title: Different femorotibial contact on the weight-bearing: midflexion between normal and varus aligned knees after total knee arthroplasty.
abstract: OBJECTIVE
  The influence of residual malalignment on biomechanical analysis after total knee arthroplasty (TKA) is currently uncertain. The hypothesis is that postoperative alignment would influence the in vivo kinematics after TKA, under weight-bearing conditions but not under non-weight-bearing condition. The purpose of the present study was to compare weight-bearing and non-weight-bearing conditions and to evaluate the effect of the postoperative alignment on the in vivo kinematics after posterior cruciate ligament-retaining TKA during midflexion using 2-dimensional/3-dimensional registration.
  
  
  METHODS
  Thirty knees of 30 patients with pre-operative varus deformity were divided into 2 groups according to their postoperative alignment: the normal alignment group (N = 21) and the varus alignment group (N = 9).
  
  
  RESULTS
  Under weight-bearing conditions, the varus alignment group showed a significant posterior displacement of the medial femoral condyle (flexion: 80°, 90° P < 0.05) and a significant anterior displacement of the lateral femoral condyle (flexion: 10° P < 0.01, 20° P < 0.05, and extension: 10°, 20° P < 0.01, 30°, 40° P < 0.05) as compared with the normal alignment group. In contrast, no significant difference in the medial and lateral femoral condyle positions under non-weight-bearing conditions was observed between the normal and varus alignment groups.
  
  
  CONCLUSIONS
  The postoperative alignment influenced knee kinematics under weight-bearing conditions. The weight load influenced knee kinematics through posterior tibial slope and induced greater lateral femoral condyle mobility, which might explain the better clinical and functional outcome. These findings contribute to gaining a proper understanding of the in vivo kinematics of the postoperative varus alignment and might be useful for orthopaedic surgeons in the achievement of patient satisfaction.
  
  
  METHODS
  III.
authors: Department of Orthopedic Surgery, Chugoku Rousai Hospital, 1-5-1 Hirotagaya, Kure, Hiroshima, 737-0193, Japan, eisaku-fjm@umin.ac.jp.
authors: Eisaku
authors: E
authors: Fujimoto
authors: Yoshiaki
authors: Y
authors: Sasashige
authors: Tetsuya
authors: T
authors: Tomita
authors: Kenji
authors: K
authors: Kashiwagi
authors: Amiko
authors: A
authors: Inoue
authors: Mikiya
authors: M
authors: Sawa
authors: Yuki
authors: Y
authors: Ota
mesh_terms: D000368:Aged; D019645:Arthroplasty, Replacement, Knee; D001696:Biomechanical Phenomena / Q000502:physiology; D005260:Female; D006801:Humans; D007719:Knee Joint / Q000000981:diagnostic imaging / Q000503:physiopathology* / Q000601:surgery; D008297:Male; D011859:Radiography; D016474:Weight-Bearing / Q000502:physiology*