Metal-on-Metal Implant (IMAGE) Northwestern University Caption This is an X-ray of the hip region with a metal-on-metal implant superimposed and a schematic illustrating graphitic material on the surface of the implant. The red spheres represent the positions of the carbon atoms in a single layer of graphite. Credit Northwestern University Usage Restrictions None License Licensed content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.