Effect of the Critical Shoulder Angle on the Efficacy of Ultrasound-Guided Steroid Injection for Subacromial Bursitis

The critical shoulder angle (CSA) is associated with impingement and rotator cuff lesions, and ultrasound-guided corticosteroid injection is effective for subacromial bursitis. However, because the efficacy of this treatment varies, this study investigated the effect of the CSA on the efficacy of corticosteroid injection in the subacromial space. Patients who received a diagnosis of subacromial bursitis after a clinical physical examination and ultrasound were enrolled prospectively from May 2019 to December 2021. Patients’ baseline variables and CSAs were assessed before intervention. Patients’ shoulder pain and disability index (SPADI), visual analog scale (VAS), and shoulder joint range of motion (ROM) scores were assessed at 2, 6, and 12 weeks after ultrasound-guided corticosteroid injection. All participants were divided into CSA > 38° and CSA ≤ 38° groups. We conducted the intragroup and intergroup comparisons of the variables and performed Pearson analysis to identify potential correlations between the CSA and outcome parameters. A total of 55 patients were enrolled in this study. Of these, 28 were included in the CSA > 38° group and 27 in the CSA ≤ 38° group. The baseline variables of the two groups did not differ. In the intragroup and intergroup comparisons, although VAS, SPADI, and ROM scores improved up to 12 weeks after intervention, no difference was identified between groups. The Pearson analysis revealed a positive correlation (r = 0.30, p = 0.024) between the CSA and VAS scores before the intervention. However, no correlation was found between the CSA and follow-up parameters. The CSA was not associated with the clinical efficacy of ultrasound-guided corticosteroid injection for subacromial bursitis.