Abstract
Introduction Residual lower pole fragments are a common limitation of ureteroscopy, yet the optimal patient positioning to minimize stone migration remains undefined. This study aimed to evaluate the impact of Trendelenburg (HeadTilt) and lateral body roll (BodyTilt) on stone migration within the kidney using physics-based simulation. Methods Three-dimensional collecting system models were generated from delayed-phase CT urograms using RadiAnt™. These hollowed models and an open-source stone model were imported into NVIDIA Isaac Sim™ (physics-based simulator). Stones were placed in the upper pole and subjected to gravity and a random contact force directed toward renal pelvis to simulate stone migration during laser fragmentation. Five angles (0°, 5°, 10°, 15°, 20°) of HeadTilt and BodyTilt, independently and in combination, were tested with 100 simulations per configuration to evaluate lower pole migration. Stone migration between sides was compared with a Mann-Whitney U test. Two-way ANOVA assessed HeadTilt and BodyTilt effects, with paired t-tests and Pearson correlation quantifying their impact. Results From 20 CTs, 20 left and 18 right collecting systems were extracted. Average lower pole migration was 14.0 ± 5.5 (left) vs. 13.2 ± 5.4 (right), with no significant difference (U = 120,568, p = 0.056). Two-way ANOVA revealed significant effects of HeadTilt (F = 929.99, p < 0.0001) and BodyTilt (F = 513.42, p < 0.0001), without interaction (p = 0.37). Paired t-test showed no difference between tilt types (p = 0.056). Increased HeadTilt and BodyTilt correlated with reduced lower pole migration (r = –0.744 and –0.552, p < 0.0001). Conclusion Simulation findings suggest combined head and body tilt can reduce stone migration to the lower pole but challenge the convention of one ideal angle. These adjustments may improve stone clearance during ureteroscopy.
