title: Wear performance of neat and vitamin E blended highly cross-linked PE under severe conditions: The combined effect of accelerated ageing and third body particles during wear test.
abstract: The objective of this study is to evaluate the effects of third-body particles on the in vitro wear behaviour of three different sets of polyethylene acetabular cups after prolonged testing in a hip simulator and accelerated ageing. Vitamin E-blended, cross-linked polyethylene (XLPE_VE), cross-linked polyethylene (XLPE) and conventional polyethylene (STD_PE) acetabular cups were simulator tested for two million cycles under severe conditions (i.e. by adding third-body particles to the bovine calf serum lubricant). Micro-Fourier Transform Infrared and micro-Raman spectroscopic analyses, differential scanning calorimetry, and crosslink density measurements were used to characterize the samples at a molecular level. The STD_PE cups had twice mass loss than the XLPE_VE components and four times than the XLPE samples; statistically significant differences were found between the mass losses of the three sets of cups. The observed wear trend was justified on the basis of the differences in cross-link density among the samples (XLPE>XLPE_VE>STD_PE). FTIR crystallinity profiles, bulk DSC crystallinity and surface micro-Raman crystallinity seemed to have a similar behaviour upon testing: all of them (as well as the all-trans and ortho-trans contents) revealed the most significant changes in XLPE and XLPE_VE samples. The more severe third-body wear testing conditions determined more noticeable changes in all spectroscopic markers with respect to previous tests. Unexpectedly, traces of bulk oxidation were found in both STD_PE (unirradiated) and XLPE (remelting-stabilized), which were expected to be stable to oxidation; on the contrary, XLPE_VE demonstrated a high oxidative stability in the present, highly demanding conditions.
authors: Medical Technology Laboratory, Rizzoli Orthopaedic Institute, Bologna, Italy. Electronic address: affatato@tecno.ior.it.
authors: Saverio
authors: S
authors: Affatato
authors: Medical Technology Laboratory, Rizzoli Orthopaedic Institute, Bologna, Italy.
authors: Jonathan Salvatore
authors: JS
authors: De Mattia
authors: Chemistry Department and Nanostructured Interfaces and Surfaces (NIS) Centre, University of Turin, Via Giuria 7, 10125 Turin, Italy.
authors: Pierangiola
authors: P
authors: Bracco
authors: Dipartimento di Scienze Biomediche e Neuromotorie, Università di Bologna, Via Belmeloro 8/2, 40126 Bologna, Italy.
authors: Eleonora
authors: E
authors: Pavoni
authors: Dipartimento di Scienze Biomediche e Neuromotorie, Università di Bologna, Via Belmeloro 8/2, 40126 Bologna, Italy.
authors: Paola
authors: P
authors: Taddei
mesh_terms: D000077:Acetabulum; D000818:Animals; D002417:Cattle; D006622:Hip Prosthesis; D008422:Materials Testing; D011095:Polyethylenes / Q000737:chemistry*; D011475:Prosthesis Failure; D014810:Vitamin E / Q000737:chemistry*
chemical_list: D011095:Polyethylenes; D014810:Vitamin E
keywords: Accelerated ageing; Hip simulator; Micro-Raman spectroscopy; Oxidation; Third-body particles; Vitamin E