Osseous spinal pathology and epaxial muscle ultrasonography in Thoroughbred racehorses

Authors

  • N. C. STUBBS,

    Corresponding author
    1. Mary Anne McPhail Equine Performance Center, Large Animal Clinical Sciences, College of Veterinary medicine, Michigan State University, East Lansing, USA; The School of Animal Studies, Faculty of Natural Resources, Agriculture and Veterinary Science, The University of Queensland Gatton, Australia
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  • C. M. RIGGS,

    1. Department of Veterinary Clinical Services, Equine Hospital, Sha Tin Racecourse, Hong Kong
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  • P. W. HODGES,

    1. NHMRC Centre for Clinical Research Excellence in Spinal Pain, Injury and Health School of Health and Rehab Sciences, The University of Queensland, Brisbane, Australia
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  • L. B. JEFFCOTT,

    1. Faculty of Veterinary Science, The University of Sydney, Veterinary Teaching Hospital L Block (CO8L-01-102), Camden, New South Wales, Australia
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  • D. R. HODGSON,

    1. Faculty of Veterinary Science, The University of Sydney, Veterinary Teaching Hospital L Block (CO8L-01-102), Camden, New South Wales, Australia
    2. Department of Large Animal Clinical Sciences, VA-MD Regional College of Veterinary Medicine, Virginia Tech, Duck Pond Drive (0442), Blacksburg, Virginia, USA
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  • H. M. CLAYTON,

    1. Mary Anne McPhail Equine Performance Center, Large Animal Clinical Sciences, College of Veterinary medicine, Michigan State University, East Lansing, USA; The School of Animal Studies, Faculty of Natural Resources, Agriculture and Veterinary Science, The University of Queensland Gatton, Australia
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  • C. M. Mc GOWAN

    1. Mary Anne McPhail Equine Performance Center, Large Animal Clinical Sciences, College of Veterinary medicine, Michigan State University, East Lansing, USA; The School of Animal Studies, Faculty of Natural Resources, Agriculture and Veterinary Science, The University of Queensland Gatton, Australia
    2. School of Veterinary Science, Faculty of Health and Life Sciences, University of Liverpool, Leahurst, UK.
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email: stubbsn@cvm.msu.edu

Summary

Reasons for performing study: The multifidus muscle plays a key role in spinal stabilisation. Multifidus atrophy ipsilateral to the side of osseous pathology has been demonstrated in man and pigs but has not been investigated in horses.

Objectives: To measure cross-sectional area (CSA) left/ right symmetry of equine multifidus ultrasonographically and relate asymmetry of multifidus with osseous spinal pathology in Thoroughbred racehorses. We hypothesised that ipsilateral multifidus CSA would be reduced when osseous pathological changes are present leading to left/right asymmetry in CSA.

Materials and methods: Twenty-two racehorses presented for euthanasia for primary reasons other than back pain were examined clinically. Ultrasonographic images on left/right sides were acquired at 5 thoracolumbosacral levels and CSA's of multifidus or sacrocaudalis dorsalis calculated. At necropsy, osseous pathological of the TL spine and pelvis were recorded by spinal level, anatomical site, and graded (0–3) according to severity. The mean typical measurement error in estimating multifidus/sacrocaudalis dorsalis CSA was used to determine the significance of left/right asymmetries. An association between multifidus CSA asymmetry and asymmetrical grading of pathological lesions was sought using Pearson's χ2 analysis.

Results: All horses had significant left/right asymmetry of multifidus CSA at >2 spinal levels, most commonly at L5 with total of 74 sites affected (22 horses). Seventeen horses had severe (grade 3) pathology, 16 of these had ipsilateral atrophy of multifidus/sacrocaudalis dorsalis. There was a significant association between pathological grade and degree of multifidus asymmetry.

Conclusions: Severe osseous pathological changes were common in this population of Thoroughbred racehorses and were associated with measurable left/right asymmetry in multifidus at or close to the level of pathology.

Potential relevance: Ultrasonography of multifidus may be a useful clinical tool in diagnosis of back problems in horses.

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