title: Radiographic outcome of limb-based versus knee-based patient specific guides in total knee arthroplasty.
abstract: BACKGROUND
  Patient specific guides (PSG's) were developed to improve overall component alignment in total knee arthroplasty (TKA). The aim of this study was to undertake a comparative radiographic study of two commonly used PSG and determine whether the radiographic technique used to construct the PSG had a significant effect on overall alignment.
  
  
  METHODS
  This prospective cohort study examined the accuracy of limb-based (n=112) versus knee-based (n=105) MR PSG in restoring the mechanical axis in three planes according to post-operative Perth CT scan protocol.
  
  
  RESULTS
  Limb-based MR and knee-based MR PSG systems both restored overall hip-knee-ankle angle (HKAA), femoral coronal alignment, tibial coronal alignment, femoral sagittal alignment, tibial sagittal alignment and femoral rotation alignment to within 3° of a neutral mechanical axis with similar precision (91.1% vs. 86.7% p=0.30, 97.3% vs. 96.2% p=0.63, 97.3% vs. 97.1% p=0.94, 94.6% vs. 89.4% p=0.16, 90.2% vs. 81.0% p=0.05, 91.1% vs. 86.7% p=0.30, respectively). However, when the secondary outcome measure of alignment within 2° was assessed, limb-based MR PSG restored HKAA, femoral coronal and tibial sagittal alignment with greater precision than knee-based MR PSG (73.2% vs. 64.8% p=0.016, 93.8% vs. 80.8% p=0.004 and 82.1% vs. 62.9% p=0.001, respectively).
  
  
  CONCLUSIONS
  The findings of this study recommend the use of limb-based MR PSG for improved precision in the restoration of neutral mechanical alignment over knee-based MR PSG in TKA.
  
  
  METHODS
  Therapeutic level III.
authors.affiliation: Department of Orthopaedic Surgery, The Canterbury Hospital, Canterbury, NSW, Australia.
authors.forename: Catherine
authors.initials: C
authors.lastname: Crane
authors.affiliation: Sydney Knee Specialists, St George Private Hospital, Sydney, NSW, Australia.
authors.forename: Kanniraj
authors.initials: K
authors.lastname: Marimuthu
authors.affiliation: Department of Orthopaedic Surgery, The Canterbury Hospital, Canterbury, NSW, Australia; Sydney Knee Specialists, St George Private Hospital, Sydney, NSW, Australia.
authors.forename: Darren B
authors.initials: DB
authors.lastname: Chen
authors.affiliation: Ingham Institute for Applied Medical Research, South Western Sydney Clinical School, UNSW, Australia.
authors.forename: Ian A
authors.initials: IA
authors.lastname: Harris
authors.affiliation: Bryant Radiology, St George Private Hospital, Sydney, NSW, Australia.
authors.forename: Emma
authors.initials: E
authors.lastname: Wheatley
authors.affiliation: Department of Orthopaedic Surgery, The Canterbury Hospital, Canterbury, NSW, Australia; Sydney Knee Specialists, St George Private Hospital, Sydney, NSW, Australia. Electronic address: samuelmacdessi@sydneyknee.com.au.
authors.forename: Samuel J
authors.initials: SJ
authors.lastname: MacDessi
mesh_terms: D000368:Aged; D019645:Arthroplasty, Replacement, Knee / Q000379:methods*; D017760:Bone Malalignment / Q000517:prevention & control; D005269:Femur / Q000033:anatomy & histology*; D006801:Humans; D007719:Knee Joint / Q000033:anatomy & histology*; D007720:Knee Prosthesis; D008279:Magnetic Resonance Imaging / Q000379:methods; D066230:Patient-Specific Modeling; D057285:Precision Medicine / Q000379:methods; D011446:Prospective Studies; D011474:Prosthesis Design; D013977:Tibia / Q000033:anatomy & histology*; D016896:Treatment Outcome
keywords: Alignment; CT Perth protocol; Knee arthroplasty; Patient specific guides; Radiographic outcomes