Rate of perioperative complications in thermal ablation of bone: an animal trial.

INTRODUCTION: While only few data are available yet for radioablation of bone tissue, the occurrence of bone marrow embolisms during cryoablation has been documented. It was the aim of this study to assess perioperative complication rates of thermoablation in animals using state-of-the-art ablation probes. MATERIALS AND METHODS: Eight adult sheep were placed under general anaesthesia, and using a radioprobe, thermoablation was performed on the medial side of the head of the right tibia. In addition, freezing was performed with miniature cryoprobes on both femurs and the head of the left tibia. Haemodynamic monitoring and determination of blood gases and electrolytes were done intraoperatively. The animals were killed 1 week after surgery, and the ablation sites and lung tissue examined macroscopically and microscopically. RESULTS: None of the animals showed pathological changes in any of these parameters. Blood gases remained unremarkable throughout the operation. All eight animals showed an average drop in haemoglobin of 0.97 g/100 ml. Two animals showed fresh embolisms in the pulmonary vessels. CONCLUSION: Experimental thermoablation of bone tissue in large animals failed to show any significant perioperative complications following surgery. The lung embolisms which did occur were not clinically relevant. The use of mini-cryoprobes or radioprobes as alternative or complementary measures for treating pathologically altered bone tissue seems viable and does not involve any undue risks.

Cryosurgery in long bones with new miniature cryoprobe: an experimental in vivo study of the cryosurgical temperature field in sheep.

AIM: The aim of this in vivo study was to determine whether new miniature cryoprobes provide adequate tissue cooling in long bones by measuring the field of temperature under various conditions. METHODS: Freezings were performed in femoral and tibial bones of 10 sheep under general anaesthesia. Applying one cryoprobe, temperatures of -75 degrees C resp. -51 degrees C could be reached within 0.75 cm resp. 1.00 cm of the probe. RESULTS: Histological examinations revealed compact bone and marrow necroses along the isotherm in all 10 sheep. Using two cryoprobes simultaneously, a mean temperature decrease to -71 degrees C between the two cryoprobes was achieved thanks to the synergistic freezing effect. Looking at consecutive freezes, it was apparent that with similar cryoprobe end temperatures, the temperature dropped faster if the number of freezing cycles was increased. CONCLUSION: In conclusion, it was seen that despite its small diameter, the new miniature cryoprobe delivers adequate in vivo tissue cooling in long tubular bones. Employing the synergistic freezing effect by using two or more cryoprobes simultaneously, efficient in vivo freezing of larger bone segments is also possible. Thus, cryosurgery with the new miniature probes can provide a valuable complement to conventional resection of long tubular bones, and offers a viable alternative to surgical treatment of neoplastic diseases of the skeletal system.