title: In vivo kinematic analysis of posterior-stabilized total knee arthroplasty for the valgus knee operated by the gap-balancing technique.
abstract: BACKGROUND
  Most in vivo kinematic studies of total knee arthroplasty (TKA) report on the varus knee. The objective of the present study was to evaluate in vivo kinematics of a posterior-stabilized fixed-bearing TKA operated on a valgus knee during knee bending in weight-bearing (WB) and non-weight-bearing (NWB).
  
  
  METHODS
  A total of sixteen valgus knees in 12 cases that underwent TKA with Scorpio NRG PS knee prosthesis and that were operated on using the gap balancing technique were evaluated. We evaluated the in vivo kinematics of the knee using fluoroscopy and femorotibial translation relative to the tibial tray using a 2-dimensional to 3-dimensional registration technique.
  
  
  RESULTS
  The average flexion angle was 111.3°±7.5° in WB and 114.9° ± 8.4° in NWB. The femoral component demonstrated a mean external rotation of 5.9° ± 5.8° in WB and 7.4° ± 5.2° in NWB. In WB and NWB, the femoral component showed a medial pivot pattern from 0° to midflexion and a bicondylar rollback pattern from midflexion to full flexion. The medial condyle moved similarly in the WB condition and in the NWB condition. The lateral condyle moved posteriorly at a slightly earlier angle during the WB condition than during the NWB condition.
  
  
  CONCLUSIONS
  We conclude that similar kinematics after TKA can be obtained with the gap balancing technique for the preoperative valgus deformity when compared to the kinematics of a normal knee, even though the magnitude of external rotation was small.
  
  
  METHODS
  IV.
authors.affiliation: Department of Orthopaedic Surgery, Hokkaido Orthopaedic Memorial Hospital, Sapporo, Japan. Electronic address: kojisuzu3434@ac.auone-net.jp.
authors.forename: Koji
authors.initials: K
authors.lastname: Suzuki
authors.affiliation: Department of Orthopaedic Surgery, Hokkaido Orthopaedic Memorial Hospital, Sapporo, Japan.
authors.forename: Noriyuki
authors.initials: N
authors.lastname: Hara
authors.affiliation: Department of Orthopaedic Surgery, Hokkaido Orthopaedic Memorial Hospital, Sapporo, Japan.
authors.forename: Susumu
authors.initials: S
authors.lastname: Mikami
authors.affiliation: Department of Orthopaedic Biomaterial Science, Osaka University Graduate School of Medicine, Suita, Osaka, Japan.
authors.forename: Tetsuya
authors.initials: T
authors.lastname: Tomita
authors.affiliation: Department of Orthopaedic Biomaterial Science, Osaka University Graduate School of Medicine, Suita, Osaka, Japan.
authors.forename: Keiji
authors.initials: K
authors.lastname: Iwamoto
authors.affiliation: Center for Advanced Medical Engineering and Informatics, Osaka University, Suita, Osaka, Japan.
authors.forename: Takaharu
authors.initials: T
authors.lastname: Yamazaki
authors.affiliation: Department of Orthopaedic Biomaterial Science, Osaka University Graduate School of Medicine, Suita, Osaka, Japan.
authors.forename: Kazuomi
authors.initials: K
authors.lastname: Sugamoto
authors.affiliation: Department of Orthopaedic Surgery, Hokkaido Orthopaedic Memorial Hospital, Sapporo, Japan.
authors.forename: Shigeo
authors.initials: S
authors.lastname: Matsuno
mesh_terms: D000368:Aged; D001172:Arthritis, Rheumatoid / Q000150:complications / Q000503:physiopathology / Q000601:surgery; D019645:Arthroplasty, Replacement, Knee / Q000379:methods*; D001696:Biomechanical Phenomena / Q000502:physiology; D015331:Cohort Studies; D005260:Female; D056304:Genu Valgum / Q000209:etiology / Q000503:physiopathology* / Q000601:surgery*; D006801:Humans; D007720:Knee Prosthesis; D008297:Male; D008875:Middle Aged; D020370:Osteoarthritis, Knee / Q000150:complications / Q000503:physiopathology / Q000601:surgery; D016059:Range of Motion, Articular / Q000502:physiology*; D012399:Rotation; D016474:Weight-Bearing / Q000502:physiology
keywords: 2D/3D registration; Gap balancing; Kinematics; Posterior stabilized total knee arthroplasty; Valgus knee