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

Adaptation strategies of Icelandic horses with induced transient hindlimb lameness at walk, trot and tölt

BACKGROUND

Icelandic horses are valued for their additional gaits, but assessing lameness in this breed can be challenging. Pelvic (P) vertical movement asymmetries, differences (D) in minimum (min)/maximum (max) position, are used to quantify impact (PDmin) and push-off (PDmax) hindlimb lameness during the trot, but no established parameters exist for detecting hindlimb lameness in other gaits.

OBJECTIVE

To evaluate temporal stride parameters and upper-body movement asymmetry after transient hindlimb lameness induction in walk, trot and tölt.

STUDY DESIGN

In vivo experiment.

METHODS

Eleven Icelandic horses were measured before and after hindlimb lameness was induced (sole pressure). Vertical movement asymmetry of Head (H)/Pelvis (HDmin/HDmax/PDmin/PDmax) and hip-hike were measured during ridden walk, sitting trot and tölt as well as in-hand walk and trot, using an inertial measurement unit system. Linear mixed models compared sound and lame conditions within each gait, and differences in estimated marginal means (mm) between conditions are presented, with significance set at p < 0.05.

RESULTS

Lameness induction significantly increased PDmin asymmetry in all gaits except walk in-hand: walk (PDminridden: 5.07), trot (PDminhand: 10.72, PDminridden: 9.85) and tölt (PDminridden: 4.88). However, PDmax increased only for trot in-hand (PDmaxhand: 4.80). Hip-hike increased on the lame limb side at trot (hip-hikehand: 20.90, hip-hikeridden: 10.81) and tölt (hip-hikeridden: 4.28).

MAIN LIMITATIONS

Findings need verification in clinically lame Icelandic horses with varying diagnoses and lameness severity.

CONCLUSION

PDmin and hip-hike appear to be effective parameters for detecting mild hoof-associated hindlimb lameness in Icelandic horses when trotting in-hand or ridden. At walk or tölt under saddle, only slight PDmin changes were observed, likely due to lower limb loading in those gaits and the pelvic minimum position associating with different loading stages throughout the stride cycle for walking and running gaits. These findings suggest trot is the preferred gait for assessing mild hindlimb lameness in Icelandic horses.

Kinematic changes in dairy cows with induced, unilateral forelimb lameness during straight line walk

Early detection of lameness in dairy herds is essential to enable timely treatment of affected animals, thereby avoiding unnecessary costs and animal suffering. Since claw diseases most commonly affect the hind claws, specific kinematic changes in cows with forelimb lameness have not been investigated. However, in-depth knowledge on movement pattern alterations occurring during lameness of varying sources is essential to develop efficient lameness detection tools. In this study, 27 gait analysis trials consisting of > 2 000 strides were collected from 12 clinically sound dairy cows. The cows were equipped with nine body-mounted inertial measurement units (IMUs) and contributed with one baseline trial and one or two lameness trials each. A lameness induction method causing increased claw pressure was used to introduce mild, reversible, unilateral forelimb lameness. From the IMU data, 31 limb-and upper body movement parameters, mainly focusing on motion symmetry, were computed for each stride. Baseline and lameness data were compared in linear mixed models, where between-cow variability was accounted for. Twenty-two movement parameters differed between the two conditions (P ≤ 0.05). Forelimb lameness caused a more pace-like walk; the relative time between hoof-on of both hindlimbs and their respective ipsilateral forelimb decreased by 0.022 and 0.036 (ratio of stride duration), while the relative time between hoof-on of the hindlimb contralateral to the lame forelimb, and the lame forelimb increased by 0.050. The maximum protraction angle of the lame forelimb increased by 1.5°, while the protraction angle of the non-lame forelimb, and the retraction angle of the lame forelimb, decreased by 1.7° and 3.0°. All hindlimb protraction and retraction angles, except the protraction angle of the hindlimb contralateral to the lame forelimb, decreased by 1.2°-1.4°. Following signal decomposition of upper body vertical motion, the largest changes were detected for the head and neck; there were notable increases (0.13 and 0.11) of their first harmonic (asymmetric component) amplitudes, and decreases (0.10 and 0.050) of their second harmonic (symmetric component) amplitudes (relative to the range of motion). Changes in the within-stride differences in the withers' position during limb spread and midstance (respectively) were also detected. The vertical range of motion per stride increased for the head, neck, and back, but decreased for the pelvis. Although the investigated parameters hence show promise as lameness indicators, the movement changes occurring with the induced fore claw pain should be confirmed in clinical lameness cases, to ensure usability of the described pattern for early, automated forelimb lameness detection.

Conference report from the abstracts of the canine section at The 9th International Conference on Canine and Equine Locomotion, Utrecht 2023

This conference report summarises the abstracts on canine locomotion research presented in The 9th International Conference on Canine and Equine Locomotion, discusses the most relevant literature in relation to the topics presented in the meeting and highlights the importance of canine locomotion in veterinary medicine.

