- 肩関節 (ISSN:09104461)
- vol.15, no.1, pp.13-17, 1991-09-01 (Released:2012-11-20)
The shoulder joint is the most mobile joint in the body combined with a small glenoid and a large humeral head. This joint has been thought to be an unstable joint because of its anatomical structure and the recurrence rate from initial dislocations. Our opinion of this joint is that it has most distinguished stabilizing mechanisms for keeping a wide range of motion.1. The first stabilizing mechanismThis mechanism is the bony combination of the radius between the glenoid cavity and the humeral head. The anatomical study showed the radius of a cross section of the glenoid was 16.8 mm and of the humeral head 22 mm. The computation of the maximum permissible kinetic vector that enables the humeral head to be on the glenoid was 43°.2. The second stabilizing mechanismThe second mechanism is the function of the anterior capsule including the inferior glenohumeral ligament.The anterior capsule works involuntary in both its tension and direction as the centripetal force does against the shear force.3. The disadvantages of these two stabilizing mechanismsThe disadvantages of these two stabilizing mechanisms are; - Inefficiency against the increased anterior kinetic vector during the positioning of the upper extremities vertically against the glenoid- The decrease of bony structural intensity compared with other joints such as the hip joint.4. The third stabilizing mechanismThe third stabildzing mechanism is the function of the shoulder girdle.Its first function is the mobility of the scapula working as shock ab s orber against the share force that falls on the glenohumeral joint.The second is the function of the shoulder girdle muscles such as the pectoralis major and the deltoid.In conclusion, therefore, a normal shoulder joint should be the most distinguished joint with these stabilizing mechanisms physically and anatomically maintaining a wide range of motion.