Quantitative assessment of classic anteroinferior bony Bankart lesions by radiography and computed tomography

Background: An anteroinferior osseous defect of the glenoid rim is sometimes encountered in patients with recurrent anterior dislocations of the shoulder. A defect of more than 21% of the glenoid length is reported to cause instability after Bankart repair. Hypothesis: We can estimate the critical size of glenoid defects by using radiography or computed tomography. Study Design: A controlled laboratory study. Methods: Osseous defects of 0%, 9%, 21%, 34%, and 46% of the glenoid length were created stepwise in 12 cadaveric scapulae, and plain radiographs simulating the axillary and West Point views and computed tomographic images were obtained. The maximum width of the remnant glenoid was measured under each condition and expressed as a percentage of the width of the intact glenoid. Results: A 21% defect appeared to be 18.6% of the intact glenoid on the West Point view. With computed tomography, a 21% defect resulted in loss of 50% of the width on a single slice across the lower one-fourth of the glenoid. Conclusions: We can estimate the size of a glenoid defect by using the West Point radiographic view or computed tomogram. Clinical Relevance: These images gave decisive information as to whether an osseous glenoid defect required bone grafting to achieve stability after Bankart repair.