title: Reliability of navigated lower limb alignment in high tibial osteotomies.
abstract: BACKGROUND
  Navigation allows for determination of the mechanical axis of the lower extremity during high tibial osteotomy (HTO) procedures. The objectives of this study were to (1) evaluate the reliability of noninvasive registration with an image-free navigation system for HTO and (2) determine the accuracy of the navigation system to monitor changes in lower limb alignment as compared with alignment measured with a novel 3-dimensional computed tomography method.
  
  
  OBJECTIVE
  Navigated limb alignment demonstrates good reliability and accuracy in all 3 planes.
  
  
  METHODS
  Descriptive laboratory study.
  
  
  METHODS
  Thirteen cadaver legs were used to examine the intra- and interobserver registration reliability of 3 observers. Initial coronal, sagittal, and axial alignment was measured on 6 legs, 3 times each, at intervals >36 hours. Navigated HTOs were then performed on all 13 legs, pre- and postoperative alignment was recorded, and data were compared with equivalent measures obtained by 3-dimensional computed tomography. Reliability and accuracy data were both analyzed using intraclass correlation coefficients with the following established thresholds: good, >0.75; fair, 0.4 to 0.75; and poor, <0.4.
  
  
  RESULTS
  Intraclass correlation coefficients for intraobserver reliability were categorized as follows: varus-valgus, good; flexion-extension, fair; and femoral-tibial rotation, poor. For interobserver reliability, results were varus-valgus, fair; flexion-extension, fair; and femoral-tibial rotation, poor. Intraclass correlation coefficients for navigation accuracy were varus-valgus, good; tibial slope, good; and tibial torsion, poor. Maximum differences in navigation-computed tomography measurements were Delta varus-valgus angle, 4.5 degrees; Delta tibial slope, 8.8 degrees; and Delta tibial torsion, 16.5 degrees.
  
  
  CONCLUSIONS
  Navigation may be reliable and clinically useful for dynamic monitoring of coronal leg alignment but has limits in determination of sagittal and axial plane alignment.
authors.affiliation: Orthopaedic Department, Hospital for Special Surgery, New York, NY 10021, USA.
authors.forename: Patrick
authors.initials: P
authors.lastname: Goleski
authors.forename: Blaine
authors.initials: B
authors.lastname: Warkentine
authors.forename: Darrick
authors.initials: D
authors.lastname: Lo
authors.forename: Cassie
authors.initials: C
authors.lastname: Gyuricza
authors.forename: Daniel
authors.initials: D
authors.lastname: Kendoff
authors.forename: Andrew D
authors.initials: AD
authors.lastname: Pearle
mesh_terms: D006801:Humans; D007866:Leg / Q000033:anatomy & histology; D015588:Observer Variation; D010027:Osteotomy / Q000379:methods*; D015203:Reproducibility of Results; D025321:Surgery, Computer-Assisted / Q000379:methods*; D013977:Tibia / Q000601:surgery*