Evaluation of critical shoulder angle in patients with shoulder impingement syndrome and rotator cuff tear

Document Type : Original Article


Department of Orthopedic and Trauma Surgery, Shahid Beheshti University of Medical Sciences, Tehran, Iran.



Introduction: Shoulder pain is a common orthopedic complaint, with rotator cuff tear (RCT) and impingement syndrome as prevalent causes. The critical shoulder angle (CSA), the angle between the glenoid and acromion, has been implicated in the development of RCT. However, comprehensive evaluations of CSA in Iranian patients with impingement syndrome and RCT are lacking.
Methods: This case-control study assessed CSA in patients with RCT and impingement syndrome. Patients presenting with severe shoulder pain between 2019 and 2021 were included, with CSA measurements taken from anterior-posterior radiographs. Diagnostic performance was evaluated. The control group comprised patients with other shoulder pathologies.
Results: Of 135 patients, those with RCT exhibited significantly higher CSA values (37.3) compared to the impingement syndrome group (30.25) and control group (29.9). CSA showed high sensitivity (100%) and specificity in diagnosing RCT at a cut-off value 35.1. In diagnosing impingement syndrome, CSA demonstrated a sensitivity of 60% and specificity of 66.7% at a cut-off of 30.25.
Discussion: CSA emerged as a promising diagnostic tool for RCT, with its value exceeding the critical threshold. This finding aligns with international studies, suggesting the utility of CSA in the Iranian context. The study provides valuable insights into the diagnostic potential of CSA, particularly in the differentiation of shoulder pathologies within the Iranian population.
Conclusion: As assessed through radiographs, the critical shoulder angle is a reliable diagnostic measure to identify RCT and distinguish it from impingement syndrome. This research contributes to understanding shoulder pathologies in the Iranian population, emphasizing the clinical significance of CSA as a predictor for RCT.


Main Subjects

Volume 28, Issue 6
November and December 2023
Pages 957-964
  • Receive Date: 17 October 2023
  • Revise Date: 02 December 2023
  • Accept Date: 06 February 2024