Statistical Analysis Plan for the REDEP study: Effectiveness of dual-mobility cups for preventing dislocation after primary total hip arthroplasty by a posterolateral approach compared to unipolar cups in elderly patients

Periprosthetic hip dislocation is a frequent complication after primary total hip arthroplasty. Observational studies suggest that dual mobility cups may reduce dislocation risk to approximately 1%, but definitive randomized evidence supporting their routine use in primary total hip arthroplasty is absent. The REDEP trial is the first prospective, randomized controlled trial that compares dual mobility cups with unipolar cups in patients ≥70 years who electively undergo primary total hip arthroplasty via a posterolateral approach. The primary objective of the trial is to determine the difference in the number of patients who suffer a periprosthetic dislocation of the hip within 1 year after primary total hip arthroplasty in this population. Other outcomes include the difference in the total number of hip dislocations (including recurrent dislocations within patients), differences in patient-reported outcome measures, and differences in the incidence of (serious) adverse events. This statistical analysis plan describes the primary statistical analysis for the REDEP study. The analyses described herein were defined prior to database lock and unblinding. Secondary analyses will be described in subsequent versions of this statistical analysis plan.