Minimal Clinically Important Difference of Four Commonly Used Balance Assessment Tools in Individuals after Total Knee Arthroplasty: A Prospective Cohort Study

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 previously established 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.

POPULATION:

Inclusion criteria: 1) first primary TKA with diagnosed knee osteoarthritis; 2) aged 50-85 yr.

EXCLUSION CRITERIA:

1) TKA due to rheumatoid arthritis of the knee or traumatic injury; 2) known medical conditions that influence balance ability. 146 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, gait and balance training, once or twice per week between assessments.

MAIN OUTCOME MEASURES:

Participants were assessed on the BESTest, Mini-BESTest, Brief-BESTest, BBS, and Functional Gait Assessment [FGA] 2 and 4 wk 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%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.

CONCLUSION:

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.