Three-dimensional anatomical description of the microarchitecture of the distal sesamoid bone in healthy and navicular syndrome-affected horses by computed microtomography.
Abstract: Navicular syndrome (NS) is a chronic, degenerative condition of the equine thoracic limb that compromises the distal sesamoid bone (DSB) and associated structures responsible for stabilization and load absorption during locomotion. Although historically attributed to vascular alterations, its etiology is now recognized as biomechanical, characterized by chronic overload of the deep digital flexor tendon. Conventional diagnostic techniques-radiography, scintigraphy, and ultrasonography-lack the sensitivity and precision required to detect early microarchitectural alterations. This study aimed to evaluate changes in the trabecular microarchitecture of the DSB in horses with and without NS using micro-computed tomography (micro-CT) and to explore its diagnostic potential. Samples from eight horses (NS group, n = 4; Not affected group (control), n = 4) were analyzed. Micro-CT images were processed to obtain parameters such as bone volume, relative density, trabecular thickness and separation, porosity, and connectivity. Group comparisons were performed using nonparametric tests and Pearson correlation analyses to explore internal structural relationships. Correlations between groups were then compared using Fisher's Z test. Horses with NS exhibited lower bone volume, trabecular density, thickness, and connectivity, alongside increased trabecular separation, porosity, and anisotropy compared to controls. In healthy horses, strong positive correlations between volume and density, and inverse relationships with trabecular fragmentation, indicated an elevated, well-connected architecture. By contrast, affected horses displayed deteriorated microarchitecture with compensatory trabecular consolidation, reduced trabecular numbers, and a more cylindrical structure-signifying pathological adaptation. Two correlations differed significantly between groups, underscoring disease-induced microstructural reorganization. Micro-CT effectively identified navicular syndrome-specific microarchitectural changes not detectable with conventional methods, yielding quantifiable metrics (thickness, separation, and porosity) that may serve as early diagnostic and monitoring biomarkers. These findings justify broader studies with larger sample sizes and longitudinal designs to validate clinical applicability.
© 2026 American Association for Anatomy.
Publication Date: 2026-01-20 PubMed ID: 41559897DOI: 10.1002/ar.70143Google Scholar: Lookup
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Summary
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Overview
- This study investigated the microarchitectural changes in the distal sesamoid bone of horses affected by navicular syndrome using micro-computed tomography (micro-CT).
- The research identified specific bone structure alterations linked to the disease, suggesting micro-CT as a promising tool for early diagnosis and monitoring of navicular syndrome.
Background
- Navicular Syndrome (NS): A chronic degenerative disease in the forelimbs of horses characterized by damage to the distal sesamoid bone (DSB) and supporting structures.
- Etiology: Previously thought to be caused by vascular issues, current understanding points to biomechanical causes, especially chronic overload of the deep digital flexor tendon.
- Diagnostic Challenges: Traditional imaging modalities such as radiography, scintigraphy, and ultrasonography lack the sensitivity to detect early microarchitectural changes in the DSB associated with NS.
Research Objective
- To assess and compare the microscopic bone structure (microarchitecture) of the distal sesamoid bone in healthy horses and those with navicular syndrome.
- To evaluate the effectiveness of micro-computed tomography (micro-CT) in detecting subtle bone changes related to navicular syndrome.
Methodology
- Sample: Distal sesamoid bone samples collected from eight horses (four with NS and four healthy controls).
- Imaging Technique: Micro-CT scanning used to create detailed 3D images of bone microarchitecture.
- Parameters Measured:
- Bone volume
- Relative bone density
- Trabecular thickness (thickness of tiny bone struts inside the bone)
- Trabecular separation (space between trabeculae)
- Porosity (degree of bone void spaces)
- Connectivity (how well trabeculae interconnect)
- Anisotropy (directional dependence of trabecular architecture)
- Data Analysis: Nonparametric tests for group comparisons and correlation analyses (Pearson and Fisher’s Z tests) to assess internal structural relationships and differences between groups.
Key Findings
- Structural Differences in NS Horses:
- Reduced bone volume, trabecular density, thickness, and connectivity compared to controls.
- Increased trabecular separation, porosity, and anisotropy, indicating a more disorganized bone structure.
- Microarchitectural Patterns in Healthy Horses:
- Strong positive correlations between bone volume and density.
- Inverse relationships between these variables and trabecular fragmentation, indicating a robust, well-connected bone structure.
- Microarchitectural Patterns in NS-Affected Horses:
- Evidence of microarchitectural deterioration with pathological bone adaptation.
- Compensatory trabecular consolidation but fewer trabeculae overall.
- Trabeculae exhibited a more cylindrical structure, reflecting mechanical adaptation to abnormal stress.
- Disease-Specific Correlation Changes:
- Two internal microarchitecture correlations were significantly different between healthy and NS groups.
- This suggests NS induces reorganization of bone microstructure.
Significance and Implications
- Diagnostic Potential: Micro-CT can detect microarchitectural changes in the distal sesamoid bone that conventional methods miss, offering quantifiable metrics like trabecular thickness, separation, and porosity.
- Early Detection and Monitoring: These microarchitectural parameters could act as biomarkers for early diagnosis and tracking the progression of navicular syndrome in horses.
- Future Research: The study recommends larger scale and longitudinal studies to better validate the ability of micro-CT to detect disease progression and evaluate clinical outcomes.
Conclusion
- This study provides a detailed 3D assessment of distal sesamoid bone microarchitecture differences between healthy and navicular syndrome-affected horses using micro-CT.
- The findings highlight specific structural degradations caused by NS and demonstrate micro-CT’s superior sensitivity to these changes compared to conventional imaging methods.
- This approach holds promise for improving clinical diagnosis and management of navicular syndrome in equine patients.
Cite This Article
APA
Salinas P, Vergara MA, Tapia D.
(2026).
Three-dimensional anatomical description of the microarchitecture of the distal sesamoid bone in healthy and navicular syndrome-affected horses by computed microtomography.
Anat Rec (Hoboken).
https://doi.org/10.1002/ar.70143 Publication
Researcher Affiliations
- Laboratory of Animal & Experimental Morphology, Institute of Biology, Faculty of Sciences, Pontificia Universidad Católica de Valparaíso, Valparaíso, Chile.
- Laboratory of Animal & Experimental Morphology, Institute of Biology, Faculty of Sciences, Pontificia Universidad Católica de Valparaíso, Valparaíso, Chile.
- MSc. Program in Biological Sciences, Pontificia Universidad Católica de Valparaíso, Valparaíso, Chile.
- Laboratory of Animal & Experimental Morphology, Institute of Biology, Faculty of Sciences, Pontificia Universidad Católica de Valparaíso, Valparaíso, Chile.
- MSc. Program in Biological Sciences, Pontificia Universidad Católica de Valparaíso, Valparaíso, Chile.
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