Variations in glenoid rim anatomy: Implications regarding anchor insertion

Purpose: The purpose of this study was to investigate normal bony anatomy of the glenoid rim and to define the angles for successful anchor placement for anterior and posterior labral repairs. Type of Study: An anatomic study using cadaveric shoulder specimens. Methods: Soft tissue was dissected from 20 cadaveric shoulders, and the glenoids were isolated. The glenoid specimens were scanned to obtain cross-sectional images using peripheral quantitative computed tomography (pQCT) in 4 different planes. Glenoid rim angles were measured from the cross-sectional pQCT images of the glenoids at 5 positions: the 3-o'clock, 4:30-, 6-, 7:30-, and 9-o'clock positions. Glenoid morphology was noted for each position. Results: The glenoid rim angles from the 3-o'clock to the 9-o'clock positions were 53degrees +/- 5degrees, 45degrees +/- 7degrees, 80degrees +/- 10degrees, 61degrees +/- 10degrees, 49degrees +/- 4degrees, respectively. Asymmetric morphology of the glenoid was noted with an almost straight line extending medially from the rim at the 3-o'clock position, whereas a concave morphology was noted at the 9-o'clock position. Similarly at the 4:30-o'clock position, the scapular bony surface did not curve toward the base as markedly as it did at the corresponding posterior 7:30-o'clock position. Conclusions: The available bone mass for the anchor insertion was found to vary depending on the position of the glenoid rim. Both rim angle and glenoid morphology for each position must be considered when selecting the ideal anchor insertion angle for labral repair.