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Published July 1, 2000 | public
Journal Article Open

Fracture mechanics model of stone comminution in ESWL and implications for tissue damage


Focused shock waves administered during extracorporeal shock-wave lithotripsy (ESWL) cause stone fragmentation. The process of stone fragmentation is described in terms of a dynamic fracture process. As is characteristic of all brittle materials, fragmentation requires nucleation, growth and coalescence of flaws, caused by a tensile or shear stress. The mechanisms, operative in the stone, inducing these stresses have been identified as spall and compression-induced tensile microcracks, nucleating at pre-existing flaws. These mechanisms are driven by the lithotripter-generated shock wave and possibly also by cavitation effects in the surrounding fluid. In this paper, the spall mechanism has been analysed, using a cohesive-zone model for the material. The influence of shock wave parameters, and physical properties of stone, on stone comminution is described. The analysis suggests a potential means to exploit the difference between the stone and tissue physical properties, so as to make stone comminution more effective, without increasing tissue damage.

Additional Information

© Institute of Physics 2000. Received 20 January 2000; Print publication: Issue 7 (July 2000) We thank Professor G Ravichandran and Professor M Ortiz for their valuable comments on the ideas discussed in this work. This work was supported by NIH grant P01 DK43881.


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