Biomechanical Effects of Extracorporeal Shock Wave Lithotripsy: Relation of Applied Voltage and Shock Wave Number to Cell Viability and Stone Fragmentation*

High-energy shock waves (HESW) are harmful to both benign and malignant cells in culture. However, the extent to which the applied voltage (kV) and shock wave number interact to induce both cellular injury and stone fragmentation remain unclear. To investigate these interactions, single-cell suspensions of a human renal carcinoma cell line (TK-10) were subjected to HESW using a Dornier HM3 lithotripter at 15,18, 21, and 24 kV each at 100, 1200, and 2400 shocks. Cell viability was measured by trypan-blue exclusion. Similarly, the relation of kV and shock wave number to stone fragmentation was elucidated by exposing standardized plaster of Paris blocks in three trials to HESW at 16,18,20,22, and 24 kV at 750 shocks and to 250, 500, 750,1000,1500, and 2000 shocks at 18 kV. Stone fragmentation was recorded as the per cent weight loss after passage of the fragments through a 1-mm pore-diameter sieve. Ceil viability decreased as a linear function of kV and as an inverse exponential function of shock wave number. Stone fragmentation, on the other hand, related linearly to both kV and shock wave number. As the total number of delivered shock waves increases, kV apparently becomes the primary determinant of cell viability, whereas kV and shock wave number retain approximately equivalent effects on stone fragmentation over a wide range of power settings.