title: Sagittal kinematics of mobile unicompartmental knee replacement in anterior cruciate ligament deficient knees.
abstract: BACKGROUND
  There is a greater risk of tibial component loosening when mobile unicompartmental knee replacement is performed in anterior cruciate ligament deficient knees. We previously reported on a cohort of anterior cruciate ligament deficient patients (n=46) who had undergone surgery, but no difference was found in implant survivorship at a mean 5-year follow-up. The purpose of this study was to examine the kinematic behaviour of a subcohort of these patients.
  
  
  METHODS
  The kinematic behaviour of anterior cruciate deficient knees (n=16) after mobile unicompartmental knee replacement was compared to matched intact knees (n=16). Sagittal plane knee fluoroscopy was taken while patients performed step-up and forward lunge exercises. The patellar tendon angle, knee flexion angle and implant position was calculated for each video frame.
  
  
  RESULTS
  The patellar tendon angle was 5° lower in the deficient group, indicating greater anterior tibial translation compared to the intact group between 30 and 40° of flexion. Large variability, particularly from 40-60° of flexion, was observed in the bearing position of the deficient group, which may represent different coping mechanisms. The deficient group took 38% longer to perform the exercises.
  
  
  CONCLUSIONS
  Kinematic differences were found between the deficient and intact knees after mobile unicompartmental knee replacement; but these kinematic changes do not seem to affect the medium-term clinical outcome. Whether these altered knee kinematics will have a clinical impact is as yet undetermined, but more long-term outcome data is required before mobile unicompartmental knee replacement can be recommended for an anterior cruciate ligament deficient patient.
authors.affiliation: Nuffield Department of Orthopaedics, Rheumatology and Musculoskeletal Sciences, University of Oxford, Oxford, United Kingdom. Electronic address: elise.pegg@ndorms.ox.ac.uk.
authors.forename: Elise C
authors.initials: EC
authors.lastname: Pegg
authors.affiliation: Orthopaedics and Traumatology Unit, San Donà di Piave General Hospital, Venice, Italy.
authors.forename: Francesco
authors.initials: F
authors.lastname: Mancuso
authors.affiliation: Nuffield Department of Orthopaedics, Rheumatology and Musculoskeletal Sciences, University of Oxford, Oxford, United Kingdom.
authors.forename: Mona
authors.initials: M
authors.lastname: Alinejad
authors.affiliation: Nuffield Department of Orthopaedics, Rheumatology and Musculoskeletal Sciences, University of Oxford, Oxford, United Kingdom.
authors.forename: Bernard H
authors.initials: BH
authors.lastname: van Duren
authors.affiliation: Department of Engineering Science, University of Oxford, Oxford, United Kingdom.
authors.forename: John J
authors.initials: JJ
authors.lastname: O'Connor
authors.affiliation: Nuffield Department of Orthopaedics, Rheumatology and Musculoskeletal Sciences, University of Oxford, Oxford, United Kingdom.
authors.forename: David W
authors.initials: DW
authors.lastname: Murray
authors.affiliation: Nuffield Department of Orthopaedics, Rheumatology and Musculoskeletal Sciences, University of Oxford, Oxford, United Kingdom.
authors.forename: Hemant G
authors.initials: HG
authors.lastname: Pandit
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D016118:Anterior Cruciate Ligament / Q000473:pathology*; D019645:Arthroplasty, Replacement, Knee / Q000379:methods*; D001696:Biomechanical Phenomena; D016022:Case-Control Studies; D005260:Female; D005471:Fluoroscopy; D006801:Humans; D007593:Joint Instability / Q000000981:diagnostic imaging / Q000209:etiology; D007719:Knee Joint / Q000000981:diagnostic imaging / Q000503:physiopathology / Q000601:surgery*; D008297:Male; D008875:Middle Aged; D017847:Patellar Ligament / Q000601:surgery; D016059:Range of Motion, Articular; D013977:Tibia / Q000601:surgery
keywords: Anterior cruciate ligament; Function; Knee kinematics; Patellar Tendon Angle; Unicompartmental knee replacement