Magnetic resonance imaging of the glenoid labrum in anterior shoulder instability.

Detachment of the anterior inferior labrum and inferior glenohumeral ligament complex from the glenoid is a common lesion encountered in anterior shoulder instability while other types of labral lesions are associated with symptoms that mimic instability. Accurate delineation of labral lesion is, therefore, key in managing shoulder problems. In a prospective double-blinded fashion, we compared the magnetic resonance imaging findings with those noted at surgery in 33 patients with possible anterior shoulder instability. Of 28 surgically confirmed labral lesions, 21 were detected by imaging. Sensitivity was 75%, specificity 100%, while positive and negative predictive values were 100% and 41%, respectively. Overall accuracy was 79%. Based on a literature review and our clinical experience, we developed a classification of glenoid labra according to the type and severity of the lesions. Method of treatment correlated with clinical outcome, using this system, to a statistically significant level. Unfortunately, this system enabled accurate classification with magnetic resonance imaging in only 7 of 33 (21%) labra, with the precision necessary to affect surgical planning in our series. We conclude that magnetic resonance imaging is not useful in the surgical planning for most patients with obvious anterior shoulder instability.