Objectives: The aim of this study was to evaluate the psychometric properties of a new x-ray scoring system for calcific tendinopathy of the rotator cuff (CTRC).
Methods: This is a post-hoc analysis of the CALCECHO trial. All patients received an ultrasound-guided puncture and lavage of their calcification. Clinical data and x-rays from baseline and follow-up visits at 7 days (D7), 3 months (M3) and 12 months (M12) were used. The scoring system was based on the reduction in size and density of the calcification compared to the initial x-ray (0 = no change; 1 = decrease of less than 50%; 2 = decrease of between 50 and 90%; 3 = decrease of more than 90%; 4 = complete disappearance). Inter-observer and intra-observer reliability were established between 3 independent investigators (2 experts and one junior) using weighted Kappa calculation. Construct validity was assessed as well as predictive validity and sensitivity to change.
Results: Between the two experts, inter-reader reliability was at 0.677, 0.744 and 0.656 at D7, M3 and M12 respectively. Intra-reader reliability was between 0.577 and 0.836 for the two expert readers and between 0.519 and 0.697 for the junior reader. Our score was correlated with shoulder pain and function at M3 and M12 and the score at M3 was predictive of the clinical outcome at M12. Finally, sensitivity to change was 0.8.
Conclusions: Our new score presented good psychometric properties and was correlated with clinical data. It could be useful in the follow-up of patients treated for CTRC.