of the following muscles is primarily innervated by a branch of the femoral nerve despite functioning as a medial compartment adductor?

. Adductor longus
. Gracilis
. Pectineus
. Adductor magnus
. Obturator externus

Correct Answer & Explanation

. Pectineus

Explanation

The pectineus muscle is anatomically located in the medial (adductor) compartment of the thigh but is predominantly innervated by the femoral nerve. It functions primarily to flex and adduct the thigh.

Question 1182

Topic: Surgical Anatomy & Approaches

During a deltopectoral approach to the shoulder, the cephalic vein is identified. It is typically retracted laterally with the deltoid to preserve its major tributaries. If the dissection proceeds too aggressively medial to the conjoined tendon, which of the following nerves is at greatest risk of direct injury?

. Axillary nerve
. Musculocutaneous nerve
. Radial nerve
. Long thoracic nerve
. Suprascapular nerve

Correct Answer & Explanation

. Musculocutaneous nerve

Explanation

The musculocutaneous nerve enters the coracobrachialis approximately 5 to 8 cm distal to the coracoid process. Retracting the conjoined tendon too vigorously or dissecting medial to it places this nerve at significant risk for neuropraxia or laceration.

Question 1183

Topic: Surgical Anatomy & Approaches

A trauma surgeon is performing an ilioinguinal approach for an anterior column acetabular fracture. While working in the second (middle) window, massive acute hemorrhage occurs. Which of the following vascular structures is the most likely source of this bleeding?

. Superior gluteal artery
. Corona mortis
. Internal pudendal artery
. Inferior gluteal artery
. Lateral femoral circumflex artery

Correct Answer & Explanation

. Corona mortis

Explanation

The second window of the ilioinguinal approach lies between the iliopectineal fascia and the external iliac vessels. The corona mortis, a highly variable arterial or venous anastomosis between the external iliac and obturator systems, traverses over the superior pubic ramus here.

Question 1184

Topic: Surgical Anatomy & Approaches

The anterolateral approach to the distal humerus is often utilized for fracture fixation, requiring exposure and protection of the radial nerve. At what approximate distance proximal to the radiocapitellar joint does the radial nerve pierce the lateral intermuscular septum to enter the anterior compartment?

. 3 - 5 cm
. 10 - 12 cm
. 15 - 17 cm
. 18 - 20 cm
. 22 - 25 cm

Correct Answer & Explanation

. 10 - 12 cm

Explanation

The radial nerve pierces the lateral intermuscular septum approximately 10 to 12 cm proximal to the lateral epicondyle (and radiocapitellar joint). This anatomic landmark is essential when extending the approach proximally.

Question 1185

Topic: Surgical Anatomy & Approaches

During an anterior (Smith-Petersen) approach to the hip, a true internervous plane is utilized. Proximally, this surgical interval is developed between muscles innervated by which two nerves?

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

Correct Answer & Explanation

. Femoral nerve and Superior gluteal nerve

Explanation

The proximal internervous plane for the Smith-Petersen approach is between the sartorius (innervated by the femoral nerve) and the tensor fasciae latae (innervated by the superior gluteal nerve). Distally, the plane falls between the rectus femoris and gluteus medius.

Question 1186

Topic: Surgical Anatomy & Approaches

A 22-year-old rugby player undergoes an open Latarjet procedure for recurrent anterior shoulder instability with 25% glenoid bone loss. Postoperatively, he presents with profound weakness with shoulder abduction and absent sensation over the lateral aspect of the shoulder. Which nerve was most likely injured, and what is its pertinent anatomic relationship during the procedure?

. Axillary nerve, passing inferior to the subscapularis and shoulder capsule
. Musculocutaneous nerve, entering the conjoint tendon distally
. Suprascapular nerve, passing through the spinoglenoid notch
. Radial nerve, passing through the triangular interval
. Spinal accessory nerve, coursing deep to the trapezius

Correct Answer & Explanation

. Axillary nerve, passing inferior to the subscapularis and shoulder capsule

Explanation

The patient's presentation of deltoid weakness and lateral shoulder numbness indicates an axillary nerve injury. During a Latarjet procedure, the axillary nerve is at risk during the inferior capsular release and subscapularis split/tenotomy, as it courses closely inferior to the subscapularis and capsule to enter the quadrangular space.

Question 1187

Topic: Surgical Anatomy & Approaches

A 22-year-old professional rugby player undergoes a Latarjet procedure for recurrent anterior shoulder instability with 25% glenoid bone loss. Postoperatively, he exhibits weakness in initiating shoulder abduction and decreased sensation over the lateral aspect of the proximal arm. Which nerve was most likely injured during the procedure?

