Radiation Modification of Synthetic Polymers in Orthopeadics
Following from extensive basic research carried out in South Africa in the mid-seventies involving senior local orthopaedic surgeons and radiation polymer experts, a unique crosslinking process, called the Gammalink process, was developed to enhance the wear characteristics of orthopaedic prostheses manufactured from UHMWPE. The Gammalink process results in a substantial improvement in the wear characteristics of the implant material and corresponding decrease in wear debris and the associated osteolysis.
As opposed to other radiation crosslinking processes introduced in the late nineties, the South African process entails the gamma crosslinking of the implant itself in such a way that the surface of the prosthesis has a much higher degree of crosslinking than the inner part thereof. The more recently developed crosslinked implants rely on the prior crosslinking of the polymeric base material, followed by the machining of the implant from the crosslinked polymer. The differences between the two processes result in different wear and clinical characteristics – the highly crosslinked surface with a lesser crosslinked inner body ensures that the desirable visco-elastic properties of the implants are retained, analogous to case hardening in metals.