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Question 1701

Topic: Surgical Anatomy & Approaches

A 6-year-old child sustains an extension-type supracondylar humerus fracture with posterolateral displacement. Which of the following neurologic structures is at greatest risk of injury?

. Ulnar nerve
. Anterior interosseous nerve (AIN)
. Radial nerve
. Musculocutaneous nerve
. Axillary nerve

Correct Answer & Explanation

. Ulnar nerve


Explanation

In an extension-type supracondylar humerus fracture with posterolateral displacement of the distal fragment, the proximal fragment is directed anteromedially. This anteromedial spike places the median nerve (specifically the anterior interosseous nerve branch) and the brachial artery at the greatest risk of injury. Conversely, posteromedial displacement of the distal fragment drives the proximal fragment anterolaterally, risking the radial nerve.

Question 1702

Topic: Surgical Anatomy & Approaches
A 35-year-old male sustained a closed mid-shaft humerus fracture resulting in an immediate complete radial nerve palsy. Four months post-injury, there is no clinical or electromyographic (EMG) evidence of recovery. If surgical exploration confirms a Sunderland Grade III nerve injury, what is the precise microanatomic state of the affected nerve?
. Myelin sheath disruption with an intact axon
. Axonal disruption with completely intact endoneurial tubes
. Axonal and endoneurial disruption with an intact perineurium
. Disruption of the axon, endoneurium, and perineurium with an intact epineurium
. Complete physical transection of all macroscopic nerve components

Correct Answer & Explanation

. Axonal and endoneurial disruption with an intact perineurium


Explanation

In the Sunderland classification: Grade I (Neuropraxia) = local myelin damage; Grade II (Axonotmesis) = axonal disruption with intact endoneurium (excellent recovery potential); Grade III = axonal and endoneurial disruption with intact perineurium (unpredictable recovery due to intraneural scarring); Grade IV = disruption of axon, endoneurium, and perineurium, leaving only the epineurium intact; Grade V = complete nerve transection (Neurotmesis).

Question 1703

Topic: Surgical Anatomy & Approaches
A 62-year-old female undergoes a ligament reconstruction and tendon interposition (LRTI) using the flexor carpi radialis (FCR) tendon for advanced Eaton-Littler Stage III thumb CMC arthritis. During the surgical approach to the CMC joint, which of the following nerves is at greatest risk of iatrogenic injury?
. Superficial radial nerve
. Palmar cutaneous branch of the median nerve
. Lateral antebrachial cutaneous nerve
. Dorsal sensory branch of the ulnar nerve
. Deep motor branch of the ulnar nerve

Correct Answer & Explanation

. Superficial radial nerve


Explanation

The surgical approach to the thumb carpometacarpal (CMC) joint often involves a dorsal or dorsoradial incision. The terminal sensory branches of the superficial radial nerve run directly over this area and are at highest risk of injury, which can lead to painful neuromas. Careful blunt dissection and retraction are required to protect them.

Question 1704

Topic: Surgical Anatomy & Approaches

A 62-year-old woman undergoes a ligament reconstruction and tendon interposition (LRTI) using the flexor carpi radialis (FCR) tendon for advanced thumb carpometacarpal (CMC) arthritis. Postoperatively, she complains of new-onset numbness and tingling over the dorsal-radial aspect of the hand. Injury to which of the following nerves most likely occurred during the surgical approach?

. Palmar cutaneous branch of the median nerve
. Superficial branch of the radial nerve
. Posterior interosseous nerve
. Dorsal sensory branch of the ulnar nerve
. Anterior interosseous nerve

Correct Answer & Explanation

. Palmar cutaneous branch of the median nerve


Explanation

The superficial branch of the radial nerve (SBRN) is highly vulnerable to injury or traction during the dorsal-radial surgical approaches to the thumb CMC joint, such as those used for LRTI. Injury results in numbness or painful neuromas over the dorsal-radial hand.

