Acromial roof in patients with concentric osteoarthritis and massive rotator cuff tears: multiplanar analysis of 115 computed tomography scans

Background: There is evidence for differences of scapular shape between shoulders with rotator cuff tears (RCT) and osteoarthritic shoulders (OA). This study analyzed orientation and shape of the acromion in patients with massive RCT and concentric OA (COA) in a multiplanar computed tomography (CT) analysis. Methods: CT scans of 70 shoulders with degenerative RCT and 45 shoulders with COA undergoing primary shoulder arthroplasty were analyzed. The 2 groups were compared in relation of (1) shape of the acromion, (2) its orientation in space, and (3) the anteroposterior glenoid coverage in relation to the scapular plane. Results: Lateral acromial roof extension was an average of 4.6 mm wider and the acromial area was an ivcrage of 156 min(2) larger in RCT than in COA < .001). Significant. differences of the lateral extension of the acromion margin were limited to the anterior two-thirds. Acromial roof orientation in RCT was average of 10.8 degrees more "externally rotated" (axial plane: P < .001) and an average of 7.8 degrees more tilted downward (coronal plane: P < .001) than in COA. The glenoid in RCT was an average of 5.5 degrees (P < .001) more covered posteriorly compared with COA. Conclusions: A more externally rotated (axial plane), more downward tilted (coronal plane), and wider posterior covering acromion was more frequent in patients with massive RCT than COA. (C) 2018 Journal of Shoulder and Elbow Surgery Board of Trustees. All rights reserved.