COMPARISON of SCAPULAR MORPHOLOGY in DEGENERATIVE and TRAUMATIC ROTATOR CUFF TEARS

Background: Degenerative cuff tears have impingement pathophysiology due to altered scapular morphology as measured by increased critical shoulder angle (CSA), decreased lateral acromial angle (LAA) and increased acromion index (AI). But scapular morphology in traumatic tears has neither been studied nor compared with degenerative tears. Aim: To compare scapular morphology with CSA, LAA, AI between traumatic and degenerative tears and determine their reliability. Methods: This observational study includes 100 patients (50 with traumatic and degenerative tears). We analyzed MRI and standardized AP shoulder radiograph of these patients. Parameters, such as CSA, LAA, AI, were measured on AP radiographs by two separate observers in a blinded manner. The 1st observer repeated measurements after four weeks. We compared age, gender, degree of cuff tear, and CSA values, LAA, and AI between the two groups. Results: On comparison using chi-square test, degenerative group had significantly higher age, higher CSA (mean 37.55, SD 0.88 versus traumatic group mean 36.6, SD 0.95, p-value<0.001, highly significant), higher AI (mean 0.73, SD 0.02 versus traumatic mean 0.69, SD 0.04 p-value<0.001, highly significant), and lower LAA (77.14, SD 2.03 versus traumatic mean 78.36, SD 2.73, p-value 0.013, significant). Interobserver and intraobserver reliability of parameters using the intraclass correlation coefficient (ICC) revealed excellent (CSA, LAA) and good (AI) agreement. ROC curve analysis calculated sensitivity (0.7) and specificity (0.66) to diagnose degenerative tear for CSA above 37.05′. Conclusion: Scapular morphology in traumatic tears differs from degenerative. CSA, LAA, AI can be reliably measured on standardized shoulder AP radiographs.