Question 1705

Topic: Surgical Anatomy & Approaches

You are reviewing an axial cross-section of the shoulder during a pre-operative imaging review for a posterior approach.

What structure forms the superior boundary of the quadrangular space, and what is its primary innervation?

. Teres major; Lower subscapular nerve
. Teres minor; Axillary nerve
. Infraspinatus; Suprascapular nerve
. Subscapularis; Upper and lower subscapular nerves
. Long head of triceps; Radial nerve

Correct Answer & Explanation

. Teres major; Lower subscapular nerve


Explanation

The quadrangular space is a critical anatomic space in the posterior shoulder. Its boundaries are: superiorly the teres minor (innervated by the axillary nerve), inferiorly the teres major, medially the long head of the triceps, and laterally the surgical neck of the humerus. It contains the axillary nerve and the posterior circumflex humeral artery.

Question 1706

Topic: Surgical Anatomy & Approaches

A surgeon plans a volar (Henry) approach to the proximal radius for open reduction internal fixation of a diaphyseal fracture.

What are the innervations of the muscles defining the proximal internervous plane in this approach?

. Radial nerve and Median nerve
. Ulnar nerve and Median nerve
. Radial nerve and Ulnar nerve
. Posterior interosseous nerve and Anterior interosseous nerve
. Musculocutaneous nerve and Radial nerve

Correct Answer & Explanation

. Radial nerve and Median nerve


Explanation

The proximal internervous plane of the volar (Henry) approach to the forearm utilizes the interval between the brachioradialis (innervated by the radial nerve) and the pronator teres (innervated by the median nerve). Distally, the plane is between the brachioradialis and the flexor carpi radialis (median nerve).

Question 1707

Topic: Surgical Anatomy & Approaches

During a posterior (Kocher-Langenbeck) approach to the hip, protecting the primary blood supply to the adult femoral head is paramount. In this region, where is the deep branch of the medial femoral circumflex artery (MFCA) consistently found?

. Superior to the piriformis tendon
. Between the inferior gemellus and obturator internus
. Between the quadratus femoris and obturator externus
. Anterior to the iliopsoas tendon
. Passing through the greater sciatic foramen deep to the sciatic nerve

Correct Answer & Explanation

. Superior to the piriformis tendon


Explanation

The medial femoral circumflex artery (MFCA) is the primary blood supply to the adult femoral head. The deep branch of the MFCA runs anterior to the quadratus femoris and posterior to the obturator externus. To protect it during a posterior approach, the surgeon must avoid releasing the obturator externus and should not divide the quadratus femoris too medially.

Question 1708

Topic: Surgical Anatomy & Approaches

During a midfoot surgical approach, the surgeon identifies the 'Master Knot of Henry' on the plantar aspect of the foot. At this location, what is the specific anatomical relationship between the traversing long flexor tendons?

. The flexor hallucis longus (FHL) crosses dorsal (deep) to the flexor digitorum longus (FDL)
. The FHL crosses plantar (superficial) to the FDL
. The FHL and FDL run parallel without crossing
. The tibialis posterior crosses deep to the FHL
. The FDL crosses deep to the tibialis anterior

Correct Answer & Explanation

. The flexor hallucis longus (FHL) crosses dorsal (deep) to the flexor digitorum longus (FDL)


Explanation

The Master Knot of Henry is an important anatomic landmark located on the plantar aspect of the midfoot at the level of the navicular. Here, the flexor hallucis longus (FHL) tendon crosses dorsal (deep) to the flexor digitorum longus (FDL) tendon. It is a critical site of potential tendon tethering or tenosynovitis.

Question 1709

Topic: Surgical Anatomy & Approaches

A saphenous nerve block is planned within the adductor (Hunter's) canal for post-operative analgesia following knee surgery. Besides the superficial femoral artery and vein, what other structures travel through the adductor canal?

