Topic Overview

Changes at the Level of Insertion of Coracobrachialis 

Key Changes in Structures Around Mid-Arm

At the level where coracobrachialis is inserted into the medial surface of the humerus, several important structural relationships change:

1. Median Nerve

   • In the upper arm → lies lateral to brachial artery.

   • At mid-arm → crosses anteriorly over the artery from lateral to medial side.

   • Below this level → continues medial to the artery.

2. Ulnar Nerve

   • Lies medial to brachial artery in upper arm.

   • At mid-arm → pierces medial intermuscular septum to enter the posterior compartment, descending toward the medial epicondyle.

3. Nutrient Artery of Humerus

   • Arises from brachial artery near this level → enters nutrient foramen directed downward (toward elbow), consistent with the “growing end” rule.

4. Musculocutaneous Nerve

   • After supplying coracobrachialis, emerges between biceps and brachialis — here it becomes easily visible during dissection.

5. Medial Intermuscular Septum

   • Appears clearly at this level — separating anterior and posterior compartments.

Cubital Fossa 

Definition

• The cubital fossa is a triangular depression in front of the elbow, serving as a passage for major nerves, arteries, and veins between the arm and forearm.

Boundaries

Contents (from medial to lateral)

👉 Mnemonic: “My Brother Throws Rocks”

Relations

• Superficial to fossa: median cubital vein (for venipuncture).

• Deep to fossa: capsule of elbow joint.

Dissection of the Cubital Fossa 

Steps

1. Make a horizontal incision across front of elbow and reflect skin.

2. Identify the median cubital vein connecting cephalic and basilic veins.

3. Remove superficial fascia → note medial cutaneous nerve of forearm and lateral cutaneous nerve of forearm.

4. Expose bicipital aponeurosis → lies superficial to brachial artery and median nerve.

5. Deep to aponeurosis, identify (from medial to lateral):

   • Median nerve

   • Brachial artery → bifurcating into radial and ulnar arteries

   • Biceps tendon

   • Radial nerve (dividing into superficial and deep branches).

6. Observe brachialis (floor medially) and supinator (floor laterally) muscles.

Clinical Anatomy 

1. Venipuncture

• Median cubital vein → preferred site for IV injection and blood sampling.

• It is superficial, fixed by perforators, and separated from the artery by bicipital aponeurosis, minimizing risk of arterial puncture.

2. Pulse Palpation

• Brachial pulse → felt in the cubital fossa, medial to biceps tendon.

3. Blood Pressure Measurement

• Sphygmomanometer cuff placed around arm → stethoscope over brachial artery in cubital fossa.

4. Injury to Brachial Artery

• Supracondylar fracture of humerus → may compress or rupture brachial artery, leading to Volkmann’s ischemic contracture (ischemic necrosis of forearm flexors).

5. Nerve Injuries

• Median nerve injury: sensory loss in lateral 3½ digits, weakness of forearm pronation and wrist flexion.

• Radial nerve injury: wrist drop due to loss of extensor power.

6. Cubital Fossa as a Clinical Landmark

• Used for injections, arterial punctures, venous sampling, and catheterization.

• Also a site for elbow joint aspiration and testing distal neurovascular status after trauma.