title: Factors affecting intraoperative kinematic patterns and flexion angles in navigated total knee arthroplasty.
abstract: OBJECTIVE
  To investigate the factors affecting intraoperative kinematics, as measured with a navigation system, and their effect on maximum flexion angles during total knee arthroplasty (TKA).
  
  
  METHODS
  One hundred posterior stabilised (PS) TKAs performed using an image-free navigation system were evaluated. Tibial internal rotation angles at maximum extension, 30°, 45°, 60°, 90°, and maximum flexion were collected at registration and after implantation. The varus angles from the coronal mechanical axis were also collected. The rotational patterns were divided into four groups to investigate whether flexion contracture and varus deformity affected the kinematic patterns, and correlated with the maximum pre- and post-operative flexion angles.
  
  
  RESULTS
  At registration, the flexion angles at maximum extension differed significantly between the kinematic groups; the flexion angle at maximum extension at registration was negatively correlated with the pre-operative maximum flexion angle (R(2) = 0.226, p < 0.0001) and the post-operative maximum flexion angle (R(2) = 0.059, p = 0.0167). Varus deformity at registration also differed significantly between the kinematic groups; varus deformity at registration was negatively correlated with the pre-operative maximum flexion angle (R(2) = 0.087, p = 0.0036) and post-operative maximum flexion angle (R(2) = 0.101, p = 0.0027).
  
  
  CONCLUSIONS
  Navigation-based measurements in patients undergoing PS TKA indicated that pre-operative flexion contracture and varus deformity are negatively correlated with both pre- and post-operative maximum flexion angles. The results may improve the ease with which surgeons can interpret intraoperative kinematics, by providing a multi-dimensional perspective. With further knowledge regarding intraoperative kinematics, it might be possible to improve surgical approach, prosthesis design, and clinical outcomes.
  
  
  METHODS
  II.
authors.affiliation: Department of Orthopaedic Surgery, Kobe Kaisei Hospital, 3-11-15, Shinohara-Kita, Nada, Kobe, 657-0068, Japan, wavedreamer17@yahoo.co.jp.
authors.forename: Kazunari
authors.initials: K
authors.lastname: Ishida
authors.forename: Nao
authors.initials: N
authors.lastname: Shibanuma
authors.forename: Tomoyuki
authors.initials: T
authors.lastname: Matsumoto
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Sasaki
authors.forename: Koji
authors.initials: K
authors.lastname: Takayama
authors.forename: Akihiko
authors.initials: A
authors.lastname: Toda
authors.forename: Ryosuke
authors.initials: R
authors.lastname: Kuroda
authors.forename: Masahiro
authors.initials: M
authors.lastname: Kurosaka
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D053587:Arthrometry, Articular; D019645:Arthroplasty, Replacement, Knee / Q000379:methods*; D001696:Biomechanical Phenomena / Q000502:physiology; D005260:Female; D006801:Humans; D007432:Intraoperative Period; D007719:Knee Joint / Q000503:physiopathology* / Q000601:surgery; D008297:Male; D008875:Middle Aged; D016059:Range of Motion, Articular / Q000502:physiology*; D012399:Rotation; D025321:Surgery, Computer-Assisted; D013977:Tibia / Q000503:physiopathology / Q000601:surgery