Avascular bone necrosis in the renal transplant patient: a discriminant analysis of 144 cases.

The purpose of this study was to seek ways of reducing the risk of avascular necrosis by examining certain potentially predisposing factors in the renal transplant patient. A group of 19 recipients who had avascular necrosis were compared with 125 recipients wo did not have this complication as reflected in the clinical factors, immunosuppressive therapy, and various biochemical parameters during the first year after the transplant operation. The serum phosphorus level two months postoperation was significantly lower in the group with avascular necrosis (p less than 0.01). Discriminant analysis showed that recipients who had hypophosphatemia at this time, who were older and who displayed slower normalization of the renal function were more likely to develop avascular necrosis. There were no differences in the individual steroid dose, but it is reasonable to assume that a general dose reduction would reduce the risk of avascular necrosis. A low serum phosphorus level during the interval after transplantation, when secondary hyperparathyroidism is still present, may be a predisposing factor. Attempts to avoid hypophosphatemia are recommended, either by replacing phosphate-depleting antacids by agents with a smaller phosphate binding capacity, or by supplementing the supply of phosphate.