Treatment of Anal and Urinary Incontinence With Free Muscle Transplants
The human anal sphincter system is composed of three muscles. The smooth internal sphincter, the striated external sphincter and the striated puborectalis muscle. The internal sphincter appears to contribute to the tonic closure of the anus at rest and plays no part in maintaining continence when the rectum is distended with faeces. The external sphincter contracts when the pressure in the rectum increases, but it can maintain the contraction only for about 1 minute and plays a relatively minor part in the mechanism of continence. Stephens, a pediatric surgeon interested in anal atresia, pointed out the dominant role of the pubo-rectahs muscle in maintaining continence. The pubo-rectalis muscle is the caudal and medial portion of the muscular floor of the pelvis. The muscle is formed as a U-shaped sling, arising at the back of the pubic bone near the symphysis, and corresponding fibres from both sides unite into a sling behind the rectum at the ano-rectal junction. The pubo-rectahs contracts as soon as increased intrarectal pressure endangers continence. The shortening of the muscle sling pushes the ano-rectal junction forward and upward, making the angle between the rectum and the anal canal more acute, thereby preventing passage of the contents. Stephens has demonstrated that after surgery for imperforate anus, continence could be achieved by use of the puborectalis muscle alone. When the pubo-rectahs muscle is damaged, atrophic or lacking, anal continence is disturbed. In such cases the incontinence can be treated by free muscle transplantation. The aim of the operation is to place a muscle graft as a sling around the rectum, imitating the position and function of the pubo-rectalis muscle.The transplant must be in contract with normally innervated levator ani muscles to permit reinnervation.
KeywordsUrinary Incontinence Anal Incontinence Pubic Bone Imperforate Anus Muscle Graft
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