Anal Sphincter Reconstruction with the Gluteus Maximus Muscle: Anatomic and Physiologic Considerations Concerning Conventional and Dynamic Gluteoplasty

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Abstract
Myoplasties have acquired an important place in anal sphincter repair. The use of the gluteus maximus muscle for sphincterplasty was reported initially in 1902. However, in 1952, the gracilis sphincterplasty became more popular because of the accessibility of this muscle. Unfortunately, continence rates, especially after graciloplasty, remained unpredictable because of inability to maintain muscle contraction despite training programs. Training should induce a shift in muscle fiber type distribution toward a more fatigue-resistant composition, with predominance of type I fibers. In order to obtain a more pronounced adaptation in the contractile, histochemical, and metabolic properties of muscle fibers, postoperative intermittent long-term stimulation of the graciloplasty was performed. As these results and the results of dynamic cardiomyoplasty with an implantable myostimulator proved to be successful, implantable pulse generators were used after graciloplasty. Subsequently, continence rates after graciloplasties improved significantly. These data encouraged us to perform dynamic gluteoplasties for anal sphincter repair. This paper presents the results in 7 patients treated by conventional and 4 patients treated by dynamic gluteoplasty. Advantages and disadvantages of gluteoplasty were compared with those of graciloplasty. The neurovascular pedicle of the gluteoplasty underwent less traction after transposition compared with the graciloplasty based on cadaver studies. Gluteus muscle transfer far exceeded the amount of muscle tissue of a normal anal sphincter despite muscle atrophy after transposition. This guaranteed a contractile muscle cuff around the anal canal in contrast to the tendinous sling after graciloplasty. Because of the excellent vascularization of the muscle, microperforations of the rectal mucosa caused by submucosal dissection were sealed, and implantation of electrodes and a pulse generator in one surgical intervention was well tolerated. The myoplasty induced a double curvation of the anal canal in contrast to the graciloplasty, which enhanced the natural anorectal angle. Patient evaluation revealed continence for stool in 9 of the 11 patients; 7 of the 11 patients also were continent for liquids, among them all of the patients who had undergone dynamic gluteoplasties. Mean basal pressure after dynamic gluteoplasty was 49 mmHg, which is lower than the reported mean basal pressure (62 mmHg) during stimulation after dynamic graciloplasty. Squeeze pressure after gluteoplasty, with or without stimulation, proved to be similar to or higher than that obtained in dynamic graciloplasty. Comparing our results of conventional gluteoplasty with the results of graciloplasty prior to stimulation, higher pressures were obtained by the gluteoplasty, especially in squeeze pressures. In the last 5 patients intraoperative pressure measurements were used to restore the optimal resting length of the muscle after transposition. An intraluminal pressure of at least 40 mmHg during rest and 80 to 120 mmHg during stimulation should be obtained to guarantee a future continent sphincter.