Elevated Critical Shoulder Angle and Acromion Index as Predictors of Symptomatic Rotator Cuff Tears: A Comparative Case–Control Study

Rotator cuff tears are one of the most frequent pathologies behind shoulder pain among patients worldwide. Some studies have suggested a relationship between critical shoulder angle (CSA), acromion index (AI) and the diagnosis of a rotator cuff tear (RCT). Given the large variation among studies in the literature, we conducted this study to investigate the relationship between these radiologic values and the presence of symptomatic RCTs.

Medical records, radiographs, and MRIs of patients who had undergone rotator cuff repair for symptomatic tears were collected. Patients with normal rotator cuffs was also included in the study as a control group for comparison.

A total of 160 patients with RCT and 106 matched control patients with a normal rotator cuff were included in our study. Among the RCT group, 87.5% of patients had a CSA value greater than 35° when measured by X-ray, and 65.6% had a CSA greater than 35° when MRI was utilized (p < 0.0001). In addition, 83.125% of patients had an AI greater than 0.7194 (p < 0.0001). The mean CSA measured by X-ray was significantly higher in the tear group (M = 40.27, SD = 4.70) compared to the control group (M = 33.70, SD = 5.39), p < 0.001. Similarly, the mean CSA measured by MRI was significantly higher in the RCT group (M = 37.24, SD = 4.37) compared to the control group (M = 32.13, SD = 4.76), p < 0.001. The mean AI measured by X-ray was also significantly higher in the RCT group (M = 0.80, SD = 0.08) compared to the control group (M = 0.64, SD = 0.10), p < 0.001.

Patients with symptomatic RCT had significantly elevated CSA and AI, whether measured by X-ray or MRI, compared with patients with normal rotator cuffs.