Efficacy of a Mobile Health-Supported Home-Based Resistance Exercise After Ultrasound-Guided Corticosteroid Injection in Chronic Subacromial Bursitis: A Randomized Controlled Trial

Background: Corticosteroid injections provide short-term relief for chronic subacromial bursitis but are associated with high recurrence rates. This study investigates the efficacy of a mobile health-supported home-based resistance exercise program compared with exercise education in patients with chronic recurrent subacromial bursitis after ultrasound-guided corticosteroid injections. Methods: Participants with chronic subacromial bursitis were assigned via computer-generated block randomization to either an intervention group receiving ultrasound-guided corticosteroid injections followed by a 12-week home-based exercise program (50 min strengthening and resistance/session, 5 days per week) supported via instant messaging applications, or a control group receiving the same injection followed by printed educational materials covering the same exercise protocol. Shoulder Pain and Disability Index (SPADI) scores, Visual Analog Scale (VAS) pain scores and active pain-free range of motion (ROM) were evaluated by a blinded assessor at weeks 4 and 12. Between-group comparisons were analyzed using two-way ANOVA after confirming normality and homoscedasticity. Results: Fifty-three patients (mean age: 55.6 ± 10.5 years; 47.2% female) were randomized to the intervention (n = 27) or control (n = 26) groups. Significant interaction effects were identified for SPADI (p = 0.040) and ROM (abduction: p = 0.036/ flexion: p = 0.032). Post hoc analysis revealed that the intervention group exhibited a significantly greater reduction in SPADI scores (p = 0.007, d = 0.72) and greater increase in abduction ROM (p = 0.004, d = 0.84) at 12 weeks; both gains surpassed the MCID. Conclusions: A mobile health-supported home-based resistance exercise program can significantly extend the benefits of corticosteroid injections in patients with chronic subacromial bursitis. Trial Registration: NCT06220643, registered 14 December 2023.