. Musculocutaneous nerve
. Axillary nerve
. Suprascapular nerve
. Radial nerve
. Median nerve

Correct Answer & Explanation

. Axillary nerve

Explanation

The axillary nerve is at high risk during the Latarjet procedure, particularly during the exposure of the inferior glenoid and capsular release. It innervates the deltoid (shoulder abduction) and provides sensation to the lateral arm via the superior lateral cutaneous nerve of the arm. The musculocutaneous nerve is also at risk during coracoid preparation and transfer, but injury would present with biceps weakness and lateral forearm sensory deficits.

Question 1188

Topic: Surgical Anatomy & Approaches

The direct anterior approach (DAA) to the hip is increasingly popular due to its internervous plane. This surgical approach exploits the interval between muscles supplied by which of the following nerve pairs?

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

Correct Answer & Explanation

. Superior gluteal nerve and Femoral nerve

Explanation

The direct anterior approach to the hip uses the internervous plane between the tensor fasciae latae (supplied by the superior gluteal nerve) and the sartorius (supplied by the femoral nerve). Deep to this, the plane is between the rectus femoris (femoral nerve) and gluteus medius (superior gluteal nerve).

Question 1189

Topic: Surgical Anatomy & Approaches

A surgeon is performing a primary total hip arthroplasty using the direct anterior approach. The superficial internervous plane is established between the sartorius and the tensor fasciae latae. During this specific stage of the superficial dissection, which of the following neurologic structures is at the highest risk of iatrogenic injury?

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

Correct Answer & Explanation

. Lateral femoral cutaneous nerve

Explanation

The direct anterior (Smith-Petersen) approach for total hip arthroplasty utilizes the internervous plane between the sartorius (femoral nerve) and the tensor fasciae latae (superior gluteal nerve). The lateral femoral cutaneous nerve (LFCN) typically crosses anterior to the sartorius and exits the fascia lata near the anterior superior iliac spine, placing it at significant risk during the initial superficial incision and retraction. Injury can lead to meralgia paresthetica.

Question 1190

Topic: Surgical Anatomy & Approaches

During a direct anterior approach for a total hip arthroplasty, the surgeon dissects through the superficial internervous plane between the tensor fasciae latae and the sartorius. In the distal extent of this field, a leash of vessels is encountered crossing the surgical field transversely, requiring ligation. These vessels are branches of which of the following arteries?

. Medial femoral circumflex artery
. Lateral femoral circumflex artery
. Profunda femoris artery
. Superficial femoral artery
. Inferior gluteal artery

Correct Answer & Explanation

. Lateral femoral circumflex artery

Explanation

The direct anterior (Smith-Petersen) approach uses the internervous plane between the sartorius (femoral nerve) and the tensor fasciae latae (superior gluteal nerve). Ascending branches of the lateral femoral circumflex artery consistently cross this surgical interval transversely in its mid-to-distal portion. These vessels must be identified and ligated or cauterized to prevent postoperative hematoma.

Question 1191

Topic: Surgical Anatomy & Approaches

During a direct anterior approach for total hip arthroplasty, the surgeon develops the superficial internervous plane. Which of the following neurological structures is at greatest risk of injury during this specific stage of the dissection?

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

Correct Answer & Explanation

. Lateral femoral cutaneous nerve

Explanation

The direct anterior approach (Smith-Petersen) utilizes the internervous plane between the tensor fasciae latae (superior gluteal nerve) and the sartorius (femoral nerve). The lateral femoral cutaneous nerve (LFCN) crosses this interval superficially and is at high risk of stretch or transection during the approach, which can lead to meralgia paresthetica.

Question 1192

Topic: Surgical Anatomy & Approaches

A surgeon is performing a primary total hip arthroplasty using the direct anterior approach, utilizing the internervous plane between the tensor fasciae latae and the sartorius. During the superficial dissection, a sensory nerve crossing the operative field is inadvertently transected. Damage to this specific nerve will most likely result in sensory loss to which of the following dermatomal distributions?

. Medial aspect of the thigh
. Anterolateral aspect of the thigh
. Posterior aspect of the thigh
. Dorsum of the foot
. Medial aspect of the calf

Correct Answer & Explanation

. Anterolateral aspect of the thigh

Explanation

The direct anterior (Smith-Petersen) approach utilizes the internervous plane between the tensor fasciae latae (superior gluteal nerve) and the sartorius (femoral nerve). The lateral femoral cutaneous nerve (LFCN) is at significant risk during the superficial dissection of this approach, as it frequently branches across the operative field. Injury to the LFCN results in numbness, paresthesia, or dysesthesia over the anterolateral aspect of the thigh.

