title: The effect of pelvic movement on the accuracy of hip centre location acquired using an imageless navigation system.
abstract: OBJECTIVE
  The aim of this study was to assess the accuracy of an imageless navigation system in localising the hip centre and to evaluate the effect of pelvic movement on the accuracy of hip centre acquisition.
  
  
  METHODS
  A phantom leg was constructed to simulate the hip joint and upper femur. A 3D measurement device was used to measure precisely the co-ordinates of hip centre. A limber link simulated hip motion as used when defining the hip centre during computer-assisted surgery. The data generated by the 3D measurement device and the image-free navigation system was compared with increasing amounts of simulated pelvic movement.
  
  
  RESULTS
  For moderate pelvic movement (5 mm) the mean error of the hip centre ranged between 1.5 mm and 3.9 mm with a corresponding angular error of between 0.25° and 0.64°. In conditions of excessive pelvic movement (15 mm) the mean error was 11.7 mm corresponding to an angular error of 1.9°.
  
  
  CONCLUSIONS
  This in vitro study showed accurate acquisition of the centre of hip with a surgical navigation system. These data suggest that during TKA using this computer assisted navigation system, the accuracy of insertion will not be significantly affected by moderate pelvic movement during data acquisition.
authors.affiliation: Service de chirurgie orthopédique, Centre Albert Trillat, Hôpital de la Croix Rousse, 103, Grande Rue de la Croix Rousse, 69004, Lyon, France. sebastien.lustig@chu-lyon.fr
authors.forename: Sebastien
authors.initials: S
authors.lastname: Lustig
authors.forename: Cyrille
authors.initials: C
authors.lastname: Fleury
authors.forename: Elvire
authors.initials: E
authors.lastname: Servien
authors.forename: Guillaume
authors.initials: G
authors.lastname: Demey
authors.forename: Philippe
authors.initials: P
authors.lastname: Neyret
authors.forename: Simon T
authors.initials: ST
authors.lastname: Donell
mesh_terms: D019645:Arthroplasty, Replacement, Knee / Q000379:methods*; D017760:Bone Malalignment / Q000517:prevention & control; D005270:Femur Head / Q000033:anatomy & histology; D006621:Hip Joint / Q000033:anatomy & histology*; D006801:Humans; D016343:Monitoring, Intraoperative / Q000379:methods*; D009068:Movement; D010388:Pelvis / Q000502:physiology*; D019047:Phantoms, Imaging; D015203:Reproducibility of Results; D025321:Surgery, Computer-Assisted / Q000379:methods*