CONCOMITANT PECTORALIS MINOR, PECTORALIS QUARTUS AND AXILLARY ARCH

Dr. Suman Verma* and Dr. Sulochana Sakthivel

ABSTRACT

Pectoralis minor, a flat muscle underneath pectoralis major, takes origin from third to fifth ribs and forms an important landmark for axillary artery. Pectoralis quartus is an accessory muscle sometimes seen along lateral margin of pectoralis major. Axillary arch is typically seen crossing over the neurovascular structures in the axilla and its presence can compress the axillary vessels. During dissection in a female cadaver, a bilateral variation in the origin of pectoralis minor along with the presence of pectoralis quartus and axillary arch was found. The pectoralis minor was attached to second to fourth ribs on the right, and second and third ribs on the left side. The pectoralis quartus was seen bilaterally as a broad muscle lateral to the pectoralis minor, and was inserted on the fascia covering the short head of biceps brachii and coracobrachialis. An atypical axillary arch on left side was seen between lateral margin of pectoralis quartus and fascia over short head of biceps brachii. Its identification is especially relevant during axillary lymphadenectomy for delineating the surgical field boundaries. The presence of variant pectoralis minor and pectoralis quartus would affect the approach to pectoral region for breast implant surgeries or mobilizing pectoral muscle flaps for grafting.

Keywords: pectoralis minor, accessory muscles, pectoralis quartus, axillary arch, pectoral muscles.