How useful is templating for total knee replacement component sizing?

This study aims to assess the accuracy of digital templating at our institution, by comparing the templated component sizes with those implanted, and to determine whether templating the preoperative films had any measurable difference on the radiographic outcome, and if, where there was a mismatch between the implanted and templated sizes, the templated size would have been preferable. While a number of studies have evaluated the accuracy of both acetate and digital templating, none has to our knowledge looked back at post-operative radiographs and reviewed these in light of the templated and implanted sizes. Data was collected from 90 PFC Sigma (DePuy, UK) total knee replacements done sequentially, 45 of whom were templated digitally using a calibrating ball and Agfa Orthopaedic Tools software. Postoperative radiographs were graded independently for correct sizing. All templates were within one size of the implanted prosthesis. The femoral component appeared to be more often oversized on the postoperative radiographs in the non-templated group. In addition, most tibial trays that were found be too small had been templated to a larger size. There was a trend towards tibial trays templated too large to have been templated to a smaller size. We conclude that digital templating with a calibrating device is a useful part of preoperative planning for total knee arthroplasty.