Thoracobrachialis- A Cadaveric Study of a Morphological Variation of Pectoralis Major with a Novel Nomenclature and Classification of the Chondroepitrochlearis Muscle

Abstract

Background: Anatomical variations are not uncommon in the pectoral region but the chondroepitrochlearis muscle has been of special interest in history owing to its rarity. Chondroepitrochlearis is a muscular slip that arises from the lower ribs, the inferolateral aspect of the pectoralis major, or the aponeurosis of the external oblique muscle and crosses the axilla to insert on the medial intermuscular septum or the medial epicondyle of the humerus. Multiple variants of this muscle exist including chondroepitrochlearis, chondrofascialis, costoepitrochlearis, thoracoepicondylaris, chondrohumeralis, etcetera. The objectives is to article aims to simplify and standardize the reporting of the chondroepitrochlearis muscle by proposing a novel nomenclature and classification. In this paper, we also present and discuss a case of chondroepitrochlearis. Subjects and Methods : A prospective study was conducted from 2012 to 2020 in the Department of Anatomy, ESIC MC and PGIMSR, Rajajinagar, to identify anatomical variations in the pectoral region. Results: During routine dissection of a male cadaver, an unusual slip was found on the right side and was identified as chondroepitrochlearis. Conclusion: Since the reporting of this rare muscle has been increasing in live patients, taking into consideration the variability in the presentation of the same anatomical structure, to avoid confusion, we propose a novel, blanket nomenclature- “Thoracobrachialis”. We also propose a clinically relevant classification that is based on the level of insertion of the muscle and the possible neurovascular structures involved.