Classification and Clinical Significance of Acromial Spur in Rotator Cuff Tear: Heel-type Spur and Rotator Cuff Tear

Acromial spurs reportedly relate to the impingement syndrome and rotator cuff tears. We classified the morphologic characteristics of the acromion (shape and thickness) and acromial spurs and determined whether they correlated with rotator cuff tears. We measured acromial shape and thickness using simple radiography and MR arthrography or CT arthrography in 106 patients with full-thickness rotator cuff tears and in 102 patients without tears. Acromial spurs could be classified morphologically into six types: heel, lateral/anterior traction, lateral/anterior bird beak, and medial. We found acromial spurs in 142 of the 208 patients (68%), and their incidence increased with age. The acromial spur was more common in the cuff tear group. The heel type was most common and detected in 59 patients (56%) in the cuff tear group and in 36 patients (35%) in the control group. The flat acromion was more common (60%) than curved and hooked acromion; however, there was no major difference between acromial shape and cuff tear. The mean acromial thickness was 8.0 mm, and the cuff tear group had thicker acromion. These data suggest acromial spurs can be classified according to the distinct morphology, and the most common heel-type spur might be a risk factor for full-thickness rotator cuff tears.