Elsevier

The Veterinary Journal

Volume 186, Issue 3, December 2010, Pages 347-351
The Veterinary Journal

Comparison of pressure plate and force plate gait kinetics in sound Warmbloods at walk and trot

https://doi.org/10.1016/j.tvjl.2009.08.024Get rights and content

Abstract

Modern pressure plates (PP) could be an alternative to traditional force plates (FP) for quantitative equine gait analysis, thereby providing the clinician with objective data on the horse’s gait while unravelling the loading of different regions of the hoof during the stance phase. The aim of this study was to determine whether a stand-alone PP allows reliable measurement of gait kinetics, compared to simultaneously recorded FP variables. Six sound Warmblood horses were walked and trotted over a combined PP and FP system for collection of a set of five valid kinetic measurements for each forelimb. A measurement was considered valid if the horse was moving in a straight line at a constant pace while gait velocity was within a preset range and the hoof fully contacted the plate surface.

Significant differences between FP and PP data were seen for peak vertical force (PVF), vertical impulse (VI), time at which the PVF occurs (tPVF) and forelimb symmetry ratios (SymPVF and SymVI) (P < 0.05), but not for stance phase duration (ST). Nevertheless, mean agreement indices (AIs) of ST, tPVF and SymPVF and SymVI were excellent (⩾0.92), whereas AIs of PVF and VI were moderate (⩾0.70). The excellent agreement between PP and FP symmetry ratios confirms that observed differences between PP and FP in symmetry ratios are small (2–7%), especially when compared to the expected decrease in symmetry associated with mild lameness (>20%). The results indicate that a stand-alone pressure plate can be used to measure absolute (ST) and relative (tPVF) temporal variables and loading symmetry ratios and offers equine veterinarians a mobile, cost-efficient and quick gait evaluation method for routine clinical use. However, the system cannot be used interchangeably with a force plate to measure absolute values of limb loading.

Introduction

Force plates (FPs) are accepted kinetic instruments for the quantitative evaluation of equine lameness (Buchner, 2001, Bertone, 2003, Ishihara et al., 2009). Despite their recognised accuracy, the use of FP systems is usually restricted to gait analysis under laboratory environments as installation procedures are laborious and costly as the FP requires a massive concrete foundation, while concurrent hoof strikes cannot be separated and limited plate dimensions preclude recording consecutive strides (Buchner, 2001, Bertone, 2003).

Modern portable pressure plate (PP) systems open new possibilities, whereby additional information on the pressure distribution of the different regions of the hoof during a complete stance period can be obtained (Van der Tol et al., 2003, Van Heel et al., 2004). This may allow us to differentiate toe and heel landing in specific causes of lameness (e.g. navicular syndrome vs. laminitis).

PP measurements can be dynamically calibrated using simultaneous FP measurements (Van der Tol et al., 2003, Van Heel et al., 2004, De Cock et al., 2005, Hagman et al., 2008). However, the combination of a built-in and fixed FP and PP is really only feasibly in an institute or laboratory and is not practical use in a cost-efficient, mobile clinical environment. Solitary PPs, operational without concurrent FP calibration, have been applied in horses (Rogers and Back, 2007, Oosterlinck et al., 2010) and humans (Thijs et al., 2007). However, before kinetic data obtained with a stand-alone PP can be used clinically, validation of the system for precision (i.e. agreement between repeated measurements) and accuracy (i.e. agreement with reference standard) is necessary (Bossuyt et al., 2003).

A high level of precision of gait kinetics and loading symmetry ratios has been demonstrated in ponies using a stand-alone PP (Oosterlinck et al., 2010). Studies specifically dealing with the accuracy of a pressure measuring system compared to a FP have been undertaken in humans (Chesnin et al., 2000) and dogs (Besançon et al., 2003). The former reported excellent correlation between the centre of pressure determined by an in-shoe pressure measuring system and a FP, while the latter reported statistically significant differences in gait kinetics between the FP and PP systems. Equine bodyweight (BW), gait variables (stride length, etc.) and conformation are very different compared to other animal species and humans, necessitating direct comparison of simultaneously recorded PP and FP measurements.

A practical application can be foreseen when variables determined from the stand-alone PP could be used interchangeably with FP measurements, thereby providing valuable and objective information on the horse’s gait and symmetry. This would offer the equine clinician a cost-efficient, quick and even portable gait evaluation method for routine clinical use. The objective of the present study was to compare gait kinetics in a group of sound horses using simultaneous measurements with a PP and a FP. The hypothesis was tested that the kinetic gait variables of the PP and the FP can be used interchangeably.

Section snippets

Horses

Six healthy and clinically sound Dutch Warmblood mares were included in the study (mean age 7 ± 4 SD years, BW 592 ± 82 kg; wither height 1.59 ± 0.07 m). All horses were part of the teaching herd of Utrecht University, and were regularly used for pleasure riding by the student riding school. Prior to the study, each horse was physically evaluated by a veterinarian and judged to be healthy and sound.

The study was approved by the Ethical Committee of Utrecht University (2008.III.07.071).

Measurement systems and data collection

After a 5 min

Results

A representative example of vertical force curves at walk and at trot, obtained with both measuring systems, is shown in Fig. 2. PP and FP measurements at walk and trot of all horses (n = 6), and AIs are summarised in Table 1.

Except for the symmetry ratios, analyses were conducted on pooled LF and RF data of the six horses since no significant differences were found between both forelimbs. All variables showed significant differences between the walk and trot. PVF, VI and tPVF obtained with the

Discussion

The vertical force curves at walk and trot, obtained with both measuring systems, showed a similar pattern as reported earlier by Oosterlinck et al. (2010). Nevertheless, in the present study the actual PVF recorded with the PP showed a lower maximal value and was recorded somewhat later in the stance phase compared to the FP measurement.

Absolute stance duration recorded with PP and FP was similar and excellent agreement between both measuring systems was identified for relative temporal

Conclusions

We are aware that this stand-alone PP cannot simply replace a FP when high accuracy of absolute force values is needed for scientific purposes. Extended calibration may help to reduce measuring errors. Nevertheless, the available PP system can be used stand-alone to evaluate temporal variables and kinetic symmetry ratios in horses. Moreover, with PP measurements, the pressure distribution of the different regions of the hoof during a complete stance phase might become unravelled (Van der Tol et

Conflict of interest statement

None of the authors of this paper has a financial or personal relationship with other people or organisations that could inappropriately influence or bias the content of the paper.

Acknowledgements

The authors wish to thank Dr. Hans Vernooij (Utrecht University) and Professor Jeroen Dewulf (Ghent University) for their assistance with statistical analyses, and Dr. Meike Van Heel (Mustad Hoofcare) for critically reading the manuscript.

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