Robust voltage-controlled transcutaneous energy transfer system for artificial anal sphincter

BACKGROUND

The artificial anal sphincter (AAS) system has gained significant attention as a solution for treating fecal incontinence (FI). It relies on transcutaneous energy transfer (TET) as its primary energy source. However, changes in posture or biological tissue can cause misalignment of the coil, resulting in unstable power reception. Inadequate power affects charging efficiency, while excessive power leads to excessive heating at the receiver side. Consequently, achieving safe and constant voltage charging for the AAS becomes a complex challenge.

METHODS

To maintain a consistent charging voltage and overcome the issue of variations in load and coil coupling strength, this article proposes a wireless charging control system that utilizes an LCC-S-type resonant network and phase shift to adjust the transmitting voltage based on feedback charging voltage in real time. In particular, the PI controller and neural network are introduced to change the phase-shift angle swiftly. The dynamic performance is then evaluated under different misalignments and presented with comparative results.

RESULTS

The results indicate that the multilayer perceptron control system outperforms the PI. Under the complex misalignment disturbance, the average error of receiver side load voltage is only 0.007 V, with an average settling time of 960 ms. Additionally, the average temperature at the receiver side is 40.4°C.

CONCLUSION

The experiments demonstrate that the proposed system effectively addresses the misalignment issue in TET during the charging, ensuring constant voltage charging at the receiver side and thermal safety.

Simulation of artificial anal sphincter motion and interaction with intestinal environment using SOFA

BACKGROUND

Artificial anal sphincter is an implantable medical device for treating fecal incontinence. Reasonable simulation facilitates the advancement of research and reduces experiments on biological tissue. However, the device's clamping motion and sensor interaction with the intestine in the simulation still require further exploration. This article presents a simulation of the artificial anal sphincter's clamping and sensing and its interaction with the intestinal environment using the Simulation Open Framework Architecture (SOFA).

METHODS

Firstly, the proposed simulation algorithm and its principles in SOFA are analyzed. Secondly, the clamping motion and sensor system of the artificial anal sphincter are simulated. Thirdly, a finite element model of intestine is established based on the properties of intestinal soft tissue. Finally, the in vitro experiments are performed.

RESULTS

The simulation results indicate that the sensor system of the artificial anal sphincter has good sensing performance during the clamping motion and fecal accumulation process. Experiments have shown that optimal sensory capabilities can be achieved as the posture of the artificial anal sphincter with a roll angle between 20° and 40°. The comparison demonstrates a mean absolute error of 10%-20% between simulation and in vitro experimental results for sensor forces, which verifies the effectiveness of the simulation.

CONCLUSION

The proposed novel simulation achieves a more comprehensive interaction between the artificial anal sphincter motion and intestinal environment. This study may provide more effective simulation data for guidance in improving the performance of sensor perception of artificial anal sphincter for further research.

Research on biomechanical compatibility for a novel artificial anal sphincter with constant force

BACKGROUND

Existing artificial anal sphincter studies have shown that biomechanical compatibility problem between artificial anal sphincter and rectum caused by long-term morphological changes of the tissue surrounding the implanted prosthesis can lead to device failure or tissue ischemic necrosis. In this article, a mechanical artificial anal sphincter with constant force clamping is designed based on the superelasticity of shape memory alloys, which improved the biomechanical compatibility of implantable artificial anal sphincter.

METHODS

Firstly, the anatomical structure and the biomechanical properties of the rectum are analyzed to obtain the size parameters and material parameters of the rectal model. Secondly, a novel artificial anal sphincter with constant force is designed to improve the biomechanical compatibility between the artificial sphincter and the rectum. Thirdly, the static analysis of artificial anal sphincter is carried out by finite element analysis.

