An inertial sensor-based system can objectively assess diagnostic anaesthesia of the equine foot

Objective movement asymmetry in horses is comparable between markerless technology and sensor-based systems

BACKGROUND

A markerless artificial intelligence (AI) system for lameness detection has recently become available but has not been extensively compared with commonly used inertial measurement unit (IMU) systems for detecting asymmetry under field conditions.

OBJECTIVE

Comparison of classification of asymmetric limbs under field conditions and comparison of normalised asymmetry data using a markerless AI system (SleipAI; recorded on a tripod mounted iPhone 14pro [SL]); the Equinosis Q Lameness Locator (LL); the EquiMoves (EM); and subjective evaluation (SE).

STUDY DESIGN

Descriptive clinical study.

METHODS

Straight line trot data were collected from 52 client-owned horses in regular training. Limbs were categorised as symmetric or asymmetric. Number of analysed strides were compared with Wilcoxon's each pairs test. Inter-rater reliability in classification of asymmetric limbs was assessed with Light's Kappa. Bland Altman analysis of normalised asymmetry data was performed.

RESULTS

Data from 41 horses were included. Most horses showed mild asymmetry. The EM analysed significantly more strides than the other systems, both for forelimbs and for hindlimbs (53 ± 11 strides for both, respectively; p < 0.006). The LL analysed significantly more hindlimbs strides (45 ± 13) than the SL (27 ± 6; p < 0.001). Moderate inter-rater agreement for asymmetry classification was found between systems (k = 0.59 forelimbs; 0.44 hindlimbs); agreement decreased when including the SE. For the normalised asymmetry data, the strongest agreement was found between the two IMU systems.

MAIN LIMITATIONS

Horses were assessed during straight-line trot only.

CONCLUSIONS

The objective systems were comparable in classification of asymmetric limbs under field conditions when using defined asymmetry thresholds. Discrepancies stemmed largely from the imposed thresholds (i.e., systems largely identified same-side asymmetry). Overall, the strongest agreement was found between LL and EM. The SL analysed significantly fewer hindlimb strides than the LL and EM which could represent a limitation of the Sleip AI.

Changes in Head and Pelvic Movement Symmetry after Diagnostic Anaesthesia: Interactions between Subjective Judgement Categories and Commonly Applied Blocks

Limited evidence is available relating gait changes to diagnostic anaesthesia. We investigated associations between specific movement patterns and diagnostic anaesthesia of different anatomical structures in a retrospective analysis. Referral-level lameness cases were included with the following criteria: presence of diagnostic anaesthesia of a forelimb and/or hind limb; subjective efficacy classified as "negative", "partially positive", or "positive"; quantitative gait data available from inertial measurement units. Gait changes were calculated for three forelimb (palmar digital, abaxial sesamoid, low 4-point nerve block) and five hind limb diagnostic blocks (tarso-metatarsal, metatarsophalangeal joint block, deep branch of lateral plantar, low 6-point, abaxial sesamoid nerve block). Mixed models (random factor "case", fixed factors "diagnostic anaesthesia type" and "efficacy", two-way interaction) assessed the head and pelvic movement (p < 0.05, Bonferroni correction). Four parameters were significantly affected by forelimb anaesthesia (N = 265) (all p ≤ 0.031) and six by hind limb anaesthesia (N = 342) efficacy (all p ≤ 0.001). All head movement parameters and pelvic push-off asymmetry were significantly affected by the two-way interaction after forelimb anaesthesia (all p ≤ 0.023) and two pelvic movement symmetry parameters by the two-way interaction after hind limb anaesthesia (all p ≤ 0.020). There are interactions between block efficacy and type resulting in changes in weight-bearing and push-off-associated head and pelvic movement symmetry after diagnostic anaesthesia.

Prevalence and clinical significance of increasing head height asymmetry as a measure of forelimb lameness in horses when trotting in a straight line after palmar digital nerve block

BACKGROUND

Some horses increase in forelimb lameness, measured as vertical head height asymmetry, or differences in maximums and minimums of head heights (HDmax, HDmin), after a palmar digital nerve (PDN) block. The prevalence of this finding, or what it means clinically, has not been reported in peer-reviewed literature.

