Abstract
In order to figure out motion mechanism of human shoulder joint, we have been analyzing in-vivo shoulder movements, particularly humeral elevation within the scapular plane, using open-MR imaging and 3D/3D-registration technique. In this paper, we applied this method to analyze the clavicle motion relative to the chest. To do so, we have to establish the cheat coordinate system having high reproducibility using 3D MR imagines of the chest. Then we manually extracted the apexes of six ribs connected to the sternum and set the sternum coordinate system denoted as ΣST using these apex points. We evaluated reproducibility of ΣST in the following two respects: 1) the variation of six apex points extracted by five different testers from the same MR images; 2) the variation of the extracted apex points as well as ΣST in different humeral elevation angles. Consequently, the apex points as well as ΣST had a high reproducibility in a level of the slice interval of MR imaging in both the same images and the different images, demonstrating the applicability of ΣST to the clavicle motion analysis. Using this coordinate system, we tried to analyze the clavicle motion of four different subjects. The results agreed well with its previous reports in both respects of the direction and range of the clavicle motion.
