AC joint osteoarthritis can reduce the mobility of the shoulder girdle, which consists of the two clavicles and the two shoulder blades as well as the connecting joints and muscles.
The two pairs of joints that are part of the shoulder girdle are the sternoclavicular joint and the acromioclavicular joint on each side.
The AC joints are particularly mobile and important. Unfortunately these are also the ones that tend to develop shoulder arthritis in the late 30’s or mid 40’s. At that time they are prone to develop a shoulder bone spur as part of osteoarthritis. This can cause sharp pain feeling like there are internal small knives in the shoulder. This is osteoarthritis pain. If they point down in the direction of the supraspinatus tendon, this can become the source of a rotator cuff injury and eventually a rotator cuff tear. In the presence of a congenital shoulder impingement this is particularly painful and devastating.
These cases need the attention of an orthopedic surgeon who can do a shoulder arthroscopy and clean out the spurs. Early detection by clinical examination and MRI scan are essential to prevent disaster (a supraspinatus tendon tear).
In severe cases of AC joint arthritis shoulder surgery is required, where the AC joint is surgically removed by doing a shoulder decompression. This consists of cutting away the distal 1/3 of the clavicle (collar bone) and removal of a wedge of the acromion. This procedure often has to be done as an “open procedure” (meaning through a large incision) although most of the time shoulder surgeons first attempts to do this procedure by arthroscopy (through “pinhole surgery”).
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