title: Posterior reference guides do not always maintain the size of posterior femoral condyles in TKA.
abstract: OBJECTIVE
  Posterior reference guides are provided by many manufacturers. However, the true posterior femoral condyle bone resection thicknesses using posterior reference guides are not stated by the manufacturers. The purpose of this study was to analyse the influence of the posterior reference guide designs on the posterior femoral condyle bone resection thickness.
  
  
  METHODS
  Thickness of posterior femoral condyle bone resection and thickness of prostheses were investigated in 8 types of total knee prostheses using the production drawings provided by the manufacturers.
  
  
  RESULTS
  Posterior femoral condyle bone resection thickness differed between prostheses. Change in size of the medial posterior condyle ranged from -0.5 to 1.4 mm at 0° external rotation, from -2.9 to 1.4 mm at 3° external rotation, and from -5.3 to 1.4 mm at 6° external rotation. Change in size of lateral posterior condyle ranged from -0.5 to 1.4 mm at 0° external rotation, from -0.4 to 3.4 mm at 3° external rotation, and from -0.4 to 5.3 mm at 6° external rotation.
  
  
  CONCLUSIONS
  This study showed that posterior femoral condyle bone resection thickness was different for each posterior reference guide. The rotation centre of posterior reference guides influenced the bone resection thickness in the posterior femoral condyle. The size of the posterior femoral condyles increased in some guides but decreased in other guides. The maximum differences in size changes of the posterior femoral condyles between the guides were 1.9 mm at 0° external rotation, 4.1 mm at 3° external rotation, and 6.3 mm at 6° external rotation. To control the size of posterior femoral condyles, the posterior reference guide design should be checked before use.
authors.affiliation: Department of Orthopaedic Surgery, Osaka City University Graduate School of Medicine, 1-4-3 Asahi-machi, Abeno-ku, Osaka, 545-8585, Japan. yminoda@msic.med.osaka-cu.ac.jp.
authors.forename: Yukihide
authors.initials: Y
authors.lastname: Minoda
authors.affiliation: Department of Orthopaedic Surgery, Osaka City University Graduate School of Medicine, 1-4-3 Asahi-machi, Abeno-ku, Osaka, 545-8585, Japan.
authors.forename: Shigekazu
authors.initials: S
authors.lastname: Mizokawa
authors.affiliation: Department of Orthopaedic Surgery, Osaka City University Graduate School of Medicine, 1-4-3 Asahi-machi, Abeno-ku, Osaka, 545-8585, Japan.
authors.forename: Yoichi
authors.initials: Y
authors.lastname: Ohta
authors.affiliation: Department of Orthopaedic Surgery, Osaka City University Graduate School of Medicine, 1-4-3 Asahi-machi, Abeno-ku, Osaka, 545-8585, Japan.
authors.forename: Mitsuhiko
authors.initials: M
authors.lastname: Ikebuchi
authors.affiliation: Department of Orthopaedic Surgery, Osaka City University Graduate School of Medicine, 1-4-3 Asahi-machi, Abeno-ku, Osaka, 545-8585, Japan.
authors.forename: Maki
authors.initials: M
authors.lastname: Itokazu
authors.affiliation: Department of Orthopaedic Surgery, Osaka City University Graduate School of Medicine, 1-4-3 Asahi-machi, Abeno-ku, Osaka, 545-8585, Japan.
authors.forename: Kazumasa
authors.initials: K
authors.lastname: Yamamura
authors.affiliation: Department of Orthopaedic Surgery, Osaka City University Graduate School of Medicine, 1-4-3 Asahi-machi, Abeno-ku, Osaka, 545-8585, Japan.
authors.forename: Suguru
authors.initials: S
authors.lastname: Nakamura
authors.affiliation: Department of Orthopaedic Surgery, Osaka City University Graduate School of Medicine, 1-4-3 Asahi-machi, Abeno-ku, Osaka, 545-8585, Japan.
authors.forename: Hiroaki
authors.initials: H
authors.lastname: Nakamura
mesh_terms: D000368:Aged; D019645:Arthroplasty, Replacement, Knee; D001842:Bone and Bones / Q000502:physiology*; D005260:Female; D005269:Femur / Q000601:surgery; D006801:Humans; D007719:Knee Joint / Q000502:physiology* / Q000601:surgery*; D008297:Male; D008875:Middle Aged; D012399:Rotation
keywords: Posterior femoral condyle; Posterior reference guide; Rotation of femoral component; Total knee arthroplasty