First Revision Total Hip Arthroplasty for Instability: 10-Year Outcomes and Risk Factors Associated with Re-Revision

BACKGROUND: Recurrent instability remains a leading cause of failure after revision total hip arthroplasty (rTHA). This study assessed the 10-year survivorship of the first rTHA when undertaken for instability and identified factors associated with failure. METHODS: We retrospectively identified all consecutive rTHA performed for instability at our institution between 2000 and 2022. Of the 678 rTHA identified, 284 (41.9%) were the first rTHA and included in the study. Re-revisions and oncology cases were excluded. The mean age at revision was 65 years, and 63.2% were women. The mean follow-up was 11.4 years (range, two to 22). A total of 84 (29.6%) hips underwent at least one re-revision. Survival free from instability-related and all-cause re-revision at 10 years was calculated using Kaplan-Meier analysis. Multivariable Cox proportional hazard regression modeling was used to assess factors associated with 10-year survival. RESULTS: The 10-year survivorship was 82.2% for instability and 73.6% for all-cause re-revision. Dual mobility (DM) components had higher 10-year instability-free survival than both standard bearings and constrained liners (P = 0.04). However, when considering 'large' (≥ 36 mm) femoral heads, there was no difference in the revision rate when compared to DM components (P = 0.59). Constrained liners were associated with a higher risk of revision for instability (HR [hazard ratio] 2.7, 95% CI [confidence interval] 1.05 to 6.8, P = 0.01). Younger age at surgery (P = 0.002), elevated body mass index (BMI) (P = 0.01), abductor deficiency (P = 0.03), and using a constrained liner (P = 0.04) were significantly associated with all-cause re-revision. CONCLUSIONS: In patients undergoing first-time rTHA for instability, nearly 20% will have recurrent instability, and 30% will undergo further revision within 10 years. The DM and large femoral heads demonstrate 10-year survivorship. Several patient and implant-related factors are associated with instability-specific and all-cause re-revision.