Clinical Y-view Versus 3-Dimensional Assessments of Intramuscular Fat in Patients with Full-Thickness Rotator Cuff Tears.

Rationale and Objectives. Recent evidence suggests an inhomogeneous distribution of intramuscular rotator cuff fat infiltration (FI) in a small sample of individuals with rotator cuff tears, yet clinically just a few slices at the scapular Y-view are used to evaluate FI in patients with rotator cuff tears. The purpose of this study was to determine if assessment of FI using the scapular Y-view is representative of the entire muscle in patients with full-thickness rotator cuff tears, and whether this varies by tear size. Materials and methods: Patients (N = 25) diagnosed with full-thickness rotator cuff tear and confirmed with magnetic resonance imaging (MRI) were included. Fat-water sequences were used to objectively quantify mean FI (%) in the entire 3D muscle and the mean from 3 slices at the Y-view. Mixed-model 2 x 2 ANOVAs were used to assess for differences between methods, and if results vary by tear-size. Results: There were no statistically significant differences between mean amount of FI of the entire 3D muscle and mean Y-view in the supraspinatus or infraspinatus muscles (p > 0.05). Additionally, this did not differ across tear size groups (p > 0.05). Conclusion: Results of this study suggest FI assessed in the Y-view is not different (mean difference < 1.0%) from FI of the entire 3D muscle in patients with full-thickness rotator cuff tears. Therefore, the clinical utility of evaluating rotator cuff intramuscular fat infiltration with the Y-view is further supported in patients with full thickness rotator cuff tears across tear sizes.