Bilateral Sternalis Muscle With the Absence of Unilateral Sternocostal Part of the Pectoralis Major and Variation of Pectoralis Minor Muscles.

Abstract

This study aims to report a 57-year-old male cadaver with a rare muscular variation of the sterno-pectoral region.An unusual sternalis muscle was observedon both sides, arising from the external oblique muscle aponeurosis. The fibers converged upwards and medially in a curved course, producing a bundle 99.50 mm long on the right side and 74.60 mm on the left. The muscles on both sides were supplied by the second, third, and fourth intercostal nerves. In the right pectoralis major (PM) muscle, the sternocostal head was completely absent, and the clavicular head arose from the medial two-thirds of the clavicle, whereas abdominalfibers arose from the aponeurosis of the external abdominal oblique muscle and ran upward and laterally and joined the clavicular fibers with a wide triangular gap. On the left side, there was an anatomically normal PM muscle. The origin of the pectoralis minor was unusually high on both sides. The morphological variations of sterno-pectoral musculature have significant implications for clinical practice, whichallows more precise surgical or radiological outcomes. Clinicoradiological evaluation of these variationsis important to achieve appropriate dissection planes during chest wall surgery.