Comparative analysis of occlusion methods for artificial sphincters.

An artificial sphincter is a device that replaces the function of the biological sphincter by occluding the relative biological lumen. The investigation of occlusion methods for artificial sphincters is crucial for a reliable and effective design of such devices. The compression induced onto the tissue by a certain pressure depends on the biomechanical and physiological features of the lumen and on the specific occlusion method. A numerical model and an experimental evaluation are presented here to assess the efficiency of different occlusion methods. Numerical models of circumferential occlusion and clamping occlusion methods to simulate the compression of the biological lumen were developed. Results revealed a relationship between the efficiency of the occlusion method and the physiological condition of the lumen. With differences related to the testing setup, this relationship was also confirmed experimentally by conducting tests on biological simulators. We analyzed the occlusion method to adopt as the physiological pressure (ie, leakage pressure values) changed. In particular, we focused on the urinary incontinence, which is a dysfunction involving the external sphincter surrounding the urethra. In this scenario, we demonstrated that a clamping occlusion is an efficient method to compress the urethra, whose physiological pressures range between 4 and 12 kPa. The clamping occlusion method resulted up to 35% more efficient in terms of sealing pressure than the circumferential one for a closing pressure varying between 2.3 and 11.5 kPa.