A 3D-CT scan study of the humeral and glenoid planes in 150 normal shoulders

The purpose of the study was to determine the normal three-dimensional relationship between the humeral and the glenoid plane of the individual patient. We measured the three-dimensional angle between the glenoid plane and the humeral plane (glenohumeral angle, A degrees GH) and the angle between the plane of the scapula and the plane of the glenoid (glenoscapular angle, A degrees GS) with the patient in a standardized position to the CT scan gantry. We hypothesized that a normal distribution with a small variation would exist for both angles. A total of 150 conventional CT scans of normal shoulders from patients aged between 18 and 80 years were examined and three-dimensional reconstructions were derived from it. The descriptive statistics and the variability of A degrees GH and A degrees GS were determined. The mean A degrees GH was 57.9A degrees, and the mean A degrees GS was -3.77A degrees. The overall reliability of the measurement was good. Descriptive statistics of this study confirm the normal distribution and a narrow variation of both parameters. This is the first study to determine the normal 3D relationship between the humerus and the glenoid (A degrees GH). This new three-dimensional anatomical information of the normal glenohumeral relationship and glenoid can be used to distinguish normal from pathological anatomy, as well as alternative surgical guidance especially in bony deficient glenoids