title: Increased volumetric wear of polyethylene liners with more than 3 years of shelf-life time.
abstract: We analyzed 20 retrieved gamma-sterilized polyethylene liners (Biomet Hexloc). The long-term durability varied significantly depending on shelf-life time before implantation. Liners with a shelf-life time of 3 years or more evinced significantly ( P 0.002) higher volumetric wear than those with a shelf life time less than 3 years. Infrared spectroscopy and scanning calorimetry showed that all explanted implants underwent substantial in vivo oxidation and crystallization. The oxidative ageing of polyethylene renders the polyethylene liner susceptible to severe wear. Scanning electron microscopy of the bearing surface of the liner revealed abrasive wear as a dominant mechanism. Moreover, poor acetabular design produces excessively thin liners, substandard locking mechanism, and backside wear of the liner. The primary reason for severe wear in the Hexloc liner was poor modular design and oxidative degradation of the polyethylene.
authors.affiliation: Division of Orthopaedics, Department of Surgery, Tampere University Hospital, P.O. Box 2000, 33521 Tampere, Finland. ygit@yahoo.com
authors.forename: T J S
authors.initials: TJ
authors.lastname: Puolakka
authors.forename: J T
authors.initials: JT
authors.lastname: Keränen
authors.forename: K A
authors.initials: KA
authors.lastname: Juhola
authors.forename: K J J
authors.initials: KJ
authors.lastname: Pajamäki
authors.forename: P J
authors.initials: PJ
authors.lastname: Halonen
authors.forename: J K
authors.initials: JK
authors.lastname: Nevalainen
authors.forename: V
authors.initials: V
authors.lastname: Saikko
authors.forename: M U K
authors.initials: MU
authors.lastname: Lehto
authors.forename: M
authors.initials: M
authors.lastname: Järvinen
mesh_terms: D000328:Adult; D000368:Aged; D020099:Coated Materials, Biocompatible; D015331:Cohort Studies; D019544:Equipment Failure Analysis; D005260:Female; D006622:Hip Prosthesis; D006801:Humans; D008297:Male; D008422:Materials Testing; D008875:Middle Aged; D020959:Polyethylene / Q000737:chemistry*; D011336:Probability; D011474:Prosthesis Design; D011475:Prosthesis Failure; D018709:Statistics, Nonparametric; D013314:Stress, Mechanical; D013499:Surface Properties; D013718:Tensile Strength; D013997:Time Factors
chemical_list: D020099:Coated Materials, Biocompatible; D020959:Polyethylene