Grading the severity of the rotator cuff tendinosis on MRI: assessment of inter-observer agreement and evaluation of a novel objective assessment tool

Introduction: MRI is generally considered the modality of choice for the assessment of rotator cuff pathology including tendinosis. Assessment of severity is currently subjective primarily based on tendon morphology and signal intensity. Limited data are available evaluating the inter-observer agreement regarding the assessment of tendinosis severity. Methods: One hundred and twenty-four patients were prospectively enrolled in the study. Patients included were referred to two private radiology practices for shoulder MRI for any reason. Two musculoskeletal radiologists assessed the severity of tendinosis independently. Supraspinatus tendon signal was evaluated with a ROI and compared to the adjacent deltoid muscle signal, generating a ratio of tendon: muscle signal, termed the ‘objective TM ratio’. The relationship between the subjective assessment of tendinosis severity and objective ratio was examined. Inter-observer agreement was also calculated. Results: Tendinosis severity was graded as normal in 36 and 11 patients by readers 1 and 2, respectively, mild in 45 and 48 patients, moderate in 26 and 48 patients and severe in 10 and 10 patients. Inter-observer agreement is classified as fair (0.31 kappa co-efficient). Mean objective TM ratio increased on both the PD and TS F2 sequences as the subjective grade of tendinosis severity increased. Conclusion: A novel means of evaluating rotator cuff tendinosis severity is presented, demonstrated to correlate with the subjective grade of tendinosis severity. Further research is required to assess the utility of such objective measurements across varying imaging protocols whilst understanding the inherent limitations with quantifying signal intensity on MRI.