AC joint disruption​

The acromioclavicular (AC) joint is the joint at the top of the shoulder where the acromion (part of the scapula or shoulder blade) meets the clavicle (collarbone). AC joint disruption, also known as an AC joint separation or sprain, occurs when the ligaments that hold these two bones together are damaged or torn, leading to a dislocation or separation of the joint.

Causes

AC joint disruption is most commonly caused by:

• Direct trauma: This usually happens from a fall directly onto the shoulder, often in sports like football, rugby, or cycling.
• Indirect force: A fall on an outstretched hand can transmit force up the arm and into the shoulder, leading to separation.

Classification

AC joint injuries are typically classified into six types based on the severity and extent of the damage:

• Type I: Mild injury with no visible displacement. The ligaments are stretched but not torn.
• Type II: Partial tear of the AC ligament, with slight displacement of the joint.
• Type III: Complete tear of both the AC ligament and the coracoclavicular (CC) ligament, with a noticeable displacement of the joint.
• Types IV, V, VI: More severe injuries involving significant displacement or abnormal positioning of the clavicle, often requiring surgical intervention.

Symptoms

Symptoms of AC joint disruption may include:

• Pain at the top of the shoulder: Especially when moving the arm or pressing on the joint.
• Swelling and bruising: Around the AC joint.
• Visible deformity: In more severe cases, a noticeable bump or “step” may be seen where the clavicle has been displaced.
• Limited range of motion: Pain may restrict shoulder movement, particularly lifting the arm.

Diagnosis

Diagnosis is typically made through:

• Physical examination: A healthcare provider will assess pain, range of motion, and joint stability.
• Imaging: X-rays are commonly used to determine the extent of the separation and to classify the injury. In some cases, an MRI may be used to evaluate associated soft tissue damage.

Treatment

Treatment depends on the severity of the injury:

• Non-surgical treatment: For Types I and II, rest, ice, pain relievers, and physical therapy are usually sufficient. A sling may be used temporarily to immobilize the shoulder.
• Surgical treatment: For Types III and above, or for athletes who require full shoulder function, surgery may be recommended to stabilize the joint and repair the ligaments.

Recovery

Recovery time can vary:

• Non-surgical: Most patients recover within a few weeks to a couple of months, depending on the severity of the injury and adherence to rehabilitation.
• Surgical: Recovery may take several months, with a focus on physical therapy to restore strength and range of motion.

In summary, AC joint disruption is a common shoulder injury that ranges from mild ligament sprains to severe separations requiring surgical repair. Early diagnosis and appropriate treatment are key to ensuring optimal recovery and return to normal activities.