Effects of liquid nitrogen treatment on the proliferation of osteosarcoma and the biomechanical properties of normal bone.

To overcome problems of autografts for reconstruction in the presence of malignant bone and soft tissue tumors, we devised a method for treating autografts that utilizes the hypothermic effect of liquid nitrogen. We measured temperature changes inside the bone at each condition and established a one-cycle liquid nitrogen protocol that included 20 min in liquid nitrogen, 15 min in room air, and 15 min in physiological saline. The proliferation potential of the tumor cells treated with the liquid nitrogen method was examined by means of bromodeoxyuridine (BrdU) immunostaining. Tumor proliferation potential in vivo was examined in nude mice. Based on the results we concluded that the tumor cells died out as a result of the liquid nitrogen method. Regarding compression strength there was no significant difference between intact bone and liquid nitrogen-treated bone, whereas the strength of the autoclaved bone was decreased. Scanning electron microscopic examination of the fracture surface of the autoclaved bone after the compression test showed an irregular, uneven surface, whereas that of the liquid nitrogen-treated bone was smooth and fine-grained. This might be one of the reasons for the discrepancy in compression strength.