Study: 95% less wear with crosslinked vs. traditional polyethylene

Highly crosslinked polyethylene bearings appear to reach a steady wear state at two years postop.

Hip prostheses that use highly crosslinked polyethylene bearings have significantly lower steady-state wear rates than implants with traditional polyethylene bearings, an in vivo study shows.

Lower rates of polyethylene wear may generate less polyethylene particle debris, which has been linked to periprosthetic bone loss, aseptic loosening and late THR failure. Thus decreasing wear may help limit osteolysis, according to the study, published in The Journal of Arthroplasty.

David W. Manning, MD, an orthopedic surgeon at the University of Chicago Medical Center, and colleagues at several U.S. centers conducted the study. The researchers used the Martell computerized edge-detection method to determine 2-D femoral head penetration and compare steady-state wear rates between two polyethylene bearing materials.

The control group involved patients implanted with a prosthesis featuring traditional ultra-high molecular weight polyethylene (UHMWPE) bearings. The researchers compared these patients to those implanted with either the Inter-Op or Trilogy (Zimmer Co.) prostheses, which feature electron beam-irradiated, postirradiation-melted, highly crosslinked polyethylene (HXLPE) bearings.

Both groups were matched for age, sex and body mass index. Additionally, surgeons used 28-mm cobalt chrome (CoCr) femoral heads and uncemented acetabular shells in all cases.

Using strict selection criteria, the researchers included 138 pairs of radiographs from the HXLPE group and 214 radiographs from the traditional polyethylene group for their analysis.

They found that HXLPE patients had an overall penetration rate of 0.012 ± 0.01 mm/year at 44 months follow-up, significantly lower than the 0.176 ± 0.054 mm/year penetration rate for traditional polyethylene patients at four years mean follow-up (P=.003).

“For the combined [HXLPE] group ... the steady-state wear rate with 28-mm CoCr femoral heads was 0.007 ± 0.022 mm/year and was 95% less than the traditional polyethylene steady-state wear,” the authors said in the study.

The traditional polyethylene group had a steady-state wear rate of 0.174 ± 0.114 mm/year (P=.003).

After 24 months, HXLPE femoral head penetration remained statistically unchanged at each six-month follow-up interval out to 44 months, which is consistent with steady-state wear, the authors noted.

No hips in either implant group required revision during the course of the study, they added.

For more information:
Manning DW, Chiang PP, Martell JM, et al. In vivo comparative wear study of traditional highly crosslinked polyethylene in total hip arthroplasty. J Arthroplasty. 2005;20:880-886.