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Shoulder

AC Joint Injuries

An acromioclavicular (AC) joint separation, also known as a “shoulder separation”, is an injury where the clavicle (collarbone) separates from the acromion (part of the shoulder blade). This occurs when the ligaments that stabilize the joint are stretched or torn, often due to trauma such as a fall or direct blow to the shoulder.

AC joint separations are common in contact sports and active individuals. Treatment depends on the severity of the separation and can range from rest and physical therapy to surgical repair or reconstruction.

The shoulder is a complex joint made up of three bones:

  1. Clavicle (collarbone)
  2. Scapula (shoulder blade)
  3. Humerus (upper arm bone)

The acromioclavicular (AC) joint is where the clavicle meets the acromion, a bony projection off the front of the scapula. This joint provides stability to the shoulder complex and and supports overhead motion.

The AC joint is stabilized by two sets of ligaments:

  • Acromioclavicular (AC) ligaments: Connect the acromion to the clavicle, providing horizontal stability.
  • Coracoclavicular (CC) ligaments: Connect the clavicle to another part of the scapula (the coracoid process), providing vertical stability. These include the conoid and trapezoid ligaments.

When these ligaments are injured or torn, the joint becomes unstable, and the clavicle may shift out of position and become malaligned.

The most common cause of an AC joint separation is a direct blow to the top of the shoulder, which can occur from:

  • Falls onto the shoulder
  • Sports injuries (e.g., football, hockey, cycling, wrestling, soccer, lacrosse)
  • Falls onto an outstretched arm or elbow

Risk factors include:

  • Participation in contact or high-risk sports
  • Prior AC joint injury

Symptoms of an AC joint separation include:

  • Pain at the top of the shoulder, especially when moving the arm across the body
  • Swelling and bruising
  • Tenderness over the AC joint
  • Visible bump or deformity where the collarbone meets the shoulder
  • Limited shoulder motion
  • Painful popping or clicking with movement

Pain often increases with overhead activities or lifting, and in severe cases, there may be a noticeable step-off or prominence of the clavicle.

Type I:

  • Sprain of AC ligaments
  • No clavicle displacement
  • Ligaments are stretched, not torn

Type II:

  • Complete tear of AC ligaments
  • Partial injury to CC ligaments
  • Mild clavicle displacement

Type III:

  • Complete tear of both AC and CC ligaments
  • Clavicle significantly elevated (25–100% displacement)
  • Often visible deformity

Type IV:

  • Clavicle displaced posteriorly into or through the trapezius muscle
  • Rare and more severe

Type V:

  • Clavicle displaced superiorly >100%
  • Severe soft tissue injury and prominence

Type VI:

  • Clavicle displaced inferiorly under the coracoid or acromion
  • Very rare and usually associated with major trauma

History and Physical Exam

  • Assess mechanism of injury, pain, and range of motion.
  • Palpation of the AC joint may reveal tenderness or deformity.
  • Cross-body adduction of the shoulder may reproduce pain.

Imaging

  • X-rays: Essential for diagnosing and classifying the injury.
    • Special views (e.g., Zanca or stress views) may be used.
  • MRI or Ultrasound: Rarely needed but may help assess soft tissue or rule out other shoulder injuries. May be useful for surgical planning

Nonoperative management is the standard of care for Type I and II injuries and often for Type III, especially in non-athletes or less active individuals.

Rest and Immobilization

  • Sling for 1–2 weeks to allow pain and swelling to decrease.

Ice Therapy

  • Apply ice packs to the shoulder for 15–20 minutes several times a day.

Medications

  • NSAIDs (e.g., ibuprofen) to reduce pain and inflammation.

Physical Therapy

  • Begins after initial pain subsides.
  • Focuses on:
    • Range of motion
    • Shoulder strength
    • Scapular control
  • Gradual return to activity over 4–8 weeks.

Return to Sport/Activity

  • Most patients with Types I–III injuries can return to sports or work within 6–12 weeks.
  • Some residual bump or discomfort may persist, but function is often excellent.

Surgery is considered for:

  • Type IV, V, and VI injuries (due to severity and instability)
  • Failed nonoperative treatment in Type III (ongoing pain or dysfunction)
  • High-demand athletes or manual laborers who require full shoulder function

Surgical Options

Ligament Reconstruction

  • Torn ligaments are reconstructed using grafts (either from the patient or donor tissue).
  • Often combined with fixation techniques (e.g., screws, suture buttons) to hold the clavicle in position.

Fixation Techniques

  • Devices such as tightrope systems, hook plates, or coracoclavicular screws are used to stabilize the clavicle during healing.
  • Some devices may require removal in a second surgery.

Distal Clavicle Resection (Mumford Procedure)

  • Removal of a small portion of the distal clavicle to reduce friction and pain in cases of arthritis or chronic instability.

  • Sling use for 4–6 weeks
  • Physical therapy begins after immobilization period
  • Gradual strengthening and return to function by 3–4 months
  • Full recovery can take 4–6 months but may be up to 1 year

Nonoperative Outcomes

  • Excellent in Types I–II and many Type III injuries
  • Most patients regain full strength and motion
  • Cosmetic bump (elevated clavicle) may remain but is typically painless
  • Some patients may experience mild pain with push-ups or heavy lifting

Surgical Outcomes

  • High success rates in restoring joint stability and function
  • Best for high-grade injuries or failed nonoperative treatment
  • Risk of complications: infection, hardware irritation, graft failure, or stiffness
  • Long-term outcomes generally favorable, though some patients may have residual symptoms

Type III injuries remain controversial:

  • Some surgeons advocate early surgery in athletes or laborers.
  • Others prefer initial nonoperative treatment, reserving surgery for persistent symptoms.

Cosmetic concerns (e.g., prominent bump) alone are not typically an indication for surgery unless associated with pain or dysfunction

 

See a healthcare provider if you:

  • Experience a fall or direct blow to the shoulder followed by pain and deformity
  • Have persistent pain or dysfunction after an AC joint injury
  • Are an athlete or laborer whose symptoms interfere with performance

AC joint separations are common shoulder injuries, often seen in falls and traumas. Severity ranges from mild ligament sprains to complete joint dislocations. Most mild to moderate injuries (Types I–III) respond well to conservative treatment including rest, physical therapy, and gradual return to activity. More severe injuries or failed nonoperative management may require surgical reconstruction.

With appropriate care, most patients regain excellent shoulder function and return to their regular activities, even after high-grade injuries.

At a Glance

Dr. Hasani Swindell

  • Fellowship-Trained Sports Medicine Specialist
  • Board-Certified Orthopedic Surgeon
  • Summa Cum Laude Graduate from the University of Pittsburgh
  • Medical Degree from Columbia University
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