Advances in scapular instability research In the past decade or so, great progress has been made in shoulder arthroscopy techniques, rotator cuff repair, and treatment of glenohumeral instability, but research on the diagnosis and treatment of scapular instability is rare, and the literature on related studies is relatively scarce. I. Background 1. The anatomy and function of the scapula The scapula and the chest wall form a micro-movement joint, the acromioclavicular joint, which is an important part of the normal activity of the shoulder joint.1 One third of the activity of the shoulder joint is accomplished by the activity of the acromioclavicular joint, and the remaining 2/3 is accomplished by the glenohumeral joint, except for the muscle attachment around the scapula, only the rostral ligament [1], the acromioclavicular ligament, and the rostral shoulder ligament The movement of the scapula is accomplished by the muscles and ligaments of the shoulder-thoracic joint and its surrounding soft tissues. The muscles around the scapula support the scapula to accomplish multi-directional activities, such as the scapular raphe and upper trapezius to stabilize the position of the scapula, the middle trapezius and rhomboid to pull the scapula medially, and the anterior serratus to pull the scapula anteriorly, and the trapezius and anterior serratus together to complete the upward and rotation of the scapula. The upper trapezius and scapularis can also lift the scapula upward. The muscles around the scapula work together to maintain the stability of the scapula and also maintain the stability of the glenohumeral joint.2-4 Sometimes the scapula can also transmit the force from the lower extremity and trunk to the upper extremity to achieve the purpose of stress relief. 2, the stability of the scapula The scapula works with the humerus to complete the normal rotational movement of the shoulder joint, and provides a stable base for the upper limb pushing, pulling, reaching and throwing movements, so it is very important to maintain the dynamic stability of the scapula. However, if there is a problem with the muscles that stabilize the scapula, the scapula will become unstable. Examples include scapulohumeral fascial dysplasia, anterior serratus paresis due to thoracic long nerve palsy, rhomboid abnormalities due to paraplegia, and rhomboid and scapular raphe disorders due to dorsal scapular nerve palsy. The movement of the scapula is complex and includes lifting, sinking, rotation, and movement medially and laterally, especially rotation, and sometimes there may be two abnormal activities such as scapular flutter and stretching of the scapula. pterygoid shoulder was first reported by Winslow in 1723.5 Pterygoid shoulder is mainly caused by anterior serratus palsy, whereas chronic spinal injuries often lead to instability of the scapula by pulling, and the former anterior serratus muscle starts from the chest wall and ends at the medial edge of the scapula, while the latter scapula is located on either side of the midline of the trunk and abuts the thorax, but when the scapula rotates, when the scapular glenoid and capsular ligament tissues are angled forward, this leads to increased tension in the inferior glenohumeral ligament ligaments, and a bulge in any part of the scapula can strike the chest wall causing symptoms. Second, the causes of instability of the scapulothoracic joint If the muscles around the scapula are injured, scapular instability will occur. If the scapula becomes unstable, the deltoid muscle will be involved in disuse atrophy, and when the deltoid muscle contracts to move the upper limb according to normal physiological movement, the scapula will rotate or lunge with the upper limb to complete the synergistic movement after scapular instability.6 1.Primary factors 2.Nerve injury 3.Paraneoplastic nerve Injury The parasympathetic nerve mainly innervates the trapezius and sternocleidomastoid muscles, it receives branches from the cervical 2, 3 and 4, but is actually an individual sensory nerve, which passes from the jugular foramen out of the cranial cavity, often behind the jugular vein, folds posteriorly through the posterior side of the sternocleidomastoid muscle, penetrates into the posterior cervical triangle at the upper 1/3, and terminates vertically through the posterior cervical triangle at the deep part of the trapezius muscle. The collateral nerve travels relatively superficially and is adjacent to the superficial cervical lymph nodes. The trapezius muscle is the main stabilizing structure of the scapula when the scapula moves in concert with the upper limb. The upper trapezius fibers together with the scapularis raphe and the serratus anterior muscle move in concert to complete the rotational function of the scapula and help the upper limb to lift over the head. The middle trapezius muscle pulls the scapula to maintain the medial edge of the scapula stable against the chest wall. The inferior trapezius completes the counterclockwise rotation of the scapula.7, 8 Paraplegia of the paraspinal nerve is often caused by compression at the posterior cervical triangle, which eventually leads to paralysis of the trapezius muscle. It can also be caused by sharp force injuries or localized strain injuries, but is more commonly caused by injuries from surgical operations in the posterior cervical triangle, such as lymph node biopsy.9-12 The paraspinal nerve may also be removed during radical neck resection, and simple paraspinal degeneration Rarely, this condition occurs when the sternocleidomastoid muscle is accumulated at the same time, and paralysis and atrophy of the trapezius muscle results in sinking of the scapular glenoid, counterclockwise rotation of the scapula, and scapular instability.10 Active abduction of the shoulder joint is limited to 80 degrees, and if the involvement of the sensory branch of the paramedian nerve is caused by a pulling injury to the brachial plexus nerve, it is accompanied by severe pain and causes secondary acromioclavicular impingement of the shoulder joint. The diagnosis of paraspinal nerve injury is generally delayed.9C11, 13 Williams12 reported that paraspinal nerve injury is more appropriately repaired at 6 to 8 months, and that examination of scapular lift alone is not helpful in diagnosing paraspinal nerve injury, because the scapular lift compensates for this part of the movement, and pain and limited abduction are other manifestations of paraspinal nerve injury. In addition, Nakamichi