title: Hip contact forces in asymptomatic total hip replacement patients differ from normal healthy individuals: Implications for preclinical testing.
abstract: BACKGROUND
  Preclinical durability testing of hip replacement implants is standardised by ISO-14242-1 (2002) which is based on historical inverse dynamics analysis using data obtained from a small sample of normal healthy individuals. It has not been established whether loading cycles derived from normal healthy individuals are representative of loading cycles occurring in patients following total hip replacement.
  
  
  METHODS
  Hip joint kinematics and hip contact forces derived from multibody modelling of forces during normal walking were obtained for 15 asymptomatic total hip replacement patients and compared to 38 normal healthy individuals and to the ISO standard for pre-clinical testing.
  
  
  RESULTS
  Hip kinematics in the total hip replacement patients were comparable to the ISO data and the hip contact force in the normal healthy group was also comparable to the ISO cycles. Hip contact forces derived from the asymptomatic total hip replacement patients were comparable for the first part of the stance period but exhibited 30% lower peak loads at toe-off.
  
  
  CONCLUSIONS
  Although the ISO standard provides a representative kinematic cycle, the findings call into question whether the hip joint contact forces in the ISO standard are representative of those occurring in the joint following total hip replacement.
authors: Institute of Medical and Biological Engineering, School of Mechanical Engineering, University of Leeds, LS2 9JT, UK.
authors: Junyan
authors: J
authors: Li
authors: Leeds Institute for Rheumatic and Musculoskeletal Medicine, School of Medicine, University of Leeds, LS2 9JT, UK; NIHR Leeds Biomedical Research Unit, Leeds Teaching Hospitals Trust, Leeds, UK.
authors: Anthony C
authors: AC
authors: Redmond
authors: Institute of Medical and Biological Engineering, School of Mechanical Engineering, University of Leeds, LS2 9JT, UK; NIHR Leeds Biomedical Research Unit, Leeds Teaching Hospitals Trust, Leeds, UK; School of Mechanical Engineering, Xi'an Jiaotong University, Xi'an, China.
authors: Zhongmin
authors: Z
authors: Jin
authors: Institute of Medical and Biological Engineering, School of Mechanical Engineering, University of Leeds, LS2 9JT, UK; NIHR Leeds Biomedical Research Unit, Leeds Teaching Hospitals Trust, Leeds, UK.
authors: John
authors: J
authors: Fisher
authors: Leeds Teaching Hospitals Trust, Chapel Allerton Hospital, Leeds, UK; NIHR Leeds Biomedical Research Unit, Leeds Teaching Hospitals Trust, Leeds, UK.
authors: Martin H
authors: MH
authors: Stone
authors: Institute of Medical and Biological Engineering, School of Mechanical Engineering, University of Leeds, LS2 9JT, UK; NIHR Leeds Biomedical Research Unit, Leeds Teaching Hospitals Trust, Leeds, UK. Electronic address: T.D.Stewart@leeds.ac.uk.
authors: Todd D
authors: TD
authors: Stewart
mesh_terms: D000328:Adult; D000368:Aged; D019644:Arthroplasty, Replacement, Hip / Q000379:methods*; D001696:Biomechanical Phenomena; D015331:Cohort Studies; D005260:Female; D005684:Gait; D006621:Hip Joint / Q000601:surgery*; D006801:Humans; D008297:Male; D008875:Middle Aged; D019736:Prostheses and Implants; D013314:Stress, Mechanical; D016138:Walking
keywords: Arthroplasty; Contact forces; Hip; Kinematics; Preclinical testing; Wear