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Updated: Jun 11 2021

TKA Templating

Images
https://upload.orthobullets.com/topic/12303/images/ap_weightbearing.jpg
https://upload.orthobullets.com/topic/12303/images/correct_slope.jpg
https://upload.orthobullets.com/topic/12303/images/femoral_template_ap.jpg
https://upload.orthobullets.com/topic/12303/images/femoral_template_lateral.jpg
https://upload.orthobullets.com/topic/12303/images/lateral.jpg
https://upload.orthobullets.com/topic/12303/images/oversized_tibial_component.jpg
  • Introduction
    • 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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