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Journal of anatomy2008; 213(6); 706-717; doi: 10.1111/j.1469-7580.2008.00996.x

Exercise-induced metacarpophalangeal joint adaptation in the Thoroughbred racehorse.

Abstract: Repetitive bone injury and development of stress fracture is a common problem in humans and animals. The Thoroughbred racehorse is a model in which adaptive failure and associated development of stress fracture is common. We performed a histologic study of the distal end of the third metacarpal bone in two groups of horses: young Thoroughbreds that were actively racing (n = 10) and a group of non-athletic horses (n = 8). The purpose of this study was to determine whether development of articular microcracks was associated with specific alterations to subchondral plate osteocytes. Morphometric measurements were made in five regions of the joint surface: lateral condyle, lateral condylar groove, sagittal ridge, medial condylar groove, and medial condyle. The following variables were quantified: hyaline cartilage width; calcified cartilage width; the number of tidemarks; microcrack density at the articular surface; blood vessel density entering articular cartilage; the presence of atypical bone matrix in the subchondral plate; bone volume fraction; and osteocyte density. Adaptation of articular cartilage was similar in both groups of horses. Vascularization of articular cartilage was increased in the group of non-athletic horses. Microcracks, which typically had an oblique orientation to the joint surface, were co-localized with blood vessels, and resorption spaces. Microcracking was increased in the condylar grooves of athletic horses compared with the other joint regions and was also increased compared with the condylar groove regions of non-athletic horses. Coalescence of microcracks also led to development of an intracortical articular condylar stress fracture in some joints and targeted remodeling of affected subchondral plate. The subchondral plate of the condyles in athletic horses was sclerotic, and contained atypically stained bone matrix with increased numbers of osteocytes with atypical morphology. However, osteocyte numbers were not significantly different between groups. We conclude that differences in site-specific microdamage accumulation and associated targeted remodeling between athletic and non-athletic horses are much greater than differences in subchondral osteocyte morphology. However, the presence of atypical subchondral bone matrix in athletic horses was associated with extensive osteocyte loss. Although osteocyte mechanotransduction is considered important for functional adaptation, in this model, adaptation is likely regulated by multiple mechanotransduction pathways.
Publication Date: 2008-12-20 PubMed ID: 19094186PubMed Central: PMC2666139DOI: 10.1111/j.1469-7580.2008.00996.xGoogle Scholar: Lookup
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  • Comparative Study
  • Journal Article
  • Research Support
  • Non-U.S. Gov't

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 research article examines the impact of exercise on the metacarpophalangeal joint of Thoroughbred racehorses, and the differences in joint stress outcomes between athletic and non-athletic horses. The researchers concluded that an accumulation of microdamage and stress in the joints of athletic horses significantly exceeded that of non-athletic horses.

Research Methodology

A comparative analysis was conducted on two groups of horses:

  • young Thoroughbred racehorses that were actively racing (10 horses)
  • non-athletic horses (8 horses)

The study employed histologic examination of the distal end of the third metacarpal bone in the horses’ joints. Morphometric measurements were taken from five regions of the joint surface. The researchers measured a variety of indicators of joint stress, including hyaline cartilage width, microcrack density, blood vessel density, bone volume fraction, and osteocyte density.

Findings and Observations

The study found that the adaptation of articular cartilage was similar in both groups of horses. Interestingly, the non-athletic horses showed increased vascularization of articular cartilage. Microcracks in the joint surface were co-localized with blood vessels and resorption spaces. These microcracks were more prevalent in the condylar grooves of the athletic horses compared to the other joint regions as well as the non-athletic horses.

Joint Stress Outcomes

Microcracks often led to the development of intracortical articular condylar stress fractures in some joints. There was targeted remodeling of the affected subchondral plate. Additionally, the subchondral plate of the condyles in the athletic horses had an atypically stained bone matrix with increased numbers of osteocytes showing abnormal characteristics. However, there were not significant differences in the number of osteocytes between the athletic and non-athletic horses.

Conclusion

The researchers concluded that there were significantly greater differences in site-specific microdamage accumulation and remodeling between athletic and non-athletic horses than differences in osteocyte morphology. However, the presence of an abnormal subchondral bone matrix in the athletic horses was associated with extensive osteocyte loss. While osteocyte mechanotransduction is considered crucial for functional adaptation, it is likely that multiple mechanotransduction pathways regulate adaptation in this model.

Cite This Article

APA
Muir P, Peterson AL, Sample SJ, Scollay MC, Markel MD, Kalscheur VL. (2008). Exercise-induced metacarpophalangeal joint adaptation in the Thoroughbred racehorse. J Anat, 213(6), 706-717. https://doi.org/10.1111/j.1469-7580.2008.00996.x

Publication

ISSN: 1469-7580
NlmUniqueID: 0137162
Country: England
Language: English
Volume: 213
Issue: 6
Pages: 706-717

Researcher Affiliations

Muir, P
  • Comparative Orthopaedic Research Laboratory, School of Veterinary Medicine, University of Wisconsin-Madison, 53706, USA. muirp@svm.vetmed.wisc.edu
Peterson, A L
    Sample, S J
      Scollay, M C
        Markel, M D
          Kalscheur, V L

            MeSH Terms

            • Adaptation, Physiological
            • Animals
            • Bone Remodeling
            • Breeding
            • Calcinosis / pathology
            • Cartilage, Articular / blood supply
            • Cartilage, Articular / pathology
            • Fractures, Bone / pathology
            • Fractures, Stress / pathology
            • Horse Diseases / etiology
            • Horse Diseases / pathology
            • Horses
            • Metacarpophalangeal Joint / blood supply
            • Metacarpophalangeal Joint / injuries
            • Metacarpophalangeal Joint / pathology
            • Metacarpus / blood supply
            • Metacarpus / pathology
            • Microscopy, Confocal
            • Osteocytes / pathology
            • Physical Conditioning, Animal / adverse effects

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