Electrically stimulated sartorius neosphincter: canine model of activation and skeletal muscle transformation.

The sartorius muscle was transposed into the abdominal cavity of six dogs, passed around a Thiry-Vella loop and sutured to itself to form a neosphincter. The muscle was activated by electrical stimulation and on contraction the neosphincter stopped or reduced the flow of saline through the Thiry-Vella loop in all animals until the onset of muscle fatigue. Continuous low frequency stimulation was used to transform the skeletal muscle, and when studied after a mean of 8 weeks of stimulation (range 6-11 weeks) the neosphincter stopped the flow for a significantly longer period of time (P = 0.027). Associated with the improved neosphincter function was a significant decrease in the fusion frequency (P = 0.003) and prolongation of the stimulus-peak tension time as assessed by a strain gauge sutured to the neosphincter muscle (P = 0.002). The changes in the contraction properties of the skeletal muscle suggest that continuous low frequency stimulation transformed the muscle fibres from type 2 to type 1, resulting in improved fatigue resistance and potential for continuous sphincter activity.