Patient-reported outcome measure comparison of two cemented primary total hip arthroplasty implant combinations for osteoarthritis: a regional New Zealand study.

PURPOSE: Compare patient-reported outcome measures (PROMs) of two cemented implants in primary total hip arthroplasty (THA) for osteoarthritis in a New Zealand regional joint registry. Identify patient predictors of poorer PROMs. METHODS: We analysed observational data from primary THA surgeries for osteoarthritis performed between 1 January 2003 and 30 June 2023, with at least one recorded PROM (n = 1365) from a regional joint registry. We compared preoperative, 1-year, 5-year, and 10-year PROMs in the cemented, highly crosslinked polyethylene Exeter® X3 Rimfit cup (Rimfit) and its conventional polyethylene predecessor, the Exeter® Contemporary Flanged cup (ECF) with the same cemented Exeter® V40 stem. We investigated six patient factors and their influence on physical function, and mental and physical health PROMs. RESULTS: No significant difference in physical function PROMs were noted between implants at any timepoint. Both implant combinations exhibited excellent (> 41) mean postoperative Oxford hip scores based on published thresholds (Rimfit: mean 41.30 ± SD 8.46; ECF: mean 41.64 ± SD 8.67). Mental health was significantly better preoperatively and at 1-year and 5-year with the Rimfit based on Veterans RAND 12-Item Health Survey. Public funding was a significant and clinically meaningful predictor of poorer preoperative outcomes in all PROMs and in both cohorts, followed by comorbidity status. The strongest significant predictor of poorer postoperative PROMs was poorer preoperative PROMs, followed by Māori ethnicity. CONCLUSION: Both implant combinations demonstrated similar PROMs up to 10 years, but the Rimfit exhibited superior mental health. Public funding, comorbidity status, and Māori ethnicity were predictors of statistically significant and clinically meaningful poorer preoperative and postoperative PROMs.