title: Quantification of structural changes of UHMWPE components in total joint replacements.
abstract: BACKGROUND
  At present time the number of implantations of joint replacements as well as their revisions increases. Higher demands are required on the quality and longevity of implants. The aim of this work was to determine the degree of oxidative degradation and the amount of free/residual radicals in selected ultra-high molecular weight polyethylene (UHMWPE) components of the joint replacements and demonstrate that the measured values are closely connected with quality and lifetime of the polymer components.
  
  
  METHODS
  We tested both new (4 samples) and explanted (4 samples) UHMWPE polymers for total joint replacements. The samples were characterized by infrared spectroscopy (IR), electron spin resonance (ESR) and microhardness (MH) test. The IR measurements yielded the values of oxidation index and trans-vinylene index. The ESR measurements gave the free radicals concentration.
  
  
  RESULTS
  In the group of new polyethylene components, we found oxidation index values ranging from 0.00-0.03 to 0.24. The trans-vinylene index values ranged from 0.044 to 0.080. The value of free radical concentration was zero in virgin and also in sample of Beznoska Company and non-zero in the other samples. In the group of explanted components, the measured values were associated with their history, micromechanical properties and performance in vivo.
  
  
  CONCLUSIONS
  We demonstrated that measuring of oxidative damage may help the orthopaedic surgeon in estimating the quality of UHMWPE replacement component and thus radically to avoid early joint replacement failure due to worse polyethylene quality.
authors.affiliation: Department of Orthopaedics, First Faculty of Medicine, Charles University in Prague, V Úvalu 84, Prague 5 15006, Czech Republic. petrfulin@gmail.com.
authors.forename: Petr
authors.initials: P
authors.lastname: Fulin
authors.forename: David
authors.initials: D
authors.lastname: Pokorny
authors.forename: Miroslav
authors.initials: M
authors.lastname: Slouf
authors.forename: Martina
authors.initials: M
authors.lastname: Nevoralova
authors.forename: Tatana
authors.initials: T
authors.lastname: Vackova
authors.forename: Jiri
authors.initials: J
authors.lastname: Dybal
authors.forename: Jan
authors.initials: J
authors.lastname: Pilar
mesh_terms: D001672:Biocompatible Materials / Q000737:chemistry*; D003460:Crystallization; D004578:Electron Spin Resonance Spectroscopy; D005609:Free Radicals / Q000032:analysis; D006244:Hardness; D006622:Hip Prosthesis; D006801:Humans; D007720:Knee Prosthesis; D008422:Materials Testing; D010084:Oxidation-Reduction; D011095:Polyethylenes / Q000737:chemistry*; D011475:Prosthesis Failure; D012086:Reoperation; D013055:Spectrophotometry, Infrared
chemical_list: D001672:Biocompatible Materials; D005609:Free Radicals; D011095:Polyethylenes; C111601:ultra-high molecular weight polyethylene