et al. found that there can be no muscle atrophy unless the patient is diabetic.14 4. Thoracic long nerve injury Velpeau15 reported in 1837 that paralysis of the thoracic long nerve (c5,6,7) caused anterior serratus disorder leading to scapular instability. Many mechanisms of injury to the long thoracic nerve have been reported, with poke or blunt injury being the common cause, as it travels superficially, while the long thoracic nerve can also be injured by jerking the upper extremity to cause tension injury or by sinking compression during shoulder motion. Injury to the long thoracic nerve has also been reported to occur between the first rib and the medial border of the scapula.17 Of course, medical factors such as mastectomy, first rib resection, anesthesia, and prolonged lying can also cause injury to the long thoracic nerve; viral infections, neuritis, immune reactions, and transaxillary sympathectomy and Turner’s syndrome can also cause injury.18 If cervical spine disease is present, the long thoracic nerve can be injured. If cervical spine disease involves the C7 nerve root, it can sometimes show abnormalities of the long thoracic nerve. The dorsal scapular nerve starts at the posterior cervical triangle from the 5th cervical nerve and travels 75% of the way to the prevertebral fascia.31 The dorsal scapular nerve often meets with branches of C4 and T1 or travels with the common trunk of the long thoracic nerve.32-34 The dorsal scapular nerve penetrates the middle trapezius muscle and travels behind the posterior trapezius and scapular raphe until it terminates at the rhomboid muscle, sending branches to the scapular raphe on the way. Because the rhomboid and scapularis are responsible for pulling and lifting the scapula, injury to this nerve can lead to scapular instability. The large and small rhomboid muscles are innervated by the dorsal scapular nerve. Injury to the dorsal scapular nerve manifests as pain at the medial border of the scapula, with the scapula in a normal position at rest, but when the upper limb is raised, the position of the scapula is the same as when the trapezius muscle is paralyzed, especially when the raised upper limb is slowly lowered, and the pterygoid deformity of the scapula is aggravated. Injury to the dorsal scapular nerve alone is rare and is often accompanied by radicular damage to the cervical 5 nerve. Blunt injury to the chest wall accounts for 26% of thoracic dorsal nerve injuries.19, 20 Some normal sports such as volleyball, weightlifting, gymnastics, and ballet may lead to strain injury to the nerve.21-24 Repetitive assembly line manipulation also causes scapular instability from time to time.25, 26 Ravindran35 reported two volleyball players with dorsal scapular nerve entrapment combined with entrapment of the subscapular nerve, hypertrophy of the The mid-rhomboid muscle entrapment or compression of the dorsal scapular nerve can cause atypical thoracic outlet entrapment syndrome.Chen et al.32 obtained better results in patients who released the dorsal scapular nerve by removing the mid-rhomboid muscle in 22 patients. 6, soft tissue causes Lesions of the soft tissues around the scapula can directly affect the stability of the scapula, such as bursitis, tears of the anterior serratus after severe trauma or injuries caused by open-heart surgery exposure, especially in patients with congenital anterior serratus, rhomboid and rhomboid deficiencies, which are relatively complex. Facioscapulohumeral muscular dystrophy (FSHD) is the third common genetic disorder of the muscles after Duchenne’s muscular lesion and myotonic dystrophy.36- 41 Landouzy and Dejerine 36- It often presents with atrophy of the muscles of the face, upper limbs, and shoulders, and can involve the muscles of the trunk and pelvis, sometimes manifesting as anterior protrusion deformity, with exacerbation leading to inability to walk and loss of shoulder function42-44 because shoulder abduction begins at 90 degrees by the glenohumeral joint FSHD can involve all the muscles around the scapula such as the serratus anterior, rhomboid, rhomboid, masseter, masseter and scapularis, so if the patient abducts or lifts the upper limb, the scapula will lose its normal stability and the glenohumeral joint will drive the scapula to rotate excessively, which will manifest as Scapular instability and limited movement of the upper limb affect the patient’s daily life activities, such as combing hair and brushing teeth.45,46 7. Bone tissue causes Osteochondroma of the scapula or subcostal bone can obviously affect the popping of the scapula or pseudopterygoid shoulder, and the diagnosis can be clarified by X-ray or CT scan examination. Occasionally, unilateral healing of the scapular deformity can also lead to scapular instability. Thomas47 reported a 12-year-old patient with a clinically typical pterygoid scapular deformity due to a scapular cycloid fracture, so it is important to clarify the scapular instability due to a high-energy injury that causes a scapular fracture. 8. Secondary causes Whether secondary or primary, instability of the glenohumeral joint often leads to abnormal motor function of the thoracic scapular joint.47 A link between abnormal glenohumeral joint motion and scapular instability has been reported, for example, anterior tilting of the scapula increases instability beneath the glenohumeral joint. Both joint and periarticular muscle abnormalities can secondary to abnormal motion states of the scapulothoracic joint. Major factors include acromioclavicular impingement, rotator cuff injury, nonunion or delayed healing of the scapular glenoid, acromion, and clavicle, or disorders such as humeral head necrosis, A-C joint abnormalities, and frozen shoulder, which cause muscle spasm or decrease glenohumeral joint mobility when the periacetabular muscles are involved or engaged in compensatory, which in turn leads to scapular instability. Abnormal scapular motion is often a major factor in periacetabular disease, so the primary disease is the first problem to be addressed. 9.Psychological factors Scapular instability in volunteers due to psychological suggestion. Psychological scapular instability is often manifested as asymmetric scapular pterygoid instability, which is rare but reported from time to time. The test for identification is when physiotherapy is performed to train the scapular muscles in normal movement patterns, or when the patient is asked to undergo a psychological assessment test to identify the condition.