Abstract
Purpose
External fixators are easy to apply and maximize soft tissue preservation. However, frames need providing an adequate stiffness in order to avoid excessive interfragmentary movement during the healing period. We characterized the stiffness of four different configurations of the newly developed Hoffmann 3 external fixation system.
Methods
A synthetic fracture gap model was stabilized using four different frame configurations: a double-∅ 11 mm rod configuration (group DR), a hybrid double-∅ 8 mm rod configuration (group H), a single ∅ 11 mm rod direct link configuration (group DL) and a single ∅ 11 mm rod side arm configuration (group SA). The stiffness of each configuration was measured under anterior-posterior bending, medial–lateral bending and axial torsion loading directions and the results statistically compared.
Results
The basic frame construct (group DR) showed the highest bending and torsional stiffness properties while the single rod side arm configuration (group SA) the lowest.
Conclusions
The diameter and the amount of used connecting rods as well as the adequate placement of these rods towards the main loading directions determine the construct stiffness. These results could help the surgeons estimating how different frames can potentially affect the interfragmentary motion. This information might help in choosing specific configuration when treating different fracture types on given patients.
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Acknowledgement
We thank Mr. Marcus Stoffel, PhD, of the Institute of General Mechanics of the RWTH Aachen University for his thorough supervision of the mechanical tests. We would like to thank Robert Leo Garrison, MD for the translational work and clinical advisory.
Conflict of interest
Stryker Osteosynthesis Kiel, Germany, sponsored this study. The tests were accompanied and supported by Mr. Markus Behrens, biomechanical engineer, Stryker Osteosynthesis, Switzerland. There was no influence by the sponsor on the submitted manuscript. The role of the sponsor was purely to advise in terms of handling of the fixator system components. There are no further conflicts of interest.
Ethical standards
The manuscript does not contain clinical studies or patient data. No human or animal specimens were used. All authors certify that they comply with the ethical guidelines for authorship and publishing in the European Journal of Trauma and Emergency Surgery.
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Sellei, R.M., Kobbe, P., Dienstknecht, T. et al. Biomechanical properties of different external fixator frame configurations. Eur J Trauma Emerg Surg 41, 313–318 (2015). https://doi.org/10.1007/s00068-014-0436-1
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DOI: https://doi.org/10.1007/s00068-014-0436-1