title: Computer-assisted navigation for the intraoperative assessment of lower limb alignment in high tibial osteotomy can avoid outliers compared with the conventional technique.
abstract: OBJECTIVE
  Longterm outcomes after valgization high tibial osteotomy (HTO) to treat varus osteoarthritis seem to depend mainly on correction precision. Intraoperative assessment of leg alignment based on radiological visualization of the mechanical axis is difficult and its precision is limited. A promising approach to improving precision is to make use of navigation systems. The case-control study reported here involved the evaluation of patients whose varus osteoarthritis had been treated by open-wedge high tibial ostoetomy, and an analysis of the effect of computer-guided navigation on postoperative leg alignment.
  
  
  METHODS
  Forty patients with medial varus osteoarthritis managed by open-wedge high tibial osteotomy using a surgical navigation system were included in the present study (Group 1). They were compared with a retrospective control group (Group 2) of 40 patients with respect to postoperative leg alignment, correlation of planned and definitive correction, and postoperative deviation from the Fujisawa point.
  
  
  RESULTS
  The mean values for planned and definitive correction showed no significant differences for identical demographic data. As a percentage of the width of the tibial plateau the postoperative weight-bearing radiographs showed a mechanical line that intersected with the knee base line at the desired value of 62% (Fujisawa point) in 58.8% (SD ± 6.1) in Group 1 and in 58.6% (SD ± 8.1) in Group 2. Despite similar mean values a significantly higher number of corrections were outside the reference area (n = 7) in the non-navigated group, whereby all corrections were within the desired range in the navigated group. There were no significant differences in operation time.
  
  
  CONCLUSIONS
  This study showed that the use of a navigation system can not increase the precision of the open-wedge HTO procedure in patients with varus osteoarthritis but it can eliminate the outliers of a well defined range.
  
  
  METHODS
  Case-control study, Retrospective comparative study, Level III.
authors: Department of Orthopedic Surgery and Traumatology, Freiburg University Hospital, Hugstetter Str. 55, 79098, Freiburg, Germany. kilian.reising@uniklinik-freiburg.de
authors: Kilian
authors: K
authors: Reising
authors: Peter C
authors: PC
authors: Strohm
authors: Oliver
authors: O
authors: Hauschild
authors: Hagen
authors: H
authors: Schmal
authors: Mohmed
authors: M
authors: Khattab
authors: Norbert P
authors: NP
authors: Südkamp
authors: Philipp
authors: P
authors: Niemeyer
mesh_terms: D000328:Adult; D005260:Female; D056305:Genu Varum / Q000150:complications / Q000000981:diagnostic imaging / Q000601:surgery*; D006801:Humans; D007719:Knee Joint / Q000000981:diagnostic imaging / Q000601:surgery*; D007866:Leg / Q000033:anatomy & histology* / Q000000981:diagnostic imaging / Q000601:surgery; D008297:Male; D016555:Matched-Pair Analysis; D008875:Middle Aged; D020370:Osteoarthritis, Knee / Q000150:complications / Q000000981:diagnostic imaging / Q000601:surgery*; D010027:Osteotomy / Q000295:instrumentation / Q000379:methods*; D011859:Radiography; D012189:Retrospective Studies; D025321:Surgery, Computer-Assisted / Q000295:instrumentation / Q000379:methods*; D013977:Tibia / Q000000981:diagnostic imaging / Q000601:surgery*; D016896:Treatment Outcome