title: Does flexion of the femoral implant in total knee arthroplasty increase knee flexion: a randomised controlled trial.
abstract: BACKGROUND
  Prosthetic and operative modifications in total knee arthroplasty (TKA) have been proposed to maximise post-operative knee flexion as it is essential in routine functional activities.
  
  
  METHODS
  We performed a double blind randomised controlled trial to compare clinical outcomes of primary cruciate-retaining TKA for osteoarthritis with the femoral component implanted in either 4° flexion in the sagittal plane (F) or in a neutral position (C). The primary outcome of knee flexion and secondary outcomes knee extension, quadriceps strength, WOMAC, SF-12v2, timed stand test, stair climb test and satisfaction were assessed at 1 year. Knee flexion and extension were also assessed intra-operatively. Implant flexion was measured from true lateral radiographs.
  
  
  RESULTS
  Thirty-nine participants (40 knees) were recruited, 20 knees per group. Three subjects from the control group and two from the flexed group were lost to 1 year follow-up but numbers were sufficient to satisfy the sample size calculation. Significant differences were found between the groups in knee flexion (F: 113.6±8.8° pre-operative, 122.4±6.0° intra-operative, 110.2±7.5° 1 year, C: 117.4±11.7°, 117.4±7.6°, 103.5±10.7°. p=0.031) and mental component score of the SF12-v2 (F 53.3±13.2, C 61.1±7.3, p=0.009) but there were no significant differences in other outcomes and patients were equally satisfied.
  
  
  CONCLUSIONS
  Flexing the femoral implant in this cruciate retaining TKA system provided a significant difference in knee flexion compared to a neutral position. The improvement appears to occur predominantly at surgery and was not associated with a clinical or functional benefit at 1 year. (ACTRN12606000325505).
  
  
  METHODS
  Level 1; randomised controlled trial.
authors.affiliation: Mater Medical Research Institute, Mater Health Services, Raymond Terrace, South Brisbane, Australia, 4101. Electronic address: michael.murphy@mater.org.au.
authors.forename: Michael
authors.initials: M
authors.lastname: Murphy
authors.affiliation: School of Health and Rehabilitation Science, University of Queensland, St Lucia, Australia, 4076.
authors.forename: Simon
authors.initials: S
authors.lastname: Journeaux
authors.affiliation: Faculty of Health Sciences, Australian Catholic University, Banyo, Australia, 4014.
authors.forename: Julie
authors.initials: J
authors.lastname: Hides
authors.affiliation: Mater Medical Research Institute, Mater Health Services, Raymond Terrace, South Brisbane, Australia, 4101.
authors.forename: Trevor
authors.initials: T
authors.lastname: Russell
mesh_terms: D000368:Aged; D000704:Analysis of Variance; D019645:Arthroplasty, Replacement, Knee / Q000379:methods*; D004311:Double-Blind Method; D005260:Female; D005269:Femur / Q000601:surgery*; D006801:Humans; D007719:Knee Joint / Q000601:surgery; D007720:Knee Prosthesis; D008297:Male; D053580:Muscle Strength; D053581:Muscle Strength Dynamometer; D020370:Osteoarthritis, Knee / Q000601:surgery; D017060:Patient Satisfaction; D017755:Prosthesis Fitting; D016059:Range of Motion, Articular