Differential Diagnosis of Shoulder Joint Dislocation and Shoulder Joint Subluxation

- Jun 03, 2020-

Differential Diagnosis of Shoulder Joint Dislocation and Shoulder Joint Subluxation.

The shoulder joint is composed of six joints, which are divided into the shoulder-humeral joint, the glenohumeral joint, the acromioclavicular joint, the sternoclavicular joint, the coracoclavicular joint, and the scapular chest wall joint. Because the humeral head is large and spherical, the glenoid is shallow and small, the shoulder joint only surrounds 1/3 of the humeral head, and the joint capsule is thin and slack, so the shoulder joint is the largest and most flexible joint in the human body. Do flexion, extension, adduction, abduction, internal rotation, external rotation, and looping. However, although the structural characteristics of the shoulder joint ensure its flexibility, its firmness and stability are inferior to other joints, and it is the most unstable joint among the large joints of the whole body. Due to structural characteristics, the shoulder joint is prone to dislocation and subluxation due to external factors.

Traumatic shoulder dislocation is divided into anterior dislocation and posterior dislocation according to the position of humeral head. Anterior dislocation of the shoulder joint is very common, often caused by indirect violence, such as abduction and external rotation of the upper limb when falling, the palm or elbow touches the ground, external force impacts along the longitudinal axis of the humerus, and the humerus head is between the subscapularis and the great circular The weak part avulsed the joint capsule and prolapsed forward and downward to form anterior dislocation. The head of the humerus is pushed under the coracoid process of the scapula to form a subcoracoid dislocation. If the violence is greater, the humeral head is moved forward to the subclavian to form the subclavian dislocation. Posterior dislocation is rare, mostly because the shoulder joint is subjected to violent action from the front to the back or the hand touches the ground when it falls when the shoulder joint is retracted. Posterior dislocation can be divided into subscapular spine and subacromial dislocation. If the shoulder joint dislocation is not properly treated in the initial stage, habitual dislocation can occur.

Shoulder joint subluxation is mainly common in patients with hemiplegia. At present, the main considerations are as follows: 1. The function of the muscles around the shoulder joint, mainly the supraspinatus and deltoid muscles; 2. The relaxation and destruction of the shoulder capsule and ligament And prolongation caused by long-term stretching; 3, the paralysis of the muscles around the scapula, the scapula caused by the spasm rotates downward. 4. In the early nursing of upper limbs of hemiplegic side, including posture treatment, functional training and posture transfer were not properly handled.

Traumatic shoulder dislocation has a history of obvious trauma, shoulder pain, swelling and dysfunction. The injured limb is elastically fixed in mild abduction and internal rotation, elbow flexion, and the affected side forearm is supported with the healthy hand. The appearance is a "square shoulder" deformity, the acromion is prominent, and the acromion is empty. The humerus and head can be felt under the armpit, under the coracoid process, or under the collarbone. The injured limb is slightly abducted and cannot be close to the chest wall. For example, when the elbow is attached to the chest, the palm of the hand cannot touch the contralateral shoulder at the same time (Dugas sign, which is a positive shoulder test). A ruler placed on the outer side of the upper arm can simultaneously contact the acromion and the lateral upper ankle of the humerus (straight rule test).

Shoulder subluxation does not occur immediately after hemiplegia, but occurs in Bronnstrom stage I ~ II dystonia, most of which occurs within 1 month after the disease. It was discovered more than after starting the sitting activity. Early patients may not feel any discomfort, and some patients may experience discomfort or pain when the upper limb of the affected side hangs for a long time on the side of the body. When the upper limb is supported or lifted, the above symptoms can be reduced or disappeared. Over time, severe shoulder pain may occur.

Inspection method of shoulder dislocation:

1. Abnormal features of shoulder joint X-ray and CT examination report: ① Due to the forced internal rotation of the humerus head, even if the forearm is in the neutral position, the humerus neck can be found to be "shortened" or "disappeared", and the large and small nodules overlap ; ② The gap between the inner edge of the humeral head and the anterior edge of the scapula is widened. It is generally considered that the gap is greater than 6mm, which can be diagnosed as abnormal; The relationship is asymmetric, showing high or low, and it is not parallel to the front edge of the glenoid.

2. When the shoulder dislocation is highly suspected, an axillary film or a thoracic film should be added, and the humeral head prolapse is located on the back of the scapula. If necessary, a CT scan of the shoulders can clearly show that the humeral head joint is facing backwards and protruded from the posterior edge of the glenoid; sometimes a humeral head fracture can be found and form a compression with the posterior edge of the glenoid, which affects the reduction, or the glenoid Fracture at the trailing edge.

3. Shoulder joint dislocation should be checked for comorbidities, about 30 to 40% of cases of shoulder joint dislocation combined with large tubercle fractures, humeral surgical neck fractures, or humeral head compression fractures, sometimes combined with joint capsule or scapular glenoid Torn off from the front attachment, poor healing can cause habitual dislocation. The long head tendon of the biceps brachii can slip backwards, which can cause obstacles to joint reduction. The axillary nerve or brachial plexus nerve medial bundle can be compressed or pulled by the humeral head, causing nerve dysfunction, and can also damage the axillary artery.

Inspection method of shoulder subluxation:

1. Shoulder joint subluxation shows the collapse of the deltoid muscle of the shoulder, the loosening of the joint capsule, and the downward displacement of the humeral head, showing a slight square shoulder deformity. The joint Meng is empty, and there can be obvious depressions between the acromion and the humeral head, which can accommodate 1--2 transverse fingers. As muscle tone increases and motor function increases, the above-mentioned signs can gradually reduce or even disappear. Most patients only show temporary relief and disappearance when holding up the upper limbs or when they are nervous, active, and hard, and still show obvious subluxation when the upper limbs are relaxed and unsupported in the sitting position.