Osteoarthritis (OA) is the most common form of arthritis and is the one typically associated with aging. According to data compiled by the National Institutes of Health (NIAMS), OA affects more than 20 million Americans.
OA is a disease due to abnormal cartilage metabolism. Cartilage is the connective tissue that lines the ends of long bones. It is tough gristly material consisting of a matrix of proteoglycans and collagen. Within this framework, cells, called chondrocytes, manufacture the matrix.
OA can be a result of genetics (there is often a family history), injury to the joint, and aging.
Weight bearing areas such as the spine, hips, knees, and the base of the thumb are the most common areas affected.
Symptoms of OA include joint pain, swelling, limited range of motion of the joint, and stiffness.
Treatment of this disorder has been largely aimed at symptom reduction. Among the various treatments used have been analgesics (pain killers), non-steroidal anti-inflammatory drugs (NSAIDS), which help reduce swelling and inflammation, injections of corticosteroid and viscosupplements (lubricants), physical therapy, and eventually joint surgery.
Different types of alternative therapies such as chiropractic, acupuncture, herbal medicines, and supplements have also been used.
These treatments, while helpful for symptoms, do nothing to restore cartilage. The end result is that patients end up needing joint replacement.
More recently, there have been attempts to heal cartilage defects. Procedures that have been employed include:
1. Autologous chondrocyte implantation. In this procedure, cartilage cells are removed from a non-weight bearing part of the joint, arthroscopically, grown in a lab, and then re-implanted into the cartilage defect.
2. Mosaicplasty. Multiple cartilage plugs are harvested from a non weight-bearing part of the joint and inserted into the cartilage defect.
3. Microfracture. The cartilage defect has multiple small holes drilled into it to allow blood and a few stem cells escape into the defect and ostensibly grow cartilage.
While these procedures have been used for small isolated cartilage defects- mostly in athletes- none of these procedures has been used extensively for osteoarthritis. In addition, long term data regarding efficacy has been mixed.
So the problem remains... What can be done to restore cartilage?
The most promising approach appears to be the use of autologous stem cell transplantation. In this procedure, bone marrow harvested from the posterior iliac crest of the patient is concentrated to isolate stem cells. Then using a combination of platelet-derived growth factors, subcutaneous fat, and a few other ingredients, the stem cells are reapplied in a regional manner to treat the osteoarthritic joint.
It must be mentioned that the pain of OA is not due directly to cartilage loss. Rather the pain is a result of several factors including irritation of the joint capsule due to bony spurs, called osteophytes, as well as inflammation of the synovium, the lining of the joint.
However, there are significant barriers when it comes to the used of stem cells. First, patients need to be at or near ideal weight. Second, they must be in good physical condition. And lastly there are biomechanical factors that must be considered. For instance, the knee is not just a hinge joint that bends back and forth. There is also a gliding component as well as a rotation component with normal knee range of motion.
The hip is a joint that is capable of significant range of motion. Most osteoarthritis develops in the superior portion of the joint and that also makes the treatment approach difficult since there is a tremendous amount of load strain that accompanies weight bearing.
The upshot is that with cartilage deterioration, there are altered biomechanics that need to be taken into account when treating an osteoarthritic joint, whether it's the knee or the hip.
Limited weight-bearing after the procedure is critical and an early program of directed physical therapy is also required.
Attempts to normalize the abnormal biomechanics are critical.
While the early data for stem cell transplantation looks promising, longer term data, and continued improvements in techniques should improve the long term outlook for patients.
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