One year results of a randomized controlled trial on radial Extracorporeal Shock Wave Treatment, with predictors of pain, disability and return to work in patients with subacromial pain syndrome

Radial Extracorporeal Shock Wave Therapy (rESWT) is increasingly used to treat patients with subacromial pain syndrome despite conflicting evidence of its effectiveness. Better knowledge regarding prognostic factors may contribute to the improvement in treatment and prognosis for the patients. The first aim of this study was to evaluate the effect of rESWT in addition to supervised exercises in patients with subacromial pain syndrome after one year. The second aim was to identify predictors of pain and disability and work status after one year in this patient group. A randomized, double-blind, sham-controlled trial. An outpatient shoulder clinic of a University hospital. Patients aged 25 to 70 years, with subacromial pain syndrome lasting at least three months were included and randomly assigned to receive either rESWT and supervised exercises or sham rESWT and supervised exercises. The Shoulder Pain and Disability Index (SPADI) and work status were assessed after one year. We screened 265 patients and enrolled 143; 74 were allocated to receive sham rESWT and exercises, and 69 were allocated to receive rESWT and exercises. After one year, no differences were found for the SPADI Score (mean difference -1.6, 95% confidence interval (CI) -10.2 to 7.0, P=0.71). Subgroup analysis of patients with calcification in the rotator cuff demonstrated no significant additional effect of rESWT to supervised exercises (mean difference -6.3, 95% CI -22.4 to 9.8, P=0.44). Marital status (single), frequent use of pain medication, not working at baseline, negative outcome expectations, low self-reported general health status and few supervised exercise sessions predicted a poor outcome on SPADI after one year. Radial ESWT was not superior to sham rESWT in addition to supervised exercises in the long term for patients with subacromial pain syndrome. The identified predictors for pain, disability and work should be assessed in future studies and addressed by clinicians in order to improve the effectiveness of supervised exercises. Radial ESWT should not be recommended for patients with subacromial pain syndrome. Clinicians should assess patient`s outcome expectations, and if possible reduce the use of pain medication and sick leave in this patient group.