Identifying optimal parameters for quantification of changes in pelvic movement symmetry as a response to diagnostic analgesia in the hindlimbs of horses

Adaptation strategies of the Icelandic horse with induced forelimb lameness at walk, trot and tölt

BACKGROUND AND OBJECTIVE

Lameness assessment in the gaited Icelandic horse is complex. We aimed to describe their kinematic and temporal adaptation strategies in response to forelimb lameness at walk, trot and tölt.

STUDY DESIGN

In vivo experiment.

METHODS

Ten clinically non-lame Icelandic horses were measured before and after reversible forelimb lameness induction. Upper body and limb kinematics were measured using 11 inertial measurement units mounted on the poll, withers, pelvis (tubera sacrale) and all four limbs and hoofs (Equimoves®, 500 Hz). Horses were measured on a straight line at walk and trot in-hand and at walk, trot and tölt while ridden. Linear mixed models were used to compare baseline and lame conditions (random factor = 'horse'), and results are presented as the difference in estimated marginal means or percentage of change.

RESULTS

Lameness induction significantly (p < 0.05) increased head vertical movement asymmetry at walk (HDmin/HDmaxHAND: 18.8/5.7 mm, HDmin/HDmaxRIDDEN: 9.8/0.3 mm) and trot (HDmin/HDmaxHAND: 18.1/7.8 mm, HDmin/HDmaxRIDDEN: 24.0/9.3 mm). At the tölt, however, HDmin did not change significantly (1.1 mm), but HDmax increased by 11.2 mm (p < 0.05). Furthermore, pelvis vertical movement asymmetry (PDmax) increased by 4.9 mm, sound side dissociation decreased (-8.3%), and sound diagonal dissociation increased (6.5%). Other temporal stride variables were also affected, such as increased stance duration of both forelimbs at walk, tölt and in-hand trot.

MAIN LIMITATIONS

Only one degree of lameness (mild) was induced with an acute lameness model.

CONCLUSIONS

Classical forelimb lameness metrics, such as vertical head and withers movement asymmetry, were less valuable at tölt compared to walk and trot, except for HDmax. Therefore, it is advised to primarily use the walk and trot to detect and quantify forelimb lameness in the Icelandic horse.

Classification performance of sEMG and kinematic parameters for distinguishing between non-lame and induced lameness conditions in horses

Despite its proven research applications, it remains unknown whether surface electromyography (sEMG) can be used clinically to discriminate non-lame from lame conditions in horses. This study compared the classification performance of sEMG absolute value (sEMGabs) and asymmetry (sEMGasym) parameters, alongside validated kinematic upper-body asymmetry parameters, for distinguishing non-lame from induced fore- (iFL) and hindlimb (iHL) lameness. Bilateral sEMG and 3D-kinematic data were collected from clinically non-lame horses (n = 8) during in-hand trot. iFL and iHL (2-3/5 AAEP) were induced on separate days using a modified horseshoe, with baseline data initially collected each day. sEMG signals were DC-offset removed, high-pass filtered (40 Hz), and full-wave rectified. Normalized, average rectified value (ARV) was calculated for each muscle and stride (sEMGabs), with the difference between right and left-side ARV representing sEMGasym. Asymmetry parameters (MinDiff, MaxDiff, Hip Hike) were calculated from poll, withers, and pelvis vertical displacement. Receiver-operating-characteristic (ROC) and area under the curve (AUC) analysis determined the accuracy of each parameter for distinguishing baseline from iFL or iHL. Both sEMG parameters performed better for detecting iHL (0.97 ≥ AUC ≥ 0.48) compared to iFL (0.77 ≥ AUC ≥ 0.49). sEMGabs performed better (0.97 ≥ AUC ≥ 0.49) than sEMGasym (0.76 ≥ AUC ≥ 0.48) for detecting both iFL and iHL. Like previous studies, MinDiff Poll and Pelvis asymmetry parameters (MinDiff, MaxDiff, Hip Hike) demonstrated excellent discrimination for iFL and iHL, respectively (AUC > 0.95). Findings support future development of multivariate lameness-detection approaches that combine kinematics and sEMG. This may provide a more comprehensive approach to diagnosis, treatment, and monitoring of equine lameness, by measuring the underlying functional cause(s) at a neuromuscular level.

