Fatigue fractures in thoroughbred racehorses: relationships with age, peak bone strain, and training.
Abstract: The North American Thoroughbred racehorse was chosen as a model to study the pathogenesis of fatigue failure of bone. This species has a high incidence of spontaneous fatigue failure of bone (bucked shins) during its early training. In vivo strain gauge studies of the third metacarpal bone of four young racehorses running at racing speeds showed high principal compressive strains [-4,841 +/- 572 (SD) microstrain] while two older horses had lower principal compressive strains (-3,317 microstrain measured at racing speed, -3,250 microstrain extrapolated from a slower speed run). Previously reported inertial property measurements of the third metacarpal bone were related to the difference in bone strains seen in young and older horses. The high strains on the surface of the third metacarpal bone associated with young horses in training may lead to high strain, low cycle fatigue. The changing shape of the third metacarpal bone during maturation may be consistent with the lower strains recorded during high speed exercise in the older animals. This phenomenon may allow for the accumulation of additional strain cycles in older animals before failure occurs.
Publication Date: 1990-07-01 PubMed ID: 2355300DOI: 10.1002/jor.1100080417Google Scholar: Lookup
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- Journal Article
- Research Support
- Non-U.S. Gov't
- Research Support
- U.S. Gov't
- Non-P.H.S.
Summary
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This study examines the relationship between age, bone strain, and training with fatigue fractures in the North American Thoroughbred racehorse. The research finds differences in bone strain between younger and older horses, suggesting age and physical maturity may influence susceptibility to bone fatigue and fracture.
Study Evolution and Methodology
- The researchers selected the North American Thoroughbred racehorse as their study’s focus, due to the high rates of spontaneous fatigue failure (commonly referred to as ‘bucked shins‘) that these animals experience during their early training period.
- In vivo strain gauge studies were conducted on the third metacarpal bone in four young racehorses running at racing speeds. This method allowed the team to measure the compressive strains exerted on the bone.
- The same strain gauged studies were also performed on two older horses at racing speed and at a slower speed. These measurements were used as a contrasting set for the results obtained from the younger horses.
Key Findings
- Younger horses exhibited higher principal compressive strains, a measure of the stress endured by a bone, compared to older horses. This difference could contribute to the higher rates of fatigue failure in younger horses.
- Previously reported measurements of the third metacarpal bone’s inertial properties were found to be related to the age-related difference in bone strains. This could suggest that the physical development and maturity of the bone play a role in managing stress during high-speed exercise.
- The high strains recorded on the surface of the third metacarpal bone in young horses during training could lead to a type of failure known as high strain, low cycle fatigue. This means bones are likely to fail (fracture) after fewer cycles of strain in younger horses.
- The changing shape of the third metacarpal bone during growth may partially explain lower strains in older horses. As the horse matures, the bone structure may adapt to better withstand the stresses of high-speed exercise, allowing these horses to bear additional strain cycles before fatigue failure occurs.
This research provides insights into the relationship between age, bone strain, and training intensity in the incidence of fatigue fractures in racehorses. Further studies could explore bone-strain reduction strategies during horse training or identify possible treatments for young horses at high risk of fatigue fractures.
Cite This Article
APA
Nunamaker DM, Butterweck DM, Provost MT.
(1990).
Fatigue fractures in thoroughbred racehorses: relationships with age, peak bone strain, and training.
J Orthop Res, 8(4), 604-611.
https://doi.org/10.1002/jor.1100080417 Publication
Researcher Affiliations
- Comparative Orthopaedic Research Laboratory, University of Pennsylvania School of Veterinary Medicine, Kennett Square 19348.
MeSH Terms
- Aging / pathology
- Animals
- Biomechanical Phenomena
- Fractures, Stress / etiology
- Fractures, Stress / pathology
- Fractures, Stress / veterinary
- Horses / injuries
- Physical Conditioning, Animal
- Stress, Mechanical
Citations
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