A comparative microstructural study of vitamin-E blended and infused highly crosslinked UHMWPE for total knee arthroplasty

Abstract The impact of adding antioxidant vitamin-E (α-tocopherol) to the microstructure of ultrahigh molecular weight polyethylene (UHMWPE) for total knee arthroplasty has been studied in detail by means of Raman microprobe spectroscopy. Three tibial insert samples prepared by different manufacturing methods were investigated, as follows: (A) a sample manufactured without blending with vitamin E which did not receive any irradiation dose after consolidation but underwent final sterilization in ethylene oxide (EtO); (B) a sample blended with 0.3 wt% of α-tocopherol, an isomer of vitamin E, and manufactured as sample (A); and, (C) a sample in which vitamin E was diffused after being irradiated with 100 kGy dose of γ-ray. Clear microstructural differences were observed in terms of phase contents (i.e., amorphous, crystalline, and intermediate phase fraction), molecular orientation, and the degree of anisotropy between the investigated tibial plates. Vitamin E in the starting resin promoted chain mobility leading to reorganization of the molecular chains. The spectroscopic characterizations helps to rationalize the complex effect of vitamin-E on the UHMWPE microstructure and gives useful information on how significantly any single step of the manufacturing procedures might affect the mechanical properties of the final orthopedic component.