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 that of a standard pin. The pins were inserted into pilot holes previously drilled into a piece of teak hardwood. Loads of different magnitudes were applied at a fixed moment arm and force-deflection curves were obtained. Thereafter, percentage stiffness increase was calculated for each pilot hole size. The results show that the addition of a collar to 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 using finite element analysis techniques. The results show that the flange significantly reduced the stresses generated at the pin-bone interface. In addition, stresses were dissipated over a wider area.
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Department of Orthopaedic Surgery, Glenfield General Hospital, Leicester, England.
Capper
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Soutis
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D001696:Biomechanical Phenomena; D001858:Bone Nails; D016267:External Fixators; D008962:Models, Theoretical; D013314:Stress, Mechanical