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Surgical Anatomy & Approaches MCQs

Practice Set 96 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 1901

Topic: Surgical Anatomy & Approaches

When performing a deltoid-splitting approach for a proximal humerus fracture, the axillary nerve is at risk of iatrogenic injury. On average, at what distance distal to the lateral edge of the acromion does the axillary nerve cross the humerus?

. 3 cm
. 7 cm
. 11 cm
. 14 cm
. 18 cm

Correct Answer & Explanation

. 7 cm

Explanation

The axillary nerve runs transversely from posterior to anterior, crossing the humerus approximately 5 to 7 cm distal to the lateral border of the acromion. A deltoid split extending further distal than 5 cm safely places this nerve at significant risk. Proximal extension of the split should be carefully measured or protected with a stay suture.

Question 1902

Topic: Surgical Anatomy & Approaches

During a posterior approach to the humeral shaft, the radial nerve is identified in the spiral groove. At what approximate distance proximal to the lateral epicondyle does the radial nerve cross the posterior aspect of the humerus?

. 5 cm
. 10 cm
. 14 cm
. 18 cm
. 22 cm

Correct Answer & Explanation

. 14 cm

Explanation

The radial nerve runs in the spiral groove of the posterior humerus. Classic anatomic studies consistently locate the nerve approximately 14 cm proximal to the lateral epicondyle and 20 cm proximal to the medial epicondyle. Knowing these landmarks helps safely localize the nerve during posterior humerus exposures.

Question 1903

Topic: Surgical Anatomy & Approaches

During an anterior (Henry) approach to the proximal radius, the supinator muscle must be elevated. To protect the posterior interosseous nerve (PIN), the supinator should be detached from its insertion and reflected laterally. The PIN enters the supinator beneath a fibrous arch known as the Arcade of Frohse. Which structure forms this arcade?

. Thickened fascial edge of the extensor carpi radialis brevis
. Thickened superficial edge of the supinator muscle
. Tendinous insertion of the brachialis
. Fascia of the pronator teres
. Lacertus fibrosus

Correct Answer & Explanation

. Thickened superficial edge of the supinator muscle

Explanation

The Arcade of Frohse is a fibrous arch formed by the thickened superficial tendinous edge of the supinator muscle. It is the most common site of compression for the posterior interosseous nerve (PIN). Supination of the forearm during the Henry approach moves the PIN radially, further protecting it during dissection.

Question 1904

Topic: Surgical Anatomy & Approaches

A 30-year-old male sustains an acetabular fracture (posterior wall and column) with associated posterior hip dislocation. He undergoes successful closed reduction. Post-reduction, he reports numbness and tingling in his foot and weakness in ankle dorsiflexion. Which nerve is most likely injured?

. Femoral nerve.
. Obturator nerve.
. Superior gluteal nerve.
. Sciatic nerve.
. Peroneal nerve.

Correct Answer & Explanation

. Sciatic nerve.

Explanation

Posterior hip dislocations and associated acetabular fractures (especially posterior wall) are well-known to cause sciatic nerve injury (D). The sciatic nerve exits the pelvis through the greater sciatic notch, lying directly posterior to the hip joint. It can be stretched, compressed, or contused during dislocation or by fracture fragments. The symptoms of numbness/tingling in the foot and weakness in ankle dorsiflexion (foot drop) are classic signs of peroneal division injury of the sciatic nerve. The femoral nerve (A) innervates the anterior thigh and would cause quadriceps weakness. The obturator nerve (B) innervates the medial thigh. The superior gluteal nerve (C) innervates gluteus medius/minimus, affecting hip abduction. The peroneal nerve (E) is a branch of the sciatic, but the sciatic nerve itself is the structure injured proximally.

Question 1905

Topic: Surgical Anatomy & Approaches

For exposure of the posterior column and posterior wall of the acetabulum, which surgical approach is most commonly utilized?

