Grow your new joint

Doctors have developed an implant that allows patients to ‘grow their own’ joints and avoid having replacement surgery.

The implant, roughly the size and shape of a mint imperial sweet, has been designed to help replace small joints in the hands and feet.

It is made from a sugar-based material which encourages the patient’s own tough fibrous tissues to form a new kind of joint, providing a cushioning barrier between the bones.

When the new joint has formed, the implant gradually breaks down and is carried away in the blood stream — it is, in effect, the world’s first biodegradable joint implant.

Research on more than 200 patients with osteoarthritis and rheumatoid arthritis showed that it significantly improved both movement and pain. Arthritis affects around nine million men and women in the UK, with symptoms including pain and stiffness. The condition causes the smooth cartilage that lines the ends of bones and cushions the joint to be become damaged or destroyed. This can result in the bones of the joint rubbing together, causing pain and swelling. And as cartilage does not regenerate well, any damage is difficult to treat.

One current surgical option for severe cases is to remove the ends of the bones and then insert an artificial replacement joint made from low-friction man-made material, such as ceramic, plastic or metal. However, these artificial joints can cause wear on the surrounding bones and tissue, and may need to be replaced within ten years.

The common surgical treatment for joints in the hand, wrist and foot involves fusing the two bones of the joint together, but this can result in very restricted movement.

The new joint, made by Finnish researchers, is a soft porous material with a consistency similar to that of a sponge. The circular disc-like device, which comes in various sizes up to 18mm in diameter and 4.5mm thick, to fit different joints, is made from polylactide, a material manufactured from corn starch or cane sugar.

In a 30-minute procedure, the implant is inserted into the space between the two bones of the joint, where the missing or damaged cartilage normally sits. Here, it acts as a spacer to stop the two bones rubbing against each other. Once in place, the implant — called the RegJoint — stimulates the release of the body’s natural healing cells, which travel to the joint, triggering the growth of strong, fibrous tissue.

Over time, these cells grow into and around the porous material of the implant. Then, over the next three to six months, this fibrous tissue fills the space between the bones, while the spongy implant degrades. What remains is a soft tissue ‘pseudo’ joint — although not as hard as the cartilage it replaces, it still restores normal mobility. This new joint should last indefinitely, say the developers.

Trial results from 270 patients, published in the Journal of Hand Surgery and the journal Tissue Engineering, found that those who had the new treatment had significantly less pain than patients with conventional joint replacements. After 12 months, their score on a pain rating scale had dropped from 70 to 15; in the comparison group, the score dropped from 70 to 40.

Researchers say the device is suitable for patients who are suffering from rheumatoid or osteoarthritis in the small joints of the hands and feet, but do not envisage the device being used for hip or knee joints, as these structures are too complex.

Commenting on the device, Jane Tadman, of Arthritis Research UK, which funds research into joint replacement surgery, said: ‘The biodegradable joint implant is a novel treatment that may have potential clinical application.

‘Instead of chopping the ends off bones and putting in a joint replacement, this puts in a kind of “spacer” which will be re-absorbed into the fibrous tissue around the joint — so it’s a kind of flexible joint fusion. But whether it’s better than a joint replacement remains to be seen. We need more studies comparing it against conventional treatments. It has to be shown that it offers therapeutic benefit.’

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