3 – Anatomy

The ulnar nerve is a branch of the medial cord of the brachial plexus and contains branches from the ventral rami of the spinal nerve roots C8 and T1

In the proximal 2/3 of the upper limb, the ulnar nerve runs runs in the medial bicipital groove together with the median nerve and the brachial artery and veins; these neurovascular structures are all sandwiched between the triceps brachii and the biceps brachii muscles – and it is anterior to the medial intermuscular septum

Between the middle and distal 1/3 of the arm, the ulnar nerve pierces the medial intermuscular septum and becomes sandwiched between the triceps brachii muscle posteriorly and the brachialis muscle anteriorly and deviates away from the median nerve and brachial vessels which descend postero-medial to the biceps muscle and anterior to the brachialis muscle

In the most distal part of the arm, the ulnar nerve enters the ulnar groove (or sulcus) on the backside of the medial epicondyle of the humerus, while the median nerve and the brachial vessels run anterior to the medial epicondyle