Normal variation in pelvic roll motion pattern during straight-line trot in hand in warmblood horses

In horses, hip hike asymmetry, i.e. left-right difference in hip upwards movement during hind limb protraction in trot, is a crucial lameness sign. Vertical hip movements are complex, influenced by both pelvic roll and pelvic vertical motion. Veterinarians find it challenging to identify low-grade lameness, and knowledge of normal variation is a prerequisite for discerning abnormalities. This study, which included 100 clinically sound Warmblood horses, aimed to describe normal variation in pelvic roll stride patterns. Data were collected during straight-line trot in hand using optical motion capture. Stride-segmented pelvic roll data, normalised with respect to time (0-100% of the stride) and amplitude (± 0.5 of horse average stride range of motion), were modelled as a linear combination of sine and cosine curves. A sine curve with one period per stride and a cosine curve with three periods per stride explained the largest proportions of roll motion: model estimate 0.335 (p < 0.01) and 0.138 (p < 0.01), respectively. Using finite mixture models, the horses could be separated into three groups sharing common pelvic roll characteristics. In conclusion, pelvic roll motion in trot follows a similar basic pattern in most horses, yet there is significant individual variation in the relative prominence of the most characteristic features.

Timing of Vertical Head, Withers and Pelvis Movements Relative to the Footfalls in Different Equine Gaits and Breeds

Simple Summary

Movement symmetry of the head and pelvis are used to measure lameness in horses in trot. Although head, pelvis and limb movements have been described, less is known about the temporal relationships between them. This information is needed to understand how the movements change with lameness. This is particularly relevant in gaited horses, such as the Icelandic horse that perform gaits such as tölt and pace, which are challenging to evaluate. This study used inertial measurement units to investigate head, withers and pelvis motion relative to limb movements in Icelandic, Warmblood and Iberian horses. Limb movements, together with vertical movements and lowest/highest positions of the head, withers and pelvis were calculated, and the relative timing of the events was compared across breeds. Additionally, data for tölt and pace were collected and evaluated in ridden Icelandic horses. For all gaits except walk and pace, the lowest/highest positions of the head/withers/pelvis were closely temporally related to midstance and hoof-off, respectively. Pelvic and withers total range of motion differed between all breeds. The Icelandic horses showed shorter stride duration and smaller movements of the upper body than the other breeds at trot, which may explain why lameness evaluation in this breed is challenging.

Abstract

Knowledge of vertical motion patterns of the axial body segments is a prerequisite for the development of algorithms used in automated detection of lameness. To date, the focus has been on the trot. This study investigates the temporal synchronization between vertical motion of the axial body segments with limb kinematic events in walk and trot across three popular types of sport horses (19 Warmbloods, 23 Iberians, 26 Icelandics) that are known to have different stride kinematics, and it presents novel data describing vertical motion of the axial body segments in tölting and pacing Icelandic horses. Inertial measurement unit sensors recorded limb kinematics, vertical motion of the axial body at all symmetrical gaits that the horse could perform (walk, trot, tölt, pace). Limb kinematics, vertical range of motion and lowest/highest positions of the head, withers and pelvis were calculated. For all gaits except walk and pace, lowest/highest positions of the pelvis and withers were found to be closely related temporally to midstance and start of suspension of the hind/fore quarter, respectively. There were differences in pelvic/withers range of motion between all breeds where the Icelandic horses showed the smallest motion, which may explain why lameness evaluation in this breed is challenging.

Robustness of five different visual assessment methods for the evaluation of hindlimb lameness based on tubera coxarum movement in horses at the trot on a straight line

BACKGROUND

The evaluation of hindlimb lameness remains a major challenge in everyday clinical practice. In the absence of clear guidelines, veterinarians use different visual assessment methods for this task whose robustness is unknown.

OBJECTIVES

Determination of the robustness of five visual hindlimb lameness assessment methods based on the comparison of left and right tuber coxae movement.

STUDY DESIGN

Validated mathematical hindlimb lameness model based on experimental data from the literature.

METHODS

Vertical movement of left (LTC) and right (RTC) tuber coxae was simulated for the range of common hindlimb lameness movement patterns that horses present within practice. Lameness severity ranged from sound to moderately lame (0% to 60% motion asymmetry). The scenarios of a pelvis held tilted and asymmetrical pelvic roll were included to reflect possible adaptations in pelvic rotation. Across all conditions, the outcomes for five different visual assessment methods based on comparative tubera coxarum movement were quantified, including hip hike, -drop and range of motion. The robustness of each assessment method was established through comparison to sacrum-based overall motion asymmetry as the ground truth.

RESULTS

Tubera coxarum-based lameness assessment was highly sensitive to all the unique lameness patterns and changes in pelvic rotation which a lame horse may adopt. None of the five visual lameness assessment methods was 100% robust across all conditions tested. For everyday clinical practice, comparing the upward movement amplitude of the RTC before right hind foot contact and of the LTC before left hind foot contact (Hip_hike_diff) would be the most robust single tubera coxarum-based visual assessment method.

MAIN LIMITATIONS

In the absence of published data regarding the frequency of different movement patterns and hip rotation adaptations in clinical practice, this study cannot indicate the proportion of assessments that would be incorrect for a given visual assessment method.

CONCLUSIONS

Using a single tubera coxarum-based visual hindlimb lameness assessment method may lead to incorrect clinical judgement. Therefore, using multiple assessment methods would be beneficial to substantiate impressions.

