Background: In osteoarthritis of the shoulder, the tilt of the glenoid surface undergoes an eccentric deformation not only in the anteroposterior but also in the superoinferior direction. The goals of this study were to analyze glenoid version in the coronal plane and to clarify the relationship between retroversion and inferior inclination of the glenoid.

Methods: Standardized radiographs of 100 consecutive patients with primary osteoarthritis of the shoulder and 100 otherwise healthy patients with shoulder pain (the control group) were included in this study and were analyzed by two independent observers.

Results: We defined four different types of inclination deformity of the glenoid. In a type-0 glenoid, a line at the base of the coracoid process and a line at the glenoid rim run parallel. Both lines intersect below the inferior glenoid rim in a type-1 glenoid. In a type-2 glenoid, the line at the base of the coracoid process and the glenoid line intersect between the inferior glenoid rim and the center of the glenoid. In a type-3 glenoid, the lines intersect above the base of the coracoid process. A significant difference (p < 0.0001) in the distribution of glenoid types between the two patient groups was observed. Forty-seven patients with osteoarthritis showed combined posterior and inferior glenoid wear. We found no correlation between the type of inclination and the type of glenoid morphology. The interobserver reliability of our observations was very high.

Conclusions: In osteoarthritis, eccentric inferior glenoid wear is frequent and independent from retroversion deformity of the glenoid. Normalization of glenoid version in both transverse and coronal planes may reduce eccentric loading of the prosthetic glenoid, which has been associated with loosening.

Clinical Relevance: This radiographic classification system can facilitate the decision-making process to normalize glenoid inclination during glenoid replacement.