Dynamic Rectus Abdominis Muscle Sphincter for Stomal Continence

Abstract

Some life-saving surgeries result in the necessity to establish permanent intestinal stomas; this outcome has an undeniable physical and emotional effect on the patient's life. Although patients with permanent stomas reasonably adjust, complications that include peristomal skin irritation, pouching system dysfunction, social inhibition, depression, and sexual dysfunction also have been reported. The quest for intestinal stomal continence has resulted in numerous non-surgical and surgical continent diversion techniques. The use of dynamic myoplasty is one of them. Dynamic myoplasty is a term given to the use of electrical stimulation devices to stimulate surgically elevated muscle flaps. It has been used to treat fecal and urinary incontinence using a gracilis muscle flap neo-sphincter. Another clinical example is use of the lattissimus dorsi muscle to augment the pump function of the heart in patients with chronic heart failure. None of the attempted techniques to maintain stomal continence have enjoyed widespread use because of associated complications or because these techniques were not able to provide complete continence. However, the use of dynamic myoplasty to achieve stomal continence has also met with limited success. Denervation atrophy caused by flap elevation to construct the sphincter and early muscle fatigue caused by continuous electrical stimulation were responsible for these disappointing results. It was our goal to see if we could make an abdominal stoma continent using dynamic myoplasty. A multiphase project was undertaken that was designed to solve the critical issues of denervation atrophy and early muscle fatigue. To solve the problem of denervation atrophy an anatomic feasibility study was undertaken in fresh human cadavers. This first study was designed to determine which local muscle could serve as an innervated and well-perfused muscle flap. The rectus abdominis muscle (RAM) was found to be ideal. Of the two RAM stoma sphincter designs the island flap was found to be superior to the peninsula flap design. The next phase of the study was to identify an animal suitable for the development of a model for stoma sphincter design. In an acute canine study, it was determined that the RAM island flap sphincter design used in human cadavers could be applied to the dog. Using an electrical stimulation device, the muscle was able to be stimulated and to generate peak pressures well above 60 mm Hg (pressure needed to maintain fecal continence in humans). Muscle fatigue was found to be directly proportional to the stimulation frequency and continence was provided at all the tested bowel pressures (30, 65 and 100 mm Hg). These promising acute functional study results paved the way for the initiation of chronic trials incorporating survival operations in dogs. In the first chronic study, it was revealed that the sphincter design was fatigue-resistant for 4 hours up to three months post-op with one of the two training protocols tested. In addition, a second chronic study was undertaken to test whether direct nerve stimulation, as opposed to intramuscular stimulation, would render more favorable results. Although the numbers were too small there was a tendency that the sphincter could be trained faster with direct nerve stimulation. However, electrode failure (displacement and lead fracture) led to a non-functioning sphincter in 63% of the cases when using direct nerve stimulation.