HOW do you add ten years to the life of an artificial knee joint? Ask an astronomer. A robotic polisher designed to make the mirrors in space telescopes super smooth could extend the lifetime of fake knees.
Many people worldwide are fitted with artificial knee joints to relieve the agony of arthritis or injury. In most cases, an intricately shaped metal socket is attached to the femur, cupping a plastic head fixed to the tibia. However, as the knee flexes, rolls and rotates the parts grind together and particles of plastic are shed. This loosens the joint, and the patient鈥檚 gait remains wobbly until the prosthesis is replaced.
But if the joint鈥檚 surfaces could be made super smooth by precision polishing, fewer particles would be rubbed off and the knee would last far longer than the 15 years typical today.
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Currently, replacement knee joints are polished laboriously by hand, says Gordon Blunn of the centre for Biomedical Engineering at University College London. So he collaborated with Zeeko, a UCL spin-off that makes a robot for polishing telescope mirrors, to develop a new technique.
Zeeko鈥檚 robot polisher scans the surface of the mirror or knee joint to reveal any microscopic imperfections. The tool head comprises a rotatable and inflatable rubber ball wrapped in a fine polishing cloth, attached to the end of a robot arm. Using feedback from the scans, a computer works out which combinations of rotations, ball inflations and sweeping motions will leave the surface perfectly smooth.
Zeeko founder David Walker says the robot cuts the time taken to polish a mirror from months to days, because it eliminates the need for hand-finishing. Trials on artificial knees are set to begin in April.