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  • Print publication year: 2011
  • Online publication date: June 2012

1 - Biocompatibility, sterilization, and materials selection for implant design

from Part I - Materials



All medical implants must be sterilized to ensure no bacterial contamination to the patient. How would you sterilize a total hip replacement comprising a titanium stem, a cobalt-chromium alloy head, and an ultra-high molecular weight polyethylene acetabular shell? Could the same method be employed for all three materials? How do you ensure that there is no degradation to the material or its structural properties? What factors would you need to consider in the optimization of this problem?

The inquiry posed above represents a realistic challenge that one might face in the field of orthopedic biomaterials. At a minimum, one would want to know the sterilization methods available for medical implants and which materials they best serve. For example, steam or autoclaving work well for sterilization of metals and ceramics but are generally unsuitable for polymers due to the lower melting and distortion temperatures of medical plastics. Also, one needs to consider whether there are any changes in the mechanical properties or if any time-dependent changes are expected owing to the sterilization method employed; for example, gamma radiation is known to leave behind free radicals (unpaired electrons) and these free radicals are highly reactive with elements such as oxygen that may be present or may diffuse into the implant material. In certain polymer materials such as ultra-high molecular weight polyethylene, gamma radiation can result in oxidation-induced embrittlement (shelf aging) that can severely degrade its wear and fracture properties. The case study presented at the end of this chapter addresses this issue.

Historical perspective and overview

Designing medical implants is a complex process, and this textbook aims to provide insight into the material, mechanical, and clinical factors that affect implant design and performance. The goal of this book is to integrate all aspects of implant design including clinical issues, structural requirements, materials selection, and processing treatments.

American Academy of Orthopaedic Surgeons 2007 Osteolysis and implant wear: biological, biomedical engineering and surgical principlesJournal of the AAOS 16 S1
Baker, D.Hastings, R.Pruitt, L. 2000 Compression and tension fatigue resistance of medical grade UHMWPE: the effect morphology, sterilization, aging and temperaturePolymer 41 795
Birkinshaw, C.Buggy, M.Dally, S. 1988 Mechanism of aging in irradiated polymersPolymer Degradation and Stability 22 285
Birkinshaw, C.Buggy, M.Dally, S.O’Neill, M. 1989 The effect of gamma radiation in the physical structure and mechanical properties of ultrahigh molecular weight polyethyleneJournal of Applied Polymer Science 38 1967
Black, J. 1999 Biological Performance of Materials: Fundamentals of BiocompatibilityNew YorkMarcel Dekker
Bronzino, J.D.Yong, J.Y. 2003 BiomaterialsBoca Raton, FLCRC Press
Bruck, S.D.Mueller, E.P. 1988 Radiation sterilization of polymeric implant materialsJournal of Biomedical Materials Research 22 133
Dole, M.Milner, D.C.Williams, T.F. 1958 Irradiation of polyethylene. II. Kinetics of unsaturation effectsJournal of the American Chemical Society 80 1580
Goldman, M.Pruitt, L. 1998 A comparison of the effects of gamma radiation and plasma sterilization on the molecular structure, fatigue resistance, and wear behavior of UHMWPEJournal of Biomedical Materials Research 40 378
Goldman, M.Ranganathan, R.Gronsky, R.Pruitt, L. 1996 The effects of gamma radiation sterilization and aging on the structure and morphology of medical grade ultra high molecular weight polyethylenePolymer 37 2909
Howie, D.W.Haynes, D.R.Rogers, S.D.McGee, M.A.Pearcy, M.J. 1993 The response to particulate debrisClinical Orthopedics: North America 24 571
Jasty, M. 1993 Clinical reviews: particulate debris and failure of total hip replacementsJournal of Applied Biomaterials 4 273
Kurtz, S.M. 2009 Packaging and sterilization of UHMWPEIn UHMWPE Biomaterials HandbookKurtz, S.MLondonElsevier21
Kurtz, S.M.Muratoglu, O.K.Evans, M.Edidin, A.A. 1999 Advances in the processing, sterilization, and crosslinking of ultra-high molecular weight polyethylene for total joint arthroplastyBiomaterials 20 1659
Park, J.B.Bronzino, J.D. 2003 Biomaterials: Principles and ApplicationsBoca RatonCRC Press
Park, J.B.Lakes, R.S. 1992 Biomaterials: An IntroductionNew YorkPlenum Press
Premnath, V.Harris, W.H.Jasty, M.Merrill, E.W. 1996 Gamma sterilization of UHMWPE articular implants: an analysis of the oxidation problemBiomaterials 17 1741
Pruitt, L. 2003 Radiation effects on medical polymers and on their mechanical propertiesAdvances in Polymer Science: Radiation EffectsKausch, H.H.Heidelberg:Springer-Verlag63
Pruitt, L.Ranganathan, R. 1995 Effect of sterilization on the structure and fatigue resistance of medical grade UHMWPEMaterials Science and Engineering91
Ratner, B.D.Hoffman, A.S.Schoen, F.J.Lemons, J.E. 1996 Biomaterials Science: An Introduction to Materials in MedicineNew YorkAcademic Press
Ries, M.D.Weaver, K.Beals, N. 1996 Safety and efficacy of ethylene oxide sterilized polyethylene in total knee arthroplastyClinical Orthopedics 331 159
Sutula, L.C.Collier, J.P.Saum, K.A.Currier, B.H.Currier, J.H.Sanford, W.M.Mayor, M.B.Wooding, R.E.Sperling, D.K.Williams, I.R.Karprazak, D.J.Surprenant, V.A. 1995 Impact of gamma sterilization on clinical performance of polyethylene in the hipClinical Orthopaedics and Related Research 319 28
Williams, D.F. 2008 On the mechanisms of biocompatibilityBiomaterials 29 2941