Preoperative pain and achievement of the minimal clinically important difference for physical function one year after total hip arthroplasty: a prospective cohort study

Purpose To examine the association between preoperative social, clinical, and biological variables and the achievement of the minimal clinically important difference (MCID) on the WOMAC-function subscale one year post total hip arthroplasty (THA). Methods In this prospective cohort study, 85 patients (aged ≥ 65) completed baseline preoperative assessment, and 53 completed the 12-month follow-up (32 lost to follow-up; 66.0% achieved MCID). The outcome was achieving WOMAC-function MCID (≥ 26.54 points). Multivariable logistic regression adjusted for baseline pain, age, sex, and BMI were performed. ROC curves evaluated discriminative capacity. Results An exploratory ROC analysis identified a baseline pain threshold of 6.5 on the Numerical Rating Scale yielded an AUC of 0.740 (70% sensitivity, 77% specificity). Conclusions Preoperative pain intensity independently associated with clinically meaningful functional improvement post-THA. An exploratory pain threshold of 6.5 on the NRS may provide an exploratory benchmark for future risk stratification.