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Exercise-induced metacarpophalangeal joint adaptation in the Thoroughbred racehorse.
J Anat. 2008 Dec; 213(6):706-17.JA

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.

Authors+Show Affiliations

Comparative Orthopaedic Research Laboratory, School of Veterinary Medicine, University of Wisconsin-Madison, 53706, USA. muirp@svm.vetmed.wisc.eduNo affiliation info availableNo affiliation info availableNo affiliation info availableNo affiliation info availableNo affiliation info available

Pub Type(s)

Comparative Study
Journal Article
Research Support, Non-U.S. Gov't

Language

eng

PubMed ID

19094186

Citation

Muir, P, et al. "Exercise-induced Metacarpophalangeal Joint Adaptation in the Thoroughbred Racehorse." Journal of Anatomy, vol. 213, no. 6, 2008, pp. 706-17.
Muir P, Peterson AL, Sample SJ, et al. Exercise-induced metacarpophalangeal joint adaptation in the Thoroughbred racehorse. J Anat. 2008;213(6):706-17.
Muir, P., Peterson, A. L., Sample, S. J., Scollay, M. C., Markel, M. D., & Kalscheur, V. L. (2008). Exercise-induced metacarpophalangeal joint adaptation in the Thoroughbred racehorse. Journal of Anatomy, 213(6), 706-17. https://doi.org/10.1111/j.1469-7580.2008.00996.x
Muir P, et al. Exercise-induced Metacarpophalangeal Joint Adaptation in the Thoroughbred Racehorse. J Anat. 2008;213(6):706-17. PubMed PMID: 19094186.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Exercise-induced metacarpophalangeal joint adaptation in the Thoroughbred racehorse. AU - Muir,P, AU - Peterson,A L, AU - Sample,S J, AU - Scollay,M C, AU - Markel,M D, AU - Kalscheur,V L, PY - 2008/12/20/entrez PY - 2008/12/20/pubmed PY - 2009/4/3/medline SP - 706 EP - 17 JF - Journal of anatomy JO - J. Anat. VL - 213 IS - 6 N2 - 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. SN - 1469-7580 UR - https://www.unboundmedicine.com/medline/citation/19094186/Exercise_induced_metacarpophalangeal_joint_adaptation_in_the_Thoroughbred_racehorse_ L2 - https://doi.org/10.1111/j.1469-7580.2008.00996.x DB - PRIME DP - Unbound Medicine ER -