Acetabular center axis: is it the future of hip navigation?

There are 2 distinct methods of cup navigation in total hip arthroplasty. One predicts orientation of the acetabulum through bony landmarks outside the acetabulum (eg, the anterior pelvic plane); its unreliability is well published. The other identifies acetabular center axis (ACA) and is patient-specific method that is independent of pelvic tilt, making it more reliable. Data from readily palpable acetabular registration points were compared with postoperative pelvic computed tomography images in 137 cases. Findings show that ACA software is accurate in determining acetabular/cup version and inclination. Cup center axis should coincide within 4 mm of ACA to minimize impingement and maximize stability without altering preoperative femoral version.