Upper Body Movement Symmetry in Reining Quarter Horses during Trot In-Hand, on the Lunge and during Ridden Exercise

Veterinary lameness examinations often comprise assessing ridden horses. Quantitative movement symmetry measurements can aid evidence-based decision making. While these are available for ‘English’ style riding, they are not for ‘Western’ style riding. This quantitative observational study quantified movement symmetry in reining Quarter Horses (QHs). Movement symmetry of the head, withers and sacrum (differences between minima, maxima and upward amplitudes) were quantified with inertial sensors in N = 30 medium/high level reining QHs during trot in-hand, on the lunge and ridden by one experienced rider (straight-line/circles) on reining-purpose riding surfaces. Mixed linear models for movement symmetry assessed the effects of ridden exercise and movement direction (fixed factors), stride time (covariate) and horse (random factor): single factors and two-way interactions with Bonferroni correction at p < 0.05. Three withers and pelvic parameters showed marginally more symmetrical movement when ridden (p ≤ 0.044; 1−5 mm differences). Three withers, three sacrum and one head parameter were significantly affected by movement direction (all p ≤ 0.026), five showed increased asymmetry on the inside rein, and two, quantifying vertical displacement maximum difference, showed the opposite. Riding QHs in ‘Western’ style showed small movement symmetry differences. Circular exercise confirmed increases in weight bearing asymmetry on the inside rein and in pushoff asymmetry on the outside rein. This should be further investigated for differentiating between different causes of lameness.

Smartphone-Based Pelvic Movement Asymmetry Measures for Clinical Decision Making in Equine Lameness Assessment

Simple Summary

As visual evaluation of hindlimb lameness in the horse is challenging, objective measurements could aid clinical decision making. Our study investigated the association of pelvic movement asymmetry, recorded via a smartphone, with lameness scores of one experienced veterinarian. In general, cut-off points between lameness grades increased with increasing severity of lameness. Pelvic upward movement amplitude difference was the asymmetry parameter with the highest discriminative power based on subjective lameness scoring of a specialist veterinarian. This parameter classified a higher proportion of lame and non-lame horses correctly compared to the parameters assessing differences between pelvic vertical movement minima and maxima. Although the use of a smartphone measuring only the symmetry of pelvis cannot replace a full lameness examination, it presents a useful adjunct to subjective evaluation alone. Quantification of pelvic asymmetry with a smartphone may also be a useful tool in the context of tracking progress after a treatment or during the rehabilitation process.

Abstract

Visual evaluation of hindlimb lameness in the horse is challenging. Objective measurements, simultaneous to visual assessment, are used increasingly to aid clinical decision making. The aim of this study was to investigate the association of pelvic movement asymmetry with lameness scores (UK scale 0–10) of one experienced veterinarian. Absolute values of pelvic asymmetry measures, quantifying differences between vertical minima (AbPDMin), maxima (AbPDMax) and upward movement amplitudes (AbPDUp), were recorded during straight-line trot with a smartphone attached to the sacrum (n = 301 horses). Overall, there was a significant difference between lameness grades for all three asymmetry measures (p < 0.001). Five pair-wise differences (out of 10) were significant for AbPDMin (p≤ 0.02) and seven for AbPDMax (p≤ 0.03) and AbPDUp (p≤ 0.02). Receiver operating curves assessed sensitivity and specificity of asymmetry measures against lameness scores. AbPDUp had the highest discriminative power (area under curve (AUC) = 0.801–0.852) followed by AbPDMax (AUC = 0.728–0.813) and AbPDMin (AUC = 0.688–0.785). Cut-off points between non-lame (grade 0) and lame horses (grades 1–4) with a minimum sensitivity of 75% were identified as AbPDUp ≥ 7.5 mm (67.6% specificity), AbPDMax ≥ 4.5 mm (51.9% specificity) and AbPDMin ≥ 2.5 mm (33.3% specificity). In conclusion, pelvic upward movement amplitude difference (AbPDUp) was the asymmetry parameter with the highest discriminative power in this study.

Quantifying the Impact of Mounted Load Carrying on Equids: A Review

Simple Summary

The overloading of equids has become an important issue among veterinarians, trainers, riders, and welfare advocates. Increased weight carrying may have negative effects on biomechanical, physiological, biochemical, and behavioral parameters of equids during exercise, including causing gait asymmetry or lameness. It is important to determine how to carefully quantify the load-carrying capacity of both ridden horses and working equids. There are many options to assess the effect of loading on an animal’s body, but these have been inconsistently applied, making it difficult to reach a consensus, even for horses. This review summarises current knowledge of the load-carrying ability for horses and donkeys and the different parameters used to determine the effect of loading on these equids. Further research is needed to develop evidence-based guidelines for maximum loading in equids. Quantified loading limits or indicators of overloading could be used by stakeholders working with sports and pleasure horses and working equids to limit overloading and to improve the welfare of these animals.

