Anterior shoulder dislocation: quantification of glenoid bone loss with CT.

Abstract

In recurrent anterior shoulder dislocation, glenoid bone loss may predispose the patient to further dislocation and failure of a Bankart repair. This study investigates the quantification of glenoid bone loss in anterior shoulder dislocation using CT. CT examinations were performed on 40 patients (average age, 31 years; range, 13-82 years), comprising 46 shoulders with anterior dislocation and 34 contralateral normal shoulders. Twenty shoulders in 10 healthy subjects were also examined. Both shoulders were examined simultaneously. Image reconstruction included oblique sagittal reformatted images en face to the glenoid fossa. Seven aspects of glenoid fossa shape and size were measured, including the cross-sectional area, maximum width, maximum height, and flattening of the anterior glenoid curvature. Variable flattening of the anterior glenoid curvature was a feature in 42 (91%) of 46 dislocated shoulders although it was seen in only two (4%) of 54 normal shoulders. Anterior glenoid flattening increased exponentially with an increasing number of dislocations. Anterior glenoid flattening, decreased maximum glenoid width, and decreased maximum width-to-length ratio were the most useful measures of bone loss. Maximum glenoid width was smaller than on the contralateral side in 79% of patients with unilateral dislocation by an average of 3.0 mm (range, 0.1-10 mm) or 10.8% (range, 0.4-32%). Glenoid cross-sectional area was a less useful measure of glenoid bone loss. Flattening of the anterior glenoid curvature is shown in most patients with anterior dislocation. In unilateral dislocation, a comparison of maximum glenoid width with that on the contralateral side was the best discriminator of moderate to severe glenoid bone loss.