Effect of lungeing on head and pelvic movement asymmetry in horses with induced lameness

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.

Changes in the equine facial repertoire during different orthopedic pain intensities

A number of facial expressions are associated with pain in horses, however, the entire display of facial activities during orthopedic pain have yet to be described. The aim of the present study was to exhaustively map changes in facial activities in eight resting horses during a progression from sound to mild and moderate degree of orthopedic pain, induced by lipopolysaccharides (LPS) administered in the tarsocrural joint. Lameness progression and regression was measured by objective gait analysis during movement, and facial activities were described by EquiFACS in video sequences (n = 348, total length 892.5 min) of the horses obtained when resting in their box stalls. Predictive modeling identified 16 action units and action descriptors, related to ears, eyes, and lower face. Lower lip depressor (AU16), lips part (AU25), half blink (AU47), single ear forward (SEAD101) and single ear rotator (SEAD104) were selected as co-occurring significantly more in horses with pain than in horses without pain. The major change in co-occurring facial activities occurred in the transition from no pain to mild pain. In conclusion, resting horses with induced orthopedic pain showed a dynamic upper and lower facial repertoire and the relationship between level of pain intensity and facial activity appears complex.

Withers vertical movement symmetry is useful for locating the primary lame limb in naturally occurring lameness

BACKGROUND

During orthopaedic assessment of lame horses, a head nod is commonly present in both primary forelimb and hindlimb lame horses. Additional motion metrics that could assist clinicians in correctly differentiating between these two scenarios would be of great clinical value.

OBJECTIVES

The primary objective of this study was to examine whether withers movement asymmetry can be used in a clinical setting to distinguish primary forelimb lameness from compensatory head movement asymmetry due to primary hindlimb lameness.

STUDY DESIGN

Retrospective, multicentre study.

METHODS

Movement asymmetry of head, withers and pelvis was measured using multi-camera optical motion capture, as part of routine lameness investigations at four European equine hospitals. Vertical movement asymmetry parameters from 317 horses trotting in a straight line were compared before and after successful diagnostic analgesia of a single limb. Descriptive statistics, t-tests and linear models were used to analyse the data.

RESULTS

In forelimb lame horses, 80%-81% showed head and withers asymmetry both indicating lameness in the same forelimb. In hindlimb lame horses, 69%-72% showed head asymmetry ipsilateral to the lame hindlimb and withers asymmetry diagonal to the lame hindlimb, thus, head and withers asymmetry indicated lameness in different forelimbs. A large (>15 mm) compensatory head nod was seen in 28%-31% of the hindlimb lame horses. In 89%-92% of these, head and withers asymmetry indicated lameness in different forelimbs. Withers asymmetry decreased linearly with reduced head or pelvic asymmetry for both forelimb and hindlimb lame horses.

MAIN LIMITATIONS

Compensatory strategies were evaluated on group level to identify common patterns, potentially ignoring uncommon individual strategies.

CONCLUSIONS

Withers vertical movement asymmetry metrics can be useful in helping to locate the primary lame limb during quantitative lameness assessment. Head and withers movement asymmetry parameters generally indicate the same forelimb in forelimb lame horses, but different forelimbs in hindlimb lame horses.

Asymmetry Thresholds Reflecting the Visual Assessment of Forelimb Lameness on Circles on a Hard Surface

The assessment of lameness in horses can be aided by objective gait analysis tools. Despite their key role of evaluating a horse at trot on a circle, asymmetry thresholds have not been determined for differentiating between sound and lame gait during this exercise. These thresholds are essential to distinguish physiological asymmetry linked to the circle from pathological asymmetry linked to lameness. This study aims to determine the Asymmetry Indices (AIs) with the highest power to discriminate between a group of sound horses and a group of horses with consistent unilateral lameness across both circle directions, as categorized by visual lameness assessment conducted by specialist veterinarians. Then, thresholds were defined for the best performing AIs, based on the optimal sensitivity and specificity. AIs were calculated as the relative comparison between left and right minima, maxima, time between maxima and upward amplitudes of the vertical displacement of the head and the withers. Except the AI of maxima difference, the head AI showed the highest sensitivity (≥69%) and the highest specificity (≥81%) for inside forelimb lameness detection and the withers AI showed the highest sensitivity (≥72%) and the highest specificity (≥77%) for outside forelimb lameness detection on circles.

Comparing Inertial Measurement Units to Markerless Video Analysis for Movement Symmetry in Quarter Horses

BACKGROUND

With an increasing number of systems for quantifying lameness-related movement asymmetry, between-system comparisons under non-laboratory conditions are important for multi-centre or referral-level studies. This study compares an artificial intelligence video app to a validated inertial measurement unit (IMU) gait analysis system in a specific group of horses.

METHODS

Twenty-two reining Quarter horses were equipped with nine body-mounted IMUs while being videoed with a smartphone app. Both systems quantified head and pelvic movement symmetry during in-hand trot (hard/soft ground) and on the lunge (left/right rein, soft ground). Proportional limits of agreement (pLoA) were established.

RESULTS

Widths of pLoA were larger for head movement (29% to 50% in-hand; 22% to 38% on lunge) than for pelvic movement (13% to 24% in-hand; 14% to 24% on lunge).

CONCLUSION

The between-system pLoAs exceed current "lameness thresholds" aimed at identifying the affected limb(s) in lame horses. They also exceed published limits of agreement for stride-matched data but are similar to repeatability values and "lameness thresholds" from "non-lame" horses. This is encouraging for multi-centre studies and referral-level veterinary practice. The narrower pLoA values for pelvic movement asymmetry are particularly encouraging, given the difficulty of grading hind limb lameness "by eye".

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.

