How do scratching and friction affect a knee implant?
Traditionally, cobalt chrome has been the material of choice for knee implants because of its strength and relative hardness. However, studies have shown that cobalt chrome implants have a tendency to roughen over time when implanted in the body. Thus, when a roughened replacement joint rubs against a plastic bearing surface, the plastic wears out. In fact, laboratory tests show that even a single scratch on a cobalt chrome surface can increase the rate of plastic wear 10 times. Over time, the plastic surface simply wears out and additional surgery is then needed to replace the worn implants. Studies conducted recently have proven through controlled wear testing that a scratched or roughened cobalt chrome implant will dramatically increase production of plastic wear debris and reduce the life span of the knee implant substantially.