. Kocher-Langenbeck approach.
. Ilioinguinal approach.
. Stoppa approach.
. Direct anterior (Smith-Petersen) approach.
. Hohmann approach.

Correct Answer & Explanation

. Kocher-Langenbeck approach.

Explanation

The Kocher-Langenbeck approach is the workhorse approach for posterior column and posterior wall acetabular fractures. It involves an incision along the posterior border of the greater trochanter and gluteal maximus, allowing access to the posterior aspect of the acetabulum. The ilioinguinal and Stoppa (modified obturator) approaches are anterior approaches used for anterior column, anterior wall, or transverse fractures. The direct anterior (Smith-Petersen) approach is used for anterior hip arthroplasty or certain anterior acetabular pathologies, but not extensive acetabular trauma. Hohmann is not a standard major acetabular approach.

Question 1906

Topic: Surgical Anatomy & Approaches

A 60-year-old male undergoes closed reduction of a posterior hip dislocation 8 hours after injury. Post-reduction radiographs show a concentric reduction. He complains of persistent pain and numbness in the lateral aspect of his calf and weakness in foot dorsiflexion. Which nerve is most likely injured?

. Femoral nerve
. Obturator nerve
. Superior gluteal nerve
. Inferior gluteal nerve
. Common peroneal nerve

Correct Answer & Explanation

. Common peroneal nerve

Explanation

The sciatic nerve is commonly injured in posterior hip dislocations. The sciatic nerve divides into the tibial and common peroneal nerves. The described symptoms (numbness in the lateral calf, weakness in foot dorsiflexion - ankle dorsiflexion and eversion) are classic signs of a common peroneal nerve palsy. The common peroneal nerve is more susceptible to injury than the tibial nerve due to its superficial course and tethering around the fibular neck. The femoral nerve would cause quadriceps weakness and anterior thigh sensory loss. The obturator nerve affects adduction. The gluteal nerves affect hip abduction or extension, respectively.

Question 1907

Topic: Surgical Anatomy & Approaches

A 28-year-old male sustains an anterior hip dislocation after a motor vehicle accident. On physical examination, his hip is externally rotated, abducted, and slightly flexed. What associated nerve injury should be specifically assessed?

. Sciatic nerve.
. Femoral nerve.
. Common peroneal nerve.
. Superior gluteal nerve.
. Lateral femoral cutaneous nerve.

Correct Answer & Explanation

. Femoral nerve.

Explanation

Anterior hip dislocations are less common than posterior dislocations. The typical mechanism is forced abduction and external rotation. In this position, the femoral nerve is at risk of injury due to its proximity to the anterior capsule and femoral head. Injury to the femoral nerve would manifest as weakness in knee extension (quadriceps) and sensory loss over the anterior thigh and medial leg (via the saphenous nerve branch). Sciatic and common peroneal nerve injuries are characteristic of posterior hip dislocations. Superior gluteal nerve injuries are associated with pelvic fractures or iatrogenic damage. Lateral femoral cutaneous nerve injury causes meralgia paresthetica (lateral thigh numbness) and is less directly associated with hip dislocation.

Question 1908

Topic: Surgical Anatomy & Approaches

When performing limb salvage for a proximal humeral osteosarcoma, which nerve is at greatest risk of injury during the surgical approach and dissection around the axilla?

. Radial nerve
. Ulnar nerve
. Median nerve
. Axillary nerve
. Musculocutaneous nerve

Correct Answer & Explanation

. Axillary nerve

Explanation

During surgery for proximal humeral tumors, especially involving the deltoid and surgical neck, the axillary nerve is at the greatest risk of injury. It courses around the surgical neck of the humerus, innervating the deltoid and teres minor. Damage to this nerve results in deltoid paralysis and significant shoulder dysfunction. The radial, ulnar, and median nerves are typically more distal or protected within the neurovascular bundle, though they are always at risk in extensive resections.

