The authors describe a rare unilateral muscle variation in the thoracic wall combining the pectoralis quartus and chondro-epitrochlearis muscles. A routine dissection was performed in the upper right limb of a male adult cadaver with approximately 35-50 years of age, embalmed in formalin 10%. An accessory muscle, the pectoralis quartus, was identified and was associated with a tendon that was inserted in the medial humeral epicondyle, characteristic of the chondro-epitrochlearis muscle tendon. Such variations have significant clinical relevance to orthopedics, mastology, neural and vascular surgery, and other specialties, for surgical approaches in both the axillary and brachial regions.
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Les anomalies musculaires chez l’homme expliquées par l’anatomie comparée, leur importance en anthropologie. Paris: G. Masson; 1884 [cited 2019 Oct 15]. Available from: https://gallica.bnf.fr/ark:/12148/bpt6k6230258d
BergmanRA. Doubled pectoralis quartus, axillary arch, chondroepitrochlearis, and the twist of the tendon of pectoralis major.
SongH, KimJ, YoonS-P. Coexistence of a pectoralis quartus muscle, a supernumerary head of biceps brachii muscle and an accessory head of flexor digitorum profundus muscle.
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