Degenerative Posterosuperior Rotator Cuff Tear Scoring System - An Indirect Diagnostic Aid Based on Medical History and CT

Background Rotator cuff tear (RCT) is a primary cause of shoulder pain and a leading source of shoulder disability in later stages. Although various computed tomography (CT) based measurements of the shoulder have been identified as predictors for RCT, we hypothesize that a combination of predictors will provide superior diagnostic and predictive performance compared to individual predictors. Thus, the aims of this study are: (i) to integration of multiple shoulder CT-based measurement parameters combined with physical examination for predicting degenerative posterosuperior rotator cuff tears. (ii) to develop a scoring system based on these predictors for estimating the likelihood of degenerative posterosuperior posterosuperior rotator cuff tears ( RCT-PT). (iii) To provide a diagnostic basis and predict the risk of degenerative posterosuperior rotator cuff tears for patients with contraindications to magnetic resonance imaging(MRI), an inability to cooperate with or complete the examination, or for whom MRI is deemed unnecessary. Methods This retrospective study analyzed 326 cases who underwent both shoulder CT and MRI examinations at our hospital. Based on the shoulder MRI findings, patients were stratified into two groups: a rotator cuff tear group and a control group. The selected predictors included the Critical Shoulder Angle (CSA), Acromial Index (AI), Goutallier grade of fatty infiltration, Supraspinatus Occupation Ratio, the Hounsfield Unit (HU) ratio of the deltoid to supraspinatus muscle, and other variables such as gender, age, symptom duration, BMI and physical examination findings. These factors were analyzed using univariate and multivariate analyses. The factors identified in the multivariate analysis were subsequently integrated into a scoring system based on their odds ratios (OR). Results Multivariate analysis identified the following independent risk factors: age (p < 0.01, OR = 1.090), fatty infiltration grade (p = 0.047, OR = 2.252), symptom duration (p = 0.012, OR = 1.036), critical shoulder angle (p = 0.028, OR = 1.175), acromial index (p = 0.034, OR = 1.068), and physical examination findings including the Hug-up test (p < 0.01, OR = 11.061), Drop arm sign (p = 0.036, OR = 3.124), and External Lag test (p < 0.01, OR = 4.558). Subsequently, a 12-point scoring system was developed. Based on the weighting derived from the multivariate analysis odds ratios, 1 point each was assigned to age, symptom duration, supraspinatus occupation ratio, critical shoulder angle, and acromial index; 2 points were assigned to fatty infiltration grade; and 3 points, 1 point, and 1 point were assigned to the Hug-up test, Drop arm sign, and External Lag test, respectively. A score of 6.5 was established as the threshold for predicting degenerative posterosuperior rotator cuff tears, yielding a sensitivity of 0.861 and a specificity of 0.864. Conclusion This scoring system integrates shoulder CT measurement parameters with clinical factors, providing a complementary tool for predicting rotator cuff tears. It enables risk assessment based on CT findings and physical examination results, allowing for preliminary assessment in patients who have undergone CT imaging while also offering a reliable predictive alternative for patients with MRI contraindications. Thus, it addresses the clinical limitations associated with restricted access to MRI.