Glenoid Version Measurement when the Medial Scapula Is Not in the Cross-Sectional Imaging Field of View

Introduction: Glenoid version, glenoid surface orientation in the axial plane, has an important role in the passive stabilization of the articular components of the glenohumeral joint. Glenoid shape and version has been associated with glenohumeral instability, arthritis, and rotator cuff tears. Cross-sectional computed tomography (CT) and magnetic resonance (MR) imaging have been demonstrated to be more accurate than radiography for measuring glenoid version. Glenoid version calculation requires a transverse scapular axis, often defined as a line connecting the glenoid fossa midpoint with the scapular spine medial endpoint. Other transverse axis definitions include a line perpendicular to the glenoid surface midpoint or a line tangent to either the posterior or anterior glenoid rim. Prior studies require identification of scapula's medial border to measure glenoid version. Clinical shoulder joint crosssectional imaging frequently uses a reduced field of view (FOV) without visualizing scapula's medial border. Thus preventing replication of the published methods. No method is currently available to measure glenoid version in routine shoulder cross-sectional imaging studies where the medial scapular border is not in the FOV. The purpose of this study was to design and validate a method to accurately measure glenoid version on cross sectional clinical CT shoulder images, where the FOV does not include the entire scapula.