title: Computer navigation experience in hip resurfacing improves femoral component alignment using a conventional jig.
abstract: BACKGROUND
  The use of computer navigation has been shown to improve the accuracy of femoral component placement compared to conventional instrumentation in hip resurfacing. Whether exposure to computer navigation improves accuracy when the procedure is subsequently performed with conventional instrumentation without navigation has not been explored. We examined whether femoral component alignment utilizing a conventional jig improves following experience with the use of imageless computer navigation for hip resurfacing.
  
  
  METHODS
  Between December 2004 and December 2008, 213 consecutive hip resurfacings were performed by a single surgeon. The first 17 (Cohort 1) and the last 9 (Cohort 2) hip resurfacings were performed using a conventional guidewire alignment jig. In 187 cases, the femoral component was implanted using the imageless computer navigation. Cohorts 1 and 2 were compared for femoral component alignment accuracy.
  
  
  RESULTS
  All components in Cohort 2 achieved the position determined by the preoperative plan. The mean deviation of the stem-shaft angle (SSA) from the preoperatively planned target position was 2.2° in Cohort 2 and 5.6° in Cohort 1 (P = 0.01). Four implants in Cohort 1 were positioned at least 10° varus compared to the target SSA position and another four were retroverted.
  
  
  CONCLUSIONS
  Femoral component placement utilizing conventional instrumentation may be more accurate following experience using imageless computer navigation.
authors.affiliation: Department of Orthopaedic Surgery, St. Michael's Hospital, University of Toronto, Toronto, ON, Canada.
authors.forename: Zachary
authors.initials: Z
authors.lastname: Morison
authors.affiliation: Department of Orthopaedic Surgery, St. Michael's Hospital, University of Toronto, Toronto, ON, Canada.
authors.forename: Akshay
authors.initials: A
authors.lastname: Mehra
authors.affiliation: Department of Orthopaedic Surgery, St. Michael's Hospital, University of Toronto, Toronto, ON, Canada.
authors.forename: Michael
authors.initials: M
authors.lastname: Olsen
authors.affiliation: Department of Orthopaedic Surgery, St. Michael's Hospital, University of Toronto, Toronto, ON, Canada.
authors.forename: Michael
authors.initials: M
authors.lastname: Donnelly
authors.affiliation: Department of Orthopaedic Surgery, St. Michael's Hospital, University of Toronto, Toronto, ON, Canada.
authors.forename: Emil
authors.initials: E
authors.lastname: Schemitsch
keywords: Computer navigation; femoral component alignment; hip resurfacing