AC Joint Injury: Understanding, Classification, and Treatment

How Do You Treat an AC Joint Injury?

Treatment for an AC joint injury typically involves a structured approach ranging from conservative management for lower-grade sprains to surgical intervention for severe separations, focusing on pain reduction, restoring range of motion, and regaining strength to facilitate a safe return to activity.

Understanding the AC Joint and Injury Mechanism

The acromioclavicular (AC) joint is a critical articulation in the shoulder complex, formed by the distal end of the clavicle (collarbone) and the acromion process of the scapula (shoulder blade). It is stabilized by the AC ligaments (superior and inferior) and, more significantly, by the coracoclavicular (CC) ligaments (conoid and trapezoid), which connect the clavicle to the coracoid process of the scapula.

An AC joint injury, often referred to as a shoulder separation, occurs when these ligaments are stretched or torn. The most common mechanism of injury is a direct blow to the top of the shoulder, such as falling directly onto the shoulder or being tackled in sports. Less commonly, it can result from a fall on an outstretched hand.

Classifying AC Joint Injuries

AC joint injuries are graded based on the severity of ligamentous damage and the degree of clavicular displacement relative to the acromion. The Rockwood classification system is widely used:

• Grade I: A mild sprain of the AC ligaments with no tearing and no displacement of the clavicle. The AC joint remains stable.
• Grade II: A complete tear of the AC ligaments, but the CC ligaments remain intact or only partially sprained. There is a subluxation (partial dislocation) of the clavicle, often visible as a slight bump.
• Grade III: Complete tears of both the AC and CC ligaments. This results in significant superior displacement of the clavicle and a noticeable deformity or "bump" on top of the shoulder.
• Grade IV: Similar to Grade III but with posterior displacement of the clavicle into or through the trapezius muscle. This is a rare and more severe injury.
• Grade V: A severe Grade III injury with significant superior displacement of the clavicle (often 100-300% of normal), causing the skin to tent. All ligamentous support is disrupted.
• Grade VI: Inferior displacement of the clavicle, dislocated beneath the coracoid process. This is extremely rare and usually results from severe trauma.

Accurate diagnosis, often involving physical examination and X-rays (sometimes with weight-bearing views), is crucial to determine the appropriate treatment strategy.

Initial Management: The Acute Phase

Regardless of the grade, initial management focuses on pain control and protecting the joint from further injury.

• Rest: Avoid activities that exacerbate pain or stress the AC joint.
• Ice: Apply ice packs to the injured area for 15-20 minutes every 2-3 hours to reduce pain and swelling.
• Compression: While not always practical for the AC joint itself, a sling can provide compression and support.
• Elevation: Keep the arm elevated to help reduce swelling.
• Pain Management: Over-the-counter non-steroidal anti-inflammatory drugs (NSAIDs) like ibuprofen or naproxen can help manage pain and inflammation. In some cases, a physician may prescribe stronger pain medication.
• Immobilization: A sling or shoulder immobilizer is often used for the first 1-3 weeks, especially for Grade II and III injuries, to provide support and allow initial healing. The duration depends on the injury severity and individual comfort.

Conservative Treatment for Low-Grade Injuries (Grades I-III)

The vast majority of AC joint injuries (Grades I, II, and many Grade III) are successfully treated non-surgically. The rehabilitation process is phased and progressive.

Phase 1: Pain and Inflammation Control (Acute Phase)

• Goal: Reduce pain and swelling, protect the healing tissues.
• Strategies: Continued use of ice, NSAIDs, and sling immobilization as needed. Gentle, pain-free passive range of motion (PROM) exercises may be introduced once acute pain subsides.

Phase 2: Restoring Range of Motion and Early Strengthening

• Goal: Regain full, pain-free shoulder range of motion and initiate muscle activation.
• Strategies:
  • Pendulum exercises: Gentle, gravity-assisted movements to promote blood flow and mobility.
  • Assisted range of motion (AROM): Using the uninjured arm or a stick to gently move the injured arm through its range.
  • Scapular stabilization exercises: Focus on activating and strengthening the muscles that control the scapula (e.g., serratus anterior, rhomboids, lower trapezius). Examples include scapular squeezes, prone T's, and wall slides.
  • Isometric exercises: Gentle contractions of shoulder muscles without movement (e.g., pushing against a wall).

