Introduction: Navigation is expected to be a useful procedure in hip resurfacing, as it helps to determine several important features such as component orientation, avoiding femoral notching, sizing and positioning.

Methods: In this study, an imageless navigation system dedicated to the Birmingham hip resurfacing prosthesis was evaluated for clinical use. With this system, the bone model is generated by registration of surface landmarks and image morphing. The computer then proposes size and position of the implant, which can be fine – tuned by the surgeon. The final position is then transferred on to the bone by navigating the guiding pin.

Results: In 40 cases the femoral component of the Birmingham hip resurfacing was implanted using the navigation system. The generated models were acceptable in all but two cases with an average accuracy of 2.1 mm (head superior) to 1.4 mm (neck superior). The difference between the neck-shaft angle calculated intraoperatively by the system and the postoperative value on x-ray on average was 2.8 degrees. The post-operative neck-shaft angle was seven deg. steeper than the pre-op CCD – angle, indicating a marked valgus position of the components which is expected to be a favorable condition. Femoral notching was not seen in any case.

Conclusion: The image free navigation proved to be a helpful and promising tool for an optimal surgery in hip resurfacing. It can replace mechanical device and is more accurate and versatile. The quality of the generated bone models should be improved. Navigation of the socket is also possible. Our results on socket are still being analysed.