Tensioning technique and fixator stability of a circular external fixator with threaded fine wires

Hybrid external fixators have become more popular over recent years, and although biomechanical tests show varying results from paper to paper, a consistent finding is shear motion occurring at the fracture/osteotomy site during loading. This can be reduced to some extent by frame configuration, and with the use of olive stop wires, but both of these have limitations. We have investigated the use of threaded fine wires in a circular hybrid fixator. A reliable tensioning method is described which minimises movement at the wire–bone interface during tensioning, and threaded wires are seen to offer a significant improvement in fracture site shear stiffness when compared to smooth fine wires.