Feasibility of stoma continence, using electrically stimulated rectus abdominis muscle in pigs

To develop surgical techniques to obtain stoma continence with a muscular sphincter, the anatomy (especially innervation and vascularization patterns) of the human abdominal wall muscles was studied in three cadaver dissections. It was found that transposed rectus abdominis muscle might be positioned as a new sphincter (sphincteroplasty). Next, the feasibility was assessed in six pigs, and the rectus muscle was positioned as a sphincter around a Thiry Vella loop. The use of three different surgical procedures has been assessed: 1) a muscular ring of the proximal rectus was constructed and partly denervated the muscle; 2) the distal end of the Thiry Vella loop was pulled through the middle of the rectus muscle, thereby also introducing partial muscle denervation; and 3) a sling was constructed using the distal muscle part. In four of these six pigs, identical procedures were performed also at the left side. These new sphincters were electrically stimulated (with implanted stimulation devices) to study the feasibility of prolonged sphincter contraction independent of will. Stimulation with a frequency of 25 Hz was used at the right and 2 Hz was used at the left sphincters. It was found that electrical stimulation with a frequency of 25 Hz as well as 2 Hz increased the percentage of Type I (relatively fatigue-resistant) muscle fibers significantly from 42 to 65 percent (n = 6) in the right and from 50 to 67 percent (n = 4) in the left rectus muscle into innervated muscle areas of the sphincters. This increase is considered essential for sustained sphincter function. Stoma continence was not achieved because constructing muscular rings (as a sphincter) caused partial atrophy. Construction of a sling using the distal part of the rectus did not cause substantial atrophy, but continence was not achieved because the dorsal side of the Thiry Vella loop was not completely covered with muscle fibers.