Central Sensitization Elevates the Minimal Clinically Important Difference of Brief Pain Inventory Scores After Total Knee Arthroplasty.

Abstract

Central sensitization (CS) is a recognized risk factor for increased pain and reduced satisfaction after total knee arthroplasty (TKA). However, its effect on the minimal clinically important difference (MCID) of patient-reported outcome measures has not been established. This study aimed to assess the influence of CS status on the MCID of the Brief Pain Inventory (BPI) in TKA patients. We prospectively enrolled 296 unilateral TKA patients who completed one-year follow-up. Preoperatively, CS status was determined by the Central Sensitization Inventory. Pain severity and interference were measured with the BPI before surgery and at one year postoperatively. The MCIDs for BPI were calculated separately for each group using anchor-based and distribution-based approaches. Receiver operating characteristic (ROC) curve analysis was employed to derive MCID cut-off values for the BPI total score and each subscale. By the anchor-based method, MCIDs for total BPI score were 15.3 points (95% CI [confidence interval] 10.65 to 20.03) in the CS group and 9.8 (95% CI 5.82 to 13.94) points in the non-CS (NCS) group. The ROC analysis yielded optimal cut-offs of 14.5 points (AUC = 0.88) for CS patients and 10.6 points (AUC = 0.88) for NCS patients. The CS patients had significantly lower MCID achievement rates than NCS patients (P < 0.05). Preoperative CS elevates BPI MCID thresholds and decreases the likelihood of achieving clinically meaningful pain relief after TKA. These findings help explain persistently lower satisfaction in CS patients and support applying CS-specific MCID standards when evaluating postoperative outcomes.