Dynamic Graciloplasty For Anal Reconstruction In Situ In A Canine Model

Permanent colostomy inevitably overloads patients with lots of inconvenience and psychological pressure while saving their lives. Thus, how to preserve or reconstruct the patient's ability of fecal control, without permanent colostomy, continues to be one of the hottest topics in general surgery. Earlier studies have proven that fast-twitch, fatigue-prone type II muscle could transform to slow-twitch, fatigue-resistant type I muscle by chronic low frequency stimulation (CLFS). Consequentially, based on the traditional graciloplasty, dynamic graciloplasty (DGP), a new surgical operation developed and has been used to clinical therapy. We applied this new approach on dogs to investigate the feasibility of DGP on large animals, furthermore, to evaluate the possibility of applying the operation on patients.Purpose : A canine model with reconstructured neosphincter was developed by replacing the normal sphincter with the gracilis muscle, which was stimulated chronically with low frequency electrical currents. To evaluate the possibility and effectiveness of the muscular transformation and alternation to normalsphincter, the ultraconstructure and function of neosphincter were observed by histochemical, electron morphological and manometric techniquesMaterials and Methods: The dogs were divided into 2 groups. In group 1 (control group), on the stage 1, the gracilis muscle were dissected in situ, the distal minar vascular pedicles ligated, and manometry performed intraoperatively; In group 2 (stimulation group), on the stage 1, the same operations were performed, and one myostimulator imbelled in a subcutaneous pocket in the abdominal wall with 2 intramuscular electrodeswas implanted into the gracilis muscle, then this group were stimulated chronically since 7 days postoperatively with low frequency electrical currency (lOHz, 1.2V and 210ms for 6 weeks). On the stage 2, abdominoperineal resection of anus and graciloplasty for anal reconstruction were performed on all dogs. After 2 weeks recovery, manometry and muscular fatigue-resistant curve (MFRC) were observed while myostimulator is switched off and on. Then muscle biopsies of the neosphincter were taken for microscope and ultrastructure observation.Results: After CLFS, the percentage of I type fibers in the stimulation group was higher than the control group (48.1 ?.93% vs. 26.83 + 3.44%, P < 0.001). There are also significantly different in the total average width of Z-line and M-line in muscular fibers between 2 groups (P < 0.001). As the function, there is no difference in BP and BNP between 2 groups (P>0.05), but FNP is different significantly (P < 0.01), and the shape of MFRC in the stimulation group was smoother with a longer platform.Conclusion: Dynamic graciloplasty is technically feasible. With chronic low frequency electrical stimulation (CLFS), the gracilis muscle has an adaptive mechanism to improve the fatigue resistance, making it more suitable for the alternative function of neosphincter.