Y-shaped axillary arch muscle: A case report

The axillary arch is a rudimentary part of the latissimus dorsi. Generally it has a single insertion either into tendon of the pectoralis major, coracobrachialis or fascia over the biceps. Clinically, this anomalous muscular slip is known to cause neurovascular compression of nearby structures. The present case reports an unusual bifurcated fibrous insertion of an axillary arch with Y-shaped limbs. The stem of this muscle was a fleshy belly measuring 7.8 cm. The upper limb of this muscle, measuring 5.6 cm, was attached to the fascia covering the short head of biceps brachii and the coracoid process while its lower limb, measuring 5.1 cm, ended by merging with the brachial fascia over the biceps brachii below the deltoid muscle. The persistence of such a Y-shaped anomalous axillary arch might restrict the hyperabduction of the arm and compress the neurovascular structures passing below it.