Updated: 10/12/2016

TKA Templating

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Questions
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Evidence
3
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Techniques
2
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
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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Technique Guides (2)
Questions (1)

(SAE07HK.79) Figure 48a shows the full-leg standing radiograph of a patient with a prior femoral fracture. Figure 48b shows the lateral view of the same joint. The patient is scheduled to undergo total knee arthroplasty. Because the mechanical axis of the lower extremity in patients with a prior femoral fracture may be disrupted, which of the following should be used during surgery to restore the mechanical axis of the lower extremity in this patient? Review Topic

QID: 6039
FIGURES:
1

Customized components

20%

(101/504)

2

Specialized intramedullary jigs

16%

(79/504)

3

Hinged prosthesis

5%

(23/504)

4

Extra-articular osteotomy

28%

(142/504)

5

Routine knee prosthesis

31%

(154/504)

ML 5

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PREFERRED RESPONSE 5
ARTICLES (4)
Topic COMMENTS (3)
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