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Investigator suggests use in young, active patients or
revision cases caused by high wear.
May 2008
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%,” said Georgios Digas, MD, “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.
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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Researchers used the Trilogy System with the Longevity liner
(Zimmer) in their study.
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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.
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