Abstract
An investigation was conducted to determine what improvements in the resistance to slippage could be obtained in selected interfaces (rod/clip torsional, cheek/bowl and cheek/clip) of the Hoffmann external fixator. The modification involved changing the standard wing-nut clamp for a bolt with a thread of 7 mm and a 1 mm pitch and placing an FAG 28–303 thrust-bearing (needle roller and cage assembly) between the bolt and the cheek. The results showed a significant improvement in the slippage values of all interfaces; increases of approximately six times were obtained at all torque values of the wing-nut clamp or fastener tested. Such improvements would markedly increase the reliability of external fixation systems and thus reduce the incidence of loss-of-reduction of fracture due to slippage of the universal joint.
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Drijber, F.L.I.P., Finlay, J.B., Moroz, T.K. et al. Source of the slippage in the universal joints of the Hoffmann external fixator. Med. Biol. Eng. Comput. 28, 8–14 (1990). https://doi.org/10.1007/BF02441671
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DOI: https://doi.org/10.1007/BF02441671