Electrical stimulation-induced changes in double-wrapped muscles for dynamic graciloplasty.

HYPOTHESIS Treatment of fecal incontinence has been greatly improved by electrical stimulation of gracilis muscle transposed around the anal canal. Various configurations of the muscle have been used: single alpha, gamma, epsilon muscle loops, split sling, or double wrap. We report herein experimental data on muscle transformation and damage induced by the latter surgical approach. DESIGN, INTERVENTIONS, AND MAIN OUTCOME MEASURES This study was conducted on 4 groups of New Zealand white rabbits. Group 1 had unstimulated transposed gracilis muscles. Group 2 had left transposed gracilis muscles stimulated only. Group 3 had both right and left transposed gracilis muscles stimulated. Group 4 were the controls (not operated on). Muscle properties were studied by electrophysiological,immunohistochemical,and biochemical techniques. RESULTS Transformation from fast-contractile glycolytic muscle fibers into fast-intermediate to slow-contractile oxidative muscle fiber types induced a fatigue resistance of the transposed muscle that has undergone long-term stimulation and muscle alterations characterized by fiber atrophy and fibrosis. CONCLUSIONS Whatever technique of dynamic graciloplasty is used, muscle degeneration associated with mobilization might result primarily from the surgical dissection, whereby collateral blood supply to the gracilis is interrupted and exacerbated by long-term stimulation.