Acetabular Revision With Dual-Mobility Bearing Reduces Redislocation in Unstable Total Hip Arthroplasty

Background: The redislocation rate for revision total hip arthroplasty (R-THA) done for instability ranges from 21 to 39%. Large femoral heads, constrained liners (CL), or dual-mobility (DM) implants are used to address this issue. This study assessed cumulative redislocation and re-revision rates after R-THA was performed for instability and identified associated risk factors for failure. Methods: There were 472 hips (468 patients) undergoing first-time R-THA due to instability between 2006 and 2021. The DM bearings were used after 2010. The mean age of patients at the time of surgery was 67 years (range, 15 to 94), with a mean body mass index of 29.4 (range, 17.3 to 55.9); 61.2% were women, and 9.5% were current smokers. Data on patient characteristics, surgical factors, and surgical management strategies were collected. Time to redislocation, rerevision, or the latest follow-up served as survival endpoints. Cumulative risks and hazard ratios (HR) were calculated. Results: At five years, cumulative redislocation and all-cause rerevision risks were 20 and 22%, respectively, increasing to 24 and 38% at 10 years. Risk factors for redislocation and rerevision included nonosteoarthritis index THA (HR 2.45, P < 0.0001; HR 2.36, P < 0.0001), smoking history (HR 2.93, P = 0.0001; HR 2.37, P = 0.0013), and cup retention (HR 1.84, P = 0.0156; HR 1.99, P = 0.0035), respectively. The best-performing strategy to prevent redislocation was cup revision with a DM implant (5-year redislocation incidence of 7%). Comparatively, the risk of redislocation was higher for cup revision CL (HR 1.64, P = 0.57), cup retention CL(HR 2.96, P = 0.049), cup revision with ≥ 36 mm head (HR 3.12, P = 0.049), cup retention DM (HR 3.81, P = 0.033), cup revision with < 36 mm head (HR 4.1, P = 0.066), cup retention with ≥ 36 mm head (HR 4.27, P = 0.0078), and cup retention with < 36 mm head (HR 6.93, P = 0.0008). Conclusions: A R-THA for instability presents ongoing challenges with high reoperation and rerevision rates. Patient optimization (e.g., smoking cessation), acetabular component revision when appropriate, and implantation of DM or CL should be considered.