Abstract

There are approximately 112 million working equids in developing countries, many of which are associated with brick kilns. Brick kilns and overloading are associated with welfare problems in working equids. Understanding equids’ abilities and influencing factors are important for both effective performance and welfare. Traditionally, measurement of the amount of ‘bone’ was used, and more recently, gait symmetry has been identified as a potential marker for loading capacity. Assessment of stride parameters and gait kinematics provides insights into adaptations to loading and may help determine cut-off loads. Physiological factors such as the ability to regain normal heart rates shortly after work is an important tool for equine fitness assessment and a more accurate measure of load-carrying capacity than absolute heart rate. Oxidative stress, plasma lactate, and serum creatine kinase activity are reliable biochemical indicators of loading ability. For monitoring stress, salivary cortisol is superior to serum cortisol level for assessment of hypothalamus-pituitary-adrenal axis and is related to eye temperatures, but this has yet to be interpreted in terms of load-carrying ability in equids. Further research is needed to standardize the evidence-based load-carrying capacity of working horses and donkeys.

Movement asymmetries in horses presented for prepurchase or lameness examination

Background

The increasing popularity of objective gait analysis makes application in prepurchase examinations (PPE) a logical next step. Therefore, there is a need to have more understanding of asymmetry during a PPE in horses described on clinical evaluation as subtly lame.

Objectives

The objective of this study is to objectively compare asymmetry in horses raising minor vet concerns in a PPE and in horses raising major vet concerns with that found in horses presented with subtle single‐limb lameness, and to investigate the effect of age/discipline on the clinicians' interpretation of asymmetry on the classification of minor vet concerns in a PPE.

Study Design

Clinical case‐series.

Methods

Horses presented for PPE (n = 98) or subjectively evaluated as single limb low‐grade (1–2/5) lame (n = 24, 13 forelimb lame, 11 hindlimb lame), from the patient population of a single clinic, were enrolled in the study provided that owners were willing to participate. Horses undergoing PPE were assigned a classification of having minor vet concerns (n = 84) or major vet concerns (n = 14) based on findings during the dynamic‐orthopaedic part of the PPE. Lame horses were only included if pain‐related lameness was confirmed by an objective improvement after diagnostic analgesia exceeding daily variation determined for equine symmetry parameters using optical motion capture. Clinical evaluation was performed by six different clinicians, each with ≥8 years of equine orthopaedic experience. Vertical movement symmetry was measured using optical motion capture, simultaneously with the orthopaedic examination. Data were analysed using previously described parameters and mixed model analysis and least squares means were used to calculate differences between groups.

Results

There was no effect of age or discipline on the levels of asymmetry within PPE horses raising minor vet concerns. MinDiff and RUD of the head discriminated between forelimb lame and PPE horses raising minor vet concerns; MinDiff, MaxDiff, RUD of the Pelvis, HHDswing and HHDstance did so for hindlimb lameness. Two lameness patterns differentiated both forelimb and hindlimb lame from PPE horses with minor vet concerns: RUD Poll + MinDiff Withers – RUD Pelvis and RUD Pelvis + RUD Poll − MinDiff Withers. Correcting for vertical range of motion enabled differentiation of PPE horses with minor vet concerns from PPE horses with major vet concerns.

Main Limitations

Objective data only based on trot on soft surface, limited number of PPE horses with major vet concerns.

Conclusions

Combinations of kinematic parameters discriminate between PPE horses with minor vet concerns and subtly lame horses, though overlap exists.

Differential Rotational Movement of the Thoracolumbosacral Spine in High-Level Dressage Horses Ridden in a Straight Line, in Sitting Trot and Seated Canter Compared to In-Hand Trot

Assessing back dysfunction is a key part of the investigative process of "loss of athletic performance" in the horse and quantitative data may help veterinary decision making. Ranges of motion of differential translational and rotational movement between adjacent inertial measurement units attached to the skin over thoracic vertebrae 5, 13 and 18 (T5, T13, T18) lumbar vertebra 3 (L3) and tuber sacrale (TS) were measured in 10 dressage horses during trot in-hand and ridden in sitting trot/canter. Straight-line motion cycles were analysed using a general linear model (random factor: horse; fixed factor: exercise condition; Bonferroni post hoc correction: p < 0.05). At T5-T13 the differential heading was smaller in sitting trot (p ≤ 0.0001, 5.1° (0.2)) and canter (p ≤ 0.0001, 3.2° (0.2)) compared to trotting in-hand (7.4° (0.4)). Compared to trotting in-hand (3.4° (0.4)) at T18-L3 differential pitch was higher in sitting trot (p ≤ 0.0001, 7.5° (0.3)) and canter (p ≤ 0.0001, 6.3° (0.3)). At L3-TS, differential pitch was increased in canter (6.5° (0.5)) compared to trotting in-hand (p = 0.006, 4.9° (0.6)) and differential heading was higher in sitting trot (4° (0.2)) compared to canter (p = 0.02, 2.9° (0.3)). Compared to in-hand, reduced heading was measured in the cranial-thoracic area and increased in the caudal-thoracic and lumbar area. Pitch increased with ridden exercise from the caudal-thoracic to the sacral area.

