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KembaraXtra-Medicine- Acromioclavicular Dislocation
The acromioclavicular (AC) joint is formed by the articulation between the distal clavicle and the acromion and is located on the anterosuperior aspect of the shoulder. This joint is stabilized primarily by the acromioclavicular (AC) ligaments and the coracoclavicular (CC) ligaments. An acromioclavicular dislocation, also referred to as an AC joint separation, occurs when trauma disrupts these stabilizing structures. The severity of injury can range from a mild ligament sprain to complete rupture of the AC and CC ligaments, with the degree of damage correlating directly with the amount of force applied to the shoulder.
AC joint dislocations most commonly result from direct trauma to the shoulder, such as a blow that drives the acromion inferiorly relative to the clavicle. These injuries are frequently seen in contact sports like football, rugby, lacrosse, and ice hockey, as well as in high-impact motor vehicle accidents. Falls, including falls onto an outstretched hand, can also produce AC joint injuries, though high-energy mechanisms are more likely to result in severe dislocations.
The incidence of AC joint dislocations in the general population ranges from 0.8 to 4.6 per 10,000 people per year, accounting for approximately 10% of shoulder girdle injuries in urban populations. Peak incidence occurs in individuals aged 29 to 40 years, and these injuries are most commonly seen in patients younger than 40 years. Males are more frequently affected than females. No genetic predisposition has been identified.
Clinically, patients typically present with anterior-superior shoulder pain following trauma. Physical examination may reveal visible deformity when compared with the contralateral shoulder, particularly in higher-grade injuries. A classic finding is the “piano key sign,” in which the distal clavicle appears elevated and rebounds when downward pressure is applied. Patients may also have localized tenderness, swelling, and limited shoulder motion. It is essential to assess neurovascular status, evaluate clavicular mobility, and examine surrounding joints and soft tissues for associated injuries.
Diagnosis is often made based on clinical presentation and plain radiographs. Standard imaging includes bilateral anteroposterior views of the AC joints, axillary lateral views, Zanca views, and cross-body adduction views. Upright imaging is preferred, as supine films may underestimate injury severity. The degree of displacement is classified using the Rockwood classification, which categorizes injuries from Type I (ligament sprain) to Type VI (severe inferior displacement of the clavicle). This classification system guides treatment decisions.
Management of AC joint dislocations depends largely on injury severity. Type I and Type II injuries are treated nonoperatively with rest, ice, NSAIDs, sling immobilization, activity modification, and physical therapy. Type III injuries remain controversial; many patients achieve good outcomes with conservative management, though orthopedic consultation is recommended. Surgical intervention may be considered in patients with persistent symptoms despite nonoperative treatment. Type IV, V, and VI injuries typically require surgical management and should be referred promptly to an orthopedic surgeon.
Nonoperative treatment focuses on pain control, immobilization, and gradual rehabilitation to restore range of motion and strength. Operative treatment usually involves open reduction with reconstruction of the coracoclavicular ligaments and repair of the deltotrapezial fascia. There is no single superior surgical technique, and outcomes are generally comparable across methods. Chronic injuries may be managed either conservatively or surgically depending on symptoms and functional impairment.
Most patients managed nonoperatively recover well, regaining near-normal function by 6 weeks and returning to full activity by approximately 12 weeks. Surgical cases require a longer recovery period, often involving 6 weeks of immobilization and return to full activity by 6 months. While many patients are left with a visible deformity at the AC joint, it is often cosmetic and asymptomatic.
Preventive strategies include the use of proper shoulder protective padding in contact sports and education on safe falling techniques in activities with a high risk of falls. Patients and families should be counseled on both nonoperative and operative treatment options, expected recovery timelines, and the possibility of persistent but painless deformity following healing.
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