Morphologic study of the glenoid in primary glenohumeral osteoarthritis.

We studied the natural course and the possibility of making a prognostic classification of glenoid morphology in primary glenohumeral osteoarthritis (GHOA). For this purpose, serial computed tomography scans of 113 osteoarthritic shoulders were reviewed. The position of the humeral head with respect to the glenoid seems to be an important predictor of the glenoid morphologic evolution. Three main glenoid types were defined: Type A, Type B, Type C. Type A (59%) was marked by a well-centered humeral head and a balanced distribution of strengths against the surface of the glenoid. The symmetric erosion was explained by the absence of subluxation. In Type B (32%), the posterior subluxation of the humeral head was responsible for the asymmetric load against the glenoid and was implicated in the development of primary GHOA, particularly the exaggerated posterior wear pattern. Type C (9%) was defined by a glenoid retroversion of more than 25 degrees, regardless of erosion; retroversion was primarily of dysplastic origin and explained the early event of osteoarthritis. In primary GHOA, this classification of the glenoid can discriminate retroversion between posterior erosion and dysplasia.