Outcomes Vary Significantly Using a Tiered Approach To Define Success After Total Hip Arthroplasty.

Background: Clinical outcomes following primary total hip arthroplasty (THA) are commonly assessed through patient-reported outcome measures (PROM). The purpose of this study was to use progressively more stringent definitions of success to evaluate clinical outcomes of primary THA at 1-year postoperatively and to determine if demographic variables were associated with achievement of clinical success. Methods: The American Joint Replacement Registry (AJRR) was queried from 2012-2020 for primary THA. Patients that completed the following PROMs preoperatively and 1-year postoperatively were included: Western Ontario and McMaster Universities Arthritis Index (WOMAC), Hip Injury and Osteoarthritis Outcome Score (HOOS) and HOOS for Joint Replacement (HOOS, JR). Mean PROM scores were determined for each visit and between-visit changes were evaluated using paired t-tests. Rates of achievement of minimal clinically important difference (MCID) by distribution-based and anchor-based criteria, patient acceptable symptom state (PASS), and substantial clinical benefit (SCB) were calculated. Logistic regression was used to evaluate associations between demographic variables and odds of success. Results: 7,001 THAs were included. Mean improvement in PROM scores were: HOOS, JR, 37; WOMAC-Pain, 39; WOMAC-Function, 41 (p<0.0001 for all). Rates of achievement of each metric were: distribution-based MCID, 88-93%; anchor-based MCID, 68-90%; PASS, 47-84%; SCB, 68-84%. Age and sex were the most influential demographic factors on achievement of clinical success. Conclusion: There is significant variability in clinical outcomes at 1 year after primary THA when using a tiered approach to define success from the patient's perspective. Tiered approaches to interpretation of PROMs should be considered for future research and clinical assessment.