The Effect of Tree Width on Thoracolumbar and Limb Kinematics, Saddle Pressure Distribution, and Thoracolumbar Dimensions in Sports Horses in Trot and Canter

Simple Summary

Determining the correct saddle fit is essential in order to optimise the interaction between the horse and rider dyad, and to reduce the risk of back-related problems or loss of performance as a result of incorrect saddle fit. Although there are industry guidelines (Society of Master Saddlers) on correct saddle fit, some saddle fitters (and others) choose to fit saddles that are wider than industry guidelines on the assumption that increased saddle width will enhance equine locomotion and allow the horses’ thoracolumbar spine to function unhindered. This study quantified the effect that a saddle that was one width fitting wider and narrower (based on the Society of Master Saddlers industry guidelines) had on the kinematics of the thoracolumbar spine, thoracolumbar epaxial musculature profiles, equine locomotion, and saddle pressure distribution. It was found that a saddle that was one width fitting wider and narrower affected the kinematics of the thoracolumbar spine, resulting in concavities in epaxial musculature at T13 when using the wide saddle and at T18 when using the narrow saddle. The wide saddle caused areas of high pressures in the cranial region of the saddle and the narrow saddle caused areas of high pressures in the caudal region of the saddle. It is essential that the correct saddle fit is achieved for each horse and rider combination in order to optimise the horse-rider system and reduce the risk of back-related problems or loss of performance that may occur as a result of incorrect saddle fit.

Abstract

This study evaluated the effect of saddle tree width on thoracolumbar and limb kinematics, saddle pressure distribution, and thoracolumbar epaxial musculature dimensions. Correctly fitted saddles were fitted by a Society of Master Saddler Qualified Saddle Fitter in fourteen sports horses (mean ± SD age 12 ± 8.77 years, height 1.65 ± 0.94 m), and were altered to one width fitting wider and narrower. Horses were equipped with skin markers, inertial measurement units, and a pressure mat beneath the saddle. Differences in saddle pressure distribution, as well as limb and thoracolumbosacral kinematics between saddle widths were investigated using a general linear model with Bonferroni adjusted alpha (p ≤ 0.05). Compared with the correct saddle width, in trot, in the wide saddle, an 8.5% increase in peak pressures was found in the cranial region of the saddle (p = 0.003), a 14% reduction in thoracolumbar dimensions at T13 (p = 0.02), and a 6% decrease in the T13 range of motion in the mediolateral direction (p = 0.02). In the narrow saddle, a 14% increase in peak pressures was found in the caudal region of the saddle (p = 0.01), an 8% decrease in the range of motion of T13 in the mediolateral direction (p = 0.004), and a 6% decrease in the vertical direction (p = 0.004) of T13. Compared with the correct saddle width, in canter, in the wide saddle, axial rotation decreased by 1% at T5 (p = 0.03) with an 5% increase at T13 (p = 0.04) and a 5% increase at L3 (p = 0.03). Peak pressures increased by 4% (p = 0.002) in the cranial region of the wide saddle. Altering the saddle fit had an effect on thoracolumbar kinematics and saddle pressure distribution; hence, correct saddle fit is essential to provide unhindered locomotion.

Clinical occurrence and radiographic diagnosis of distal limb lameness in equine

The objectives of this study was to evaluate the hospital occurrence of various radiographic lesions of the distal limb (bones and joints) lameness in equine and to evaluate the role of nerve and joint blocks for the localization of lameness in equine. All the equine lameness cases (117), presented during the one year study period that were subjected to radiographic evaluation, were investigated. Out of these, 20 equine lameness cases were subjected to systematic evaluation including nerve / joint blocks to confirm, whether the clinically or radiographically detectedlesion was the primary cause for the lameness or not. Out of 117, 78 equine (66.67%), were diagnosed with 124 radiographic lesions involving 101 limbs. The majority (62.8%) of the equines had single radiographic lesion, whereas the remaining animals were detected with multiple lesions involving one (15.4%) or more limbs (21.8%). Majority cases of equine lameness were recorded in winter season. Highest per cent lesions were recorded in hoofregion (25.81%) with more common involvement of fore feet (68.75%) and in mares (54.54%). Hock and fetlock regions were second (22.6%) and third (21.8%) most common regions for occurrence of equine lameness. Fetlock joint of hindlimb (63%) was more commonly affected than that of the forelimb. In this study, 16 nerve / joint blocks were applied in 15 horses and these were found helpful in confirming the lameness lesions in 66.7% cases. In conclusion, high prevalence of multiple lesions involving one or more limb poses great diagnostic challenge. Forelimb hoof and the hock were most frequently involved in distal limb lameness in equine. Periostitis and arthritis were most prevalent lameness causing lesions in equine. Physical examinations, nerve/ joint bocks and radiography complement each other in confirming the site of lesion causing lameness.

