A biomechanical study to assess orthotopic bladder substitutes in robot-assisted radical cystectomy

In the era of robotic surgery, the evolution of intracorporeal urinary diversion at the time of robot-assisted radical cystectomy has led to a wide variety of orthotopic neobladder designs and surgical techniques. This study aims to evaluate the biomechanical properties of four common neobladder configurations (Studer, Hautmann, Y-shape, and FloRIN) using finite element simulations and to identify the optimal neobladder design in terms of volume and compliance.

Three-dimensional models based on surgical instructions for each neobladder design were created using computer aided design software and transformed into finite element meshes. Numerical simulations were conducted using finite element software with biomechanical tissue properties derived from experimental porcine ileum data. Virtual filling simulations were performed to assess volume and intraluminal pressure.

The Studer neobladder demonstrated the most favorable biomechanical properties in the simulations, with lower intraluminal pressure at high filling volumes and a more gradual pressure-volume response. Compared to the Hautmann, Y-shape, and FloRIN configurations, the Studer model exhibited superior compliance and more homogeneous wall deformation, indicating improved capacity for physiological filling. While the Hautmann design, with its nearly spherical shape, still showed good compliance, especially at moderate volumes, and the Y-shape performed well at maximum filling, the FloRIN model displayed the steepest pressure increase, indicating lower compliance overall. Pressure-volume curves and deformation results supported these observations.

This study provides a biomechanical basis for optimizing neobladder design in robot-assisted radical cystectomy. The Studer configuration demonstrated superior characteristics in achieving high bladder capacity and low intraluminal pressure. These findings may guide urological surgeons in optimizing preoperative planning and improving patient outcomes in orthotopic neobladder reconstruction.