Effectiveness of ultrasound in evaluation of fatty infiltration in rotator cuff muscles

Background: This study aimed to verify the diagnostic performance of Ultrasonography (US) in the evaluation of fatty infiltration (FI) in rotator cuff muscles and to analyze the diagnostic values of each measurement component. Methods: The degree of FI in 108 shoulders was assessed by magnetic resonance imaging (MRI) and US. MRI findings were graded by the Goutallier classification. US findings were graded by the Strobel method. Agreement between MRI and US findings was evaluated. The sensitivity and specificity for detecting FI and intraobserver reliabilities were also assessed. Results: US grading of the infraspinatus based on short-axis architecture showed good agreement (k = 0.62). US grading-based on architecture showed good agreement for both supraspinatus and infraspinatus in long-and short-axis scans (supraspinatus, k = 0.63; infraspinatus, k = 0.68), while that based on echogenicity showed moderate agreement (supraspinatus, k = 0.51; infraspinatus, k = 0.50). The sensitivity, specificity, positive predictive value, negative predictive value, and accuracy of detecting advanced FI were significant in both axes. Conclusions: US is effective for detecting advanced FI in the rotator cuff muscles. US can assess the infraspinatus more accurately than the supraspinatus, and architecture is a more decisive component of FI status than echogenicity.