Muscle transformation of the sartorius muscle in a canine model: clinical impact for electrodynamic graciloplasty as a "neosphincter"

Electrically stimulated rectus abdominis muscle flap to achieve enterostomal continence: development of a functional canine model

BACKGROUND

Dynamic myoplasty has many clinical applications and has proven to be a versatile surgical procedure with great promise. This procedure has been used to achieve fecal/urinary continence, as in the dynamic graciloplasty, and to augment cardiac ventricular function, as is commonly seen with dynamic latissimus cardiomyoplasty. In the present study, the authors describe a functional innovative island flap sphincter created from the rectus abdominis muscle in a large-animal model to provide stomal continence for future clinical studies.

METHODS

The caudal region of the rectus abdominis muscle in eight mongrel canines (23 to 25 kg) was investigated through anatomical dissections during which the location of the neurovascular pedicles and the intersegmental muscle dimensions between the muscle inscriptions were noted. The rectus abdominis muscle was used to create functional dynamic stomal sphincters that were trained with subcutaneously implanted pulse stimulators.

RESULTS

The neurovascular pedicles were consistently found in similar locations along the posterior medial aspect of the caudal portion of the canine's rectus abdominis muscle. The vertical height of the deep inferior epigastric pedicle and caudal intercostal nerve muscular mean entry points were 6.75 +/- 1.89 cm and 7.44 +/- 0.86 cm, respectively. The mean caudal intersegmental muscle length of the rectus abdominis muscle used to create the sphincter was 9.69 +/- 1.81 cm.

CONCLUSIONS

The canine rectus abdominis muscle has reliable anatomical locations where the neurovascular pedicle may be found. This canine muscle may be used to create a continent island flap stomal sphincter. This large-animal sphincter model is versatile, durable, and easy to manipulate, with minimal morbidity to the animal.

Systematic review of dynamic graciloplasty in the treatment of faecal incontinence

Background

The aim of this systematic review was to compare the safety and efficacy of dynamic graciloplasty with colostomy for the treatment of faecal incontinence.

Methods

Two search strategies were devised to retrieve literature from the Medline, Current Contents, Embase and Cochrane Library databases up until November 1999. Inclusion of papers depended on a predetermined protocol, independent assessments by two reviewers and a final consensus decision. English language papers were selected. Acceptable study designs included randomized controlled trials, controlled clinical trials and case series. Forty papers met the inclusion criteria. They were tabulated and critically appraised in terms of methodology and design, outcomes, and the possible influence of bias, confounding and chance.

Results

No high-level evidence was available and there were no comparative studies. Mortality rates were around 2 per cent for both graciloplasty and colostomy. Morbidity rates reported for graciloplasty appear to be higher than those for colostomy. Dynamic graciloplasty was clearly effective at restoring continence in between 42 and 85 per cent of patients, whereas colostomy is, by its design, incapable of restoring continence. However, dynamic graciloplasty is associated with a significant risk of reoperation.

Conclusion

While dynamic graciloplasty appears to be associated with a higher rate of complications than colostomy, it is clearly a superior intervention for restoring continence in some patients. It is recommended that a comparative, but non-randomized, study be undertaken to evaluate the safety of dynamic graciloplasty in comparison to colostomy, and that the procedure should be performed only in centres where it is carried out routinely.

Long-term results of modified graciloplasty for sphincter replacement after rectal excision

OBJECTIVE: Restoration of the anal sphincter by means of electrically stimulated (dynamic) graciloplasty is a new therapeutic option for patients with severe faecal incontinence or those having abdomino-perineal resection (APR) of the anorectum. The present study reviews the outcome of total anorectal reconstruction (TAR) after APR for low rectal cancer or recurrent anal cancer. METHODS: From 1992 to 2000, 35 of 64 patients treated with dynamic graciloplasty had a TAR performed either synchronously (n=26) or as a secondary procedure one to five years after rectal excision (n = 9). RESULTS: The most frequent complication was injury or erosion of the neorectum (n = 9) which, was avoided with increasing surgical experience. Defaecation disorders and consequent incontinence were the most common functional problem and had to be treated with periodical enemas. CONCLUSION: Although sphincter replacement by means of TAR after APR led to poorer functional results than those achieved in patients treated with dynamic graciloplasty for faecal incontinence, TAR remains a valid treatment option for patients who do not tolerate a permanent stoma.

Analysis of chronic morphologic changes of small bowel in electrically stimulated canine island-flap rectus abdominis muscle stomal sphincters

PURPOSE

Dynamic myoplasty to achieve fecal continence has been used in humans with varying results. A potential complication of the use of dynamic skeletal sphincters to attain fecal continence is the development of ischemic strictures within the bowel encircled by the functional sphincter. This study examines the histologic changes present in the bowel wall used to create a functional dynamic island-flap stomal sphincter in a chronic canine model.