Effect of a unilateral hind limb orthotic lift on upper body movement symmetry in the trotting horse

In trotting horses, movement asymmetry is associated with ground reaction force asymmetry. In humans, limb length differences influence contralateral force production. Here we investigate whether horses, in immediate reaction to limb length changes, show movement asymmetry adaptations consistent with reported force differences. Aim of this study was to quantify pelvic and compensatory head and withers movement asymmetry as a function of limb length changes after application of orthotic lifts. In this experimental study movement asymmetry of eleven trotting horses was calculated from vertical displacement of poll, withers, sacrum and left and right tuber coxae with inertial sensors. Horses were assessed in-hand under 5 conditions (all with hind limb boots): without orthotic lifts, and with a 15mm or 30mm orthotic lift applied to the left hind or right hind. A linear mixed model investigated the influence of orthotic lift condition (P<0.05, pairwise posthoc Bonferroni correction). Pelvic movement asymmetry showed increased pelvic downward movement during stance of the shorter limb and increased pelvic upward movement during and after stance of the longer limb (P<0.001) with asymmetry changes of 3-7mm (4-10mm) for 15mm (30mm) lifts. Hip hike (tuber coxae movement asymmetry) was unaffected (P = 0.348). Head and withers movement asymmetry were affected less consistently (2 of 3 respectively 1 of 3 head or withers parameters). The small sample size of the study reduced generalizability, no direct force measurements were conducted and only immediate effects of orthotic lifts were assessed with no re-assessments days or weeks after. Conclusions about mechanical consequences (weight bearing, pushoff) are based on published movement-force associations. Pelvic movement asymmetry with an artificial change in limb length through application of an orthotic lift indicates increased weight support with the shorter limb and increased pushoff with the longer limb. This may be of relevance for the management of horses with different hoof shapes between contralateral limbs, for example some chronically lame horse.

Repeatability of gait analysis measurements in Thoroughbreds in training

BACKGROUND

With the view of implementing gait symmetry measurements in Thoroughbreds in training for early detection of injuries, repeatability of inertial measurement unit (IMU) gait parameters needs to be established.

OBJECTIVES

To assess the variation of head and pelvis movement symmetry in Thoroughbreds in training.

STUDY DESIGN

Repeated observations in horses in race training.

METHODS

Daily and weekly repeat gait assessments were conducted in 14 Thoroughbreds equipped with IMUs on poll, sacrum and right (RTC) and left (LTC) tuber coxae. Gait was assessed in trot, in-hand, on a level concrete surface. Difference between vertical displacement minima and maxima and range of motion (ROM) were obtained. Ranges containing 50% (median), 75, 90 and 95% of absolute daily and weekly differences were calculated and intraclass correlation coefficients (ICC) calculated for daily and weekly repeats.

RESULTS

Median absolute daily differences ranged from 4 to 7 mm and median weekly differences from 4 to 8 mm. 90% of daily differences were between 9 and 16 mm and 90% of weekly differences between 11 and 19 mm. ICC values were found on average across sensors and gait parameters as 0.73 (ranging from 0.40 to 0.92 across parameters) for daily repeats and as 0.65 (0.27 to 0.91) for weekly repeats.

MAIN LIMITATIONS

Horses were of varying training and movement asymmetry levels, and no veterinary lameness examination was conducted.

CONCLUSIONS

Daily and weekly repeat gait assessments in this group of Thoroughbreds in training show lower ICC values than previously reported from within-day repeats in horses during lameness examinations. We recommend conducting repeatability studies for specific groups of horses when planning long-term studies aiming at identifying horses at risk of injury.

Head, withers and pelvic movement asymmetry and their relative timing in trot in racing Thoroughbreds in training

BACKGROUND

Horses show compensatory head movement in hindlimb lameness and compensatory pelvis movement in forelimb lameness but little is known about the relationship of withers movement symmetry with head and pelvic asymmetry in horses with naturally occurring gait asymmetries.

OBJECTIVES

To document head, withers and pelvic movement asymmetry and timing differences in horses with naturally occurring gait asymmetries.

STUDY DESIGN

Retrospective analysis of gait data.

METHODS

Head, withers and pelvic movement asymmetry and timing of displacement minima and maxima were quantified from inertial sensors in 163 Thoroughbreds during trot-ups on hard ground. Horses were divided into 4 subgroups using the direction of head and withers movement asymmetry. Scatter plots of head vs. pelvic movement asymmetry illustrated how the head-withers relationship distinguishes between contralateral and ipsilateral head-pelvic movement asymmetry. Independent t test or Mann-Whitney U test (P<0.05) compared pelvic movement asymmetry and timing differences between groups.

