AN INVESTIGATION OF THE BENDING STIFFNESS OF AND THE PLANE STRESSES GENERATED BY A FLANGED EXTERNAL FIXATOR PIN

In an attempt to reduce pin loosening, a flanged external fixator pin has been designed and its bending stiffness has been compared with tha t of a standard pin. The pins were inserted into pilot holes previousl y drilled into a piece of teak hardwood. Loads of different magnitudes were applied at a fixed moment arm and force-deflection curves were o btained. Thereafter, percentage stiffness increase was calculated for each pilot hole size. The results show that the addition of a collar t o the external fixator pin increases its stiffness and its ability to resist bending forces. In a parallel study, the stresses generated at the pin-bone interface by this pin and a standard pin were compared us ing finite element analysis techniques. The results show that the flan ge significantly reduced the stresses generated at the pin-bone interf ace. In addition, stresses were dissipated over a wider area.