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The UHMWPE Lexicon is the online reference for ultra-high molecular weight polyethylene used in total joint replacements. The additional goals for this website are to provide an overview of state-of-the-art research in several key polyethylene related problems of clinical significance and to encourage hypothesis driven polyethylene research.
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Effects of High Dose Irradiation on Cross-Linking of Vitamin E-Blended UHMWPE
Vitamin E-stabilized, highly cross-linked ultrahigh molecular weight polyethylene (UHMWPE) is a promising oxidation and wear resistant UHMWPE with improved mechanical strength in comparison with the first generation, irradiated and melted UHMWPE. However, radiation cross-linking efficiency of UHMWPE decreases in the presence of vitamin E. Therefore an optimum vitamin E concentration and radiation dose level need to be determined to achieve a cross-link density comparable to 100-kGy irradiated and melted UHMWPE, which has shown excellent wear properties in vivo. Vitamin E concentrations equal to or above 0.3wt% (3000 ppm) in blended materials are not recommended for subsequent irradiation to achieve a wear resistant cross-linked UHMWPE.
Trace Concentrations of Vitamin E Protect Radiation Crosslinked UHMWPE from Oxidative Degradation
This research tested the hypothesis that the oxidation resistance of Vitamin E-blended UHMWPE would be influenced by trace doses of antioxidant, resin, and radiation treatment. Trace concentrations (<=500 ppm w/w%) of alpha-tocopherol (Vitamin E) were blended separately with GUR 1020 and 1050 resins, molded into disks, and irradiated according to different protocols. The results of this experiment supported the hypotheses that trace concentrations of Vitamin E, coupled with radiation treatment-but not resin grade-influence the mechanical and oxidative degradation behavior of UHMWPE.
Effects of Packaging on Free Radicals in Vitamin E Blended UHMWPE
Ultra-high molecular weight polyethylene (UHMWPE) powder (GUR 1020) was blended with high concentration (20%) of vitamin E (alpha-Tocopherol (alpha-T)) for direct detection of alpha-T radicals in presence of PE radicals. When irradiated in air, alpha-T-resin produced ESR signals characteristics of tochopheroxyl radicals (alpha-T-O(*)), suggesting that PE radicals are quenched by alpha-T. When alpha-T-resin was irradiated in N(2), presence of both PE and alpha-T radicals were evident in the ESR spectra.
Assessment of Oxidative Changes after In Vivo Degradation of UHMWPE Knee Components
This study reports on the suitability of different experimental techniques to evaluate chemical, microstructural, and mechanical changes associated with in vivo oxidation encountered in historical polyethylene components. The chemical, physical, and mechanical properties data confirmed the occurrence of in vivo degradation in the long-term implanted knee components following gamma irradiation in air. Furthermore, infrared spectroscopy alone appeared to provide excellent insight into the oxidation and crystallization state of the in vivo oxidized polyethylene.
2008 AAOS Scientific Exhibit: Gamma Inert Sterilization: A Solution to Polyethylene Oxidation?
This study explores the hypothesis that implants sterilized in a low oxygen environment undergo similar in vivo oxidative mechanisms as implants sterilized in air. Over the past seven years, an multi-institutional retrieval program has traced and analyzed 264 conventional polyethylene hip and knee components. Measurable oxidation was observed in all cohorts. The oxidation was regional. Surfaces with access to bodily fluids were more heavily oxidized than protected, bearing surfaces. This variation appeared to be greater in gamma-air sterilized implants. The research therefore demonstrates that gamma inert sterilization may have improved, but not completely solved, the problem of polyethylene oxidation for hip and knee arthroplasty.
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The UHMWPE Biomaterials Handbook: 2nd Edition
 The 2nd Edition of the UHMWPE Biomaterials Handbook, edited by Steven M. Kurtz, Ph.D., is currently under development for release in early 2009. The expanded Handbook will include over 30 chapters and 15 contributors, expanding upon the history, properties, and clinical performance of biomaterials used for joint replacement. The new edition will contain dedicated chapters to remelted and annealed highly crosslinked UHMWPE, Vitamin E stabilization, composite biomaterials, high pressure crystallization, as well as chapters covering advances in characterization, such as hip and knee simulator testing, radiographic wear measurement, biological response of wear debris, and fatigue and fracture behavior. Although the first edition of the Handbook is currently out of print, copies of the book may still be available through Amazon.
Spine Technology Handbook
 A new frontier for surgical grade UHMWPE is in the field of spine implants. The Spine Technology Handbook, edited by Steven M. Kurtz, Ph.D., and Avram A. Edidin, Ph.D., is published by Elsevier Academic Press. The 16 chapters of the Spine Technology Handbook (560 pp.) describe the bioengineering principles, biomaterials, and designs of implants used in the treatment of spine disorders. Major technologies reviewed include devices used for fusion (screws, plates, rods, and cages), disc repair and augmentation, total disc replacement, and vertebral body repair and augmentation. An excerpt from Chapter 11, which discusses the use of UHMWPE in disc replacement, can be found here. Copies of the book can now be ordered through Amazon and Academic Press.
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4th UHMWPE International Meeting in Torino, Italy
We are pleased to announce that the 4th UHMWPE International Meeting Update will be convened by the University of Torino, Italy, for September 17 & 18, 2009. As in previous years, the meeting will include two main parts: one basic research module, open for papers and oriented to gather cutting-edge research on UHMWPE; and a second part oriented to clinical aspects and discussion. Please stay tuned for additional details about the conference, which will be posted soon. For preliminary queries, please contact the conference chairman, Prof. Luigi Costa (luigi.costa@unito.it).
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Development of a Standard Guide for UHMWPE Implant Components at ASTM
At the May 2008 ASTM meeting for F04, a new task force convened to develop an "umbrella" type document listing all of the recommended preclinical testing that should be performed for UHMWPE implants components by manufacturers. The scope includes conventional and highly crosslinked UHMWPE, with and without Vitamin E. This standard is expected to provide guidance for UHMWPE testing to manufacturers of hip, knee, upper extremity, and spinal implants. The intent of this proposed standard is to provide the basis for a future FDA guidance document for UHMWPE. Participation in this task force continues to be open to all. To join the task force and participate in the standard development process, please contact the Task Force Chair, Prof. Warren Haggard, U. of Memphis (whaggrd1@memphis.edu) or the Vice Chair, David Schroeder, from Biomet (Dave.Schroeder@biomet.com). The next face-to-face meeting of the task force, to discuss the initial ballot results, is expected to take place at next ASTM meeting in November 2008.
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