Comparison of Transverse Thoracolumbar Angles in Dressage and Endurance Horses Using 3D Light Scanning and Comparison with Commercial Saddle Gullet Angles

David J. Marlin

doi:10.64292/305rrm51

Authors

David J. Marlin Ergon Equine Ltd, Whittingehame Estate, Haddington EH41 4QA, United Kingdom

DOI:

https://doi.org/10.64292/305rrm51

Keywords:

Back, equestrian, riding, equine, morphometry

Abstract

The thoracolumbar profile is of interest in relation to saddle design and saddle fit. Flexible-curve rulers have previously been used to gather thoracolumbar profiles in horses; however, 3D light scanning offers a potential non-contact alternative method to estimate the cross-sectional shape of the region in greater detail. The aims of this study were to (1) describe the thoracolumbar profiles of endurance and dressage horses using 3D light scanning and (2) compare the wither profiles to saddle manufacturers' gullet bar angles. 3D light scans of the thoracolumbar region were obtained from 23 fit and competing Arabian endurance horses and 21 dressage horses of mixed breed competing at advanced or higher, each from two different stables. Markers were placed by palpation on the caudal scapula (V1) and T18 (V4). Images were imported into Meshmixer. A transversely oriented plane cut was taken at the level of the marker of the left caudal scapula, perpendicular to the back surface (V1), and at the level of the marker at T18. Two further cuts were made at the base of the withers (V2) and the lowest point/midpoint of the back (V3). The mean transverse back angle at V1 was 87 ± 8° for the endurance horse sample and 99 ± 10° for the dressage horse sample (P < 0.0001), and at V4 was 141 ± 7° (endurance) and 144 ± 6° (dressage) (P < 0.0001). For both endurance horses and dressage horses, there was a significant effect of location on back transverse angle (V1 to V4; P < 0.001), with V1 the narrowest and V4 the widest. While there is little consistency in what gullet angle a "medium" gullet bar would actually be, the range of angles measured at the shoulder in the present study reflects the most common gullet sizes offered by six manufacturers of English saddles.

References

Shakeshaft A, Tabor G. The effect of a physiotherapy intervention on thoracolumbar posture in horses. Animals 2020;10:1977. https://doi.org/10.3390/ani10111977.

Caine MP, McConnell AK, Taylor D. Assessment of spinal curvature: an evaluation of the flexicurve and associated means of analysis. International Journal of Rehabilitation Research 1996;19:271–8. https://doi.org/10.1097/00004356-199609000-00009.

Harrison DE, Haas JW, Harrison DD, Holland B, Janik T. Sagittal skin contour of the cervical spine: interexaminer and Intraexaminer reliability of the flexicurve instrument. Journal of Manipulative and Physiological Therapeutics 2005;28:516–9. https://doi.org/10.1016/j.jmpt.2005.07.009.

Society of Master Saddlers. Certificate in saddle fitting (in association with the Society of Master Saddlers). Qualification handbook. City and Guilds; 2019.

Lane D. Equine back profiling system. Dennis Lane n.d. https://www.dennislane.com.au/equine-back-profiling-system (accessed May 1, 2025).

Valberg SJ, Borer Matsui AK, Firshman AM, Bookbinder L, Katzman SA, Finno CJ. 3 Dimensional photonic scans for measuring body volume and muscle mass in the standing horse. PLOS ONE 2020;15:e0229656. https://doi.org/10.1371/journal.pone.0229656.

Borer-Matsui A, Donnelly CG, Valberg SJ. The impact of body position on measurement of equine lumbar and hindquarter volume using 3-dimensional scans. Comparative Exercise Physiology 2023;19:19–26. https://doi.org/10.3920/cep220021.

Tabor GF, Marlin DJ, Williams JM. Use and repeatability of 3D light scanning to measure transverse dorsal profile size and symmetry in the thoracic region in horses. Comparative Exercise Physiology 2022;18:445–51. https://doi.org/10.3920/cep220016.

Pérez-Ruiz M, Tarrat-Martín D, Sánchez-Guerrero MJ, Valera M. Advances in horse morphometric measurements using LiDAR. Computers and Electronics in Agriculture 2020;174:105510. https://doi.org/10.1016/j.compag.2020.105510.

Matsuura A, Dan M, Hirano A, Kiku Y, Torii S, Morita S. Body measurement of riding horses with a versatile tablet-type 3D scanning device. Journal of Equine Science 2021;32:73–80. https://doi.org/10.1294/jes.32.73.

Wang J, Yi T, Liang X, Ueda T. Application of 3D laser scanning technology using laser radar system to error analysis in the curtain wall construction. Remote Sensing 2022;15:64. https://doi.org/10.3390/rs15010064.

Jadayel M, Khameneifar F. Structured-light 3D scanning performance in offline and in-process measurement of 3D printed parts. Procedia CIRP 2024;126:987–92. https://doi.org/10.1016/j.procir.2024.08.372.

Lange R, Böhmer S, Buxbaum B. CMOS-based optical time-of-flight 3D imaging and ranging. High Performance Silicon Imaging 2020:319–75. https://doi.org/10.1016/b978-0-08-102434-8.00011-8.

Askar C, Sternberg H. Use of smartphone lidar technology for low-cost 3D building documentation with iPhone 13 Pro: a comparative analysis of mobile scanning applications. Geomatics 2023;3:563–79. https://doi.org/10.3390/geomatics3040030.

Tabor GF, Johansson C, Randle H. A comparison of measurement techniques of thoracic epaxial musculature in the horse, Liverpool, UK: 2012.

Stubbs NC, Riggs CM, Hodges PW, Jeffcott LB, Hodgson DR, Clayton HM, et al. Osseous spinal pathology and epaxial muscle ultrasonography in Thoroughbred racehorses. Equine Veterinary Journal 2010;42:654–61. https://doi.org/10.1111/j.2042-3306.2010.00258.x.

Marlin DJ, Weaver T, McKeever K, Clayton H, Roepstorff L. A novel 4-dimensional imaging technique to track back shape changes in exercising horses. vol. 18, Uppsala, Sweden: Comparative Exercise Physiology; 2022, p. 1–121. https://doi.org/10.3920/cep2022.s1.

Smirnova KP, Frill MA, Warner SE, Cheney JA. Shape change in the saddle region of the equine back during trot and walk. Journal of The Royal Society Interface 2024;21:20230644. https://doi.org/10.1098/rsif.2023.0644.