High cycle in vitro hip wear of and in vivo biological response to vitamin E blended highly crosslinked polyethylene

Effect of serum dilution fluids on the wear of unirradiated and high dose gamma-irradiated, vitamin E stabilized UHMWPE

“…In general, multidirectional, serum lubricated wear tests have been shown to produce wear particles that fit well into this range [32]. VEXLPE wear particles have been shown to be similar to conventional UHMWPE particles [15].…”

“…With 1:1 PBS dilution, the difference was 20-fold (p < 0.001). In three hip simulator studies against CoCr heads, the following reductions in wear rate were obtained with vitamin E stabilized, highly crosslinked UHMWPE: (1) 10-fold, gamma-sterilized vs. 85 kGy gamma-irradiated [13], (2) 5-fold, unirradiated vs. 90 kGy electron beam irradiated [14], and (3) 20-fold, gamma-sterilized vs. 100 kGy electron beam irradiated [15]. The variation of reduction is wide but the observed wear resistance of the high dose irradiated, vitamin E stabilized material is always superior, as in the present study.…”

“…Another limitation was that wear particles were not analysed. Clinically, the majority of polyethylene particles are in the 0.1 µm to 1 µm size range [31], and therefore they are biologically active [15]. In general, multidirectional, serum lubricated wear tests have been shown to produce wear particles that fit well into this range [32].…”

“…It was considered interesting to find out (a) if a similar decrease occurs with unirradiated and with vitamin E stabilized, 100 kGy gamma-irradiated, highly crosslinked UHMWPE, 'VEXLPE', and (b) whether the phosphates or sodium chloride or their combined action is responsible for the decrease. Vitamin E stabilization has been introduced in the recent years to prevent the in vivo oxidation of highly crosslinked UHMWPE without compromising mechanical properties, which is typical of heat treatments used earlier to prevent oxidation [13][14][15].…”

“…Crosslinking has been shown to be beneficial for the wear resistance [13][14][15], but it has been suggested that the presence of vitamin E hampers crosslinking and therefore the wear resistance is inferior to that of heat-treated, crosslinked materials [16]. After a few preliminary circular translation pin-on-disk (CTPOD) trials, it was hypothesized that (1) the polyethylene wear is significantly reduced by the dilution of serum lubricant with PBS, phosphate buffer, saline, or their combined action, compared with DW dilution, and that (2) the VEXLPE wear rate is between those of unirradiated UHMWPE and of highly crosslinked, heat-treated UHMWPE.…”