Chondroepitrochlearis and a supernumerary head of the biceps brachii.

Abstract

Unique variants of the pectoralis major and biceps brachii were found during a routine student dissection of a 96-year-old Caucasian female's axilla and brachium. The donor cadaver had bilateral presentation of a muscle originating from the pectoralis major, near the lateral lip of the intertubercular groove, extending obliquely to insert on the medial intermuscular septum and medial epicondyle of the humerus. This muscle variant is currently described as a rare presentation of the chondroepitrochlearis, potentially a remnant of the panniculus carnosus in man. Often considered to be a thin, slender muscle taking origin from the true ribs, the right-side chondroepitrochlearis described in this report was notably larger-to the authors' knowledge-than all other published cases, measuring 38.1mm at the widest point. Meanwhile, another small muscle originating on the posterior surface of the pectoralis major tendon was present. Due to its insertion, the muscle was identified as a supernumerary portion, or a third head, of the biceps brachii. The proximal attachment of both the chondroepitrochlearis and the third head of the biceps brachii could impose functional limitations on the pectoralis major.