title: Articular surface mounted navigated total knee arthroplasty improves the reliability of component alignment.
abstract: OBJECTIVE
  The primary aim was to compare the early knee-specific functional outcome after articular surface mounted (ASM) navigation with non-navigated TKA. The secondary aims were to compare general physical and mental health improvement, patient satisfaction, and reliability of component alignment in the sagittal and coronal planes between ASM navigated TKA with that of non-navigated TKA.
  
  
  METHODS
  Prospective functional outcome and radiographic data were collect for 123 patients undergoing ASM navigation and 172 patients undergoing non-navigated TKA by a high volume single surgeon. Pre-operative and one-year Oxford knee score (OKS) and short form (SF-) 12 scores were collected. Patient satisfaction was also assessed at one year. Implant position was assessed on post-operative radiographs (alpha, beta, gamma, and sigma angles) by a blinded observer.
  
  
  RESULTS
  There was no significant difference for improvement in OKS, SF-12 physical or mental components, or satisfaction between the groups one year following surgery. The non-navigation group was significantly more likely to have outliers (greater than 3 degrees) in femoral varus/valgus coronal alignment [odds ratio (OR) 4.5, 95% confidence interval (CI) 1.0-20.7, p = 0.049] and for posterior tibial slope (OR 8.3, 95% CI 1.1-65.0, p = 0.03).
  
  
  CONCLUSIONS
  ASM navigation significantly reduces the number of outliers for the femoral and tibial components when compared to conventional non-navigation alignment. However, the short-term functional outcome is not influenced by the surgical technique used. If the surgeon wants to reduce their number of outliers, then ASM navigation should be considered but the overall functional outcome in the short term is not influenced.
  
  
  METHODS
  III Therapeutic investigation, retrospective cohort study.
authors.affiliation: Department of Orthopaedics and Trauma, The Royal Infirmary of Edinburgh, Little France, Edinburgh, EH16 4SA, UK. nickclement@doctors.org.uk.
authors.forename: N D
authors.initials: ND
authors.lastname: Clement
authors.affiliation: University of Edinburgh, Edinburgh, UK.
authors.forename: D
authors.initials: D
authors.lastname: MacDonald
authors.affiliation: Department of Orthopaedics and Trauma, The Royal Infirmary of Edinburgh, Little France, Edinburgh, EH16 4SA, UK.
authors.forename: A G
authors.initials: AG
authors.lastname: Burgess
authors.affiliation: Department of Orthopaedics and Trauma, The Royal Infirmary of Edinburgh, Little France, Edinburgh, EH16 4SA, UK.
authors.forename: C R
authors.initials: CR
authors.lastname: Howie
mesh_terms: D000368:Aged; D019645:Arthroplasty, Replacement, Knee / Q000379:methods*; D005260:Female; D005269:Femur / Q000033:anatomy & histology; D006801:Humans; D007593:Joint Instability / Q000517:prevention & control*; D008297:Male; D008875:Middle Aged; D017060:Patient Satisfaction; D011446:Prospective Studies; D011859:Radiography; D015203:Reproducibility of Results; D012189:Retrospective Studies; D025321:Surgery, Computer-Assisted / Q000379:methods*
keywords: Alignment; Navigation; Outcome; Oxford knee score; Total knee arthroplasty