EP750 - A Novel Hydrogel Rectal Phantom for Transanal Minimally Invasive Surgery Simulation

Purpose/Background: Minimally invasive transanal surgical techniques, such as transanal minimally invasive surgery (TAMIS) and transanal endoscopic microsurgery (TEM), allow for safe endoluminal resection of rectal masses. However, surgical trainees have relatively low exposure to such techniques, placing even greater importance on colorectal surgery fellowship and early faculty years to gain these skills. Additionally, the expansion of robotic surgery to transanal procedures augments two related training gaps. Faculty adopting robotic transanal surgery will require training specific to this application of the technology, and there will be fewer opportunities for trainees to learn TAMIS and TEM. Both of these needs can be addressed with an effective simulation model that is easily modifiable to different learning levels.

This study is designed to build evidence for construct validity for a minimally invasive transanal surgery simulation using a novel hydrogel rectal model, focusing on the content validity of performing TAMIS mass resection.

Methods/Interventions: A 3D-printed mold of a rectal lumen with polyps was created using OnShape (PTC, version 1.205) and used to create a phantom of a rectum out of polyvinyl-alcohol hydrogel. A TAMIS operative setup was simulated using an adapted laparoscopic trainer and an electrocautery machine. Colorectal surgery faculty were recruited via convenience sampling and participation was voluntary.

Participants were asked to complete two tasks: complete mucosal resection of a polyp and suture closure of the resection bed. Performance time was recorded separately for each task. They completed pre- and post-task questionnaires regarding their experience with transanal surgery, attitudes towards its training, and views on the realism and utility of the simulation.

This study was determined to be exempt by the local Institutional Review Board.

Results/Outcomes: Three colorectal surgeons of varying experience level participated in the study.

All participants successfully completed the resection with an intact specimen and complete mucosal resection with an average time of 6 min, 4 sec. Due to difficulty, two of the faculty aborted the suture task; one participant completed this task in 25 min, 30 secs, but the tissue was not adequately approximated. The ratings of realism of the simulation varied among the components. The size (4, SD 1.7) and shape of the rectum (3.3, SD 1.2), as well as the sessile polyp appearance (3.3, SD 1.4) were rated highly. The ratings of tissue response to manual and electrocautery manipulation were average (3, SD 0; 3, SD 1) and the realism of tissue response to suturing was rated 2 out of 5 (SD 1). The simulation was thought to adequately represent the ergonomics of TAMIS (3, SD 1.7) and was rated as useful for trainees to learn this aspect (4, SD 1). Overall, participants rated the simulation 4 out of 5 (SD 1) as useful for faculty to practice this technique.

Conclusion/Discussion: The results show that this simulation realistically represents the appearance, tactility, and ergonomics of TAMIS resection of a rectal mass. However, it was not found to be an accurate representation of endoluminal suturing. The model has been modified in response to these results and further studies will reevaluate the content validity. Future directions include testing of the model in the context of robotic transanal minimally invasive surgery. Overall, this study demonstrates that a realistic hydrogel-based simulation for transanal surgery is feasible and can be useful for training residents, fellows, and faculty.

Figure 1
Simulated resection of sessile polyp in hydrogel rectal model using electrocautery.