Phase 3: Progressive Strengthening and Proprioception

• Goal: Build strength, endurance, and neuromuscular control in the shoulder complex.
• Strategies:
  • Rotator cuff strengthening: Exercises for internal and external rotation (e.g., using resistance bands or light dumbbells).
  • Deltoid strengthening: Light raises (front, lateral, bent-over).
  • Upper back strengthening: Rows, pull-aparts with bands.
  • Proprioceptive exercises: Activities that challenge balance and coordination of the shoulder (e.g., stability ball push-ups, rhythmic stabilization drills).
  • Core stability: Essential for overall shoulder mechanics.

Phase 4: Return to Activity/Sport

• Goal: Safely return to sport-specific or activity-specific demands.
• Strategies:
  • Sport-specific drills: Gradually reintroduce movements required for the individual's sport or occupation (e.g., throwing, overhead lifting, pushing).
  • Plyometrics: For athletes, introducing low-impact plyometric exercises to prepare for dynamic movements.
  • Gradual increase in intensity and duration: Progressively challenge the shoulder under controlled conditions.
  • Emphasis on proper technique: Reinforce correct biomechanics to prevent re-injury.

The timeline for conservative treatment can range from 6 weeks for Grade I injuries to 3-6 months for Grade III injuries, depending on individual healing and adherence to rehabilitation.

Surgical Considerations for High-Grade Injuries (Grades IV-VI)

While less common, surgical intervention may be considered for higher-grade injuries (typically Grade IV, V, and VI, and some symptomatic Grade III injuries in specific populations like overhead athletes or heavy laborers).

• Indications for Surgery:

  • Significant cosmetic deformity and persistent pain in Grade III.
  • High-grade dislocations (IV, V, VI) where conservative management is unlikely to restore function.
  • Failure of conservative treatment for Grade III injuries.
  • Young, active individuals with high functional demands.

• Surgical Procedures: The goal of surgery is to reduce the clavicle back into its anatomical position and stabilize the joint. Common techniques include:

  • Direct AC joint repair/reconstruction: Repairing or reconstructing the torn AC ligaments.
  • Coracoclavicular (CC) ligament reconstruction: Most common, using grafts (autograft or allograft) or synthetic materials to reconstruct the CC ligaments, which provide primary vertical stability.
  • Hook plate fixation: A temporary plate that hooks under the acromion to hold the clavicle in place while ligaments heal, later removed.
  • Screws or sutures: Used to temporarily stabilize the joint.

• Post-Operative Care: Surgical treatment is followed by a structured rehabilitation program, often more conservative initially than non-surgical rehab. This typically involves:

  • Immobilization: Sling for 4-8 weeks.
  • Early passive motion: Carefully initiated under therapist guidance.
  • Gradual progression: Similar to conservative rehab, but with stricter timelines to protect surgical repairs. Full recovery can take 6-12 months.

Rehabilitation Principles: A Phased Approach

Regardless of whether treatment is conservative or surgical, the principles of rehabilitation remain consistent:

1. Protect the Healing Tissues: Avoid activities that stress the injured joint.
2. Restore Pain-Free Range of Motion: Gradually increase mobility.
3. Regain Strength and Endurance: Strengthen the muscles supporting the shoulder.
4. Improve Proprioception and Neuromuscular Control: Enhance joint awareness and stability.
5. Return to Functional Activities: Progressively reintroduce daily, occupational, and sport-specific movements.

Throughout all phases, listening to your body and avoiding pain are paramount. A qualified physical therapist or athletic trainer is essential to guide this process, tailoring exercises to individual needs and progress.

When to Seek Professional Help

It is crucial to seek medical attention if you suspect an AC joint injury. A physician can accurately diagnose the grade of injury and recommend the most appropriate treatment plan. Consult a healthcare professional if you experience:

• Severe pain or inability to move your arm.
• Visible deformity or a prominent "bump" on your shoulder.
• Numbness or tingling in your arm or hand.
• Symptoms that worsen or do not improve with initial rest and ice.

Prevention and Long-Term Outlook

While not all AC joint injuries are preventable, strengthening the surrounding musculature (deltoids, trapezius, rotator cuff) and practicing proper fall techniques (e.g., in sports) can help.

The long-term outlook for AC joint injuries is generally good. Most individuals, even with Grade III injuries treated conservatively, can return to full activity with minimal long-term issues. Some may experience a persistent cosmetic deformity (the "bump") and occasional mild pain with certain activities, especially with weather changes or direct pressure. Surgical outcomes are also generally positive, though they involve a longer recovery period. Adherence to a comprehensive rehabilitation program is the most critical factor in achieving a successful outcome.