Design and Evaluation of an Intelligent Artificial Anal Sphincter System Powered by an Adaptive Transcutaneous Energy Transfer System

Objectives The aim of this study was to optimize an intelligent artificial anal sphincter system (AASS) II for patients with severe fecal incontinence. Methods Redesigning and integrating a pressure sensor into the sphincter prosthesis allows us to reduce the sensor volume and makes it suitable for a chronic, ambulatory application. Furthermore, a close-loop frequency control method was designed for the transcutaneous energy transfer system. Finally, a longer working time of the implanted device was obtained by the low-power design of the hardware and software. The new model was implanted in 2 dogs and studied for periods of up to 5 weeks. Results The output voltage induced on the load of 30 Ω, for a variation range in k of 0.12 ~ 0.42, was maintained at approximately 6.8 V with a frequency control range of the 270 ~ 320 kHz. The minimum and maximum output voltages of the pressure sensor were found to be 1.7 V and 2.34 V, respectively, which corresponded to a pressure range of 90 ~ 120 kPa with maximum change rate of approximately 3.7% caused by the temperature variations. Moreover, compared with AASS I, the low-power design resulting in 94% reduction in power consumption. Conclusions The efficacy of the device in achieving continence and sensing the need to defecate was assessed in an animal model. The technical concept and the design of the AASS II turned out to be capable of fulfilling the medical requirements.