ACROMIOCLAVICULAR (AC) JOINT
1. Anatomy and Function
– the AC Joint is where the Clavicle & Acromion meet. This allows the Clavicle to provide support to the Scapula, connecting it to the Ribcage via the Sternum at its medial end. The Clavicle rotates at the AC Joint when the arm is elevated.
2. Injury –
A) AC Separation – this occurs when there is a fall, landing on the
point at the top of the shoulder (Acromion). The Acromion is driven downward, yet the Clavicle remains in its elevated position, causing the AC Joint to Separate or Dislocate. There are 3 grades of AC Separation:
Grade 1 – the Acromioclavicular ligaments are partially torn, causing pain and weakness. The AC Joint is not mal-aligned. X-rays are normal.
Grade 2 – the Acromioclavicular ligaments are completely torn, but the Coracoclavicular ligaments are not injured. The AC joint is partially mal-aligned. X-rays show the distal Clavicle is elevated by 50% of its thickness above the Acromion.
Grade 3 – both the Acromioclavicular and the Coracoclavicular
ligaments are completely torn. The AC joint is completely separated. The x-rays show the distal Clavicle completely above the Acromion. There is
a noticeable bump on the top of the shoulder due to elevated distal Clavicle.
B) AC Arthropathy – the AC Joint has become degenerated and the
Cartilage lining has been worn away due injury or wear and tear. The joint space narrows and two bones rub against one another causing spur
formation, pain and weakness.
A) AC Separation – the treatment will depend on the Grade:
Grade 1 – simple rest, NSAIDs and rehab will usually be enough
to resolve the pain and weakness over 4 to 6 weeks.
Grade 2 – same as Grade 1 except sometimes an injection of Cortisone is needed. The other difference is these may progress to AC Arthropathy (see above).
Grade 3 – this is a somewhat controversial area in Orthopedics. The current thinking is that Surgery is needed in a Dominant arm, young and active
patient. The procedure is the Modified Weaver-Dunn Reconstruction. A six inch incision is made over the end of the Clavicle and one-half inch of bone is removed from the end. This eliminates friction at the AC Joint. To stabilize the
end of the Clavicle, a tether of heavy suture is passed around the Coracoid process and tied over the Clavicle.This takes about 2 hours and requires an overnight stay at the surgery center. Recovery involves a shoulder
immobilizer for 6 weeks and 2 months of physical therapy. Full activity is resumed at 3 to 4 months. In a non-dominant arm, sedentary individual the
decision to treat with rest and rehab will probably be enough to allow full recovery in 2 to 3 months. If a patient is not happy with the results at that point, then a Modified Weaver-Dunn Reconstruction is still an option.
B) AC Arthropathy – a Cortisone injection into the joint will provide
Relief for 3 to 6 months. Arthroscopic Distal Clavicle is the definitive treatment. This is done as an outpatient procedure and is often simultaneous with other procedures on that shoulder. It takes about 30 minutes to do and requires 2 or 3 portals. Recovery requires a sling for a few days and a month of therapy. Full Activity is resumed in 6 weeks.