Functional Evaluation of an Artificial Anal Sphincter Using Shape Memory Alloys

Challenges faced in the clinical application of artificial anal sphincters

Fecal incontinence is an unresolved problem, which has a serious effect on patients, both physically and psychologically. For patients with severe symptoms, treatment with an artificial anal sphincter could be a potential option to restore continence. Currently, the Acticon Neosphincter is the only device certified by the US Food and Drug Administration. In this paper, the clinical safety and efficacy of the Acticon Neosphincter are evaluated and discussed. Furthermore, some other key studies on artificial anal sphincters are presented and summarized. In particular, this paper highlights that the crucial problem in this technology is to maintain long-term biomechanical compatibility between implants and surrounding tissues. Compatibility is affected by changes in both the morphology and mechanical properties of the tissues surrounding the implants. A new approach for enhancing the long-term biomechanical compatibility of implantable artificial sphincters is proposed based on the use of smart materials.

A novel artificial anal sphincter system in an in vitro and in vivo experiment

This paper presents some of the latest progress in the development of a novel artificial anal sphincter system (AASS) to treat severe fecal incontinence. We have redesigned and integrated an intelligent, remote-controlled artificial anal sphincter based on biological signal feedback mechanisms. The device consists of an external telemetry unit, an internal artificial anal sphincter (IAAS), and a transcutaneous energy transfer system (TETS). The mechanical medical micropump of the IAAS can realize bidirectional flow with a maximum flow rate of 8.5 ml/min and can build backpressure up to 170 kPa. The design of the prosthesis reduces occlusion pressure and allows for low inflation volumes (9 mL-10.5 mL); operating pressures between 4.05 kPa and 7.16 kPa indicate that the risk of ischemic injury to the bowel is minimal. Furthermore, the rechargeable battery based on TETS puts the operation time at an estimated 2 days. The performance characteristics of the AASS and its efficiency in achieving continence and sensing the stool inside the anorectum were evaluated in vitro and in vivo in a pig model. Experimental results confirm that the system can maintain continence and build the sense of defecation successfully. Moreover, this innovation can be integrated into not only severe fecal incontinence, erectile dysfunction, and therapy-resistant reflux disease, but also morbid adiposity therapeutic AASS applications.

Assessment and in vitro experiment of artificial anal sphincter system based on rebuilding the rectal sensation function

In this paper, a novel artificial anal sphincter (AAS) system based on rebuilding the rectal sensation function is proposed to treat human fecal incontinence. The executive mechanism of the traditional AAS system was redesigned and integrated for a simpler structure and better durability. The novel executive mechanism uses a sandwich structure to simulate the basic function of the natural human anal sphincter. To rebuild the lost rectal sensation function caused by fecal incontinence, we propose a novel method for rebuilding the rectal sensation function based on an Optimal Wavelet Packet Basis (OWPB) using the Davies-Bouldin (DB) index and a support vector machine (SVM). OWPB using a DB index is used for feature vector extraction, while a SVM is adopted for pattern recognition.Furthermore, an in vitro experiment with the AAS system based on rectal sensation function rebuilding was carried out. Experimental results indicate that the novel executive mechanism can simulate the basic function of the natural human anal sphincter, and the proposed method is quite effective for rebuilding rectal sensation in patients.

The possibility of muscle tissue reconstruction using shape memory alloys

Severe dysfunction of muscle tissues can be treated by transplantation but the success rate is still not high enough. One possibility instead is to replace the dysfunctional muscle with artificial muscles. This article introduces a unique approach using shape memory alloys (SMAs) to replace the anal sphincter muscle for solving the problem of fecal incontinence. The use of SMAs that exhibit a two-way shape memory effect allows the device to function like a sphincter muscle and facilitates simple design. In this article, we will give a brief introduction to the functional material-SMA-together with its medical applications, and will follow this with a description of the recent progress in research and development of an SMA-based artificial sphincter. The possibility of its commercialization will also be discussed.

Swallow stent with hyperthermia function

An operation of an esophagus cancer is one of the most difficult operations even now, when medicine progressed. One of the most important points is the difficulties of esophagus reconstruction. In an operation, since the stomach and intestines are used as a substitute, an invasion becomes large and an operation of elderly people becomes difficult. Although the improvement in a life prognosis is expected if cancer is removable, there are a lot of cases, who were too late for surgery of the esophageal cancer at the time of diagnosis. Then, a Swallow Stent with Hyperthermia function for the terminal esophageal cancer patients, for whom an operation cannot be conducted, was invented. The Swallow Stent with Hyperthermia function has three characteristics. 1. Completely noninvasive, 2. Hyperthermia on the carcinoma tissue. 3. Swallow function. Possibilities are expected as one of the alternative candidates for a terminal esophagus cancer therapy.

Biochemical evaluation of an artificial anal sphincter made from shape memory alloys

Severe anal incontinence is a socially incapacitating disorder and a major unresolved clinical problem that has a considerable negative impact on quality of life. In this study, we developed a new artificial anal sphincter using shape memory alloys (SMAs) in order to improve the quality of life of such patients and evaluated the influence of this sphincter on blood serum chemistry in animal experiments. The artificial anal sphincter was driven by two Ti-Ni SMA actuators sandwiching the intestine and was implanted in three female goats. Blood was collected from the jugular vein on days 1 and 4; at weeks 1 and 2; and at months 1, 2, and 3, postoperatively. Biochemical parameters including total protein, albumin, total bilirubin, aspartate amino-transferase, blood urea nitrogen, creatinine, and C-reactive protein were examined. The time courses of total bilirubin and aspartate amino transferase of the three goats were within the baseline levels after 1 week of implantation and remained normal, demonstrating no liver function complications. The blood urea nitrogen and creatinine levels remained within the normal range, indicating no renal function complications. The total protein and albumin fluctuated within the normal range throughout the duration of this study. In these goats, it was also found that the level of C-reactive protein did not increase and that there was no stricture of the intestine where the artificial sphincter was attached. Our findings indicate that the artificial sphincter SMA demonstrated no adverse influence on blood serum chemistry and exhibited an effective system performance.

Passive mechanical properties of large intestine under in vivo and in vitro compression

This paper presents experimental data obtained from both in vivo and in vitro compression of the large intestine of goat. In vivo experimental data were obtained from compression tests on the large intestine of an anesthetized goat using force-displacement acquisition equipment. In vitro experimental data were also obtained from tissue excised after the in vivo experiments, and two types of data were then compared. The results demonstrated that the stress values had a strong dependence on the compressive rate in the in vivo experiments, although such effect was not distinct in the in vitro experiments. Additionally, at a lower compression rate, the intestinal tissues were found to be stiffer in the in vitro experiments than in the in vivo ones. This paper is a preliminary report on the mechanical properties of the large intestine based on in vivo and in vitro experimental data.

Preclinical development of SMA artificial anal sphincters

This article presents some progress in the development for preclinical trials of an artificial anal sphincter using shape memory alloys. The novel device has been proposed and developed by the author's group at Tohoku University. It has two dominant features different from other systems, which are either clinically available or still under development. One is that a solid driving element, a combination of shape memory alloy (SMA) ribbons and silicone elastomer sheets with a layered structure, is adopted for the opening and closing functions of the artificial sphincter. The other is a sandwich mechanism for the closing of bowel to reduce the risk of buckling induced ischemia which has been reported in hydraulically driven artificial sphincters with a radial squeezing mechanism. The device has fewer parts inside the body and therefore be implanted more easily. A new design eliminating the risk of heat burns enables long-term implantation and brings the device closer to practical use. Functionality and safety of the device have been proved in three-month animal experiments.