[Changes in stability after cryosurgical treatment of long tubular bones. An animal experiment study].

The incidence of spontaneous fractures after cryosurgical treatment is described in the literature. The purpose of this study in the sheep model was to analyze the possibility of minimizing the potential risk of bone failure using a new miniature cryoprobe with minimal tissue traumatism and exact control of the ablation. In each of 24 sheep ablations at the right femur and left tibia were performed by drilling. The ablation at the femur was restricted to an area of 2 cm(2) of only one cortical bone, whereas at the proximal tibia the whole tibial plateau was included. The opposite side, which was treated with analog drillings without cryoablation, served as control. The ultimate bending strength of the femur and the ultimate compression strength of the tibia were examined 2, 4, and 6 months after the operation. After 2 months there was a significant difference ( p<0.05) in the ultimate compression strength between the treated and untreated tibiae, whereas the ultimate bending strength of the treated femora tended to be lower. After 4 and 6 months the side treated with cryosurgery was only marginally weaker than the untreated side. Spontaneous fractures were not observed during the whole experimental period. The good controllability of the freezing procedure and the low iatrogenic weakening of the bone using a modern miniature cryoprobe minimizes the risk of pathological postoperative fractures. After ablation of larger bone sections, the treated extremity should be partially unloaded or managed by osteosynthesis for at least 3 months.