Ultrasound vs pointer palpation based method in THA navigation: a comparative study.

Intraoperative registration of the anterior pelvic plane is necessary for navigation during total hip arthroplasty (THA). Ultrasound referencing of bony landmarks was implemented in a THA navigation system (OrthoPilot, B. Braun Aesculap; Tuttlingen, Germany) as an alternative to pointer palpation. This study compared the accuracy of manual pointer palpation with ultrasound registration for determining anterior pelvic plane registration in a consecutive series of 37 cases. Findings showed postoperative radiographic anteversion was lower than ultrasound and pointer navigated anteversion. Because ultrasound registers the bony landmarks of the anterior pelvic plane with a high degree of accuracy, we conclude radiographs 2 weeks post-operatively are not suited to evaluate anteversion, because they still display a pelvic tilt due to a pre-operative flexion contraction.