Rim Damage in Retrieved 1st and 2nd Generation Annealed Highly Crosslinked Polyethylene Hip Liners.

BACKGROUND

Highly crosslinked polyethylene (HXLPE) was clinically introduced in total hip arthroplasty (THA) with the goal of reducing wear and wear debris-induced osteolysis. Studies have shown increased wear resistance of the HXLPE articulating surface as compared to controls. However, wear particles can also be produced via different mechanisms, particularly at the rim of the HXLPE liner. The purpose of this study was to compare the rim damage of 1st generation-annealed and 2nd generation sequentially annealed HXLPE THA acetabular liners.

METHODS

There were 89 annealed and sequentially annealed THA liners implanted for five or more years that were collected at routine revision THA surgery. The liners were revised predominantly for loosening, infection, and instability. The single-dose annealed liners were implanted for a longer duration than the sequentially annealed liners (mean difference of 2.5 years, P < 0.001). The liners were inspected for the seven damage modes. In addition, we noted instances of subsurface whitening. The extent of damage was described as the arc angle of the rim that exhibited each damage mode.

RESULTS

Rim damage was observed on 46% of annealed liners and 25% of sequentially annealed liners. Delamination, subsurface whitening, burnishing, and abrasion were the damage modes observed in both cohorts. The extent of delamination and subsurface whitening was greater in the annealed HXLPE liners than in the sequentially annealed HXLPE liners. We did not observe any correlation between the extent of any damage mode and implantation time, head size, rim oxidation, or implant design (P > 0.05).

CONCLUSIONS

We analyzed the rim damage modes of retrieved 1st and 2nd generation-annealed HXLPE THA liners. We observed that the sequentially annealed liners had lower levels of damage as compared to annealed HXLPE liners. The clinical relevance of these findings is unclear at this point, as the biological response to HXLPE particles is multifactorial.