What is an AC joint separation?
The acromioclavicular (AC) joint serves to connect the clavicle (collarbone) to the tip of the scapula (shoulder blade) known as the acromion. The AC joint is held together by strong ligaments that prevent the shoulder from collapsing during shoulder motion. An AC joint injury is quite common and is usually caused by direct trauma to the shoulder, such as blunt force during sports or a hard fall directly on the shoulder. The result of a shoulder separation is the clavicle separating from the scapula, which can include injury to the muscles, tendons and ligaments surrounding it. Injuries of the AC joint can range in severity from a mild sprain to a complete separation, leading to pain and deformity. Although there is great discomfort with an AC separation, it will usually heal on its own within 12 weeks.
What are the symptoms of an AC joint injury?
Injuries to the AC joint are graded on a 1-6 scale based on severity. No matter the grade of the injury, shoulder pain is the hallmark symptom of an AC joint injury. Grades 1-3 are the most common, and symptoms often include minor swelling, tenderness, and possible mild deformity. Grades 4-6 are very rare and are usually the result of a high-energy trauma. These typically cause severe pain, visible deformity, and inability to lift the arm.
- Grade 1 – Mild separation that involves a sprain of your AC ligament. Does not move your clavicle and looks normal on X-rays. This is the most common type of injury to the AC joint
- Grade 2 – Partial separation in which there is a tear of the AC ligament and a sprain of the coracoclavicular (CC) ligament. Slight elevation of distal clavicle (< 25% displacement) on x-rays
- Grade 3 – Complete separation of the joint that completely tears both your AC and CC ligaments. Usually, the displacement is obvious on clinical exam. Elevation of distal clavicle (25-100% displacement) on x-rays
- Grades 4, 5, 6 – Very rare. Treated surgically because of the severe disruption of all the ligamentous support for the arm and shoulder
How is an AC joint separation diagnosed?
In order to confirm the diagnosis of an AC joint separation, Dr. Potts will perform a comprehensive history and physical examination. AC joint injuries are usually diagnosed with x-rays, although MRI imaging may also be ordered to rule out additional injuries to the shoulder.
How are AC joint injuries treated?
Grade 1-2 injuries of the AC joint are generally treated conservatively with a sling followed by physical therapy to restore strength, function and mobility to the shoulder. Treatment also includes rest, ice, activity modification, and anti-inflammatory medications.
Grade 3 injuries are controversial and can be treated effectively with either surgery or conservative treatment programs. Dr. Potts will evaluate the individual and determine the optimal treatment based on age, activity level, and severity of the injury.
Grade 4-6 AC joint injuries, as well as those who fail conservative treatment, typically require surgical intervention for the best possible outcome. Dr. Potts generally uses minimally invasive shoulder arthroscopy to reconstruct the AC joint using a ligament graft and sutures to restore stability.