Inter- and intra-observer reliability of a smartphone application for measuring hallux valgus angles

BackgroundMeasurement of radiological angles can be useful in the planning of the management of patients with hallux valgus. A smartphone application offers an alternative way of measuring these angles in a clinic setting. We compared the reliability (inter- and intra-observer) of this method to the use of PACS.MethodsRadiographs of 30 feet from new patients referred with hallux valgus were examined and angles (HVA, IMA, and DMAA) recorded using the smartphone application and PACS.ResultsThe smartphone application provided good inter-observer reliability for HVA and IMA (r = 0.93 and r = 0.79 respectively). Intra-observer reliability for HVA and IMA was also found to be good (r = 0.93–0.97 r = 0.82–0.93 respectively). The inter- and intra-observer reliability for using this method to measure DMAA fell below useful levels (r < 0.60 in each case).ConclusionsThis smartphone application provides a reliable method to measure HVA and IMA but we would not recommend it to measure DMAA.