In vitro comparison of shock wave lithotripsy machines

Purpose: We tested the hypothesis that shock wave lithotripsy machines vary in the ability to fragment stones to small size. Materials and Methods: Calcium oxalate monohydrate, calcium hydrogen phosphate dihydrate, cystine and magnesium ammonium phosphate hexahydrate calculi were fragmented in vitro with the 22 kV. Dornier HM3, 20 kV. Storz Modulith SLX, 15.6 kV. Siemens Lithostar C, 24 kV. Medstone STS-T, 26 kV. HealthTronics LithoTron 160, 20 kV. Dornier Doli and 22.5 kV. Medispec Econolith lithotriptors. Stones were given 500 or 2,000 shocks, or the Food and Drug Administration limit. Post-lithotripsy fragment size was characterized using sequential sieves and compared. Results: Stone mass was statistically similar in the cohorts (p >0.94). Fragment size decreased as the number of shocks increased when the machine and stone composition were constant. Magnesium ammonium phosphate hexahydrate calculi were completely fragmented by all devices. At Food and Drug Administration treatment limits the mean incidence per device of calcium hydrogen phosphate dihydrate, calcium oxalate monohydrate, cystine and magnesium ammonium phosphate hexahydrate stones rendered into fragments greater than 2 mm. was 0% for the HM3, Modulith SLX and Lithostar C, 10% for the STS-T, 3% for the LithoTron 160, 29% for the Doli and 18% for the Econolith (p = 0.04); 0% for the HM3, Modulith SLX, Lithostar C, STS-T and LithoTron 160, 4% for the Doli and 9% for the Econolith (p = 0.15); 1% for the HM3, 0% for the Modulith SLX, 1% for the Lithostar C, 10% for the STS-T, 14% for the LithoTron 160, 3% for the Doli and 9% for the Econolith (p = 0.44); and 1% for the HM3, 0% for the Modulith SLX, 1% for the Lithostar C, 10% for the STS-T, 14% for the LithoTron 160, 3% for the Doli and 9% for the Econolith (p = 0.44), respectively. Conclusions: Shock wave lithotriptors vary in fragmentation ability. The HM3, Modulith SLX and Lithostar C machines yield smaller fragments than other machines.