Development of an implantable artificial anal sphincter by the use of the shape memory alloy

In this study, we developed and assessed an artificial anal sphincter drive n by an shape memory alloy actuator (AS-SMA). The performance characteristi cs of the device were analyzed with a measurement system. Assessment showed that the AS-SMA could generate a pressure of 55 mm Hg at an atmospheric te mperature of 36 degreesC, and displacement of the SMA actuator was 7.5 mm w hen the temperature of the SMA plate was 55 degreesC. To evaluate opening a nd closing, we studied a piglet colostomy model, in which the AS-SMA was im planted around the colostomy in the extraperitoneal space. Flow control tes ts using living porcine intestine revealed that the AS-SMA could maintain f ecal continence against an intestinal pressure of 75 mm Hg. The high pressu re zone corresponding to the location of the device was demonstrated in a m anometric examination. For 6 days after surgery, we activated the AS-SMA tw ice a day and observed the bowel movements. The animal experiment indicated that the AS-SMA is able to control the bowel movements of patients with fe cal incontinence if several problems, such as burning of tissue around the device and compression injury of the intestine, are resolved.