抄録
In 1986, Bigliani et al. classified acromial shape: type I (flat) 18.6%, type II (curved) 42%, type III (hooked) 38.6%, and found 66% type III acromions among cadavers with rotator cuff tears. The majority of studies have confirmed this correlation. The relation between age and acromial types have been also investigated, however the acromial types in children was not investigated in most reports. Thus, the classification is performed after the developments have finished and ossifications have been completed. Therefore, there is no report about the cartilaginous acromions as the mold of ossification in live shoulders. The purpose of this study was to clarify the morphology of cartilaginous acromions. Seventy-eight persons (156 shoulders, 8-12 years old) were studied. Because the acromions consist of cartilage, the undersurface of acromion can be depicted when the probe of ultrasound machine (Xario, Toshiba, Japan) attached parallel to the lateral edge of acromions. We classified these cartilaginous acromions into Bigliani classification by using the quantitative classification method (Getz et al., Radiology, 1996). The distribution of acromial types was as follows: type I (flat) 22%, type II (curved) 78%, type III (hooked) 0%. We did not find Type IV (convex) acromion which Gagey reported (Surg Radiol Anat, 1993). There were little Type III acromions in the cartilaginous stage. Type III acromion may be formed by the traction of coracoacromial ligament, because there are many reports that the older have more Type III acromion and that enthesophytes are more common in type III acromions.