Discrimination of the Lame Limb in Horses Using a Machine Learning Method (Support Vector Machine) Based on Asymmetry Indices Measured by the EQUISYM System

Lameness detection in horses is a critical challenge in equine veterinary practice, particularly when symptoms are mild. This study aimed to develop a predictive system using a support vector machine (SVM) to identify the affected limb in horses trotting in a straight line. The system analyzed data from inertial measurement units (IMUs) placed on the horse's head, withers, and pelvis, using variables such as vertical displacement and retraction angles. A total of 287 horses were included, with 256 showing single-limb lameness and 31 classified as sound. The model achieved an overall accuracy of 86%, with the highest success rates in identifying right and left forelimb lameness. However, there were challenges in identifying sound horses, with a 54.8% accuracy rate, and misclassification between forelimb and hindlimb lameness occurred in some cases. The study highlighted the importance of specific variables, such as vertical head and withers displacement, for accurate classification. Future research should focus on refining the model, exploring deep learning methods, and reducing the number of sensors required, with the goal of integrating these systems into equestrian equipment for early detection of locomotor issues.

The Challenge of Defining Laterality in Horses: Is It Laterality or Just Asymmetry?

The defining characteristic of laterality is the dominance of one side of the brain controlling specific functions of paired organs or on one side of the body. Structural and functional asymmetries are ubiquitous in horses and range from anatomical features (e.g., the length of long bones) to the gathering of sensory information (e.g., which eye is used to observe unfamiliar scenes) and motor functions (e.g., left-right differences in locomotion). There is a common tendency to assign observed structural or functional asymmetries to lateralization, which often involves more than a simple left-right difference in observed behavior. This narrative review explores the concept of laterality relative to the structural and functional asymmetries reported in horses. Inconsistent and poorly defined terminology, a widely disparate methodology, and a lack of standardized thresholds make it difficult to assess the presence or degree of laterality. Within this context, there seems to be limited evidence of laterality in horses and much more prevalent and stronger support for structural and functional asymmetries due to a wide range of well-established behavioral, nociceptive, and biomechanical mechanisms. The authors caution against generalizing the idea that all observed structural or functional asymmetries in horses are due to laterality.

Quantifying head and withers movement asymmetry in sound and naturally forelimb lame horses trotting on a circle on hard and soft surfaces

BACKGROUND

Reliable lameness thresholds for vertical head displacement for trotting on a circular path and on different surfaces have yet to be defined. Withers movement in lame horses could help improve the diagnostic accuracy of sensor technology.

OBJECTIVES

To define head movement lameness threshold ranges and describe the relationship between head and withers movement during trotting under different circumstances in sound and forelimb lame horses.

STUDY DESIGN

Retrospective analysis of clinical data and comparison with control group.

METHODS

Fifty-five sound and thirty-four naturally lame horses were trotted under field conditions on a hard surface on a straight line and on both directions on soft and hard surfaces. Movement asymmetry was analysed by measuring differences in displacement minima for head and withers using an inertial measurement unit sensor-based gait analysis system. Receiver operating characteristic (ROC) analysis was performed to define threshold ranges. Relationships between head and withers data were identified by calculating the correlation with linear regression analysis.

RESULTS

Estimated lameness threshold values for vertical head movement asymmetry ranged from 11.5 to 12.5 mm. On both surfaces, a head movement asymmetry threshold range from 24.5 to 26.5 mm could be found for the circle. Lame horses showed significant correlations between head and withers movement on hard ground straight line (R2 0.714, p < 0.001) and inner leg lame horses on the lunge (R2 0.915, p < 0.001).

MAIN LIMITATIONS

Different sources of lameness were not distinguished. Radius and speed during lungeing could not be perfectly controlled. Inclusion in the sound group was based on a subjective examination by one clinician and in the lame group two clinicians subjectively determined inner and outer leg lameness creating an extra amount of uncertainty.

CONCLUSIONS

Lameness thresholds for quantifying head movement asymmetry on the lunge were proposed. A significant correlation was observed between head and withers movement asymmetry under several conditions.

