Highly cross-linked polyethylene implants have demonstrated
excellent radiographic results, minimal penetration and low linear wear, even
against large femoral heads, according to a recent presentation that reviewed
four critical polyethylene studies in the
“Our conclusions with these four studies — and numerous
studies throughout the literature — suggest that first generation highly
cross-linked polyethylene (HXLPE) has excellent clinical results at 7 to 10
years,” Harry E. Rubash, MD, orthopedic department chief at Massachusetts
General Hospital (MGH), said during his presentation at the
SICOT XXV Triennial World Congress 2011 in Prague.
Rubash’s co-authors on these studies were Charles Bragdon, PhD; Brian
Jarrett, BS; Michael Dornier, MS; Andrew Freiberg, MD; Young-Min Kwon, MD, PhD;
Henrik Malchau, MD, PhD; and William H. Harris MD, DSc.
Penetration rate unchanged
Rubash discussed four key polyethylene implant wear studies: a 7-year to
10-year single-center follow-up of penetration rates for HXLPE vs. conventional
polyethylene; a 5-year to 10-year follow-up multicenter study of Longevity
(Zimmer; Warsaw, Ind.) polyethylene components; a multicenter, radio
stereometric analysis (RSA) study of large diameter femoral head
total hip arthroplasty and preliminary vitamin E highly
cross-linked polyethylene data.
The first investigation revealed no revisions for wear or liner fracture
among implants studied, as well as any
osteolysis or component loosening, Rubash noted. He and
colleagues examined 184 patients postoperatively at the 7-year follow-up and 44
patients at the 10-year follow-up. Analyses done at both time points showed low
linear penetration rates using the Martell method for edge detection and wear.
However, concerns from a Swedish group examining RSA findings led the
MGH team to conduct a subsequent study examining radiographs of penetration
rates of 278 HXLPE implants used in patients treated at seven centers who were
followed up for 5 years to 10 years. The primary implants involved Longevity
liners and 26-mm, 28-mm and 32-mm diameter chromium cobalt femoral heads.
Rubash and colleagues found no change in the penetration rate.
Linear wear studied
“Our conclusions of these two studies showed that the MGH [study],
at least at mid-term follow-up, showed low femoral head penetration rates at 7
to 10 years with no signs of osteolysis by plain films and our multicenter
study showed the same,” Rubash said. “We were not able to demonstrate
an increase in femoral head penetration rate like they did in the Swedish study
with our U.S. multicenter study.”
The third study Rubash cited compared standard size femoral heads (26
mm, 28 mm and 32 mm) to larger femoral heads (36 mm, 28 mm and 40 mm) in 525
patients to determine corresponding linear wear rates. Researchers found no
signs of osteolysis and a low linear wear rate for all femoral head sizes,
“The wear of HXLPE is extremely low, even when articulating against
femoral head diameters greater than 32 mm,” Rubash said, noting that
although researchers observed increases in the wear rate with larger femoral
heads, the difference was not statistically significant.
A study of 51 hips in 47 patients examined at the effects of the E1
Antioxidant Infused Technology (Biomet; Warsaw, Ind.) polyethylene implants vs.
conventional polyethylene implants. The investigators found penetration with
“E1 polyethylene is very, very similar to the cross-linked polyethylene
both [with] the 28 mm heads, as well as the 36 mm heads,” Rubash said.
Although HXLPE implants may have a low wear rate, Rubash mentioned some
of the other benefits to using polyethylene compared to other hip articulation
materials: “With crosslinked polyethylene, you can avoid fractures,
squeaking, [aseptic lymphocytic vasculitis-associated lesions] ALVAL,
pseudotumors and a variety of other reasons for sleepless nights.”
– by Jeff Craven
- Bragdon C, Burke D, Ekeledo A, et al. Seven to ten year follow-up
of highly cross-linked polyethylene liners in total hip arthroplasty. J
Bone Joint Surg Br. 2010;92:511.
- Digas G, Kärrholm J, Thanner J, Herberts P. 5-year experience
of highly cross-linked polyethylene in cemented and uncemented sockets: two
randomized studies using radiostereometric analysis. Acta Orthop.
- Rubash HE. International Hip Society Symposium: Bearing couples.
Highly cross-linked polyethylene. Presented at the SICOT XXV Triennial World
Congress 2011. Sept 6-9. Prague.
- Harry E. Rubash, MD, can be reached at 55 Fruit St., Yawkey Center
for Outpatient Care, Suite 3700, Boston, MA 02114; 617-726-5231; email:
- Disclosure: Rubash receives research support from Biomet and