Os acromiale: frequency and a review of 726 shoulder MRI.

Os acromiale consist in a lack of fusion between the different ossification spots of the acromial side of scapula from the age of 23-25 years. A relation between os acromiale and some shoulder pathology like impingement syndrome, cuff tear and subacromial bursitis has been described. The etiology is not already known. The aim of this study was to evaluate the frequency of os acromiale in our population, the link between os acromiale and sex, side and shoulder pathology. 1042 shoulder MRI were evaluated to find out os acromiale and the linked cuff pathology. In our population, the frequency of os acromiale was 3.44% without differences between sexes, with prevalence on the right shoulder. No differences in cuff and bursa pathology were present between affected and unaffected subjects. Os acromiale is an anomaly still underdiagnosed. It is important to be recognized because it allows to make an accurate pre-surgical plan. To make a correct diagnosis, axial MRI cut or TC is necessary.