In-vitro assessment of a new portable ballistic lithotripter with percutaneous and ureteroscopic models.

BACKGROUND AND PURPOSE: The EMS Swiss LithoBreaker is a new, portable, electrokinetic lithotripter. We compared its tip velocity and displacement characteristics with a handheld, pneumatic lithotripter LMA StoneBreaker.™ We also evaluated fragmentation efficiency using in vitro models of percutaneous and ureteroscopic stone fragmentation.

MATERIALS AND METHODS: Displacement and velocity profiles were measured for 1-mm and 2-mm probes using a laser beam aimed at a photo detector. For the percutaneous model, 2-mm probes fragmented 10-mm spherical BegoStone phantoms until the fragments passed through a 4-mm mesh sieve. The ureteroscopic model used 1-mm probes and compared the pneumatic and electrokinetic devices to a 200-μm holmium laser fiber. Cylindrical (4-mm diameter, 4-mm length) BegoStone phantoms were placed into silicone tubing to simulate the ureter; fragmented stones passed through a narrowing in the tubing.

RESULTS: For both 1-mm and 2-mm probes, the electrokinetic device had significantly higher tip displacement and slower tip velocity, P<0.01. In the percutaneous model, the electrokinetic device needed an average of 484 impulses over 430 seconds to fragment one BegoStone, while the pneumatic device needed 29 impulses over 122 seconds to fragment one stone. Both clearance times and number of impulses needed for percutaneous stone clearance were significantly different at P<0.01. Ureteroscopically, the mean clearance time was 97 seconds for the electrokinetic lithotripter, 145 seconds for the pneumatic lithotripter, and 304 seconds for the laser. Comparing the pneumatic device with the electrokinetic device ureteroscopically, there was no significant difference in clearance time, P=0.55. Both the pneumatic and electrokinetic lithotripters, however, demonstrated decreased clearance times compared with the laser, P=0.027.

CONCLUSIONS: The portable electrokinetic lithotripter may be better suited for ureteroscopy instead of percutaneous nephrolithotomy. It appears to be comparable to the portable pneumatic device in the ureter. Further clinical studies are needed to confirm these findings in vivo.