Minimal clinically important difference of four commonly used balance assessment tools in individuals after total knee arthroplasty : a prospective cohort study

Abstract

Background: Although balance is commonly assessed during the recovery of total knee arthroplasty (TKA), the minimal clinically important difference (MCID) values of frequently used balance assessment tools have not been established previously in this population. Objective: To determine the MCID of four balance tests—ie, the Balance Evaluation Systems Test (BESTest), Mini-BESTest, Brief-BESTest, and the Berg Balance Scale (BBS)—in individuals post-TKA. Design: Prospective cohort. Setting: Outpatient rehabilitation. Participants: Inclusion criteria: (1) first primary TKA with diagnosed knee osteoarthritis; (2) aged 50-85 years. Exclusion criteria: (1) TKA due to rheumatoid arthritis of the knee or traumatic injury; (2) known medical conditions that influence balance ability. One hundred forty-six participants were recruited, and 134 of them with complete data were included in the analysis. Interventions: Participants received individualized physiotherapy, consisting of electrotherapy for pain and edema control, mobilization and strengthening exercises, and gait and balance training, once or twice per week between assessments. Main Outcome Measurements: Participants were assessed on the BESTest, Mini-BESTest, Brief-BESTest, BBS, and Functional Gait Assessment (FGA) 2 and 4 weeks after surgery. The FGA was used as the anchor reference measure to calculate the MCID of the other four balance tests. A distribution-based approach was also employed to derive the MCID (ie, standardized effect size of 0.5). Results: The BESTest (area under curve [AUC] = 0.811, 95% confidence interval [CI] 0.739-0.883) had the highest accuracy in detecting clinically important improvements on the FGA (≥4 points), followed by the Mini-BESTest (AUC = 0.782, 95% CI 0.704-0.860), Brief-BESTest (AUC = 0.701, 95% CI 0.618-0.795), and BBS (AUC = 0.586, 95% CI 0.490-0.682). The anchor- and distribution-based MCIDs were 6-8 for the BESTest, 1-2 for the Mini-BESTest, and 2-3 for the Brief-BESTest. Conclusions: Improvements exceeding MCIDs established above are indicative of significant progress in balance function post-TKA. The BBS is not a recommended tool due to its low AUC value.