Osteoarthritis of the shoulder is relatively uncommon when compared to that affecting the knee and hip. It is seen, more often, to occur as a pathological condition resulting from a trauma such as a fracture of the upper part of the arm bone (proximal humerus). It can also be seen as a result of a chronic rotator cuff tear when it is termed as Rotator Cuff Arthropathy which is a distinct entity.
Patients are commonly middle aged or elderly and have pain which worsens over a period of time. Pain in the shoulder can limit shoulder movement and also cause sleep deprivation. The pain has been described as gnawing similar to that of a tooth ache. It can also cause restriction of movement and can be misdiagnosed as frozen shoulder. The difference becomes more apparent though an x-ray.
- X-rays reveal evidence of joint destruction and bone spurs at the margins. There will also be tissue hardening and reduction in the joint space
- CT scans are useful to see how much of the joint is involved and to see if there are any glenoid wear changes.
- An MRI may also be recommended to check if there is any damage to the rotator cuff musculature (the tendons in the shoulder socket that connect the shoulder socket to the upper arm bone) which is extremely important in deciding the type of joint replacement prosthesis required
Initial treatment is in the form of medication for pain killers and physical therapy to try and control the pain. This may provide relief initially, but the pain gradually worsens as the arthritis progresses with time. Surgery may be recommended in the form of joint replacement, depending on several factors which the surgeon takes into account.
In mild and moderate cases where the bone is not damaged, patients may be recommended a resurfacing of the humeral head (Ball part of the upper arm bone and socket joint). Only the articular cartilage (the cartilage around the shoulder socket) is replaced by a metallic cup. Results are fairly good with this procedure.
Patients may also be recommended to undergo a hemiarthroplasty which is slightly more extensive than the resurfacing procedure if the bone is undamaged and suitable to undergo the same. In this procedure the metallic cup attached to the shoulder socket has connecting stem and may be attached to the bone with or without cement.
In cases where evidence of wear and tear of the glenoid (socket part of the ball and socket joint) is found, patients may be advised to undergo a total shoulder replacement where both the ball and socket part of the joint are replaced. The ball, generally made of metal and the socket usually made of plastic, is secured to the bone using bone cement. For all the above mentioned procedures, it is extremely vital to have a normal cuff for good results.
In cases where the arthritis is mainly because of a chronic rotator cuff tear, the humerus will have some amount of damage mainly above the humeral head due to erosion against the under-surface of the shoulder socket. These patients typically have poor shoulder function due to the damaged cuff. They may continue to have good passive range of movement. These patients are generally recommended to undergo a reverse total shoulder replacement. In this procedure, the normal ball and socket anatomy are reversed. Hence using a special prosthesis, the shoulder socket is replaced with ball type prosthesis and the upper arm head is replaced with socket type prosthesis. This treatment procedure prevents the upward migration of the humeral head owing to the structural design of the prosthesis. Movement is fairly satisfactory following this surgery however; long term results of this particular procedure are still awaited. Short term results are promising.
There are some special problems with this type of procedure. Fracture of the acromion, (the highest part of the shoulder bone), and glenoid notching (shoulder socket) have been noted. The significance of this is still not known and is under study.