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The effect of heel elevation on the stiffness gradient index of the digital flexor tendons in the equine forelimb of clinically normal horses.
Abstract: To evaluate the effect of heel elevation on measurement of stiffness gradients by means of acoustoelastography in the digital flexor tendons of clinically normal horses. Unassigned: 15 clinically normal horses. Unassigned: For each horse, stiffness gradient index (SGI) for superficial digital flexor tendons (SDFT) and deep digital flexor tendons (DDFT) were evaluated in both forelimbs at 0, 4 and 8 degrees of heel elevation. Acoustoelastography (AEG) was used for data acquisition at three sites, approximately 6, 12, and 18 cm distal to the accessory carpal bone in the metacarpal region. Lifting the contralateral limb during image acquisition resulted in the application of load and the subsequent SDFT and DDFT deformation required. The effects of loaded versus unloaded digital flexor tendons and right-to-left limb symmetry on SGI at three regions in the metacarpal region were further evaluated. Changes in angulation of the metacarpophalangeal, proximal interphalangeal, and distal interphalangeal (DIP) joints in conjunction with the palmar angle (PA) of the distal phalanx and toe angle (TA) were measured radiographically at 0, 4 and 8 degrees of heel elevation to approximate trends in digital angles with applied heel elevation. Unassigned: SGI values for SDFTs and DDFTs differed significantly in loaded versus unloaded tendons and at different locations of the metacarpus. Incremental heel elevation had the greatest and most consistent effect on the SGI in the mid-metacarpal region in both flexor tendons. At this level, the stiffness gradient tended to decrease when the angle of heel elevation increased from 0 to 8 degrees for both flexor tendons. There was a significant difference in SGI between loading and unloading the limb during AEG acquisition, with reduced variability when the digital flexor tendons were loaded. Unassigned: Results indicated that the SGI of digital flexor tendons was significantly affected by heel elevation. Regarding technique, AEG can be easily and effectively utilized to measure flexor tendon strain in a standing horse with applied heel elevation. This model resulted in direct quantification of tendon strain as it relates to distal limb conformation, which would allow for more targeted therapeutic farriery techniques.
Copyright © 2025 Shaw and Brounts.
Publication Date: 2025-10-01 PubMed ID: 41104281PubMed Central: PMC12522721DOI: 10.3389/fvets.2025.1610788Google Scholar: Lookup The Equine Research Bank provides access to a large database of publicly available scientific literature. Inclusion in the Research Bank does not imply endorsement of study methods or findings by Mad Barn.
- Journal Article
- Animal Study
- Biomechanics
- Clinical Study
- Deep Digital Flexor Tendon
- Diagnostic Technique
- Distal Interphalangeal Joint
- Equine Health
- Equine Medicine
- Farriery
- Imaging Techniques
- Lameness
- Metacarpal Bone
- Metacarpophalangeal Joint
- Musculoskeletal System
- Radiology
- Stiffness
- Superficial Digital Flexor Tendon
- Tendons
- Veterinary Research
Summary
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Overview
- This study investigates how different degrees of heel elevation affect the stiffness gradient index (SGI) of the superficial and deep digital flexor tendons in the forelimbs of healthy horses using acoustoelastography (AEG).
- The research aims to assess tendon stiffness changes at various heel elevations and the potential implications for equine limb conformation and therapeutic farriery.
Introduction and Purpose
- The digital flexor tendons (superficial digital flexor tendon – SDFT, and deep digital flexor tendon – DDFT) play a critical role in equine forelimb biomechanics.
- Heel elevation, often used in farriery, alters limb conformation and could influence tendon stiffness, affecting tendon strain and injury risk.
- The study utilized acoustoelastography (AEG), a technique combining ultrasound with elastography, to non-invasively measure changes in tendon stiffness gradients at different elevations of the hoof heel (0°, 4°, and 8°).
- The goal was to quantify tendon strain relative to changes induced by heel elevation and better understand biomechanical responses for improved therapeutic interventions.
Methods
- Sample: 15 clinically normal horses with no known forelimb tendon pathology.
- Measurement Sites: SGI values were evaluated at three specific locations along the metacarpal region (approximately 6, 12, and 18 cm distal from the accessory carpal bone).
- Heel Elevation: Measurements were taken at neutral (0°), mild (4°), and moderate (8°) heel elevations.
- Loading Conditions: The contralateral limb was lifted during acquisition to induce loading on the tested limb, examining differences between loaded and unloaded tendons.
- Radiographic Analysis: Angles at the metacarpophalangeal, proximal interphalangeal, and distal interphalangeal joints were measured, along with the palmar angle of the distal phalanx and toe angle, to correlate biomechanical changes with anatomical positioning.
Key Findings
- Significant differences in SGI values were observed between loaded and unloaded tendons, with loading resulting in more consistent and reduced variability in measurements.
- SGI values varied by location along the metacarpus, with the mid-metacarpal area (around 12 cm distal) showing the greatest and most consistent changes.
- Incremental heel elevation led to a decrease in stiffness gradient at the mid-metacarpal region for both SDFT and DDFT, indicating increased tendon strain as the heel angle increased from 0° to 8°.
- Changes in joint angulation and distal limb conformation (palmar and toe angles) correlated with alterations in tendon stiffness, elucidating how heel elevation mechanically affects tendon loading.
Implications and Applications
- The study demonstrates that heel elevation significantly influences the stiffness and strain behavior of digital flexor tendons in healthy horses, which is relevant for farriery and rehabilitation practices.
- AEG proved to be a useful and practical tool for assessing tendon biomechanics in standing horses, allowing real-time non-invasive tendon strain quantification under controlled loading conditions.
- Understanding the relationship between heel elevation and tendon stiffness gradients can guide farriers and veterinarians in selecting heel modifications to optimize limb biomechanics and potentially reduce injury risk.
- This research provides a foundation for therapeutic interventions targeting tendon strain through modified hoof conformation, aiding in preventative and rehabilitative strategies for equine athletes.
Cite This Article
APA
Shaw KA, Brounts SH.
(2025).
The effect of heel elevation on the stiffness gradient index of the digital flexor tendons in the equine forelimb of clinically normal horses.
Front Vet Sci, 12, 1610788.
https://doi.org/10.3389/fvets.2025.1610788 Publication
Researcher Affiliations
- Department of Surgical Sciences, School of Veterinary Medicine, University of Wisconsin, Madison, CA, United States.
- Department of Surgical Sciences, School of Veterinary Medicine, University of Wisconsin, Madison, CA, United States.
Conflict of Interest Statement
The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.
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