The 3-dot circle: A reliable method for safe and efficient digital templating of the acetabular component.

Background: Templating for preoperative planning of joint arthroplasty has followed the evolution of digital templating software.

Objective: This study aims to provide a safe, reliable and reproducible method for prediction of acetabular component size based on measurement of the radiographic femoral head diameter, with the aid of templating software.

Methods: A defined methodology for femoral head measurement was applied to 97 consecutive, calibrated digital pelvic radiographs. Based on radiographic femoral head diameter, the minimum acetabular shell diameter was calculated and then compared to the size of the implanted acetabular shells.

Results: This method predicted safe minimum acetabular component size with an accuracy of 95.9% with a high inter-observer reliability of 97.6%.

Conclusions: This study presents a simple, reproducible and accurate method for templating of the minimum safest acetabular component diameter.