Validity and reliability of smartphone-based application for chronic ankle instability

Abstract

Background/aims Ankle instability is one of the most common injuries that can occur during everyday life, sports and exercise. Recently, smartphone accelerometers have been used to measure single leg balance associated with ankle instability, because they are easy to use, inexpensive and can be used in small spaces. Thus, the purpose of this study was to introduce and investigate the intra- and inter-rater reliability of the smartphone accelerometer when assessing ankle instability. Methods A total of 26 individuals who had ankle instability were recruited. The single leg stance balance was measured using a smartphone accelerometer (Accelerometer application) and a force platform (I-Balance) for 5 seconds with their eyes open or their eyes closed. Results In the eyes open position, intra-rater reliability of the smartphone accelerometer was excellent for both raters (intraclass correlation coefficient: 0.87–0.90); and the inter-rater reliability was moderate (intraclass correlation coefficient: 0.71). In the eyes closed position, the intra-rater reliability of the smartphone accelerometer was excellent for both raters (intraclass correlation coefficient: 0.90–0.93); the inter-rater reliability was good (intraclass correlation coefficient: 0.82). Additionally, there were fair positive correlations between the smartphone accelerometer and the Cumberland Ankle Instability Tool, and between the smartphone accelerometer and I-Balance (r=0.33, 0.30 respectively). Conclusions The present study demonstrated excellent intra-rater reliabilities of two raters and moderate to good inter-rater reliabilities. The smartphone accelerometer offers several important advantages as a potential portable medical device to assess ankle instability accurately. Although there was a positive correlation, the relationships between the smartphone accelerometer and Cumberland Ankle Instability Tool and that between the smartphone accelerometer and I-Balance were fair. Future studies should investigate the validity of the smartphone accelerometer as a portable medical device for determining ankle instability.