Defining clinically meaningful values in the oxford hip score and factors associated with their achievement following aseptic revision total hip arthroplasty

PURPOSE: To define the 'patient acceptable symptom state' (PASS) and 'minimum important change' (MIC) for the Oxford Hip Score (OHS) following aseptic revision total hip arthroplasty (rTHA), and identify factors associated with their achievement. METHODS: A prospective cohort of 135 patients (138 hips) undergoing aseptic rTHA at a single centre were followed up at one and two years postoperatively. Demographics, health-related quality of life (HRQoL; EQ-5D) and OHS were recorded at each timepoint. Anchor techniques were used to define the MIC and PASS. Regression models identified factors associated with PASS and MIC achievement. RESULTS: The OHS PASS was 31.5 and 33.5 at one and two years postoperatively, respectively. The MIC was 8.5 at both timepoints. A greater preoperative EQ-5D was independently associated with PASS achievement at both timepoints. One-year MIC achievement was independently associated with lower BMI (p = 0.042) and lower preoperative OHS (p = 0.007), whilst lower preoperative OHS (p = 0.016) alone was independently associated with two year MIC achievement (p = 0.016). Lower preoperative EQ-5D and ASA grade 3 were associated with failure to achieve either PASS or MIC at one year (p = 0.030) and two years (p = 0.013) postoperatively, respectively. CONCLUSION: The PASS and MIC thresholds for the OHS following aseptic rTHA contextualise the score and can inform study design. Greater preoperative HRQoL was independently associated with PASS achievement, whilst worse preoperative function was independently associated with MIC achievement. These thresholds should be considered in conjunction when assessing outcomes following aseptic rTHA.