With the advent of digital radiology, our institution has introduced digital templating for preoperative planning of total hip arthroplasty (THA). Prior studies of the accuracy of digital templating had contradictory results. This study compares the accuracy of digital and analog templating for THA. Ninety patients were recruited. Sixty-eight patients had analog pre-operative templating while 22 patients had digital templating. A retrospective review of medical records obtained the sizes of hip implants inserted during THA and patient demographics. The templated hip sizes were compared with the actual hip implants inserted. Accuracies of both templating methods were compared in four outcomes: prediction of acetabular cup size, prediction of femoral stem size, prediction of femoral offset and prediction of femoral neck length.

Digital templating was more accurate than analog templating in predicting acetabular cup size, femoral stem size and femoral offset. Analog templating was more accurate in predicting femoral neck length. However, only the comparison of femoral offset achieved statistical significance (p-value = 0.049).

After stratifying the data by BMI, digital templating was more accurate than analog templating in predicting acetabular cup and femoral stem sizes for patients with high BMI. For patients with BMI = 25-30, accuracy of digital templating was 100.0% for cup and 80.0% for stem while accuracy of analog templating was 74.1% for cup and 74.1% for stem. For patients with BMI > 30, accuracy of digital templating was 84.6% for cup and 69.2% for stem while that of analog templating was 75.0% for cup and 66.7% for stem.

Digital templating outperformed analog templating in all the outcomes except femoral neck length. In addition, digital templating was significantly more accurate in predicting femoral offset. This study showed that digital templating has the potential to reduce errors in pre-operative planning for THA.