This is due to the anatomical and physiological characteristics of the shoulder joint, such as a large humeral head, a shallow and small joint pelvis, a loose joint capsule, weak tissues below the front of the joint, a large range of joint movement, and more opportunities for external forces. Dislocation of the shoulder joint occurs mostly in young adults and more often in men.
I. Etiology
Shoulder dislocation is divided into anterior and posterior dislocation according to the position of the humeral head. The anterior dislocation of the shoulder joint is common and is often caused by indirect violence, such as when the upper limb is abducted and externally rotated during a fall, the palm of the hand or the elbow lands on the ground, and the external force impacts upward along the longitudinal axis of the humerus, and the humeral head tears off the joint capsule from the weak part between the subscapularis and the large garden muscle and comes out forward and downward, forming an anterior dislocation. The humeral head is pushed under the rostral process of the scapula, forming a sub rostral dislocation. If the violence is greater, the humeral head moves forward to the subclavian, forming a subclavian dislocation. Posterior dislocations are rare and are caused by anterior to posterior violence to the shoulder joint or by landing on the hand when the shoulder joint is internally rotated. Posterior dislocation can be divided into subscapularis and subacromial dislocation. If the shoulder joint dislocation is not treated properly at the initial stage, habitual dislocation may occur.
II. Clinical manifestations
1. Swelling of the injured shoulder, pain, and limitation of active and passive activities.
2. Elasticity of the affected limb is fixed in a mild external booth, often with the affected arm supported by the healthy hand, and the head and trunk are tilted to the affected side.
The shoulder deltoid is collapsed, with a square shoulder deformity. The displaced humeral head can be palpated in the axilla, under the rostral process or under the clavicle, and the joint pelvis is empty.
4. Positive shoulder hitch test, when the affected hand is leaning against the chest, the palm of the hand cannot hitch on the contralateral shoulder.
III. Examination
Posterior shoulder dislocation is often reported as negative on routine anteroposterior radiographs of the shoulder. Since subacromial dislocation is the most common, and the general position of the humeral head in relation to the glenoid and the acromion still exists in the anteroposterior radiographs, the radiographs are often negative.
However, the following abnormal features can still be found by careful reading of the films.
1, due to the forced internal rotation of the humeral head, even if the forearm is in a neutral position, the humeral neck can still be found to be “shortened” or “disappeared”, with overlapping images of large and small nodes.
2, the gap between the inner edge of the humeral head and the anterior edge of the scapular glenoid is widened, and it is usually considered that a gap greater than 6 mm is diagnosed as abnormal.
3, disappearance of the oval overlapping shadow of the normal humeral head and scapular glenoid.
4.The relationship between the humeral head and the scapular glenoid is asymmetrical, manifesting as high or low, and not parallel to the anterior edge of the glenoid.
If posterior dislocation of the shoulder joint is highly suspected, axillary film or lateral film through the chest should be taken, then the humeral head prolapse can be found on the posterior side of the scapular glenoid. If necessary, a CT scan of both shoulders can clearly show that the articular surface of the humeral head faces posteriorly and is dislocated from the posterior edge of the articular glenoid; sometimes a depressed fracture of the humeral head and a jamming with the posterior edge of the articular glenoid can be found and affect reset, or a fracture of the posterior edge of the articular glenoid.
IV. Diagnosis
1.History of trauma to the shoulder or upper limb.
2.According to the above symptoms and signs.
3.X-ray film can clarify the type of dislocation and the presence of fracture.
Differential diagnosis
This disease needs to be differentiated from frozen shoulder. Both frozen shoulder and shoulder dislocation have severe pain in the shoulder and significant limitation of shoulder joint function. However, frozen shoulder is a chronic degenerative inflammation of the soft tissues of the shoulder, with severe pain in the early stage and functional impairment in the middle and late stages. In contrast, shoulder dislocation mostly has a history of acute injury, such as pulling and punching with excessive force or sudden violence, landing on the palm and elbow during a fall, and dislodging the humeral head from the articular pelvis due to sudden violence impacting upward along the humerus.
In addition, the type of dislocation needs to be identified. After dislocation, the humeral head can be divided into 3 types according to its position.
1.Subglenoid type: the humeral head is located below the articular glenoid, and this type is rare.
2, subglottis type: the humeral head is located under the scapular gland, this is also rare.
3.Subacromial: the humeral head is still located under the acromion, but the articular surface faces backward and is located behind the scapular glenoid, which is the most common.
VI. Treatment
1.Manual reset
The dislocation should be reset as soon as possible, and appropriate anesthesia (brachial plexus anesthesia or general anesthesia) should be chosen to relax the muscles and make the reset painless. Older people or those with weak muscles can also be carried out under painkillers. Habitual dislocations can be performed without anesthesia. The repositioning technique should be gentle and violent techniques are prohibited to avoid additional injuries such as fracture or nerve damage. There are three common repositioning techniques.
