The shoulder joint is the most mobile joint in the human body, and it is also the joint where most dislocations occur, accounting for 50% of human dislocations. Shoulder instability is mostly caused by post-traumatic dislocation, which means that the humeral head cannot be kept in the center of the shoulder pelvis, and its incidence is about 2% in the population.
I. Etiology of shoulder dislocation
Shoulder dislocation is generally referred to as shoulder instability in clinical practice. The scholar Bankart first used the term shoulder instability in 1923 and first described the phenomenon of glenoid labrum or joint capsule tearing off from the glenoid rim after recurrent shoulder dislocation, injury. Traditionally, shoulder instability only indicated anterior or posterior dislocation. With advances in clinical and basic research in shoulder surgery, the definition of SI was extended to include unidirectional or multidirectional dislocations and subluxations to the anterior, anterior-inferior, inferior, posterior-inferior, posterior, and anteroposterior caused by trauma or nontrauma.
There are four causes of shoulder instability as follows.
1.Traumatic: greater violence, causing dislocation or subluxation of the joint.
2. Repeated shoulder strain or improper exertion. For example, participation or engagement in sports with large range of shoulder motion such as water sports, tennis, badminton, and certain occupational factors.
3.No obvious cause: About 4% of shoulder instability is caused by extensive relaxation of the joint capsule, and there is no clear history of trauma.
4. In the “mental” type of shoulder instability, the patient consciously dislocates the joint to attract the attention of others, so attention should be paid to the mental status of these patients.
2. Diagnosis of shoulder dislocation
1. Medical history and physical examination: 90% of SI can be diagnosed by medical history and physical examination. Recurrent SI often has a history of post-traumatic dislocation or subluxation, or a history of repeated activity of the upper arm over the head. 50% or more have multi-directional instability with a history of excessive activity of other joints. The main symptoms are shoulder pain, easy fatigue, radiating numbness and tingling in the upper arm.
tingling. The shoulder “slides in and out” unstable feeling, sometimes only manifested as “shoulder impingement syndrome”.
2.Body examination under anesthesia: It is considered to be the most effective non-invasive examination method. It is suitable for people with well-developed muscles and typical symptoms, but the diagnosis cannot be confirmed by physical examination and X-ray.
3.X-ray examination: It is a routine examination method. Multi-angle radiographs can be performed for a definite diagnosis.
4.Shoulder arthrography: It has some significance in diagnosing shoulder capsule, glenoid labrum and rotator cuff injury. At present, air and contrast agent are often used to do double contrast imaging.
5.CT and CTA: CT can clearly show Hill-Sachs injury, glenoid margin osteochondral lesions and intra-articular free bodies. It is especially superior to plain X-rays for the identification of tilted glenoid or humeral head deformity and glenoid head size ratio.
6.MRI: In recent years, MRI has become increasingly important in the diagnosis of SI and rotator cuff injuries. It can show glenoid labral tear, joint capsule avulsion from the glenoid, glenohumeral ligament tear, subscapularis atrophy and rotator cuff tear, in which MRI is superior to arthrography, CT and CTA.
7.Shoulder arthroscopy: It can directly observe the pathological changes and dislocation direction in SI joint, which is beneficial to the surgical approach and method selection. Combined with physical examination under anesthesia, it has some diagnostic value for SI with mild lesions and difficult to diagnose. Microscopically, a marginal or “barrel stem” tear of the glenoid labrum can be seen. The cartilaginous surface of the humeral head is eroded and damaged posteriorly and superiorly. Free bodies in the joint cavity and bone spur formation on the anterior inferior border of the glenoid. Relaxation, tearing or scarring of the joint capsule, enlargement of the subscapularis or axillary fossa. The supraspinatus and infraspinatus muscles are torn and degenerated, while the subscapularis lesion is difficult to show microscopically. In addition, arthroscopy can simultaneously remove the free body in the joint cavity and directly repair the damaged glenoid labrum, joint capsule and AIGHL.
C. Treatment of shoulder dislocation
1.Conservative treatment is mainly to enhance the muscle strength exercise of deltoid, rotator cuff and scapular band muscles, which has good effect on casual SI, PSI and MDI. The excellent rate of treating non-traumatic subluxation is 80%, while the excellent rate of treating traumatic subluxation is only 16%.
2.Open surgery: There are more than 150 surgical methods, each of which has certain complications. At present, it is not recommended to cut the subscapularis tendon, but to split it horizontally from the middle and lower 1/4 to reveal the joint capsule, and then to cut the joint capsule in a “T” shape.
Shoulder arthroscopy: Arthroscopic repair of glenoid labrum, joint capsule, and glenohumeral ligament injuries has become the preferred method for treating ASI. Nowadays, arthroscopic repair of glenoid labrum injury tends to use absorbable materials instead of metal materials such as screws and “U” shaped nails. The latter has complications such as loosening, displacement and fracture, thus the recurrence rate after surgery is high, while the recurrence rate after surgery using absorbable materials is only 10%.
4. Rehabilitation: Active or passive postoperative rehabilitation of the periapical muscles is an important step in maintaining the surgical effect. The strengthening of the deltoid, rotator cuff muscles and biceps and triceps muscles is important in maintaining the stability of the glenohumeral joint.