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Question 1241

Topic: Surgical Anatomy & Approaches

During a Smith-Petersen approach to the hip, the internervous plane is developed to access the anterior joint capsule. This plane is defined by muscles innervated by which of the following pairs of nerves?

. Superior gluteal and femoral nerves
. Femoral and obturator nerves
. Superior gluteal and inferior gluteal nerves
. Sciatic and inferior gluteal nerves
. Femoral and sciatic nerves

Correct Answer & Explanation

. Superior gluteal and femoral nerves


Explanation

The Smith-Petersen (anterior) approach utilizes the internervous plane between the sartorius (femoral nerve) and the tensor fasciae latae (superior gluteal nerve). Deep dissection passes between the rectus femoris (femoral nerve) and gluteus medius (superior gluteal nerve).

Question 1242

Topic: Surgical Anatomy & Approaches

During an ilioinguinal approach for open reduction of an anterior column acetabular fracture, severe hemorrhage is encountered upon dissection just posterior to the superior pubic ramus. This bleeding is most likely originating from an anastomotic connection between which two vascular systems?

. Internal pudendal and external pudendal arteries
. External iliac and internal iliac systems
. Internal pudendal and obturator arteries
. Superior gluteal and inferior gluteal arteries
. Deep circumflex iliac and inferior epigastric arteries

Correct Answer & Explanation

. External iliac and internal iliac systems


Explanation

The corona mortis is a vascular anastomosis between the external iliac system (usually via the inferior epigastric artery) and the internal iliac system (obturator artery). It crosses the superior pubic ramus approximately 5 cm from the pubic symphysis.

Question 1243

Topic: Surgical Anatomy & Approaches

During a lateral deltoid-splitting approach for fixation of a proximal humerus fracture, the axillary nerve is at risk of iatrogenic injury. Approximately how far distal to the lateral edge of the acromion does the axillary nerve typically course on the deep surface of the deltoid?

. 2 cm
. 5 cm
. 9 cm
. 12 cm
. 15 cm

Correct Answer & Explanation

. 5 cm


Explanation

The axillary nerve courses circumferentially from posterior to anterior on the deep surface of the deltoid, typically about 5 to 7 cm distal to the lateral tip of the acromion. Splitting the deltoid distal to this 'safe zone' risks denervating the anterior aspect of the muscle.

Question 1244

Topic: Surgical Anatomy & Approaches

Anatomical variations in the relationship between the sciatic nerve and the piriformis muscle can theoretically contribute to piriformis syndrome. In the most common normal anatomical arrangement, how does the sciatic nerve traverse the greater sciatic foramen relative to the piriformis?

. The entire nerve passes superior to the piriformis
. The common peroneal division passes through the piriformis, and the tibial division passes below it
. The entire nerve passes undivided inferior to the piriformis
. The common peroneal division passes superior to the piriformis, and the tibial division passes below it
. The entire nerve passes through the muscle belly of the piriformis

Correct Answer & Explanation

. The entire nerve passes undivided inferior to the piriformis


Explanation

In over 80% of individuals, the sciatic nerve passes undivided through the greater sciatic foramen strictly inferior to the piriformis muscle. The most common variation involves the common peroneal nerve piercing the piriformis muscle belly.

Question 1245

Topic: Surgical Anatomy & Approaches

During a lateral transpsoas approach (LLIF) to the lumbar spine at the L4-L5 disc space, the surgeon must carefully navigate the lumbar plexus to avoid neurologic injury. Which nerve pierces the anterior surface of the psoas major muscle and is highly vulnerable during initial psoas muscle splitting and retraction?

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

Correct Answer & Explanation

. Genitofemoral nerve


Explanation

The genitofemoral nerve uniquely emerges on the anterior aspect of the psoas major muscle belly and descends longitudinally. It is at significant risk of stretch or transection during the initial splitting and retraction of the psoas in lateral lumbar interbody fusion.

Question 1246

Topic: Surgical Anatomy & Approaches

A 28-year-old overhead athlete presents with chronic posterior shoulder pain and teres minor atrophy. MRI confirms nerve compression within the quadrilateral space. Which of the following structures defines the superior boundary of this anatomic space?

. Teres major
. Teres minor
. Long head of the triceps
. Surgical neck of the humerus
. Latissimus dorsi

Correct Answer & Explanation

. Teres minor


Explanation

The quadrilateral space is bounded superiorly by the teres minor, inferiorly by the teres major, medially by the long head of the triceps, and laterally by the surgical neck of the humerus. It contains the axillary nerve and the posterior humeral circumflex artery.

Question 1247

Topic: Surgical Anatomy & Approaches

During an ilioinguinal approach for an anterior column acetabular fracture, massive hemorrhage occurs posterior to the superior pubic ramus. This is most likely due to an iatrogenic injury to the corona mortis, which represents an anastomosis between the obturator vessels and branches of which artery?

