Anatomy of the superior glenoid rim. Repair of superior labral anterior to posterior tears.

BACKGROUND Successful placement of a fixation device on the superior glenoid rim during superior labrum repairs requires accurate knowledge of the glenoid rim anatomy. PURPOSE To investigate the normal bony anatomy of the superior glenoid rim. STUDY DESIGN Descriptive anatomic study. METHODS Twenty cadaveric glenoid specimens were scanned to obtain cross-sectional images with peripheral quantitative computed tomography in three different positions, each perpendicular to the articular surface. Two straight lines were drawn along the interior bony margins of the articular surface and cortex, and image analysis software was used to calculate the angle between these lines. Three bony angles were measured. RESULTS The bony angles from the 10:30-, 12-, and 1:30-o'clock cross-sections were 55 degrees +/- 5 degrees, 64 degrees +/- 5 degrees, and 62 degrees +/- 8 degrees, respectively. The posterosuperior angle (at the 10:30-o'clock position) was statistically significantly lower than the superior and anterosuperior angles. Intraobserver variation was less than 3%. CONCLUSIONS The most superior point of the glenoid rim (12-o'clock position) seems to provide the most bone stock for anchor insertion. The available bone support was found to decrease posteriorly on the glenoid rim. CLINICAL RELEVANCE During superior labral repairs, the anchor or fixation device should be inserted at approximately a 30 degrees angle in relation to the articular surface for maximal bone support.