title: Fluoroscopic motion study confirming the stability of a medial pivot design total knee arthroplasty.
abstract: BACKGROUND
  The ideal total knee arthroplasty should provide maximum range of motion and functional stability for all desired daily activities. The SAIPH™ (MatOrtho; UK) knee has a medial pivot knee kinematic pattern designed to achieve medial stability and an asymmetric posterior translation of the lateral femoral condyle during knee flexion and in this way attempts to mimic the natural knee motion. This study aims to analyze knee kinematics of the SAIPH™ total knee arthroplasty (TKA) by videofluoroscopy during four different weightbearing activities.
  
  
  METHODS
  Fourteen consecutive patients operated on by a single surgeon, with a minimum follow-up of 24 months were included in this IRB-approved study. There were no exclusions based on patient's functional level. A medially conforming knee was implanted in all cases. Participants in the study were asked to perform the clinically relevant functional activities of pivoting, kneeling, lungeing and step-up/down activities while their knee motion was recorded by videofluoroscopy.
  
  
  RESULTS
  Maximum knee flexion during the kneeling activity mean 127° (100°-155°). An asymmetric posterior translation of the lateral femoral condyle (LFC) was observed during pivoting, kneeling, lungeing and stepping. No paradoxical anterior translation of the femoral condyles was observed in any activity.
  
  
  CONCLUSIONS
  The kinematics observed in this implant are similar in pattern, although smaller in magnitude, to normal functional knees, showing a posterior translation of the lateral femoral condyle during knee flexion, with internal rotation of the tibia, and no paradoxical anterior motion in any of the four weight bearing activities.
authors.affiliation: Melbourne Orthopaedic Group, 33 The Avenue, Windsor, Victoria, Australia. Electronic address: ashimmin@mog.com.au.
authors.forename: Andrew
authors.initials: A
authors.lastname: Shimmin
authors.affiliation: Melbourne Orthopaedic Group, 33 The Avenue, Windsor, Victoria, Australia. Electronic address: drsaramartinez@gmail.com.
authors.forename: Sara
authors.initials: S
authors.lastname: Martinez-Martos
authors.affiliation: Olympic Park Imaging, AAMI Park, Entrance F/60 Olympic BLV, Melbourne, Australia. Electronic address: j.owens@iop.net.au.
authors.forename: John
authors.initials: J
authors.lastname: Owens
authors.affiliation: Orthopaedic Research Laboratory, West Palm Beach, FL, USA. Electronic address: alex.i@ufl.edu.
authors.forename: Alex D
authors.initials: AD
authors.lastname: Iorgulescu
authors.affiliation: Orthopaedic Research Laboratory, West Palm Beach, FL, USA. Electronic address: banks@ufl.edu.
authors.forename: Scott
authors.initials: S
authors.lastname: Banks
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D019645:Arthroplasty, Replacement, Knee; D005260:Female; D005471:Fluoroscopy / Q000379:methods*; D005500:Follow-Up Studies; D006801:Humans; D007719:Knee Joint / Q000000981:diagnostic imaging / Q000503:physiopathology* / Q000601:surgery; D007720:Knee Prosthesis; D008297:Male; D008875:Middle Aged; D009068:Movement / Q000502:physiology*; D020370:Osteoarthritis, Knee / Q000000981:diagnostic imaging / Q000503:physiopathology / Q000601:surgery; D011187:Posture / Q000502:physiology*; D011474:Prosthesis Design; D016059:Range of Motion, Articular / Q000502:physiology*; D013997:Time Factors; D016474:Weight-Bearing / Q000502:physiology
keywords: Fluoroscopy; Kinematics; Medial pivot; Prosthetic design; Total knee arthroplasty