Variability of measurement of glenoid version on computed tomography scan.

The purpose of the study was to determine the variability of measurement that might occur with rotation of the scapula in the coronal plane when computed tomography scanning is used. Ten dry scapula specimens had 4 sets of computed tomography scans performed at +20 degrees, +10 degrees, neutral, and -10 degrees of scapula rotation. The angle of glenoid version was then measured according to the technique of Friedman. The measured value for glenoid version was noted to vary by as much as 10 degrees on the same specimen with minor rotation of the scapula. This result occurred because of differences in the curvature of the vertebral border of the scapula. The measured angle of glenoid version was most likely to vary with rotation of the scapula 10 degrees downward (i.e., glenoid articular surface facing 10 degrees upward). For accurate and reproducible measurement of the glenoid version, it is essential that in the scout view the glenoid orientation is neutral (i.e., glenoid surface is perpendicular to the plane of the computed tomography cut).