Animals : an open access journal from MDPI2026; 16(16); 2465; doi: 10.3390/ani16162465

Longitudinal, Objective Fan-Beam Computed Tomographic Evaluation of the Distal Third Metacarpal Bone in 31 Non-Lame Showjumpers.

Höhl, A
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Pollard, D
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Nagy, A

Abstract: Computed tomography (CT) is increasingly used in equine lameness diagnosis, but no objective CT findings have been documented in the fetlock of sport horses. The aim of this study was to describe the pattern and longitudinal changes of densification in the distal third metacarpal bone (McIII) in non-lame showjumpers using CT measurements. Fan-beam CT examination of both metacarpophalangeal regions was performed in 31 non-lame showjumpers in regular work, at four examinations (times 0-3) on 27, 21 and 10 horses, respectively, with a median interval of 10 months. Mean Hounsfield unit (HU) values were recorded on sagittal reconstructions in the dorsal and palmar halves of the medial and lateral condyles, parasagittal grooves, and in the sagittal ridge. Mean dorsal HU values were highest in the medial condyle (1168.7 ± 67.2 HU at time 0) and lowest in the lateral parasagittal groove (947.0 ± 96.2 HU at time 0). Multivariable linear regression analysis showed that dorsal HU increased with showjumping level (3.12 HU per 5 cm increase in fence height; = 0.002) and was higher in medial compared with lateral regions (estimate 28.58 HU; < 0.001). Palmar HU values also increased with competition level (2.27 HU per 5 cm increase; = 0.003) and examination time (6.22 HU per time point; = 0.010). Overall, bone densification was greatest in the condyles, particularly medially. In most regions, no significant changes were detected over time, suggesting limited adaptive bone densification in this population of mature showjumpers over the study period.

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Publication Date: 2026-08-08 PubMed ID: 42651870PubMed Central: PMC13508917DOI: 10.3390/ani16162465Google Scholar: Lookup

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Summary

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Overview

This study used fan-beam computed tomography (CT) to measure bone density changes in the lower leg bones (distal third metacarpal bone) of non-lame showjumping horses over time.
The research aimed to identify patterns of bone densification related to sport level and time in horses regularly competing, contributing objective data about musculoskeletal adaptation in equine athletes.

Background and Objective

Computed tomography (CT) is increasingly employed to diagnose lameness in horses but lacked detailed objective data on the fetlock region—specifically the distal third metacarpal bone in sport horses.
The study focused on well-conditioned, non-lame showjumping horses to establish baseline patterns and longitudinal changes in bone density using CT measurements.
Understanding bone densification helps assess how sporting activity and time impact bone health and adaptation in performance horses.

Study Design and Population

31 non-lame showjumpers actively competing were selected for CT scans of both metacarpophalangeal (fetlock) regions.
Scans were performed at up to four examination points (time 0 to time 3) with a median interval of 10 months between each exam.
The number of horses scanned decreased over time: 31 at time 0, 27 at time 1, 21 at time 2, and 10 at time 3.

Methods: Bone Density Measurement

Using fan-beam CT scans, researchers measured the Hounsfield unit (HU) values, a quantitative scale of radiodensity, at specific anatomical locations in the distal third metacarpal bone.
Measurements focused on sagittal CT reconstructions in the dorsal (front) and palmar (rear) halves across different regions: medial and lateral condyles, parasagittal grooves, and sagittal ridge.
This allowed precise comparison of bone density in different structural parts of the bone important for joint function and stress distribution.

Key Findings

The highest bone density (mean HU) at the start (time 0) was found in the dorsal part of the medial condyle (1168.7 ± 67.2 HU).
The lowest was observed in the lateral parasagittal groove (947.0 ± 96.2 HU), indicating variation in bone density across different sites.
Statistical modeling showed that:
- Dorsal bone density increased with higher showjumping levels: a 3.12 HU increase per 5 cm rise in fence height.
- The medial regions had consistently higher density than the lateral, with a difference estimate of 28.58 HU.
- Palmar bone density (rear half of bone) also increased with competition level and examination time, indicating some bone adaptation over months.
Overall, bone densification was greatest in the condyles, especially the medial condyle, highlighting regions under higher mechanical load during jumping.
Most measured regions did not show significant density changes over time, suggesting limited bone remodeling or adaptation in mature showjumpers within the time frame studied.

Interpretation and Significance

The study objectively confirms that bone density in the distal metacarpal bone is related to the competition level, supporting the idea that mechanical loading from jumping influences bone strength.
The greater density medially correlates with asymmetric loading patterns and may reflect adaptation to stresses experienced predominantly on the medial condyle during activity.
Limited changes over the 10-month intervals imply mature horses may have stable bone density under consistent training rather than rapid adaptive changes.
These baseline CT values and longitudinal data provide important reference points for veterinarians evaluating fetlock health and potential early pathology in showjumpers.
The findings can guide future research and clinical assessment by establishing objective thresholds for normal bone density in equine athletes.

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APA

Höhl A, Pollard D, Nagy A. (2026). Longitudinal, Objective Fan-Beam Computed Tomographic Evaluation of the Distal Third Metacarpal Bone in 31 Non-Lame Showjumpers. Animals (Basel), 16(16), 2465. https://doi.org/10.3390/ani16162465