Imaging the intermuscular septum in the context of ulnar neuropathy.

Impingement/entrapment of the ulnar nerve by the intermuscular septum at the distal arm is a common cause of recurrent or recalcitrant ulnar neuropathy following ulnar nerve decompression or anterior transposition. Primary entrapment/impingement of the ulnar nerve along the intermuscular septum may also occur. Evaluation with both ultrasound (US) and MRI can identify entrapment of the ulnar nerve at the intermuscular septum, while dynamic assessment with US can also identify dynamic subluxation of the ulnar nerve over the intermuscular septum.