Efficacy of hydraulic stretch-assist devices in treating ankle contracture: A retrospective study

Background Ankle contracture/arthrofibrosis is addressed with physical therapy or low-intensity stretch assist splints, requiring prolonged treatment and if clinician-set goals remain unmet, surgical intervention is considered. Mechanical therapy using a hydraulic stretch assist device with a high-intensity stretch protocol offers a potential non-operative alternative. This study evaluated the effectiveness of a hydraulic stretch-assist device in improving ankle dorsiflexion range of motion (ROM). Methods : This retrospective study reviewed patients from an internal database prescribed the Ermi Ankle Flexionater + device between October 2021 and May 2023 after plateauing in dorsiflexion recovery despite at least four weeks of standard treatment Dorsiflexion ROM was measured using the ErmiMotion application in straight- and bent-leg positions at baseline and follow-up. Changes between initial and final measurements were assessed using paired t-tests, with significance set at α< 0.05. Results : Seventy-four patients had complete data available. Treatment began 214 days after injury/surgery. The final dorsiflexion ROM significantly improved in straight (from 4.0°±10.8° to 12.5°±10.2°; p < 0.001) and bent leg positions (from 8.1°±11.7° to 15.0°±10.8°; p < 0.001). Effect sizes were large (Cohen’s d=0.86 and 0.80, respectively). Patients with severe motion loss showed marked improvement (straight: −7.7°±6.5° to 7.3°±11.4°; p < 0.001; bent: −9.1°±10.7° to 9.6°±10.3°; p = 0.001), with very large effect sizes (Cohen’s d=1.52 and 3.06, respectively). Conclusions : Treatment with a hydraulic stretch assist device was associated with improved dorsiflexion ROM in patients with ankle contracture, including those with severe limitations. These findings support consideration of using a hydraulic stretch assist device for individuals who do not respond adequately to standard treatments.