Meanwhile, thanks to adaptations made by ORNL physicist Gerald Alton and collaborators, calutrons were showing promise as ion sources for the budding semiconductor industry. By the mid 1960s ORNL's calutrons had ion implanted thousands of semiconductor samples. In an unprecedented example of technology transfer, ion doping was swiftly transformed from an exotic laboratory phenomenon into a gargantuan global industry. For hip implants, ion treating the cobalt-chrome ball, or femoral head, offered longer life. The chief beneficiary is not the femoral head itself, but the softer polyethylene socket in which it nestles.
Most surgeons now consider polyethylene to be an implant's weakest link.
The body's immune system sees these particles as invaders and launches a counterattack. The real victim in this warfare though, is the surrounding bone tissue, which is broken down by enzymes released by the immune-system warriors. The ions, blasted into the metal by a particle accelerator, harden and smooth the ball's surface. More important, they also seem to attract and hold a thin film of joint fluid, which lubricates the moving parts. Several implant manufacturers agree.