(1) foot stirrup method, the patient lies on his back, the operator is located on the affected side, both hands hold the wrist of the affected limb, the heel is placed in the axilla of the affected side, both hands traction with a steady and continuous force, traction in the heel outward pushing the humeral head, while rotating, inward upper arm can be reset. A loud sound can be heard during the resetting.
(2) Koch method This method is easy to succeed under muscle relaxation, do not use excessive force to prevent the humeral neck from being subjected to excessive twisting force and fracture. Manual steps: hold the wrist with one hand, flex the elbow to 90 degrees, make the biceps muscle relax, hold the elbow with the other hand, keep traction, lightly abduct, gradually rotate the upper arm outward, then inwardly make the elbow along the chest wall near the midline, then inwardly rotate the upper arm, at this time, it can be reset. And you can hear a ringing sound.
(3) traction pushing method casualty lying on his back, an assistant with a cloth sheet over the thorax to the healthy side of the pull, the second assistant with a cloth sheet through the axilla over the affected limb to pull outward above, the third assistant holding the affected limb wrist down traction and external rotation inward, the three sides at the same time Xu Xu continuous traction. The operator pushes the humeral head outward with the hand in the axilla to return it to reset. The second person can also do traction repositioning.
After the reset, the shoulder is restored to the normal shape of blunt garden plump, axillary, sub rostral or sub clavicular and then the dislocated humeral head is not palpable, the shoulder hitch test becomes negative, and the humeral head is in the normal position on X-ray examination. If the humerus is combined with an avulsion fracture of the greater tuberosity, because there is a periosteum between the fracture fragment and the humeral stem, in most cases, the avulsion of the greater tuberosity is also reset after the shoulder dislocation is reset.
After the dislocation, the affected limb should be kept in an inwardly rotated position with a cotton pad in the axilla, and then fixed in the chest with a tricot, bandage or cast. After the posterior dislocation is reset, it is fixed in the opposite position (i.e. abduction, external rotation and posterior extension and pulling).
2.Surgical repositioning
There are a few cases of shoulder dislocation that require surgical repositioning. The indications are: anterior shoulder dislocation with backward slippage of the long head of biceps tendon that hinders manual repositioning; avulsion fracture of the greater tuberosity of the humerus with the fracture fragment stuck between the humeral head and the articular pelvis that affects repositioning; combined with fracture of the surgical neck of the humerus that cannot be repaired by manual repositioning; combined with fracture of the rostral process, acromion or shoulder glenoid with obvious displacement; combined with large blood vessel injury in the axilla.
3.Treatment of old shoulder dislocation
If the shoulder joint has not been repositioned for more than three weeks after dislocation, it is considered old dislocation. The joint cavity is filled with scar tissue, there are adhesions with surrounding tissues, contracture of surrounding muscles, formation of bone scabs or deformed healing in combined fractures, and all these pathological changes prevent the humeral head from resetting.
Treatment of old shoulder dislocation: If the dislocation is within three months, the patient is young and strong, the dislocated joint still has a certain range of motion, and there is no osteoporosis and intra- or extra-articular ossification on the X-ray film, a trial of manual repositioning can be performed. Before resetting, traction on the affected ulnar hawk can be performed for 1 to 2 weeks; if the dislocation is short and the joint activity is light, no traction can be performed. The resetting should be performed under general anesthesia, followed by shoulder massage and gentle rocking activities to release the adhesions and relieve muscle spasm, so as to facilitate resetting. The operation of resetting is done by traction and massage or foot stirrups, and the treatment after resetting is the same as that of fresh dislocation. It must be noted that the operation must not be rough to avoid fracture and axillary neurovascular injury. If the manual repositioning fails, or if the dislocation has exceeded three months, surgical repositioning can be considered for young and strong-aged casualties. If the joint surface of the humeral head is found to be severely damaged, then shoulder fusion or artificial joint replacement should be considered. After shoulder resurfacing surgery, the activity function is often unsatisfactory. For elderly patients, surgical treatment is not advisable and patients are encouraged to strengthen their shoulder activities.
4.Treatment of habitual anterior shoulder dislocation
Habitual anterior shoulder dislocation is mostly seen in young adults. It is generally believed that the injury was caused after the first traumatic dislocation, and although it was reset, it did not receive proper and effective fixation and rest. The joint becomes lax because the joint capsule is torn or avulsed and the cartilage glenoid lip and glenoid rim are not well repaired, and the posterior lateral humeral head depression fracture becomes equal to the pathological changes. Subsequently, dislocation may occur repeatedly under slight external forces or during certain movements, such as abduction and external rotation and posterior extension of the upper extremity. The diagnosis of habitual dislocation of the shoulder joint is relatively easy. During the X-ray examination, in addition to the anteroposterior plain radiograph of the shoulder, an additional anteroposterior radiograph of the upper arm in the 60°-70° internal rotation position should be taken, which can clearly show the posterior humeral head defect if it is present.