RESULTS

The relationship between head and withers asymmetry (i.e. same sided or opposite sided asymmetry) predicts the relationship between head and pelvic asymmetry in 69-77% of horses. Pelvic movement symmetry was significantly different between horses with same sign vs. opposite sign of head-withers asymmetry (P<0.0001). Timing of the maximum head height reached after contralateral ('sound') stance was delayed compared to withers (P = 0.02) and pelvis (P = 0.04) in horses with contralateral head-withers asymmetry.

MAIN LIMITATIONS

The clinical lameness status of the horses was not investigated.

CONCLUSION

In the Thoroughbreds with natural gait asymmetries investigated here, the direction of head vs. withers movement asymmetry identifies the majority of horses with ipsilateral and contralateral head and pelvic movement asymmetries. Withers movement should be further investigated for differentiating between forelimb and hindlimb lame horses. Horses with opposite sided head and withers asymmetry significantly delay the upward movement of the head after 'sound' forelimb stance.

Thoracolumbar movement in sound horses trotting in straight lines in hand and on the lunge and the relationship with hind limb symmetry or asymmetry

Equine movement symmetry is changed when turning, which may induce alterations in thoracolumbosacral kinematics; however, this has not previously been investigated. Our objectives were to document thoracolumbar movement in subjectively sound horses comparing straight lines with circles on both reins and to relate these observations to the objectively determined symmetry/asymmetry of hindlimb gait. Fourteen non-lame horses were assessed prospectively in a non-random, cross-sectional survey. The horses were trotted in straight lines and lunged on both reins and inertial sensor data collected at landmarks: withers, T13 and T18, L3, tubera sacrale, and left and right tubera coxae. Data were processed using published methods; angular motion range of motion (ROM; flexion-extension, axial rotation, lateral bending) and translational ROM (dorsoventral and lateral) and symmetry within each stride were assessed. The dorsoventral movement of the back exhibited a sinusoidal pattern with two oscillations per stride. Circles induced greater asymmetry in dorsoventral movement within each stride (mean ± standard deviation, up to 9 ± 6%) compared with straight lines (up to 6 ± 6%). The greatest amplitude of dorsoventral movement (119 ± 14 mm in straight lines vs. 126 ± 20 mm in circles) occurred at T13. Circles induced greater flexion-extension ROM (>1.3°; P = 0.002), lateral bending (>16°; P <0.001), and lateral motion (>16 mm; P = 0.002) compared with straight lines. Circles induced a movement pattern similar to an inside hindlimb lameness, which was significantly associated with the circle-induced greater asymmetry of dorsoventral movement of the thoracolumbar region (P = 0.03). Moving in a circle induces measurable changes in thoracolumbar movement compared with moving in straight lines, associated with alterations in the hindlimb gait.

Associations of force plate and body-mounted inertial sensor measurements for identification of hind limb lameness in horses

OBJECTIVE

To investigate associations between inertial sensor and stationary force plate measurements of hind limb lameness in horses.

ANIMALS

21 adult horses with no lameness or with mild hind limb lameness.

PROCEDURES

Horses were instrumented with inertial sensors and evaluated for lameness with a stationary force plate while trotting in a straight line. Inertial sensor-derived measurements of maximum and minimum pelvic height differences between right and left halves of the stride were compared with vertical and horizontal ground reaction forces (GRFs). Stepwise linear regression was performed to investigate the strength of association between inertial sensor measurements of hind limb lameness and amplitude, impulse, and time indices of important events in the vertical and horizontal GRF patterns.

RESULTS

Difference in minimum pelvic position was moderately (Ra(2) = 0.60) associated with the difference in peak vertical GRF but had little association with any horizontal GRF measurements. Difference in maximum pelvic position was strongly (Ra(2) = 0.77) associated with a transfer of vertical to horizontal ground reaction impulse in the second half of the stance but was not associated with difference in peak vertical GRF.

CONCLUSIONS AND CLINICAL RELEVANCE

Inertial sensor-derived measurements of asymmetric pelvic fall (difference in minimum pelvic position) indicated a decrease in vertical GRF, but similar measurements of asymmetric pelvis rise (difference in maximum pelvic position) indicated a transfer of vertical to horizontal force impulse in the second half of the stance. Evaluation of both pelvic rise and fall may be important when assessing hind limb lameness in horses.

Comparison of a standalone consumer grade smartphone with a specialist inertial measurement unit for quantification of movement symmetry in the trotting horse

REASONS FOR PERFORMING STUDY

Equine inertial measurement unit (IMU) gait analysis has gained in popularity for use in horses. Similar transducers are now found in consumer grade smartphones. However, to date there are no scientific data evaluating their use for assessment of movement (a)symmetry in the horse.

