Low pretransplant bone-mineral density and rapid bone loss do not increase risk for avascular osteonecrosis after allogeneic hematopoietic stem cell transplantation

Background. Avascular osteonecrosis (AVN) is a serious complication of allogeneic stem cell transplantation (SCT). Graft-versus-host disease and its treatment with steroids are the main risk factors; underlying diagnosis, age and gender are further risk factors. It has been speculated that low baseline bone mineral density (BMD) is associated with AVN posttransplant. Furthermore, rapid bone loss with consecutive microarchitectural changes might prone patients to AVN. Methods. In a single-center prospective cohort study, 255 patients undergoing allogeneic SCT for CML, AML, MDS, and ALL were followed for at least 5 years. We measured BMD (spine, femoral neck, total body) and body indices (body weight, body mass index, body composition determined by dual-energy x-ray absorptiometry) at baseline. Annual changes of BMD and body indices were prospectively observed for 5 years. Incidence of hip AVN necessitating total arthroplasty (severe adverse event) was determined. Univariate and multifactorial nominal logistic as well as Cox proportional hazard analysis were performed. Results. Severe adverse events occurred in nine patients (5-year cumulative incidence rate 6.9%). Baseline BMD and body indices were within normal limits. Rapid and intense bone loss occured, especially during the first year, accompanied by loss of body and especially muscle mass. AVN occurrence was not associated with BMD or body indices at baseline neither with prospectively observed changes of BMD or body indices. Conclusions. AVN is a devastating frequent complication of allogeneous SCT. Allogeneous SCT is followed by dramatic changes in BMD and body composition. However, low BMD and rapid bone loss per se do not dispose patients to AVN occurrence.