RESUMEN
The effects of liquid nitrogen (LN) and polymethylmethacrylate (PMMA) on normal bone, bone graft incorporation, and reossification were evaluated by simulating a tumor in dogs with experimental bone cavity. Ten skeletally mature mongrel dogs (20 femora) were divided into three groups: Group I, controls; Group II, LN (with and without bone graft); and Group III, PMMA (with and without LN). Roentgenograms, whole-mount histology, and tetracycline fluorescence studies were performed on the distal femur. Correlation of these studies showed that (1) marked trabecular and bone necrosis, extending 7-12 mm around the circumference of the cavity, developed by three and seven weeks after LN but no bony necrosis occurred after PMMA; (2) the pattern of reossification following cryosurgery was delayed and abnormal, demonstrating increased calcification and metaplastic bone formation; (3) cryosurgery decreased the rate of bone graft incorporation; (4) the cryonecrotic rim following cryosurgery correlated with an abortive attempt at peripheral reossification; and (5) cryosurgery had no effect on the articular cartilage. Cryosurgery is effective in causing bone necrosis, whereas PMMA is not, and the pattern of reossification is delayed and altered by freezing. This study suggests that microvascular thrombosis with subsequent ischemic infarction of bone is a major cause of bone necrosis following cryosurgery.