Clinical Orthopaedics and Related Research®

, Volume 469, Issue 8, pp 2278–2285

Do First-generation Highly Crosslinked Polyethylenes Oxidize In Vivo?

  • Daniel MacDonald
  • Ashlyn Sakona
  • Allyson Ianuzzi
  • Clare M. Rimnac
  • Steven M. Kurtz
Symposium: UHMWPE for Arthroplasty: From Powder to Debris

DOI: 10.1007/s11999-010-1728-3

Cite this article as:
MacDonald, D., Sakona, A., Ianuzzi, A. et al. Clin Orthop Relat Res (2011) 469: 2278. doi:10.1007/s11999-010-1728-3

Abstract

Background

Highly crosslinked and thermally treated polyethylenes were clinically introduced to reduce wear and osteolysis. Although the crosslinking process improves the wear performance, it also introduces free radicals into the polymer that can subsequently oxidize. Thermal treatments have been implemented to reduce oxidation; however, the efficacy of these methods with regard to reducing in vivo oxidative degradation remains to be seen. Polyethylene oxidation is a concern because it can compromise the ultimate strength and ductility of the material.

Questions/purposes

We analyzed the oxidation, oxidation potential, and mechanical behavior of thermally treated highly crosslinked polyethylene retrieved acetabular liners.

Methods

Three hundred seven acetabular liners were collected from consecutive revision surgeries at six institutions over a 10-year period. Twenty-four were sterilized using nonionizing methods, 43 were sterilized in an inert environment, 80 were highly crosslinked and annealed, and 160 were highly crosslinked and remelted. Oxidation and oxidation potential were assessed by Fourier transmission infrared spectroscopy. Mechanical behavior was assessed by the small punch test.

Results

Oxidation and hydroperoxide (oxidation potential) indices were elevated in the annealed and gamma inert sterilized groups compared with those of the remelted liners and uncrosslinked gas sterilized controls, particularly at the rim. We also detected an increase in oxidation over time at the bearing surface of the remelted group. Ultimate strength of the polyethylene at the bearing surface was negatively correlated with implantation time for the annealed liners.

Conclusions

Within the first decade of implantation, the clinical outlook for first-generation highly crosslinked polyethylene remains promising. However, ongoing research continues to be warranted for first-generation highly crosslinked polyethylene bearings to monitor the implications of elevated oxidation at the rim of annealed liners as well as to better understand the subtle changes in oxidation at the bearing surface of remelted liners that occur in vivo.

Copyright information

© The Association of Bone and Joint Surgeons® 2010

Authors and Affiliations

  • Daniel MacDonald
    • 1
  • Ashlyn Sakona
    • 1
  • Allyson Ianuzzi
    • 1
  • Clare M. Rimnac
    • 2
  • Steven M. Kurtz
    • 1
  1. 1.Implant Research Center, School of Biomedical Engineering, Science, and Health SystemsDrexel University, and Exponent, IncPhiladelphiaUSA
  2. 2.Mechanical and Aerospace EngineeringCase Western Reserve UniversityClevelandUSA

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