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Equine veterinary journal2026; 58(3); 674-681; doi: 10.1002/evj.70145

Risk assessment for condylar stress fracture in elite racing Thoroughbreds using standing computed tomography-based virtual mechanical testing.

Abstract: Condylar stress fracture of the third metacarpal bone (MC3) is a common catastrophic injury in Thoroughbred racehorses and is associated with parasagittal groove (PSG) subchondral osteolysis. Standing computed tomography (sCT) imaging enables sensitive identification of this fatigue-induced early subchondral bone injury (SBI), but there is no objective method for identifying racehorses at heightened risk of condylar stress fracture. Objective: To estimate PSG first principal strain in elite Thoroughbred racehorses that have undergone subjective risk assessment using sCT fetlock screening. Methods: Retrospective clinical study. Methods: We used fetlock sCT images from nine thoracic limbs from seven Thoroughbred racehorses. A tuned, validated, 3D finite element (FE) analysis was used as a virtual mechanical test to estimate PSG first principal strain in the distal MC3 from these joints. Virtual mechanical testing results were compared with a subjective clinical imaging risk assessment using a screening approach by Racing Victoria. Results: MC3 condyles with PSG SBI consistently and significantly displayed increased levels of first principal strain throughout the PSG. We found focal strain concentrations associated with the SBI location compared to condyles with no evidence of PSG SBI. Diagnosis of SBI with PSG focal osteolysis, FE-predicted strain elevation, and clinical imaging risk assessment were concordant with R = 0.62. Conclusions: The sample size was small, and our virtual mechanical testing protocol does not account for whole-joint physiology. Conclusions: Risk assessment through sCT screening is an established approach to injury prevention in racing Thoroughbreds. Concordance of a current clinical imaging risk assessment approach by Racing Victoria with objective FE analysis of principal strain in sites of PSG SBI in the present study suggests 3D FE analysis using a validated pipeline has potential as a new approach for routine assessment of risk of MC3 condylar stress fracture in Thoroughbred racehorses once computational pipeline automation yields a clinically relevant analysis time.
© 2026 The Author(s). Equine Veterinary Journal published by John Wiley & Sons Ltd on behalf of EVJ Ltd.
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Publication Date: 2026-01-18 PubMed ID: 41549565DOI: 10.1002/evj.70145Google Scholar: Lookup
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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 study focuses on assessing the risk of condylar stress fractures in elite Thoroughbred racehorses by using standing computed tomography (sCT) images combined with a 3D finite element (FE) mechanical testing method to estimate strain in the third metacarpal bone (MC3).
  • The researchers compared the objective FE analysis with subjective clinical imaging risk assessments to evaluate their agreement and potential for improving injury risk prediction.

Background

  • Condylar stress fractures occur frequently in the MC3 bone of Thoroughbred racehorses, often causing catastrophic injury.
  • These fractures are linked to early bone injury, called subchondral bone injury (SBI), specifically in the parasagittal groove (PSG) region of the bone.
  • Standing computed tomography (sCT) allows sensitive detection of these early bone injuries by producing detailed images while the horse is standing.
  • Despite imaging capabilities, there is no current objective method to clearly identify which horses are at the greatest risk of progressing to condylar stress fracture.

Objective of the Study

  • The primary goal was to estimate mechanical strain (specifically, first principal strain) in the PSG of the MC3 using virtual mechanical testing derived from 3D finite element (FE) analysis applied to sCT data.
  • The study aimed to compare these objective strain measurements with subjective clinical risk assessments performed via sCT imaging to evaluate agreement and potential clinical utility.

Methods

  • The researchers used a retrospective design analyzing sCT images from nine thoracic limbs collected from seven elite Thoroughbred racehorses.
  • A 3D FE model, which was carefully tuned and validated, was employed to simulate mechanical loading and calculate first principal strain across the PSG in the distal MC3 region.
  • FE-derived strain results were then compared to subjective clinical risk assessments performed by Racing Victoria using their imaging screening protocols.

Key Findings

  • MC3 condyles that had evidence of PSG SBI consistently demonstrated significantly higher first principal strain levels when compared to condyles without such injuries.
  • The elevated strains were particularly concentrated around the specific locations of focal SBI, indicating a mechanical underpinning to the sites of early bone injury.
  • There was a moderate positive correlation (R = 0.62) between presence of SBI with focal osteolysis, the FE-predicted elevated strain, and the clinical risk scores assigned by Racing Victoria.

Conclusions and Implications

  • The study supports the use of sCT imaging combined with FE strain analysis as a promising method for the objective risk assessment of condylar stress fractures in racehorses.
  • The agreement between subjective clinical risk assessments and quantitative virtual mechanical testing suggests FE analysis could complement or enhance current screening methods.
  • Limitations include a small sample size and a FE model that does not yet incorporate full joint physiology, potentially affecting the completeness of risk prediction.
  • Further development and automation of the computational pipeline are necessary to reduce analysis time, making this approach feasible for routine clinical use.
  • Ultimately, such integration could improve injury prevention strategies for elite Thoroughbred racehorses by identifying at-risk individuals earlier and more objectively.

Cite This Article

APA
Brown NL, Irandoust S, Thom EJ, Whitton RC, Henak CR, Muir P. (2026). Risk assessment for condylar stress fracture in elite racing Thoroughbreds using standing computed tomography-based virtual mechanical testing. Equine Vet J, 58(3), 674-681. https://doi.org/10.1002/evj.70145

Publication

Equine veterinary journal
ISSN: 2042-3306
NlmUniqueID: 0173320
Country: United States
Language: English
Volume: 58
Issue: 3
Pages: 674-681

Researcher Affiliations

Brown, Nicola L
  • Department of Surgical Sciences, University of Wisconsin-Madison, Madison, Wisconsin, USA.
Irandoust, Soroush
  • Department of Surgical Sciences, University of Wisconsin-Madison, Madison, Wisconsin, USA.
  • Department of Mechanical Engineering, University of Wisconsin-Madison, Madison, Wisconsin, USA.
Thom, Elleana J
  • Department of Surgical Sciences, University of Wisconsin-Madison, Madison, Wisconsin, USA.
  • Department of Mechanical Engineering, University of Wisconsin-Madison, Madison, Wisconsin, USA.
Whitton, R Christopher
  • Department of Veterinary Clinical Sciences, Melbourne Veterinary School, Faculty of Science, University of Melbourne, Werribee, Victoria, Australia.
Henak, Corinne R
  • Department of Mechanical Engineering, University of Wisconsin-Madison, Madison, Wisconsin, USA.
  • Department of Biomedical Engineering, University of Wisconsin-Madison, Madison, Wisconsin, USA.
  • Department of Orthopedics & Rehabilitation, University of Wisconsin-Madison, Madison, Wisconsin, USA.
Muir, Peter
  • Department of Surgical Sciences, University of Wisconsin-Madison, Madison, Wisconsin, USA.

MeSH Terms

  • Animals
  • Horses / injuries
  • Fractures, Stress / veterinary
  • Fractures, Stress / diagnostic imaging
  • Tomography, X-Ray Computed / veterinary
  • Horse Diseases / diagnostic imaging
  • Retrospective Studies
  • Risk Assessment
  • Biomechanical Phenomena
  • Male
  • Mechanical Tests
  • Female
  • Metacarpal Bones / injuries
  • Metacarpal Bones / diagnostic imaging
  • Forelimb

Grant Funding

  • American Veterinary Medical Association
  • MRG-2022-100008 / The Hong Kong Jockey Club Equine Welfare Research Foundation

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