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Veterinary surgery : VS2025; 54(3); 610-620; doi: 10.1111/vsu.14226

Ex vivo biomechanical comparison of pedicle screw and rod constructs with and without interbody fusion devices for equine cervical vertebral stabilization.

Abstract: To determine the biomechanical properties of pedicle screw and rod (PSR) constructs alone and with an interbody fusion device (PSRIFD) for equine ventral cervical vertebral stabilization. Methods: Cadaveric ex vivo biomechanical analysis. Methods: A total of 14 (n = 14) adult equine cervical vertebral columns. Methods: Cervical vertebral columns were stabilized by PSR alone (n = 6) or PSRIFD (n = 5). Three columns were left unaltered as controls. Non-destructive biomechanical testing showed the kinematic range of motion (ROM), compliance, and neutral zone of each spinal unit in the three main kinematic directions (flexion-extension, lateral bending and axial rotation). Destructive testing was performed to identify mode of failure and stiffness in flexion. Non-destructive and destructive biomechanical data were compared by ANOVA between experimental groups. Results: In flexion-extension, PSR and PSRIFD had significantly lower ROM, compliance and neutral zone than controls (all p < .05). ROM, compliance and neutral zone were not different between PSR and PSRIFD groups. In axial rotation, the neutral zone of PSR was lower than PSRIFD (p = .013) and both were lower than controls (p < .0001 and p < .02, respectively). Stiffness and moment failure between PSR and PSRIFD groups were not different. All constructs failed through articular process joint dislocation, though the PSRIFD group also had ventral IFD migration. Conclusions: PSR and PSRIFD groups have similar biomechanical properties and modes of failure, though PSRIFD had higher catastrophic injury potential. Conclusions: These findings support that PSR constructs provide comparable biomechanical stability to PSRIFD, reducing time and potential complications associated with IFD placement.
© 2025 American College of Veterinary Surgeons.
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Publication Date: 2025-02-14 PubMed ID: 39953786DOI: 10.1111/vsu.14226Google Scholar: Lookup
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  • Journal Article
  • Comparative Study

Summary

This research summary has been generated with artificial intelligence and may contain errors and omissions. Refer to the original study to confirm details provided. Submit correction.

Overview

  • This research article examines the biomechanical stability of two cervical vertebral stabilization methods in horses: pedicle screw and rod (PSR) constructs alone versus PSR combined with interbody fusion devices (PSRIFD).
  • The goal was to compare their mechanical properties and failure modes to determine if adding the interbody fusion device provides additional stabilization benefits.

Introduction and Purpose

  • Cervical vertebral instability in horses can require surgical stabilization to restore function and reduce pain.
  • Two common methods for stabilization are:
    • Pedicle screw and rod (PSR) constructs, which fix spinal segments externally with screws and rods.
    • PSR combined with an interbody fusion device (PSRIFD), which also involves placing a fusion device between vertebral bodies to promote bone fusion and stability.
  • The study aimed to biomechanically compare these two techniques in equine cervical spines to evaluate differences in stability and failure patterns.

Methods

  • Used 14 adult equine cervical vertebral columns obtained post-mortem for ex vivo biomechanical testing.
  • Three groups were tested:
    • PSR alone (n=6): stabilization by pedicle screw and rod constructs.
    • PSRIFD (n=5): stabilization by PSR plus ventral interbody fusion device.
    • Controls (n=3): no stabilization applied, natural spine for baseline comparison.
  • Biomechanical tests were of two types:
    • Non-destructive testing: measured kinematic parameters including range of motion (ROM), compliance (ease of movement under load), and neutral zone (amount of movement before resistance is encountered) in three movement directions—flexion-extension, lateral bending, and axial rotation.
    • Destructive testing: applied increasing force until failure to measure stiffness in flexion and identify the mode of failure for each construct.
  • Statistical analysis was done using ANOVA to compare biomechanical outcomes among the groups.

Results

  • In flexion-extension movement:
    • Both PSR and PSRIFD groups showed significantly reduced ROM, compliance, and neutral zone compared to control spines, indicating increased stability (p < .05).
    • No significant difference between PSR and PSRIFD in these parameters, showing comparable stabilization capacity in this motion plane.
  • In axial rotation:
    • The neutral zone for PSR was significantly lower than for PSRIFD (p = .013), suggesting PSR alone allowed less initial movement.
    • Both PSR and PSRIFD had lower neutral zones than controls, indicating both enhance stability versus natural spine (p < .0001 and p < .02 respectively).
  • Destructive testing (flexion stiffness and failure moments):
    • No significant differences between PSR and PSRIFD groups in stiffness or force/moment required to cause failure.
    • Failure mode for all constructs was dislocation at the articular process joints.
    • PSRIFD constructs also showed ventral migration of the interbody fusion device, indicating a potential additional risk of catastrophic injury with this technique.

Conclusions and Implications

  • PSR constructs alone provide biomechanical stability comparable to PSR plus interbody fusion devices in equine cervical spines under the tested conditions.
  • Since there was no improvement in stabilization but an increased risk of ventral implant migration with PSRIFD, the simpler PSR method may be preferable.
  • Choosing PSR alone could reduce surgical time and risks related to placing interbody fusion devices, potentially minimizing complications during stabilization surgeries in horses.
  • Clinicians can consider these results when deciding stabilization approaches for equine cervical vertebral instability.

Cite This Article

APA
Pezzanite LM, Nelson BB, Downey AC, Gadomski B, McGilvray K, Baer K, Kappel SM, Nout-Lomas Y, Seim HB, Easley JT. (2025). Ex vivo biomechanical comparison of pedicle screw and rod constructs with and without interbody fusion devices for equine cervical vertebral stabilization. Vet Surg, 54(3), 610-620. https://doi.org/10.1111/vsu.14226

Publication

Veterinary surgery : VS
ISSN: 1532-950X
NlmUniqueID: 8113214
Country: United States
Language: English
Volume: 54
Issue: 3
Pages: 610-620

Researcher Affiliations

Pezzanite, Lynn M
  • Department of Clinical Sciences, Colorado State University, Fort Collins, Colorado, USA.
Nelson, Brad B
  • Department of Clinical Sciences, Colorado State University, Fort Collins, Colorado, USA.
Downey, Amy C
  • Department of Clinical Sciences, Colorado State University, Fort Collins, Colorado, USA.
Gadomski, Ben
  • Department of Mechanical Engineering, Colorado State University, Fort Collins, Colorado, USA.
McGilvray, Kirk
  • Department of Mechanical Engineering, Colorado State University, Fort Collins, Colorado, USA.
Baer, Kenzie
  • Department of Mechanical Engineering, Colorado State University, Fort Collins, Colorado, USA.
Kappel, Sarah M
  • Department of Clinical Sciences, Colorado State University, Fort Collins, Colorado, USA.
Nout-Lomas, Yvette
  • Department of Clinical Sciences, Colorado State University, Fort Collins, Colorado, USA.
Seim, Howard B
  • Department of Clinical Sciences, Colorado State University, Fort Collins, Colorado, USA.
Easley, Jeremiah T
  • Department of Clinical Sciences, Colorado State University, Fort Collins, Colorado, USA.

MeSH Terms

  • Animals
  • Horses / surgery
  • Biomechanical Phenomena
  • Cervical Vertebrae / surgery
  • Spinal Fusion / veterinary
  • Spinal Fusion / instrumentation
  • Spinal Fusion / methods
  • Cadaver
  • Pedicle Screws / veterinary
  • Range of Motion, Articular

Grant Funding

  • Preclinical Surgery Research Laboratory and Spine Research Center of Colorado State University

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