PECTORO-EPICONDYLARIS: A RARE EXTENSION OF THE PECTORALIS MAJOR MUSCLE. Pectoro-epicondilaris: Una rara extensión del músculo pectoral mayor

A very rare case of a thoracobrachialis muscle

The anterior arm compartment includes the biceps brachii muscle, brachialis muscle, and coracobrachialis muscle, and they are characterized by different morphological variations. During standard anatomical dissection of right upper limb, an variant muscle was found. It originated from the fascia covering the long head of biceps brachii and from the tendon of pectoralis major muscle. It also connected to the brachial fascia. It also demonstrated a long thin tendon which was distally attached to the medial epicondyle of humerus. Knowledge about the morphological variations in this region is clinically important because of their direct correlation with neurovascular structures, which may lead to pathologies such as tingling, muscle weakness, paresthesia, and loss of sensation.

Chondroepitrochlearis and a supernumerary head of the biceps brachii

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 38.1 mm 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.