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Effects of Transfixation Pin Positioning on the Biomechanical Properties of Acrylic External Skeletal Fixators in a Fracture Gap ModelFunding The study has been funded by the Fonds du Centenaire and the Fonds en santé des animaux de compagnie of the Faculty of Veterinary Medicine of the University of Montreal, supported by Zoetis.
Objective The aim of this study was to evaluate the biomechanical effects of transfixation pin positioning in acrylic columns of external skeletal fixators (ESF).
Study Design Twenty-four type I acrylic ESF were built simulating a fracture gap-model. Transfixation pins were placed centric (n = 12) or eccentric at ¼ of the column diameter (n = 12) in the acrylic columns. Six constructs from each group were subjected to axial compression and four-point bending tests. Stiffness, yield load and mode of failure were recorded.
Results Stiffness was not influenced by centring (p = 0.373), but it was higher in four-point bending than in axial compression (p < 0.001). Pin positioning had no influence on the yield (p = 0.535) and failure loads (p = 0.715) in axial compression, nor on the yield load in bending (p = 0.135). Eccentric pin positioning decreased failure loads by 28% in bending (p < 0.001).
Conclusion Eccentric position of transfixation pins within the acrylic columns alters the biomechanical properties of type I ESF constructs. While acrylic offers several advantages, when forming the columns, frame strength will be optimized if pins are centrally located.
This work was submitted in abstract form and accepted for oral presentation in the Resident's Forum at the American College of Veterinary Surgeons (ACVS) Surgery Summit, Portland, United States, October 2022.
All authors conceptualized and designed the study. J.L. and D.G. acquired the data. All authors did data analysis and interpretation of the results, as well as drafted, revised and approved the submitted manuscript and are publicly responsible for the relevant content.
Received: 12 August 2022
Accepted: 22 April 2023
Article published online:
19 June 2023
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