Intra- and Inter-Rater Reliability of Magnetic Resonance Imaging Measurements of Supraspinatus Muscle Thickness, Acromiohumeral Distance, and Coracohumeral Distance in Patients with Shoulder Pain

ABSTRACT
Aim: The aim of this study was to evaluate the intra- and inter-rater reliability coefficients of the supraspinatus muscle thickness (SMT ), acromiohumeral distance (AHD), and coracohumeral distance (CHD) in patients with shoulder pain. 
Materials and Methods: This retrospective study included 80 patients who presented with complaints of shoulder pain at a single centre between January 2023 and January 2024. The supraspinatus muscle thickness, acromiohumeral distance, and coracohumeral distance measurements were obtained one week apart by two observers. The intraclass correlation coefficient (ICC), minimum detectable change, and standard error of measurement were subsequently calculated. 
Results: AHD intra-rater reliability results evaluated on coronal sections were excellent (Rater 1, ICC=0.96; 95% CI, 0.94-0.97; Rater 2 ICC=0.75; 95% CI, 0.61-0.84). AHD intra-rater reliability results evaluated on sagittal sections were excellent (Rater 1, ICC=0.94; 95% CI; 0.91-0.96; Rater 2 ICC=0.77; 95% CI, 0.64-0.85). The results of CHD measured using coronal sections were good (Rater 1, ICC=0.85; 95% CI, 0.76-0.90; Rater 2 ICC=0.82; 95% CI, 0.71-0.88). SMT measurement results measured using coronal sections were excellent (Rater 1, ICC=0.98; CI, 0.98-0.99; Rater 2, ICC=0.89; 95% CI, 0.82-0.93).The inter-rater reliability values were good for AHD-Coronal (ICC= 0.75; 95% CI, 0.61-0.84) and AHD-Sagittal (ICC=0.86; 95% CI, 0.79-0.91), were fair for CHD evaluated on coronal sections (ICC=0.74; %95 CI, 0.58-0.83), and were excellent for SMT evaluated on coronal sections  (ICC=0.92; 95% CI, 0.87-0.95). 
Conclusion: These results suggest that magnetic resonance imaging measurements of the supraspinatus muscle thickness and acromiohumeral distance can be reliable and consistent for the clinical evaluation of patients with shoulder pain. 
Keywords: Reliability, shoulder measurement, magnetic resonance imaging