Updated: 10/12/2016

TKA Templating

Review Topic
  • Definition
    • the process of anticipating the size and position of implants prior to surgery
  • Importance
    • allows prediction of implant sizes needed to be available in operating room
    • provides a reliable starting point in determining size and position of implants
  • Accuracy
    • up to 92-100% accurate +/- one size
  • Steps
    • obtain appropriate radiographs
    • analyze radiographs for appropriate planning
    • ensure scale is correct between templates and radiographs
    • template femoral component
    • template tibial component
Radiographic Views
  • Necessary radiographs
    • AP weight-bearing radiograph of the knee 
    • lateral view of the knee 
      • most important view for templating
    • patellofemoral joint view 
      • not necessary for templating
  • Optional radiographs
    • full-length hip-to-ankle AP weight-bearing view 
      • can be used for templating
      • useful for 
        • ruling-out extra-articular deformity
        • estimating coronal laxity
        • planning bony cuts with respect to mechanical axis
  • Magnification
    • 20% is standard
      • most templates account for this
    • magnification markers are helpful
Radiographic Analysis
  • Step 1
    • assess the mechanical axis
      • draw a line of the hip-to-ankle view that shows the overall mechanical axis 
        • neutral mechanical axis should bisect the center of knee
  • Step 2
    • estimate magnitude of coronal deformity
      • measure the tibiofemoral angle 
  • Step 3
    • determine the femoral resection angle
      • difference between mechanical and anatomic axis of the femur 
  • Step 4
    • determine tibial bone cut
      • perpendicular to mechanical axis 
  • Step 5
    • assess bony defects and osteophytes
      • easiest to do on AP weight-bearing view
  • Step 6
    • assess tibial slope
      • completed on lateral radiograph 
  • Step 7
    • assess patellar height
      • completed on lateral radiograph 
      • assess for patella baja
        • this will make exposure more difficult
  • Step 8
    • assess patellar shift/tilt 
      • completed on skyline view of patella
Template the Femur
  • Steps
    • choose appropriate implant size on lateral radiograph  
      • restore posterior condylar offset  
      • avoid notching
    • assess this size component on the AP to determine medial/lateral positioning and ensure no overhang  
      • if there is significant overhang, may have to consider downsizing  
Template the Tibia
  • Steps
    • choose appropriate size based on lateral radiograph  
      • ensure no overhang
      • aim to match native tibial slope
    • assess this component size on the AP to determine medial/lateral positioning and ensure no overhang  
      • consider downsizing if there is any overhang  

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