A new method for external fixation with single crystal alumina ceramic screw nail and its biomechanical study

Through the use of the Hoffmann external fixator, we have recognized the importance of strength of fixation between the screw nail and the bone in the external fixation and have fully realized the necessity of an affinity of the screw nail to the soft tissue at the thrusting site of the screw nail. We made a screw nail for external fixation with single crystal alumina ceramic on an experimental basis and after its basic test of strength, tried its clinical application by the Hoffmann external fixator. When this screw nail was used, it was found difficult to fix the screw nails thrusted in each different direction by the Hoffmann external fixator because of the small elasticity of the sapphire screw nail itself. However when the screw nails were fixed by force, a great stress concentration occurred in them or the bone around them and this caused their breakage and loosening. To protect this, we have developed a new external fixator which enables to hold, connect and fix each screw nail at the individual thrusting positions and directions and is therefore completely universal to each plane.