title: The effect of transfixion wire crossing angle on the stiffness of fine wire external fixation: a biomechanical study.
abstract: To analyse the effect of transfixion wire-crossing angle on the stiffness of fine wire external fixation, a laboratory investigation using a fibreglass tibia fixed into an idealised fixator was performed with a servohydraulic test frame. Load-deformation behaviour was compared at the different wire-crossing angles (30 degrees -90 degrees ) under identical conditions of central axial compression, medial compression-bending, posterior compression-bending, posteromedial compression-bending, and torsion. Stiffness values were calculated from the load-deformation and torque-angle curves. The increase in wire-crossing angle led to an overall increase in the stiffness, except medial bending stiffness. The wire-crossing angle of 90 degrees provided significantly greater stiffness than all other angles in all load configurations (p<0.05) except medial bending. In medial bending, the wire-crossing angle of 30 degrees provided significantly greater stiffness than all the other angles (p<0.05). Increasing wire-crossing angle from 30 degrees to 90 degrees contributed to an overall increase of 75% in external fixation stiffness, which included axial, torsional, and bending stiffness, but bending stiffness was a function of the wire positioning with respect to the loading axis. Therefore, using the widest possible wire-crossing angle and placing wires as close to the loading plane as possible can increase the stiffness of external fixation.
authors.affiliation: Department of Orthopaedic Surgery, University of Louisville School of Medicine, 210 East Gray Street, Suite 1003, Louisville, KY 40202, USA. craig.roberts@louisville.edu
authors.forename: Craig S
authors.initials: CS
authors.lastname: Roberts
authors.forename: Valentin
authors.initials: V
authors.lastname: Antoci
authors.forename: Valentin
authors.initials: V
authors.lastname: Antoci
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Voor
mesh_terms: D001696:Biomechanical Phenomena; D001864:Bone Wires; D005592:Fracture Fixation / Q000295:instrumentation / Q000379:methods*; D006801:Humans; D013314:Stress, Mechanical; D013978:Tibial Fractures / Q000601:surgery*