title: Mechanical properties of human bone-implant interface tissue in aseptically loose hip implants.
abstract: The main cause of failure in total hip replacement is aseptic loosening which is associated with the formation of a periprosthetic fibrous (interface) tissue. Despite important applications for finite element modeling of loose implants, the mechanical properties of the bone-implant interface tissue have never been measured in humans. In this study, we performed unconfined compression tests to characterize the mechanical properties of the interface tissue and to determine the parameters of various hyperelastic material models which were fitted to the measurements. Human interface tissues were retrieved during 21 elective revision surgeries from aseptically loosened cemented (N=10) and uncemented hip implants (N=11). Specimens were tested at a fixed deformation rate of 0.1mm/min up to a maximum force of 10N. Elastic moduli for low and high strain regions of the stress-strain curves were determined. Interface tissue from aseptically loose cemented prostheses shows higher elastic moduli (mean=1.85MPa, 95% C.I.=1.76-1.95MPa) in the high strain region as compared to that of the interface tissue from the cementless group (mean=1.65MPa, 95% C.I.=1.43-1.88MPa). The 5-terms Mooney-Rivlin model ( [Formula: see text] ) described the stress-strain behavior the best. Large variations in the mechanical behavior were observed both between specimens from the same patient as between those of different patients. The material model parameters were therefore estimated for the mean data as well as for the curves with the highest and lowest strain at the maximum load. The model parameters found for the mean data were C1=-0.0074MPa, C2=0.0019MPa, C3=0MPa, C4=-0.0032MPa and C5=0MPa in the cemented group and C1=-0.0137MPa, C2=0.0069MPa, C3=0.0026MPa, C4=-0.0094MPa and C5=0MPa in the cementless group. The results of this study can be used in finite element computer.
authors.affiliation: Biomechanics and Imaging Group, Department of Orthopaedics, Leiden University Medical Center, P.O. Box 9600, Leiden 2300RC, The Netherlands; Department of Biomechanical Engineering, Delft University of Technology, Mekelweg 2, Delft 2628CD, The Netherlands. Electronic address: g.kraaij@lumc.nl.
authors.forename: Gert
authors.initials: G
authors.lastname: Kraaij
authors.affiliation: Department of Biomechanical Engineering, Delft University of Technology, Mekelweg 2, Delft 2628CD, The Netherlands.
authors.forename: Amir A
authors.initials: AA
authors.lastname: Zadpoor
authors.affiliation: Department of Biomechanical Engineering, Delft University of Technology, Mekelweg 2, Delft 2628CD, The Netherlands; Department of Orthopedic Surgery, Academic Medical Center, Meibergdreef 9, Amsterdam 1105 AZ, The Netherlands.
authors.forename: Gabrielle J M
authors.initials: GJ
authors.lastname: Tuijthof
authors.affiliation: Department of Biomechanical Engineering, Delft University of Technology, Mekelweg 2, Delft 2628CD, The Netherlands.
authors.forename: Jenny
authors.initials: J
authors.lastname: Dankelman
authors.affiliation: Biomechanics and Imaging Group, Department of Orthopaedics, Leiden University Medical Center, P.O. Box 9600, Leiden 2300RC, The Netherlands.
authors.forename: Rob G H H
authors.initials: RG
authors.lastname: Nelissen
authors.affiliation: Biomechanics and Imaging Group, Department of Orthopaedics, Leiden University Medical Center, P.O. Box 9600, Leiden 2300RC, The Netherlands; Department of Biomechanical Engineering, Delft University of Technology, Mekelweg 2, Delft 2628CD, The Netherlands.
authors.forename: Edward R
authors.initials: ER
authors.lastname: Valstar
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D019644:Arthroplasty, Replacement, Hip; D019245:Compressive Strength; D055119:Elastic Modulus; D005260:Female; D006621:Hip Joint / Q000166:cytology*; D006622:Hip Prosthesis; D006801:Humans; D008297:Male; D008422:Materials Testing; D055595:Mechanical Phenomena; D008875:Middle Aged; D008954:Models, Biological; D011475:Prosthesis Failure
keywords: Biomechanics; Hip; Interface membrane; Loosening; Prosthesis