Hexapod orthogonal periarticular slack-wire stabilization technique: Surgical tip for accurate orthogonal metaphyseal frame mounting

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Introduction: The use of hexapod circular external fixators in the treatment of various orthopedic conditions has become more common in recent years. One of the principle mounting requirements is that the fixator is orthogonally aligned to the mechanical axis of the limb. This creates the optimal mechanical environment for bone formation as any forces exerted on the fixator are transmitted as axial forces to the limb while eliminating unwanted motions such as rotation and shear. We describe a method to reliably obtain orthogonal mounting of periarticular rings during hexapod circular external fixator application. The technique is fast, accurate, and uses components readily available on all hexapod external fixator systems. Methods: The “hexapod orthogonal periarticular slack-wire stabilization (HOPSS) technique” uses a untensioned/slack wire as the second fixation element following the transverse reference wire. A wire fixation bolt is attached to the ring, and a second wire (slack wire) is placed through the wire fixation bolt to allow insertion in an antero–posterior direction. The wire is advanced through the near cortex and onto the far cortex after which the wire fixation bolt can be tightened and a final image intensifier check can be done. The technique can be used for the application rings to the metaphysis of long bones. Discussion: Orthogonal mounting for Ilizarov all-wire frames has been a crucial part of the surgical technique and has long been accepted as it promotes axial micromotion that supports callus formation and union and eliminated parasitic motion at the bone ends. The described technique uses readily available instruments and components to assist with perfect orthogonal mounting. Conclusions: The hexapod orthogonal periarticular slack-wire technique is a simple method for obtaining more accurate orthogonal mounting. It is quick and effective and does not require any additional equipment.