No abstract

A novel, sensitive method for quantifying an equivalent antioxidant concentration, specifically vitamin E (VE), in postprocessed ultra-high molecular weight polyethylene (UHMWPE) for orthopedic implants is presented. This method correlates oxidative-induction time (OIT) determined from differential scanning calorimetry with starting VE weight percent in solvent blended samples using a nonlinear power law fit. The generated calibration curve reliably determined the equivalent VE concentration down to blended concentrations lower than 0.007 wt %, with a measurement uncertainty of 0.0009 wt %. This measurement uncertainty implies a detection limit that is significantly lower than currently achievable with the established method using Fourier transform infrared spectroscopy to calculate a VE index. However, exact processes that are influencing the OIT in irradiated materials are unclear at this time. UHMWPE blended with VE in powder, consolidated and irradiated form were investigated. In addition, intralaboratory results give support that this technique may lend itself to standardization in quality control and verification.

The suitability of grafted vitamin-E highly crosslinked polyethylene (VE-HXPE) for use in posterior stabilized (PS) and constrained condylar knee (CCK) applications has not been explored. We hypothesized that VE-HXPE performs better than conventional and crosslinked polyethylene under clinically relevant conditions. PS tibial post fracture resistance under adverse shear loading conditions, CCK tibial post resistance to torsional fatigue, delamination resistance under high stress, and wear resistance were evaluated. Grafted VE-HXPE exhibits (1) 10% and 57% improved PS post fatigue strength compared to conventional PE (CPE) and remelted HXPE; (2) 45% improved CCK post fatigue strength compared to CPE; (3) Greater than 36× the delamination resistance of CPE; and (4) 96% and 73% wear reduction compared to CPE and HXPE. VE-HXPE performed well under clinically relevant in vitro conditions. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 105B: 1789-1798, 2017.