A Biomechanical Evaluation of Three Drop Wire Configurations

Authors

  • Johnattan Arango DVM,

    1. Comparative Orthopaedics and Biomechanics Laboratory, University of Florida, Gainesville, Florida
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  • Daniel D. Lewis DVM, Diplomate ACVS,

    Corresponding author
    1. Department of Small Animal Clinical Sciences, College of Veterinary Medicine, University of Florida, Gainesville, Florida
    • Comparative Orthopaedics and Biomechanics Laboratory, University of Florida, Gainesville, Florida
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  • Caleb C. Hudson DVM, MS, Diplomate ACVS,

    1. Comparative Orthopaedics and Biomechanics Laboratory, University of Florida, Gainesville, Florida
    2. Department of Small Animal Clinical Sciences, College of Veterinary Medicine, University of Florida, Gainesville, Florida
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  • MaryBeth Horodyski EdD, ATC

    1. Comparative Orthopaedics and Biomechanics Laboratory, University of Florida, Gainesville, Florida
    2. Department of Orthopaedics and Rehabilitation, College of Medicine, University of Florida, Gainesville, Florida
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  • Funded in part by a grant from the Morris Animal Foundation, Veterinary Student Scholars program. Some materials were provided by IMEX™ Veterinary, Inc., Longview, TX.

Corresponding Author

Daniel D. Lewis, DVM, Diplomate ACVS, 2015 SW 16th Avenue, Gainesville, FL 32610

E-mail: lewisda@ufl.edu

Abstract

Objective

Evaluate effect of adding drop wires to single-ring constructs.

Study Design

Biomechanical study

Sample Population

Single ring circular external skeletal fixator constructs stabilizing a Delrin segment bone model.

Methods

Eight replicates of 5 constructs made with 66 mm complete rings, 1.6 mm olive wires, and a 15.9-mm diameter Delrin rod were loaded in axial compression, craniocaudal and mediolateral bending, and torsion. Constructs tested were: (1) base single-ring construct; (2) single-ring construct with a drop wire mounted on fixation bolts; (3) single-ring construct with a drop wire mounted on 1-hole posts; (4) single-ring construct with a drop wire mounted on 2-hole posts; and (5) 2-ring construct. Construct stiffness for each mode of loading was compared using repeated measures ANOVAs (P ≤ .05).

Results

Axial compression and torsion: the 2-ring construct was stiffer than all others. Drop wire constructs were stiffer than the single-ring construct, but not significantly different from each other. Craniocaudal bending: the 2-ring construct was stiffest with the 2-hole post construct being stiffer than all except the 2-ring construct. Mediolateral bending: the 2-hole post construct was stiffer than the 2-ring construct, which was stiffer than the 1-hole post construct, which was stiffer than the fixation-bolt construct, which was stiffer than the single-ring construct.

Conclusions

Drop wires improved stiffness of single-ring constructs in all loading modalities. Positioning the drop wire farther from the ring surface significantly improved craniocaudal and mediolateral bending stiffness, but did not affect axial compression and torsional stiffness.

Ancillary