Fat distribution in the rotator cuff interval determining the coracohumeral ligament visualization: Magnetic resonance imaging findings

Abstract

ABSTRACT Objective: The purpose of this study was to analyze how fat distribution in the rotator cuff interval (RCI) in normal volunteer shoulders determines the coracohumeral ligament (CHL) visualization, including the CHL visualization rate, type, and thickness, using routine magnetic resonance imaging (MRI). Materials and Methods: This study prospectively analyzed 120 shoulder joints in 60 normal volunteer individuals (30 males and 30 females) using MRI to identify the fat distribution type in the RCI as well as the CHL visualization rate, type, and thickness. Results: The fat in the RCI was visualized in 110 of 120 shoulders (91.7%) while the fat in the RCI was not identifiable in 8.3% of normal volunteer shoulders. The fat distribution in the RCI was classified into five types: Type A (52.5%), Type B (26.7%), Type C (5.8%), Type D (6.7%), and Type E (8.3%). The CHL types included the horizontal type (73.3%), upsloping type (12.5%), downsloping type (5.9%), and unseen type (8.3%) (The CHL was not identifiable in 8.3% of normal volunteer shoulders). No significant difference existed for the fat distribution types in the RCI or the CHL visualization rate, types, or thickness in either different lateral shoulders or different gender shoulders, using a Chi-square test (P > 0.05). In addition, no significant correlation emerged between body mass index (23.4 ± 2.5, n = 110) and the CHL thickness (3.1 ± 1.3 mm) in normal volunteer shoulders, using the Pearson correlation test (n = 110) (r = −0.095, P> 0.05). Conclusion: MRI is a satisfactory method for determining the fat distribution in the RCI and CHL depiction in normal volunteer shoulders. The fat distribution in the RCI determines the CHL visualization, including the CHL visualization rate, type, and thickness.