Artificial Intelligence for Lameness Detection in Horses-A Preliminary Study

Lameness in horses is a long-known issue influencing the welfare, as well as the use, of a horse. Nevertheless, the detection and classification of lameness mainly occurs on a subjective basis by the owner and the veterinarian. The aim of this study was the development of a lameness detection system based on pose estimation, which permits non-invasive and easily applicable gait analysis. The use of 58 reference points on easily detectable anatomical landmarks offers various possibilities for gait evaluation using a simple setup. For this study, three groups of horses were used: one training group, one analysis group of fore and hindlimb lame horses and a control group of sound horses. The first group was used to train the network; afterwards, horses with and without lameness were evaluated. The results show that forelimb lameness can be detected by visualising the trajectories of the reference points on the head and both forelimbs. In hindlimb lameness, the stifle showed promising results as a reference point, whereas the tuber coxae were deemed unsuitable as a reference point. The study presents a feasible application of pose estimation for lameness detection, but further development using a larger dataset is essential.

Performance of four equine pain scales and their association to movement asymmetry in horses with induced orthopedic pain

Objective

This study investigated the relationship between orthopedic pain experienced at rest, and degree of movement asymmetry during trot in horses with induced reversible acute arthritis. Orthopedic pain was assessed with the Horse Grimace Scale (HGS), the Equine Utrecht University Scale of Facial Assessment of Pain (EQUUS-FAP), the Equine Pain Scale (EPS), and the Composite Orthopedic Pain Scale (CPS). Reliability and diagnostic accuracy were evaluated with intraclass correlation coefficients (ICC) and area under the curve (AUC).

Study design and animals

Eight healthy horses were included in this experimental study, with each horse acting as its own control.

Methods

Orthopedic pain was induced by intra-articular lipopolysaccharide (LPS) administration. Serial pain assessments were performed before induction and during pain progression and regression, where three observers independently and simultaneously assessed pain at rest with the four scales. Movement asymmetry was measured once before induction and a minimum of four times after induction, using objective gait analysis.

Results

On average 6.6 (standard deviation 1.2) objective gait analyses and 12.1 (2.4) pain assessments were performed per horse. The ICC for each scale was 0.75 (CPS), 0.65 (EPS), 0.52 (HGS), and 0.43 (EQUUS-FAP). Total pain scores of all scales were significantly associated with an increase in movement asymmetry (R² values ranging from −0.0649 to 0.493); with CPS pain scores being most closely associated with movement asymmetry. AUC varied between scales and observers, and CPS was the only scale where all observers had a good diagnostic accuracy (AUC > 0.72).

Conclusions and clinical relevance

This study identified significant associations between pain experienced at rest and degree of movement asymmetry for all scales. Pain scores obtained using CPS were most closely associated with movement asymmetry. CPS was also the most accurate and reliable pain scale. All scales had varying linear and non-linear relations between total pain scores and movement asymmetry, illustrating challenges with orthopedic pain assessment during rest in subtly lame horses since movement asymmetry needs to be rather high before total pain score increase.

The Effect of 12 Weeks of Saddle Horse Conversion Training on Thoroughbred Horse Gait

The unwanted horse problem is the most serious issue confronting the equestrian industry. Thus, it is recommended that retired racehorses switch to become saddle horses for ‘the second life of a racing veteran’ because training and using retired Thoroughbred racehorses as saddle horses is the most cost-effective option. The current study aimed to analyze the effects of saddle horse conversion training on gaits of retired Thoroughbred racehorses. Our study included 12 retired Thoroughbred racehorses. These Thoroughbred racehorses performed the retraining 20–50 min a day, five times per week for three months. There are some critical findings in this study. The results show that the decreased stride length of each foot decreased the displacements of the center of mass and the center of the head. In addition, after retraining, there was a significant decrease in the head–neck angle and displacement between the center of the head and the center of the neck. These changes in the horse’s movements mean that the habitual movements for racing are gradually changed to optimal movements for a saddle horse.

The Effects of the EquiAmiTM Training Aid on the Kinematics of the Horse at the Walk and Trot In-Hand

The EquiAmi Training Aid (ETA) is a popular training and rehabilitation tool, however knowledge about its effect on the equine gait is lacking. Understanding of its effects on equine kinematics, and the clinical relevance of these effects is vital to promote optimal use of training aids within training and rehabilitation programmes. Therefore, this study aimed to determine how the ETA influences horses' gait kinematics at walk and trot. Eight horses walked and trotted in-hand with and without the ETA. Optical motion capture was used to measure forelimb and hindlimb pro- and retraction angles, withers-croup angle, and stride length. Separate repeated-measures ANOVAs in each gait were used to assess the differences between gait kinematics and stride length variability with and without the ETA. The ETA did not significantly influence the horses' kinematics in walk or trot, however, individual differences in the effect of the ETA on the horses' angular and linear kinematics were found, with variation between gaits within the same horse observed. The ETA does not have the same effect on every horse, and its effect can vary within the same horse between gaits. Therefore, the individual characteristics and needs of the horse must be considered when applying training aids.

Linear Discriminant Analysis for Investigating Differences in Upper Body Movement Symmetry in Horses before/after Diagnostic Analgesia in Relation to Expert Judgement

Simple Summary

Identifying the anatomical structures involved in causing pain and an associated lameness in a horse typically requires assessment in straight lines and circles and using regional administration of local anesthetic drugs (diagnostic analgesia). Visual assessment of changes in movement are affected by bias, i.e., expected changes influence decisions. Quantitative measurements with inertial sensors aim at removing this bias. The current study is aimed at investigating how a specific data-driven method, linear discriminant analysis (LDA), may be useful for aiding veterinary decision making about perceived changes in lameness. Changes in movement data after diagnostic analgesia and expert judgements from 53 lame horses were used to study (a) the accuracy of LDA-based decision making, (b) differences between straight-line and circular movement and (c) which commonly used movement features are most useful in this context. Accuracy was comparatively low and varied considerably between 36% and 57%, indicating considerable overlap between movement symmetry data of the diagnostic analgesia categories. The best data-driven separation between categories was observed when the limb in which perineural anaesthesia had been performed was on the inside of the circle (on hard ground for forelimb and on soft ground for hindlimb diagnostic analgesia). Movement features of all three landmarks (head, withers, pelvis) were important for data-driven classification, emphasizing the complexity of the movement pattern changes after diagnostic analgesia observed in lame horses.

