Introduction: Pre-operative templating helps the operating surgeon to accurately choose optimal implant size. In the past analog images have been templated with the help of acetate templates. With the introduction of Picture Archive and Communications Systems (PACS) digital software is now available. We would like to present preliminary results of an ongoing prospective study investigating the accuracy of digital templating compared to actual implant size in primary hip arthroplasty.

Methodology: The senior author pre-operatively templated implant size using the TraumaCad (Orthocrat limited, Israel). Images were saved and displayed using the web based PACS system RADIN (RADIN 3.2, SoHard AG, Germany). All patients undergoing primary hip replacement surgery were included in the study. Patients with significant collpase of the acetabulum or femoral head needing additional reconstruction were excluded. Hips were templated using radiographs calibrated against a spherical metal ball. For each hip, an AP pelvis view was used. Acetabular implants used were either Trident PSL or Exeter contemporary cup (Stryker). Femoral stem was Exeter (Stryker). Predicted implant sizes were documented. Operation was performed by the senior author or under his supervision using the posterior approach. Postoperatively, the predicted implant size was compared to the implanted components.

Results: 18 consecutive primary total hip arthroplasties were templated. The differences between digital and actual sizes were plotted against their mean in Bland- Altman plot. The 95% confidence interval of the differences between digital and actual sizes were ± 4mm (±2 sizes) for acetabluar cup, ±1 mm (± ½ size) for femoral stem and ± 6mm (±1 size) for offset. All postoperative films showed good fit of components and there were no intraoperative or postoperative fractures.

Discussion: Our data indicate that digital templating is reliable in predicting actual implant sizes for total hip arthroplasty. We hope to present a larger series in the meeting.