Cartilage Replacement

Bend the top of your ear forward, and you can feel something flex and spring back. It is cartilage, a dense bluish-white connective tissue found in the ear, nose, ribs, and other parts of the skeletal system, that acts to cover and cushion the points at which bones meet – at the joints.

Cartilage is made of collagen, a fibrous protein also found in various forms in bone and hair. Woven around a network of bushy strands of proteoglycans (sugar-carrying proteins), collagen acts as a kind of scaffolding, giving the cartilage its strength. The proteoglycans trap water molecules and provide the cartilage with its flexibility and cushioning properties.

When cartilage begins to wear thin, as it does in osteoarthritis, the bones are left exposed and raw. With each movement, one end of the bone rubs against another, causing the bone to fragment and erode. The joint loses its ability to bend easily and absorb the impact of normal movement. You will feel this deterioration in localized pain and stiffness. It is this process that leads to serious disability.

In most cases, when bone destruction – and the consequent pain -- become relentless, the usual course is to consider total joint replacement. Each year, approximately 150,000 people in this country get new hips, another 240,000 replace knees, and countless others exchange elbows, ankles, shoulders, and even finger joints. In the past 15 years, joint replacement surgery has become remarkably safe and effective. Despite the fact that joint replacement can be quite effective in relieving pain and restoring function, it can also be expensive. Joint replacement is simply not for everyone.

Certain medications, specifically a drug called Synvisc can be injected into the joint to enhance and restore some of the properties of synovial fluid, which are compromised in osteoarthritis. Known as viscosupplementation, this type of agent works to lubricate, protect and cushion the joint. When successful, it relieves pain and improves mobility in osteoarthritic joints. However, while damaged or deteriorating cartilage can be repaired, seldom is the solution practical for the long-term. Consequently, researchers are looking into alternative, less invasive and extensive procedures.

One procedure, called cartilage regeneration, has been used to correct knee problems in Sweden, and is now available in the United States. In this procedure, the doctor first does a biopsy and extracts a small sample of healthy cartilage tissue. That tissue is then sent to a lab where it reproduces. The lab returns a vial containing 12 million cartilage cells. During a second surgery, the damaged cartilage is removed and the new cells are injected into the joint site. There they grow and eventually resurface the bones.

Usually, patients recover within six months of the cartilage regeneration operation. In that time, it is important that a patient keep all weight off his knee. That usually means using crutches. In addition, weeks of physical therapy and rehabilitation are needed to help rebuild strength in the area.

Cartilage regeneration seems most appropriate for people under age 55 whose cartilage deterioration is localized and due to a genetic defect or sports injury. Although this procedure seems promising, so far, only 250 have been performed worldwide.

Another very promising option involves replacing the eroded cartilage with such synthetic alloys as ground diamonds, ceramics, and electrically charged coverings. Researchers in Minnesota are currently experimenting with liquid polyurethane. Using arthroscopy to scrape damaged cartilage from the bone surfaces – at the knee, for example they apply the liquid polyurethane on raw bone. Once applied to the bony surface, the substance dries, leaving a hard, smooth, resilient coating upon which the joint glides with no apparent pain or loss of function.

Although the use of synthetic cartilage replacement has been used only in animal studies, early results seem to hold out great promise for success in human joints. So far there seems to be little risk of rejection, no significant side-effects or related inflammation.

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