The Effect of a Single Infusion of Zoledronic Acid on Early Implant Migration in Total Hip Arthroplasty

Background: Aseptic loosening is the most frequent cause of implant failure in total hip arthroplasty. While a direct link between aseptic loosening and periprosthetic bone loss remains elusive, there is plentiful evidence for a close association with early implant migration. The present trial was primarily designed to evaluate whether a single infusion of 4 mg of zoledronic acid prevented early implant migration in patients with osteonecrosis of the femoral head. Methods: Fifty patients were consecutively enrolled to receive either zoledronic acid or saline solution after cementless total hip arthroplasty. Radiographs, biochemical parameters of bone turnover, and the Harris hip-rating score were determined preoperatively and at each follow-up examination at seven weeks, six months, one year, and yearly thereafter. The median follow-up period was 2.8 years. Results: We found a significant subsidence of the stem of up to a mean (and standard deviation) of −1.2 ± 0.6 mm at two years within the control group, and the cups had a mean medialization of 0.6 ± 1.0 mm and a mean cranialization of 0.6 ± 0.8 mm (p < 0.001). Treatment with zoledronic acid effectively minimized the migration of the cups in both the transverse and the vertical direction (mean, 0.15 ± 0.6 mm and 0.06 ± 0.6 mm, respectively; p < 0.05), while only a trend to decreased subsidence of the stem was detected. Finally, the Harris hip score rapidly increased over time in both treatment groups, although this increase was significantly more pronounced in the zoledronate-treated group than in the control group (analysis of variance, p = 0.008). Conclusions: A single infusion of zoledronic acid shows promise in improving initial fixation of a cementless implant, which may improve the clinical outcome of total hip arthroplasty in patients with osteonecrosis of the femoral head. Level of Evidence: Therapeutic Level I. See Instructions to Authors for a complete description of levels of evidence.