Influence of chemolysis on physical properties and comminution of artificial stones (BON(N)-STONES)

Purpose: Acoustic and mechanical properties show significant differences am ong various stone compositions and are important parameters for the determi nation of stone fragility under shock wave impact. Suggesting that stone fr agility and thus shock wave lithotripsy (SWL) can be altered by varying the physical properties of stones through chemolysis calcium oxalate monohydra te (COM) stones were treated with EDTA and stones composed of uric acid (UA ) with tromethamine. Material and Methods: Synthetic urine served as a control. Using an ultraso und transmission technique longitudinal wave propagation speeds were measur ed at different time intervals. We also measured stone density using a pycn ometer based on Archimedes' principle. From these measurements we calculate d transverse (shear) wave speed, wave impedance and dynamic mechanical prop erties of the artificial stones. Moreover the microhardness of artificial s tones was measured and investigations on shock wave lithotripsy (SWL) combi ned with initial chemolytic treatment of the stones were performed. Results: Both, wave speeds and wave impedances as well as dynamic mechanica l properties only showed a decreasing trend in test groups regarding COM an d UA treated stones suggesting an improvement of stone fragility, whereas n o change was seen concerning all COM and UA control groups. Microhardness o f COM and UA treated stones decreased compared to control groups. Combining medical treatment and SWL the investigations showed a significant impact o f solvents on stone comminution concerning COM and UA stones. Conclusion: In conclusion, the results indicate that appropriate chemical t reatments may provide a useful adjunct modality for improving the efficacy of stone comminution during SWL.