. Internal pudendal
. Superior gluteal
. Inferior epigastric
. Deep circumflex iliac
. Internal iliac

Correct Answer & Explanation

. Inferior epigastric


Explanation

The corona mortis is an arterial or venous anastomosis between the external iliac (or its branch, the inferior epigastric) and the obturator vessels. It is located roughly 5 cm from the pubic symphysis along the superior pubic ramus and is highly vulnerable during anterior pelvic exposures.

Question 1248

Topic: Surgical Anatomy & Approaches

A patient presents with an inability to extend the metacarpophalangeal joints of the fingers following a surgical approach to the proximal radius. The most likely injured nerve typically enters the supinator muscle beneath a dense fibrous arch. What is the proper anatomical name of this arch?

. Arcade of Struthers
. Arcade of Frohse
. Lacertus fibrosus
. Ligament of Struthers
. Osborne's ligament

Correct Answer & Explanation

. Arcade of Frohse


Explanation

The posterior interosseous nerve (PIN) is at risk during approaches to the proximal radius. The PIN dives under the superficial head of the supinator muscle at the Arcade of Frohse, the most common site of PIN compression.

Question 1249

Topic: Surgical Anatomy & Approaches

To avoid iatrogenic injury to the axillary nerve during a lateral deltoid-splitting approach to the proximal humerus, the split should not extend beyond what distance distal to the lateral edge of the acromion?

. 1 cm
. 3 cm
. 7 cm
. 5 cm
. 9 cm

Correct Answer & Explanation

. 5 cm


Explanation

The axillary nerve runs horizontally across the deep surface of the deltoid approximately 5 cm distal to the lateral edge of the acromion. A deltoid split should be limited to this distance to prevent denervating the anterior portion of the muscle.

Question 1250

Topic: Surgical Anatomy & Approaches

The Smith-Petersen approach to the hip utilizes a superficial internervous plane between which of the following muscle pairs?

. Sartorius and Tensor fasciae latae
. Tensor fasciae latae and Gluteus medius
. Rectus femoris and Gluteus medius
. Sartorius and Rectus femoris
. Gluteus maximus and Tensor fasciae latae

Correct Answer & Explanation

. Sartorius and Tensor fasciae latae


Explanation

The Smith-Petersen (anterior) approach utilizes the internervous plane between the sartorius (femoral nerve) and the tensor fasciae latae (superior gluteal nerve). The deep plane is between the rectus femoris (femoral nerve) and the gluteus medius (superior gluteal nerve).

Question 1251

Topic: Surgical Anatomy & Approaches

A surgeon is performing a surgical exposure of the hip via the anterior (Smith-Petersen) approach. Which of the following represents the correct internervous plane for the superficial dissection?

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

Correct Answer & Explanation

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


Explanation

The superficial internervous plane of the anterior (Smith-Petersen) approach to the hip is between the sartorius (femoral nerve) and the tensor fasciae latae (superior gluteal nerve). The deep plane is between the rectus femoris and gluteus medius.

Question 1252

Topic: Surgical Anatomy & Approaches

A 32-year-old bodybuilder complains of vague posterior shoulder pain and numbness over the lateral aspect of his shoulder. MRI reveals a paralabral cyst compressing structures within the quadrangular space. Which of the following muscles forms the superior border of this space?

. Teres major
. Teres minor
. Long head of the triceps
. Surgical neck of the humerus
. Subscapularis

Correct Answer & Explanation

. Teres minor


Explanation

The quadrangular space is bordered superiorly by the teres minor, inferiorly by the teres major, medially by the long head of the triceps, and laterally by the surgical neck of the humerus. It contains the axillary nerve and posterior humeral circumflex artery.

Question 1253

Topic: Surgical Anatomy & Approaches

A surgeon is planning an extensile posterolateral approach to the tibia to plate a complex tibial plateau fracture. Which internervous plane is predominantly utilized in this approach?

. Soleus (Tibial n.) and Flexor hallucis longus (Tibial n.)
. Gastrocnemius (Tibial n.) and Soleus (Tibial n.)
. Peroneus brevis (Superficial peroneal n.) and Extensor digitorum longus (Deep peroneal n.)
. Peroneus brevis (Superficial peroneal n.) and Soleus (Tibial n.)
. Tibialis anterior (Deep peroneal n.) and Tibialis posterior (Tibial n.)

Correct Answer & Explanation

. Peroneus brevis (Superficial peroneal n.) and Soleus (Tibial n.)


Explanation

The posterolateral approach to the tibia utilizes an internervous plane between the peroneal muscles (superficial peroneal nerve) anteriorly and the soleus, flexor hallucis longus, and gastrocnemius (tibial nerve) posteriorly.

