Reza Tavakoli Darestani - Department of Orthopedic and Trauma Surgery, Shahid Beheshti University of Medical Sciences, Tehran, Iran.
Sina Afzal - Department of Orthopedic and Trauma Surgery, Shahid Beheshti University of Medical Sciences, Tehran, Iran.
Mojtaba Baroutkoub - Department of Orthopedic and Trauma Surgery, Shahid Beheshti University of Medical Sciences, Tehran, Iran.
Amin Norouzbeygi - Department of Orthopedic and Trauma Surgery, Shahid Beheshti University of Medical Sciences, Tehran, Iran.
Hasan Barati - 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 ۲۰۱۹ and ۲۰۲۱ 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 ۱۳۵ patients, those with RCT exhibited significantly higher CSA values (۳۷.۳) compared to the impingement syndrome group (۳۰.۲۵) and control group (۲۹.۹). CSA showed high sensitivity (۱۰۰%) and specificity in diagnosing RCT at a cut-off value ۳۵.۱. In diagnosing impingement syndrome, CSA demonstrated a sensitivity of ۶۰% and specificity of ۶۶.۷% at a cut-off of ۳۰.۲۵. 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.

Shoulder Pain, Rotator cuff tear, Shoulder impingement syndrome, Critical shoulder angle, Iran