title: In vivo pre- and postoperative three-dimensional knee kinematics in unicompartmental knee arthroplasty.
abstract: BACKGROUND
  Pre- and postoperative knee kinematics in unicompartmental knee arthroplasty (UKA) can be theoretically related to clinical outcome and longevity after UKA with regard to ligament function and the degree of arthritic changes. However, the preoperative knee kinematics of patients indicated for UKA remain to be elucidated, and it is also unclear whether the preoperative kinematics can be maintained by the UKA procedure. The objective of this study was to examine the in vivo pre- and postoperative three-dimensional knee kinematics in UKA while referencing the normal knee kinematics reported in our previous study.
  
  
  METHODS
  We analyzed the knee kinematics in 17 knees (14 patients) undergoing UKA via a three-dimensional to two-dimensional registration technique employing femoral condylar translation and femoral axial rotation. The pre- and postoperative knee kinematics during squat motion were evaluated in the same subjects, employing consistent evaluation parameters.
  
  
  RESULTS
  On average, both pre- and postoperative knee kinematics in the range 10-100° of knee flexion demonstrated near-consistent femoral external rotation and anterior translation of the medial condyle and posterior translation of the lateral condyle. However, the mean femoral external rotation angle and the posterior translation of the lateral condyle postoperatively were significantly smaller than the values observed preoperatively.
  
  
  CONCLUSIONS
  Although the patterns of preoperative knee motion were similar to those seen in normal knees, the magnitude of this motion varied widely between patients, so it was not necessarily representative of normal knees. These variations may be due to the varying degrees of arthritic changes caused by osteoarthritis. Although the patterns of knee kinematics were largely maintained by the UKA procedure, the causes of the significant reductions in the magnitude of motion upon performing the UKA procedure should be investigated in subsequent studies with a larger number of patients.
authors.affiliation: Department of Orthopaedic Surgery, Niigata Medical Center, 3-27-11 Kobari, Nishi-ku, Niigata, Niigata 950-2022, Japan.
authors.forename: Tomoharu
authors.initials: T
authors.lastname: Mochizuki
authors.forename: Takashi
authors.initials: T
authors.lastname: Sato
authors.forename: Osamu
authors.initials: O
authors.lastname: Tanifuji
authors.forename: Kouichi
authors.initials: K
authors.lastname: Kobayashi
authors.forename: Yoshio
authors.initials: Y
authors.lastname: Koga
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Yamagiwa
authors.forename: Go
authors.initials: G
authors.lastname: Omori
authors.forename: Naoto
authors.initials: N
authors.lastname: Endo
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D000465:Algorithms; D019645:Arthroplasty, Replacement, Knee / Q000379:methods*; D001182:Arthroscopy; D001696:Biomechanical Phenomena; D005260:Female; D005471:Fluoroscopy; D005500:Follow-Up Studies; D006801:Humans; D021621:Imaging, Three-Dimensional; D007719:Knee Joint / Q000000981:diagnostic imaging / Q000503:physiopathology* / Q000601:surgery; D007720:Knee Prosthesis; D008297:Male; D008875:Middle Aged; D020370:Osteoarthritis, Knee / Q000000981:diagnostic imaging / Q000503:physiopathology / Q000601:surgery*; D011184:Postoperative Period; D057234:Preoperative Period; D011474:Prosthesis Design; D016059:Range of Motion, Articular / Q000502:physiology*; D015203:Reproducibility of Results; D014057:Tomography, X-Ray Computed / Q000379:methods*