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.

Comparison of abdominal and perineal approach for recurrent rectal prolapse

Purpose

Rectal prolapse is a benign disease in which the rectum protrudes below the anus. Although many studies have been reported on the treatment of primary rectal prolapse for many years, there is a lack of treatment or clinical research results on recurrent rectal prolapse. This study aimed to evaluate the outcomes of surgical approaches for recurrent rectal prolapse.

Methods

We studied patients who underwent surgical treatment for recurrent rectal prolapse disease from March 2016 to February 2021. We analyzed the previous operation methods in patients with recurrent rectal prolapse, as well as the operation time, complication rate, hospital stay, and re-recurrence rates in the perineal and abdominal approach groups.

Results

Out of a total of 239 patients, 41 patients who underwent surgery for recurrent rectal prolapse were retrospectively enrolled. Recurrent rectal prolapses were surgically treated either by the perineal approach (n = 25, 61.0%) or by the abdominal approach (n = 16, 39.0%). The operation times were significantly longer in the abdominal approach than in the perineal approach (98.44 minutes vs. 58.00 minutes, P = 0.001). Hospital stay was significantly longer in the abdominal approach than in the perineal approach (9.19 days vs. 6.00 days, P = 0.012). Re-recurrence rate after repeat repair was not significantly different between the 2 groups (P = 0.777).

Conclusion

Although the perineal approach shortened the operation time and hospital stay, there were no significant differences between the 2 groups in postoperative complications and re-recurrence rate. Both approaches can be good surgical options for the treatment of recurrent rectal prolapse.

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.