title: Analysis of the Geometry of the Distal Femur and Proximal Tibia in the Osteoarthritic Knee: A 3D Reconstruction CT Scan Based Study of 449 Cases.
abstract: BACKGROUND
  The aim of this study is to evaluate the geometry of the distal femur and the proximal tibia in the osteoarthritic knee using 3D reconstructive CT scan imaging.
  
  
  METHODS
  449 patients with knee osteoarthritis were treated surgically in our center with patient-specific technology total knee arthroplasty. Preoperatively, all the patients underwent a CT scan according to a standard protocol. Using this database, the Hip-Knee-Angle (HKA), the Femur Valgus Angle (FVA), the Tibia Varus Angle (TVA), the Posterior Tibia Slope (PTS), and the angle between the posterior condylar axis and the anatomical transepicondylar axis (PCA) for each patient were recorded and statistically evaluated.
  
  
  RESULTS
  In overall, the mean HKA angle was 177.3±5.55, the mean FVA angle was 3.19±2.08, the mean TVA was 3.28±2.35, the PTS angle was 9.02±3.46, and the PCA angle was 2.86±0.78. Evaluation of the correlations between HKA and PCA (r=0.035), HKA and PTS (r=-0.047), and PCA and PTS (r=0.05) showed non-significant relationships (P=0.46, P=0.32, and P=0.29 respectively). No significant differences were revealed from the comparison of male patients with female patients, regarding the mean HKA, FVA, TVA, PTS, and PCA.
  
  
  CONCLUSIONS
  The posterior condylar axis is a well-defined but not a reliable axis, while the transepicondylar and the anteroposterior are reliable, but not easily defined axes. Given the large ranges and standard deviations of the location of posterior condylar axis, and the important inter- and intraobserver variability in the intraoperative location of the transepicondylar and the anteroposterior axes, the use of a preoperative 3D CT scan is recommended.
authors.affiliation: Sky Ridge Medical Center, Joint and Spine Department, Lone Tree, Colorado, USA.
authors.forename: Dimitrios N
authors.initials: DN
authors.lastname: Lyras
authors.affiliation: Sky Ridge Medical Center, Joint and Spine Department, Lone Tree, Colorado, USA.
authors.forename: Craig
authors.initials: C
authors.lastname: Loucks
authors.affiliation: Sky Ridge Medical Center, Joint and Spine Department, Lone Tree, Colorado, USA.
authors.forename: Robert
authors.initials: R
authors.lastname: Greenhow
keywords: 3D CT scan; Knee Geometry; Patient Specific Instruments; Posterior Condylar Axis; Total Knee Arthroplasty