Response to Letter to the Editor: Do we have to redefine lameness in the era of quantitative gait analysis

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.

A Review: Development of Computer Vision-Based Lameness Detection for Dairy Cows and Discussion of the Practical Applications

The computer vision technique has been rapidly adopted in cow lameness detection research due to its noncontact characteristic and moderate price. This paper attempted to summarize the research progress of computer vision in the detection of lameness. Computer vision lameness detection systems are not popular on farms, and the accuracy and applicability still need to be improved. This paper discusses the problems and development prospects of this technique from three aspects: detection methods, verification methods and application implementation. The paper aims to provide the reader with a summary of the literature and the latest advances in the field of computer vision detection of lameness in dairy cows.

How low can we go? Influence of sample rate on equine pelvic displacement calculated from inertial sensor data

BACKGROUND

Low-cost sensor devices are often limited in terms of sample rate. Based on signal periodicity, the Nyquist theorem allows determining the minimum theoretical sample rate required to adequately capture cyclical events, such as pelvic movement in trotting horses.

OBJECTIVES

To quantify the magnitude of errors arising with reduced sample rates when capturing biological signals using the example of pelvic time-displacement series and derived minima and maxima used to quantify movement asymmetry in lame horses.

STUDY DESIGN

Data comparison.

METHODS

Root mean square (RMS) errors between the 'reference' time-displacement series, captured with a validated inertial sensor at 100 Hz sample rate, and down-sampled time-series (8 Hz to 50 Hz) are calculated. Accuracy and precision are determined for maxima and minima derived from the time-displacement series.

RESULTS

Average RMS errors are <2 mm at 50 Hz sample rate, <4 mm at 40 Hz, <7 mm between 25 and 35 Hz, and increase to up to 20 mm at 20 Hz and below. Accuracy for maxima and minima is generally below 1mm. Precision is 1 mm at 50 Hz sample rate, 3 mm at 40Hz and ≥9 mm at 20 Hz and below.

MAIN LIMITATIONS

Only sample rate, no other sensor parameters were investigated.

CONCLUSIONS

Sample rate related errors for inertial sensor derived time-displacement series of pelvic movement are <2mm at 50 Hz, a rate that many low-cost loggers, smartphones or wireless sensors can sustain hence rendering these devices valid options for quantifying parameters relevant for lameness examinations in horses.

Use of Physical Self-Experience for Teaching Lameness Evaluation: Short-Term Effects on Lameness Evaluation of Horses with Mild Forelimb Lameness by Novice Veterinary Students

Lameness evaluation (LE) is an important veterinary skill, but it can be a challenging task to teach. Acoustic and visual input in conjunction with acting are the three major learning channels for acquiring new information. Acting (e.g., physical self-experience) has not been reported as a didactic tool for LE; therefore, we investigated two physical self-experience techniques, imitation of lameness during LE instruction and head nod during LE. Undergraduate veterinary students (N = 78) who had not yet received any instructions for LE underwent standard instruction for LE, followed by instructions to head nod, instructions to imitate lameness, or neither. Students' subjective LE skills were then tested against those of senior clinicians on two horses that were either sound or mildly forelimb lame. In more than 80%, there was agreement on the presence or absence of lameness independent of instruction, and we found no significant evaluation differences between didactic strategies. Specific instructions for head nodding did not significantly influence the quality of LE, possibly because head nodding was widespread even when no specific instructions had been given. Veterinary students who had been taught to imitate lameness without instructions to head nod were consistently closest to the assessment of the senior clinicians, and in walk these students were significantly better at LE than students additionally instructed to head nod. This finding indicates that imitation of lameness, but not necessarily head nodding, may be beneficial for understanding body movement such as mild equine forelimb lameness.

Should We Agree to Disagree? An Evaluation of the Inter-Rater Reliability of Gait Quality Traits in Franches-Montagnes Stallions

Gait quality, that is, the way horses move according to functional and aesthetic principles, englobes many traits that are scored by experts during breeding competitions. The experts can score a trait on a subjective valuating (SV) scale or on a linear profiling (LP) scale representing the biological extremes of the population. However, the reliability of the appraisal of gait quality traits has not been extensively evaluated. In this study, seven breed experts appraised the walk and trot quality of 24 Franches-Montagnes stallions presented in hand on a sand track. Inter-rater reliabilities of six traits (five SV and one LP) at the walk and eight traits (five SV and three LP) at the trot were estimated with intraclass correlation coefficients (ICCs). The inter-rater reliabilities were poor (ICC < 0.50). The scale anchoring varied between experts, and the variance of scores was low. There were no systematic differences in inter-rater reliability between LP and SV traits. Future studies should determine whether the inter-rater reliabilities may be increased by a more precise definition of the scores within each trait to improve the absolute agreement between experts, by a more uniform scale anchoring between experts, and by decreasing the number of scale items. However, considering the inherent limitations of the human eye in observing high-speed movement, the use of a field-applicable kinematic measurement system may support breeding experts in the appraisal of gait quality traits in the future.

Irish Equine Industry Stakeholder Perspectives of Objective Technology for Biomechanical Analyses in the Field

Wearable sensing technologies are increasingly used in human and equine gait research to improve ecological validity of research findings. It is unclear how these tools have penetrated the equine industry or what perspectives industry stakeholders' hold in relation to these relatively new devices. Semi-structured interviews were conducted with Irish equine industry stakeholders to understand their perception of objective tools for biomechanical analysis in the field. The study participants came from professional/elite backgrounds in both the sport horse (n = 6) and thoroughbred (n = 6) sectors. The interview data were analysed using thematic analysis, resulting in four analytical themes. The first theme conveys the importance of tacit knowledge and experience in the holistic analysis of a horse. Theme two highlights that the perfect horse does not exist therefore, equine athlete management is complex and requires a multi-layered problem-solving approach. Theme three describes an awareness among stakeholders of technologies, however they are sceptical of their value. The final theme identified that one of the key barriers to technology adoption is the economic value of the horse and the cost of implementing technology herd-wide. Our findings highlight the need for a user-centred design in this domain, which requires greater consultation and learning between technology developers and equine stakeholders to develop fit-for-purpose analysis and monitoring tools.

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.

Reliability of equine visual lameness classification as a function of expertise, lameness severity and rater confidence

Visual equine lameness assessment is often unreliable, yet the full understanding of this issue is missing. Here, we investigate visual lameness assessment using near-realistic, three-dimensional horse animations presenting with 0-60 per cent movement asymmetry. Animations were scored at an equine veterinary seminar by attendees with various expertise levels. Results showed that years of experience and exposure to a low, medium or high case load had no significant effect on correct assessment of lame (P>0.149) or sound horses (P≥0.412), with the exception of a significant effect of case load exposure on forelimb lameness assessment at 60 per cent asymmetry (P=0.014). The correct classification of sound horses as sound was significantly (P<0.001) higher for forelimb (average 72 per cent correct) than for hindlimb lameness assessment (average 28 per cent correct): participants often saw hindlimb lameness where there was none. For subtle lameness, errors often resulted from not noticing forelimb lameness and from classifying the incorrect limb as lame for hindlimb lameness. Diagnostic accuracy was at or below chance level for some metrics. Rater confidence was not associated with performance. Visual gait assessment may overall be unlikely to reliably differentiate between sound and mildly lame horses irrespective of an assessor's background.