Failure to Achieve an Early Distribution-Based Minimum Clinically Important Difference Almost Triples the Odds of Poor Patient-Reported Outcomes Within the First Year Following total Hip Arthroplasty: A Retrospective Cohort Study.

BACKGROUND: Postoperative improvement in patient-reported outcomes is a key measure of total hip arthroplasty success. The Minimum Clinically Important Difference (MCID) represents the smallest improvement perceived as beneficial. Distribution-based MCIDs have been criticized for producing thresholds smaller than anchor-based values, questioning their clinical relevance. We hypothesized they may capture early biological recovery signals associated with subsequent patient-reported outcomes and aimed to determine whether failure to achieve an early distribution-based MCID (seven to 31 days) was associated with failure to achieve a late anchor-based MCID (90 to 365 days).

METHODS: This retrospective cohort study included patients undergoing primary unilateral total hip arthroplasty for osteoarthritis from January 1, 2021, to January 1, 2025, comprising 844 patients. Patients were included if they completed 'Hip disability and Osteoarthritis Outcome Score, Joint Replacement' questionnaires preoperatively, at seven to 31 days, and at 90 to 365 days. Distribution-based MCID was defined as a ≥ 7.8-point improvement, and anchor-based MCID as ≥ 23 points. Multivariable regression assessed associations between early distribution-based and late anchor-based MCID failure, adjusting for demographics and clinical factors.

RESULTS: In the early period (seven to 31 days), 565 patients (67.0%) achieved the distribution-based MCID, whereas 573 (67.9%) achieved the late anchor-based MCID (90 to 365 days). Among patients who failed to attain an early distribution-based MCID, 54.1% (151 of 279) also failed the late anchor-based MCID, compared with 21.2% (120 of 565) among early achievers (P < 0.001). Early distribution-based MCID failure was a strong independent predictor of late anchor-based MCID failure (odds ratio: 2.61; 95% confidence interval: 1.85 to 3.68; P < 0.001). Higher baseline Hip disability and Osteoarthritis Outcome Score, Joint Replacement scores and facility-based discharge were also independently associated with late failure (P < 0.05).

CONCLUSIONS: Failure to achieve an early distribution-based MCID is strongly associated with poor patient-reported outcomes up to one year. Early distribution-based MCID attainment may represent an important prognostic marker, enabling timely clinical intervention.