Differential ability of selected postural-control measures in the prediction of chronic ankle instability status

Abstract

Context: Chronic ankle instability (CAI) is a term used to identify a condition associated with recurrent ankle sprains and persistent symptoms. Balance deficits, evaluated using center-of-pressure (COP) force-plate measurements, have been shown to occur in people with CAI. Objective: To determine the differential abilities of selected force-plate postural-control measures to assess CAI. Design: Case-control study. Setting: Laboratory. Patients or Other Participants: A total of 63 individuals with CAI (30 men, 33 women: age = 22.3 ± 3.7 years, height = 169.8 ± 9.6 cm, mass = 70.7 ± 14.3 kg) and 46 healthy controls (22 men, 24 women: age = 21.2 ± 4.1 years, height = 173.3 ± 9.2 cm, mass = 69.2 ± 13.2 kg) volunteered. Intervention(s): Participants performed 3 10-second trials of quiet, single-limb stance on a force plate under 2 conditions: eyes open and eyes closed. Main Outcome Measure(s): Measures of COP area, COP velocity, COP SD, COP range of excursion, percentage of COP range used, time-to-boundary absolute minimum, timeto- boundary mean of the minima, and time-to-boundary SD of the minima were calculated. All measures with the exception of COP area were calculated in both the mediolateral (ML) and anteroposterior directions. For each measure, a receiver operator curve analysis was created, and the corresponding area under the curve was tested. The optimal diagnostic threshold value for each measure was determined, and the corresponding positive and negative likelihood ratios were calculated. Results: Three eyes-closed, single-limb force-plate measures (COP ML SD, ML percentage of COP range used, and time-to-boundary absolute minimum) predicted CAI status. However, all 3 measures had positive likelihood ratios associated with only small shifts in the probability of a patient with a positive test having CAI and negative likelihood ratios associated with very small shifts in the probability of a patient with a negative test not having CAI. Conclusions: No single force-plate measure was very effective in predicting if an individual had CAI or not. © 2011 by the National Athletic Trainers' Association, Inc.