Question 1909

Topic: Surgical Anatomy & Approaches

A patient undergoes curettage for a presumed enchondroma. Intraoperatively, the lesion appears more aggressive than expected. What is the most crucial step regarding the excised tissue?

. Discard the tissue if it looks benign
. Send for immediate frozen section analysis by a musculoskeletal pathologist
. Send only a small fragment for routine pathology
. Preserve in saline for later analysis
. Send for genetic testing only

Correct Answer & Explanation

. Send for immediate frozen section analysis by a musculoskeletal pathologist

Explanation

If the intraoperative appearance of a lesion suggests malignancy despite a preoperative diagnosis of enchondroma, an immediate frozen section analysis by an experienced musculoskeletal pathologist is crucial. This rapid assessment can guide the surgeon in extending resection margins or changing the surgical approach during the same procedure, optimizing patient outcomes. Discarding tissue or sending only small fragments would be inappropriate.

Question 1910

Topic: Surgical Anatomy & Approaches

Regarding the surgical approach for a posterior wall acetabular fracture, what is a critical consideration to prevent iatrogenic sciatic nerve injury?

. Limiting hip flexion during exposure
. Avoiding release of the piriformis muscle
. Minimizing traction on the inferior gluteal artery
. Placing retractors deep to the short external rotators but superficial to the nerve
. Utilizing a modified Stoppa approach

Correct Answer & Explanation

. Placing retractors deep to the short external rotators but superficial to the nerve

Explanation

When using the Kocher-Langenbeck approach for posterior wall acetabular fractures, the sciatic nerve lies deep to the short external rotators (gemelli, obturator internus, quadratus femoris). Careful placement of retractors superficial to the sciatic nerve but deep to these muscles is crucial to avoid direct nerve compression or stretching, which can lead to iatrogenic injury. Limiting hip flexion helps prevent excessive tension on the nerve. The Stoppa approach is an anterior approach and not relevant to a posterior wall fracture. Avoiding piriformis release is not a primary factor in sciatic nerve protection specific to retractors.

Question 1911

Topic: Surgical Anatomy & Approaches

Which of the following describes a key risk of the anterior approach (ilioinguinal) for acetabular fracture fixation?

. Sciatic nerve injury
. Superior gluteal artery injury
. Lateral femoral cutaneous nerve injury
. Posterior femoral cutaneous nerve injury
. Common peroneal nerve injury

Correct Answer & Explanation

. Lateral femoral cutaneous nerve injury

Explanation

The lateral femoral cutaneous nerve (LFCN) is particularly vulnerable during the ilioinguinal approach for acetabular fractures as it crosses the iliac crest and passes through or under the inguinal ligament. Injury can lead to meralgia paresthetica (pain, numbness, or burning sensation on the lateral thigh). Sciatic nerve injury is a risk with posterior approaches. Superior gluteal artery injury is a risk with iliosacral screw placement. Posterior femoral cutaneous and common peroneal nerves are not typically at risk with an anterior ilioinguinal approach.

Question 1912

Topic: Surgical Anatomy & Approaches

Which surgical approach for acetabular fractures offers the best visualization of the anterior column, posterior column, and quadrilateral surface simultaneously?

. Kocher-Langenbeck approach
. Ilioinguinal approach
. Modified Stoppa approach (pararectus or infrapectineal)
. Extended iliofemoral approach
. Anterior approach (Smith-Petersen)

Correct Answer & Explanation

. Modified Stoppa approach (pararectus or infrapectineal)

Explanation

The modified Stoppa approach (pararectus or infrapectineal approach) combined with a limited ilioinguinal approach or alone, offers excellent direct visualization of the anterior column, posterior column (from the inside of the pelvis via the quadrilateral surface), and the quadrilateral surface. This approach has gained popularity for its ability to address both columns through a single incision in many complex fracture patterns. The Kocher-Langenbeck is posterior. Ilioinguinal provides anterior and middle window access. The extended iliofemoral is a massive approach with significant morbidity. The Smith-Petersen is less extensive and generally for hip arthroplasty.

