Knee Solutions – Alternative Bearing Surfaces

Traditional total knee replacements utilize cobalt chrome or titanium alloy components to cap the bony surfaces of the knee, and ultra high molecular weight polyethylene (UHMWP) to replace the cartilage. Although these materials worked quite well from the outset, many total knees still wear out after 15-20 years.

Newer materials are now available. One company has developed a method of converting a thin portion of the surface of the femoral component to a hard, smooth zirconia ceramic—which causes less wear against the plastic. We expect these components to wear roughly twice as well against the polyethylene insert as standard cobalt chrome components.

Polyethylene is also changing. UHMWP now can undergo a process called “crosslinking,” which converts the parallel strands of polyethylene molecules into a crosslinked “weave,” adding durability to the polyethylene. Although the crosslinking process causes the polyethylene to become more brittle, other methods for treating the polyethylene to reduce this affect, such as adding vitamin E to the polyethylene, are being evaulated.

With these and other new developments in materials, we should expect total knee replacements to last much longer than 20 years now and in the future.

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