METHODS

The rectus abdominis muscles of canines were used to create island-flap stomal sphincters. Eight dynamic island-flap stomal sphincters were created from the rectus abdominis muscles in mongrel dogs by wrapping them around a blind loop of distal ileum that was no longer in continuity with the terminal small bowel. Temporary pacing electrodes were secured intramuscularly near the intercostal nerve entry point and connected to a subcutaneously placed pulse stimulator. Two different training protocols resulting in different contractile properties were used: Program A (n = 4) and Program B (n = 4). The island-flap sphincters were trained over 3 months to generate stomal intraluminal pressures of more than 60 mmHg in all animals. The intact sphincters, normal bowel, and contralateral stomal bowel were obtained when the animals were killed. Specimens were processed with paraffin embedding, sectioned, and stained with trichrome and hematoxylin-and-eosin stains. Measurements of the different bowel layers were made with a micrometer. The muscular sphincters were biopsied before and after training. Fiber-type histochemistry was performed with a monoclonal antibody to the fast isoforms of myosin. Pretrained and posttrained skeletal muscle specimens were examined histologically.

RESULTS

The bowel wall within the functional dynamic stomal sphincter did not exhibit any significant architectural changes related to ischemic fibrosis or mucosal damage. A significant fiber-type conversion was achieved in both training groups with Programs A and B, with a >50 percent conversion from fatigue-prone (type II) muscle fibers to fatigue-resistant (type I) muscle fibers. Biopsy specimens revealed that fiber-type transformation was uniform throughout the sphincters. Skeletal muscle fibers within both groups demonstrated a reduction in their fiber diameter. There was no evidence of significant fibrosis or deposition of fat within the skeletal muscle of the sphincters.

CONCLUSION

Results of our experiment suggest that our anterior abdominal wall dynamic island-flap stomal sphincter, which generates a contractile force over the bowel wall capable of producing enough stomal pressure to achieve fecal continence, is not intrinsically harmful to the bowel that it encircles. The transformation of skeletal muscle to fatigue-resistant (type I) fibers occurred uniformly throughout the skeletal muscle sphincters without evidence of muscle fiber damage or significant fibrosis.

Restoration of anal sphincter function by single-stage dynamic graciloplasty with a modified (split sling) technique

BACKGROUND

Controlled muscle fiber conversion by electrostimulation makes transformation of fast twitching type II muscle fibers to slow twitching type I fibers possible, which gives skeletal muscles the capacity for tetanic contraction. This phenomenon has been recently applied in the so-called "dynamic graciloplasty" to restore function of an insufficient or excised anal sphincter. This paper describes our results with this method in patients with fecal incontinence or following an abdomino-perineal resection (APR) of the anorectum.

METHODS

From April 1992 through April 1997, 28 patients (12 women and 16 men) were treated by dynamic graciloplasty. The median age was 53.5 years (range 16 to 79). Indications were as follows: APR + synchronous restoration of the excised sphincter by graciloplasty (n = 12); total anorectal reconstruction (TAR) following APR in the past (n = 6); Patients with acquired fecal incontinence (n = 4); and Congenital atresia (n = 6). Muscle transposition, implantation of stimulation electrodes and pulse generator were done as a single-stage procedure, the "neosphincter" was wrapped in a modified technique (split-sling technique). Muscle transformation was performed by controlled neuromuscular stimulation during 8 weeks (from 1992 to 1995) and 4 weeks (since 1996), respectively.

RESULTS

No postoperative mortality (90 days) was observed in either group. In our early experience, rectal injury occurred in 4 patients as the most prominent complication. Evaluation of the functional outcome showed the best results in patients operated either for congenital of acquired incontinence who achieved a continence for solids and liquids or solids alone, respectively (1 or 2 according to Williams' score) in 90%, while patients following APR showed a satisfying outcome (continence for solids and liquids, solids alone or with occasional episodes for liquids) in only 55.5%. In patients following APR, defecation disorders turned out to be the most prominent functional problem and had to be treated by enemas.

CONCLUSION

In this series, we have been able to perform dynamic graciloplasty as a one-stage procedure using a modified muscle wrap (split-sling-technique) thus reducing the time period until continence could be achieved to 7 weeks. We found the appropriate tension of the muscle wrap essential to prevent direct injury to the rectum as it was seen in our early experience. For this reason, we have introduced a modified device to perform intraoperative anal manometry and to measure pressures created by the neosphincter objectively.