Vergleichende biomechanische in vitro Untersuchung zur extramedullären vs. intramedullären Stabilisierung am Modell der instabilen medialen Schenkelhalsfraktur.

Abstract

Background: The objective of this study was to investigate primary stability of the proximal femoral nailing antirotation for the indication of unstable medial femoral neck fractures. The device was compared to the dynamic hip screw blade, which is a "gold standard" in the treatment of proximal femoral fractures. Methods: Six pairs of human cadaver femurs were tested in a cyclic loading model with loads up to 200 N, 400 N, 600 N, 800 N, and 1000 N, respectively. Iliotibial tract was simulated by a chain that applied forces on the greater trochanter during loading. In vitro combined axial and bending loads were applied. Angular displacements during loading were recorded in all directions, and loads to failure were recorded. Findings: For the cyclic loading test no statistically significant differences between the two groups could be detected. Specimens fixed with the dynamic hip screw blade showed higher displacements in varus direction at 400 N and 600 N, in external rotation at 200 N, 400 N and 600 N, and in anterior direction at 400 N. Load to failure revealed no statistical difference between the two implants. Interpretation: The proximal femoral nailing antirotation achieves primary stability comparable to the dynamic hip screw blade. The proximal femoral nailing antirotation combines the biomechanical favourable concept of intramedullary fixation with a minimally-invasive surgical technique, which theoretically may be advantageous in clinical use. Further biomechanical studies are required to clarify to what extent the results of the present study can be transferred to the clinical situation.