Suprascapular nerve compression syndrome

　　1. Etiology

　　The compression of the suprascapular nerve can be caused by acute injuries such as scapular fracture or glenohumeral joint injury. Dislocation of the shoulder joint can also damage the suprascapular nerve. Forward flexion of the shoulder, especially when the scapula is fixed, reduces the mobility of the suprascapular nerve, making it easy to be damaged. Tumors, humeral head ossicle cysts, and fibrosis of the suprascapular notch are all main reasons for the compression of the suprascapular nerve. Some reports suggest that traction during rotator cuff injury can also cause damage to the suprascapular nerve. Various local lipomas and nodules can compress the trunk or subscapular nerve branches of the suprascapular nerve, causing compression.

　　2. Pathogenesis

　　Sunderland believes that the suprascapular nerve is relatively fixed when passing through the suprascapular notch, making it easy to be damaged during repetitive movements. The repetitive movements of the scapula and glenohumeral joint cause friction of the nerve at the notch, resulting in inflammatory reaction and edema of the nerve, which can lead to compressive damage. It is known that the movement of the distal end of the scapula can tighten the suprascapular nerve, causing a 'suspension effect', which twists the nerve at the notch, leading to nerve lesions. Mizuno et al. reported that after the accessory nerve becomes paralyzed, the downward and lateral drooping of the scapula can cause the suprascapular nerve to be pulled by the suprascapular transverse ligament. The scapular branch of the suprascapular nerve can cause pain in the glenohumeral joint, which is the most common clinical symptom. Nerve lesions of the suprascapular nerve are mainly unilateral, but there are also reports of bilateral onset.

　　The main complications of this disease are that when the compression is severe and prolonged, it can cause demyelination of nerve fibers, even far-end axon degeneration, and Wallerian degeneration of the myelin sheath. During limb movement, nerve fibers in narrow channels are subject to chronic traumatic inflammation under mechanical stimulation, which aggravates the vicious cycle of edema and ischemia. This further causes damage, so patients with this disease should receive active treatment to prevent the occurrence of complications.

　　1. Patients often have diffuse dull pain in the periscapular area, located in the posterior lateral part of the shoulder, which may radiate to the back of the neck and the arm, but the radiation pain is often located in the posterior aspect of the upper arm. Patients often feel weak shoulder abduction and external rotation, and progressive cases may have atrophy of the supraspinatus muscle. However, in most cases, there is no obvious muscle atrophy, making clinical diagnosis difficult.

　　2. Patients usually have a history of trauma or overuse, such as direct or indirect injury to the shoulder, such as excessive abduction of the shoulder joint when reaching out to prevent a fall, resulting in sprain; some patients also have a history of overuse injury of the shoulder joint, such as sports-related overuse (such as volleyball, basketball, tennis, etc.), and a history of shoulder work-related injury.

　　3. Patients with trauma or overuse injury usually have sharp pain in the shoulder, which may worsen during shoulder movement. The pain may be persistent, and severe cases may affect sleep. There is no obvious muscle atrophy, difficulty in lifting the arm, or the affected hand cannot reach the opposite shoulder. Some patients have shoulder pain without other symptoms, and the pain may last for several years.

　　4. The most common sign of superior scapular entrapment is tenderness in the superior scapular notch or between the clavicle and the deltoid ridge triangular area. The trapezius area may also have tenderness. If there is entrapment at the scapular notch, the tender point is at the scapular notch, the shoulder abduction and external rotation strength are weakened; the supraspinatus and infraspinatus muscles atrophy, especially the infraspinatus muscle atrophy. Due to the innervation of the superior scapular joint branch to the acromioclavicular joint, tenderness may occur at the acromioclavicular joint, such as when there is entrapment at the acromial fossa notch, the pain is less than that at the superior scapular notch entrapment, the tenderness is located at the acromial fossa notch, and other manifestations are not obvious except for the atrophy of the infraspinatus muscle.

　　Superior scapular entrapment can be caused by acute injuries such as scapular fractures or glenohumeral joint injuries. Dislocation of the shoulder joint can also damage the superior scapular nerve. Therefore, the affected joint should be protected, the joint load reduced, weight loss paid attention to, rest ensured, and long-term weight-bearing and poor posture avoided. Use canes, walkers, and other aids. Pay attention to keeping the affected joint warm in daily life, and use hot water bottles, hot towels, and other warm compresses. Avoid direct blowing of air conditioning or electric fans on the joint during hot summer days.

　　1. Electromyography

　　Electromyography and nerve conduction velocity examination are helpful for the diagnosis of superior scapular entrapment syndrome. Khaliki found that in patients with superior scapular entrapment syndrome, the latency of evoked potentials is prolonged, and the electromyogram of the supraspinatus muscle may show positive waves, fibrillation waves, and decreased or absent motor potentials.

　　2. X-ray examination

　　The scapula should be tilted 15° to 30° towards the tail end on the anteroposterior X-ray film to check the shape of the superior scapular notch, which is helpful for diagnosis.

　　The diet of patients with suprascapular nerve entrapment syndrome should include two elements: vitamins and fiber. Especially B-group vitamins, which are very important substances for nerve metabolism, and vitamin C, vitamin D, and other nutrients are essential for the human body. Some fat-soluble vitamins are prone to deficiency, so it is appropriate to eat some milk, brown rice, brown flour, carrots, fresh vegetables, and fruits to supplement them. Eat some nuts, such as walnuts, ginkgo, and pine nuts, which contain abundant nutrients for nerve metabolism. Avoid smoking, alcohol, spicy, fried, and roasted foods.

　　First, Basic Requirements

　　The treatment of suprascapular nerve entrapment still focuses on surgical release. Conservative treatment such as rest, physical therapy, the use of painkillers, and local closure treatment can also be chosen. For injuries to the suprascapular nerve caused by trauma or traction, conservative treatment can be adopted in the early stage. For definite chronic compression, early surgical treatment should be performed, including nerve release and expansion of the suprascapular notch.

　　Second, Surgical Treatment.

　　The treatment of suprascapular nerve entrapment usually adopts three approaches: posterior approach, anterior approach, and cervical approach. The posterior approach is the most commonly used surgical approach, and the surgical steps are as follows:

　　1. Anesthesia and Incision

　　(1) Anesthesia: General anesthesia, lateral decubitus position.

　　(2) Incision: Starting from the acromion, extend medially along the scapular spine to the vertebral margin of the scapula, about 10cm long (Figure 1).

　　2. Surgical Steps

      Incise the superior margin of the free flap, incise the deep fascia, identify the insertion point of the trapezius muscle, and cut the insertion point of the muscle along the incision direction. Find the myositis gap between the trapezius muscle and the supraspinatus muscle, and separate it bluntly downwards to the superior limit of the scapula. Continue to separate laterally, and find the suprascapular nerve and suprascapular vessels. Displace the suprascapular vessels laterally to fully expose the possible compression factors of the suprascapular nerve, such as the suprascapular cruciate ligament and various fibrous bands, and release the compression factors. Free the suprascapular nerve, displace it, and use a bone chisel to expand the suprascapular notch. After the operation, hang the distal part of the limb and perform functional exercises as soon as possible.