An Anatomical Variation of the Anconeus Epitrochlearis Muscle: A Case Report.

The anconeus epitrochlearis muscle (AEM) is an anatomical variant found in various animal species and some humans, believed to be evolutionarily linked to climbing behavior. It typically spans from the medial epicondyle of the humerus to the olecranon and is innervated by the ulnar nerve. While most AEMs appear as a single-headed muscle, this case report describes a rare three-headed AEM identified during routine cadaveric dissection of an 82-year-old female. On the right side, the AEM showed a typical single-headed structure. On the left side, however, the muscle had three distinct heads, with the proximal head located deep to the ulnar nerve, an unusual configuration not previously documented. All measurements were made using microcalipers. Clinically, the AEM has been associated with cubital tunnel syndrome due to potential ulnar nerve compression. However, some studies suggest it might protect the ulnar nerve compared to the more rigid Osborne's ligament. Variants of the AEM are rare, and to our knowledge, this case of a three-headed AEM is likely the first such report in the literature, contributing new anatomical knowledge with potential clinical relevance.