OBJECTIVES

To establish limits of agreement (LoA, mean difference ±2 s.d.) between a validated specialist IMU system and IMU data collected with a consumer grade smartphone for quantification of movement symmetry and range of motion (ROM) of pelvic movement in the trotting horse.

STUDY DESIGN

Method comparison study based on quantitative gait data.

METHODS

Twenty horses were equipped with a specialist IMU (MTw, Xsens) and a consumer grade smartphone (Apple iPhone6), both securely attached immediately in front of one another in the midline over the sacrum. Horses were trotted in-hand and lunged on both reins on a soft arena surface. Median values for movement symmetry and ROM were determined over a series of strides for each exercise condition. Data collection was repeated in 6 horses to determine the effect of mediolateral sensor positioning on outcome parameters.

RESULTS

Valid data from 17 horses resulted in LoA values of -3.7 ± 9.2 mm for MinDiff (difference between left and right hind mid stance), -0.6 ± 6.0 mm for MaxDiff (difference between left and right hind propulsion) and -0.8 ± 7.4 mm for ROM across horses and exercises. LoAs were narrower for straight line exercise and the negative bias was considerably reduced when moving the smartphone to the right of the midline.

CONCLUSIONS

The consumer grade smartphone provided meaningful gait data in horses: LoAs in particular for in-hand exercise and when adjusting the mediolateral positioning are similar to published asymmetry thresholds. Owing to the sensitivity to mediolateral positioning, particular care should be taken when placing an IMU over the midline of the horse.

Understanding hind limb lameness signs in horses using simple rigid body mechanics

Hind limb lameness detection in horses relies on the identification of movement asymmetry which can be based on multiple pelvic landmarks. This study explains the poorly understood relationship between hind limb lameness pointers, related to the tubera coxae and sacrum, based on experimental data in context of a simple rigid body model. Vertical displacement of tubera coxae and sacrum was quantified experimentally in 107 horses with varying lameness degrees. A geometrical rigid-body model of pelvis movement during lameness was created in Matlab. Several asymmetry measures were calculated and contrasted. Results showed that model predictions for tubera coxae asymmetry during lameness matched experimental observations closely. Asymmetry for sacrum and comparative tubera coxae movement showed a strong association both empirically (R(2)≥ 0.92) and theoretically. We did not find empirical or theoretical evidence for a systematic, pronounced adaptation in the pelvic rotation pattern with increasing lameness. The model showed that the overall range of movement between tubera coxae does not allow the appreciation of asymmetry changes beyond mild lameness. When evaluating movement relative to the stride cycle we did find empirical evidence for asymmetry being slightly more visible when comparing tubera coxae amplitudes rather than sacrum amplitudes, although variation exists for mild lameness. In conclusion, the rigidity of the equine pelvis results in tightly linked movement trajectories of different pelvic landmarks. The model allows the explanation of empirical observations in the context of the underlying mechanics, helping the identification of potentially limited assessment choices when evaluating gait.

Lungeing on hard and soft surfaces: Movement symmetry of trotting horses considered sound by their owners

REASONS FOR PERFORMING STUDY

Lungeing is often part of the clinical lameness examination. The difference in movement symmetry, which is a commonly employed lameness measure, has not been quantified between surfaces.

OBJECTIVES

To compare head and pelvic movement symmetry between surfaces and reins during lungeing.

STUDY DESIGN

Quantitative gait analysis in 23 horses considered sound by their owners.

METHODS

Twenty-three horses were assessed in-hand and on the lunge on both reins on hard and soft surfaces with inertial sensors. Seven movement symmetry parameters were quantified and used to establish 2 groups, namely symmetrical (n = 9) and forelimb-lame horses (n = 14), based on values from straight-line assessment. Movement symmetry values for left rein measurements were side corrected to allow comparison of the amount of movement symmetry between reins. A mixed model (P<0.05) was used to study effects on movement symmetry of surface (hard/soft) and rein (inside/outside with respect to movement symmetry on the straight).

RESULTS

In forelimb-lame horses, surface and rein were identified as significantly affecting all head movement symmetry measures (rein, all P<0.0001; surface, all P<0.042). In the symmetrical group, no significant influence of surface or rein was identified for head movement symmetry (rein, all P>0.245; surface, all P>0.073). No significant influence of surface or rein was identified for any of the pelvic movement symmetry measures in either group.

CONCLUSIONS

While more symmetrical horses showed a consistent amount of movement symmetry across surfaces/reins, horses objectively quantified as lame on the straight showed decreased movement symmetry during lungeing, in particular with the lame limb on the inside of a hard circle. The variation within group questions straight-line movement symmetry as a sole measure of lameness without quantification of movement symmetry on the lunge, ideally on hard and soft surfaces to evaluate differences between reins and surfaces. In future, thresholds for lungeing need to be determined using simultaneous visual and objective assessment.