What Is the Acromioclavicular Joint?

It is composed of the scapula acromion articular surface and the clavicle acromion articular surface. The articular capsule is relatively loose, attached to the perimeter of the articular surface, and reinforced by the coracoclavicular ligament (orthorhombic ligament, conical ligament) that connects the coracoid process of the scapula and the clavicle. The acromioclavicular joint is a flat joint that can perform micro-movements in all directions.

It is composed of the scapula acromion articular surface and the clavicle acromion articular surface. The articular capsule is relatively loose, attached to the perimeter of the articular surface, and reinforced by the coracoclavicular ligament (orthorhombic ligament, conical ligament) that connects the coracoid process of the scapula and the clavicle. The acromioclavicular joint is a flat joint that can perform micro-movements in all directions.

Chinese name

Acromioclavicular joint

Foreign name

Primary ossification center

Overview of Acromioclavicular Joint Dislocation

The acromioclavicular joint is located at the micro-movement joint of the scapula acromion and distal clavicle. The joint capsule, acromioclavicular ligament, and coracoclavicular ligament maintain the stability of the joint. Anterior-posterior stability is maintained by the acromioclavicular ligament, and vertical stability is provided by the coracoclavicular ligament. When the shoulder joint is abducted at 90 °, the stress on the acromioclavicular joint is twice that of the human body. Therefore, when the acromioclavicular joint is dislocated, it will seriously affect the function of the entire upper limb.

The most important reason for acromioclavicular dislocation is direct violence. The shoulder joint is in the adducted position and directly hits the ground. The violence pushes the acromion downwards and inwards. If the distal clavicle fracture does not occur, then the acromioclavicular joint capsule will be damaged and broken. Then the force is transmitted to the coracoclavicular ligament, which causes damage or rupture of the coracoclavicular ligament. If the violence is strong enough, the clavicle continues to conduct, and the deltoid and trapezius muscles will tear at the point of clavicle resistance, causing complete dislocation of the clavicle. As a result, the entire upper limb loses the clavicle and scapula suspension, causing the upper limb to sag.

Dislocation of the acromioclavicular joint should be considered in patients with shoulder trauma. Acute acromioclavicular joint dislocation will result in adduction of the affected limb and support the affected elbow with a healthy limb to relieve shoulder pain. Palpation revealed local pain and swelling in the acromioclavicular joint area. In severe cases, the distal clavicle can be touched.

X-ray examination is the preferred method for diagnosis and classification of acromioclavicular joint dislocation. Zanca position examination (X-ray tube is tilted 15 ° to the head side) can reveal the acromioclavicular joint accurately. To distinguish type II injury and type III injury, a stress X-ray film can be used. A 10-pound weight is suspended from the wrist of the affected side, and X-ray films of bilateral acromioclavicular joints are taken. Of course, MRI can more intuitively detect whether the acromioclavicular ligament and the coracoclavicular ligament are broken.

Acromioclavicular Joint Surgical Treatment

The acromioclavicular joint is completely dislocated. If the external fixation cannot maintain its alignment, surgical incision and reduction of internal fixation are mostly used.

Kirschner wire tension band Kirschner wire tension band is applied earlier, with simple operation, less trauma, and low cost, but it is easy to loosen or break, and the Kirschner wire is displaced; Kirschner wire will pass through and damage the joint surface, causing Traumatic arthritis; limits the micromotion of the acromioclavicular joint, causing pain in the acromioclavicular joint. Stucken et al reviewed the efficacy of Kirschner wire tension bands in the treatment of acromioclavicular joint dislocation, and the patient satisfaction rate did not exceed 50%. Therefore, few clinical institutions have adopted Kirschner wire tension bands to treat acromioclavicular joint dislocation.

Coracoclavicular ligament reconstruction The coracoclavicular ligament is the most important structure for stabilizing the acromioclavicular joint. According to the literature, more than 60 types of coracoclavicular ligament reconstruction have been reported. Mainly include coracoclavicular fixation, ligament displacement reconstruction, autologous or allogeneic tendon transplantation reconstruction, artificial material reconstruction, etc.

In 1971, Cadenat first reconstructed the coracoclavicular ligament by transferring the coracoclavicular ligament. Weaver and Dunn also reported this technique in 1972. They reconstructed the coracoclavicular ligament by removing the distal clavicle and transferring the coracoclavicular ligament to the distal clavicle. Recently, Alentorn-Geli et al. Preserved the acromion bone fragments when cutting the acromion of the coracoid ligament, and then fixed the bone fragments to the clavicle, so that the ligaments and the clavicle were healed strongly.

Thomas et al. Transferred the combined tendon with a coracoid bone mass to the clavicle for the treatment of acromioclavicular joint dislocation, which is a dynamic fixation of the acromioclavicular joint and meets the biomechanical requirements. However, Saccomanno believes that the application of this technique to the treatment of acromioclavicular joint dislocation can easily lead to acromioclavicular osteoarthritis in the later stage. Therefore, it is recommended that the distal clavicle resection should be used at the same time to avoid the occurrence of acromioclavicular arthritis. But in fact, distal clavicle resection is mainly used to treat patients with chronic acromioclavicular arthritis.

Interbeak locks include Bosworth screws and titanium cables. Bosworth screws can make the coracoclavicular ligament heal without tension, have less trauma, and are relatively simple. However, they do not conform to the biomechanics of the acromioclavicular joint, and can easily cause the screws to break or loose, so they are not widely used.

Hook plate fixation In recent years in China, hook plate has become a common method for the treatment of acromioclavicular joint dislocation. Feng Lei and others used AO hook plate combined with polyester suture to treat acromioclavicular joint dislocation. . However, many scholars have pointed out that postoperative shoulder pain and dislocation recurrence after removal of the steel plate are the most common complications. Chen et al. Reported that the incidence of shoulder pain after surgery can reach 25.5%. Other complications include acromion impact, limited shoulder movement, clavicle acromion resorption, and plate rupture. Therefore, the purpose of the hook steel plate is to temporarily fix and maintain the effect of reduction, but it needs to be removed within 6 to 12 months after operation. If it is left for a long time, it will cause the corresponding complications mentioned above.

With the development of shoulder arthroscopy technology, more and more scholars have tried to use minimally invasive methods to treat acromioclavicular joint dislocation, and have achieved satisfactory results to a large extent. Salzmann applied double-strand suture technique under arthroscopy to treat acromioclavicular joint dislocation. Follow-up showed that the satisfaction rate was as high as 98%. Pan and others used Endobutton to reconstruct the coracoclavicular ligament under acroscopy to treat acromioclavicular joint dislocation. It was found that this method is less invasive, is conducive to the repair of the joint capsule and ligaments, and scarring, and allows the acromioclavicular joint to move within a certain range. Meet the requirements of biomechanics, and the effect is satisfactory. Pan Zhaoxun and others compared the effect of arthroscopy and incision under direct vision on the treatment of acromioclavicular joint dislocation, and found that arthroscopic surgery has the advantages of less trauma, higher patient satisfaction, and faster postoperative recovery, and the mechanical strength after surgery is not inferior For incision surgery. Overall, the advantages of arthroscopy are to reduce soft tissue damage and skin and wound complications, and patients can resume daily life early.