MODIFIED INTRACORPOREAL LITHOTRIPSY FOR C EMENT REMOVAL IN TOTAL HIP REVISION ARTHROPLASTY - EXPERIMENTAL GROUNDWORK

Introduction: Particularly problematic in total hip revision arthropla sty is the cement removal out of the depth of the femoral canal; it is also costly in time and effort. The extracorporal shack wave lithotri psy proved to be an unsuitable method. With the present paper we prove d experimentally a newly developed endoscopically controlled modified intracorporal lithotripter (Swiss Orthoclast) for the removal of bone cement. Methods: We tested the efficiency on standardized cement speci mens of different manufacturers in vitro. We compared both conventiona l removing techniques with mallet and chisel and a pneumatically power ed chisel with formalin fixed human femora. During these experiments w e measured the intrafemoral pressure distally to the cement layer. Res ults: We achieved a high energy (max. 450 mJ) and a very effective fra gmentation of the cement (40 mg fragments calculated on the single imp uls of 350 mJ). The endoscopic control ensures a safe control of the c ement removal even in the depth of the femoral canal. No bone damage o ccured macroscopically and radiologically. No heat or toxic products d eveloped. Using the Swiss Orthoclast the intrafemoral pressure was the lowest possible (7 mbar). Even with hammer and chisel or the pneumati cally powered chisel the pressure was too low (max. 55 mbar with malle t and chisel) to cause a fat embolic syndrome. Conclusion: As a result of these experiments we startet with clinical trials (with permission of the Ethic commission) to evaluate the practicability of the modifi ed intracorporal lithotripter (Swiss Orthoclast) for cement removal.