Acromial morphotype in the young asymptomatic athletic shoulder.

Several studies have documented an association between the type III acromion and rotator cuff tears. However, controversy exists as to whether the shape of the acromion is an innate anatomic characteristic. The purpose of this study was to evaluate the prevalence of the type III acromion in young asymptomatic athletes. Bilateral supraspinatus outlet radiographs were obtained in 100 Division 1 collegiate athletes (average age, 19.9 years). Only 4 (2%) of 200 shoulders were found to have a type III acromion by use of the standard subjective Bigliani classification. Eight (4%) acromion were found to be type III by the use of previously published objective criteria for acromial measurement. Our results show the type III acromion to be relatively rare in asymptomatic, young athletes, but the incidence of type III acromion in a general population of both young and older individuals is still not completely understood. However, our results accentuate the possibility that the higher incidence of type III acromion seen in older populations may in fact be related to secondary acromial changes.