Denosumab and bone loss in uncemented total hip arthroplasty: a secondary 5-year follow-up of a randomized controlled trial

BACKGROUND AND PURPOSE: Denosumab may preserve periprosthetic bone mineral density (pBMD) around uncemented total hip arthroplasty (THA) components. This exploratory analysis of a previously published randomized controlled trial (RCT) aimed to assess the effects of denosumab on BMD 5 years after treatment cessation. METHODS: 64 non-osteoporotic patients undergoing uncemented THA were enrolled in a randomized, double-blind, placebo-controlled phase-2 trial and received either 2 doses of denosumab or placebo. The primary outcome was pBMD at 12 months, measured by dual-energy X-ray absorptiometry (DEXA). At a mean follow-up of 5.6 years (range 4.3-7.3), 54 patients remained for clinical assessment, DEXA, and plain radiography. The study was registered on ClinicalTrials.gov (NCT01630941). RESULTS: No differences in pBMD in the acetabular Digas zones or femoral Gruen zones were found between the groups at 5 years. The estimated mean difference in the sum of all zones around the cup was 0.042 g/cm² (95% confidence interval [CI] -0.31 to 0.35; P = 0.8), and for the sum of all Gruen zones -0.06 g/cm² (CI -0.55 to 0.43; P = 0.8). No statistically significant differences were observed in patient-reported outcome measures or the incidence of heterotopic ossification. A gradual decline in pBMD was evident. CONCLUSION: At 5 years, the adjusted between-group difference and its 95% confidence interval showed no statistically or clinically relevant effect of denosumab. Whether longer treatment duration or a sequential post-denosumab regimen could influence long-term periprosthetic bone preservation is unknown.