Question 1193

Topic: Surgical Anatomy & Approaches

A surgeon is performing a primary THA using the direct anterior approach (Smith-Petersen) on a standard operating table. The internervous plane is developed between the tensor fasciae latae and sartorius. To safely expose the anterior joint capsule without causing a postoperative hematoma, which of the following vascular structures typically must be identified and ligated?

. Ascending branches of the lateral circumflex femoral artery
. Descending branches of the lateral circumflex femoral artery
. Medial circumflex femoral artery
. Superior gluteal artery
. Inferior gluteal artery

Correct Answer & Explanation

. Ascending branches of the lateral circumflex femoral artery

Explanation

During the direct anterior approach to the hip, the internervous plane between the sartorius (femoral nerve) and tensor fasciae latae (superior gluteal nerve) is utilized. Deeply, the plane is between the rectus femoris and gluteus medius. The ascending branches of the lateral circumflex femoral artery cross this interval horizontally and must be carefully cauterized or ligated to prevent substantial bleeding and hematoma formation.

Question 1194

Topic: Surgical Anatomy & Approaches

A patient sustains a closed midshaft humerus fracture and presents with a dense radial nerve palsy. Electromyography (EMG) performed at 4 weeks shows fibrillation potentials in the brachioradialis. High-resolution MRI reveals intact endoneurial and epineurial connective tissue architecture. According to the Seddon classification, this injury is best categorized as:

. Neuropraxia
. Axonotmesis
. Neurotmesis
. Sunderland Type IV injury
. Sunderland Type V injury

Correct Answer & Explanation

. Axonotmesis

Explanation

Axonotmesis (Seddon classification) involves disruption of the axon and myelin sheath, leading to Wallerian degeneration distal to the injury (hence fibrillation potentials on EMG after 3-4 weeks). However, the supporting connective tissue structures (endoneurium, perineurium, epineurium) remain intact, allowing for potential spontaneous recovery as the axon regenerates along the intact tubes. Neuropraxia is a temporary conduction block without axonal disruption (no fibrillations). Neurotmesis is complete nerve transection.

Question 1195

Topic: Surgical Anatomy & Approaches
Following a severe crush injury to the sciatic nerve, the distal nerve segment undergoes Wallerian degeneration. Which of the following cell types is primarily responsible for the phagocytosis of myelin debris and the subsequent formation of the bands of Büngner to guide regenerating axonal sprouts in the peripheral nervous system?
. Oligodendrocytes
. Astrocytes
. Microglia
. Schwann cells
. Fibroblasts

Correct Answer & Explanation

. Schwann cells

Explanation

In the peripheral nervous system, Schwann cells are the primary glia responsible for coordinating Wallerian degeneration and regeneration. Alongside infiltrating macrophages, Schwann cells phagocytose myelin debris, proliferate, and align to form longitudinal tubes known as the bands of Büngner. They also secrete essential neurotrophic factors to guide regenerating axons. Oligodendrocytes and microglia perform similar functions in the CNS, but oligodendrocytes typically inhibit axonal regeneration.

Question 1196

Topic: Surgical Anatomy & Approaches

A patient sustains a closed midshaft humerus fracture and presents immediately with a secondary complete radial nerve palsy. Electromyography (EMG) is performed at 4 weeks post-injury and reveals abundant fibrillation potentials and positive sharp waves in the brachioradialis. What is the clinical significance of this EMG finding?

. It represents intact motor end plates indicative of a pure neuropraxia.
. It indicates active muscle denervation resulting from Wallerian degeneration.
. It demonstrates early physiological reinnervation with nascent motor units.
. It implies a primary myopathic process mimicking a peripheral nerve injury.
. It signifies axonotmesis with a guarantee of full spontaneous recovery.

Correct Answer & Explanation

. It indicates active muscle denervation resulting from Wallerian degeneration.

Explanation

Fibrillation potentials and positive sharp waves on an EMG are classic indicators of active muscle denervation. They arise spontaneously from individual denervated muscle fibers. These findings typically appear 3 to 4 weeks after a nerve injury severe enough to cause axonal loss and distal Wallerian degeneration (axonotmesis or neurotmesis). In contrast, neuropraxia (conduction block) involves an intact axon and does not produce fibrillation potentials.

