AC joint injuries

What is an AC joint injury?

The acromioclavicular, or AC, joint is where the collarbone meets the highest point of the shoulder blade. You can feel it as a small bump near the outer end of your collarbone. Ligaments hold the joint together, including a strong pair that run from the collarbone down to the shoulder blade.

An AC joint injury is often called a shoulder separation. It is different from a shoulder dislocation, where the ball comes out of the socket. Here, the ball and socket are fine. The ligaments at the collarbone are what stretch or tear.

It usually comes from a direct fall onto the point of the shoulder, as in cycling, skiing, hockey, or football. You will often feel pain right at that spot, and you may see a new bump.

What do the grades mean?

Doctors use the Rockwood grades, from I to VI. A shoulder panel agreed the system is valid when used as modified by ISAKOS, a surgical society (Rosso, 2021).

• Grade I: the ligaments are stretched, and the joint stays in line.
• Grade II: the joint ligaments tear, and the collarbone shifts a little.
• Grade III: the ligaments that hold the collarbone down also tear, so the joint comes fully apart.
• Grade IV: the collarbone is pushed backward into or through the muscle behind it.
• Grade V: the collarbone sits much higher than normal, with more muscle torn away.
• Grade VI: the collarbone is pushed down, under the bone below it. This is rare.

Grade III is sometimes split further, based on how stable the shoulder blade is. X-rays are usually enough to make the diagnosis. The panel agreed on a true front-on view or a view of both sides. Your doctor will also check whether the joint slides front to back, using a test that brings your arm across your body (Rosso, 2021).

Can it get better without surgery?

Grades I and II are usually treated without surgery. Grades IV and VI are often treated with surgery, and grade V is debated.

Grade III is where most of the debate sits. A Cochrane review of six trials and 357 people, most of them young adults, compared surgery with non-surgical care for acute injuries. There was no clear gain from surgery in function, return to former activities, or quality of life at one year. People treated without surgery recovered earlier. The evidence was low quality, and there was too little data to compare injury grades (Tamaoki, 2019).

Non-surgical care often means a sling for comfort, then motion and strength work. A newer trial of 124 people with grade III or V injuries compared physical therapy with hook plate surgery. Those treated without surgery did better at 3 months. There were no significant differences at 6, 12, or 24 months. However, 18% of those assigned to non-surgical care had surgery within 19 months (Boström Windhamre, 2022).

So non-surgical care works for many people, and it does not work for everyone. The bump often stays, and some people have lasting pain or weakness.

When is reconstruction considered?

Surgery is often discussed for:

• Higher grades, where the collarbone has moved far out of place
• Grade III injuries that still hurt or limit you after a real trial of therapy
• Overhead athletes and heavy laborers who need more from the shoulder
• Long-standing pain and instability

The panel set the line between acute and chronic injuries at 3 weeks. For acute injuries, it favored arthroscopically assisted repair with a strong suture device. For chronic injuries, it suggested rebuilding the ligaments with a tendon graft (Rosso, 2021).

For high-grade chronic injuries, a review of 27 studies and 590 patients compared three types of surgery. Complication rates were similar, at 15% to 17%, and failure rates were 5% to 8% (Borbas, 2019).

What are the risks of surgery?

Risks include infection, hardware problems, loss of the position over time, fracture of the collarbone or nearby bone, stiffness, and ongoing pain. In the Cochrane review, adverse events occurred in 45 of 168 people after surgery and in 16 of 174 without it. That evidence was very low quality, and many problems came from older devices that are rarely used today (Tamaoki, 2019). No surgeon can promise a certain outcome.

Should I get a second opinion?

It can help, especially if you were told you need surgery for a grade III injury, or if months of therapy did not help. Here’s how a second opinion works.

Where can I see Dr. Pareek?

Dr. Pareek sees shoulder patients at HSS in New York and at HSS in New Jersey. Bring any X-rays, MRI images, and reports you already have.

What does recovery look like?

These are typical ranges. Your surgeon’s plan comes first, and recovery varies from person to person.

• Weeks 0-2: Calm the shoulderWith or without surgery, many people use a sling for comfort or protection, along with ice and gentle hand and elbow motion.
• Weeks 2-6: Regain motionNon-surgical care usually moves on to motion and light therapy as pain allows. After surgery, the sling often stays on longer and lifting is limited.
• Weeks 6-12: Start strengthTherapy adds strength for the shoulder blade muscles and the rotator cuff. People treated without surgery are often ahead at this stage.
• Months 3-6: Build powerHeavier lifting and sport drills build up over time, as your plan allows.
• Months 6 and beyond: Return to full activityContact sport and heavy overhead work return once strength and comfort allow. After reconstruction this may take longer. These are typical ranges, and your surgeon's plan governs.

Sources

1. Tamaoki MJ, et al. Surgical versus conservative interventions for treating acromioclavicular dislocation of the shoulder in adults. Cochrane Database Syst Rev 2019;10:CD007429.
2. Boström Windhamre H, et al. No difference in clinical outcome at 2-year follow-up in patients with type III and V acromioclavicular joint dislocation treated with hook plate or physiotherapy: a randomized controlled trial. J Shoulder Elbow Surg 2022;31:1122-1136.
3. Rosso C, et al. High degree of consensus achieved regarding diagnosis and treatment of acromioclavicular joint instability among ESA-ESSKA members. Knee Surg Sports Traumatol Arthrosc 2021;29:2325-2332.
4. Borbas P, et al. Surgical management of chronic high-grade acromioclavicular joint dislocations: a systematic review. J Shoulder Elbow Surg 2019;28:2031-2038.