Abstract

Diagnostic analgesia and lunging are parts of the equine lameness examination, aiding veterinarians in localizing the anatomical region(s) causing pain-related movement deficits. Expectation bias of visual assessment and complex movement asymmetry changes in lame horses on the lunge highlight the need to investigate data-driven approaches for optimally integrating quantitative gait data into veterinary decision-making to remove bias. A retrospective analysis was conducted with inertial sensor movement symmetry data before/after diagnostic analgesia relative to subjective judgement of efficacy of diagnostic analgesia in 53 horses. Horses were trotted on the straight and on the lunge. Linear discriminant analysis (LDA) applied to ten movement asymmetry features quantified the accuracy of classifying negative, partial and complete responses to diagnostic analgesia and investigated the influence of movement direction and surface type on the quality of the data-driven separation between diagnostic analgesia categories. The contribution of movement asymmetry features to decision-making was also studied. Leave-one-out classification accuracy varied considerably (38.3–57.4% for forelimb and 36.1–56.1% for hindlimb diagnostic analgesia). The highest inter-category distances (best separation) were found with the blocked limb on the inside of the circle, on hard ground for forelimb diagnostic analgesia and on soft ground for hindlimb diagnostic analgesia. These exercises deserve special attention when consulting quantitative gait data in lame horses. Head and pelvic upward movement and withers minimum differences were the features with the highest weighting within the first canonical LDA function across exercises and forelimb and hindlimb diagnostic analgesia. This highlights that movement changes after diagnostic analgesia affect the whole upper body. Classification accuracies based on quantitative movement asymmetry changes indicate considerable overlap between subjective diagnostic analgesia categories.

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.

In vivo joint synovial fluid disposition of a novel sustained-release formulation of diclofenac and hyaluronic acid in horses

Intra-articular administration of sustained-release anti-inflammatory drugs is indicated in horses suffering from joint inflammation, but no such drugs are labelled for veterinary use. To obtain initial data on synovial disposition and safety of a new sustained-release formulation of diclofenac (SYN321) in the joints of horses, an experimental interventional study of elimination and side effects of intra-articular administration of SYN321 was conducted. Nine clinically sound horses were included in the study, and SYN321 was administered by the intra-articular route. Dose ranges and sampling intervals were established in a pilot study with two horses, and then applied in a main study involving seven horses treated in the fetlock joint. Diclofenac was detected above lower limit of quantification (LOQ: 0.5 ng/ml) in synovial fluid throughout the study period (14 days), and below LOQ (0.1 ng/ml) in plasma after 4 days and in urine after 14 days. No obvious clinical side effects were detected. Clinical examination and objective lameness evaluation suggested that SYN321 has potential as a local joint NSAID treatment with sustained release in horses, but further studies on synovial fluid exposure, safety and clinical efficacy are warranted.

Effect of Speed and Surface Type on Individual Rein and Combined Left-Right Circle Movement Asymmetry in Horses on the Lunge

Differences in movement asymmetry between surfaces and with increasing speed increase the complexity of incorporating gait analysis measurements from lunging into clinical decision making. This observational study sets out to quantify by means of quantitative gait analysis the influence of surface and speed on individual-rein movement asymmetry measurements and their averages across reins (average-rein measurements). Head, withers, and pelvic movement asymmetry was quantified in 27 horses, identified previously as presenting with considerable movement asymmetries on the straight, during trot in hand and on the lunge on two surfaces at two speeds. Mixed linear models (p < 0.05) with horse as the random factor and surface and speed category (and direction) as fixed factors analyzed the effects on 11 individual-rein and average-rein asymmetry measures. Limits of agreement quantified differences between individual-rein and average-rein measurements. A higher number of individual-rein asymmetry variables-particularly when the limb that contributed to movement asymmetry on the straight was on the inside of the circle-were affected by speed (nine variables, all p ≤ 0.047) and surface (three variables, all p ≤ 0.037) compared with average-rein asymmetry variables (two for speed, all p ≤ 0.003; two for surface, all p ≤ 0.046). Six variables were significantly different between straight-line and average-rein assessments (all p ≤ 0.031), and asymmetry values were smaller for average-rein assessments. Limits of agreement bias varied between +0.4 and +4.0 mm with standard deviations between 3.2 and 12.9 mm. Fewer average-rein variables were affected by speed highlighting the benefit of comparing left and right rein measurements. Only one asymmetry variable showed a surface difference for individual-rein and average-rein data, emphasizing the benefit of assessing surface differences on each rein individually. Variability in straight-line vs. average-rein measurements across horses and exercise conditions highlight the potential for average-rein measurements during the diagnostic process; further studies after diagnostic analgesia are needed.

Differences in equine spinal kinematics between straight line and circle in trot

Work on curved tracks, e.g. on circles, is commonplace within all forms of horse training. Horse movements in circles are naturally asymmetric, including the load distribution between inner and outer limbs. Within equestrian dressage the horse is expected to bend the back laterally to follow the circle, but this has never been studied scientifically. In the current study 12 horses were measured (optical motion capture, 100 Hz) trotting on left and right circles and on the straight without rider (soft surface). Data from markers placed along the spine indicated increased lateral bending to the inside (e.g. left bending on the left circle) of the thoracolumbar back (difference left circle vs. straight − 3.75°; right circle + 3.61°) and the neck (left − 5.23°; right + 4.80° vs. straight). Lateral bending ROM increased on the circle (+ 0.87° and + 0.62°). Individual variation in straight-circle differences was evident, but each horse was generally consistent over multiple trials. Differences in back movements between circle and straight were generally small and may or may not be visible, but accompanying changes in muscle activity and limb movements may add to the visual impression.

