Bilateral Sternal Muscle, Description of a Case and Clinical Implications

The sternal muscle corresponds to a supernumerary muscle variant of the thoracic musculature, whose oldest description dates to 1604. Throughout history it has been called the "episternal", "presternal", "rectus thoracis" or "rectus sternalis" muscle. It is located between the superficial fascia and the pectoralis major muscle, has a prevalence of between 3 % and 8 % in the general population, presents unilaterally or bilaterally, exhibits a high interracial variability and can be the cause of diagnostic dilemmas during surgery and imaging examinations. Dissection in an adult male cadaver. Two sternal muscles were found connected superiorly by a central tendon. The right sternal muscle extended from the sternal manubrium to the right seventh costal cartilage. The left sternal muscle extended from the sternal manubrium to the left sixth costal cartilage. The innervation was given by anterior cutaneous branches of the intercostal nerves and the vascularization by perforating branches coming from the internal thoracic vessels. The sternal muscle presents a high morphological variability and the prevalence is influenced by racial factors. Knowing this muscle variation enriches the diagnostic and surgical capacity, reducing the possibility of iatrogenesis.