Question 1913

Topic: Surgical Anatomy & Approaches

A patient is undergoing biopsy for a suspected metastatic lesion to the sacrum. Which of the following is a critical anatomical structure to be mindful of during the biopsy of the sacrum?

. Sciatic nerve
. Femoral nerve
. Inferior vena cava
. Sural nerve
. Spinal accessory nerve

Correct Answer & Explanation

. Sciatic nerve

Explanation

The sciatic nerve exits the pelvis through the greater sciatic foramen, immediately anterior to the sacrum, and can be at significant risk during sacral biopsies, especially from a posterior or posterolateral approach. Injury to the sciatic nerve can result in devastating motor and sensory deficits. While the femoral nerve is important, it's more anterior. The inferior vena cava is more anterior and superior in the abdomen. The sural and spinal accessory nerves are not in the vicinity of the sacrum.

Question 1914

Topic: Surgical Anatomy & Approaches

What is the most common nerve injury associated with proximal fibula fractures, particularly those involving the fibular head?

. Sciatic nerve.
. Femoral nerve.
. Superficial peroneal nerve.
. Deep peroneal nerve.
. Common peroneal nerve.

Correct Answer & Explanation

. Common peroneal nerve.

Explanation

The common peroneal nerve courses around the neck of the fibula, making it highly susceptible to injury with fractures of the fibular head or neck. Injury to the common peroneal nerve typically results in a 'foot drop' due to paralysis of the ankle dorsiflexors and evertors, along with sensory loss over the dorsum of the foot and lateral leg. The superficial and deep peroneal nerves are branches of the common peroneal nerve, so an injury to the common peroneal nerve would affect both. Sciatic and femoral nerves are anatomically more proximal.

Question 1915

Topic: Surgical Anatomy & Approaches

Which of the following statements regarding the posterior interosseous nerve (PIN) is TRUE?

. It provides sensory innervation to the dorsal forearm and hand.
. It is a branch of the median nerve.
. It innervates the brachioradialis and extensor carpi radialis longus muscles.
. It is purely a motor nerve after it branches from the radial nerve.
. It commonly causes 'wrist drop' when compressed at the elbow.

Correct Answer & Explanation

. It is purely a motor nerve after it branches from the radial nerve.

Explanation

The posterior interosseous nerve (PIN) is a purely motor nerve, branching from the radial nerve within the cubital fossa. It innervates the extrinsic extensors of the fingers and thumb, as well as the extensor carpi ulnaris and supinator. The superficial radial nerve provides sensory innervation. The radial nerve itself innervates the brachioradialis and ECRL (before it splits). A 'wrist drop' is typically associated with a more proximal radial nerve lesion, as the PIN lesion would preserve wrist extension through ECRL and ECPL (radial-innervated muscles before PIN branch).

Question 1916

Topic: Surgical Anatomy & Approaches

Which nerve is at greatest risk of iatrogenic injury during surgical intervention for lateral epicondylitis?

. Median nerve
. Ulnar nerve
. Musculocutaneous nerve
. Superficial radial nerve
. Posterior interosseous nerve

Correct Answer & Explanation

. Posterior interosseous nerve

Explanation

During surgical intervention for lateral epicondylitis, especially with deeper dissection, the posterior interosseous nerve (PIN), a branch of the radial nerve, is at greatest risk. It winds around the radial neck and passes through the supinator muscle (Arcade of Frohse), near the surgical field for the common extensor origin. The superficial radial nerve is also a risk, but typically more distal and subcutaneous. Median, ulnar, and musculocutaneous nerves are more distant from the lateral epicondyle.

Question 1917

Topic: Surgical Anatomy & Approaches

An examiner asks you to describe post-operative complications following shoulder arthroscopy. Which of the following is a recognized, albeit rare, neurological complication specific to the beach-chair position?

