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More than 95% less wear with highly crosslinked PE vs. conventional PE
Investigator suggests use in young, active patients or revision cases caused by high wear.
Two randomized clinical studies investigating two types of highly crosslinked polyethylene sockets show significantly decreased wear rates with highly crosslinked polyethelene compared to conventional polyethylene at 5 years.
“Use of highly crosslinked instead of conventional polyethylene (PE) reduced wear by more than 95%,” Georgios Digas, MD, told Orthopaedics Today International. “Our findings support the continued use of the highly crosslinked PE.”
Digas and colleagues compared the wear rates of highly crosslinked polyethylene (HXLPE) and conventional PE in patients who underwent total hip arthroplasty (THA) with a minimum follow-up of 5 years. In the first study, the investigators examined 55 patients who received either HXLPE (Durasul, Zimmer) or cemented conventional PE sockets by the same manufacturer.
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Bilateral hybrid THA
The second study included 23 patients who underwent bilateral hybrid THA for bilateral primary or secondary hip osteoarthritis. Patients were randomized to receive either an HXLPE liner (Longevity, Zimmer) or the manufacturer’s conventional PE liner in the most painful side of the hip and had the other liner in the contralateral hip. The investigators used the same surgical approach and designer stem in both studies, and patients were mobilized at 1-day postop and performed weightbearing as tolerated.
Less head penetration wear
“Bedding in and creep for the Durasul all-PE was reached at 2 years [and] for the Longevity liners at 1 year, while the bedding-in for the conventional PE was reached at 6 months,” Digas said. “The steady-state wear rate was close to 0 in the two types of highly crossedlinked PE and 0.06 mm/year for the conventional PE in the two control groups.”
The investigators determined the wear rates using radiostereometry (RSA) examination in both studies and evaluated the patients in standing and supine positions at several time intervals.
In both studies, the investigators discovered less mean proximal and total head penetration wear rates for the HXLPE groups compared to the conventional PE groups for both the supine and standing examinations.
The first study revealed an overall proximal penetration rate of 0.03 mm/year for the HXLPE group and 0.072 mm/year in the conventional PE group. The second study showed 0.08 mm of bedding-in or creep for the HXLPE group and a 0.016 mm/year penetration rate. The conventional PE cohort had a penetration rate of 0.068 mm/year.
“Because of the excellent wear characteristics of the highly crosslinked PE, it can be used in patients with expected high wear rates as [in] young active patients or in cases of revision arthroplasty caused by high wear rate and osteolysis,” Digas said.
The investigators hope to follow patients in the two studies for at least 15 years and will note the incidence of osteolysis and adverse events. “There is some concern about altered mechanical properties and different biological effects of wear particles from highly cross-linked PE compared with conventional PE,” Digas said.
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Image: Digas G |
For more information:
- Georgios Digas, MD, can be reached at Sahlgrenska University Hospital, Göteborg University, S-41345, Göteborg, Sweden; e-mail: georgios.digas@vgregion.se. The authors’ institution received funding from Zimmer, the Swedish Research Council and the Göteborg Medical Society.
Reference:
- Digas G, Kärrholm J, Thanner J, et al. Five-year experience of highly cross-linked polyethylene in cemented and uncemented sockets. Acta Orthopaedica. 2007;78 (6):746-754.