Rater agreement for assessment of equine back mobility at walk and trot compared to quantitative gait analysis

Background

Lameness assessment in horses is still predominantly performed using subjective methods. Visual assessment is known to have moderate to good intra-rater agreement but relatively poor inter-rater agreement. Little is known about inter- and intra-rater agreement on the evaluation of back motion, for which no objective measurement technique in a clinical setting is available thus far.

Objectives

To describe inter- and intra-rater agreement of visual evaluation of equine back mobility.

Study design

Rater reliability study using a fully crossed design in which all horses are rated by all observers. This data is compared with objective gait analysis.

Methods

Seventy equine professionals (veterinarians and physiotherapists) and veterinary students evaluated videos of 12 healthy horses at walk and trot on a hard, straight line. Nine parameters related to back mobility were scored: general mobility, thoracic, lumbar, lumbosacral flexion and extension and left and right thoracolumbar latero-flexion. All parameters were compared with simultaneously measured quantitative motion parameters. After 1 month, six randomly chosen horses were re-evaluated by 57 observers.

Results

For each parameter inter- and intra-rater agreements were calculated using intra-class correlation coefficients. For all parameters, inter-rater agreement was very poor (<0.2). The mean intra-rater agreement of all observers and for all parameters was poor (~0.4) but varied between 0.0 and 0.96 for individual observers. There was no correlation between the visual subjective scoring and objective gait analysis measurements.

Main limitations

Horses were scored from videos and by lack of any existing (semi-) quantitative system, a custom-made system had to be used.

Conclusions

The poor inter- and intra-rater agreements of visual scoring of mobility of the equine back and the disagreement between subjective and objective gait analysis data, demonstrate the need for the development and introduction of objective, quantitative and repeatable techniques to assess equine back motion.

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.

Continuous versus discrete data analysis for gait evaluation of horses with induced bilateral hindlimb lameness

Background

Gait kinematics measured during equine gait analysis are typically evaluated by analysing (asymmetry‐based) discrete variables (eg, peak values) obtained from continuous kinematic signals (eg, timeseries of datapoints). However, when used for the assessment of complex cases of lameness, such as bilateral lameness, discrete variable analysis might overlook relevant functional adaptations.

Objectives

The overall aim of this paper is to compare continuous and discrete data analysis techniques to evaluate kinematic gait adaptations to lameness.

Study design

Method comparison.

Methods

Sixteen healthy Shetland ponies, enrolled in a research programme in which osteochondral defects were created on the medial trochlear ridges of both femurs, were used in this study. Kinematic data were collected at trot on a treadmill before and at 3 and 6 months after surgical intervention. Statistical parametric mapping and linear mixed models were used to compare kinematic variables between and within timepoints.

Results

Both continuous and discrete data analyses identified changes in pelvis and forelimb kinematics. Discrete data analyses showed significant changes in hindlimb and back kinematics, where such differences were not found to be significant by continuous data analysis. In contrast, continuous data analysis provided additional information on the timing and duration of the differences found.

Main limitations

A limited number of ponies were included.

Conclusions

The use of continuous data provides additional information regarding gait adaptations to bilateral lameness that is complementary to the analysis of discrete variables. The main advantage lies in the additional information regarding time dependence and duration of adaptations, which offers the opportunity to identify functional adaptations during all phases of the stride cycle, not just the events related to peak values.

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.

Non-banked curved tracks influence movement symmetry in two-year-old Standardbred trotters

BACKGROUND

Little is known regarding how trotting through curves affects locomotion symmetry in Standardbred trotters.

OBJECTIVES

To investigate differences in objectively measured Standardbred trotter vertical motion symmetry between straight and non-banked, curved sections of oval trotting tracks during exercise warm-up, using a wireless inertial measurement unit (IMU) system.

STUDY DESIGN

Cross-sectional, observational study.

METHODS

Sixteen horses were included. Mixed models were used to assess associations between symmetry, track segment (straight vs curve) and stride duration.

RESULTS

Significant results for forelimb parameters were dependent on interactions between track segments and stride duration. At mean stride duration (0.611 second), during the curved track segment horses showed a lower maximum vertical position of the head after push-off of the outside forelimb (estimate -2.3 mm, P < 0.0001, 95% CI -1.7 to -2.9) and higher minimum vertical position of the head during stance of the outside forelimb (estimate -1.8 mm, P < 0.0001, 95% CI -1.2 to -2.5) compared to straight track, mimicking outside forelimb impact and push-off asymmetry during track curves. For hindlimb parameters, during the curve there was a decreased downward motion of the pelvis during outer hindlimb stance (estimate-0.7 mm, P < 0.0001, 95% CI -0.4 to -1.0), mimicking outside hindlimb impact asymmetry.

MAIN LIMITATIONS

Horses were evaluated going in one direction only on the track (clockwise).

CONCLUSIONS

Systematic differences between straight and curved track segments were found but did not fully correspond to previously described findings for horses lunged in circles. Effect sizes were overall small. Data in our study were collected from horses trotting on 1000 m tracks with curve radii of 80-85 m. On non-banked tracks of this size, collecting IMU symmetry data at jogging speeds without distinguishing between straight and curved parts is unlikely to adversely affect clinical decision-making.

Upper body movement analysis of multiple limb asymmetry in 367 clinically lame horses

BACKGROUND

Compensatory lameness is common in horses and evaluation can be challenging.

OBJECTIVES

To investigate patterns of compensatory movements in clinical cases with fore- or hindlimb lameness before and after diagnostic analgesia.

STUDY DESIGN

Retrospective clinical study.

