A Novel Tabletop Plane-Based Scapular Coordinate System Improves the Reproducibility of Preoperative Three-Dimensional Measurements in Reverse Total Shoulder Arthroplasty

Background/Objectives: Accurate three-dimensional (3D) assessment of glenoid morphology depends on the coordinate system used for measurement. Conventional landmark-based coordinate systems may be affected by observer-dependent variability in identifying the scapular landmarks. This study aimed to compare the reproducibility of a novel anterior scapular plane (ASP) coordinate system with that of the conventional surgical scapular plane (SSP).

Methods

Twenty-five shoulders undergoing primary reverse total shoulder arthroplasty were evaluated using preoperative computed tomography scans. Glenoid version (GV), glenoid inclination (GI), glenoid height (GH), glenoid width (GW), and global offset (GO) were measured using both coordinate systems. Two fellowship-trained shoulder surgeons independently performed all measurements twice at a 1-month interval. Intra- and inter-observer reliability were assessed using intraclass correlation coefficients (ICCs).