Acromioclavicular Joint (ACJ) Osteoarthritis
What is this condition?
This condition occurs due to “wear and tear” of the joint at the end of the collarbone (clavicle) where it meets the acromion (part of the shoulder blade). The joint where the two bones meet is called the acromio-clavicular or AC joint. It is susceptible to wear and tear (osteo-) arthritis due to the large forces transmitted through the joint with every day activities such as lifting objects above shoulder height.
What are the symptoms?
Patients with the condition complain of very localised pain over the end of the collarbone which is typically made worse on movement of the shoulder, particularly movements “high in the arc”. It may also cause pain when rolling onto the affected shoulder at night when in bed.
Who gets this condition?
As it is a degenerative or ‘wear and tear’ condition, it is more common as we get older, and in patients who have manual occupations.
Distal clavicle osteolysis
A subtype of the condition, called distal clavicle osteolysis, can be seen in a younger group of patients; weight-lifters in particular seem to be susceptible to this condition. It is thought that damage to the fibrous disc of tissue within the AC joint causes inflammation followed by absorption of bone at the end of the collarbone. It is treated in much the same way as AC joint osteoarthritis.
What are the treatment options?
A steroid injection into the AC joint can provide very effective pain relief. This is usually guided by ultrasound or x-ray, to ensure that the needle is in the correct place. I would usually recommend this as a first line of treatment since injections are low risk, effective and are useful to confirm the diagnosis. If the injection takes the pain away for a period of time, then even if the pain comes back, we can be reasonably certain that the pain is emanating from the AC joint and not from other problems in the shoulder or the neck.
The definitive surgical procedure for this condition is an operation to remove approximately 5mm of bone from the outer end of the collarbone. This is done under general anaesthetic and can be performed with keyhole surgery. Removing the bone prevents the worn out surfaces from rubbing against each other and usually provides permanent relief from this problem. There is no detrimental effect to removing the bone, as long as not too much is removed.