Hidden spinal stress fractures in racehorses: scintigraphy reveals sites and prognosis

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

Alexander R. Chapple; Jodie Daglish; Susan M. Stover; Natalya Slipchenko; Kathryn L. Phillips

Background

Stress fractures are a major cause of morbidity and mortality in Thoroughbred racehorses, yet ante-mortem diagnosis of vertebral stress fractures has been poorly described. Previous post-mortem studies indicate a predilection for the caudal lumbar vertebral column, but there is limited literature characterising how these lesions appear on imaging during life. Nuclear scintigraphy is widely used to detect stress-related bone remodelling, and this study aimed to describe scintigraphic features, anatomical distribution, associated signalment factors, and racing outcomes of presumed thoracolumbar vertebral stress fractures in UK Thoroughbred racehorses .

Methods

This was a retrospective single-centre case series of Thoroughbred racehorses that underwent nuclear scintigraphy over a 10-year period (2009–2019). Scans were reviewed for focal increased radiopharmaceutical uptake in the thoracolumbar vertebral column consistent with presumed stress fracture, with inclusion by consensus of two assessors. Vertebral level, sublocation (lamina/articular process, vertebral body, or transverse process), laterality, signalment, and racing discipline were recorded. Outcome was defined as return to racing, determined using a public racing database. Statistical analyses evaluated associations between lesion characteristics, signalment, and outcome.

Results

Thirty-five racehorses were included, with 41 presumed thoracolumbar vertebral stress fractures identified. The caudal lumbar vertebrae were the most common location, followed by the thoracolumbar junction, mirroring prior post-mortem findings. Most lesions involved the lamina/articular process, with fewer affecting the transverse processes or vertebral bodies. A positive outcome, defined as return to racing, occurred in 65.9% of cases. Patient sex was the only factor significantly associated with outcome, with female horses being less likely to return to racing, while lesion location, number of fractures, age, and laterality were not significantly associated with prognosis.

Limitations

The study was retrospective and observational, with a relatively small sample size, limiting statistical power. Definitive confirmation of stress fractures was not available due to the lack of post-mortem or histopathological correlation. Potential confounding factors, such as concurrent injuries, management decisions, and economic influences on retirement—particularly in female horses—could not be fully controlled.

Conclusions

Nuclear scintigraphy can identify presumed thoracolumbar vertebral stress fractures ante-mortem in Thoroughbred racehorses, with lesion distribution closely aligning with previously reported post-mortem data. The caudal lumbar region and lamina/articular process are the most commonly affected sites. Most horses returned to racing following diagnosis, indicating a generally favourable prognosis, although female sex was associated with poorer outcome. These findings support the use of scintigraphy as a key diagnostic tool for racehorses with non-specific lameness or poor performance and suspected vertebral stress injury.

Disclaimer: The summary generated in this email was created by an AI large language model. Therefore errors may occur. Reading the article is the best way to understand the scholarly work. The figure presented here remains the property of the publisher or author and subject to the applicable copyright agreement. It is reproduced here as an educational work. If you have any questions or concerns about the work presented here, reply to this email.