BENDING STIFFNESS OF CONICAL AND STANDARD EXTERNAL FIXATOR PINS

The bending stiffnesses of a conical and a standard external fixator p in have been compared. The pins were inserted into pilot holes in a pi ece of teak hardwood and loads of different magnitudes were applied at a fixed moment arm. Force-deflection curves were obtained for each pi n, and stiffness (newtons per metre) and percentage stiffness reductio n were calculated for each pilot hole size. The results show that defl ection increased (i.e. stiffness decreased) with increasing force or d iameter of pilot hole. This loss of stiffness was linear for the stand ard pin but was bimodal for the conical pin.