Location of the Glenoid Defect in Shoulders with Recurrent Anterior Dislocation

BACKGROUND: In patients with recurrent anterior dislocations of the shoulder, it is well known that the glenoid rim is often deficient (8%-95%). However, little is known regarding the precise location of the bony defect of the glenoid. HYPOTHESIS: The bony defect is anterior rather than anteroinferior to the glenoid. STUDY DESIGN: Cohort study (symptom prevalence); Level of evidence, 2. METHODS: The authors studied 3-dimensional images of the glenoid reconstructed from computed tomography to determine the location of the glenoid defect in 123 shoulders of 123 patients with recurrent anterior dislocations of the shoulder. They measured the location, extent, and orientation of the defect based on the clock face of the glenoid. RESULTS: The defects were located between 12:08 and 6:32, with the range between 2:30 and 4:20 being the most frequent. The extent of the glenoid defect was 106.7 degrees +/- 27.1 degrees (mean +/- standard deviation). The mean orientation of the defect was pointing toward 3:01 on the clock face of the glenoid, at a mean angle of 90.5 degrees +/- 10.4 degrees from the 12-o'clock direction. CONCLUSION: The glenoid defect is located almost anterior to the glenoid.