METHODS

Multiple limb lameness of 367 horses was characterised by type (push-off, impact or mixed), limb (fore- or hindlimb in predominant lameness) and side (ipsi- or contralateral in concurrent lameness) using a body-mounted inertial sensor (BMIS). Diagnostic analgesia was performed until the percentage improvement of the vector sum in forelimb lameness and the mean difference of the maximum or minimum pelvic height (PD_max or PD_min ) in hindlimb lameness was ≥50%. Linear mixed model and post-estimation of effects were performed by contrast command with multiple comparisons adjusted by Bonferroni method. Correlation of pre- and post-analgesia of all head and pelvis asymmetry parameters was tested with Spearman's rank correlation.

RESULTS

Improvement in vector sum per mm after diagnostic analgesia in forelimb impact lameness positively correlated with decrease in PDmax in contralateral mixed lameness (0.187 mm, r = .58, P < .05). Improvement in PD_min per mm after diagnostic analgesia in hindlimb mixed and PD_max in hindlimb push-off lameness decreased vector sum in ipsilateral forelimb impact lameness by 0.570 and 0.696 mm, respectively (P < .05), with no positive correlation.

MAIN LIMITATIONS

A variety of cases with inhomogeneous distribution of lameness patterns was investigated retrospectively, therefore, it is impossible to distinguish between true multiple limb lameness and compensatory lameness in this clinical material.

CONCLUSIONS

Various asymmetry patterns of concurrent lameness were seen in horses with naturally occurring primary forelimb impact lameness with contralateral compensatory hindlimb lameness with a mixed component being the most common. In horses with hindlimb lameness, compensatory movements were seen in ipsilateral forelimbs, mostly as an ipsilateral impact lameness during straight line trot.

Objectively measured movement asymmetry in yearling Standardbred trotters

BACKGROUND

Lameness evaluation of Standardbred trotters can be challenging due to discrepancies in observed movement asymmetry between in-hand and track exercise, and between different trotting speeds. There are few studies on objective measurement of movement in Standardbreds, and little knowledge regarding biological variation and clinical significance of measured movement asymmetry in this breed.

OBJECTIVES

To quantify the prevalence and magnitude of objectively measured movement asymmetry in young Standardbred trotters, and identify associations with trainer, sex, height, track type and in-hand measurement prior to or after track trials.

STUDY DESIGN

Cross-sectional, observational study.

METHODS

A total of 114 Standardbred yearlings were evaluated with a wireless inertial sensor system during trot in-hand and when driven on a track. After exclusions relating to lameness or technical difficulties, 103 horses were included in the study; 77 were evaluated in-hand and on the track, 24 only in-hand and 2 only on the track.

RESULTS

Front and/or hindlimb parameters were above asymmetry thresholds previously established for other breeds during in-hand trials for 94 (93%) horses and during track trials for 74 (94%) horses. Most horses showed mild asymmetry. A minority of horses (20%) switched side of the asymmetry for one or more parameters between in-hand and track trials. Mixed model analyses revealed no significant effects of trial mode (in-hand or track trial, in-hand trial pre- or post-track trial, straight or oval track), trainer or horse height. Females had a significant but small reduction in asymmetry in one front limb parameter (HD_max ) compared with males (1.7 mm, 95% CI 0.18-3.28, P = .03).

MAIN LIMITATIONS

High data variability, reflected in large trial standard deviations, relating mainly to a lack of horse compliance.

CONCLUSIONS

A high proportion of Standardbred yearlings showed movement asymmetries. There was no group-level effect between in-hand and track trials, however, considerable individual variation was observed.

The Effect of Tungsten Road Nails on Upper Body Movement Asymmetry in Horses Trotting on Tarmac

Tungsten road nails are commonly used by farriers to increase grip between the hoof and the ground surface. There is limited evidence relating the use of road nails to the fundamental mechanics of movement. Grip is important for efficient deceleration on landing and subsequent propulsion, but this must be balanced against an amount of slip to divide the landing force into horizontal as well as vertical subcomponents. Here, we conducted an intervention study to quantify the effect of lateral heel road nail placement on weight bearing and propulsion in 10 horses trotting on tarmac. Wireless inertial measurement units measured vertical movement asymmetry. Differences in head and pelvic movement asymmetry before/after subsequent application of laterally placed road nails to forelimb and hindlimb hooves in a randomized order were compared to zero value (no change) with a one-sample t-test, P < .05. Left-to-right tuber coxae movement amplitude difference was significantly more negative (-3.25 mm, P = .03), suggesting more right than left tuber coxae movement amplitude, after application of a road nail to the left hindlimb. No movement asymmetries at the poll, withers, or sacrum were detected after nail placement (all P > .055). Pelvic movement indicates a very small increase in weight bearing and propulsion provided by the hindlimb with a laterally placed road nail compared to the contralateral hindlimb. Further work is needed to investigate slip- and grip-related parameters at the level of the hoof and to investigate the long-term consequences of very small changes in movement asymmetry.

Effect of induced hindlimb length difference on body-mounted inertial sensor measures used to evaluate hindlimb lameness in horses

This study has investigated the immediate effect of induced hindlimb length difference on hindlimb lameness measured as differences in minimum (Pmin) and maximum (Pmax) pelvic heights in 16 horses trotting in a straight line and lungeing on both hard and soft surfaces with body-mounted inertial sensors. Hindlimb length differences were induced by applying an Easyboot Glue-on shoe to one hindlimb. Changes in Pmin and Pmax with induced hindlimb length difference were assessed with a two-way repeated-measures ANOVA with trial (straight, lunge with inside limb elevation, lunge with outside limb elevation) and surface (hard, soft) as within-subject factors. Change in Pmin, indicating an impact-type lameness, in the hind limb with the elevation, was significant in both the straight line and while lunging on both hard and soft surfaces. Change in Pmax, indicating pushoff-type lameness, in the opposite, non-elevated hind limb, was significant when trotting in a straight line but not while lunging.

