The acromioclavicular joint is an important hub between the shoulder girdle and the trunk, and the stresses acting on the upper extremity are transmitted through the acromioclavicular joint. Dislocation of the acromioclavicular joint is mostly caused by direct violence and accounts for about 12% of shoulder injuries. The incidence is 5-10 times higher in men than in women. Incomplete injuries of the acromioclavicular joint are about twice as common as complete injuries. Age younger than 30 years accounts for the majority of cases, most of which are mild injuries and subluxations. In the United States, these cases are predominantly sports injuries, with American soccer players being extremely common with these injuries.
In other developed countries, they are common in rugby, soccer, etc. In China, falls on motorcycles and bicycles are more common. Injuries to the acromioclavicular joint can cause dysfunction of the entire upper extremity and seriously affect the quality of life of the patient. However, the choice of treatment for acromioclavicular joint injuries is still very controversial. Whether surgical or conservative treatment is used, the acromioclavicular joint will have varying degrees of residual dysfunction. Therefore, the choice of treatment modality and the corresponding rehabilitation are crucial to the functional recovery of the acromioclavicular joint.
I. Anatomical overview of the acromioclavicular joint
The acromioclavicular joint is a joint that consists of the inner edge of the acromion and the outer end of the clavicle, and its joint stability is maintained by three devices.
(1) the acromioclavicular ligament formed by the joint capsule and its thickened part;
(2) the tendonous attachments of the deltoid and trapezius muscles;
The rostral ligament (rhomboid and tapered ligaments) from the rostral process to the clavicle. The average distance between the clavicle and the rostral process is 1.2 cm (1.1-1.3 cm).
The acromioclavicular ligament mainly maintains the stability in the horizontal direction; the rostral ligament mainly maintains the stability in the vertical direction. The rostral collar ligament is more important for the function of the acromioclavicular joint. The rostral ligament is composed of two parts, the medial conical ligament and the lateral rhomboid ligament (also known as the deltoid ligament). The tapered ligament starts at the medial rostral root and ends vertically upward at the lower surface of the clavicle; the rhomboid ligament starts above the rostral root and ends obliquely outward at the lower surface of the clavicle.
Second, the subtype of acromioclavicular joint dislocation.
The most commonly used subtype of acromioclavicular dislocation is the Rockwood subtype. According to this type, acromioclavicular dislocation can be divided into 6 types: Type I is a contusion or partial rupture of the acromioclavicular ligament, with no significant instability of the acromioclavicular joint and no widening of the joint space visible on imaging; Type II is a complete rupture of the acromioclavicular ligament and a contusion of the rostral ligament, but the shape is intact, and only the widening of the rostral joint space without the upward displacement of the distal clavicle; Type III is a complete rupture of the rostral ligament, with the acromioclavicular joint in the vertical position. In type III, the rostral-clavicular ligament is completely ruptured, and the stability of the acromioclavicular joint in the vertical direction is lost, and the distal clavicle is displaced upward by 25%-100% of the thickness of the clavicle.
In type IV, the clavicular end is dislocated posteriorly into the trapezius muscle; in type V, the clavicular end is displaced upward to 100%-300% of the clavicular end thickness; and in type VI, the clavicular end is dislocated inferiorly to the sub rostral process. Type I, type II and type III injuries are common. There is also a variant of type III injury, Salter-Harris injury, which includes distal clavicular epiphysis injury, rostral fracture, and acromioclavicular dislocation. Because the distal clavicular epiphysis closes late (18-22 years of age), this injury can also occur in young adults.
In this case, the acromioclavicular joint is intact, the rostral ligament is attached to the intact periosteal sheath, and the epiphysis and cadaver of the clavicle are displaced upward through the periosteal rupture of the muscle.
Type I: incomplete rupture of the acromioclavicular ligament and intact rostral ligament, with mild displacement of the clavicle on X-ray; Type II: complete rupture of the acromioclavicular ligament and strain on the rostral ligament, with half of the diameter of the outer end of the clavicle protruding above the acromion on stress X-ray; Type III: complete rupture of the acromioclavicular ligament and rostral ligament, with piano-like sign on X-ray. The sign of piano may appear, and the X-ray shows complete displacement of the distal clavicle.
Treatment strategy of shoulder lock joint dislocation
Type I and type II dislocations: conservative treatment is mainly adopted. Type I injuries can generally resume normal activities in 1-3 weeks; while type II injuries generally resume normal activities in 2-12 weeks (generally 3-5 weeks). However, Martin Mikek, a foreign scholar, conducted a 10.2-year follow-up of 23 cases of type I and type II conservatively treated acromioclavicular dislocations, and at the last follow-up, about half of the patients had functional impairment of the acromioclavicular joint. Thus the long-term outcome of type I and II acromioclavicular dislocations is very uncertain.
2. Type III injury: It is very controversial in terms of treatment. It is currently believed that the indications for type III injury requiring one-stage surgery are.
