Technique for intraoperative determination of femoral rotation with a lateral femur nail (LFN, Synthes, Oberdorf, Switzerland)

Endomedullary femur nails with a head–neck implant offer an up to now unused point of reference for the determination of rotation during osteosynthesis. The lateral femur nail (LFN) or the long Proximal Femur Nail (long PFNA), for example, have recon screws or a blade placed at a 10° angle to the distal locking screw in the transversal plane. If the head–neck implant is inserted properly, the rotation of the femur can be measured with the C-arm taking the hole of the distal locking screw and the posterior condylar tangential line as reference lines. If the posterior condylar tangential line is parallel to the axes of the hole of the distal locking screw, then the rotation or anteversion of the femur is equal to the angle between the head–neck implant and the distal locking screw which is 10° with LFN or long PFNA. Differing rotation angles can be made visible by rotating the C-arm from the axial projection of the distal locking screw up to the posterior condylar tangential line. Three exemplary cases are presented. The recommended method was effective. The rotation of the femur can be measured intraoperatively with this technique and many revisions can be avoided.