Os acromiale: anatomy and surgical implications.

We examined 270 scapular bones and found an incidence of os acromiale of 8.2%. In most cases, the free fragment was approximately one-third of the overall length of the acromion, and included the acromioclavicular facet and the principal areas of attachment of the coracoacromial ligament. Two-thirds of the specimens showed a distinctive pattern of osteophytic lipping. Based on this study, we devised operative procedures for symptomatic patients, and operated upon seven, with good results in six.