[Bone segment transport of the femur. Biomechanical value of an unreamed titanium intramedullary nail with reference to stiffness of external distraction systems].

The influence of an unreamed femur nail on axial and torque stiffness of nine different external fixator devices was investigated in a biomechanical study. With a newly developed femur bone model simulating segmental transport, 582 biomechanical tests were performed. The additional use of an unreamed femur nail (UFN) increased axial stiffness of the external fixator devices up to 8108% (average 1673.8-2631.8%) and increased torque stiffness up to 86% (average 47%). The best results could be achieved when combining a small-diameter UFN (9 x 360 mm, Synthes Co.) and external fixator devices with high torque and comparatively little axial stiffness. The use of stainless steel half-pins instead of titanium half-pins improved torque stiffness significantly. Concerning the biomechanical demands made on external fixator devices used for femoral segmental transport, the Hexfix fixator with steel bar and steel half-pins combined with an UFN achieved the best results.