ABSTRACT
Accessory muscles passing through Guyon's canal are common; the most common anomalous muscle at Guyon's canal is the accessory abductor digiti minimi muscle (AADM). The aim of this study was to demonstrate and describe the gross anatomy of an anatomic variant of the AADM relative to the surrounding structures. The AADM was found in the left forearm and hand of a 61-year-old male cadaver during dissection in a gross anatomy course. It was observed by focusing on the shape, the course, and its relationship with the surrounding structures. The AADM originated as muscle fibers from the antebrachial fascia. It coursed downward in the distal forearm and crossed the ulnar nerve and artery obliquely at Guyon's canal. The AADM narrowed and became a long tendon in the hypothenar region. The abductor digiti minimi muscle was partly attached to the tendon of the AADM, running along the tendon. The tendon of the AADM inserted into the ulnar side of head of the fifth metacarpal bone. The AADM was innervated by several twigs from the ulnar nerve. We reported herein another variant of the AADM at Guyon's canal, which may be helpful to surgeons performing diagnoses and surgical procedures.