OBJECTIVES

To estimate the prevalence of increasing head height asymmetry after a PDN block and determine if this is associated with cause of forelimb lameness.

STUDY DESIGN

Retrospective case series.

METHODS

Head height asymmetry, normalised to expected vertical head displacement, from inertial-sensor data collections of all horses evaluated for forelimb lameness while trotting in a straight line at two different clinics were screened for cases that had an initial PDN block and then another more proximal block in the same limb during the same lameness evaluation. Medical records of the screened cases (n = 213) were evaluated to determine the cause of lameness. Prevalence of increasing head height asymmetry was calculated. Differences in lameness amplitude between groups of cases that remained unchanged (Group 1), that increased (Group 2), and that decreased (Group 3) in head height asymmetry before and after the initial PDN block were compared (Kruskal-Wallis). Determination of the location of the cause of lameness and final diagnoses of cases were compared between Group 1 and Group 2 (chi-squared tests of independence).

RESULTS

The PDN block increased head height asymmetry at a prevalence of 32.5% (95% CI = 24.5%-41.5%) and 13.8% (95% CI = 7.3%-22.9%), in clinic 1 and 2, respectively. Increasing head height asymmetry after an initial PDN block did not predict localization of the cause of forelimb lameness or specific diagnosis (p = 0.1), other than indicating that it is unlikely to be in the foot (p = 0.02).

MAIN LIMITATIONS

Study samples consisted primarily of Warmbloods (clinic 1) and Quarter Horses (clinic 2). Analysis of blocking induced changes was limited to straight line trot only.

CONCLUSIONS

Increasing head height asymmetry after PDN block is common during forelimb lameness evaluations. Other than indicating that the cause of lameness is more proximal in the blocked forelimb, this does not help determine the final diagnosis.

Objective evaluation for analgesia of the distal interphalangeal joint, the navicular bursa and perineural analgesia in horses with naturally occurring forelimb lameness localised to the foot

BACKGROUND

The outcome and interpretation of intra-synovial diagnostic analgesia of the distal interphalangeal joint (DIPJ) and the navicular bursa (NB) remain in dispute, and no objective studies have been carried out to establish the percentage of improvement over time from these two analgesia techniques.

OBJECTIVES

To investigate the qualitative and time-dependent outcome of DIPJ-A and NB-A in naturally occurring forelimb lameness.

STUDY DESIGN

Case series.

METHODS

Twenty-three clinical cases with forelimb lameness were evaluated objectively using a body mounted inertial sensor system (BMIS). Lameness was localised to the foot with a palmar digital nerve block and/or an abaxial sesamoidean nerve block on day 1, and analgesia of the DIPJ (DIPJ-A) and NB (NB-A) were performed on days 2 and 3. Improvement following perineural analgesia was measured after 10 min and intra-synovial blocks after 2-, 5- and 10-min. Horses with at least 70% improvement measured objectively after diagnostic analgesia were included in the study.

RESULTS

There was no significant association between improvement following perineural analgesia and the DIPJ-A and NB-A. The mean improvement in the lameness differed between DIPJ-A and NB-A at 2 min (p < 0.001) and at 5 min (p = 0.04), and it was no longer observed after 10 min (p = 0.06). A positive NB-A produced a high degree of improvement that remained stable, whereas the DIPJ-A improved over time.

MAIN LIMITATIONS

Perineural and intra-synovial analgesia were performed without contrast medium to assess the diffusion of mepivacaine.

CONCLUSIONS

Our results suggest that perineural analgesia is not reliable enough to differentiate pain originating from DIPJ and NB. Early evaluation of the DIPJ-A and NB-A can determine the origin of the pain. An improvement following NB-A was constant over time, but an improvement following DIPJ-A varied by up to 10 min.

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.