RESULTS

The simulation results show that the artificial anal sphincter can maintain a constant clamping force of 4 N within a certain variation range of intestinal tissue thickness, which verifies the constant force characteristic of the artificial anal sphincter. The constant clamping force of the artificial anal sphincter to the rectum is 4 N that is greater than the clamping force 3.99 N required to close the rectum, which verifies the effectiveness the artificial anal sphincter. The surface contact stress and the minimum principal stress of the rectum in the clamping state are less than the pressure threshold, which verifies the safety of the artificial anal sphincter.

CONCLUSIONS

The novel artificial anal sphincter has better biomechanical compatibility and improves the mechanical match between artificial sphincter and intestinal tissue. This study may provide more reasonable and effective simulation data for in vivo experiments of artificial anal sphincter in future, which may provide theoretical and technical support for further research about clinical application of artificial anal sphincter.

A Novel Sensor System for In Vivo Perception Reconstruction Based on Long Short-Term Memory Networks

Monitoring bodily pressure could provide valuable medical information for both doctors and patients. Long-term implantation of in vivo sensors is highly desirable in situations where perception reconstruction is needed. In particular, for fecal incontinence, artificial anal sphincters without perceptions could not remind patients when to defecate and even cause ischemic tissue necrosis due to uncontrolled clamping pressure. To address these issues, a novel self-packaging strain gauge sensor system is designed for in vivo perception reconstruction. In addition, long short-term memory (LSTM) networks, which show excellent performance in processing time series-related features and fitting properties, are used in this article to improve the prediction accuracy of the perception model. The proposed system has been tested and compared with the traditional linear regression (LR) approach using data from in vitro experiments. The results show that the Root-Mean-Square Error (RMSE) is reduced by more than 69%, which demonstrates that the prediction accuracy of the proposed LSTM model is higher than that of the LR model to reach a more accurate prediction of the amount of intestinal content. Furthermore, outcomes of in vivo experiments show that the robustness of the novel sensor system based on long short-term memory networks is verified through experiments with limited data.

Design and evaluation of perception reconstruction with sensor system for artificial anal sphincter based on vector similarity

BACKGROUND

Artificial organs are playing an increasingly important role in medical field. Artificial anal sphincter, as an example, is a widely used medical device for fecal incontinence. Though it could help patients maintain continence, the issue of perception reconstruction is still unsolved, which means that patients cannot control defecation as desired.

METHODS

In this paper, a novel sensor system based on vector similarity has been analyzed and evaluated. The sensor system is a self-packaged strain gauge sensor with a small size 14.5mm x 6mm, especially for medical device implanted in body to reconstruct perception function. In order to overcome the disadvantages of single threshold judgment, a more accurate and reliable judgment standard for content pressure detection in rectum is developed by using vector similarity method. Therefore, in the novel sensor system, standard multi-parameters are comprehensive considered. Furthermore, weight-optimization of sensors are investigated since each sensor has played a different role in detection. Finally, sensor calibration, in vitro and in vivo experiments are established.

RESULTS

In sensor calibration, the result R² > 0.99 presents the strain gauge pressure sensor has a good linearity. After that, a series of in vitro experiments have been conducted. The optimized sensor system shows a high accuracy rate in perception reconstruction, which is 87.5% on early warning and 95% on the alarm. In the following in vivo experiments. The results indicate that the average accuracy of the proposed perception reconstruction module has increased by 17.7%, compared with that without optimized sensor system.

CONCLUSIONS

All of these have proven that the novel perception reconstruction module with sensor system based on vector similarity is more acceptable and reliable.

Preliminary study of a novel artificial anal sphincter with perception reconstruction

BACKGROUND

Artificial anal sphincter (AAS), as an advanced device, has been widely investigated by researchers around world. But the reliability of the structure is still unsatisfactory according to clinical results. What's more, the previous AAS systems are lack the ability of rectal perception as native anal sphincter, which fails to guarantee the safety of the blood supply. In addition, without it, the patient cannot determine when to defecate.

METHODS

In order to improve the reliability and safety of current AAS systems, a novel structure AAS system with rectal perception function, based on pressure sensor module, is proposed in this article. The novel AAS system has a closed three-arm clamping mechanism, with transmission structure of cam-follower system. Then, the design, strength check, optimization and force analysis of the proposed mechanism are investigated. After that, to remodel rectal perception function, the novel sensor module system based on strain gauge is established. Finally, in vitro experiments are conducted.

