title: Sagittal plane kinematics of fixed- and mobile-bearing total knee replacements.
abstract: OBJECTIVE
  The objective of this prospective, randomized, patient- and observer-blinded study was to analyze, in vivo, the knee joint kinematics in the sagittal plane in a patient population that had received either a fixed or a mobile TKA.
  
  
  METHODS
  Thirty-one patients (57 knees) were evaluated by means of fluoroscopy during unloaded flexion and extension against gravity as well as during step up and step down with full weight bearing. In these 31 patients, 22 fixed-bearing TKAs, 16 mobile-bearing TKAs, and 19 natural knee joints were included. Fluoroscopic radiographs were evaluated by measuring the "patella tendon angle" in relation to the knee flexion angle, as a measure of anteroposterior translation, as well as the "kinematic index," as a measure of reproducibility.
  
  
  RESULTS
  During unloaded movement, fluoroscopic analysis did not show a significant difference between both types of prosthesis design and the natural knee. In the weight-bearing movement, both types of TKA designs revealed a more linear patellar tendon angle curve, with a greater angle in extension and in flexion than in the natural knees. In the mobile-bearing group, interindividual deviations from the mean during weight-bearing movements were significantly less than in the fixed-bearing group.
  
  
  CONCLUSIONS
  No functional advantage of mobile-bearing TKA over fixed-bearing devices could be found. Both TKA designs showed the typical kinematics of an anterior instability. These results only apply to cruciate retaining mobile-bearing TKA with a bearing that allows both rotation and anteroposterior translation, using a sagittal plane kinematics analysis evaluated by such methodology. A possible influence of less variability of the kinematic pattern on clinical results still needs to be confirmed.
authors: Sporthopaedicum Straubing, Bahnhofplatz 8, 94315 Straubing, Germany. carsten@tibesku.de
authors: Carsten O
authors: CO
authors: Tibesku
authors: Kiriakos
authors: K
authors: Daniilidis
authors: Volker
authors: V
authors: Vieth
authors: Adrian
authors: A
authors: Skwara
authors: Walter
authors: W
authors: Heindel
authors: Susanne
authors: S
authors: Fuchs-Winkelmann
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D000704:Analysis of Variance; D019645:Arthroplasty, Replacement, Knee / Q000009:adverse effects / Q000379:methods*; D001696:Biomechanical Phenomena; D003936:Diagnosis, Computer-Assisted / Q000379:methods; D004311:Double-Blind Method; D005260:Female; D005471:Fluoroscopy / Q000379:methods; D005500:Follow-Up Studies; D006801:Humans; D007593:Joint Instability / Q000175:diagnosis* / Q000517:prevention & control; D007720:Knee Prosthesis; D008297:Male; D008875:Middle Aged; D015588:Observer Variation; D020370:Osteoarthritis, Knee / Q000000981:diagnostic imaging / Q000601:surgery; D017847:Patellar Ligament / Q000601:surgery; D011446:Prospective Studies; D011474:Prosthesis Design; D016059:Range of Motion, Articular / Q000502:physiology*; D020127:Recovery of Function; D018709:Statistics, Nonparametric; D016896:Treatment Outcome; D016474:Weight-Bearing