. Femoral nerve and nerve to vastus intermedius
. Saphenous nerve and nerve to vastus medialis
. Obturator nerve and medial femoral circumflex artery
. Tibial nerve and popliteal vein
. Sural nerve and descending genicular artery

Correct Answer & Explanation

. Femoral nerve and nerve to vastus intermedius


Explanation

The adductor canal (Hunter's canal) begins at the apex of the femoral triangle and ends at the adductor hiatus. Its contents include the superficial femoral artery, superficial femoral vein, the saphenous nerve, and the nerve to the vastus medialis. The main femoral nerve has already arborized proximally in the femoral triangle.

Question 1710

Topic: Surgical Anatomy & Approaches

During a standard ilioinguinal approach for an anterior column acetabular fracture, the surgeon is working in the middle window. Which of the following neurovascular structures is primarily found in this window?

. Femoral nerve and iliopsoas
. External iliac vessels
. Spermatic cord and rectus abdominis
. Obturator nerve and artery
. Superior gluteal artery and nerve

Correct Answer & Explanation

. Femoral nerve and iliopsoas


Explanation

The ilioinguinal approach has three windows. The middle window, located between the iliopectineal fascia and the conjoint tendon, contains the external iliac artery and vein.

Question 1711

Topic: Surgical Anatomy & Approaches

A 35-year-old male sustains a midshaft humerus fracture and develops a secondary radial nerve palsy after closed reduction. If the surgeon decides to explore the nerve via a posterior approach, between which two muscle bellies does the radial nerve most reliably emerge from the spiral groove?

. Long head and lateral head of the triceps
. Lateral head and medial head of the triceps
. Brachialis and brachioradialis
. Teres major and long head of the triceps
. Brachialis and lateral head of the triceps

Correct Answer & Explanation

. Long head and lateral head of the triceps


Explanation

In the posterior approach to the humerus, the radial nerve is found in the spiral groove between the lateral and medial heads of the triceps. The long head is medial to the nerve.

Question 1712

Topic: Surgical Anatomy & Approaches

While performing an extended volar approach to the radiocarpal joint (Henry approach), the surgeon retracts the flexor carpi radialis (FCR) tendon. To minimize the risk of injury to the palmar cutaneous branch of the median nerve (PCBMN), in which direction should the FCR tendon be retracted and where does the PCBMN typically lie?

. FCR retracted radially; PCBMN lies radial to the FCR
. FCR retracted ulnarly; PCBMN lies ulnar to the FCR
. FCR retracted ulnarly; PCBMN lies radial to the FCR
. FCR retracted radially; PCBMN lies ulnar to the FCR
. FCR retracted distally; PCBMN lies deep to the FCR

Correct Answer & Explanation

. FCR retracted radially; PCBMN lies radial to the FCR


Explanation

The PCBMN typically arises 5 cm proximal to the wrist crease and travels on the ulnar side of the FCR. Retracting the FCR ulnarly protects the nerve during the volar approach.

Question 1713

Topic: Surgical Anatomy & Approaches

A surgeon is utilizing the Smith-Petersen approach to the hip. This approach exploits an internervous plane between which of the following muscles superficially?

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

Correct Answer & Explanation

. Tensor fasciae latae (Superior gluteal n.) and Gluteus medius (Superior gluteal n.)


Explanation

The superficial internervous plane in the anterior (Smith-Petersen) approach to the hip lies between the sartorius (innervated by the femoral nerve) and the tensor fasciae latae (innervated by the superior gluteal nerve).

Question 1714

Topic: Surgical Anatomy & Approaches

While executing a deltopectoral approach for a total shoulder arthroplasty, the coracobrachialis is retracted.

To avoid iatrogenic injury, the surgeon must remember that the musculocutaneous nerve typically enters the coracobrachialis at what average distance distal to the coracoid process?

