title: Radiological method for measuring patellofemoral tracking and tibiofemoral kinematics before and after total knee replacement.
abstract: OBJECTIVE
  Numerous complications following total knee replacement (TKR) relate to the patellofemoral (PF) joint, including pain and patellar maltracking, yet the options for in vivo imaging of the PF joint are limited, especially after TKR. We propose a novel sequential biplane radiological method that permits accurate tracking of the PF and tibiofemoral (TF) joints throughout the range of movement under weightbearing, and test it in knees pre- and post-arthroplasty.
  
  
  METHODS
  A total of three knees with end-stage osteoarthritis and three knees that had undergone TKR at more than one year's follow-up were investigated. In each knee, sequential biplane radiological images were acquired from the sagittal direction (i.e. horizontal X-ray source and 10° below horizontal) for a sequence of eight flexion angles. Three-dimensional implant or bone models were matched to the biplane images to compute the six degrees of freedom of PF tracking and TF kinematics, and other clinical measures.
  
  
  RESULTS
  The mean and standard deviation for the six degrees of freedom of PF tracking and TF kinematics were computed. TF and PF kinematics were highly accurate (< 0.9 mm, < 0.6°) and repeatable.
  
  
  CONCLUSIONS
  The developed method permitted measuring of in vivo PF tracking and TF kinematics before and after TKR throughout the range of movement. This method could be a useful tool for investigating differences between cohorts of patients (e.g., with and without pain) impacting clinical decision-making regarding surgical technique, revision surgery or implant design.
authors.affiliation: University of Calgary, 3280 Hospital Drive NW, Calgary, Alberta T2N 4Z6, Canada.
authors.forename: G B
authors.initials: GB
authors.lastname: Sharma
authors.forename: S K
authors.initials: SK
authors.lastname: Saevarsson
authors.forename: S
authors.initials: S
authors.lastname: Amiri
authors.forename: S
authors.initials: S
authors.lastname: Montgomery
authors.forename: H
authors.initials: H
authors.lastname: Ramm
authors.forename: D D
authors.initials: DD
authors.lastname: Lichti
authors.forename: R
authors.initials: R
authors.lastname: Lieck
authors.forename: S
authors.initials: S
authors.lastname: Zachow
authors.forename: C
authors.initials: C
authors.lastname: Anglin
keywords: 2D-3D registration; Kinematics; Patellar tracking; TKA; Total knee replacement; X-ray imaging