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Shoulder arthritis refers to loss of cartilage on the surface of the ball (humeral head) and the socket (glenoid) of the shoulder glenohumeral joint. The two bones rub against each other and produce pain, stiffness and difficulty moving an arm.
Types and Causes of Shoulder arthritis
Osteoarthritis (OA) – also called degenerative joint disease (DJD), is the “wear and tear” condition of the joint commonly due to old age. OA is characterized by loss of cartilage, bone spurs (osteophytes) and no major inflammation (Fig. 1).
Fig. 1: Osteoarthritis of the main shoulder joint. Click on image to see a larger version on Alila Medical Media website where the image is also available for licensing.
Rheumatoid arthritis (RA) – Inflammation of the synovium – the membrane that encloses the joint and contains lubricant fluid. Inflammation brings in the cells of the immune system whose inflammatory chemicals damage and destroy the joint. It’s not clear how RA starts but genetic predisposition together with infection of the joint are likely to be among the causes.
Rotator cuff arthropathy or cuff tear arthropathy (CTA) – Shoulder arthritis as a result and in a setting of rotator cuff tears. Rotator cuff muscles hold the ball and the socket together and prevent the humeral head from moving out of the socket when the person raises an arm. In people with torn rotator cuff, the head of the humerus moves upwards and rub onto the acromion. This causes damages to the covering cartilage and eventually arthritis. Combination of cuff tear and arthritis is a devastating condition that seriously compromises function of the shoulder.
Post-traumatic arthritis – arthritis that develops after physical injury to the joint.
Chondrolysis – sudden loss of cartilage that happens occasionally after a shoulder surgery, commonly seen in association with infusion of local anesthetics into the joint for pain management.
Treatments
Non-surgical treatments include shoulder exercises and anti-inflammatory medications.
Surgical treatments include a variety of procedures :
1. Total shoulder replacement surgery : the arthritic humeral head is replaced with a metal ball on a stem that fits inside the humerus, the socket is replaced with a plastic component made of high density polyethylene.
Fig. 2: Total shoulder replacement procedure. Click on image to see a larger version on Alila Medical Media website where the image is also available for licensing.
2. Ream and Run Arthroplasty – a modification of total shoulder procedure above. The metal ball replaces the humeral head but the socket is simply shaped, smoothed to fit the ball and left to heal. No plastic component used. With time, the body grows a cartilage layer on top of the socket. This procedure is recommended for younger and more active individuals.
3. Reverse total shoulder or Delta total shoulder replacement – This is indicated for people with rotator cuff arthropathy (see types of shoulder arthritis above). This procedure reverses the positions of the prostheses : the metal ball is now fixed on the socket and the plastic component is fixed in place of the humeral head. This topic is covered in the next article about reverse total shoulder replacement.
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