Question 1254

Topic: Surgical Anatomy & Approaches

The standard deltopectoral approach to the shoulder utilizes a true internervous plane. This interval is developed between muscles innervated by which of the following combinations of nerves?

. Axillary and musculocutaneous nerves
. Axillary and medial/lateral pectoral nerves
. Suprascapular and axillary nerves
. Musculocutaneous and medial pectoral nerves
. Thoracodorsal and axillary nerves

Correct Answer & Explanation

. Axillary and medial/lateral pectoral nerves


Explanation

The deltopectoral interval lies between the deltoid (axillary nerve) and the pectoralis major (medial and lateral pectoral nerves). This creates a safe internervous plane for anterior shoulder exposure.

Question 1255

Topic: Surgical Anatomy & Approaches

During an anterior intrapelvic (modified Stoppa) approach for acetabular fracture fixation, significant hemorrhage occurs while dissecting over the superior pubic ramus. This is likely due to an injury to the corona mortis, an anastomosis connecting the obturator vessels with which of the following systems?

. Internal pudendal system
. External iliac or inferior epigastric system
. Superior gluteal system
. Internal iliac system
. Deep circumflex iliac system

Correct Answer & Explanation

. External iliac or inferior epigastric system


Explanation

The corona mortis is an anatomical vascular anastomosis between the external iliac (or inferior epigastric) vessels and the obturator vessels. It is located on the posterior aspect of the superior pubic ramus.

Question 1256

Topic: Surgical Anatomy & Approaches

Following a severe motorcycle crash, a patient presents with paralysis of the latissimus dorsi, deltoid, and all extensor muscles of the arm, forearm, and hand. Sensation is preserved over the lateral aspect of the forearm. The lesion is most accurately localized to which structure of the brachial plexus?

. Lateral cord
. Medial cord
. Posterior cord
. Upper trunk
. Lower trunk

Correct Answer & Explanation

. Posterior cord


Explanation

The posterior cord gives rise to the upper/lower subscapular, thoracodorsal (latissimus dorsi), axillary (deltoid), and radial (extensors) nerves. The lateral cutaneous nerve of the forearm is a branch of the musculocutaneous nerve (lateral cord), explaining the preserved sensation.

Question 1257

Topic: Surgical Anatomy & Approaches

A 25-year-old sustains a displaced fracture of the surgical neck of the humerus. On examination, weakness in shoulder abduction and external rotation is noted. The injured nerve exits the axilla through a space that is bordered superiorly by which of the following muscles?

. Teres major
. Teres minor
. Long head of the triceps
. Lateral head of the triceps
. Subscapularis

Correct Answer & Explanation

. Lateral head of the triceps


Explanation

The axillary nerve passes through the quadrangular space, which is bordered superiorly by the teres minor (posteriorly) and subscapularis (anteriorly), inferiorly by the teres major, medially by the long head of the triceps, and laterally by the surgical neck.

Question 1258

Topic: Surgical Anatomy & Approaches

A trauma patient undergoes open reduction and internal fixation of an anterior pelvic ring fracture via an ilioinguinal approach. The surgeon identifies substantial bleeding from a vascular anastomosis coursing over the superior pubic ramus. This structure primarily connects which two vessel systems?

. Internal iliac and external iliac
. External iliac and obturator
. External iliac and femoral
. Superior gluteal and internal pudendal
. Inferior epigastric and femoral

Correct Answer & Explanation

. External iliac and obturator


Explanation

The corona mortis is a vascular anastomosis between the external iliac (or inferior epigastric) system and the obturator system. It typically crosses the superior pubic ramus approximately 5 to 6 cm from the pubic symphysis, making it highly vulnerable during anterior pelvic surgery.

Question 1259

Topic: Surgical Anatomy & Approaches

A patient sustains a midshaft femur fracture. During an anterolateral approach, the surgeon utilizes the interval between the rectus femoris and the vastus lateralis. Which of the following nerves innervates the muscle that is retracted medially?

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

Correct Answer & Explanation

. Femoral nerve


Explanation

The anterolateral approach utilizes an intermuscular plane between the rectus femoris (retracted medially) and vastus lateralis (retracted laterally). Both muscles are innervated by the femoral nerve, meaning this is not a true internervous plane.

Question 1260

Topic: Surgical Anatomy & Approaches

A surgeon uses a single-incision anterior approach to repair an acute distal biceps tendon rupture. During dissection, a cutaneous nerve is identified and protected to avoid lateral forearm numbness. This nerve is the terminal sensory branch of which parent nerve?

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

Correct Answer & Explanation

. Musculocutaneous nerve


Explanation

The lateral antebrachial cutaneous nerve provides sensation to the lateral forearm and is frequently injured during anterior approaches to the elbow. It is the terminal branch of the musculocutaneous nerve, piercing the deep fascia lateral to the biceps tendon.