Vitamin E-Diffused Highly Cross-Linked Polyethylene Liner
Condition: Osteoarthritis
MeSH terms: Osteoarthritis
Study type: Interventional

Summary: 
      Vitamin E incorporated highly cross linked polyethylene (E-XLPE) was developed to increase
      oxidative resistance of highly cross-linked polyethylene (XLPE) without affecting mechanical
      properties. The investigators evaluated this type of polyethylene in a randomized clinical
      study, using Radiostereometric Analysis (RSA). The objective of this study was to compare the
      early-term wear of E-XLPE to a compression annealed polyethylene liner (C-XLPE, ArComXL®).
      The clinical outcome at two years was not expected to be affected by the choice of
      polyethylene.
    

Detailed description: 
      First generation of modern highly cross-linked polyethylene (XLPE) was clinically introduced
      in 1998 and has in most countries become standard as bearing surface in total hip
      arthroplasty. Studies of these materials have shown significantly reduced femoral head
      penetration when compared to gamma sterilized conventional polyethylene.

      Thermaly treating (melting or annealing) is often a part of the manufacturing process of
      highly cross-linked polyethylenes. The polyethylene is exposed to irradiation to achieve
      cross-linking and improve wear resistance. Cross-linking by irradiation increases the amount
      of free radicals in the material.These radicals must be eliminated or stabilized to avoid
      oxidative degradation over time.Thermal treatment improves oxidation resistance but
      potentially changes the mechanical properties of the polyethylene.

      By annealing i.e. heat treatment under the melt temperature the material maintains better
      mechanical properties, but elimination of free radicals is suboptimal, which can lead to
      oxidation in vivo.Heat treatment of the polyethylene above the melt temperature will more
      effectively reduce or eliminate the amount of residual free radicals. This will increase
      oxidation resistance, but will negatively influence the mechanical properties of the
      material.

      Due to these limitations new generations of cross-linked polyethylene materials have been
      developed. Introducing Vitamin E (α-tocopherol), a natural antioxidant into the material
      prevents oxidative degradation and stabilizes the free radicals found in irradiated
      polyethylene plastic. In laboratory tests, polyethylene liners with incorporated vitamin-E
      have demonstrated similar wear, greater strength and better resistance to oxidation compared
      with the first generation cross-linked polyethylene. Currently, there are only laboratory
      studies on vitamin E diffused polyethylene available.

      The hypothesis in this study is that the early-term E-XLPE wear is low and comparable to a
      heat-treated XLPE. The investigators also hypothesize that implant fixation and clinical
      outcome at two years will be unaffected by the choice of polyethylene.

      The investigators therefore evaluated the early bedding in and wear in an uncemented
      arthroplasty supplied with liners made of vitamin E diffusion doped XLPE (E1®, Biomet,
      Warsaw, IN, USA). In the control group the investigators used the same uncemented hip
      prosthesis with polyethylene liners manufactured to achieve high levels of crosslinking
      without sacrificing the mechanical strength and extinguish residual free radicals (ArComXL® ,
      Biomet, Warzaw, IN, USA).
    

Intervention name(s): E-poly; ArComXL
Intervention type(s): Other; Other
Intervention description(s): comparison of two different polyethylene plastic 0,04 mm at 3 months 0,06 at 2 years; comparison of two different polyethylene plastic 0,03 mm at 3 months 0,10 mm at 2 years
Allocation: Randomized
Intervention model: Parallel Assignment
Masking: Double (Participant, Investigator)
Primary purpose: Supportive Care