Effect of meloxicam treatment on movement asymmetry in riding horses in training

Quantitative gait analysis has revealed that a large proportion of horses in training, perceived as free from lameness by their owners, show movement asymmetries of equal magnitude to horses with mild clinical lameness. Whether these movement asymmetries are related to orthopaedic pain and/or pathology has yet to be further investigated. Therefore, the objective of this study was to determine whether movement asymmetries in riding horses in training are affected by anti-inflammatory treatment with meloxicam. In a crossover design, horses were treated with meloxicam or placebo for four days respectively, with a 14–16 day washout period between treatments. Objective movement analysis utilising body mounted accelerometers was performed on a hard and a soft surface before and on day four of each treatment. A trial mean was calculated for the differences between the two vertical displacement minima and maxima of head (HDmin, HDmax) and pelvis (PDmin, PDmax) per stride. Horses (n = 66) with trial mean asymmetries greater than 6 mm for HDmin or HDmax, or more than 3 mm for PDmin or PDmax, at baseline were included. The difference before and after each treatment in the measured movement asymmetry was assessed with linear mixed models. Treatment with meloxicam did not significantly affect the movement asymmetry in any of the models applied (all p>0.30). These results raise new questions: are the movement asymmetries in riding horses in training simply expressions of biological variation or are they related to pain/dysfunction that is non-responsive to meloxicam treatment?

Sensor-based equine gait analysis: more than meets the eye?

Quantitative gait analysis in the lame horse has gained in popularity, likely related to the potential to remove bias from the clinical decision-making process. Its implementation into clinical practice is, however, not without challenges. This review visits some of the challenges related to the use of thresholds and guideline values in the context of clinical decision making, as well as when applied to scientific studies based on relevant published studies: issues such as ‘normal day-to-day variation’, conformational asymmetry and the often limited number of parameters that are being quantified. Emphasis is put on outlining the basic underlying principles relating to head nod and hip hike, which are explained in the context of Newtonian mechanics associating reduced vertical acceleration of the upper body to reduced force production with the limb that is in contact with the ground during that time period. Further to quantifying what can be seen ‘by eye’, the review also visits phenomena such as asymmetries in weight bearing or pushoff and compensatory mechanisms, with emphasis on measurement of withers movement and thoughts about multilimb lameness. The review concludes with thoughts about additional parameters such as limb movement and movement of the thoraco-lumbo-sacral area, which may provide additional insights into lameness and poor performance but are at current less frequently included into clinical gait analysis in the horse.

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.

Vertical movement symmetry of the withers in horses with induced forelimb and hindlimb lameness at trot

Background

The main criteria for lameness assessment in horses are head movement for forelimb lameness and pelvic movement for hindlimb lameness. However, compensatory head nod in horses with primary hindlimb lameness is a well‐known phenomenon. This compensatory head nod movement can be easily misinterpreted as a sign of primary ipsilateral forelimb lameness. Therefore, discriminating compensatory asymmetries from primary directly pain‐related movement asymmetries is a prerequisite for successful lameness assessment.

Objectives

To investigate the association between head, withers and pelvis movement asymmetry in horses with induced forelimb and hindlimb lameness.

Study design

Experimental study.

Methods

In 10 clinically sound Warmblood riding horses, forelimb and hindlimb lameness were induced using a sole pressure model. The horses were then trotted on a treadmill. Three‐dimensional optical motion capture was used to collect kinematic data from reflective markers attached to the poll, withers and tubera sacrale. The magnitude and side (left or right) of the following symmetry parameters, vertical difference in minimum position, maximum position and range‐up were calculated for head, withers, and pelvis. Mixed models were used to analyse data from induced forelimb and hindlimb lameness.

Results

For each mm increase in pelvic asymmetry in response to hindlimb lameness induction, withers movement asymmetry increased by 0.35–0.55 mm, but towards the contralateral side. In induced forelimb lameness, for each mm increase in head movement asymmetry, withers movement asymmetry increased by 0.05–0.10 mm, in agreement with the head movement asymmetry direction, both indicating lameness in the induced forelimb.

Main limitations

Results must be confirmed in clinically lame horses trotting overground.

Conclusions

The vertical asymmetry pattern of the withers discriminated a head nod associated with true forelimb lameness from the compensatory head movement asymmetry caused by primary hindlimb lameness. Measuring movement symmetry of the withers may, thus, aid in determining primary lameness location.

Assessment of static posturography and pedobarography for the detection of unilateral forelimb lameness in ponies

BACKGROUND

Static posturography and pedobarography are based on the detection of postural imbalance and, consequently, the pressure redistribution between limbs in lame subjects. These techniques have proven to be useful for the detection of lameness in humans and dogs. The main objective of this study was to test the suitability of static posturography and pedobarography in diagnosing lameness in ponies. A pressure platform was used to obtain postural data (statokinesiograms, mean X and Y, length, LFS ratio, and mean velocity) from 10 sound ponies and 7 ponies with unilateral forelimb lameness. Static pedobarographic data (pressure distribution, mean pressure, and peak pressure) were also collected and compared with force plate data (peak vertical force and vertical impulse) obtained from the same animals at the walk.

RESULTS

Significant differences were seen between lame and sound ponies for almost all evaluated parameters. With this sample size, differences between lame and sound limbs/groups were detected with a statistical power of 90%, except for mean X and Y.

CONCLUSIONS

Static posturography and pedobarography provide a complementary approach for lameness detection in equids.

