Miller AG, Purtill JJ
Preoperative planning is an important aspect of total joint arthroplasty. Although significant attention has been given to how total hip arthroplasty templates are magnified, total knee arthroplasty (TKA) digital templating magnification methods have not been compared.
In this study, 50 patients undergoing TKA by the same surgeon were digitally templated using 2 common digital magnification methods to determine if there is any difference in accuracy or precision. Radiographs were randomly chosen to include a 25-mm magnification marker (MM) at the level of the joint or no magnification marker with uniform 115% magnification (NM).
There was no statistical difference between templated and actual component sizes. Preoperative templating determined the exact component size in 64% of femurs and 60% of tibias using the NM technique. Femurs were slightly oversized (mean, 0.2 femur size), whereas tibias had no such trend. In MM templating, 52% of femurs and 48% of tibias were exact.
Various methods of digital templating—the new standard of preoperative templating—provide no clear advantage over one another. The benefit of templating in TKA appears to be 2-fold: the surgeon can reliably predict a range of implant sizes needed and can ascertain a reliable starting point in determining implant size and position.