The axillary arch - morphological and histological study with clinical importance

The latissimus dorsi is a muscle of the back which forms the posterior fold of the axilla and its tendon twists to insert into the floor of the intertubercular sulcus of the humerus. Occasionally, the muscle has a muscular slip which crosses the axilla to insert into the pectoralis major. This muscular slip is often termed as "axillary arch." In the present study, we report bilateral axillary arch detected in a 45-year-old male cadaver. The average vertical length of the axillary arch measured 7 cm. The average maximum width of the uppermost, middle and lower part of the arch measured 2, 3.5 and 3.2 cm, respectively. The presence of the axillary arch is an uncommon finding in humans, considering the fact that it is solely found in the animals who prefer to hang on the trees. A histological study of the axillary arch was also performed and it showed skeletal muscle fibres which was uniformly arranged. The presence of the axillary arch may assist in the adduction of the shoulder. It may also compress the axillary vessels and nerves thereby causing resultant symptoms. Prior anatomical knowledge of the presence of axillary arch may be helpful for surgeons performing radical dissection of the axillary lymph nodes and ligation of axillary vessels, clinicians diagnosing abduction syndromes and interventional radiologists interpreting axillary mass in day to day clinical practice.