Algometry to measure pain threshold in the horse\u2019s back \u2013 An in vivo and in vitro study

Una Pongratz,Theresia Licka

doi:10.1186/s12917-017-1002-y

Abstract

BackgroundThe aim of this study was to provide information on algometric transmission of pressure through the dorsal thoracolumbar tissues of the equine back. Using a commercially available algometer, measurements were carried out with six different tips (hemispheric and cylindrical surfaces, contact areas 0.5 cm2, 1 cm2, and 2 cm2). In nine live horses the threshold of pressure that lead to any reaction was documented. In postmortem specimens of five euthanized horses the transmission of algometer pressure onto a pressure sensor placed underneath the dorsal thoracolumbar tissues at the level of the ribs or the transverse lumbar processes respectively was measured.ResultsAlgometer tips with a contact area of 1 cm2 led to widely similar results irrespective of the surface shape; these measurements also had the lowest variance. Contact areas of 0.5 cm2 resulted in a lower pressure threshold, and those of 2 cm2 resulted in a higher pressure threshold. The hemispheric shape of the contact area resulted in a higher pressure threshold, than the cylindrical contact area.Compared to the thoracic region, a significantly higher pressure threshold was found in the lumbar region in the live horses. This result corresponds to the increased tissue thickness in the lumbar region compared to the thoracic region, also documented as less pressure transmission in the lumbar region on the in vitro specimens.ConclusionsAlgometry is an easily practicable and well tolerated method to quantify pain but it is important to consider the many factors influencing the results obtained.

Highlights

The aim of this study was to provide information on algometric transmission of pressure through the dorsal thoracolumbar tissues of the equine back
Even though algometry is a quantitative measure for pain thresholds, it is influenced by factors of the examiner and the subject examined [12]
Animals Nine horses without a history of muscular problems, thoracolumbar pain, surgery, wounds or trauma of the back were used for this study

Summary

Introduction

The aim of this study was to provide information on algometric transmission of pressure through the dorsal thoracolumbar tissues of the equine back. Compared to the thoracic region, a significantly higher pressure threshold was found in the lumbar region in the live horses This result corresponds to the increased tissue thickness in the lumbar region compared to the thoracic region, documented as less pressure transmission in the lumbar region on the in vitro specimens. The pressure exerted via the algometer at which a first reaction of the subject of the examination is noted is known as the mechanical nociceptive threshold. This pressure is documented as N (Newton) or kg/cm, and – obviously larger values indicate a higher threshold than smaller values [2].

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