[Intraoperative navigation for hip resurfacing. Methods and first results].

Hip resurfacing received a renewed boost through the introduction of the BHR (Birmingham hip resurfacing) system. One can assume that with the BHR system major disadvantages of previous resurfacing systems have been overcome. Among the most remarkable improvements are the metal on metal bearing as well as the equipment for the exact positioning of the femoral component through guided drilling, reaming and an insertion of the implant. The purpose of the presented study was to find out whether by using a fluoroscopic navigation system the preparation of the femoral head and the positioning of the femoral component can be made easier and more precise. We developed a standardised procedure, which comprised the preoperative planning as well as the intraoperative application of the navigation system up to the drilling of the central rod, through which all of the reaming tools are guided and, finally, the component is also fitted. In 31 cases, the procedure showed excellent performance and reliability.A very exact, preferably steep (valgus) implantation of the femoral component was achieved without erosion of the femoral neck cortex ("femoral notching"). The difference between the intraoperative angles of the component's position indicated by the navigation system and the postoperative results on x-rays averaged 2.6 degrees (0.89 degrees SD), which is close to the actual limits of accuracy for fluoroscopic systems. The realisation of the project was achieved with standard hardware (navigated drill guide) and navigation system software. The virtual positioning of the implant in the optimal position impressed as an important comfort gain. The additional operating time was 10-15 min in the last ten cases.