Shoulder joint instability

　　One, the cause of the disease

　　1. Congenital or developmental skeletal factors:A small glenoid, a deep articular surface, an excessively posterior tilt of the glenoid (an excessively large posterior glenoid angle), and a defect in the posterior inferior margin of the glenoid are all important factors in the instability of the glenohumeral joint.

　　(1) Abnormal development of the humeral head, posterior superior defect (Scaphoid deformity), and abnormal inversion deformity of the humerus, leading to an excessively large anterior inclination angle of the humeral head, are often the basis for recurrent shoulder joint dislocation.

　　(2) Soft tissue factors: seen in systemic joint capsule and ligament laxity syndrome (Ehlers-Danlos syndrome) caused by mesodermal developmental defects.

　　2. Paralytic factors:The main muscles of the shoulder joint and the nerves that innervate these muscles can cause shoulder joint instability due to paralysis. Brachial plexus injury (including birth injury), axillary nerve injury, superior scapular nerve entrapment syndrome, accessory nerve injury, and neonatal paralysis sequelae can all cause muscle paralysis, leading to shoulder joint instability.

　　3. Traumatic factors:Traumatic shoulder joint dislocation in young and middle-aged individuals can cause detachment of the joint capsule, detachment of the labrum, and injury and relaxation of the middle and lower glenohumeral ligaments, which are common causes of recurrent shoulder joint dislocation and subluxation. Labral detachment is difficult to heal, and the detachment of the labrum at the anterior-inferior position can cause recurrent shoulder joint dislocation, while the detachment of the labrum at the anterior position is more likely to cause recurrent shoulder humeral joint subluxation.

　　(1) The function of the rotator cuff is not only related to the movement of the proximal end of the humerus but also crucial for the stability of the glenohumeral joint. A widespread rotator cuff tear causes instability of the glenohumeral joint in the anterior-posterior and superior-inferior directions. Elderly patients often have rotator cuff injuries when dislocating the shoulder joint, leading to shoulder joint instability in the future.

　　(2) The tear of the rotator interval is a special type of rotator cuff injury. The splitting of the interval between the supraspinatus tendon and the subscapularis muscle significantly weakens the synergistic action of the two muscles during the raising of the arm and the combined force for fixing the humeral head on the glenoid, causing joint instability and the phenomenon of shoulder humeral slipping during the lifting process.

　　4. Idiopathic shoulder looseness:Idiopathic shoulder looseness is a condition of multidirectional instability of the shoulder joint without clear cause or anatomical morphological abnormalities, which can occur in either unilateral or bilateral cases. X-ray examination shows the appearance of glenohumeral joint subluxation at the superior position, and the humeral head loosens downwards when the upper arm is pulled downwards. This condition is known as multidirectional shoulder instability or multidirectional glenohumeral joint subluxation in English-speaking literature, and as shoulder looseness syndrome in Japan. Some scholars believe that patients with this condition have a defect in the posterior inferior margin of the glenoid, an excessive posterior glenoid angle, and it is a strictly localized instability within the glenohumeral joint.

　　5. Psychological factors:Voluntary glenohumeral joint dislocation and subluxation are caused by the voluntary contraction of muscles. Rowe emphasized the importance of psychological factors in the etiology of the disease in 1973.

　　2. Pathogenesis

　　1. The broad sense of the shoulder joint refers to the joint complex composed of 6 parts: the glenohumeral joint (the first shoulder joint), subacromial joint (the second shoulder joint), intercostal-thoracic wall connection, coracoclavicular joint, acromioclavicular joint, and sternoclavicular joint. The first three are the main movement parts of the shoulder joint complex, and the last three belong to the micro-motion parts.

　　2. The narrow sense of the shoulder joint refers to the glenohumeral joint. The glenohumeral joint is a pivot joint composed of the glenoid and the humeral head. The humeral head is large and nearly spherical: the glenoid articular surface is nearly oval in shape, with an area only 1/3 of the humeral head articular surface. The glenoid is shallow,呈碟状, surrounded by fibrocartilage to form the glenoid labrum. The joint capsule wall is loose and elastic, forming folds in the anterior, posterior, and axillary parts, allowing the shoulder joint to maintain the greatest range of motion. Shoulder joint instability usually refers to the instability of the glenohumeral joint.

　　3. The shoulder joint relies on the ligamentous tissue, joint capsule, and surrounding muscles to maintain its stability. The main stable structures, in addition to the intra-articular stable devices such as the fibrous joint capsule, glenohumeral ligament, coracohumeral ligament, and deepening of the glenoid fossa, include the rotator cuff muscle group (supraspinatus, infraspinatus, subscapularis, and teres minor), deltoid muscle, biceps brachii, triceps brachii, and the muscle groups connecting the trunk and scapular belt (pectoralis major, pectoralis minor, rhomboid muscle, levator scapulae, latissimus dorsi, trapezius, and serratus anterior, etc.). The intra-articular stable devices, rotator cuff muscle group, deltoid muscle, biceps brachii, and triceps brachii are the most important for the stability of the glenohumeral joint. These muscles are both the stable structure of the shoulder joint and the power device for shoulder joint movement.

