Effect of zoledronate on avascular necrosis of the femoral head according to disease stage and bone resorption activity.

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.