Prevalence and risk factors for nonvertebral bone fractures in kidney transplant recipients - a single-center retrospective analysis

Complex and longstanding bone disease superimposed by harmful influences of immunosuppression is the reason for increased risk of bone fracture in kidney transplant recipients. The aim of our study was to analyze the incidence and prevalence of nonvertebral bone fractures and early (in the first post-transplant year) clinical and laboratory risk factors for suffering bone fracture in the long-term post-transplant period. Clinical and laboratory data as well as bone mineral density (BMD) measurements of 507 first kidney transplant recipients who were transplanted in the period from 1976 to 2011 were analyzed. The mean age of included patients was 54.3 ± 12.0 years, there were 45% females, and mean time on renal replacement treatment prior to transplantation was 63.4 ± 43.6 months. The average observation time post-transplant was 9.7 years (1.4 - 36.3 years). Post-transplant, 64 (12.6%) patients suffered 89 nonvertebral fractures (44 patients suffered 1 fracture, 15 patients 2 fractures, and 5 patients 3 fractures). Patients with fractures had significantly lower late BMD of femoral neck in the period of 1 - 10 years post-transplant, had osteopenia and osteoporosis more frequently in the same time period, and higher serum alkaline phosphatase in the first year post-transplant. 13 patients (13/64, 20.3%) had major fractures. Patients with major fractures were significantly older than patients with no major fractures and had lower serum albumin. Frequency of treatment with bisphosphonate, calcium, or phosphate did not differ between the groups. Vitamin D supplement (active form in 98% of cases) was prescribed more frequently in the group without fractures, but this was not statistically significant. Fracture rate in our transplant patient population was comparable to that reported in the literature. Except for a higher level of serum total alkaline phosphatase in the fracture group, we found no other early laboratory risk factors for bone fractures. BMD at the femoral region 1 - 10 years after kidney transplantation but not BMD at the time of transplantation was a risk factor for nonvertebral fractures. Osteopenia and osteoporosis in the post-transplant period were found to be a fracture risk factor. .