RESULTS

In vitro test, the sensor system could monitor the rectal pressure accurately. And when H = 24.6 cm (feeling the urge to have a bowel movement), the clamping pressure is 7.39 kPa. which is also less than the safe pressure 9.33 kPa.

CONCLUSIONS

Good performance of the reliability and safety of both novel rectal perception function and new clamping mechanism have been showed.

Sphinkeeper Procedure for Treating Severe Faecal Incontinence-A Prospective Cohort Study

(1) Background: The Sphinkeeper implantation for faecal incontinence (FI) is a novel surgical procedure with limited data on its clinical efficacy. Therefore, we aimed to assess the functional outcome following Sphinkeeper surgery in patients with refractory FI. (2) Methods: Between 2018 and 2020, eleven consecutive patients (9 female) with FI met the inclusion criteria and were enrolled for surgery. Functional outcome and quality of life were evaluated by standard questionnaires pre- and post-surgery. Migration of protheses was demonstrated by 3D endoanal ultrasound. The median follow-up time was eight months (range 3–18 months). (3) Results: The median age was 75 years (range 46–89 years) with a median BMI of 27.4 (range 21.2–30.1). The median number of implanted prostheses per intervention was nine (range 9–10). We found no intraoperative or early postoperative complications. After two months, two prostheses in one patient had to be removed due to pain at the perianal skin site. The median St. Mark’s incontinence score decreased significantly from 22 to 13 points (p = 0.008). The SF-12 showed a significant improvement (35.9 versus 46.3) after surgery (p = 0.028). A migration of at least one prosthesis was observed in ten patients (91%). Six (60%) prostheses were found at the same level in another ten patients. (4) Conclusion: Sphinkeeper implantation is a promising surgical technique for patients with severe FI. The complication rate is low, and short-term functional improvement can be achieved even in severe forms of FI. Migration of implants commonly occurs.

An artificial anal sphincter based on a novel clamping mechanism: Design, analysis, and testing

An artificial anal sphincter is a device to help patients with fecal incontinence rebuild the ability to control the excrement through the anus. In this article, an artificial anal sphincter based on a novel clamping mechanism (AASNCM) is proposed to improve the safety and reliability. The AASNCM, which is powered by a transcutaneous energy transfer system, consists of a novel clamping mechanism, a receiving coil and a control unit. According to design requirements, the novel clamping mechanism model was established. After that, its kinematics and dynamics were analyzed. The results of force tests on the prototype AASNCM show that the maximum values of clamping force and expanding force are 15.859 and 31.029 N, respectively. Comparing the experimental results with theoretical analysis, a good match can be concluded. Finally, in vitro experiments were conducted, and have verified the safety and reliability of the proposed AASNCM.

Design and evaluation of puborectalis-like artificial anal sphincter that replicates rectal perception

While fecal incontinence (FI) is not fatal, it can dramatically decrease the patient's quality of life. An artificial anal sphincter (AAS) is an implantable device that treats FI by replacing a diseased or damaged anal sphincter, thus allowing the patient's continence to be maintained. Here, we report a novel implantable puborectalis-like artificial anal sphincter (PAAS) that replicates rectal perception and has a low risk of ischemia necrosis. Using the pressure sensors embedded in the PAAS, the relationship between the mass of feces and the pressure was determined, and a feces mass estimation model was developed based on in vitro studies. Rectal perception is provided through the real-time monitoring of rectal feces, and the feeling of defecation is quantified based on a comparison between the feces mass and a preset threshold mass. In vivo studies were performed for validation, and the accuracy of the model was determined to be as high as 90%. The performance of the PAAS in the real-time monitoring of rectal feces and its in vivo biocompatibility were also evaluated. The device should further the functionality of existing AAS systems while improving their biosafety and thus expand the applicability of implantable AAS systems in the treatment of FI.