　　1. Severe pain in the shoulder joint after injury.

　　2. The range of motion of the shoulder joint is severely limited.

　　3. The shoulder joint hangs down and forward, with a large depression under the acromion.

　　4. The humeral head can be seen in front of the shoulder or in the armpit, resembling a mass. To reduce the dislocation of the shoulder joint, it is usually necessary to seek help from the emergency department of the hospital to find a doctor, while some patients with recurrent shoulder dislocation have a lot of experience and can reduce the dislocation themselves.

　　1. Symptoms

　　1. Pain:Presented as dull pain in the shoulder, exacerbated during movement or weight-bearing, joint instability, and a feeling of crepitus; 70% of patients feel instability of the glenohumeral joint and have a feeling of crepitus, often appearing when lifting or abducting to a certain angle, and the symptoms are more obvious during weight-bearing, with more than half of the patients experiencing fatigue and weakness, especially unable to lift heavy objects for a long time, and about 1/3 of the patients have numbness around the shoulder.

　　2. In the glenohumeral joint:Repeated anterior dislocation has typical deformity and dysfunction during the occurrence of dislocation, which is prone to occur during external rotation, abduction, and extension, and it is relatively easy to reduce the dislocation, but the symptoms are not as obvious as acute shoulder joint dislocation.

　　Symptoms

　　During the examination, the patient should be fully exposed with both shoulders, sitting opposite to the examiner, and the examination content should include:

　　1. Whether there is muscle atrophy:Including the deltoid, supraspinatus, infraspinatus, teres minor, and other muscles of the upper limb.

　　2. Range of motion of the joint:Including elevation, abduction, extension, and passive internal and external rotation (performed simultaneously with the healthy side for comparison), the range of motion, palpate the front of the joint during passive extension and flexion movements and active abduction and elevation to detect any clicks or instability vibration, if the shoulder and humeral joint has excessive movement in all directions, further examination of other joints of the limbs should be performed.

　　3. Joint stability examination:Push the humeral head in the anteroposterior direction to detect any excessive looseness, and pull the upper arm downward in the internal and external rotation positions, if the humeral head moves downward significantly, and a noticeable depression appears between the acromion and the humeral head, it indicates downward instability (loosening). Idiopathic shoulder instability and rotator cuff interval tears have the above-mentioned manifestations. Unstable shoulder anteriorly and inferiorly is the most common type, and less common recurrent posterior shoulder dislocation exists with posterior instability, and the humeral head is prone to be pushed backward.

　　4. Tenderness location:Recurrent anterior shoulder dislocation or Bankart lesion may have tenderness in the anterior and inferior parts of the glenoid; tenderness from rotator cuff injury is often located below the acromion and near the greater tubercle, tenderness in the rotator cuff interval at the outer margin of the coracoid process, increased pain during passive external rotation, congenital developmental malformation, and paralytic, voluntary shoulder joint subluxation often have no fixed tenderness points in the shoulder and humeral joint instability.

　　This disease is caused by direct trauma to the shoulder joint, such as falls, falls, or emergency braking while driving. Therefore, attention should be paid to living habits, high-risk workers such as construction workers, miners, and machine operators are prone to injury, and they should pay attention to protecting themselves during work. Stay calm in the face of things, avoid emotional excitement and conflict, which can lead to this disease. Secondly, early discovery, early diagnosis, and early treatment are also of great significance for the prevention of this disease.

　　1. X-ray examination

　　1. Routine X-ray:The presence of a posterior superior defect of the humeral head on the anteroposterior film (scimitar deformity) supports the diagnosis of recurrent shoulder joint dislocation. If there is a slipping phenomenon of the humeral head in the anteroposterior X-ray film of the elevated arm, it indicates the existence of lateral instability. If there is a significant downward movement of the humeral head when the affected arm is pulled down, it is an X-ray manifestation of inferior instability of the shoulder joint.

　　2. Axial X-ray film:It is helpful to discover poor glenoid formation or posterior inferior margin defects, and to understand the relationship between the humeral head and the glenoid (whether the center of the humeral head deviates from the central axis of the glenoid). Axial imaging can also measure the posterior glenoid angle (posterioroperingangle) and the glenoid tilt angle (glenoidtilingangle). Anteroposterior imaging can determine the free joint surface of the humeral head, the free surface central angle of the humeral head (more than 80° indicates instability), and the glenoid index (the ratio of the long diameter of the glenoid to the long diameter of the humeral head). The measurement of these indicators is of reference significance for the etiological diagnosis of shoulder joint instability.

