Standing magnetic resonance imaging detection of bone marrow oedema-type signal pattern associated with subcarpal pain in 8 racehorses: A prospective study

Authors

  • S. E. POWELL,

    1. Rossdales Equine Diagnostic Centre, Cotton End Road, Exning, Suffolk CB8 7NN; and Beaufort Cottage Stables, High Street, Newmarket, Suffolk CB8 8JS, UK.
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  • P. H. L. RAMZAN,

    1. Rossdales Equine Diagnostic Centre, Cotton End Road, Exning, Suffolk CB8 7NN; and Beaufort Cottage Stables, High Street, Newmarket, Suffolk CB8 8JS, UK.
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  • M. J. HEAD,

    1. Rossdales Equine Diagnostic Centre, Cotton End Road, Exning, Suffolk CB8 7NN; and Beaufort Cottage Stables, High Street, Newmarket, Suffolk CB8 8JS, UK.
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  • M. C. SHEPHERD,

    1. Rossdales Equine Diagnostic Centre, Cotton End Road, Exning, Suffolk CB8 7NN; and Beaufort Cottage Stables, High Street, Newmarket, Suffolk CB8 8JS, UK.
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  • G. I. BALDWIN,

    1. Rossdales Equine Diagnostic Centre, Cotton End Road, Exning, Suffolk CB8 7NN; and Beaufort Cottage Stables, High Street, Newmarket, Suffolk CB8 8JS, UK.
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  • W. N. STEVEN

    1. Rossdales Equine Diagnostic Centre, Cotton End Road, Exning, Suffolk CB8 7NN; and Beaufort Cottage Stables, High Street, Newmarket, Suffolk CB8 8JS, UK.
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Summary

Reason for performing study: The proximal metacarpal region is a common site of origin of lameness in the performance horse. A number of disease entities are recognised as causes of proximal metacarpal lameness but a definitive diagnosis is often elusive. Magnetic resonance imaging (MRI) is hypothesised to offer advantages over traditional imaging modalities in the investigation of proximal metacarpal pain.

Objective: To describe clinical and imaging features of cases of lameness in racehorses arising from the proximal metacarpal region in which standing MRI identified ‘bone marrow oedema-type’ (BMO-type) signal patterns.

Methods: Records for all horses undergoing standing MRI of the proximal metacarpus/distal carpus from September 2006 to December 2008 were reviewed. Cases underwent a standardised protocol for diagnostic analgesia, radiography and ultrasonography of the proximal metacarpus and distal carpus. Cases with proximal metacarpal lameness displaying a characteristic BMO-type signal pattern on MRI were identified and outcomes analysed.

Results: Eight cases were identified with characteristic MRI findings of extensive hyperintensity on T2* gradient echo and short tau inversion fast spin echo sequences and corresponding hypointensity on T1 gradient echo images within the palmaroproximal aspect of the third metacarpal bone. Follow-up information was available for all cases; at the time of writing 7/8 had returned to full work and were free from lameness.

Conclusions: The BMO-type signal patterns visible on MR images in these cases may signal the existence of a previously under-diagnosed pathological process associated with proximal metacarpal lameness in racehorses. This finding is postulated to be associated with a stress reaction and possible prodromal stress fracture of the palmaroproximal metacarpus not appreciable radiographically or ultrasonographically.

Potential relevance: MRI of the proximal metacarpal region permits detection of pathological processes, which may elude conventional imaging and, therefore, has important therapeutic and prognostic implications in these cases.

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