抄録
The unstable shoulder is difficult in making a proper diagnosis. Because the objective findings are not clear always on the clinical signs, X-ray appearance and other examination. In order to make diagnosis easier, we divided the'unstable shoulders into two major groups in the pathogenesis (Fig.1). One is the anatomical instability and the other is the functional (3)(6). In the anatomical instability, displacement of the glenohumeral joint can be demonstrable clinically, on the other hand, in the functional instability it cannot be shown clinically although severe shoulder disability is found when the shoulder joint is forced into the definite position such as abduction with external rotation(4)(8). There are many reports on the factors stabilizing the glenohumeral joint, for examples, abnormalities of the subscapular muscles (10), the glenoid labral lesion(3), the capsular elongat1on(5) and the bony defect of the humeral head or the gleno1d. The subscapular deficiency will be excluded in this paper, because it is difficult to show any objective findings of the subscapular muscle before surgery. This factor is still not comprehensive. The glenohumeral joint will be displaced objectively due to the capsular elongation at the stress position, showing the anatomical instability. The glenoid labral lesion including the partial detachment of the capsule will produce severe pain at the forced position, but it will not show the objective displacement of the glenohumeral joint, which is the functional instability.
