Computer-assisted fluoroscopy-based reduction of femoral fractures and antetorsion correction

Intra-operative fluoroscopy is a valuable tool for visualizing underlying bone, implant, and surgical tool positions in orthopedics. It has brought about the minimally invasive surgical technique of intramedullar nailing to fix femoral shaft fractures. However, the limited field of view and two-dimensional property of fluoroscopic images aggravate intra-operative control of surgical parameters. The purpose of this article is to introduce a surgical navigation system based on fluoroscopy that provides missing information for the procedure of femoral fracture fixation.

Optoelectronic markers are placed on a surgical drill, involved bone fragments, the femoral nail, and the fluoroscope to track their positions. Projection properties of the fluoroscope are acquired through an initial precalibration. The relative positions of bone fragments, implants, and surgical tools are displayed superimposed simultaneously and in real time on multi-planar intra-operative fluoroscopic images. This is achieved by computer simulation of X-ray projections that have taken place with acquisition of the fluoroscopic images. In addition, a method has been developed that allows contactless measurement of three-dimensional anatomic landmarks, based on their representation in fluoroscopic images. In combination with optoelectronic tracking, this enables dynamic calculation of important surgical parameters such as femoral antetorsion.

A pilot surgery showed that fracture reduction can benefit from the developed computer-assisted method. An in-vitro study on computer-assisted measurement of femoral antetorsion demonstrated the high degree of precision of this technique.