Hip fractures remain an important complication following kidney transplantation, but the incidence of these fractures has decreased substantially since 1997, according to a new study.

The study, led by Wolfgang C. Winkelmayer, MD, ScD, Associate Professor of Medicine and Director of Clinical Research in the Division of Nephrology at Stanford University of School of Medicine in Palo Alto, Calif., included 69,740 patients who under kidney transplantation from 1997 to 2010.

Results showed patients who received a transplant in 2010 had a 44% decreased risk of hip fracture compared with those who received a transplant in 1997, after adjusting for case mix and demographic, dialysis, comorbid, and most transplant-related factors, researchers reported online ahead of print in the American Journal of Transplantation.

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The risk reduction was 32% after additional adjustment for baseline immunosuppression.

Of the 69,740 patients, 597 experienced a hip fracture during 155,341 person-years of follow-up, which translated into an incidence rate of 3.8 per 1,000 person-years. The 30-day mortality rate was 2.2 deaths per 100 hip fractures.

Dr. Winkelmayer’s group noted that bone loss and fractures are well-known complications of solid organ transplantation, and cited research demonstrating that bone of about 3.9% in the femoral neck has been shown to occur as early as three months post-transplant.

The researchers suggested some possible explanations for the decline in hip fracture risk, including changes in immunosuppressive regimens during the era studied. The attenuation of hip fracture risk after adjusting for baseline immunosuppression suggests that changes in immunosuppressive therapy may be partly responsible for the risk reduction, they stated.

“Tacrolimus largely replaced cyclosporine by the early 2000s and some data suggest that, relative to cyclosporine, tacrolimus may preserve bone mineral density.” In addition, corticosteroids are a well-established risk factor for post-transplant fractures, “and the adoption of steroid-sparing and steroid-minimizing regimens could have contributed to the diminished adjusted risk.”

The researchers acknowledged some study limitations, such as possible under-ascertainment of hip fractures by including only hospitalized patients, since they based their outcome definition on administrative claims data. They noted, however, that nearly all patients with hip fractures require hospitalization.