Proper site of corticosteroid injection for the treatment of idiopathic frozen shoulder: Results from a randomized trial

Abstract

Objective: The objective is to determine whether corticosteroid injection into the subacromial space wasnot inferior to intra-articular injection in patients with idiopathic frozen shoulder (FS), and whethercombined injections had an additive effect.Methods: Patients with idiopathic FS (n = 126) were randomly assigned to receive ultrasound-guidedintra-articular (IA group), subacromial (SA group), or combined IA and subacromial injections (IA + SAgroup). All groups received a total dose of 40 mg triamcinolone acetonide. The outcome measures includedthe visual analog scale (VAS) for pain, American Shoulder and Elbow Surgeon (ASES) shoulder score,subjective shoulder value (SSV), and passive range of motion before and at 3, 6, and 12 weeks aftertreatment.Results: There was significant effect of time on all measurements such that all measures improved in allgroups (P < 0.001) during the 12 weeks after treatment. Group-by-time interactions were significant forASES (P = 0.006), VAS (P < 0.001), SSV (P = 0.03), and internal rotation (P = 0.014). Between-group compar-isons revealed a significant improvement in the IA (P < 0.001) and IA + SA (P < 0.001) groups as compared tothe SA group. The IA + SA group demonstrated significant improvement in internal rotation as comparedto the IA group (P = 0.046).Conclusion: The efficacy of corticosteroid injection into the SA space in idiopathic FS was inferior toIA injection up to 12 weeks; however, combination injections had an additive effect on increasing theinternal rotation angle. These results indicate that although the glenohumeral joint is a major site in thepathogenesis of idiopathic FS, the SA space may be a contributing site.