20 18 Examination of Orthopedic Surgery Related Professional Knowledge for Surgeons (1)
Shoulder joint examination
Anatomy of shoulder joint
1 connector
The shoulder joint includes three anatomical joints and two physiological joints.
Anatomical joints include:
① glenohumeral joint: ball-and-socket joint. Consists of humeral head and glenoid. There is a glenoid lip around the glenoid. The glenoid lip is fibrocartilage with triangular cross section, which is divided into three layers. The outer two layers play a buffering role, and the inner layer is the most important, which can increase the stability of the joint. The glenoid joint forms a joint with 30% of the humeral head surface. Because of the existence of the glenoid lip, the glenoid fossa deepened by 2.5mm and the contact surface of glenohumeral joint reached 75%. The center of humeral head cartilage is thicker, while the periphery of glenoid is thicker. Peripheral muscles, especially rotator cuff, provide dynamic stability, while joint capsule and ligament provide static stability. In addition, the negative pressure in the joint and the limited volume of the joint (20ml, 18-52ml) also enhance the stability of the joint.
The glenohumeral joint capsule is a complex structure, which is the main static stable structure of the joint, and can bear the maximum tension of 2000 N. The joint capsule is mainly composed of type I collagen and a small amount of type III and IV collagen. It consists of three layers: outer layer, middle layer and inner layer. The inner layer is the thickest and the outer layer is thin. The posterior joint capsule is thin, without thickening area, but reinforced by muscle tissue. The anterior articular capsule is locally thickened, forming the superior, middle and inferior ligaments of glenohumeral. The glenohumeral ligament can only be seen from the inside of the joint. It starts from the upper lip of glenohumeral in front of the tendon of biceps brachii and ends in the depression above the humeral tubercle. Most of them run in front of the biceps brachii tendon, and 20% cross under the biceps brachii tendon, forming a part of the tendon sheath of the biceps brachii tendon. Its main function is to limit the downward movement of the humeral head, and also to a little limit the outward rotation and backward movement. The middle glenohumeral ligament is a wide fan-shaped structure, which is about 2cm long and 3-4mm wide. It starts below the starting point of the upper glenohumeral ligament, above the middle and lower 1/3 intersection point of the anterior edge of the glenohumeral and ends at the inner edge of the tubercle. 9% is a bundle, which extends to the anterior superior glenoid lip and ends at the glenoid lip at the root of the tendon of biceps brachii, and is called Bufford complex. It is usually closely combined with the deep surface of subscapular tendon, and has the function of limiting external rotation and downward and forward movement of humeral head when the shoulder joint is less than 90 abduction. The inferior glenohumeral ligament starts from the anterior and posterior glenoid lips, glenoid neck and glenoid margin, and ends below the articular surface of humeral head. It is divided into anterior bundle, posterior bundle and axillary bundle, which is the strongest of the three ligaments. The toe-in prevents the humeral head from moving forward when the shoulder joint rotates outward, and the toe-in prevents the humeral head from moving backward when the shoulder joint rotates inward. The upper joint capsule is reinforced by coracoclavicular ligament and joint capsule, which can limit the downward and backward movement of humeral head. The anterior inferior articular capsule is the weakest at about 4 o'clock, so dislocation often occurs here.
② Acromioclavicular joint: it is a plane joint connecting clavicle and scapula. Few people have coracoclavicular joints. The surface of the joint is hyaline cartilage. There are anatomical differences in joints. 49% of the clavicle crosses the acromion, 3% of the acromion crosses the clavicle, and only 27% of the clavicle is in the same plane. There is a cartilage disc in the joint, which fills the joint, increases the range of motion of the humerus, and is also easy to degenerate, causing osteoarthropathy. The peripheral ligaments are acromioclavicular ligament, inferior ligament, anterior and posterior ligament and coracoclavicular ligament, which are strengthened by deltoid muscle and trapezius muscle. When acromioclavicular ligament and joint capsule are cut off, the joint will be dislocated backwards by 50%, and when the muscle stop and joint capsule are cut off, the joint will be completely dislocated backwards and subluxated upwards. Coracoclavicular ligament also includes lateral trapezius ligament and medial conus ligament to prevent distal clavicle from displacement, especially upward dislocation. Among them, the conus ligament plays a major role in preventing the rotation and displacement of the clavicle, while the oblique ligament plays a minor role in preventing the joint from moving to the acromion axis. According to the indirect angle between acromioclavicular joint and clavicle, acromioclavicular joint can be divided into three types: type I joint angle is relatively vertical, type III joint angle is relatively parallel, and type II is in between. Type I is more prone to degeneration. The mobility of acromioclavicular joint is very small, and fixing this joint has little effect on shoulder joint activity.
③ Thoracoclavicular joint: the only joint connecting the shoulder and the spine, and there is also a joint disc. It is reinforced by anterior and posterior sternoclavicular ligaments and interlocking ligaments. The anterior sternoclavicular ligament is the strongest, and it is reinforced by sternocleidomastoid muscle tendon to maintain forward stability. The upper joint capsule and interlocking ligament prevent the joint from dislocating upwards and the distal clavicle from moving downwards. Costoclavicular ligament is also an important structure to maintain the stability of sternoclavicular joint, which is divided into anterior bundle and posterior bundle. The front bundle goes from the lower medial side to the upper lateral side to prevent the clavicle from supination and outward movement, and the rear bundle goes from the lower lateral side to the upper medial side to prevent the clavicle from supination and inward movement. When you lift your shoulders, lift your joints 30 times? -35? Move back and forth about 35? , longitudinal rotation about 45? -50? . If the joint is fixed, the shoulder abduction can only reach 90? .