Goutallier classification is widely used to describe fatty infiltration within a rotator cuff muscle belly. Initially developed based on axial CT images, the grading system has been extrapolated to magnetic resonance imaging (MRI) over time. Goutallier classification based on MRI is widespread, but no one has yet studied if its reliability can be deteriorated by the size of the cuff retraction . The aim of our study was to evaluate whether the Goutallier grading system should be adjusted to the cuff tear size or if it is reliable regardless the amount of retraction.
This was a prospective observational study. MRIs of 81 patients reflecting a range of tear sizes were compiled and 3 parasagittal cuts from each series were extracted and de-identified (total 243 images). The image based on the coronal view with the greatest supraspinatus tendon retraction was used for tear-size classification according to Cofield classification. The most lateral cut in which the scapular spine is still attached to the scapular body represented the traditionally used ‘baseline” cut for Goutallier classification. Two additional cuts were obtained 3 and 6 slices medially from the first. Nine clinicians (3 fellowship trained upper extremity surgeons, 2 upper extremity fellows, 2 orthopedic residents and 2 fellowship trained musculoskeletal radiologists) assigned Goutallier classifications to each of the four RC muscles based on the three MRI cuts. Evaluation of all images was repeated 3 times with a 7-day gap between each session and images re-randomized for each session. A threshold of Krippendorff’s alpha of 0.8 was set a priori and reviewers achieving 0.8 or higher were included in further analysis with the purpose of revealing the impact of size of cuff tear and slice on Goutallier grade. Kruskall-Wallis was used to determine the impact of expertise on intra-rater reliability.
Five of 9 clinicians achieved a level of 0.8 or higher reflecting high intra-rater reliability. Reliability was not significantly associated with expertise (p=0.3089). Based on only the raters with high intra-rater reliability, there was a significant difference in Goutallier grade between slices in supraspinatus (p=0.007), infraspinatus (p<0.001), and subscapularis (p=0.0193), but not teres major (p=0.4227). The tendency was to give the lower grade for same muscles, in more medial MRI cuts.
Comclusion: Goutallier classification is influenced by the slice reviewed, the size of the tear, and the muscle being evaluated. A systematic approach to grading based on MRI needs to be established with adequate training. Choosing the right MRI image can be crucial for accurate diagnosis and treatment planning, especially as torn rotators cuff tendons tend to retract over the time and retraction is a well-known risk factor for a non-successful repair.