Equine back pain is prevalent among ridden horses and is often attributed to poor saddle fit. An alternative explanation is that saddle fits are technically good but fit to the wrong configuration. Saddles are fit for the standing horse, but much of the time ridden is instead spent locomoting when the back experiences the greatest peak forces. We used an array of cameras to reconstruct the surface of the back and its movement during trot, walk and standing for five horses. We verified the setup\'s accuracy by reconstructing a laser-scanned life-sized model horse. Our reconstructions demonstrate that saddles sit within a large, relatively low-mobile region of the back. However, saddles do sit adjacent to the highly mobile withers, which demands care in positioning and design around this important region. Critically, we identified that saddle curvature between standing and moving horses is substantially different, where trotting and walking horses have flatter backs than their standing configurations. Saddles designed around the locomoting configuration of horses may improve horse welfare by being better fit and decreasing the focal pressures applied by saddles.

Quantifying lumbar back motion during functional activities in real-life environments may contribute to a better understanding of common pathologies such as spinal disorders. The current study therefore aimed at the comparative evaluation of the Epionics SPINE system, a portable device for measuring sagittal lumbar back motion during functional activities. Twenty healthy participants were therefore evaluated with the Epionics SPINE and a Vicon motion capture system in two identical separate research visits. They performed the following activities: standing, sitting, chair rising, box lifting, walking, running and a counter movement jump (CMJ). Lumbar lordosis angles were extracted as continuous values as well as average and range of motion (ROM) parameters. Agreement between the systems was evaluated using Bland-Altman analyses, whereas within- and between-session reliability were assessed using intraclass correlation coefficients (ICC) and minimal detectable changes (MDC). The analysis showed excellent agreement between the systems for chair rising, box lifting and CMJ with a systematic underestimation of lumbar lordosis angles during walking and running. Reliability was moderate to high for all continuous and discrete parameters (ICC ≥ 0.62), except for ROM during running (ICC = 0.29). MDC values were generally below 15°, except for CMJ (peak values up to 20° within and 25° between the sessions). The Epionics SPINE system performed similarly to a Vicon motion capture system for measuring lumbar lordosis angles during functional activities and showed high consistency within and between measurement sessions. These findings can serve researchers and clinicians as a bench mark for future investigations using the system in populations with spinal pathologies.

Major back dimension changes over time have been observed in some horses, the speed of which may be influenced by work type, skeletal maturity, nutrition and saddle fit. Currently, there are no longitudinal data quantifying changes in back dimensions. The objectives of this study were to quantify back dimension changes over time, to identify the effects of horse, saddle and rider on these dimensions, and to determine their association with season, weight, work and saddle management. A prospective, longitudinal study was performed, using stratified random sampling within a convenience sample of 104 sports horses in normal work. Thoracolumbar dimensions/symmetry were measured at predetermined sites every second month over 1 year; weight, work and saddle management changes were recorded. Descriptive statistics, and univariable and multiple mixed effects linear regression were performed to assess the association between management changes, horse-saddle-rider factors and back dimension changes. Complete data was available for 63/104 horses, including horses used for dressage (n= 26), showjumping (n= 26), eventing (n= 26) and general purpose (n= 26), with age groups 3-5 years (n = 24), 6-8 years (n = 28), 9-12 years (n = 24) and ≥ 13 years (n = 28). There were considerable variations in back dimensions over 1 year. In the multivariable analysis, the presence of gait abnormalities at initial examination and back asymmetry were significant and had a negative effect on changes in back dimensions. Subsequent improved saddle fit, similar or increased work intensity, season (summer versus winter) and increased bodyweight retained significance, having positive effects on changes in back dimensions. In conclusion, quantifiable changes in back dimensions occur throughout the year. Saddle fit should be reassessed professionally several times a year, especially if there has been a change in work intensity.

The purpose of this study was to determine the correlation between the back shape of the lumbar region and the spinal loads during activities performed in the sagittal plane. Measurements were performed in four subjects who had suffered from a compression fracture of a lumbar vertebral body which was treated with a telemeterized vertebral body replacement that is able to measure six load components in vivo. An Epionics SPINE measurement system was used to determine the lumbar lordosis angle. The relationship between the lordosis angle and the corresponding loads was quantified with the Spearman\'s rank correlation coefficient method. Measurements were performed during thirteen exercises in lying, standing or sitting. During upper body flexion, the force increased on average by approximately 285N and the lordosis angle decreased by 15°. The change of the force for elevating 30N in one hand was on average approximately 190N and for the lordosis angle 2°. Correlation coefficients greater than 0.6 were found for exercises that involved both large back shape and load changes, such as upper body flexion. A strong increase in spinal load can be associated with an increase or a decrease of the lordosis angle. Only for considerable changes of the lordosis angle in an upright body position was a strong correlation between lordosis angle and implant force found.