Variations in the anterior thoracic wall with sternalis muscle and accessory pectoralis major muscle.

ABSTRACT

PURPOSE: The new type of the sternalis muscle needs to be recognized, and the accessory pectoralis major muscle (AcPM) was found between the pectoralis major and minor muscle. It needs to be acknowledged those two different variations can exist in one case. METHODS: The muscle was found on a 73-year-old male cadaver during the dissection class for the anterior thoracic wall. It was proceeded to identify the adjacent structures with precise dissection. RESULTS: The cadaver had sternalis muscle bilaterally. Both side sternalis muscles had a medial and lateral belly and attached to pectoral fascia and rectus abdominis sheath. The pectoralis major muscle (PMaj) had a more profound slip attached to the costal cartilage of rib 4 and 5, which is AcPM. The pectoral nerve traveled through the clavipectoral fascia to the AcPM and through PMaj to the sternalis muscle. CONCLUSIONS: This study presented a new type of sternalis muscle. Two different variations were developed along with the pectoral nerve. It needs to be recognized in the diagnostic images, the muscle rehab outcome, and the surgical complication.