Malposition of cups and stems in THA leads to a higher rate of dislocation and wear, to leg length discrepancies and to a higher revision rate. Surgical navigation of the implant components should lead to a more accurate position of THA.

1481 consecutive THA were evaluated from November 2001 to June 2006. In a first series until December 2002 127 THA with navigated cups were compared with 110 manually implanted THA. In a second series all following 766 THA with navigated cups were compared to 384 THA with both navigated cup and stem. Navigated surgery was done as a routine procedure by all surgeons, from residents to consultants.

Evaluation was done for radiographs, clinical results, the navigation system data for cup anteversion and inclination, centre of rotation, leg lengthening, offset and antetorsion of the stem, technical exclusions and intra- and postoperative complications as dislocation, seroma, thrombosis and duration of surgery.

The results showed a better alignment in inclination and anteversion of navigated cups compared to non navigated cups and additional improvement when cup and stem were navigated. In stem navigation a good control of the leg lengthening and a reliable prediction of the safe range of motion could be seen. The overall dislocation rate was 0.3% in the navigated groups after December 2002. Thrombosis, seroma and infection were seen in a very low rate in all groups.