(1) High aesthetic requirements or thin skin of the shoulder.
(2) Repeated lifting of heavy objects in the type of work.
(3) The shoulder joint is in the forward flexion >90o position for a long time.
3. For type IV, V and VI, most of them cannot be closed and reset because of the interlocking of the muscles and the distal clavicle, so it is better to operate.
The following principles should be considered for shoulder lock joint dislocation surgery.
1. The acromioclavicular joint is precisely reset and the vertical and horizontal stability of the joint surface at the lateral end of the clavicle is restored;
2. Repair or replace the avulsed ligament with an autologous (local or distant) / allograft ligament to achieve the original biomechanical form as much as possible;
3. The repositioned and reconstructed ligaments must be stable enough to avoid re-displacement until the injured ligaments are firmly healed; 4. Once the repaired or reconstructed ligaments are firmly healed, the strong endograft or temporary stabilization device should be removed immediately, otherwise it will break, loosen or produce stiffness of the shoulder joint.
IV. Treatment methods
(i) Conservative treatment.
The main treatment is the application of a sling (Kenny Howard sling) for suspension and fixation. Apply painkillers and physical therapy to reduce pain. Perform functional exercises until full-amplitude motion is achieved.
1.Post-traumatic arthritis: Many scholars report that joint degeneration can occur after Tossy I and II injuries, and the probability of X-ray changes can be as high as 75%, and the probability of symptoms is 48%. However, there is no clear relationship between the occurrence of symptoms and radiographic performance. If conservative treatment is not effective, distal clavicle resection can be considered. Type III injury may result in instability of the acromioclavicular joint if the distal clavicle is removed alone, so acromioclavicular joint stabilization (such as rostral ligament reconstruction, etc.) should be performed at the same time.
2, distal clavicle osteolysis: the main manifestation is pain (mostly occurs during abduction and flexion), but has a self-limiting tendency. osteolysis, osteoporosis, bone redundancy formation and distal clavicle acromegaly can be seen on radiographs [23].
3, neurovascular injury: mostly caused by the instability of the scapular band resulting in brachial plexus nerve pull; or due to the compression of the external fixation belt too tight. If thoracic outlet syndrome is caused then vascular symptoms will occur. Generally, the symptoms can be improved by scapuloclavicular joint stabilization without releasing the nerve.
4.Osseous ossification of the rostral-clavicular space: Whether treated conservatively or surgically, ossification of the rostral-clavicular space may occur. Ectopic calcification may occur around the injury area, or a bridge may be formed between the rostral process and the clavicle. The ossification of the rostral clavicular space does not have much effect on function.
5. Postoperative loss of repositioning and re-dislocation: The rate of re-dislocation/ or partial dislocation is high, but most patients with gradual loss of repositioning do not have obvious symptoms and mostly do not need reoperation. Only patients with acute re-dislocation, especially those with fracture or broken internal fixation, require reoperation
(ii) Surgical treatment.
(1) Apply K-wire or clavicle hook plate fixation.
Surgical points: The torn articular disc needs to be excised. Repair the acromioclavicular and rostral ligaments, repair the torn deltoid and trapezius fascia. It is being used less and less in the academic world.
(2) Weaver-Dunn procedure: The rostral ligament is reconstructed by transposition of the rostral shoulder ligament or the rostral ligament is reconstructed by autologous or allogeneic tendons. A wire or outline cable is also used for fixation between the rostral process and the clavicle.
(3) Dynamic reconstruction surgery is a surgical method in which the attachment point of the rostro-humeral muscle and the short head of the biceps at the rostral eminence is chiseled down together with part of the bone and fixed on the clavicle by moving it upward. This method is more suitable for young adults, who have more developed muscles and can reposition the acromioclavicular joint by traction with the movement of the upper arm. This method has a low recurrence rate of re-dislocation, but it is more damaging. When the affected limb is lifted, it is easy to cause friction and collision between the two ends of the joint surface, which will accelerate the degeneration of the acromioclavicular joint and lead to the occurrence of acromioclavicular arthritis. Therefore, the distal end of the clavicle was resected by 0.5~1 cm on the basis of this surgery to reduce the occurrence of acromioclavicular arthritis.
(4) The principles to be followed in the surgery of acromioclavicular joint dislocation are
(1) Remove the scar tissue and blood clot from the dislocation to achieve anatomical repositioning;
(2) Repair and reconstruct the corresponding ligaments and joint capsule to maintain the muscle balance of the shoulder joint;
(3) Reliable fixation to achieve firm healing of the ligament;
(3) Reliable fixation to achieve firm healing of the ligaments; and (4) Early and painless functional exercises to prevent the development of periarticular histopathy.
Surgical treatment may also have complications, such as incisional infection, injury to the vascular nerves, and postoperative secondary subluxation, etc. Although the current technology is mature and the chance of complications from surgical treatment is low, they still cannot be completely excluded.