Reliability of a 3 T MRI protocol for objective grading of supraspinatus tendonosis and partial thickness tears

BACKGROUND: Partial thickness supraspinatus tears and tendonosis can be managed either nonoperatively or by various arthroscopic techniques. New biologic treatment approaches are currently being investigated. MRI is commonly used for objective imaging outcome evaluation but there is a lack of reliability studies. We propose a novel MRI classification of partial supraspinatus tears and tendonosis and evaluate its inter-observer and intra-observer reliability. METHODS: Digital MRI scans (3 Tesla) of 65 patients investigated for assessment of supraspinatus pathology or subacromial impingement were evaluated by three independent and experienced musculoskeletal (MSK) radiologists. Tendonosis (absent, focal, generalized), partial thickness (PT) tears (absent, 0%–25% PT, 25%–50% PT, 50%–100% PT, and full thickness tears), and anteroposterior extent of tears (less than 5 mm, 5–10 mm, greater than 10 mm) were scored by each radiologist on two separate occasions (t1, t2), 2 months apart. The inter-observer and intra-observer agreement and weighted kappa values for each parameter were calculated. RESULTS: The range of weighted intra-observer kappa (IAK) was 0.84–0.93 for evaluation of tendonosis; 0.84 (all raters) for depth of partial thickness, 0.74–0.84 for AP tear size, and 0.83–0.85 for the total score. The range of weighted inter-observer kappa (IEK) over two time points (t1, t2) was 0.55–0.74 for tendonosis, 0.69–0.84 for depth for partial thickness tears, 0.57–0.80 for AP tear size, and 0.63–0.80 for the total score. CONCLUSION: A comprehensive MRI grading protocol is proposed and is reliable for the evaluation of supraspinatus tendonosis and partial thickness tears with good to excellent kappa values. This rotator cuff MRI protocol can be applied to evaluate morphological tendon outcomes after different treatment modalities. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (doi:10.1186/s13018-014-0128-x) contains supplementary material, which is available to authorized users.