Accelerometry-Based Step Count Validation for Horse Movement Analysis During Stall Confinement

Quantitative tracking of equine movement during stall confinement has the potential to detect subtle changes in mobility due to injury. These changes may warn of potential complications, providing vital information to direct rehabilitation protocols. Inertial measurement units (IMUs) are readily available and easily attached to a limb or surcingle to objectively record step count in horses. The objectives of this study were: (1) to compare IMU-based step counts to a visually-based criterion measure (video) for three different types of movements in a stall environment, and (2) to compare three different sensor positions to determine the ideal location on the horse to assess movement. An IMU was attached at the withers, right forelimb and hindlimb of six horses to assess free-movement, circles, and figure-eights recorded in 5 min intervals and to determine the best location, through analysis of all three axes of the triaxial accelerometer, for step count during stall confinement. Mean step count difference, absolute error (%) and intraclass correlation coefficients (ICCs) were determined to assess the sensor's ability to track steps compared to the criterion measure. When comparing sensor location for all movement conditions, the right-forelimb vertical-axis produced the best results (ICC = 1.0, % error = 6.8, mean step count difference = 1.3) followed closely by the right-hindlimb (ICC = 0.999, % error = 15.2, mean step count difference = 1.8). Limitations included the small number of horse participants and the lack of random selection due to limited availability and accessibility. Overall, the findings demonstrate excellent levels of agreement between the IMU's vertical axis and the video-based criterion at the forelimb and hindlimb locations for all movement conditions.

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.

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.

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.

Comparison of analgesic and tissue effects of subcutaneous perineural injection of liposomal bupivacaine and bupivacaine hydrochloride in horses with forelimb lameness induced via circumferential clamp

OBJECTIVE

To evaluate the analgesic and tissue effects of liposomal bupivacaine administered SC as an abaxial sesamoid nerve block in horses with experimentally induced lameness.

ANIMALS

6 healthy mature light-breed horses.

PROCEDURES

In a randomized crossover study, a circumferential hoof clamp was applied to a forelimb to induce reversible lameness. An abaxial sesamoid nerve block of the lame forelimb was performed by SC perineural injection of 10 mg of liposomal bupivacaine or bupivacaine HCl/site. Quantitative gait data were objectively obtained with a body-mounted inertial sensor system before (baseline) and at 30-minute intervals after treatment. Time to return to 85% of baseline lameness was determined. After a minimum 4-day washout period, procedures were repeated with the alternate limb and treatment. Lastly, the palmar digital nerves and perineural tissues were collected and examined histologically.

RESULTS

SC perineural injection of liposomal bupivacaine ameliorated forelimb lameness in 5 of 6 horses. The median duration of analgesia was not significantly different between liposomal bupivacaine (4.5 hours) and bupivacaine HCl (3.0 hours). Histologically, mild inflammation was noted in 3 of 10 sites injected with liposomal bupivacaine and in none of the sites injected with bupivacaine HCl.

CONCLUSIONS AND CLINICAL RELEVANCE

SC perineural injection of 10 mg of liposomal bupivacaine/site ameliorated experimentally induced forelimb lameness in some horses. At milligram-equivalent doses, liposomal bupivacaine had a similar duration of analgesia to that of bupivacaine HCl. Further investigation is required before recommending clinical use of liposomal bupivacaine for nerve blocks in horses.

Agreement among equine veterinarians and between equine veterinarians and inertial sensor system during clinical examination of hindlimb lameness in horses

BACKGROUND

Hindlimb lameness evaluation is known to be challenging. Experience is essential for the ability of equine veterinarians to detect lameness. Nevertheless, even an experienced veterinarian is still subject to bias. Objective lameness detecting methods have been established to aid veterinarians.

OBJECTIVES

1) To estimate the effect of experience on the interobserver agreement and the agreement between a body-mounted inertial sensor system (BMISS) and veterinarians on detecting hindlimb lameness, and 2) to estimate the agreement between the BMISS and highly experienced veterinarians on change in lameness after diagnostic analgesia.

STUDY DESIGN

Cross-sectional study.

METHODS

Twenty-six horses with hindlimb lameness were evaluated in clinical conditions by clinicians and simultaneously measured by the BMISS. Videos of their lameness examination were recorded and shown to 13 veterinarians from three groups of varying experience for evaluation. The interobserver agreement and the agreement between veterinarians and the BMISS were calculated.

RESULTS

Interobserver agreement from all three groups was recorded as 'fair'. The strength of agreement between veterinarians and BMISS was 'fair' for the highly experienced group, 'slight to fair' for the moderately experienced group and 'slight' in the inexperienced group. The BMISS and the highly experienced veterinarians declared a 'strong' agreement in assigning an improvement in lameness after diagnostic analgesia.

