Background: During the past decade, there has been a resurgence of interest in hip resurfacing as a mode of treatment for the younger patient with hip disease since major disadvantages of previous resurfacing systems have been overcome. The purpose of the presented study was to clarify if an imageless navigation system will allow precise placement of the femoral component.

Methods: Between September 2004 and May 2006, 50 metal-on-metal surface arthroplasties each were performed either using an imageless navigation system or the conventional technique. The inclination and the axial alignment of the femoral component were determined by two independend examiners and compared to the values presented by the navigation system.

Results: In the preoperative x-rays a mean CCD-Angle of 129.2 degrees (Control group: 127.5°) was measured. The mean femoral shaft angle was 137.5 degrees (Control group 133°) postoperatively with a mean deviation of 2.1 degrees compared to the values shown by the system. In the computer assisted group the mean deviation from the ideal placement in the axial plane was 2.9 degrees compared to 4.8° when using the conventional technique.

Conclusion: The use of a navigation system was associated with only an average time loss of 7 minutes for surface data acquisition und mounting of the reference base. The computer assisted technique appears to be helpful to avoid notching during the femoral bone preparation and improve implant positioning which might improve durability.