Intraoperative landmarks are used in image-free navigation systems. The ultrasound-based navigation systems try to overcome the problems of positional deviation associated with soft tissue. Our study analyzed the accuracy of ultrasound-based navigation of cup positioning compared with postoperative 3-dimensional (3D) computed tomography scans of cup positioning. Twenty-five ultrasound-navigated total hip arthroplasties (THAs) were analyzed. The difference between the intraoperative cup orientation (navigation) and the postoperative cup position (CT) was evaluated. The average difference between intraoperative navigation and postoperative CT measurements was 2.8 degrees (SD+/-1.8 degrees ) for abduction and 2.2 degrees (SD+/-1.6 degrees ) for anteversion. Therefore, we recommend ultrasound-based navigation as an exact tool for cup positioning in THA.
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