Abstract
The purpose of this study was to evaluate infraspinatus muscle atrophy with regard to sagittal extent of rotator cuff tears using magnetic resonance imaging (MRI). A consecutive series of 43 patients (45 shoulders), who underwent MRI because they were suspected to have rotator cuff tear, was evaluated. Subjects consisted of 24 males and 21 females with an average age of 60 years old (range, 19-82). Rotator cuff tear size was determined using each slice of T2-weighted oblique coronal images of MRI. There were 16 intact shoulders (group A) and 29 rotator cuff tears, including eight tears localized only in the anterior 1/2 of the superior facet (group B),10 tears which extended to the posterior half of the superior facet (group C), and 11 tears which extended to the middle facet (group D). The infraspinatus was divided into 4 compartments using proximal muscular slices in T2-weighted oblique sagittal images and muscle atrophy in each compartment was classified into 4 grades (grades I, II, III, and IV) based on Goutallier's staging. Regarding muscle atrophy, no significant difference was observed between groups A and B. However, significant muscle atrophy was observed in group C in the upper 2 compartments and in group D in all compartments compared with group A. Infraspinatus muscle atrophy increased in both extent and degree in accordance with posterior extent of tears. Infraspinatus muscle atrophy increased in both extent and degree in accordance with posterior extent of tears. Recently, it has been reported through anatomical investigation that the infraspinatus muscle was inserted to the most anterior part of the greater tuberosity. The fact that group C demonstrated infraspinatus muscle atrophy indicated that the infraspinatus tendon could be involved in this type of rotator cuff tears.
