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Lower wear rates seen with crosslinked vs. conventional polys for THA at 8 years
Crosslinked polyethylene showed 33% wear reduction at 5 years and 38% at 8 years.
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A new clinical trial shows that crosslinked polyethylene has a lower wear rate than conventional polyethylenes at longer follow-up and maintains that low wear rate over time.
In a prospective randomized trial, investigators studied 48 patients who underwent total hip arthroplasty using either Stryker’s Duration crosslinked polyethylene or conventional polyethylene material. An 8-year follow-up revealed a significantly lower wear rate in the crosslinked polyethylene group.
The investigators also found a 38% reduction in annual wear for the crosslinked polyethylenes, which was similar to the 45% reduction in wear predicted by simulator studies, according to the study abstract. Moreover, the wear rate reduction at 8 years was an even 5% (or percentage points) larger than an earlier measurement at 5 year.
“The Duration polyethylene is better than the standard polyethylene with regards to wear at 8 years,” Bernd P. Grimm, PhD, said during his presentation at the 8th European Federation of National Associations of Orthopaedics and Traumatology Congress. “The wear rate advantage is maintained at 8 years and that correlates very well with the simulator predictions and, so far, we have no signs of aging. The reduced wear is starting to show and [there is] less osteolysis and fewer revisions. Therefore, I think that we can confidently extrapolate these findings for the new generation of crosslinked polyethylene.”
Eight-year follow-up
For the hip stimulator data the investigators radiographically measured wear using computer software and also radiographically assessed for osteolysis.
They found no significant differences between the crosslinked and conventional polyethylene groups for clinical parameters such as cup diameter, inclination, liner thickness and ball diameter. They also saw no significant differences regarding patient demographics.
In the 8-year follow-up, five patients died and three were lost to follow-up.
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No aging effects
The investigators found a significantly lower wear rate for the crosslinked polyethylene group compared to the conventional poly cohort at 8 years follow-up. “When we did the 5-year measurement, the wear rate advantage of the crosslinked material was 33% and at 8 years it was 38%,” he said. “We can see that, so far, there are no aging effects.”
Due to the small sample size, the study was inadequately powered to detect statistically significant differences from the radiographic findings. However, Grimm said that only the conventional poly group showed acetabular radiolucencies. “Signs of femoral osteolysis were more frequent in the conventional group than in the Duration group,” he said. “We also had one revision already in this conventional group due to aseptic loosening. So, there also seems to be an improved survival showing up for the Duration group.”
For more information:Reference:
- Bernd P. Grimm, PhD, can be reached at the Atrium Medisch Centrum, Department of Orthopaedic Surgery, Heerlen, CX. The Netherlands. He has received research or institutional support from Stryker and Biomet.
- Grimm BR, Tonino AJ, Heyligers IC. Eight-year prospective, randomized comparison between cross-linked and conventional polyethylene in total hip arthroplasty. F327. Presented at the 8th European Federation of National Associations of Orthopaedics and Traumatology Congress. May 11-15, 2007. Florence.