MAIN LIMITATIONS

Lameness evaluation through video viewing might be more challenging for some evaluators than live situations.

CONCLUSIONS

Given the task of evaluating videos of horses trotting in a straight line, the more experienced veterinarians did not show more reliability than those with less experience. Due to 1) the moderate agreement between the BMISS and clinicians (highly experienced and moderately experienced) in the live clinical evaluation in determining hindlimb lameness, and 2) the strong association between the BMISS and highly experienced veterinarians in determining improvement of lameness after anaesthesia, therefore the use of the BMISS as a supporting tool for veterinarians is encouraged.

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.

Objective assessment of the compensatory effect of clinical hind limb lameness in horses: 37 cases (2011-2014)

OBJECTIVE To characterize and describe the compensatory load redistribution that results from unilateral hind limb lameness in horses. DESIGN Retrospective case series. ANIMALS 37 client-owned horses. PROCEDURES Medical records were reviewed to identify horses with unilateral hind limb lameness that responded positively (by objective assessment) to diagnostic local anesthesia during lameness evaluation and that were evaluated before and after diagnostic local anesthesia with an inertial sensor-based lameness diagnosis system. Horses were grouped as having hind limb lameness only, hind limb and ipsilateral forelimb lameness, or hind limb and contralateral forelimb lameness. Measures of head and pelvic movement asymmetry before (baseline) and after diagnostic local anesthesia were compared. The effect of group on baseline pelvic movement asymmetry variables was analyzed statistically. RESULTS Maximum pelvic height significantly decreased from the baseline value after diagnostic local anesthesia in each of the 3 lameness groups and in all horses combined. Minimum pelvic height significantly decreased after the procedure in all groups except the hind limb and contralateral forelimb lameness group. Head movement asymmetry was significantly decreased after diagnostic local anesthesia for horses with hind limb and ipsilateral forelimb lameness and for all horses combined, but not for those with hind limb lameness only or those with hind limb and contralateral forelimb lameness. CONCLUSIONS AND CLINICAL RELEVANCE Results supported that hind limb lameness can cause compensatory load redistribution evidenced as ipsilateral forelimb lameness. In this population of horses, contralateral forelimb lameness was not compensatory and likely reflected true lameness. Further studies are needed to investigate the source of the contralateral forelimb lameness in such 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.

Naturally-occurring forelimb lameness in the horse results in significant compensatory load redistribution during trotting

This study aimed to quantify the compensatory response to naturally-occurring forelimb lameness on load redistribution. Data from lameness investigations using an inertial sensor based system to monitor the response to forelimb diagnostic anaesthesia were reviewed. Horses with primary forelimb lameness were grouped for analysis as (1) all horses combined (n= 28), (2) forelimb-only lameness (n= 8/28), (3) forelimb-contralateral hindlimb lameness (n= 14/28), (4) forelimb-ipsilateral hindlimb lameness (n= 6/28). The effect of diagnostic anaesthesia on measures of head and pelvic movement asymmetry was determined using the Wilcoxon signed rank test. Spearman's correlation analysis was performed between forelimb and hindlimb variables. Statistical significance was set at P< 0.05. Forelimb diagnostic anaesthesia resulted in a decrease in pelvic movement asymmetry among all horses and the forelimb-only and forelimb-contralateral hindlimb lameness groups. Pelvic movement asymmetry associated with the contralateral hindlimb decreased by a median of 38% (interquartile range [IQR] 10-65%), 43% (IQR 28-60%) and 28% (IQR 12-67%) in all horses, forelimb-only and forelimb-contralateral hindlimb groups respectively (P< 0.05). Maximum pelvic height difference (PDMax) significantly decreased in all horses combined and the forelimb-contralateral hindlimb lameness group by a median of 66% (IQR 24-100%) and 78% (IQR 27-100%, P< 0.01), respectively. Change in head movement asymmetry and vector sum was significantly positively correlated with PDMax in all horses combined and the forelimb-contralateral hindlimb group (P< 0.05). Forelimb lameness had a significant effect on hindlimb and pelvic movement in horses with clinical lameness resulting in compensatory load redistribution and decreased push-off from the contralateral hindlimb.