Digital templating in primary total hip and knee arthroplasty

The use of digital radiography is becoming more prevalent in orthopedics. This transition impacts the ability to preoperatively plan for implants in total hip arthroplasty (THA) and total knee arthroplasty (TKA). This article reports on the clinical success of digital templating using the Advanced Case Plan (Stryker Imaging, Flower Mound, Texas) system in primary THA and TKA. Digital radiographs of 269 consecutive patients undergoing primary THA (93 cases) or TKA (176 cases) were templated using the Advanced Case Plan digital software package. A 25.4-mm metallic sphere was used as a calibrating marker. Anteroposterior hip and lateral knee radiographs were digitally templated preoperatively and compared to the actual size of the implants at the time of surgery. The accuracy of calibrating images using the metallic sphere was validated by measuring the diameter of femoral heads on 25 postoperative hip radiographs. Digital templating was accurate in predicting the correct implant size in 58.5% of THAs and 66% of TKAs. In 93% of THAs and 98.5% of TKAs, preoperative templating was within 1 size of the final implant. There were no cases in which the predicted implant size varied from the final components by >2 sizes. Calibrating the image using the metallic sphere marker was found to be highly accurate, predicting the correct femoral head size within 1.5 mm in all 25 cases (7 hemiarthroplasties and 18 THAs). Digital templating is an effective means for predicting the size of THA and TKA components, thus remaining a viable option as we transition into the modern era of digital radiography. Future studies will evaluate interobserver reliability and the impact of level of training on templating accuracy.