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Equine veterinary journal2014; 46(4); 408-415; doi: 10.1111/evj.12241

Bone fatigue and its implications for injuries in racehorses.

Abstract: Musculoskeletal injuries are a common cause of lost training days and wastage in racehorses. Many bone injuries are a consequence of repeated high loading during fast work, resulting in chronic damage accumulation and material fatigue of bone. The highest joint loads occur in the fetlock, which is also the most common site of subchondral bone injury in racehorses. Microcracks in the subchondral bone at sites where intra-articular fractures and palmar osteochondral disease occur are similar to the fatigue damage detected experimentally after repeated loading of bone. Fatigue is a process that has undergone much study in material science in order to avoid catastrophic failure of engineering structures. The term 'fatigue life' refers to the numbers of cycles of loading that can be sustained before failure occurs. Fatigue life decreases exponentially with increasing load. This is important in horses as loads within the limb increase with increasing speed. Bone adapts to increased loading by modelling to maintain the strains within the bone at a safe level. Bone also repairs fatigued matrix through remodelling. Fatigue injuries develop when microdamage accumulates faster than remodelling can repair. Remodelling of the equine metacarpus is reduced during race training and accelerated during rest periods. The first phase of remodelling is bone resorption, which weakens the bone through increased porosity. A bone that is porous following a rest period may fail earlier than a fully adapted bone. Maximising bone adaptation is an important part of training young racehorses. However, even well-adapted bones accumulate microdamage and require ongoing remodelling. If remodelling inhibition at the extremes of training is unavoidable then the duration of exposure to high-speed work needs to be limited and appropriate rest periods instituted. Further research is warranted to elucidate the effect of fast-speed work and rest on bone damage accumulation and repair.
© 2014 EVJ Ltd.
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Publication Date: 2014-04-01 PubMed ID: 24528139DOI: 10.1111/evj.12241Google 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.

This research paper discusses the implications of bone fatigue in racehorses, highlighting it as a potential cause for common musculoskeletal injuries. The paper examines areas with high joint load, such as the fetlock, and how repeated high loading can lead to chronic damage, further explaining the interplay between bone adaptation and remodelling, and the need to balance high-speed work and rest for the overall health of equine bones.

Bone Fatigue and Associated Injuries

  • The article begins by identifying musculoskeletal injuries as a common reason for racehorses’ missed training days. It goes on to link many of these injuries to the phenomenon of bone fatigue, a condition where bones accumulate chronic damage due to repeated high-load forces exerted during fast racing work.
  • The fetlock, a high-load joint, often suffers such damage leading to subchondral bone injuries, a prevalent issue in racehorses. Microcracks at these sites that later develop into intra-articular fractures and palmar osteochondral disease mirror fatigue damage caused by repetitive bone loading.

Fatigue Life and Its Implications

  • Borrowing terminology from material science, the term ‘fatigue life’ is used to denote the number of load cycles a material (in this case, bone) can withstand before failing. This concept is crucial to understanding injuries in racehorses, as the load placed on their limbs increases with their speed, thereby reducing their bones’ fatigue life.

Adaptation and Remodelling of Bone

  • The article elaborates on the dynamic nature of bones, which adapt to heightened load by modelling to keep strains within safe levels. Additionally, bones repair fatigued matrixes through remodelling. When the rate of microdamage supersedes the rate of remodelling, fatigue injuries occur.
  • Training regimen effects bone remodelling in racehorses – it is slowed during race training while sped up during rest periods. The initial phase of remodelling involves bone resorption, which temporarily weakens the bone from increased porosity. As such, a bone that had just completed a rest period and is thus porous, is at a higher risk of failure.

The Importance of Balanced Training and Future Research

  • Hence, maximizing bone adaptation forms a significant part of training young racehorses. This is because even well-adapted bones continue to accumulate microdamage and need constant remodelling. Therefore, if the avoidance of remodelling inhibition during extreme training is impossible, it is important to limit time exposure to high-speed work and ensure appropriate rest periods.
  • The authors conclude by encouraging further research into the effects of fast-speed work and rest on bone damage accumulation and repair, to better understand and address bone fatigue in racehorses.

Cite This Article

APA
Martig S, Chen W, Lee PV, Whitton RC. (2014). Bone fatigue and its implications for injuries in racehorses. Equine Vet J, 46(4), 408-415. https://doi.org/10.1111/evj.12241

Publication

Equine veterinary journal
ISSN: 2042-3306
NlmUniqueID: 0173320
Country: United States
Language: English
Volume: 46
Issue: 4
Pages: 408-415

Researcher Affiliations

Martig, S
  • Faculty of Veterinary Science, The University of Melbourne, Werribee, Victoria, Australia.
Chen, W
    Lee, P V S
      Whitton, R C

        MeSH Terms

        • Animals
        • Biomechanical Phenomena
        • Bone Remodeling / physiology
        • Fractures, Stress / veterinary
        • Horse Diseases / etiology
        • Horses / injuries

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