　　3, Arthrography:It is still a relatively reliable method for diagnosing rotator cuff tear and rotator cuff gap splitting at present. The former can see the contrast agent溢出 from the glenohumeral joint cavity through the rotator cuff rupture, and the latter can see the contrast agent溢出 between the acromion and the supraspinatus muscle and subscapularis muscle, forming a papillary or striated abnormal shadow. During arthrography, the anteroposterior or posterior oblique projection of the humeral head can be observed.

　　4, In the case of habitual shoulder joint:When performing arthrography for joint laxity caused by dislocation and subluxation, and idiopathic shoulder instability, the contrast agent can be seen to accumulate above the humeral head when the affected arm is pulled down in the internal rotation position, forming a 'snowcap shadow'.

　　Second, special examination

　　1, CT examination:Can detect rotator cuff injury and abnormal anterior humeral head angle caused by abnormal rotation of the humeral shaft, and if combined with low concentration double-contrast agent contrast, it can help to detect anterior joint Hill-Sachs lesion and Bankart lesion.

　　2, Ultrasound examination:Helpful for the diagnosis of complete rotator cuff rupture and severe tearing.

　　3, Electromyography:And shoulder joint motion analysis methods: have diagnostic value for shoulder joint instability caused by paralysis, and have certain reference significance for the diagnosis of idiopathic shoulder laxity and rotator cuff gap splitting.

　　4, Arthroscopy:Some pathogenic factors within the joint, such as rotator cuff injury, labral detachment, and laxity of the glenohumeral ligament, as well as the cartilage avulsion of the humeral head secondary to instability, are all direct diagnostic methods.

　　In general, patients can eat any diet without the need to avoid certain foods. However, during the onset of the disease, it is not advisable to eat spicy and刺激性 food; for those with chronic illness and deficiency of the spleen and stomach, it is recommended to eat less cold fruits and vegetables, as well as shrimps, crabs, and bamboo shoots. Once the condition is stable, the dietary restrictions can be relaxed.

　　First, non-surgical treatment

　　Primarily used for non-traumatic voluntary and involuntary semi-dislocation. The above types of shoulder joint instability have good efficacy in rehabilitation treatment and psychological treatment, with improvement rates of 75% and 87% respectively, while the efficacy of surgical reconstruction is very poor and often fails. Muscle function training, including strengthening the strength of the deltoid, supraspinatus, pectoralis major, biceps brachii, and triceps brachii, as well as applying the principle of muscle movement biofeedback for复位, using electromyography to check the feedback results for long-term muscle resistance rehabilitation training, can achieve a good response.

　　Second, Surgical Treatment

　　Mainly used for skeletal developmental defects and traumatic shoulder joint instability. The surgical methods can be divided into the following 7 types:

　　1. Anterior Capsule Tightening and Strengthening the Anterior Joint Wall Surgery: Such as Bankary and Putti-Platt, Magnuson methods, which are commonly used for habitual anterior shoulder dislocation and idiopathic shoulder looseness.

　　2. Utilizing Muscle Transplantation to Construct a Muscle Line to Prevent Humeral Head Dislocation: Such as Boythev method, Bristow method, and Nicola method, etc.

　　3. Utilizing Bone Blocking for Humeral Head Dislocation: Such as Oudard surgery and its modified version, Eden-Hybbinette method is also a frequently used method for treating recurrent shoulder joint dislocation.

　　4. Shoulder Acetabulum and Humeral Head Subcapital Osteotomy: Posterior inferior acetabular osteotomy is used to treat acetabular hypoplasia and idiopathic shoulder looseness, which can achieve good results. Shoulder acetabular horizontal rotation osteotomy or humeral head subcapital rotation osteotomy is used for the correction of humeral reverse rotation deformity (excessive anterior tilt angle).

　　5. Tendon Repair Surgery: Shoulder joint instability secondary to rotator cuff tears and rotator cuff gap separation, the stability is restored after the above-mentioned tendon repair.

　　6. Muscle Transplantation Surgery: Mainly used for paralytic shoulder joint instability, such as using the pectoralis major or latissimus dorsi muscle insertion for the scapula to treat idiopathic shoulder looseness.

　　7. Nerve Surgery: Nerve anastomosis, transplantation, and decompression surgeries are used for brachial plexus and accessory nerve injuries, and superior scapular nerve entrapment syndrome.

　　Due to the polyetiological nature of shoulder joint instability, it is necessary to start with the medical history and clinical examination, and according to the information about glenohumeral joint instability such as X-ray films and angiography, clarify the etiology and related pathological characteristics, and choose reasonable and effective treatment methods.