Background <p>Rotator cuff tears (RCT) are a primary cause of shoulder pain and a leading source of shoulder disability in later stages. Magnetic resonance imaging (MRI) is the diagnostic gold standard but is not always feasible. Computed tomography (CT) is often available but provides limited direct soft-tissue information. Although various CT-derived 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. The primary objective of this study was to develop and validate a scoring system based on these factors to estimate the likelihood of a degenerative posterosuperior rotator cuff tear in patients for whom MRI is unavailable or contraindicated.</p> Methods <p>This retrospective study analyzed 326 cases who underwent both shoulder CT and MRI examinations at our hospital. MRI was the reference standard, dividing patients into a tear group (full-thickness tear of supraspinatus/infraspinatus) and a control group (intact cuff). Candidate predictors included: age, sex, Body mass index (BMI), symptom duration, physical exam findings (Hug-up test, Drop arm sign, Jobe test, External rotation lag test), and CT-derived parameters including the Critical shoulder angle (CSA), Acromial index (AI), Goutallier grade of fatty infiltration, Supraspinatus occupation ratio, and the Hounsfield unit (HU) ratio of the deltoid to supraspinatus muscle, sex, age, Duration of symptoms(DOS), BMI and Physical examination findings(Hug-up test, Drop arm sign, Jobe test, External rotation lag test and Hawkins test). These factors were analyzed using univariate and multivariate analyses. A weighted scoring system was developed based on the odds ratios (OR) from the multivariate model. Model performance was assessed using the area under the receiver operating characteristic curve (AUC).</p> Results <p>Multivariate analysis identified eight independent risk factors of posterosuperior rotator cuff tear (RCT-PT): age (<i>p</i> &lt; 0.01, OR = 1.090), symptom duration (<i>p</i> = 0.012, OR = 1.036), fatty infiltration grade (<i>p</i> = 0.047, OR = 2.252), critical shoulder angle (<i>p</i> = 0.028, OR = 1.175), acromial index (<i>p</i> = 0.034, OR = 1.068), supraspinatus occupation ratio (<i>p</i> &lt; 0.01, OR = 0.880), and physical examination findings including the Hug-up test (<i>p</i> &lt; 0.01, OR = 11.061), Drop arm sign (<i>p</i> = 0.036, OR = 3.124), and External Lag test (<i>p</i> &lt; 0.01, OR = 4.558). Subsequently, a 12-point scoring system was developed. The score demonstrated excellent discriminatory ability with an AUC of 0.930. A cut-off score of 6.5 yielded a sensitivity of 86.1% and specificity of 86.4% for predicting RCT-PT.</p> Conclusion <p>This CT-based scoring system, integrating morphological parameters with clinical factors, provides a useful tool for risk stratification of posterosuperior rotator cuff tears. It offers a complementary decision-support aid for clinicians when MRI is not possible, such as in pre-operative planning for shoulder arthroplasty, helping to identify patients who may warrant more definitive investigation or influence surgical strategy.</p>