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, Waleed Albishi et al conducted a 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 cuff s was also included in the study as a control group for comparison.
The key findings of the study were:
• A total of 160 patients with RCT and 106 matched control patients with a normal rotator cuff were included in the 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).
• 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.
• 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.
The authors concluded – ‘Patients included in our study had symptomatic and painful RCT, had failed all conservative management, and eventually required surgical intervention. These patients were found to have elevated CSA and AI angles. CSA and AI are reliable measurements that are straightforward to calculate independently using a standard shoulder X-ray, provided it is properly taken and ensuring it is a true AP of the shoulder. We found that both measurements are equally effective in predicting the risk of symptomatic RCT and may be used in the primary healthcare setting to screen patients for RCT. Our study confirmed that both X-ray and MRI are equally sufficient for measuring CSA, allowing physicians to choose between these techniques.’
Further reading:
Elevated Critical Shoulder Angle and Acromion Index as Predictors of Symptomatic Rotator Cuff Tears: A Comparative Case–Control Study
Waleed Albishi et al
Indian Journal of Orthopaedics (2025) 59:785–792
https://doi.org/10.1007/s43465-024-01310-4
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