Incidence of full-thickness rotator cuff tear after subacromial corticosteroid injection: a 12-week prospective study.

INTRODUCTION: Rotator cuff tears (RCT) are a common source of shoulder pain, with an incidence ranging between 5% and 40%. The influence of corticosteroid injections on the incidence of RCT remains unknown. The aim of this study was to estimate the incidence of full-thickness RCT 12 weeks after a subacromial corticosteroid injection in patients with shoulder pain. PATIENTS AND METHOD: We made a prospective, open-label study in patients with unilateral painful shoulder without previous local corticosteroid injection. Ultrasound assessments were made at the first (baseline) and last (Week 12) visits by an experienced radiologist. A rheumatologist did the clinical examination. Patients with full-thickness RCT at the first visit were excluded. All patients received a subacromial injection of triamcinolone acetate 40 mg. RESULTS: One hundred and two patients with shoulder pain were initially evaluated: 49 (48%) were excluded due to full-thickness RCT on ultrasound assessment. Therefore, 53 patients completed the study (34 female, mean age 60.8 years, mean time of evolution 9.6 months). In the first ultrasound evaluation, 24 patients (45.3%) had a partial-thickness tear. At 12 weeks after the corticosteroid injection, 9 (17%) patients developed full-thickness RCT, 66.6% of which occurred in patients with previous partial-thickness RCT. Corticosteroid injection significantly improved symptoms (p = 0.0001 for pain VAS score) and range of motion (p = 0.002 for forward elevation and external rotation). CONCLUSIONS: Seventeen percent of patients with shoulder pain suffered a full-thickness RCT 12 weeks after subacromial corticosteroid injection. Corticosteroid injection is highly effective in improving clinical symptoms of rotator cuff tendinopathy at 12 weeks.