Glenoid inclination is associated with full-thickness rotator cuff tears

Anatomic factors, such as a hooked acromion, have been associated with rotator cuff disorders. Orientation of the glenoid relative to the scapula has been implicated in shoulder instability, but it has not been linked to rotator cuff disorders. The purpose of the current study was to test the hypothesis that superior inclination of the glenoid is associated with full-thickness rotator cuff tears. Glenoid inclination angles were measured from 16 shoulder radiographs of a convenience sample of eight cadavers in which one shoulder had an intact rotator cuff and the other shoulder had a full-thickness rotator cuff tear. Glenoid inclination angles for shoulders with rotator cuff tears were compared with contralateral normal shoulders using nonparametric statistical analysis. The glenoid inclination angle was greater in cadaver shoulders having full-thickness rotator cuff tears (98.6degrees) than in shoulders without tears (91.0degrees). A second experiment was done to assess the reliability of using 34 Grashey view radiographs from a clinical population to measure glenoid inclination angle. A method to measure the glenoid inclination on Grashey views was tested and was found to correlate with the inclination angles measured on cadaveric scapulae. Intrarater reliability of measurements from clinical Grashey views was 0.93, and interrater reliability was at least 0.88.