Introduction. Cobalt chrome on polyethylene remains a widely used bearing combination in total joint replacement. However wear induced osteolysis, bulk material property degradation of highly cross-linked polyethylene (HXLPE) [1], and oxidation after implantation (thought to be as a result of lipid absorption or cyclic loading [2]) remains a concern. ECIMA is a cold-irradiated, mechanically annealed, vitamin E blended next generation HXLPE developed to maintain mechanical properties, minimise wear and to improve the oxidation resistance in the long-term. The aim of this study was to compare the in-vitro wear rate and mechanical properties of three different acetabular liners; conventional UHMWPE, HXLPE and ECIMA. Methods. Twelve liners (Corin, UK) underwent a 3 million cycle (mc) hip simulation. Three conventional UHMWPE liners (GUR1050, Ø32 mm, 30 kGy sterilised in Nitrogen), three HXLPE liners (GUR1020, Ø40 mm, 75 kGy cross-linking and EtO sterilised) and six ECIMA liners (0.1 wt% vitamin E GUR1020, Ø40 mm, 120 kGy cross-linking, mechanically deformed and annealed, and EtO sterilised) articulated against CoCrMo alloy femoral heads to ASTM F75 (Corin, UK). Wear testing was performed in accordance with ISO 14242 parts 1 and 2, with a maximum force of 3.0 kN and at a frequency of 1 Hz. The test lubricant used was calf serum with a protein content of 30 g/l and 1% (v/v) patricin added as an antibacterial agent. Volumetric wear rate was determined gravimetrically after the first 0.5 mc and every 1 mc thereafter. ASTM D638 type V specimens (3.2 mm thick) were machined from ECIMA material for uniaxial tension testing to ASTM D638. Ultimate tensile
Recent findings about UHMWPE oxidation from in vivo stresses lead to the need of a better understanding of which anti-oxidant additivation method is the best option for the use in orthopaedic field. A GUR 1050 crosslinked Vitamin E - blended UHMWPE has been investigated, to provide an accurate outline of its properties. DSC and FTIR measurements, together with ageing and tensile tests were performed on compression moulded blocks, as well as biocompatibility tests, including implantation on rabbits. Moreover, wear simulations on finished components (Delta acetabular liners) have been completed. All the test procedures have been repeated for a reference material, a GUR 1050 crosslinked and remelted standard UHMWPE (commercial name UHMWPE X-Lima), and the outcomes have been compared to the crosslinked Vitamin E - blended UHMWPE ones. On the additivated UHMWPE, we found a ultimate tensile strength of 43 MPa, a
INTRODUCTION. The lifetime of UHMWPE implants may be limited by wear and oxidative degeneration. Wear produced particles are in general biologically active, and may induce osteolysis. As threshold of PE wear rate below which osteolysis is rarely observed is postulated to be less tahn 0.1 mm per year. Moreover, PE delamination and breakage are consequences of the embrittlement of the PE due to oxidation. Both demonstrate, that improving the clinical behaviour of UHMWPE means reduction of wear particles. The first can be achieved by cross-linking the second by the anti-oxidative stabiliser vitamin E. The highly cross-linked PE vitamys ® used for the isoelastic monobloc cup RM Pressfit (Mathys AG Bettlach, Bettlach, Switzerland) is mixed with 0.1% of synthetic vitamin E and is the first and only highly cross-linked PE used in total hip replacement that meets all requirements for the best grade UHMWPE in
The objective of this study was to determine if a synthetic bone
substitute would provide results similar to bone from osteoporotic
femoral heads during Pushout studies were performed with the dynamic hip screw (DHS)
and the DHS Blade in both cadaveric femoral heads and artificial
bone substitutes in the form of polyurethane foam blocks of different
density. The pushout studies were performed as a means of comparing
the force displacement curves produced by each implant within each
material.Introduction
Methods