Abstract
Background And Aims: Total knee replacements provide a cost effective treatment for painful joint conditions such as osteoarthritis. Their long term performance is governed by ultra-high molecular weight polyethylene (UHMWPE) wear which produces wear debris and leads to osteolysis and aseptic loosening of the implant. Using a new material which is more scratch resistant than cobalt chrome it is hoped to reduce wear of UHMWPE and its subsequent complications.
Methods: Two total knee replacements made from cobalt chrome and two of oxidised zirconium were wear tested in a knee simulator. Surface roughness data from the femoral components was collected. Gravimetric and volumetric wear of the polyethylene inserts was measured. SEM analysis of the surfaces was also performed.
Results: Oxidised zirconium is significantly more scratch resistant than CoCr; Ra (mean average roughness) of 0.7μm compared to 0.43μm (p< < 0.01) at end of test, and confirmed by SEM analysis. This was accompanied by a 4 fold reduction in wear of UHMWPE 49.60mg to 12.48mg (p=0.02). Barium sulphate particles were found to be embedded in the surface of the CoCr implants.
Summary And Conclusions: Oxidised zirconium leads to a reduction in wear of UHMWPE due to its increased resistance to third body wear. It has the potential to increase the longevity of total knee replacements by reducing UHMWPE related complications.
Honorary Secretary – Mr Roger Smith. Correspondence should be addressed to BASK at the Royal College of Surgeons, 35 - 43 Lincoln’s Inn Fields, London WC2A 3PN
