The Anconeus Epitrochlearis Muscle is an anomalous muscle that may cause ulnar nerve compression at the elbow. The anconeus epitrochlearis muscle runs between the medial aspect of the olecranon and the medial epicondyle. It is found in about 28% of cadavers. The anconeus epitrochlearis muscle should not be confused with the anconeus muscle which is a triangular muscle located on the lateral aspect of the elbow joint. The anconeus epitrochlearis muscle can be identified by ultrasound or by MRI. The anconeus epitrochlearis muscle should be considered in evaluating patients with cubital tunnel syndrome. The ulnar nerve travels through a tunnel of tissue (cubital tunnel) that runs under the medial epicondyle. There are multiple causes of ulnar nerve entrapment around the cubital tunnel. All of these causes can lead to compression of the ulnar nerve and one of these causes is the anconeus epitrochlearis muscle.
The arcade of Struthers is different from the ligament of Struthers. The ligament of Struthers deals with median nerve compression. If you find a medial bony process in the distal humerus, this may give median nerve compression at the ligament of Struthers. The Arcade of Struthers is a hiatus in the medial intermuscular septum which will pinch the ulnar nerve. The ulnar nerve can be compressed between the Osborne’s ligament and the MCL. Cubitus Valgus is a deformity in which the elbow is turned outward. Entrapment may also occur due to a spur on the medial epicondyle.
Aconeus epitrochlearis compression on the ulnar nerve is treated using conservative methods first. Surgical excision of the anomalous muscle should be considered in symptomatic patients after failure of conservative treatment.
