Abstract
Ankle joint instability after acute lateral ankle sprain (LAS) is an important factor for deciding treatment strategies. Nevertheless, the degree of ankle joint mechanical instability as a criterion for making clinical decisions is unclear. This study examined the reliability and validity of an Automated Length Measurement System (ALMS) in ultrasonography for assessing real-time anterior talofibular distance. Using a phantom model, we tested whether ALMS could detect two points within a landmark following movement of the ultrasonographic probe. Furthermore, we examined whether ALMS was comparable with the manual measurement method for 21 patients with an acute LAS (42 ankles) during the reverse anterior drawer test. Using the phantom model, ALMS measurements showed excellent reliability, with errors below 0.4 mm and with a small variance. The ALMS measurement was comparable to manually measured values (ICC = 0.53-0.71, p < 0.001) and detected differences in talofibular joint distances between unaffected and affected ankles of 1.41 mm (p < 0.001). ALMS shortened the measurement time by one-thirteenth for one sample compared to the manual measurement (p < 0.001). ALMS could be used to standardize and simplify ultrasonographic measurement methods for dynamic joint movements without human error in clinical applications.