Localized glenoid hypoplasia. An anatomic variation of possible clinical significance.

Examinations were done on 1150 scapular bone specimens from museum collections. A localized hypoplasia of the posteroinferior glenoid was found in significant numbers (20%-35%) depending on the population group studied. Criteria were established for the identification of this variant in computed tomography and magnetic resonance studies. Localized hypoplasia of the posteroinferior glenoid was detected as an incidental finding in 54 (18%) of 300 such studies. Using these same imaging criteria in a prospective manner, 9 of 12 patients seen for voluntary multidirectional instability of the shoulder displayed a localized posteroinferior glenoid hypoplasia. This phenomenon also may add to the picture of extreme posterior glenoid wear that sometimes is seen in association with osteoarthritis of the shoulder.