Influence of seating styles on head and pelvic vertical movement symmetry in horses ridden at trot

Detailed knowledge of how a rider’s seating style and riding on a circle influences the movement symmetry of the horse’s head and pelvis may aid rider and trainer in an early recognition of low grade lameness. Such knowledge is also important during both subjective and objective lameness evaluations in the ridden horse in a clinical setting. In this study, inertial sensors were used to assess how different rider seating styles may influence head and pelvic movement symmetry in horses trotting in a straight line and on the circle in both directions. A total of 26 horses were subjected to 15 different conditions at trot: three unridden conditions and 12 ridden conditions where the rider performed three different seating styles (rising trot, sitting trot and two point seat). Rising trot induced systematic changes in movement symmetry of the horses. The most prominent effect was decreased pelvic rise that occurred as the rider was actively rising up in the stirrups, thus creating a downward momentum counteracting the horses push off. This mimics a push off lameness in the hindlimb that is in stance when the rider sits down in the saddle during the rising trot. On the circle, the asymmetries induced by rising trot on the correct diagonal counteracted the circle induced asymmetries, rendering the horse more symmetrical. This finding offers an explanation to the equestrian tradition of rising on the ‘correct diagonal.’ In horses with small pre-existing movement asymmetries, the asymmetry induced by rising trot, as well as the circular track, attenuated or reduced the horse’s baseline asymmetry, depending on the sitting diagonal and direction on the circle. A push off hindlimb lameness would be expected to increase when the rider sits during the lame hindlimb stance whereas an impact hindlimb lameness would be expected to decrease. These findings suggest that the rising trot may be useful for identifying the type of lameness during subjective lameness assessment of hindlimb lameness. This theory needs to be studied further in clinically lame horses.

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.

Alterations in thoracolumbosacral movement when pain causing lameness has been improved by diagnostic analgesia

Lameness, thoracolumbosacral pain and reduced range of motion (ROM) often coexist; better understanding of their relationship is needed. The objectives were to determine if thoracolumbosacral movement of horses changes when pain causing lameness is improved by diagnostic analgesia. We hypothesised that reduction of lameness will increase ROM of the thoracolumbosacral region. Thirteen horses with different types of hind limb lameness were trotted in straight lines and lunged on a 10m diameter circle on left and right reins before and after lameness was subjectively substantially improved by diagnostic analgesia. Inertial sensor data were collected from the withers, thirteenth (T13) and eighteenth thoracic (T18) vertebrae, third lumbar (L3) vertebra, tubera sacrale (TS), left and right tubera coxae. ROM of flexion-extension, axial rotation, lateral bending, dorsoventral, lateral-lateral motion and vertical movement symmetry were quantified at each thoracolumbar site. Hiphike difference (HHD), maximum difference (MaxDiff) and minimum difference (MinDiff) for the pelvic sensors were measured. Percentage changes for before and after diagnostic analgesia were calculated; mean±standard deviation (SD) or median [interquartile range] were determined. Associations between the change in pelvic versus thoracolumbar movement symmetry after each local analgesic technique were tested. After resolution of lameness, HHD decreased by 7% [68%] (P=0.006). The MinDiff decreased significantly by 33% [61%] (P=0.01), 45±13% (P=0.005) and 52±23% (P=0.04), for TS, L3 and T18, respectively. There was significantly increased ROM in flexion-extension at T13, in axial rotation at T13, T18, L3 and in lateral-lateral ROM at L3. Thoracolumbosacral asymmetry and reduced ROM associated with lameness were both altered immediately by improvement in lameness using diagnostic analgesia.

Head and pelvic movement asymmetries at trot in riding horses in training and perceived as free from lameness by the owner

Recent studies evaluating horses in training and considered free from lameness by their owners have identified a large proportion of horses with motion asymmetries. However the prevalence, type and magnitude of asymmetries when trotting in a straight line or on the lunge have not been investigated. The aim of this study was to objectively investigate the presence of motion asymmetries in riding horses in training by identifying the side and quantifying the degree and type (impact, pushoff) of forelimb and hind limb asymmetries found during straight line trot and on the lunge. In a cross-sectional study, vertical head and pelvic movement symmetry was measured in 222 Warmblood type riding horses, all without perceived performance issues and considered free from lameness by their owners. Body-mounted uni-axial accelerometers were used and differences between maximum and minimum head (HDmax, HDmin) and pelvic (PDmax, PDmin) vertical displacement between left and right forelimb and hind limb stances were calculated during straight line trot and on the lunge. Previously reported symmetry thresholds were used. The thresholds for symmetry were exceeded in 161 horses for at least one variable while trotting in a straight line, HDmin (n = 58, mean 14.3 mm, SD 7.1), HDmax (n = 41, mean 12.7 mm, SD 5.5), PDmax (n = 87, mean 6.5 mm, SD 3.10), PDmin (n = 79, mean 5.7 mm, SD 2.1). Contralateral and ipsilateral concurrent forelimb and hind limb asymmetries were detected in 41 and 49 horses, respectively. There was a linear association between the straight line PDmin values and the values on the lunge with the lame limb to the inside of the circle. A large proportion (72.5%) of horses in training which were perceived as free from lameness by their owner showed movement asymmetries above previously reported asymmetry thresholds during straight line trot. It is not known to what extent these asymmetries are related to pain or to mechanical abnormalities. Therefore, one of the most important questions that must be addressed is how objective asymmetry scores can be translated into pain, orthopedic abnormality, or any type of unsoundness.

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.

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.

Movement asymmetry in working polo horses

REASONS FOR PERFORMING STUDY

The high, repetitive demands imposed on polo horses in training and competition may predispose them to musculoskeletal injuries and lameness.

OBJECTIVES

To quantify movement symmetry and lameness in a population of polo horses, and to investigate the existence of a relationship with age.

STUDY DESIGN

Convenience sampled cross-sectional study.

METHODS

Sixty polo horses were equipped with inertial measurement units (IMUs) attached to the poll, and between the tubera sacrale. Six movement symmetry measures were calculated for vertical head and pelvic displacement during in-hand trot and compared with values for perfect symmetry, compared between left and right limb lame horses, and compared with published thresholds for lameness. Regression lines were calculated as a function of age of horse.

