Interobserver agreement in the classification of rotator cuff tears

Background: Six classification systems have been proposed for describing rotator cuff tears designed to help understand their natural history and make treatment decisions. Purpose: To assess the interobserver variation for these classification systems and identify the method with the best interob-server agreement. Study Design: Cohort study (diagnosis); Level of evidence, 2. Methods: Six rotator cuff tear classification systems were identified in a literature search. The components of these systems included partial-thickness rotator cuff tears and classification by size, shape, configuration, number of tendons involved, and by extent, topography, and nature of the biceps. Twelve fellowship-trained orthopaedic surgeons who each perform at least 30 rotator cuff repairs per year reviewed arthroscopy videos from 30 patients with a random assortment of rotator cuff tears and classified them by the 6 classification systems. Interobserver variation was determined by a kappa analysis. Results: Interobserver agreement was high when distinguishing between full-thickness and partial-thickness tears (0.95, κ = 0.85). The investigators agreed on the side (articular vs bursal) of involvement for partial-thickness tears (observed agreement 0.92, κ = 0.85) but could not agree when classifying the depth of the partial-thickness tear (observed agreement 0.49, κ = 0.19). The best agreement for full-thickness tears was seen when the tear was classified by topography (degree of retraction) in the frontal plane (observed agreement 0.70, κ = 0.54). Conclusion: With the exception of distinguishing partial-thickness from full-thickness rotator cuff tears and identifying the side (articular vs bursal) of involvement with partial-thickness tears, currently described rotator cuff classification systems have little interobserver agreement among experienced shoulder surgeons. Researchers should consider describing full-thickness rotator cuff tears by topography (degree of retraction) in the frontal plane.