Evaluation of a new fluoroscopy-based navigation system in the placement of the femoral component in hip resurfacing.

Prosthesis-specific mechanical alignment instruments for the precise and reproducible positioning of the femoral component constitute one of the major improvements in modern hip resurfacing prostheses. However, mechanical failure of the femoral component is mostly attributable to the surgical technique, and in particular to notching of the femoral neck. In order to evaluate a novel computer-assisted fluoroscopy-based planning and navigation system, six DUROM hip resurfacing prostheses were implanted into artificial femurs by means of computer-assisted fluoroscopy-based navigation and prosthesis-specific mechanical alignment instruments. Subsequently, the planning and navigation system was tested within the scope of a cadaver study on three fixed whole-body preparations (six femurs). The average difference between planned and actual angle of the prosthesis was 0 +/- 0.7 degrees for fluoroscopy-based navigation versus 6.5 +/- 7.8 degrees for the in-vitro use of the prosthesis-specific mechanical alignment instruments, and 1 +/- 1.4 degrees for fluoroscopic navigation in the cadaver study. The average discrepancy between planned and actual anterior offset was -1.2 +/- 1.2 mm versus 0.8 +/- 4 mm, and 0.3 +/- 2.2 mm in the cadaver study, and the time required for the total of five planning and navigation steps was 17.2 +/- 1.5 min versus 14 +/- 0.8 min and 20.2 +/- 2.5 min respectively. No notching of the femoral neck occurred under fluoroscopy nor under conventional treatment. During in-vitro studies, use of the computer-assisted fluoroscopy-based planning and navigation system resulted in enhanced accuracy compared with conventional prosthesis-specific mechanical alignment instruments. The system has yielded initial promising results within the scope of the cadaver study.