Treatment of AC joint dislocation

                   Treatment of AC joint dislocation

                                           Dr KS Dhillon

Introduction

The true incidence acromioclavicular (AC) injuries is not known because many with such injuries do not seek medical treatment. About 12% of shoulder dislocations involve the AC joint. The treatment of AC joint injury remains controversial although good long term results can be seen in patients treated conservatively. There is an increasing tendency to treat higher grade injuries surgically.

Anatomy of AC joint

The acromioclavicular (AC) joint is a synovial arthrodial joint with an intra-articular disc, where the oval lateral end of the clavicle articulates with an imperfect incongruent facet of the acromion. Although it is a small joint it supports the shoulder girdle and the upper limb [1].

The joint stability is provided superiorly by reinforcement of the capsule with a strong acromioclavicular ligament and inferiorly the capsule and a weak inferior acromioclavicular ligament. These ligaments provide about 68% of joint stability to superior translation of the clavicle. Additional stability is provided by the coracoacromial and the coracoclavicular (conoid and trapezoid) ligaments [1].

The clavicle rotates about 45 degrees on its own axis. Most of this motion occurs at the sternoclavicular joint and only about 5 to 8 degrees of motion occurs at the sternoclavicular joint [2].

Imaging anatomy of the AC joint

The AC joint is best viewed in an AP projection with a 10-15 degree cephalic angulation (Zanca view). In this view, the clavicle is projected off the spine of the scapula [3].

The AC joint space is measured as an average of the cranial and caudal joint space measurements. It is usually less than 5mm. In males the average is about 3.3 plus minus 0.8 and in females the average is about 2.9 plus minus 0.8. In both males and females, the joint space reduces with age and space of less than 0.5 mm can be found. A joint space of more than 7 mm in males and more than 6 mm in females is pathological irrespective of age. There is no significant difference between the left and the right [4].

The coracoclavicular distance is usually less than 11-13mm and the right and left difference is usually less than 5mm [5].

Classification of AC joint injuries

The most commonly used classification for AC joint injuries is the one by Rockwood et al [6]:

Type I. Partial tear of acromioclavicular ligaments. X-rays are usually normal. Pain, swelling and local tenderness at the AC joint often present. Cross arm test is positive.

Type II. Complete tear of the acromioclavicular ligaments. Plain X-rays are usually normal. Some widening of the AC joint space may be present. The inferior border of the clavicle is not elevated beyond the superior border of the acromion.  Pain, swelling, tenderness, and deformity at the AC joint is usually present.

Type III. Clinically obvious deformity is seen. X-rays show vertical translation with the inferior border of the clavicle elevated beyond the superior border of the acromion.

Type IV. Posterior displacement of the lateral end of the clavicle into or through the trapezius muscle occurs. An axial view will show the posterior displacement of the lateral end of the clavicle.

Type V. Disruption of the deltotrapezius fascia occurs which allows the lateral end of the clavicle to lie under the skin. X-rays show marked displacement of the clavicle beyond the medial end of the acromion.

Type VI. A very rare injury. The lateral end of the clavicle is displaced inferiorly and lies below the acromion and the coracoid (as well as the conjoint tendon).

Treatment of AC joint injuries

The treatment of AC joint injuries remains controversial. Although in recent years more surgeons are opting for surgical treatment of severe AC joint injuries, the outcome of conservative treatment is good on long term follow up. Nonoperative treatment of complete AC joint dislocations have generally yielded reasonable results, although there are some patients who have reported dissatisfaction with the outcomes [7,8,9,10]. Rawes and Dias [11] reviewed 30 patients, who were treated conservatively for dislocation of the AC joint, at an average of 12.5 years after the injury. They found good outcomes in all except one patient. X-rays showed persistent dislocation in 17 patients and in 13 the dislocation improved to a subluxation. Atrophy of lateral end of clavicle (similar to resection of lateral end of clavicle) was seen in completely dislocated joints.
Randomized prospective controlled trials also show good outcomes of conservative treatment for dislocation of the AC joint [10,12]. However, the current trend for the treatment of type I and type II injuries is conservative with symptomatic relief provided by ice, arm sling, and analgesics. Heavy lifting and sports are usually avoided for 8 to 12 weeks [13].

The current consensus on the treatment of type III injuries remains that of a conservative approach because the prognosis after conservative treatment is excellent [14,15,16]. However, patients with type III injuries who continue to have symptoms after 3 months may be considered for surgical treatment [13]. Some surgeons prefer surgical treatment in patients with type III injury who are heavy laborers and overhead athletes [17].

Type VI injuries are very rare and most of the reported cases are case reports where the patients have been treated surgically [18,19,20]. In medically fit patients who have type IV and V injuries the treatment is usually surgical [13].

Murray et al [21] published in 1918 the outcome of The ACORN Prospective, Randomized Controlled Trial comparing open reduction and tunneled suspensory device (ORTSD) fixation with nonoperative treatment for type-III and type-IV AC joint dislocations. The study included sixty patients aged 16 to 35 years with an acute type-III or IV disruption of the AC joint who were randomized to receive ORTSD fixation or nonoperative treatment. They assessed functional outcomes with use of the Disabilities of the Arm, Shoulder and Hand (DASH) as the primary outcome measure.  The Oxford Shoulder Scores (OSS) and Short Form (SF-12) were used as secondary outcome measures at 6 weeks, 3 months, 6 months, and 1 year after treatment.
They found that ORTSD fixation confers no functional benefit over nonoperative treatment at 1 year follow up in patients with type-III or IV disruptions of the AC joint. The patients managed nonoperatively generally recovered faster. There were some patients in the nonoperative treatment group who remained dissatisfied and required delayed surgical reconstruction. The principal reason for dissatisfaction was persistent discomfort, with 1 individual making a specific request for a surgical procedure for cosmetic reasons. The cost of surgical treatment was significantly higher than nonoperative treatment.
The authors concluded that routine surgical treatment for displaced AC joint injuries is not justified.

Chang et al [22] carried out a systematic review and meta-analysis to compare the outcome of operative versus nonoperative management of acute high-grade AC joint dislocation. They found that there was no clinical difference in functional outcome scores between the two groups. Patients in the nonoperative group returned to work earlier. Surgery can be associated with implant complications and postoperative infections.

Many surgical procedures have been described for the treatment of AC joint injuries and no one procedure has been shown to be superior to the other. Procedures for acute injuries include reduction and stabilization of the joint with reconstruction of the ligaments. For delayed surgery, an excision of lateral end of the clavicle is usually carried out in addition to the reduction, stabilization and ligament reconstruction [13].

Conclusion

Although there are some controversies regarding the treatment of AC joint dislocations, there is, however, consensus that type I and type II dislocations should be treated nonsurgically. There is also consensus that type III injuries should be treated conservatively. Occasionally type III injuries may need to be treated surgically when there are persistent symptoms after 3 months and in patients who are heavy manual laborers and overhead athletes.

Type IV and Type V injuries are often treated surgically. Type VI injuries are very rare. There are more and more studies being published which show that surgical treatment offers no functional benefits over nonsurgical treatment. Surgery is more expensive and can be associated with complications. Patients treated conservatively return to work faster. In patients with high-grade dislocations who are treated nonoperatively cosmesis is sometimes a cause for dissatisfaction.

References

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