title: Femorotibial kinematics and load patterns after total knee arthroplasty: An in vitro comparison of posterior-stabilized versus medial-stabilized design.
abstract: BACKGROUND
  Femorotibial kinematics and contact patterns vary greatly with different total knee arthroplasty (TKA) designs. Therefore, guided motion knee systems were developed to restore natural knee kinematics and make them more predictable. The medial stabilized TKA design is supposed to replicate physiological kinematics more than the posterior-stabilized TKA system. We conducted this study to compare a newly developed medial stabilized design with a conventional posterior-stabilized design in terms of femorotibial kinematics and contact patterns in vitro.
  
  
  METHODS
  Twelve fresh-frozen knee specimens were tested in a weight-bearing knee rig after implantation of a posterior stabilized and medial-stabilized total knee arthroplasty under a loaded squat from 20° to 120° of flexion. Femorotibial joint contact pressures in the medial and lateral compartments were measured by pressure sensitive films and knee kinematics were recorded by an ultrasonic 3-dimensional motion analysis system.
  
  
  RESULTS
  The medial stabilized design showed a reduction of medial femorotibial translation compared to posterior-stabilized design (mean 3.5mm compared to 15.7 mm, P<0.01). In the lateral compartment, both designs showed a posterior translation of the femur with flexion, but less in the medial stabilized design (mean 14.7 mm compared to 19.0mm, P<0.01). In the medial femorotibial compartment of medial stabilized design, we observed an enlarged contact area and lower peak pressure, in contrast in the lateral compartment there was a reduced contact area and an increased peak pressure.
  
  
  CONCLUSIONS
  While posterior-stabilized design enforces a medio-lateral posterior translation, the medial stabilized arthroplasty system enables a combination of a lateral translation with a medial pivot, which restores the physiological knee kinematics better.
authors.affiliation: Department of Orthopedic Surgery, Physical Medicine and Rehabilitation, University Hospital of Munich (LMU), Campus Grosshadern, Marchioninistr, 15, 81377 Munich, Germany. Electronic address: arnd.steinbrueck@med.uni-muenchen.de.
authors.forename: Arnd
authors.initials: A
authors.lastname: Steinbrück
authors.affiliation: Department of Orthopedic Surgery, Physical Medicine and Rehabilitation, University Hospital of Munich (LMU), Campus Grosshadern, Marchioninistr, 15, 81377 Munich, Germany.
authors.forename: Christian
authors.initials: C
authors.lastname: Schröder
authors.affiliation: Department of Orthopedic Surgery, Physical Medicine and Rehabilitation, University Hospital of Munich (LMU), Campus Grosshadern, Marchioninistr, 15, 81377 Munich, Germany.
authors.forename: Matthias
authors.initials: M
authors.lastname: Woiczinski
authors.affiliation: Department of Orthopedic Surgery, Physical Medicine and Rehabilitation, University Hospital of Munich (LMU), Campus Grosshadern, Marchioninistr, 15, 81377 Munich, Germany.
authors.forename: Andreas
authors.initials: A
authors.lastname: Fottner
authors.affiliation: 1st Orthopaedic Clinic, 1st Medical Faculty, Charles University, Prague, Czech Republic.
authors.forename: Vera
authors.initials: V
authors.lastname: Pinskerova
authors.affiliation: Department of Orthopedic Surgery, Physical Medicine and Rehabilitation, University Hospital of Munich (LMU), Campus Grosshadern, Marchioninistr, 15, 81377 Munich, Germany.
authors.forename: Peter E
authors.initials: PE
authors.lastname: Müller
authors.affiliation: Department of Orthopedic Surgery, Physical Medicine and Rehabilitation, University Hospital of Munich (LMU), Campus Grosshadern, Marchioninistr, 15, 81377 Munich, Germany.
authors.forename: Volkmar
authors.initials: V
authors.lastname: Jansson
mesh_terms: D000328:Adult; D000368:Aged; D019645:Arthroplasty, Replacement, Knee / Q000295:instrumentation*; D001696:Biomechanical Phenomena; D002102:Cadaver; D005260:Female; D005269:Femur / Q000502:physiology / Q000601:surgery; D006801:Humans; D007719:Knee Joint / Q000502:physiology*; D007720:Knee Prosthesis; D008297:Male; D008875:Middle Aged; D011312:Pressure; D011474:Prosthesis Design; D016059:Range of Motion, Articular / Q000502:physiology; D013977:Tibia / Q000502:physiology / Q000601:surgery; D016474:Weight-Bearing / Q000502:physiology
keywords: Femorotibial pressure distribution; In vitro study; Knee kinematics; Medial stabilized; Posterior stabilized; Total knee arthroplasty