First clinical and biomechanical results of the Trochanteric Fixation Nail (TFN).

Conventional osteosynthesis of proximal femur fractures is still affected by serious complication rates between 4-18%, even though advanced implant modifications and surgical techniques are common practice. In terms of increasing age and co-morbidity of patients this complication ratio is expected to increase even further in the immediate future. One major reason for implant failure is the decreasing stability potential of the implant due to a loss in mechanical properties of cancellous bone. Therefore, efforts in new intramedulary techniques specifically focus on the load bearing characteristics of the implant by developing new geometries to improve the implant-tissue interface. This investigation discusses first clinical results of the trochanteric fixation nail TFN (145 patients) and a biomechanical analysis of the blade/femur head interaction under different static loading conditions. The TFN shows promising performance in first clinical results. In the clinical study the overall complication rate was significantly lower compared to other similar osteosynthesis. For the investigation of the biomechanical stability of the helical TFN blade the following experiments were performed: Analysis of the axial load required for insertion of the blade by free rotation; measurement of the corresponding rotation angle for total insertion (32 mm) (n = 8); pull-out forces with suppressed rotation (n = 4); loads for rotational overwinding of the implant in the fully inserted condition (n = 4). All investigations were performed on human femoral heads. The bone mineral densities of the specimens were detected by QCT-scans. Prior to cadaveric testing the experimental set-up was validated (n = 8) by the use of synthetic foam blocks (Sawbone).