Highly cross-linked, electron-beam-irradiated, melted polyethylene: some pros.
Extensive new evidence generated within the past the year provides strong support for the use of electron-beam highly cross-linked, subsequently melted ultra-high molecular weight polyethylene in total hip replacement arthroplasty. In terms of wear reduction, three studies involving three different demographic groups and two different measurement techniques have found that the femoral head penetration with this type of polyethylene after bedding in has finished taking place is less than 10 micra per year. This wear rate is similar to the wear rate of metal-on-metal and ceramic-on-ceramic articulations. Retrieval specimens up to 3 years after insertion confirmed the minimal wear by exhibiting persisting machine marks throughout the inside diameter of the liner. Extensive studies show no evidence of oxidation, confirming the absence of residual free radicals. No evidence of fatigue failure exists except three known cases out of 150,000, in which malposition of the acetabular component produced abnormally high contact stresses on unsupported polyethylene. The in vivo wear, oxidation resistance, and mechanical properties of this alternative bearing material are excellent, with in vivo durations now exceeding five years. The other major advantages over hard-on-hard bearings including familiarity, adaptability, forgiveness, and cost seem to be compelling.
Harris
William H
WH
Department of Orthopaedic Surgery and the Orthopaedic Biomechanics and Biomaterials Laboratory, Massachusetts General Hospital, 55 Fruit Street, Boston, MA 02114, USA. wharris.obbl@partners.org
D000328:Adult; D000368:Aged; D019644:Arthroplasty, Replacement, Hip / Q000379:methods; D016022:Case-Control Studies; D019245:Compressive Strength; D019544:Equipment Failure Analysis; D005260:Female; D006622:Hip Prosthesis; D006801:Humans; D008297:Male; D008422:Materials Testing; D008875:Middle Aged; D011095:Polyethylenes / Q000528:radiation effects*; D011474:Prosthesis Design; D011475:Prosthesis Failure; D011840:Radiation, Nonionizing; D013314:Stress, Mechanical; D013499:Surface Properties
D011095:Polyethylenes; C111601:ultra-high molecular weight polyethylene