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

Practical and effective stomal sphincter creation: evaluation in pigs

PURPOSE

Stoma creation frequently presents complications for which there is no satisfactory surgical solution. We reexamined the feasibility of managing stoma continence with an artificial sphincter, addressing the outstanding issues of geometry, electrode disposition, and fatigue resistance.

METHODS

In 6 pigs, 1 rectus abdominis muscle was preconditioned with electric stimulation for 4 weeks by an implanted stimulator. A sphincter was then constructed and tested for its ability to provide continence against saline at a typical intestinal pressure. The result was compared with a sphincter fashioned from the unconditioned contralateral (control) muscle. In each case, stimulation was applied alternately to longitudinal segments.

RESULTS

A 2-layered wrap was required to achieve continence. Sphincters created from the preconditioned muscles could sustain continence continuously for at least 90 minutes.

CONCLUSION

This study establishes a practical approach to the creation of a sphincter from the rectus abdominis muscle in stoma patients. Continence can be achieved only with a double-layered wrap. Fatigue during long-term operation can be avoided by a combination of preconditioning and segmental stimulation of intramuscular nerve branches.

Adaptive change in electrically stimulated muscle: a framework for the design of clinical protocols

Adult mammalian skeletal muscles have a remarkable capacity for adapting to increased use. Although this behavior is familiar from the changes brought about by endurance exercise, it is seen to a much greater extent in the response to long-term neuromuscular stimulation. The associated phenomena include a markedly increased resistance to fatigue, and this is the key to several clinical applications. However, a more rational basis is needed for designing regimes of stimulation that are conducive to an optimal outcome. In this review I examine relevant factors, such as the amount, frequency, and duty cycle of stimulation, the influence of force generation, and the animal model. From these considerations a framework emerges for the design of protocols that yield an overall functional profile appropriate to the application. Three contrasting examples illustrate the issues that need to be addressed clinically.

Experimental model of continent colostomy using rectus abdominis neosphincteroplasty

Background

Use of dynamic myoplasty to create a continent stoma has produced promising results, but long-term stoma continence has not been achieved. The aim of the study was to establish and test a new model.

Methods

Three types of dynamic rectus abdominis sphincteroplasty around a colostomy and two conditioning protocols were tested in ten domestic pigs. Continence was assessed by means of conventional defaecography and neosphincter manometry after 8 and 12 weeks. The neosphincter muscle was studied histologically to assess the transformation of muscle type.

Results

Use of a distal rectus muscle sling surrounding the stoma by 270° with a low-frequency conditioning protocol achieved a continent colostomy for more than 12 h on each of 5 consecutive days. The neosphincter had a 40-mm high-pressure segment with mean pressure of 74 (range 67–82) mmHg. The proportion of type I muscle fibres increased from 38 (range 32–42) to 74 (range 66–78) per cent after 12 weeks of conditioning.

Conclusion

This pilot study demonstrated the feasibility of a continent stoma in an animal model with a dynamic rectus neosphincter. Long-term results should be confirmed in a larger series before use in humans can be considered.