Functional sphincter ani externus reconstruction for treatment of fecal stress incontinence using free latissimus dorsi muscle transfer with coaptation to the pudendal nerve: preliminary experimental study in dogs.

The external anal sphincter (EAS) is a skeletal muscle capable of voluntary contraction to prevent accidental defecation. Current reconstructive options for a severely damaged EAS using local muscle flaps are not always adequate for functional repair. The present preliminary experimental model was designed to assess the feasibility of a neuromicrovascular latissimus dorsi muscle transfer for functional external spincter muscle reconstruction. In nine mongrel dogs, the anal sphincter muscles were totally resected, leaving a mucosal canal in place. A segmental latissimus dorsi muscle was shaped around the anal canal in a circular fashion, with coaptation to the pudendal nerve, and vessel anastomosis at the ischiorectal fossa. Functional evaluation was performed using electromyogram, sphincter manometry, video documentation, and histologic examination with standard and immunohistochemical staining. After 8 months, the remaining three eligible dogs were continent. Muscle function was verified by means of electromyogram, sphincter manometry, and a video record. Histologic and immunohistochemical examination confirmed the functional results, showing only minor zones of fatty and fibrous degeneration. Transplantation of a segmental latissimus dorsi muscle with vascular anastomosis and coaptation to the pudendal nerve has proved to be successful in restoring (voluntary) anal continence experimentally in dogs. Its feasibility for perfect orientation as a neosphincter seems to be superior to any pedicled muscle flap. However, these preliminary results deserve further investigation prior to considering application in humans.