Veterinary surgery : VS2026; doi: 10.1111/vsu.70166

Cervical articular process joint versus ventral cervical stabilization in horses: A biomechanical study.

Ysebaert, MP
·
Foslien, R
·
David, DM
·
Bonilla, AF
·
Gadomski, BC
·
Easley, JT
·
Nelson, BB

Abstract: To determine the biomechanical properties and modes of failure of a single level equine cervical spine immobilized with unilateral or bilateral articular process joint (APJ) stabilization, ventral cervical stabilization (VCS) and non-stabilized controls. Methods: Ex vivo experimental study. Methods: A total of 24 equine cadaver cervical spines. Methods: Cervical spinal units (C4-C5) were randomly assigned to four groups (n = 6/group): unilateral APJ stabilization, bilateral APJ stabilization, VCS using pedicle screws and rod constructs, or non-stabilized. Non-destructive testing assessed kinematic range of motion (ROM), neutral zone, and stiffness in flexion-extension, axial rotation, and lateral bending. Specimens underwent four-point bending to failure (0.1 mm/s). Radiographs and visual inspection characterized failure mode. Groups were compared using one-way ANOVA or Kruskal-Wallis tests. Significance was p < .05. Results: Non-destructive testing showed unilateral and bilateral APJ constructs were stiffer in flexion-extension, axial rotation and lateral bending than non-stabilized (p < .05). In destructive testing, bilateral APJ stabilization was 2.5× stiffer than VCS, with similar failure moments. Construct stiffness was higher with bilateral APJ stabilization (27.89 ± 5.11 Nm/°) versus non-stabilized (6.92 ± 3.90 Nm/°, p = .0037), unilateral APJ (14.06 ± 2.94 Nm/°, p < .0001) and VCS (11.28 ± 3.01 Nm/°, p < .0001) groups. Failure typically occurred as cranial articular process fracture in both bilateral and unilateral APJ constructs. Conclusions: Bilateral APJ stabilization demonstrated greater stiffness than VCS with comparable failure moments. Conclusions: Bilateral APJ stabilization, with its higher stiffness than VCS, may be an alternative strategy to achieve spinal fusion in horses while avoiding a ventral surgical approach. Future investigations and development of this technique in vivo are warranted before implementation in clinical cases.

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Publication Date: 2026-10-05 PubMed ID: 42834597DOI: 10.1111/vsu.70166Google Scholar: Lookup

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Overview

This study compared the biomechanical strength and failure modes of different stabilization techniques used to immobilize a segment of the equine cervical spine.
Specifically, it evaluated unilateral and bilateral articular process joint (APJ) stabilization against ventral cervical stabilization (VCS) and non-stabilized controls in horse cervical vertebrae.

Background and Purpose

The cervical spine in horses can require stabilization due to injury or disease affecting spinal stability.
Traditional stabilization often involves a ventral surgical approach using screws and rods (VCS), which has certain limitations and risks.
APJ stabilization, either unilateral (one side) or bilateral (both sides), offers a possible alternative that avoids the ventral (front) aspect of the neck.
The study aimed to determine and compare the mechanical properties—stiffness, range of motion, and failure characteristics—of these stabilization methods in an ex vivo (outside living body) equine model.

Methods

24 cadaver cervical spines from horses were prepared, specifically isolating the C4-C5 vertebral unit.
Specimens were randomly assigned to one of four groups (6 specimens each):

Unilateral APJ stabilization (stabilization on one side of the articular process joint)
Bilateral APJ stabilization (both sides)
Ventral cervical stabilization (VCS) using pedicle screws and rods
Non-stabilized controls (no fixation)

Two types of biomechanical testing were performed:

Non-destructive testing measured kinematic parameters: range of motion (ROM), neutral zone (the laxity region), and stiffness during movements including flexion-extension, axial rotation, and lateral bending.
Destructive four-point bending testing assessed failure moments and stiffness until failure occurred at a controlled loading speed.

Radiographs and visual inspection were used post-testing to characterize how and where failures occurred.
Statistical methods included one-way ANOVA and Kruskal-Wallis tests to determine significance with p < 0.05 considered statistically significant.

Results

Non-destructive testing indicated both unilateral and bilateral APJ stabilization increased stiffness compared to non-stabilized controls across all motion planes.
Bilateral APJ stabilization was found to be 2.5 times stiffer than VCS in destructive bending tests, meaning it better resisted deformation before failure.
Specific stiffness measures (in Nm/°) were:

Bilateral APJ: 27.89 ± 5.11
Non-stabilized: 6.92 ± 3.90 (significantly lower)
Unilateral APJ: 14.06 ± 2.94
VCS: 11.28 ± 3.01

Failure modes predominantly involved fractures of the cranial articular process in both unilateral and bilateral APJ groups.
Failure moments (the torque at which failure occurred) were similar across bilateral APJ stabilization and VCS groups despite differences in stiffness.

Conclusions and Clinical Implications

Bilateral APJ stabilization offers higher biomechanical stiffness compared to standard ventral cervical stabilization, suggesting it may provide superior immobilization for inducing spinal fusion.
This method potentially avoids the risks and complications associated with the ventral surgical approach.
The typical failure pattern (cranial articular process fracture) does not preclude clinical use but should be considered during surgical planning.
Authors propose that bilateral APJ stabilization could be a viable alternative for cervical spine stabilization in horses.
Further research is needed, especially in living horses (in vivo), to investigate clinical outcomes and to develop safe and effective surgical protocols based on these biomechanical findings.

Significance and Future Directions

This study provides foundational biomechanical data supporting the concept of APJ stabilization as a promising technique.
If validated in clinical settings, it could improve treatment options for horses with cervical spine instability.
Future investigations should focus on the biological response, healing, and long-term stability following APJ stabilization surgery in live animals.
Development and refinement of surgical tools and techniques tailored for APJ fixation will also be essential.

Cite This Article

APA

Ysebaert MP, Foslien R, David DM, Bonilla AF, Gadomski BC, Easley JT, Nelson BB. (2026). Cervical articular process joint versus ventral cervical stabilization in horses: A biomechanical study. Vet Surg. https://doi.org/10.1111/vsu.70166

Publication

Veterinary surgery : VS

ISSN: 1532-950X

NlmUniqueID: 8113214

Country: United States

Language: English

Researcher Affiliations

Ysebaert, Machiel P

Colorado State University, College of Veterinary Medicine and Biomedical Sciences, Fort Collins, Colorado, USA.

Foslien, Ryan

Orthopedic Bioengineering Research Laboratory, Colorado State University, Fort Collins, Colorado, USA.

David, Donovan M

Colorado State University, College of Veterinary Medicine and Biomedical Sciences, Fort Collins, Colorado, USA.

Bonilla, Andres F

Colorado State University, College of Veterinary Medicine and Biomedical Sciences, Fort Collins, Colorado, USA.

Gadomski, Ben C

Colorado State University, College of Veterinary Medicine and Biomedical Sciences, Fort Collins, Colorado, USA.
Orthopedic Bioengineering Research Laboratory, Colorado State University, Fort Collins, Colorado, USA.

Easley, Jeremiah T

Colorado State University, College of Veterinary Medicine and Biomedical Sciences, Fort Collins, Colorado, USA.

Nelson, Brad B

Colorado State University, College of Veterinary Medicine and Biomedical Sciences, Fort Collins, Colorado, USA.

Grant Funding

American College of Veterinary Surgeons Foundation

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