Comparative analysis of occlusion methods for artificial sphincters

Abstract

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.

Artificial sphincters: An overview from existing devices to novel technologies

“…The compression induced onto the tissue by a certain pressure depends on the biomechanical and physiological features of the tissues itself and the specific occlusion method. 3 It is almost impossible to measure the deformation and hightension (stress) levels acting on the biological tissues due to the AS permanence on the body and, especially, during the occlusive action. To overcome the complications and the failures of the existing devices, it is desirable a more rational approach based on the methods of bioengineering.…”

“…To overcome the complications and the failures of the existing devices, it is desirable a more rational approach based on the methods of bioengineering. Computational studies treating the tissue-device interaction and the occlusion methods have been proposed in order to develop new and optimized ASs able to simulate natural sphincters, 3,23,24 minimize tissue damage and ischemia, and improve AS effectiveness and reliability. Preclinical testing of medical devices designed for humans must be evaluated first by a series of in vitro and in vivo tests.…”

“…The main human sphincters, analyzed in this work, are three: the Lower Esophageal Sphincter (LES) regulating stomach contents from the ascent to the esophagus, and the external urethral and anal sphincters, which regulate the passage of urine and fecal matter, respectively. Nervous or anatomical damages can lead to muscular failure, 3 leading to chronical pathologies such as Gastroesophageal Reflux Disease (GERD), characterized by the retrograde movement of gastric contents, fecal incontinence (FI), defined as an uncontrolled passage of fecal material, and urinary incontinence (UI), defined as any involuntary leakage of urine 4 . These pathologies are spreading with the aging of the population, reaching rates from 2.5% up to 45%, worldwide 5–7 .…”

“…Artificial Bowel Sphincters (ABSs), and extra-urethral and endo-urethral artificial urinary sphincters (AUSs) have been developed to address sphincter's incompetence. 3 An ideal AS should reproduce all of the key features of the natural sphincter, such as adaptable compression varying with internal pressure, anatomical constraint fitting, efficiency, reliability, and long-term duration. Traditional ASs are positioned around the duct to guarantee continence and their functional role is based on different mechanical principles.…”

Preliminary study of a novel artificial anal sphincter with perception reconstruction

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Fecal incontinence (FI) is a common clinical symptom, which refers to the inability to control defecation and cause the leakage of intestinal contents. 1 The incidence of FI in adults is 7%-15% and the older the age, the higher the incidence. 2 Studies have shown that the incidence of elderly people over 65 years old is as high as 18.30%.

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