OBJECTIVE This study aimed to develop an alternative thermoinactivation method for biological inactivation of microscopic contamination on the cavity wall following curettage of local aggressive tumors. Hot saline irrigation was applied at various temperatures to bone cavity, with or without tourniquet on the extremity and temperature changes and local effects were investigated in vivo. METHODS Bone cavities 12 cm3 in size were created in the condylar regions of the hind legs in nine female adult sheep. The cavities were irrigated by hot saline solution at 60, 70, 75, 80, or 100 degrees C, with and without the presence of a tourniquet, and the temperatures 1, 2, 3, and 10 mm distant to the cavity wall were recorded. The animals were sacrificed postoperatively at 2 days, 3 and 6 weeks, and 3 and 7 months for histologic studies. RESULTS The mean body temperature and temperature inside the bone prior to surgery were measured as 38.1 degrees C and 27.34 degrees C, respectively. Tourniquet application caused a mean decrease of 1.5 degrees C (range 1-2 degrees C) in bone temperature. The highest temperatures measured below 80 degrees C and at 80 degrees C were 55.5 degrees C and 62.5 degrees C in the cavity, and 40.5 degrees C and 42.5 degrees C in the bone, respectively. At 100 degrees C, the color of the bone together with the surrounding soft tissue and muscle tissue turned to yellow-brown-black, and the animal died on the second postoperative day. At temperatures <or=80 degrees C, the color of the bone and surrounding tissues appeared normal and no early complications were encountered. Histologic studies showed no bone marrow or bone necrosis at 60 degrees C, only bone marrow necrosis at 70 degrees C and 75 degrees C, and in addition to bone marrow necrosis, bone necrosis at 80 degrees C. At these temperatures no evidence for soft tissue necrosis were observed. CONCLUSIONS Our results show that, in order to achieve bone necrosis at 1-mm and 2-mm distances from the cavity wall, the optimum temperature for hot saline irrigations applied to the bone cavity is 80 degrees C.