Study on the Mechanical Device, Control System, and Sensor of Biaxial Actuated Artificial Anal Sphincter Actuator for Treating Fecal Incontinence

Abstract

Conventional artificial anal sphincter (AAS) did not have the capability to detect intestinal pressure, which may lead to ischemic necrosis at the clamping site or incomplete fecal release. The biaxial actuated artificial anal sphincter (BAAS) was capable of emulating the functions of the internal and external anal sphincters as well as the puborectalis in regulating defecation. Additionally, it provided real-time feedback on intestinal pressure information and aided in restoring the patient's sensation of defecation. The performance of the actuator was pivotal to the defecation control process within the BAAS, directly influencing its efficacy. Based on the human defecation mechanisms, the BAAS actuator designed in this study comprised primarily mechanical device, control system, and sensor module (SM). The mechanical device was responsible for executing the defecation operation. The control system facilitated information collection, transmission, processing, and storage. It controlled the actions of the mechanical device and established communication with an external controller. The sensor module quantified intestinal pressure and aided patients in regaining a sense of normal defecation. Finally, through tests evaluated sealing performance, mechanical performance, and clamping capability of the BAAS actuator, it was confirmed that the BAAS achieved an IPx8 waterproof rating. When a stall current of 0.615 A, the BAAS actuator generated an output force of 11.65 N, satisfying the clamping requirements of the BAAS system. The BAAS actuator had a maximum control volume of approximately 450 mL and an anorectal angle less than 90 deg, which met the requirements of in vivo experiment. This study provided guidance for a new generation of AAS.