title: A preclinical numerical assessment of a polyetheretherketone femoral component in total knee arthroplasty during gait.
abstract: BACKGROUND
  Conventional total knee replacement designs show high success rates but in the long term, the stiff metal components may affect bone quality of the distal femur. In this study we introduce an all-polymer total knee replacement device containing a PEEK femoral component on an UHMWPE tibial implant and study its mechanical integrity, fixation, and stress shielding of the periprosthetic femur.
  
  
  METHODS
  The implant was analysed in finite element simulations of level gait, adopted from the ISO 14243-1 standard. Mechanical integrity of the implant and underlying cement mantle were tested, and the fixation strength of the cement-implant interface was studied. Stress shielding was assessed based on strain energy density distributions in the distal femur. We compared PEEK and CoCr implants for mechanical performance and fixation, and compared both versions against an intact case to determine the change in bone strain energy density.
  
  
  RESULTS
  The mechanical integrity of the PEEK and CoCr components was similar in magnitude, but differences in stress patterns were found. Moreover, the cement mantle was loaded more heavily in the CoCr configuration. Under similar interface properties, the CoCr-cement interface was more at risk of failure than the PEEK-cement interface. The bone strain energy density distribution of the PEEK implant was similar to the intact case, while the CoCr implant showed signs of stress shielding, and a different distribution than the intact and PEEK models.
  
  
  CONCLUSIONS
  During gait, the PEEK femoral component performed similarly to CoCr, with no added risk for the cement mantle. The reduction in stress shielding for PEEK was evident and confirms the potential reduction in long-term loss of bone stock for this all-polymer knee implant.
authors.affiliation: Orthopaedic Research Laboratory, Radboud University Medical Center, Radboud Institute for Health Sciences, P.O. Box 9101, 6500 HB, Nijmegen, The Netherlands. Lennert.deRuiter@radboudumc.nl.
authors.forename: Lennert
authors.initials: L
authors.lastname: de Ruiter
authors.affiliation: Orthopaedic Research Laboratory, Radboud University Medical Center, Radboud Institute for Health Sciences, P.O. Box 9101, 6500 HB, Nijmegen, The Netherlands.
authors.forename: Dennis
authors.initials: D
authors.lastname: Janssen
authors.affiliation: Invibio Ltd, Thornton Cleveleys, Lancashire, FY5 4QD, UK.
authors.forename: Adam
authors.initials: A
authors.lastname: Briscoe
authors.affiliation: Orthopaedic Research Laboratory, Radboud University Medical Center, Radboud Institute for Health Sciences, P.O. Box 9101, 6500 HB, Nijmegen, The Netherlands.|Laboratory for Biomechanical Engineering, University of Twente, Enschede, The Netherlands.
authors.forename: Nico
authors.initials: N
authors.lastname: Verdonschot
keywords: Finite element analysis; Implant mechanical integrity; Polyetheretherketone; Stress shielding; Total knee arthroplasty