This study aims to assess and compare the effectiveness of two different volumes of local anesthetic combined with 40mg of triamcinolone for subacromial injections in treating patients with rotator cuff impingement syndrome

Patients with rotator cuff impingement syndrome were randomized to undergo subacromial injection with 10mL total volume of 1% lidocaine plus 40mg triamcinolone acetonide (n = 22), or a 4mL total volume of 1% lidocaine plus 40-mg triamcinolone acetonide (n = 23). Evaluations using a visual analog scale (VAS) for pain during motion, and the Western Ontario Rotator Cuff Index (WORC) were completed before treatment and 30 minutes, 2 weeks, and 8 weeks after injection.

Inclusion Criteria:

1. participants with clinically diagnosed the rotator cuff impingement
2. participants aged 20 years and older
3. at least 1 month's duration
4. pain of moderate to severe intensity, defined as a score of 5 or more points on a 10-cm visual analog scale (VAS) rated from 0 (no pain) to 10 (worst imaginable pain)

Exclusion Criteria:

1. patients with adhesive capsulitis of the shoulder (normal radiograph of affected shoulder, and restriction of passive motion >30° in ≥2 planes of movement)
2. previous trauma history at currently affected shoulder
3. previous corticosteroid injection history at the affected shoulder
4. abnormal calcification and/or primary osteoarthritis of the shoulder joint on plain radiographs
5. use of medication such as antiplatelet agent or anticoagulation.