title: Influence of tibial rotation in total knee arthroplasty on knee kinematics and retropatellar pressure: an in vitro study.
abstract: OBJECTIVE
  Although continuous improvements have been made, there is still a considerable amount of unsatisfied patients after total knee arthroplasty (TKA). A main reason for this high percentage is anterior knee pain, which is supposed to be provoked by post-operative increased retropatellar peak pressure. Since rotational malalignment of the implant is believed to contribute to post-operative pain, the aim of this study was to examine the influence of tibial component rotation on knee kinematics and retropatellar pressure.
  
  
  METHODS
  Eight fresh-frozen knee specimens were tested in a weight-bearing knee rig after fixed-bearing TKA under a loaded squat from 20° to 120° of flexion. To examine tibial components with different rotations, special inlays with 3° internal rotation and 3° external rotation were produced and retropatellar pressure distribution was measured with a pressure-sensitive film. The kinematics of the patella and the femorotibial joint were recorded with an ultrasonic-based motion analysis system.
  
  
  RESULTS
  Retropatellar peak pressure decreased significantly from 3° internal rotation to neutral position and 3° external rotation of the tibial component (8.5 ± 2.3 vs. 8.2 ± 2.4 vs. 7.8 ± 2.5 MPa). Regarding knee kinematics femorotibial rotation and anterior-posterior translation, patella rotation and tilt were altered significantly, but relative changes remained minimal.
  
  
  CONCLUSIONS
  Changing tibial rotation revealed a high in vitro influence on retropatellar peak pressure. We recommend the rotational alignment of the tibial component to the medial third of the tibial tuberosity or even more externally beyond that point to avoid anterior knee pain after TKA.
authors.affiliation: Department of Orthopedic Surgery, Physical Medicine and Rehabilitation, University Hospital of Munich (LMU), Campus Grosshadern, Marchioninistr. 15, 81377, Munich, Germany. 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: Tatjana
authors.initials: T
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: 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
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
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D019645:Arthroplasty, Replacement, Knee; D001696:Biomechanical Phenomena; D017760:Bone Malalignment; D002102:Cadaver; D005260:Female; D006801:Humans; D066298:In Vitro Techniques; D007719:Knee Joint / Q000601:surgery*; D008297:Male; D008875:Middle Aged; D010329:Patella / Q000502:physiology*; D011312:Pressure; D016059:Range of Motion, Articular; D012399:Rotation; D013977:Tibia / Q000502:physiology*; D016474:Weight-Bearing
keywords: Anterior knee pain; Knee kinematics; Retropatellar pressure; Rotational malalignment; Tibial component; Total knee arthroplasty