. Axillary nerve injury.
. Musculocutaneous nerve injury.
. Brachial plexus traction injury.
. Suprascapular nerve injury.
. Ulnar nerve compression neuropathy.

Correct Answer & Explanation

. Brachial plexus traction injury.

Explanation

Brachial plexus traction injury, particularly involving the lower trunk (C8-T1), is a recognized, albeit rare, complication associated with the beach-chair position during shoulder arthroscopy. This typically occurs due to excessive traction on the arm, often compounded by factors like neck lateral flexion or rotation. While other nerve injuries can occur, brachial plexus traction is a specific concern related to positioning and traction application. Axillary nerve injury is more common with deltoid dissection, and musculocutaneous or suprascapular nerve injuries are more likely with direct iatrogenic injury or retraction.

Question 1918

Topic: Surgical Anatomy & Approaches

An examiner asks you about the 'quadrilateral space syndrome'. Which nerve and artery are primarily compressed in this syndrome?

. Suprascapular nerve and suprascapular artery.
. Axillary nerve and posterior circumflex humeral artery.
. Musculocutaneous nerve and anterior circumflex humeral artery.
. Radial nerve and profunda brachii artery.
. Ulnar nerve and ulnar artery.

Correct Answer & Explanation

. Axillary nerve and posterior circumflex humeral artery.

Explanation

The quadrilateral space is an anatomical space bounded by the teres minor (superiorly), teres major (inferiorly), long head of triceps (medially), and surgical neck of the humerus (laterally). The axillary nerve and posterior circumflex humeral artery pass through this space. Compression of these structures, often due to fibrous bands or trauma, can lead to quadrilateral space syndrome, characterized by posterior shoulder pain, paresthesia, and deltoid weakness. The other options involve different anatomical structures and locations.

Question 1919

Topic: Surgical Anatomy & Approaches

An examiner asks about a patient with a proximal humerus fracture and suspected axillary nerve injury. What clinical finding would be most indicative of this nerve injury?

. Weakness in wrist extension.
. Loss of sensation over the medial forearm.
. Inability to abduct the arm beyond 90 degrees due to deltoid weakness.
. Weakness in elbow flexion.
. Paresthesia in the thumb, index, and middle fingers.

Correct Answer & Explanation

. Inability to abduct the arm beyond 90 degrees due to deltoid weakness.

Explanation

The axillary nerve innervates the deltoid and teres minor muscles and provides sensory supply to the 'regimental badge' area over the lateral shoulder. Therefore, inability to abduct the arm (due to deltoid weakness) combined with sensory loss over the lateral shoulder would be most indicative of an axillary nerve injury. The other options describe symptoms related to different nerve distributions.

Question 1920

Topic: Surgical Anatomy & Approaches

A 32-year-old male sustains a closed, mid-shaft humerus fracture. On initial presentation, his neurovascular exam is completely normal. A closed reduction is performed and a coaptation splint is applied. Immediately following the reduction, the patient is noted to have a complete wrist drop and inability to extend his fingers. What is the most appropriate next step in management?

. Clinical observation for 3 to 4 months followed by EMG if no recovery is noted
. Immediate surgical exploration of the radial nerve and rigid fracture fixation
. Immediate electromyography (EMG) and nerve conduction studies
. Switching from a coaptation splint to a Sarmiento functional fracture brace
. Administration of high-dose intravenous corticosteroids

Correct Answer & Explanation

. Immediate surgical exploration of the radial nerve and rigid fracture fixation

Explanation

While an initial (primary) radial nerve palsy in a closed humerus fracture is generally treated with observation, a secondary radial nerve palsy that developsimmediately aftera closed reduction attempt strongly suggests that the nerve has become entrapped or lacerated within the fracture site during the manipulation. This is a classic indication for immediate surgical exploration and internal fixation.

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