Minimal Detectable Change Scores For Measures of Functional Balance in Adolescents With Chronic Ankle Instability

Abstract

Chronic Ankle Instability (CAI) is an issue that can affect individuals with a history of ankle sprains. Improving functional balance is one of the key goals in ankle rehabilitation programs. However, the threshold for defining a meaningful level of improvement for certain assessments has not been determined. PURPOSE: To establish the minimal detectable change (MDC) values for 2 different functional balance assessments in an active adolescent population with CAI. METHODS: Forty-three active adolescents with CAI (20 males and 23 females, 16±1 years, 171.75±12.05cm, 69.38±18.36kg). CAI inclusion criteria consisted of ankle sprain history, current symptoms of pain, weakness and instability and repeated episodes of giving-way. Participants completed 4-weeks of either strength training, balance board training, combination training (completion of both strength and balance board exercises) or no intervention. Dependent variables were pre and post-intervention scores for two measures of functional balance: side-hop test required participants to hop 30-centimeters medially/laterally for 10 repetitions and figure-of-8 hop test required participants to hop in a figure-of-8 pattern over a 5-meter distance for 2 repetitions. Both tests were completed twice on the involved leg. Hopping ability was measured in time to complete (seconds). A positive change score indicated improvement by a decrease in time needed to perform each test. The MDC with 95% confidence intervals was calculated for each variable [MDC = 1.96SD x (1-ICC)1/2 x (2)1/2]. RESULTS: Average pre and post-intervention scores were 12.55±4.51sec and 10.06±2.45sec for side-hop and 14.60±2.70sec and 13.00±1.80sec for figure-of-8 hop respectively. MDC was 2.60sec for both side-hop and figure-of-8 hop. These values reflect the minimal score necessary to be 95% confident that any measured change surpasses the statistical error associated with the test. Approximately 34.38% of the intervention participants had a clinically meaningful change of >2.60 seconds for side-hop test and 31.25% for figure-of-8 hop test. CONCLUSIONS: When these functional balance tests are used to detect beneficial changes from rehabilitation interventions, these MDC scores should be used as a minimum threshold to detect a true and clinically meaningful change.