NEUROVASCULAR INTACT MUSCLE TRANSPOSITION FOR ANAL-SPHINCTER REPAIR -EXPERIMENTAL MODEL AND EXPERIENCE WITH DYNAMIC PACING

PURPOSE: To study muscle behavior for anal sphincter repair, radiologi c, manometric, and histologic techniques in a dog animal model have be en used. Special attention was given to the problem of resting length of the transposed muscle. METHODS: The semitendinosus muscle of the do g could be transposed successfully to create a new anal sphincter base d on an intact neurovascular pedicle. The parallel-fibered muscle was split at its distal end and encircled around the anal canal. Manometry was performed intraoperatively and postoperatively. A sufficiently hi gh basal and squeeze pressure had to be obtained intraoperatively to g uarantee a final continent neosphincter. This could be realized by a p rogressive stretching of the muscle until maximum squeeze is reached. In one animal a pacemaker was implanted, and postoperatively a fixed s phincter stimulation protocol was started. Muscle biopsies of the norm al anal sphincter and the neosphincter were taken. RESULTS: 1) Muscle transposition gave a high degree of continence in this experimental mo del, with a mean resting pressure of +/- 40 mmHg and a mean squeezing pressure of +/- 73 mmHg. 2) Electric stimulation of the neosphincter i n one animal influenced the resting pressure but not the squeeze press ure. 3) Muscle fiber type composition changed toward a slow fiber type composition after transposition of the fast muscle and even more afte r stimulation. CONCLUSIONS: 1) Creation of a muscle cuff around the an al sphincter can substitute normal anal sphincter. 2) Adequate stretch of muscle fibers is essential for continence. 3) Electrical pacing he lps preserve resting tension and subsequent continence.