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 Manual templating is up to 92-100% accurate +/- one size Automatic templating only 51% 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 Alignement strategies mechanical alignment TKA Kinematic Alignment Mechanical alignment Goal achieve neutral mechanical axis with the hip, knee center, and ankle in alignment (0° ± 3°) Femoral component positioned perpendicular to the mechanical axis of the femur (typically 5-7° of valgus relative to the anatomical axis) Tibial component positioned perpendicular to the mechanical axis of the tibia (0° varus/valgus) aim is too avoid too much accidental varus Femoral rotation set using either the surgical transepicondylar axis (TEA) or 3° external rotation to the posterior condyles Soft tissue considerations templating anticipates need for ligament releases to achieve balanced rectangular gaps in extension and flexion Kinematic Alignment Goal restore pre-arthritic joint line anatomy and native knee kinematics Femoral component aligned to the cylindrical axis of the posterior femoral condyles (the native flexion-extension axis) typically resulting in -0.7° to -1.8° more valgus positioning than Mechanical Alignment Tibial component positioned to match the pre-arthritic tibial joint line typically resulting in more varus alignment usually 1.2° to 2.2° more varus than Mechanical Alignment Tibial slope restored to match native posterior slope approximately 1.2° more slope than mechanical alignment Resection planning equal thickness resections from medial and lateral femoral condyles and tibial plateaus to match cartilage and bone loss Soft tissue considerations aims to preserve native ligament balance without releases; fewer soft tissue releases anticipated 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 Pitfalls is to oversize the femoral component consistently less accurate than templating the tibia 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 Pitfalls equally likely to oversize and undersize intraoperative decision making more likely to lead surgeons to downsize the component