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Home / Equine Research Bank / Equine Vet J / Localisation and outcome of presumed thoracolumbar vertebral...
Equine veterinary journal2025; doi: 10.1111/evj.70113

Localisation and outcome of presumed thoracolumbar vertebral stress fracture in 35 UK Thoroughbred racehorses using nuclear scintigraphy.

Abstract: Stress fracture is an important cause of mortality and morbidity in racing Thoroughbreds. Nuclear scintigraphy is the imaging modality of choice for investigating unlocalised stress-related bone remodelling in horses. Stress fractures of the caudal lumbar vertebral column have been previously described in both racing Quarter horses and racing Thoroughbreds post-mortem. There is a lack of literature describing the imaging appearance of vertebral stress fractures in racehorses ante-mortem. Objective: To describe: (1) ante-mortem scintigraphic appearance of presumed thoracolumbar vertebral stress fracture; (2) predilection sites of presumed thoracolumbar stress fracture and compare this to prior post-mortem descriptions; (3) if patient signalment had an association with presumed stress fracture; (4) the prognosis of return to racing post-diagnosis. Methods: Retrospective single-institutional case series. Methods: Thoroughbred racehorses undergoing nuclear scintigraphy during a 10-year period (2009-2019). Images reviewed by two assessors for abnormal increased radiopharmaceutical uptake in the thoracolumbar vertebral column consistent with presumed stress fracture; inclusion by consensus. Chi-square test performed to investigate outcome. Results: Thirty-five racing Thoroughbreds included and 41 presumed stress fractures identified. The caudal lumbar vertebral column was the most common site of presumed thoracolumbar vertebral stress fracture, consistent with previously reported post-mortem findings. The thoracolumbar junction was identified as the second most common site of presumed stress fracture. A positive outcome, defined as return to racing, was present in 65.9% of horses; 95% CI (51.4%, 80.4%). Patient sex was the only factor associated with outcome, with female patients having a lower likelihood of returning to racing. Conclusions: Retrospective observational nature with only a small sample size. Conclusions: The caudal lumbar vertebral column was the most common site of presumed thoracolumbar vertebral stress fracture, followed by the thoracolumbar junction. Lamina/articular process was the most common sublocation. Most horses had a positive outcome. Female sex was the only factor significantly associated with a worse outcome.
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Publication Date: 2025-12-01 PubMed ID: 41327941DOI: 10.1111/evj.70113Google Scholar: Lookup
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Summary

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Overview

  • This study investigated the occurrence, localisation, and outcomes of presumed thoracolumbar vertebral stress fractures in 35 UK Thoroughbred racehorses using nuclear scintigraphy, an imaging technique.
  • It identified common fracture sites and assessed how these injuries impact a horse’s ability to return to racing, with findings on prognosis and factors affecting recovery.

Background and Significance

  • Stress fractures are a significant cause of death and illness in racing Thoroughbred horses.
  • Stress fractures cause bone weakening due to repetitive stress and strain, particularly impacting performance and health.
  • Nuclear scintigraphy is a preferred diagnostic imaging method for detecting bone changes due to stress fractures ante-mortem (before death).
  • Previous descriptions of thoracolumbar vertebral stress fractures have mainly been post-mortem and in different horse breeds, with limited ante-mortem imaging data especially in UK Thoroughbreds.

Study Objectives

  • To describe the ante-mortem scintigraphic (nuclear imaging) appearance of presumed thoracolumbar vertebral stress fractures.
  • To identify the common sites (predilection sites) where these fractures occur and compare with earlier post-mortem findings.
  • To analyze whether horse characteristics (signalment), such as sex and age, are associated with the occurrence or outcome of these fractures.
  • To evaluate the prognosis of horses, specifically their ability to return to racing after diagnosis of these fractures.

Methods

  • A retrospective case series was conducted at a single institution covering 10 years (2009-2019).
  • Inclusion criteria: Thoroughbred racehorses that underwent nuclear scintigraphy of the thoracolumbar area during this period.
  • Two independent assessors reviewed the nuclear scintigraphy images to identify abnormal increased uptake of radiopharmaceuticals consistent with stress fractures in the thoracolumbar spine; consensus was required to include cases.
  • Statistical analysis (Chi-square test) was used to examine the relationship between patient characteristics and outcomes, primarily return to racing.

Key Findings

  • Thirty-five Thoroughbred racehorses were diagnosed with a total of 41 presumptive thoracolumbar vertebral stress fractures.
  • The most common site of these fractures was the caudal lumbar vertebral column, aligning with prior post-mortem reports in racehorses.
  • The second most frequent site was the thoracolumbar junction, another critical biomechanical area prone to stress.
  • Within the vertebral structures, the lamina and articular processes were the most frequent sublocations for fractures.
  • Regarding outcomes, about 65.9% of horses returned to racing after diagnosis, indicating a generally favorable prognosis.
  • Sex was significantly associated with outcome: female horses had a lower rate of returning to racing compared to male horses.

Conclusions and Considerations

  • The study confirms the caudal lumbar vertebral column as the primary site of thoracolumbar vertebral stress fractures in Thoroughbred racehorses, identified ante-mortem by scintigraphy.
  • The thoracolumbar junction is also a notable site of injury.
  • Most horses diagnosed with these fractures can return to racing, but female horses have a statistically lower likelihood of recovery to performance.
  • The retrospective nature and relatively small sample size are important limitations, meaning broader conclusions should be made cautiously.
  • Results emphasize the utility of nuclear scintigraphy for detecting stress-related vertebral injuries in live racehorses and aiding prognosis and management decisions.

Cite This Article

APA
Chapple AR, Daglish J, Stover SM, Slipchenko N, Phillips KL. (2025). Localisation and outcome of presumed thoracolumbar vertebral stress fracture in 35 UK Thoroughbred racehorses using nuclear scintigraphy. Equine Vet J. https://doi.org/10.1111/evj.70113

Publication

Equine veterinary journal
ISSN: 2042-3306
NlmUniqueID: 0173320
Country: United States
Language: English

Researcher Affiliations

Chapple, Alexander R
  • Department of Veterinary Surgery and Radiology, University of California Davis School of Veterinary Medicine, Davis, California, USA.
Daglish, Jodie
  • NEH Cotswolds, Gloucestershire, UK.
Stover, Susan M
  • Department of Veterinary Surgery and Radiology, University of California Davis School of Veterinary Medicine, Davis, California, USA.
Slipchenko, Natalya
  • Research Scholar, Davis, California, USA.
Phillips, Kathryn L
  • Department of Veterinary Surgery and Radiology, University of California Davis School of Veterinary Medicine, Davis, California, USA.

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