Question 1197

Topic: Surgical Anatomy & Approaches

A 35-year-old patient sustains a closed midshaft humerus fracture and presents with an immediate, complete radial nerve palsy. Electromyography (EMG) is performed at 3 weeks and reveals abundant fibrillation potentials in the brachioradialis and extensor carpi radialis longus. Based on Sunderland's classification, what is the minimum grade of nerve injury sustained?

. First-degree (Neurapraxia)
. Second-degree (Axonotmesis)
. Third-degree
. Fourth-degree
. Fifth-degree (Neurotmesis)

Correct Answer & Explanation

. Second-degree (Axonotmesis)

Explanation

Fibrillation potentials on EMG indicate active muscle denervation secondary to Wallerian degeneration, which takes about 2 to 3 weeks to become electrically evident. First-degree injuries (neurapraxia) represent a focal conduction block without axonal disruption; therefore, Wallerian degeneration does not occur and fibrillations are absent. The presence of fibrillations implies axonal death distal to the injury, making the injury at least a second-degree (axonotmesis), where the axon is disrupted but the endoneurium remains intact.

Question 1198

Topic: Surgical Anatomy & Approaches
A 28-year-old male sustains a midshaft humerus fracture resulting in an acute radial nerve palsy. At 4 weeks, EMG confirms denervation. During the ongoing process of Wallerian degeneration and subsequent peripheral nerve regeneration, which cell type undergoes dedifferentiation, forms the bands of Büngner, and upregulates the production of neurotrophic factors (e.g., NGF) to guide the regenerating axon?
. Fibroblasts
. Macrophages
. Schwann cells
. Astrocytes
. Perineurial cells

Correct Answer & Explanation

. Schwann cells

Explanation

Following a peripheral nerve injury, Schwann cells in the distal nerve stump undergo a massive phenotypic modulation. They dedifferentiate, assist in initial myelin clearance, proliferate, and align to form longitudinal conduits known as the bands of Büngner. Crucially, they upregulate the synthesis of neurotrophic factors (such as Nerve Growth Factor, NGF) and cell adhesion molecules that physically and chemically guide the regenerating axonal sprouts.

Question 1199

Topic: Surgical Anatomy & Approaches
A 34-year-old man sustains a mid-shaft humerus fracture resulting in a radial nerve palsy. Electromyography (EMG) performed 3 weeks later shows fibrillation potentials in the brachioradialis. Which of the following processes predominantly characterizes the Wallerian degeneration occurring distal to the injury site?
. Proliferation of Schwann cells and upregulation of neurotrophic factors
. Immediate death of the anterior horn cell in the spinal cord
. Remyelination of the intact axon by oligodendrocytes
. Phagocytosis of the myelin sheath solely by circulating neutrophils
. Retrograde axonal transport of inflammatory cytokines leading to cortical reorganization

Correct Answer & Explanation

. Proliferation of Schwann cells and upregulation of neurotrophic factors

Explanation

Wallerian degeneration is the process of anterograde breakdown of the axon and myelin sheath distal to a nerve injury (axonotmesis or neurotmesis). Following the injury, local macrophages and Schwann cells phagocytose the axonal and myelin debris (neutrophils are not the primary phagocytes here). Critically, Schwann cells then proliferate within the remaining endoneurial tubes and upregulate neurotrophic factors (such as NGF and BDNF) and surface adhesion molecules. These cells align to form the Bands of Büngner, which provide a supportive microenvironment and physically guide the regenerating axonal sprouts from the proximal stump toward the target organ.

Question 1200

Topic: Surgical Anatomy & Approaches

A 28-year-old patient sustains a closed midshaft humerus fracture resulting in an immediate radial nerve palsy. EMGs performed at 4 weeks show fibrillation potentials but no motor unit action potentials. Which of the following describes the correct order of the connective tissue layers in a peripheral nerve, from innermost (surrounding individual axons) to outermost (surrounding the entire nerve)?

. Epineurium, Perineurium, Endoneurium
. Endoneurium, Epineurium, Perineurium
. Endoneurium, Perineurium, Epineurium
. Perineurium, Endoneurium, Epineurium
. Epineurium, Endoneurium, Perineurium

Correct Answer & Explanation

. Endoneurium, Perineurium, Epineurium

Explanation

The connective tissue layers of a peripheral nerve, from deep to superficial, are: the Endoneurium (surrounds individual axons and their Schwann cells), the Perineurium (surrounds groups of axons to form fascicles, providing primary mechanical strength and maintaining the blood-nerve barrier), and the Epineurium (the outermost layer surrounding the entire nerve and the interfascicular spaces).

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