EFFECT OF AN ULTRASONIC DEVICE ON TEMPERATURES GENERATED IN BONE AND ON BONE-CEMENT STRUCTURE

Cement removal during revision arthroplasty can be a tedious, time-con suming process. The usual methods of removing cement include high-spee d drills, chisels, saws and reamers, which are often associated with f racture and/or perforation of the femoral shaft. Ultrasound has been u sed in dentistry to remove plaque and in ophthalmology to remove catar acts and is now applied to cement removal in orthopaedic surgery. Ther e is little data available on the effect of ultrasound on temperatures generated in bone and on its effects on the structure of bone-cement. A cement mantle was constructed in the intramedullary canal in each o f six 10 cm lengths of human cadaver femora. A temperature probe was t hen inserted into predrilled holes and temperatures generated by the u ltrasonic device were recorded under a variety of conditions. In addit ion, a cement cylinder was microscopically evaluated after an ultrason ic tool had been inserted. Temperatures generated by the ultrasonic to ol in cadaver bone were no higher than previously reported temperature s of 140-degrees-C generated by high-speed drills. Furthermore, temper atures at the bone-cement interface never exceeded 60-degrees-C when s aline irrigation was used in conjunction with the ultrasonic tools, an d were below 40-degrees-C l minute after deactivation of the device. M icroscopic examination shows that ultrasound produced local changes in the structure of bone-cement converting it from a microscopically sph erical interlocked material to one that appears homogeneous and granul ar.