title: A method for assessing joint line shift post knee arthroplasty considering the preoperative joint space.
abstract: BACKGROUND
  Accurate comparison of outcomes regarding various surgical options in knee arthroplasty can benefit from an improved method for joint line analysis that takes into account the preoperative joint space.
  
  
  METHODS
  This article describes a new preoperative-based registration method that measures changes in the joint line by overlaying the 3D models of the bones with implants using preoperative CT along with preoperative and postoperative biplanar radiography. The method was tested on six cadaveric specimens for measuring alteration to the medial and lateral joint lines in extension and flexion.
  
  
  RESULTS
  The joint line shift, when measured using the new method, was in the range of -0.2 to 1.3 mm on average (SD=1.3 to 3.8 mm, for medial and lateral, in flexion and extension positions). This was significantly different (p≤0.01) from the results of a previous postoperative-based registration method which did not account for the cartilage thickness in calculating alterations of the joint line (mean=3.9 to 6.8mm, SD=1.2 to 4.3 mm).
  
  
  CONCLUSIONS
  These results further highlight the importance of considering the preoperative joint space in analyzing the joint line, and demonstrate the utility of the newly introduced method for accurate assessment of changes in the joint line after arthroplasty.
  
  
  CONCLUSIONS
  The introduced method provides accurate means for investigating joint line alterations in relation to different surgical techniques and the subsequent biomechanical effects after knee arthroplasty.
authors.affiliation: Department of Orthopaedics, University of British Columbia, Vancouver, BC, Canada; Centre for Hip Health and Mobility (CHHM), Robert H.N. Ho Research Centre, Vancouver, BC, Canada. Electronic address: shahramiri@gmail.com.
authors.forename: Shahram
authors.initials: S
authors.lastname: Amiri
authors.affiliation: Department of Orthopaedics, University of British Columbia, Vancouver, BC, Canada.
authors.forename: Bassam A
authors.initials: BA
authors.lastname: Masri
authors.affiliation: Biomedical Engineering, University of Calgary, Calgary, AB, Canada; Department of Civil Engineering, University of Calgary, Calgary, AB, Canada; McCaig Institute for Bone and Joint Health, University of Calgary, Calgary, AB, Canada.
authors.forename: Carolyn
authors.initials: C
authors.lastname: Anglin
authors.affiliation: Department of Orthopaedics, University of British Columbia, Vancouver, BC, Canada; Centre for Hip Health and Mobility (CHHM), Robert H.N. Ho Research Centre, Vancouver, BC, Canada.
authors.forename: David R
authors.initials: DR
authors.lastname: Wilson
mesh_terms: D019645:Arthroplasty, Replacement, Knee; D002102:Cadaver; D005269:Femur / Q000000981:diagnostic imaging / Q000601:surgery; D006801:Humans; D007091:Image Processing, Computer-Assisted; D021621:Imaging, Three-Dimensional; D007719:Knee Joint / Q000000981:diagnostic imaging* / Q000601:surgery; D007720:Knee Prosthesis; D011184:Postoperative Period; D057234:Preoperative Period; D017755:Prosthesis Fitting; D012984:Software; D013977:Tibia / Q000000981:diagnostic imaging / Q000601:surgery; D014057:Tomography, X-Ray Computed
keywords: Arthroplasty; Joint line; Joint space; Knee; Total knee arthroplasty; Total knee replacement