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Open Access Research article

Comparison of transverse wires and half pins in Taylor Spatial Frame: A biomechanical study

Ashish Khurana1*, Carlton Byrne2, Sam Evans2, Hiro Tanaka3 and Kartik Haraharan3

Author Affiliations

1 Department of Trauma & Orthopaedics, University Hospital of Wales, Heath Park, Cardiff, UK

2 School of Engineering, Cardiff University, Cardiff, UK

3 Department of Trauma & Orthopaedics, Royal Gwent Hospital, Newport, UK

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Journal of Orthopaedic Surgery and Research 2010, 5:23  doi:10.1186/1749-799X-5-23

Published: 27 March 2010

Abstract

Background

The aim of this study was to compare the stiffness characteristics of Taylor Spatial Frame (TSF) fixed with transverse wires and half pins.

Design & Methods

Experiments were carried out at the biomechanics laboratory at Cardiff University. All mechanical testing was performed with a servo hydraulic test frame (MTS 858 Mini Bionix II(R), MTS Corp., Mineapolis, USA). Custom built mounts were used to attach the bone rigidly to the one end of machine and the TSF ring to the other. Rings were fixed with 1.8 mm transverse wires or hydroxy-apatite coated 6.5 mm half pins in 45degrees, 60degrees, 75degrees and 90degrees divergence angles. Bone was loaded with axial load to 400 N and torque to 20 Nm in an indestructible manner. Load/displacement curve data were analyzed for slope and axial and angular displacements.

Results

For larger diameter rings (180 mm), for axial stiffness there was no statistically significant difference between the transverse wires (4 wires with 2 rings) and the half pins (2 pins with 1 ring) (p > 0.05). For 155 mm internal diameter rings, half pins provided statistically higher axial stiffness than transverse wires (p = 0.036). The half pins show significantly more torsion stiffness in both ring diameters (p < 0.05) in comparison to transverse wires. As in axial stiffness, small diameter rings show increased stiffness in torsion. There is increase in axial and torsion stiffness with the increase in the divergence angle between the wires or pins (p < 0.05).

Conclusion & Clinical Relevance

Half pins provide greater stiffness to TSF frames and allow for axial micro motion as well. This work provides a rationale for clinical decision making about the use of tensioned transverse wires in comparison to half pins in construction of a TSF frame