Abstract
The purpose of this study was to analyze the component motions of the acromioclavicular and sternoclavicular joint capsules in the horizontal plane, using MRI in the human body without the involvement. The subjects were 13 healthy women (mean age, 20.8 years). The task was following three kinds. Task (1): 90° flexion position of the right shoulder joint with the right cubital joint flexed at 90° in a supine position; task (2): most anterior protrusion position of the right shoulder girdle from that in task (1); and task (3): horizontal and flexion positions of the right shoulder joint from that in task (2). By results, in task (2), movement of the sternoclavicular joint became more important than the acromioclavicular joint. The clavicular and sternal epiphyses induced ventral rolling and sliding motions to the sternoclavicular joint according to the concave rule. The acromioclavicular joint produced sliding to a little ventral aspect of the medial margin of the acromion. In task (3), movement of the acromioclavicular joint became more important than the sternoclavicular joint, the medial margin of the acromion induced ventromedial rolling and sliding motions according to the concave rule to the acromioclavicular joint. From this results, degree of the component motions of the acromioclavicular and sternoclavicular joint capsules in the horizontal plane was clarified in vivo.
