Effect of moderate bone hyperthermia on cell viability and mechanical function.

Extracorporeal hyperthermia treatment of bone followed by its reimplantation may be an optional treatment of bone tumors. In this study, the authors examined the minimal hyperthermic condition in which complete eradication of all viable cells in rat bone can be achieved and the mechanical effect of this treatment on the tested bone. When the results were evaluated histologically by special lactate dehydrogenase activity staining, it was found that complete bone cell death occurred after 30 minutes of heating at 60 degrees C. Cartilage cells, including those of the epiphysis, were more resistant to thermal damage. When the ability of the specimens to proliferate in cell cultures was tested, no growth was observed after heating at temperatures of 50 degrees C or greater. The mechanical stiffness tested in the Instron machine showed decreased bone stiffness at 70 degrees C but no change in the breaking load of the bones. Controlled hyperthermia's ability to eradicate viable cells without significant damage to the mechanical properties may have clinical relevance in limb salvage tumor surgery.