The acromio clavicular joint (AC joint) is the joint between your clavicle and your scapula at the top of the shoulder.
It is often injured in sport and in falls. The common injury is the severe shoulder charge in hurling and football. The ligaments that hold the joint in place get torn and then the end of the clavicle pops up.
- Type 1: Minor sprain of the acromioclavicular ligament, intact joint capsule, intact coracoclavicular ligament, intact deltoid and trapezius
- Type 2: Rupture of the acromioclavicular ligament and joint capsule, sprain of the coracoclavicular ligament but intact coracoclavicular interspace, minimal detachment of the deltoid and trapezius
- Type 3: Rupture of the acromioclavicular ligament, joint capsule, and coracoclavicular ligament; elevated clavicle (≤100% displacement); detachment of the deltoid and trapezius
- Type 4: Rupture of the acromioclavicular ligament, joint capsule, and coracoclavicular ligament; posteriorly displaced clavicle into the trapezius; detachment of the deltoid and trapezius
- Type 5: Rupture of the acromioclavicular ligament, joint capsule, and coracoclavicular ligament; elevated clavicle (>100% displacement); detachment of the deltoid and trapezius
- Type 6 (rare): Rupture of acromioclavicular ligament, joint capsule, and coracoclavicular ligament; the clavicle is displaced behind the tendons of the biceps and coracobrachialis
Most patients with Type 1 and 2 injuries do well with some rest and time and can generally return to sport after 4 weeks or less. Types 4, 5 and 6 do require surgery to relocate the joint. There is some discussion on whether the relatively common Type 3 injuries should be treated by surgery. Studies have reported equal outcomes with and without surgery and surgery is not without its complications. Probably the biggest problem with Type 3 injuries is the cosmetic appearance of the injury with a sometimes unsightly very prominent clavicle. It can also result in forward rotation of the scapula and winging. This can lead to a decrease in the level of performance in high demand athletes. Any injury to any joint can of course lead to arthritis in the long term.
There is the option to perform an arthroscopic (keyhole) repair of the AC joint. http://www.arthrex.com/shoulder/ac-dog-bone-technique. A heavy stitch is placed through the clavicle and the coracoid to hold these bones closer together while healing takes place. If this is done in the first 2 weeks after the injury there is a good chance that the ligaments will heal while the joint is kept in place. It can also be performed later and in this situation the repair is augmented with a hamstring tendon graft around the clavicle and the coracoid.
There may not be a perfect result with surgery and there may still be some slight sub luxation of the joint. The clavicle or the coracoid bones may break because of the hole that is drilled through them. The stitch material may be prominent beneath the skin.
Arthroscopic keyhole repair of the AC joint injury is an option that can be considered in an individual case.