RESULTS

Based on 2 different sets of published asymmetry thresholds 52-53% of the horses were quantified with head movement asymmetry and 27-50% with pelvic movement asymmetry resulting in 60-67% of horses being classified with movement asymmetry outside published guideline values for either the forelimbs, hindlimbs or both. Neither forelimb nor hindlimb asymmetries were preferentially left or right sided, with directional asymmetry values across all horses not different from perfect symmetry and absolute values not different between left and right lame horses (P values >0.6 for all forelimb symmetry measures and >0.2 for all hindlimb symmetry measures). None of the symmetry parameters increased or decreased significantly with age.

CONCLUSIONS

A large proportion of polo horses show gait asymmetries consistent with previously defined thresholds for lameness. These do not appear to be lateralised or associated with age.

Head and pelvic movement asymmetry during lungeing in horses with symmetrical movement on the straight

Reasons for performing study

Lungeing is commonly used as part of standard lameness examinations in horses. Knowledge of how lungeing influences motion symmetry in sound horses is needed.

Objectives

The aim of this study was to objectively evaluate the symmetry of vertical head and pelvic motion during lungeing in a large number of horses with symmetric motion during straight line evaluation.

Study design

Cross‐sectional prospective study.

Methods

A pool of 201 riding horses, all functioning well and considered sound by their owners, were evaluated in trot on a straight line and during lungeing to the left and right. From this pool, horses with symmetric vertical head and pelvic movement during the straight line trot (n = 94) were retained for analysis. Vertical head and pelvic movements were measured with body mounted uniaxial accelerometers. Differences between vertical maximum and minimum head (HDmax, HDmin) and pelvic (PDmax, PDmin) heights between left and right forelimb and hindlimb stances were compared between straight line trot and lungeing in either direction.

Results

Vertical head and pelvic movements during lungeing were more asymmetric than during trot on a straight line. Common asymmetric patterns seen in the head were more upward movement during push‐off of the outside forelimb and less downward movement during impact of the inside limb. Common asymmetric patterns seen in the pelvis were less upward movement during push‐off of the outside hindlimb and less downward movement of the pelvis during impact of the inside hindlimb. Asymmetric patterns in one lunge direction were frequently not the same as in the opposite direction.

Conclusions

Lungeing induces systematic asymmetries in vertical head and pelvic motion patterns in horses that may not be the same in both directions. These asymmetries may mask or mimic fore‐ or hindlimb lameness.

Rater agreement of visual lameness assessment in horses during lungeing

REASONS FOR PERFORMING STUDY

Lungeing is an important part of lameness examinations as the circular path may accentuate low-grade lameness. Movement asymmetries related to the circular path, to compensatory movements and to pain make the lameness evaluation complex. Scientific studies have shown high inter-rater variation when assessing lameness during straight line movement.

OBJECTIVES

The aim was to estimate inter- and intra-rater agreement of equine veterinarians evaluating lameness from videos of sound and lame horses during lungeing and to investigate the influence of veterinarians' experience and the objective degree of movement asymmetry on rater agreement.

STUDY DESIGN

Cross-sectional observational study.

METHODS

Video recordings and quantitative gait analysis with inertial sensors were performed in 23 riding horses of various breeds. The horses were examined at trot on a straight line and during lungeing on soft or hard surfaces in both directions. One video sequence was recorded per condition and the horses were classified as forelimb lame, hindlimb lame or sound from objective straight line symmetry measurements. Equine veterinarians (n = 86), including 43 with >5 years of orthopaedic experience, participated in a web-based survey and were asked to identify the lamest limb on 60 videos, including 10 repeats. The agreements between (inter-rater) and within (intra-rater) veterinarians were analysed with κ statistics (Fleiss, Cohen).

RESULTS

Inter-rater agreement κ was 0.31 (0.38/0.25 for experienced/less experienced) and higher for forelimb (0.33) than for hindlimb lameness (0.11) or soundness (0.08) evaluation. Median intra-rater agreement κ was 0.57.

CONCLUSIONS

Inter-rater agreement was poor for less experienced raters, and for all raters when evaluating hindlimb lameness. Since identification of the lame limb/limbs is a prerequisite for successful diagnosis, treatment and recovery, the high inter-rater variation when evaluating lameness on the lunge is likely to influence the accuracy and repeatability of lameness examinations and, indirectly, the efficacy of treatment.

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.

Estimation of vertical tuber coxae movement in the horse from a single inertial measurement unit

Pelvic movement is altered in hind limb lame horses. A simple method using one inertial measurement unit (IMU) attached to the sacrum, which objectively measures 'hip hike', will help detecting hind limb lameness in large scale studies. In this study, IMUs over the sacrum and the left and right tuber coxae (TC) quantified vertical movement symmetry (MS) in 10 clinically lame horses. A simple geometrical model was used to estimate TC movement from the sacrum IMU. The differences between measured and estimated MS values (mean±SD) and MS changes during different exercise conditions (straight, circle, flexion) were quantified using established MS parameters to assess the performance of the sacral IMU for estimating TC movement. Mean differences between measured and estimated MS values were variable between horses and ranged from 5 to 30 mm, SD of differences ranged from 7 to 14 mm. However, the difference between measured and estimated change in MS induced by lungeing or flexion test, was lower, with a value <1 mm for one MS measure, which assesses differences between left and right TC movement. Estimating TC movement from sacral movement does not accurately quantify the true state of TC MS since limits of agreement (LoA) overlap the decision boundaries for detecting mild lameness. The LoA of changes in vertical TC movement between exercises compared favourably with the average changes between exercise conditions. While in moderate to severe cases, changes in TC movement may be estimated from a single sensor over the sacrum, in mildly lame horses it should be measured with additional sensors.