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Vitamin E-enhanced polyethylene liners show low wear in THA performed for OA
The amount of head penetration and cup migration was low in patients with osteoarthritis who underwent total hip arthroplasty with vitamin E-enhanced highly crosslinked polyethylene liners regardless of the femoral head material used in the implant or the size of the femoral head.
“We have demonstrated less wear compared to any other study of polyethylene,” Henrik Malchau, MD, PhD, of Massachusetts General Hospital (MGH), in Boston, one of the investigators, told Orthopaedics Today Europe. “We have not demonstrated any side effects in implant stability.”
Nanna Sillesen, MD, PhD, a research fellow at Harris Orthopaedic Laboratory at MGH is scheduled to present the findings at the EFORT Congress on June 6 in the Paris Auditorium from 17:15 to 18:15.
Multicenter THA study
Malchau and colleagues prospectively studied 144 patients (150 hips) who underwent total hip arthroplasty (THA) at two of three centers involved in the study. The average follow-up was 5 years.
Image: Sillesen N
The 61 patients operated on at center 1 received a Regenerex Porous Titanium Construct acetabular cup (Biomet; Warsaw, Ind., USA) with a vitamin E-enhanced highly crosslinked polyethylene liner (E1 Antioxidant Infused Technology; Biomet) and a 32-mm or 36-mm diameter cobalt chrome femoral head.
Forty-five patients treated at center 2 received the same cup with a highly crosslinked polyethylene liner that was doped with vitamin E and 44 patients treated at center 2 received Arcom XL liners not doped with vitamin E (Biomet; Warsaw, Ind., USA). All the patients treated at center 2 received either 32-mm or 36-mm diameter ceramic femoral heads.
The surgeons at center 1 under-reamed the acetabular bone bed by 1 mm and surgeons at center 2 reamed the bone bed line-to-line, according to Malchau.
To measure femoral head displacement into the polyethylene and acetabular component stability, investigators performed radiostereometric analyses (RSA) in all patients immediately postoperatively and at 6 weeks, 6 months, and 1 year, 2 years, 3 years and 5 years after THA surgery.
Low wear, no increase in migration
The median femoral head penetration for THAs performed at center 1 with the vitamin E-doped liners and 32 mm metal heads was –0.02 mm ± 0.02 mm.
Malchau and colleagues found this penetration was about the same as that for THAs performed at center 2 with ceramic heads with the vitamin E liners at 0.02 mm ± 0.05 mm and for ceramic heads used at center 2 with non-vitamin E liners, where head penetration was 0.02 mm ± 0.04 mm.
At 3 years of follow-up, these differences were not significant.
At 1 postoperative year, investigators found proximal cup migration of 0.14 mm ± 0.04 mm for cases at center 1, a distance that was significantly lower than at center 2 where the cup migration was 0.38 mm ± 0.05 mm (P<0.001). However, they noted cup migration at both centers did not increase at 3 years.
“We have the lowest wear percentage so far with any highly crosslinked polyethylene and we have no side effects with increased migration of the implants,” Malchau said, noting the main outstanding question about vitamin E-doped highly crosslinked polyethelene is how it will withstand wear in the second decade.
One patient in the study who developed an infection underwent surgical debridement and irrigation, but did not require a revision or a liner exchange. Study limitations included a lack of randomization and controls and the low numbers of patients enrolled in the study at both centers, Malchau said.
“We are running a much larger cohort study where we include 500 patients with vitamin E-stabilized polyethylene and 500 patients with a more conventional type of polyethylene, but it needs a much longer follow-up before we can make any clinical conclusions.” – by Renee Blisard Buddle
- Reference:
- Sillesen N. Paper #13-2743. Scheduled to be presented June 6 at the EFORT Congress; June 5-8, 2013. Istanbul.
- Fore more information:
- Henrik Malchau, MD, can be reached at Orthopedic Department, Massachusetts General Hospital, 55 Fruit St., GRJ 1126, Boston, MA 02114, USA; email: hmalchau@partners.org.
Disclosure: Malchau is a shareholder in RSA Biomedical and is a consultant to Biomet. Malchau and Sillesen receive grant/research support from Biomet.