Navigated Ultrasound in Total Hip Arthroplasty

In total hip arthroplasty, an optimal cup orientation is essential to avoid dislocations. Computer assisted systems provide the surgeon with the intra-operative cup orientation. However, these systems rely on the palpation of the anterior pelvic plane, and are thereby prone to the palpation error of this plane. As this error is directly linked to the soft tissue overlying the pelvic landmarks, we developed a navigated ultrasound system to acquire the anterior pelvic plane. 5 operators acquired 5 times the anterior pelvic plane of 2 female cadavers. After a learning curve, the acquisition of the plane took approximately 90 seconds. Compared to the anterior pelvic plane measured on the CT-scan, the mean rotation error was less than 0.5°, with a standard deviation of less than 1.2°. The mean version error was -1.2°, and the standard deviation remained below 1.9°. Our results confirm that navigated ultrasound is a very accurate tool to acquire the anterior pelvic plane and thereby allow an accurate navigation of total hip arthroplasty.