Effectiveness of High-Volume Corticosteroid Injection Diluted with Saline in Subacromial Impingement Syndrome: A Randomized Trial.

BACKGROUND: The aim of this study was to determine whether the efficacy of high-volume, ultrasound-guided subacromial injection with corticosteroid (CS) diluted with normal saline is superior to that of low-volume injection in patients with subacromial impingement syndrome (SIS). METHODS: This study included 70 patients diagnosed with SIS. Patients were randomized into either the high-volume CS injection group [1 mL, 40 mg triamcinolone acetonide (TA); 1 mL, 2% lidocaine; 8 mL normal saline mixture] or the low-volume CS injection group (1 mL, 40 mg TA; 1 mL, 2% lidocaine; 1 mL normal saline mixture). Additional instructions for a home exercise program were provided after the injection. Assessments were made at baseline and 4- and 12-weeks post-injection, using the following measurements: Shoulder Pain and Disability Index (primary outcome); visual analogue scale (pain); active range of motion measurements (abduction, flexion, and external and internal rotations); and Western Ontario Rotator Cuff Index. RESULTS: There were no significant differences between the groups in terms of demographic or shoulder-pain-related data at baseline. Both groups showed significant improvements in all outcomes at 4- and 12-weeks post-injection. However, there was no significant difference between the groups for any outcome. Post-injection adverse events and drug consumption during follow-up were comparable between the groups. CONCLUSIONS: All outcome measures significantly improved in both the high- and low-volume injection groups, with no significant between-group differences. This suggests that high-volume CS injections provide no additional benefit over low-volume injections for reducing pain and improving function in patients with SIS.