Migration of cementless total knee arthroplasty is mitigated by both local intraoperative zoledronate and postoperative denosumab: a randomized controlled trial

Aims: The aim of this study was to investigate if adjuvant treatment with antiresorptive bone medication improves fixation of cementless total knee arthroplasty. We hypothesized that local bisphosphonate (zoledronate) or systemic denosumab would both decrease implant migration. Methods: This four-way, double-blinded, randomized trial included 108 patients with primary knee osteoarthritis with a five-year follow-up. Three groups had the same cementless total knee tibial implant and were included in this primary study (n = 82). Patients were randomized to either placebo (n = 27), intraoperative local zoledronate (n = 28), or postoperative denosumab (n = 27). The primary outcome was tibial implant migration measured by radiostereometric analysis (RSA) using maximum total point motion (MTPM) and signed migrations. Secondary outcomes were biochemical bone markers (resorption: serum collagen type 1 cross-linked C-telopeptide (CTX); formation: serum type 1 procollagen N-terminal (P1NP)), periprosthetic bone mineral density (BMD), and patient-reported outcomes. Results: At one year, the mean difference in MTPM between zoledronate and placebo was 0.43 mm (95% CI 0.01 to 0.85; p = 0.043), and 0.42 mm (95% CI 0.00 to 0.83; p = 0.048) between denosumab and placebo. At five years, the intervention groups showed less y-translation (subsidence) than placebo: mean difference of 0.50 mm for zoledronate (95% CI 0.23 to 0.78; p < 0.001) and 0.30 mm for denosumab (95% CI 0.03 to 0.58; p = 0.031). CTX was lower in the zoledronate group than in the placebo group at two- and six-week follow-up. In the denosumab group, CTX was lower until one year postoperatively. P1NP were similar in the placebo and zoledronate groups, but lower in the denosumab group up to one year postoperatively. Periprosthetic BMD was higher in intervention groups, with a lasting effect in the zoledronate group at five years. Conclusion: Both interventions decreased cementless tibial implant migration by suppressing bone resorption. Local zoledronate had a lasting mitigating effect on subsidence and the periprosthetic BMD. Our findings support the use of local intraoperative zoledronate during knee arthroplasty surgery to improve cementless tibial implant fixation and preserve tibial bone. However, multicentre studies and prospective cohort quality studies should be performed for confirmation.