title: Partial restoration of knee kinematics in severe valgus deformity using the medial-pivot total knee arthroplasty.
abstract: OBJECTIVE
  The objectives of the study were to examine knee kinematics in knees with severe valgus deformities and to compare pre- and post-operative knee kinematics for the same subjects implanted with medial-pivot total knee arthroplasty (TKA).
  
  
  METHODS
  Seven subjects with severe valgus deformities due to osteoarthritis (OA) or rheumatoid arthritis (RA) were enrolled in the prospective study. Prior to TKA, three-dimensional (3D) kinematics were assessed by 3D to 2D registration technique using the image matching software 'Knee Motion', under in vivo, weight-bearing conditions. Postoperatively, each subject again performed the same motion under fluoroscopic surveillance.
  
  
  RESULTS
  Preoperative kinematics demonstrated external rotation of tibias from extension to flexion, and small posterior femoral translations dominated in the medial condyle associated with anterior slides during partial range of motion. Postoperatively, these non-physiological tibial rotations were restored, and most subjects exhibited small internal rotations of tibias. On average, preoperative tibial internal rotation was -4.7° ± 7.6° from full extension to maximum flexion, and the angle was 4.8° ± 3.1° postoperatively (p = 0.01). In addition, small amounts of posterior translation of the lateral condyle and anterior translation of the medial condyle were confirmed in most subjects postoperatively.
  
  
  CONCLUSIONS
  The study showed that the preoperative kinematic pattern established in severe valgus deformity was different from the physiological knee pattern. In addition, post-operative results suggest that the non-physiological kinematics were partially restored after TKA by using the prosthesis design even in the absence of the posterior cruciate ligament (PCL) and the cam-post mechanism.
authors.affiliation: Department of Orthopaedic Surgery, Hyogo Rehabilitation Center Hospital, 1070 Akebono-cho, Nishi-ku, Kobe, Hyogo, 651-2181, Japan, a_kitagawa@hwc.or.jp.
authors.forename: Atsushi
authors.initials: A
authors.lastname: Kitagawa
authors.forename: Kazunari
authors.initials: K
authors.lastname: Ishida
authors.forename: Takaaki
authors.initials: T
authors.lastname: Chin
authors.forename: Nobuhiro
authors.initials: N
authors.lastname: Tsumura
authors.forename: Tetsushiro
authors.initials: T
authors.lastname: Iguchi
mesh_terms: D000368:Aged; D001172:Arthritis, Rheumatoid / Q000000981:diagnostic imaging / Q000503:physiopathology / Q000601:surgery; D019645:Arthroplasty, Replacement, Knee / Q000379:methods*; D001696:Biomechanical Phenomena; D005260:Female; D005471:Fluoroscopy; D006801:Humans; D007719:Knee Joint / Q000000981:diagnostic imaging / Q000503:physiopathology / Q000601:surgery; D007720:Knee Prosthesis; D020370:Osteoarthritis, Knee / Q000000981:diagnostic imaging / Q000503:physiopathology / Q000601:surgery; D011446:Prospective Studies; D016059:Range of Motion, Articular / Q000502:physiology; D012399:Rotation; D016474:Weight-Bearing / Q000502:physiology