Development of an electrically stimulated neoanal sphincter

In early surgical attempts to create a neoanal sphincter for patients who are faecally incontinent, skeletal muscle (usually the gracilis) has been transposed around the anal canal. Despite modifications, such as intermittent electrical stimulation, this procedure is likely to fail because the fast-twitch gracilis muscle is incapable of prolonged contraction without fatigue. Long-term electrical stimulation to convert such a muscle to a slow-twitch, fatigue-resistant muscle, though practicable, has yielded inconsistent results. We describe further modifications of this technique. A neoanal sphincter was constructed with an electrically stimulated transposed gracilis muscle in 20 incontinent patients with a deficient anal sphincter, and as part of a reconstruction in 12 patients in whom the anorectum had been excised or was congenitally absent. A totally implanted stimulator was used to convert the muscle from a fast-twitch to a slow-twitch muscle. Other modifications included vascular delay 4-6 weeks before transposition of the muscle, stimulation of the main nerve to the gracilis rather than its peripheral branches, and intermittent higher frequency stimulation. 2-4 of these modifications gave significantly fewer failures than did 0-1. With the new technique, continence has been restored in patients whose only other treatment option was a permanent stoma.