Relationship between the lateral acromion angle and rotator cuff disease.

One hundred consecutive magnetic resonance imaging (MRI) studies of the shoulder obtained for the purpose of evaluating rotator cuff symptoms were retrospectively reviewed to assess the relationship between acromion morphologic appearance and rotator cuff disease. The studies were reviewed simultaneously by two authors. Each cuff was assigned a tendon grade and an overall cuff score with MRI criteria previously described in the literature. A newly described "lateral acromion angle" was measured from a specified oblique coronal cut on each MRI study and was correlated with the corresponding MRI-determined rotator cuff score and supraspinatus tendon grade. Observed correlations were analyzed by using statistical methods. The average measured lateral acromion angle was 78 degrees, with a range from 64 degrees to 99 degrees. Eight shoulders had angles less than or equal to 70 degrees, and all eight of these patients were found to have full-thickness rotator cuff tears. As the lateral acromion angle decreased, a statistically significant increase in rotator cuff disease was noted (p < 0.0001). A significant correlation between increasing age and rotator cuff disease was also observed (p < 0.0001). Multiple regression analysis confirmed that both the lateral acromion angle and the age of the patient were independent predictors of rotator cuff score. Finally, although a trend was noted suggesting a correlation between acromion type (I--flat, II--curved, and III--hooked) and MRI-determined rotator cuff disease, this trend did not reach statistical significance (p = 0.12). Surgical correlation with MRI rotator cuff findings in 35 patients showed an MRI sensitivity of 100% and specificity of 83%. A statistically significant correlation between the lateral acromion angle and MRI-determined rotator cuff disease has been noted. The described angle may be a useful adjuvant in the evaluation and management of rotator cuff disease.