Risk Factors for Fractures in Kidney Transplantation

Background: Risk factors for fracture after kidney transplantation need to be identified to target patients most likely to benefit from preventive measures.

Methods: Medical records were reviewed for 1572 kidney transplants done at a single center between February, l963 and May, 2000 with 6.5+/-5.4 years of follow-up.

Results: One or more fractures occurred in 300 (19.1%), with multiple fractures in 101 (6.4%). After excluding fractures of the foot or ankle (n=130 transplants, 8.3%), avascular necrosis (n=86, 5.5%), and vertebral fractures (n=28, 1.8%), there were one or more fractures in 196 (12.5%), with a cumulative incidence of 12.0%, 18.5%, and 23.0% at 5, 10, and 15 years, respectively. In multivariate Cox proportional hazards analysis, age had no effect on fractures in men. Compared with men and younger women, women 46-60 and >60 years old were, respectively, 2.11 (95% confidence interval 1.43-3.12, P=0.0002) and 3.47 (2.16-5.60, P<0.0001) times more likely to have fractures. Kidney failure from type 1 and 2 diabetes increased the risk by 2.08 (1.47-2.95, P<0.0001) and 1.92 (1.15-3.20, P=0.0131), respectively. A history of fracture pretransplant increased the risk by 2.15 (1.49-3.09, P<0.0001). Each year of pretransplant kidney failure increased the risk by 1.09 (1.05-1.14, P<0.0001). Obesity (body mass index >30 kg/m2) was associated with 55% (17-76%, P=0.0110) less risk. Different immunosuppressive medications, acute rejections, and multiple other factors were not independently associated with fractures.

Conclusions: The population of transplant patients at high risk for fracture can be identified using age/gender, pretransplant fracture history, diabetes, obesity, and years of pretransplant kidney failure.