Dual-mobIlity verSus conventional Total hip arthroplasty In femoral Neck fractures, a registry-nested, open-label, Cluster-randomized crossover Trial (DISTINCT) : statistical analysis plan.

Aims: A statistical analysis plan for analysis of DISTINCT (Dual-mobIlity verSus conventional Total hip arthroplasty In femoral Neck fractures, a registry-nested, open-label, Cluster-randomized crossover Trial) is outlined to aid transparency in analytical procedures.

Methods: DISTINCT aims to determine whether dual-mobility total hip arthroplasty (THA) is superior to conventional THA in reducing postoperative prosthetic hip dislocations in patients undergoing surgery for femoral neck fractures. The trial is nested within the Australian Orthopaedic Association National Joint Replacement Registry (AOANJRR). The clusters comprised hospitals that perform at least 12 THAs for femoral neck fracture per annum. Each hospital was randomized to two sequential periods of dual-mobility THA and conventional THA, with the order randomly allocated. Crossover occurred once sites had recruited an average of 16 patients eligible for the primary analysis in the initial allocation, to provide an average of 32 patients per cluster. The primary outcome is the incidence of prosthetic hip dislocation in the first postoperative year. Secondary outcomes are the rate of revision for dislocation, all-cause revision, mortality at one, two, and five years, and complication rates at one year. All analyses will use cluster summary methods, weighted by cluster size to account for unequal cluster sizes. Participants will be analyzed in the groups to which they were randomized (intention-to-treat). Sensitivity analyses will be performed to analyze the unadjusted primary outcome based on treatment received (as-treated) and per-protocol groupings.

Conclusion: This statistical analysis plan describes the detailed analysis of the DISTINCT study, a registry-nested, open-label, cluster-randomized crossover trial that will provide supporting evidence for prosthesis choice in the common clinical problem of femoral neck fracture.