Comparative anatomical study of the gracilis and coracobrachialis muscles: implications for facial reanimation.

Abstract

Since the introduction of cross-facial nerve grafting and free vascularized muscle transfer for the treatment of longstanding facial paralysis, substantial progress has been made toward restoration of facial expression that is as normal as possible. Much of the focus has remained on the gracilis as a donor muscle. However, its inherent anatomical characteristics may preclude it from ever being more than simply a mass of contractile tissue in the face. The coracobrachialis muscle, which is the analogue in the arm of the lower limb adductor mass, was proposed as an alternative donor muscle because it was thought that certain features would allow it to improve on the overall results that are currently possible with the gracilis. A comparative anatomical study was conducted to gauge this potential. A total of 133 muscles were analyzed, including 96 dissected specimens, 16 arterial and 14 venous study specimens, and seven neurovascular study specimens. Anatomical parameters were recorded for each muscle and later tabulated. Histological analysis of the nerves to 10 gracilis and 10 coracobrachialis muscles was performed, and the findings were confirmed with intraneural dissection of an additional 20 nerves under an operating microscope. The coracobrachialis was observed to be a practical alternative to the gracilis. Indeed, it has many of the attributes that initially drew attention to the gracilis as a possible donor muscle, including a reliable neurovascular supply, minimal donor-site morbidity, and the option of having two teams operate simultaneously. In addition, it has a size, shape, and form that make it an excellent choice for transfer to the face. It could be easily attached in the face to provide static support as well as animation, because of its long proximal tendon, the thick intermuscular septum along its lateral surface, and, when present, the ligament of Struthers.