E95 In-Vitro assessment of retropulsion and fragmentation of two stand-alone, handheld lithotripsy devices

Abstract

INTRODUCTION AND OBJECTIVES: Different laser-systems are currently used for stone fragmentation in the upper urinary tract. The aim of our study was to evaluate probe velocity and displacement, retropulsion and fragmentation characteristics two novel devices LithoBreaker® and StoneBreaker® in vitro. METHODS: Max. probe velocities and displacements were measured using high-speed photography (100.000 FPS). Repulsion testing was conducted through a 7.5 Fr ureteroscope in an underwater set-up. The probes were projected against a non-frangible led mass placed in an in-vitro model of the ureter. Repulsion was determined by measuring the distance the lead mass (0.98g) was displaced. Fragmentation efficiency was assessed by measuring the number of single shots required to break Bego Stone hard (15:3) and soft (15:6) with an size of 7.5 mm x 5.5 mm placed on a mesh (edge length 3.15mm) into 3 mm fragments. Mean and standard deviation were computed for all groups and statistical analysis was performed (student’s t-test). RESULTS: The StoneBreaker® yielded the highest velocity of 22.0 1.9 m/sec. followed by the LithoBreaker® assembled with the hard probe guide of 14.2 0.5 m/sec and the soft probe guide of 11.5 0.5 m/sec accordingly. The max. probe displacement for the StoneBreaker® was 1.04 mm and for the LithoBreaker® 0.9 mm and 1.1 mm (hard vs. soft probe guide). Retropulsion produced using the 1mm probes showed no statistical differences between the devices. Using the 2mm probes, the hardness of the damper used significantly changed the repulsion behaviour of the LithoBreaker®. Using the 1mm probe, the amount of single shots for fragmentation of soft Stones was significantly higher for the LithoBreaker® with soft probe guide (31.5 11.31 vs. 21.5 5.29 p 0,05 compared to the StoneBreaker® 11.2 2.65. Fragmentation efficiency for the hard Bego Stones showed statistically significant results (p 0,05). Comparison of the two different probe guides showed that the higher velocity linked to the harder probe guide improved LithoBreaker® fragmentation performance. CONCLUSIONS: The electromechanic LithoBreaker® and the pneumatic Stonebreaker® were shown to be effective in cracking stone phantoms. Fragmentation characteristics improved substantially with the higher hardness of the probe support higher velocity equals higher fragmentation performance of the LithoBreaker®. Retropulsion produced were at comparable levels. More testing is required to more detailed information on impulse frequency and capacity for stone clearance time to be used in clinical practice.