Kinematic changes in dairy cows with induced hindlimb lameness: transferring methodology from the field of equine biomechanics

Lameness is a common issue on dairy farms, with serious implications for economy and animal welfare. Affected animals may be overlooked until their condition becomes severe. Thus, improved lameness detection methods are needed. In this study, we describe kinematic changes in dairy cows with induced, mild to moderate hindlimb lameness in detail using a "whole-body approach". Thereby, we aimed to identify explicable features to discriminate between lame and non-lame animals for use in future automated surveillance systems. For this purpose, we induced a mild to moderate and fully reversible hindlimb lameness in 16 dairy cows. We obtained 41 straight-line walk measurements (containing > 3 000 stride cycles) using 11 inertial measurement units attached to predefined locations on the cows' upper body and limbs. One baseline and ≥ 1 induction measurement(s) were obtained from each cow. Thirty-one spatial and temporal parameters related to limb movement and inter-limb coordination, upper body vertical displacement symmetry and range of motion (ROMz), as well as pelvic pitch and roll, were calculated on a stride-by-stride basis. For upper body locations, vertical within-stride movement asymmetry was investigated both by calculating within-stride differences between local extrema, and by a signal decomposition approach. For each parameter, the baseline condition was compared with induction condition in linear mixed-effect models, while accounting for stride duration. Significant difference between baseline and induction condition was seen for 23 out of 31 kinematic parameters. Lameness induction was associated with decreased maximum protraction (-5.8%) and retraction (-3.7%) angles of the distal portion of the induced/non-induced limb respectively. Diagonal and lateral dissociation of foot placement (ratio of stride duration) involving the non-induced limb decreased by 8.8 and 4.4%, while diagonal dissociation involving the induced limb increased by 7.7%. Increased within-stride vertical displacement asymmetry of the poll, neck, withers, thoracolumbar junction (back) and tubera sacrale (TS) were seen. This was most notable for the back and poll, where a 40 and 24% increase of the first harmonic amplitude (asymmetric component) and 27 and 14% decrease of the second harmonic amplitude (symmetric component) of vertical displacement were seen. ROMz increased in all these landmarks except for TS. Changes in pelvic roll main components, but not in the range of motion of either pitch or roll angle per stride, were seen. Thus, we identified several kinematic features which may be used in future surveillance systems. Further studies are needed to determine their usefulness in realistic conditions, and to implement methods on farms.

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

BACKGROUND AND OBJECTIVE

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

STUDY DESIGN

In vivo experiment.

METHODS

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

RESULTS

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

MAIN LIMITATIONS

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

CONCLUSIONS

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

Pilot study of locomotor asymmetry in horses walking in circles with and without a rider

Background

Horses commonly show asymmetries that manifest as left (L)-right (R) differences in vertical excursion of axial body segments. Moving on a circle confounds inherent individual asymmetries. Our goals were to evaluate individual and group asymmetry patterns and compare objective data with subjective impressions of side preference/laterality in horses walking on L and R circles.

Methods

Fifteen horses walked on L and R circles unridden and ridden on long and short reins. Optical motion capture (150 Hz) tracked skin-fixed markers. Variables were trunk horizontal angle; neck-to-trunk angle; vertical range of motion (ROM) for the head, withers and sacrum; ROM for pelvic roll, pitch, and yaw; mean pelvic pitch; and ROM for hip, stifle and tarsal joints. Differences between inside and outside hind steps were determined for vertical minima and maxima of the head (HMinDiff/HMaxDiff), withers (WMinDiff/WMaxDiff) and sacrum (PMinDiff/PMaxDiff). Subjective laterality was provided by owners. Data analysis used mixed models, first without and then with subjective laterality. Iterative k-means cluster analysis was used to associate biomechanical variables with subjective laterality.

Results

PMaxDiff, PMinDiff and WMaxDiff indicated R limb asymmetry in both directions. WMinDiff indicated L (inside) fore asymmetry for L direction but was close to zero for R direction. Hip ROM was significantly smaller for the inside limb in both directions (L inside/outside: 16.7° vs. 20.6°; R: 17.8° vs. 19.4°). Stifle ROM was significantly larger for the inside limb in both directions (L: 43.1° vs. 39.0°; R: 41.9° vs. 40.4°). Taking the general direction effect into account the R hip and L stifle had larger ROM. Adding laterality to the models (seven horses L- vs. six horses R-hollow), PMaxDiff R hind asymmetry was more obvious for L-hollow horses than for R-hollow horses. L-hollow horses had greater pelvic roll ROM moving in L vs. R direction. L-hollow horses had smaller inside and greater outside hip joint ROM in L vs. R direction. R-hollow horses had a significant difference in HMinDiff between L (0 mm) and R (-14 mm) directions, indicating less head lowering at outside forelimb midstance in R direction, and larger outside tarsal ROM in R (38.6°) vs. L (37.4°) direction (p ≤ 0.05). The variables that agreed most frequently with subjective laterality in cluster analysis were pelvic roll ROM, followed by HMinDiff and PMaxDiff.

Conclusion

Differences between horses walking in L and R directions were found both at group and individual levels, as well as evidence of associations with subjective laterality. Horses maintained more symmetric hip and stifle ROM and withers vertical motion when walking on the R circle. Findings suggest that left and right lateralised horses may not be perfect mirror images. Pelvic roll ROM emerged as a promising variable to determine laterality in walk as perceived by the rider, especially when considered together with other variables.