A uniaxial force and stiffness model of the vagina during laparoscopic sacrocolpopexy

Abstract

Background: Laparoscopic sacrocolpopexy is the preferred procedure for restoring vaginal vault prolapse. An assistant uses a vaginal manipulator to position and tension the vault such that the surgeon can dissect the bladder, rectum and vault to eventually suture a synthetic mesh used to suspend the vagina to the longitudinal anterior vertebral ligament. Vaginal vault manipulation requires application of high forces for long periods of time.Methods: This work quantifies the task by measuring and analyzing the interaction forces and the workspace during vaginal vault manipulation. From the measurements we developed a uniaxial model, expressing the increase in interaction force and stiffness of the vagina. By adapting the model parameters, the difference in interaction force and stiffness between moderate and severe prolapse are predicted.Findings: For moderate prolapse the average interaction force and stiffness start at 2.56 N and 0.11 N mm −1 in the tensionfree state, and go up to 20.14 N and 0.53 N mm −1 after complete insertion of the instrument. For severe degrees of prolapse, tissue interaction is much lower starting at 1.68 N and 0.06 N mm −1 while staying limited to 12.20 N and 0.30 N mm −1 at full extension.

Multimodal Robot-Assisted Instrument Interaction for Solo Laparoscopic Sacrocolpopexy

“…Although the human assistant is able to feel the forces applied to the vault, this information is rarely fed back to the main surgeon. During a previous study [12] it was observed that the main surgeon is most often concerned with having proper vault exposure rather than possible overtensioning. Therefore, communication between main surgeon and vaginal manipulator assistant is mostly unidirectional and consists of giving positioning instructions to the assistant.…”

“…According to Akrivos and Barton-Smith, the ViKY UP provides a reduced range of motion when manipulating loads greater than 350 g [8]. This is insufficient for LSC as vaginal vault tensioning forces higher than 20 N have been measured [12].…”

“…A rupture requires emergency surgery to limit blood loss and prevent contamination of the abdomen. Furthermore, vaginal manipulation is physically demanding for the assistant as surgery times are long [11] and the required force to tension the vagina is high [12].…”