Cross-sectional structures at the elbow

• Median nerve: Lies anterior to the medial epicondyle as the most medial structure in the cubital fossa. It travels between the large humeral and small ulnar head of pronator teres heads before dividing into anterior interosseous nerve (AIN) and median nerve proper.
• Brachial artery: Courses down the medial edge of the cubital fossa, dividing into radial and ulnar arteries at the level of the radial neck.
• Radial nerve: After piercing the lateral intermuscular septum, the radial nerve passes anterior to the lateral epicondyle before dividing into the deep and superficial branches. The deep branch descends through the arcade of Frohse (between supinator attachments) to become the posterior interosseous nerve.
• Radial collateral artery: In the arm, the profunda brachii follows the radial nerve around the spiral groove and across the anterior surface of the lateral epicondyle. At this point, it is known as the radial recurrent artery. It anastomoses with the radial artery just after the bifurcation of the brachial artery.
• Ulnar nerve: Wraps posteriorly behind the medial epicondyle within the cubital tunnel, accompanied by the superior ulnar collateral artery. Passes beneath Osbourne’s ligament before passing between the humeral and ulnar heads of FCU.

Courses in the forearm

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Course of median, ulnar and radial nerves in the forearm

• Median nerve

Crosses the anterior aspect of the medial epicondyle and enters the forearm by passing between the humeral and ulnar heads of pronator teres. At this point, it gives off the anterior interosseous nerve, which innervates the deep muscles of the flexor compartment.

The anterior interosseous nerve descends the anterior surface of the interosseous membrane, while the median nerve proper continues in the plane between FDS and FDP.

Approximately 5 cm proximal to the wrist, the superficial palmar branch arises and travels superficially (not through the carpal tunnel) to supply the skin over the thenar eminence.

The median nerve proper passes through the carpal tunnel on the radial side, then divides into the recurrent branch (motor to the thenar muscles) and digital sensory branches (including palmar digital nerves).

• Ulnar nerve

Passes posterior to the medial epicondyle through the cubital tunnel, deep to Osborne’s ligament. It then passes between the humeral and ulnar heads of FCU, and descends in the anterior compartment in the plane between FCU and FDP.

At the wrist, it enters the hand via Guyon’s canal on the ulnar side of the volar wrist, winding around the hook of hamate, and divides into superficial and deep branches:

• Deep branch: motor to the intrinsic hand muscles

• Superficial branch: sensory to the ulnar 1.5 digits

• Radial nerve

Crosses anterior to the lateral epicondyle, then divides into:

• Deep branch: pierces supinator through the Arcade of Frohse and enters the posterior compartment, running along the posterior surface of the interosseous membrane as the posterior interosseous nerve (PIN).

• Superficial branch: does not pierce supinator; instead, descends the forearm beneath brachioradialis. At the wrist, it passes through the anatomical snuffbox, winding dorsally to supply cutaneous sensation to the dorsum of the hand, particularly the radial 3.5 digits proximally.

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