Subgroup Variations in Bone Mineral Density Response to Zoledronic Acid After Hip Fracture

Minimizing post‐fracture bone loss is an important aspect of recovery from hip fracture, and determination of factors that affect bone mineral density (BMD) response to treatment after hip fracturemay assist in the development of targeted therapeutic interventions. A post hoc analysis of the HORIZON Recurrent Fracture Trial was done to determine the effect of zoledronic acid (ZOL) on total hip (TH) and femoral neck (FN) BMD in subgroups with low‐trauma hip fracture. A total of 2127 patients were randomized (1:1) to yearly infusions of ZOL 5mg (n 1065) or placebo (n 1062) within 90 days of operation for low‐trauma hip fracture. The 1486 patients with a baseline and at least one post‐baseline BMD assessment at TH or FN (ZOL 745, placebo 741) were included in the analyses. Percentage change from baseline in TH and FN BMD was assessed at months 12 and 24 and compared across subgroups of hip fracture patients. Percentage change from baseline in TH and FN BMD at months 12 and 24 was greater (p< 0.05) in ZOL‐treated patients compared with placebo in most subgroups. Treatment‐by‐subgroup interactions (p< 0.05) indicated that a greater effect on BMDwas observed for TH BMD at month 12 in females, in patients in the lower tertile bodymass index at baseline (22.6 kg/m2), and in patients with baseline FN BMD T‐score of –2.5; for FN BMD in patients who received ZOL for>6 weeks post‐surgery; and for TH and FN BMD in patients with a history of one ormore prior fractures. All interactions were limited to the first 12months after treatmen