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Equine veterinary journal2020; 53(2); 294-305; doi: 10.1111/evj.13291

Subchondral focal osteopenia associated with proximal sesamoid bone fracture in Thoroughbred racehorses.

Abstract: Proximal sesamoid bone (PSB) fracture is the most common fatal injury in Thoroughbred (TB) racehorses in the United States. Epidemiological and pathological evidence indicates PSB fracture is likely the acute culmination of a chronic stress-related process. However, the aetiopathogenesis of PSB fracture is poorly understood. Objective: To characterise bone abnormalities that precede PSB fracture. Methods: Two retrospective case-control groups of PSBs from TB racehorses with, and without, unilateral biaxial PSB fracture. Methods: Proximal sesamoid bones were harvested post-mortem from TB racehorses subjected to euthanasia for unilateral biaxial PSB fracture (cases) or causes unrelated to PSB fracture (controls) while racing or training. The fractured medial PSB (FX-PSB) and contralateral intact medial PSB (CLI-PSB) from racehorses that sustained PSB fracture, and an intact medial PSB (CTRL-PSB) from racehorses that did not have a PSB fracture were collected as case and control specimens. Study 1 distributions of morphological features were compared among case and control groups using visual examination, photographs, radiographs and histology of whole PSBs and serial sagittal sections (10 FX-PSB, 10 CLI-PSB and 10 CTRL-PSB). Study 2 local bone volume fraction and mineral densities were compared among case and control PSBs using microcomputed tomography (9 FX-PSB, 9 CLI-PSB and 9 CTRL-PSB). Results: A focal subchondral lesion characterised by colocalised focal discoloration, radiolucency, osteopenia, low tissue mineral density and a surrounding region of dense cancellous bone was identified in most case horses but not in controls. This subchondral lesion was found in a slightly abaxial mid-body location and was bilaterally present in most case horses. Conclusions: The post-mortem samples may not represent the spectrum of abnormalities that occur throughout the development of the subchondral lesion. Lateral PSBs were not examined, so their contribution to biaxial PSB fracture pathogenesis is unknown. Conclusions: Abaxial subchondral lesions are consistent with pre-existing injury and likely associated with PSB fracture.
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Publication Date: 2020-07-23 PubMed ID: 32474944DOI: 10.1111/evj.13291Google Scholar: Lookup
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  • Journal Article

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.

The study focuses on examining the bone abnormalities in Thoroughbred racehorses that could precede a fracture in the Proximal Sesamoid Bone (PSB), a common yet fatal injury in the breed.

Research Objective and Methodology

  • This research explored the bone irregularities which could lead to the Proximal Sesamoid Bone (PSB) fractures in Thoroughbred racehorses, a condition that epidemiological and pathological data suggests is typically an acute result of chronic stress-related processes.
  • Two separate retrospective case-control groups were established to collect data for the research. These were PSBs from Thoroughbred racehorses with and without unilateral biaxial PSB fractures.
  • The PSBs were obtained post-mortem from the Thoroughbred racehorses that were euthanized due to these fractures, while the control group consisted of horses that had been subjected to euthanasia for reasons not related to PSB fractures.
  • Similarly, medial PSBs both from horses with sustained PSB fractures and those without were also collected to serve as case and control specimens.
  • The researchers conducted two studies. The first one compared morphological features among the case and control groups using visual examination, pictures, radiographs, and histology of whole PSBs and serial sagittal sections. The other compared local bone volume fraction and mineral densities among case and control PSBs using microcomputed tomography.

Study Results and Conclusions

  • Most of the horses with fractures displayed a focal subchondral lesion—a region under the cartilage of a joint—characterised by focal discoloration, radiolucency, osteopenia (abnormal reduction of bone mass), reduced tissue mineral density, and surrounded by a dense area of spongy bone. This contrasted with the control group which did not show these features.
  • The subchondral lesion was typically located at a slightly abaxial mid-body location and was bilaterally present in most case horses, indicating a strong link to the fracture.
  • However, it was acknowledged that the post-mortem samples might not fully represent the entire range of abnormalities that occur during the development of the subchondral lesion.
  • Another limitation of the study is that it did not examine the lateral PSBs, hence, their contribution to the pathogenesis of biaxial PSB fractures remains unknown.
  • The researchers ultimately concluded that abaxial subchondral lesions were consistent with a pre-existing injury and most likely linked with PSB fracture.

Cite This Article

APA
Shaffer SK, To C, Garcia TC, Fyhrie DP, Uzal FA, Stover SM. (2020). Subchondral focal osteopenia associated with proximal sesamoid bone fracture in Thoroughbred racehorses. Equine Vet J, 53(2), 294-305. https://doi.org/10.1111/evj.13291

Publication

Equine veterinary journal
ISSN: 2042-3306
NlmUniqueID: 0173320
Country: United States
Language: English
Volume: 53
Issue: 2
Pages: 294-305

Researcher Affiliations

Shaffer, Sarah K
  • Department of Mechanical and Aerospace Engineering, University of California-Davis, Davis, CA, USA.
To, Celeste
  • Department of Surgical and Radiological Sciences, University of California-Davis, Davis, CA, USA.
Garcia, Tanya C
  • Department of Surgical and Radiological Sciences, University of California-Davis, Davis, CA, USA.
Fyhrie, David P
  • Departments of Orthopedic Surgery and Biomedical Engineering, University of California-Davis, Davis, CA, USA.
Uzal, Francisco A
  • California Animal Health and Food Safety Laboratory System, University of California-Davis, Davis, CA, USA.
Stover, Susan M
  • Department of Surgical and Radiological Sciences, University of California-Davis, Davis, CA, USA.

MeSH Terms

  • Animals
  • Bone Diseases, Metabolic / veterinary
  • Fractures, Bone / complications
  • Fractures, Bone / veterinary
  • Horse Diseases / etiology
  • Horses
  • Retrospective Studies
  • Sesamoid Bones
  • X-Ray Microtomography

Grant Funding

  • Grayson Jockey Club Research Foundation, Inc.
  • Center for Equine Health, University of California, Davis
  • Maury Hull Fellowship
  • Louis R. Rowan Fellowship

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Citations

This article has been cited 8 times.
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  2. Shaffer SK, Stover SM, Fyhrie DP. Training drives turnover rates in racehorse proximal sesamoid bones. Sci Rep 2023 Jan 27;13(1):205.
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  3. Shaffer SK, Garcia TC, Stover SM, Fyhrie DP. Exercise history predicts focal differences in bone volume fraction, mineral density and microdamage in the proximal sesamoid bones of Thoroughbred racehorses. J Orthop Res 2022 Dec;40(12):2831-2842.
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