title: Preoperative varus-valgus kinematic pattern throughout flexion persists more strongly after cruciate-retaining than after posterior-stabilized total knee arthroplasty.
abstract: BACKGROUND
  Restoration of normal knee kinematics is key to improving patient satisfaction and functional outcomes after total knee arthroplasty (TKA). However, the effect of preoperative varus-valgus kinematics due to knee osteoarthritis on the postoperative kinematics is unclear. The function of the knee ligament contributes to both knee stability and kinematics. The aim of this study was to evaluate changes in varus-valgus kinematics before and after TKA using a navigation system, in addition to comparing the pre- and postoperative changes in kinematic patterns between cruciate-retaining (CR)- and posterior-stabilized (PS)-TKAs.
  
  
  METHODS
  Forty knees treated with TKA were evaluated (CR-TKA 20; PS-TKA 20). Manual mild passive knee flexion was applied while moving the leg from full extension to flexion. The varus-valgus angle was automatically measured by a navigation system at every 10° of the flexion angle, and the kinematics were evaluated.
  
  
  RESULTS
  Kinematic patterns throughout flexion can be classified into five types. The pre- and postoperative kinematic patterns were similar in 60% of patients who underwent CR-TKA, whereas they were similar in only 25% of those who underwent PS-TKA. The mean change in the size of the varus-valgus angle throughout flexion did not differ between CR-TKA and PS-TKA. However, the distribution of changes in the size of the varus-valgus angle differed between CR-TKA and PS-TKA.
  
  
  CONCLUSIONS
  We obtained the following results: 1) some patterns of varus-valgus kinematics are noted under unloading conditions despite recovery of neutral alignment in extension and 2) the preoperative varus-valgus kinematic pattern persisted more strongly after CR-TKA than after PS-TKA.
authors.affiliation: Department of Orthopedic Surgery, Ehime University Graduate School of Medicine, Toon, Ehime, Japan. Electronic address: taimisaki@gmail.com.
authors.forename: Kazunori
authors.initials: K
authors.lastname: Hino
authors.affiliation: Department of Orthopedic Surgery, Ehime University Graduate School of Medicine, Toon, Ehime, Japan. Electronic address: keishomth@gmail.com.
authors.forename: Yoshio
authors.initials: Y
authors.lastname: Oonishi
authors.affiliation: Department of Orthopedic Surgery, Ehime University Graduate School of Medicine, Toon, Ehime, Japan. Electronic address: kutsuna@m.ehime-u.ac.jp.
authors.forename: Tatsuhiko
authors.initials: T
authors.lastname: Kutsuna
authors.affiliation: Department of Orthopedic Surgery, Ehime University Graduate School of Medicine, Toon, Ehime, Japan. Electronic address: watamori.1010@gmail.com.
authors.forename: Kunihiko
authors.initials: K
authors.lastname: Watamori
authors.affiliation: Department of Orthopedic Surgery, Ehime University Graduate School of Medicine, Toon, Ehime, Japan. Electronic address: yasutake2257@gmail.com.
authors.forename: Yasutake
authors.initials: Y
authors.lastname: Iseki
authors.affiliation: Department of Orthopedic Surgery, Ehime University Graduate School of Medicine, Toon, Ehime, Japan. Electronic address: hirokiyomatsu@gmail.com.
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Kiyomatsu
authors.affiliation: Department of Orthopedic Surgery, Ehime University Graduate School of Medicine, Toon, Ehime, Japan. Electronic address: seiji-wa@m.ehime-u.ac.jp.
authors.forename: Seiji
authors.initials: S
authors.lastname: Watanabe
authors.affiliation: Department of Orthopedic Surgery, Ehime University Graduate School of Medicine, Toon, Ehime, Japan. Electronic address: hmiura8@gmail.com.
authors.forename: Hiromasa
authors.initials: H
authors.lastname: Miura
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D019645:Arthroplasty, Replacement, Knee / Q000379:methods*; D001696:Biomechanical Phenomena; D017760:Bone Malalignment / Q000517:prevention & control; D056304:Genu Valgum / Q000503:physiopathology* / Q000601:surgery; D056305:Genu Varum / Q000503:physiopathology* / Q000601:surgery; D006801:Humans; D021621:Imaging, Three-Dimensional; D007719:Knee Joint / Q000503:physiopathology* / Q000601:surgery; D008023:Ligaments, Articular / Q000503:physiopathology / Q000601:surgery; D008875:Middle Aged; D020370:Osteoarthritis, Knee / Q000503:physiopathology* / Q000601:surgery; D011184:Postoperative Period; D057234:Preoperative Period; D016059:Range of Motion, Articular; D025321:Surgery, Computer-Assisted
keywords: Alignment; Kinematics; Mid-flexion alignment; Total knee arthroplasty; Varus–valgus