The joint between the clavicle (collar bone) and the acromion (part of the shoulder blade) is a very common site of wear and tear arthritis (osteoarthitis). By the third decade the disc of cartilage that normally occupies the space between the bones has often started to degenerate.
Xray and MRI findings of arthritis are common after 40, however the majority of these joints do not produce symptoms.
If the AC joint does become symptomatic this can be in isolation or as well as a rotator cuff problem.
Localised superior shoulder pain
Pain at end range of reach
Pain on reach across the body
When the arm is moved it causes compression of the bone ends together as shown below.
Xrays and clinical examination usually confirm the diagnosis and often the first line treatment would be a steroid injection into the AC joint and some studies have shown good sustained relief. This would be usually carried out in conjuction with a course of physiotherapy.
If these conservative measures either fail or are temporary then the surgery may be indicated. Surgery is performed arthroscopically to remove the end of the clavicle. This creates space and stops the ends of the bones from rubbing against each other.
This surgery is usually carried out arthroscopically and as a day case, this reduces the chances of AC joint instability because less ligaments are cut than if the surgery is carried out by an open technique.