Inhibition of hyperplasia during the implantation of the puborectalis-like artificial anal sphincter

OBJECTIVES

This study aims to extend the implantation lifetime of the puborectalis-like artificial anal sphincter by inhibiting the occurrence of hyperplasia following the implantation process.

METHOD

A new transmission structure was designed inside the puborectalis-like artificial anal sphincter to generate an adequate torque to maintain the feces, even if hyperplasia developed around the prosthetic sphincter. An outer shell was added to the prosthetic sphincter to decelerate the occurrence of hyperplasia on the outer shell side. Medical titanium alloy was tested to replace the nylon-12 prosthetic sphincter, while polyetheretherketone was used for the construction of the power supply unit in the puborectalis-like artificial anal sphincter system instead of nylon-12. In vivo experiments were conducted to evaluate all the methods presented in this study with 10 Pa Ma piglets, 1 domestic pig, and 1 beagle dog during the past 2 years.

RESULTS

Compared with the previous prosthetic sphincter that was equipped with a fixed-axle gear transmission, the new transmission structure is equipped with a planet-gear train managed to generate a prosthetic sphincter output with a 53% larger torque but with the same size and type of motor as that used previously and increase the implantation lifetime by 56%. After the replacement of the nylon-12, the new prosthetic sphincter made of medical titanium alloy succeeded in extending the implanted lifetime by 83%. In addition, the lifetime was increased by 143%, when an outer shell was added to the prosthetic sphincter. Polyetheretherketone significantly decreased the growth rate of hyperplasia around the power supply unit by 44% after the replacement of the power supply unit material. After the combination of all the improvements, the longest implantation lifetime of the puborectalis-like artificial anal sphincter during the in vivo experiments was 7 months and 10 days, which reflected an improvement of 249%.

CONCLUSION

All methods posted in this study were evaluated to be effective to prolong the implantation lifetime of the puborectalis-like artificial anal sphincter. Among the methods proposed, the most effective was the addition of the outer shell to the puborectalis-like artificial anal sphincter. The least effective method was the improvement of the transmission structure. Medical titanium alloy and polyetheretherketone were good replacements for nylon-12 that managed to extend the implantation lifetime and yield a moderate improvement.

Sphinkeeper™ for faecal incontinence: a preliminary report

AIM

A new artificial anal sphincter placed into the intersphincteric space, SphinKeeper™, has recently been proposed to improve outcomes in the treatment of faecal incontinence (FI). We report our preliminary results with short-term follow-up, comparing preoperative and postoperative data after implant of SphinKeeper™ in patients suffering from FI.

METHODS

All patients older than 18 years were included with FI of at least 6 months, incontinence episodes occurring more than once a week and resistance to other conservative treatments. Anorectal manometry, endoanal ultrasound, Cleveland Clinic FI Score, FI Quality of Life score and total number of episodes of FI per week were recorded preoperatively and at the end of the 6-month follow-up period.

RESULTS

Thirteen consecutive patients were treated with SphinKeeper™. No intra-operative nor postoperative complications were reported. Two cases of prosthesis extrusion occurred, and in one case an anterior dislocation was detected. Maximum resting pressure, total number of episodes of FI per week and Cleveland Clinic FI Score were improved after 6 months (P < 0.05).

CONCLUSIONS

SphinKeeper™ could be a minimally invasive procedure for FI with good postoperative outcomes. If these results are confirmed by studies with more patients and longer follow-up, it could be a first-line approach in FI.

Surgical management for fecal incontinence

Fecal incontinence is a socially debilitating condition that can lead to social isolation, loss of self-esteem and self-confidence, and depression in an otherwise healthy person. After the appropriate clinical evaluation and diagnostic testing, medical management is initially instituted to treat fecal incontinence. Once medical management fails, there are a few surgical procedures that can be considered. This article is devoted to the various surgical options for fecal incontinence including the history, technical details, and studies demonstrating the complication and success rate.