Cryosurgery in long bones; an experimental study of necrosis and revitalization in rabbits

Cryosurgery is an established adjuvant treatment of bone tumors which reduc es the local recurrence rate. In this study, cryosurgical experiments were carried out in rabbits to study the temperature field, the extent of necros is, and the revitalization process in order to optimize treatment. Intramed ullary freezing of long bones with a closed liquid nitrogen cryoprobe and t hree consecutive sessions induces osteonecrosis down to the -10 degrees C i sotherm without compromising the soft tissues. The application of a tourniq uet does not influence the thermodynamics. The revitalization process is di stinguished into an osteogenic and a remodelling phase. In rabbits, there i s an obvious periosteal osteogenesis starting from 1 week after operation a nd overlapping the remodelling phase, which stal ts between 3 and 5 weeks a fter operation. Two out of eight rabbits sustained a pathologic fracture wi thin 3 weeks of cryosurgery. No pathologic fractures were encountered durin g the remodelling phase, probably because of the profuse periosteal bone ap position that added mechanical strength. In clinical practice, no profound periosteal bone apposition and a high risk for pathologic fractures during the remodelling phase were noted. Future research should focus on bone stre ngth during the remodelling phase of cryosurgically treated long bones, to decide on the role of preventive osteosynthesis or postoperative restrictio ns. This animal model is not advised for these biomechanical experiments be cause of itss profuse periosteal bone apposition.