Abstract
BACKGROUND: Avascular necrosis (AVN) of the femoral head is a progressive condition that leads to collapse of the femoral head in 85% of symptomatic patients when left untreated. As it is typically a disease that occurs among the younger population, the consequent arthroplasty of the hip is a radical procedure. In this study, we investigated the effect of intravenous zoledronate infusion in patients with avascular necrosis of the femoral head. METHODS: This retrospective study included 94 hips diagnosed with AVN of the femoral head that were treated off-label with 4 mg intravenous zoledronate once or twice in 3-month intervals during the years 2007-2019 at Oulu University Hospital. RESULTS: We found that 38% of the zoledronate-treated hips did not require arthroplasty; 75% of patients not requiring arthroplasty were men. Risk factors for arthroplasty were high Association Research Circulation Osseous (ARCO) stage, large volume of osteonecrosis and edema at baseline, 3, and 6 months of follow-up. High resorption activity indicated by higher levels of cross-linked carboxy- terminal telopeptide of type I collagen (ICTP) after zoledronate infusion in hips classified as ARCO IV predicted a poor outcome (p=0.002). The mean follow-up for those not requiring arthroplasty was 102.4 months. CONCLUSION: Zoledronate treatment is more likely to be effective in male patients with early-stage osteonecrosis (ARCO I-II), whereas advanced-stage disease (ARCO III-IV) may not respond well. Moreover, an accelerated bone resorption rate, indicated by elevated ICTP levels after zoledronate infusion, is associated with an increased risk of treatment failure.