. 1 to 3 cm
. 5 to 8 cm
. 9 to 11 cm
. 12 to 14 cm
. Greater than 15 cm

Correct Answer & Explanation

. 1 to 3 cm


Explanation

The musculocutaneous nerve typically penetrates the coracobrachialis muscle at an average distance of 5 to 8 cm distal to the tip of the coracoid process. Aggressive distal retraction of the conjoined tendon can cause neuropraxia.

Question 1715

Topic: Surgical Anatomy & Approaches

When planning an anterolateral approach to the distal humerus, an MRI shows the radial nerve piercing the lateral intermuscular septum. At what average distance proximal to the lateral epicondyle does this anatomically occur?

. 3 cm
. 6 cm
. 10 cm
. 14 cm
. 18 cm

Correct Answer & Explanation

. 3 cm


Explanation

The radial nerve pierces the lateral intermuscular septum to pass from the posterior to the anterior compartment of the arm at approximately 10 cm proximal to the lateral epicondyle.

Question 1716

Topic: Surgical Anatomy & Approaches

In a coronal MRI of the brachial plexus evaluating a traction injury, the posterior cord is visualized. Which of the following is a direct terminal branch of the posterior cord?

. Musculocutaneous nerve
. Median nerve
. Ulnar nerve
. Axillary nerve
. Suprascapular nerve

Correct Answer & Explanation

. Musculocutaneous nerve


Explanation

The posterior cord of the brachial plexus gives rise to the upper subscapular, thoracodorsal, and lower subscapular nerves, before bifurcating into its terminal branches: the axillary and radial nerves.

Question 1717

Topic: Surgical Anatomy & Approaches

During a modified Stoppa approach for an acetabular fracture, an aberrant vascular anastomosis termed the 'corona mortis' is encountered over the superior pubic ramus. This structure connects which two vascular systems?

. Internal iliac (obturator) and external iliac (inferior epigastric)
. Superior gluteal and inferior gluteal systems
. Internal pudendal and obturator systems
. External pudendal and femoral systems
. Deep circumflex iliac and inferior epigastric systems

Correct Answer & Explanation

. Internal iliac (obturator) and external iliac (inferior epigastric)


Explanation

The corona mortis ('crown of death') is an anastomosis between the obturator vessels (internal iliac system) and the inferior epigastric vessels (external iliac system). It is vulnerable to severe bleeding during intrapelvic approaches if not properly identified and ligated.

Question 1718

Topic: Surgical Anatomy & Approaches

The Kocher-Langenbeck approach to the acetabulum does not utilize a true internervous plane. What is the primary innervation of the gluteus maximus muscle, which is split during the superficial dissection of this approach?

. Superior gluteal nerve
. Inferior gluteal nerve
. Sciatic nerve
. Nerve to quadratus femoris
. Pudendal nerve

Correct Answer & Explanation

. Superior gluteal nerve


Explanation

The gluteus maximus is innervated by the inferior gluteal nerve. The Kocher-Langenbeck approach utilizes a muscle-splitting incision through the gluteus maximus rather than a true internervous plane.

Question 1719

Topic: Surgical Anatomy & Approaches



When performing a posterior approach to the humerus, the radial nerve must be identified and protected. Approximately how far proximal to the lateral epicondyle does the radial nerve pierce the lateral intermuscular septum?

. 5 cm
. 10 cm
. 15 cm
. 20 cm
. 25 cm

Correct Answer & Explanation

. 5 cm


Explanation

The radial nerve passes from the posterior compartment to the anterior compartment by piercing the lateral intermuscular septum approximately 10 cm proximal to the lateral epicondyle. This is a critical landmark during the posterior approach.

Question 1720

Topic: Surgical Anatomy & Approaches



In the anterior approach to the hip (Smith-Petersen), the superficial internervous plane lies between two muscles. What are the respective innervations of these two muscles?

. Femoral nerve and superior gluteal nerve
. Femoral nerve and obturator 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 superficial plane of the Smith-Petersen approach is between the sartorius (femoral nerve) and the tensor fasciae latae (superior gluteal nerve). This provides a safe, true internervous plane.