Comparison of visual lameness scores to gait asymmetry in racing Thoroughbreds during trot in‐hand

Abstract

Summary Regular monitoring of movement asymmetry with inertial measurement units (IMUs) to aid in the diagnosis of the underlying cause of a lameness is feasible. Normal ranges for specific groups of horses may be required, with consideration of expert veterinary opinions for both asymmetry screening and lameness assessment. The aim of this study was to determine movement asymmetry values compared with expert lameness scores to enable screening for lameness in Thoroughbreds in race training. IMU gait assessment during in‐hand trot‐up was performed in 25 racehorses undergoing routine gait analysis or lameness examination at the Singapore Turf Club. Video recordings were graded numerically (0–5) for lameness by six experienced racehorse veterinarians. Inter‐observer agreement and consistency were determined. Median lameness scores were used to calculate sensitivity and specificity for head, withers and pelvic movement asymmetry. Guideline values for aligning movement asymmetry values with expert opinions about forelimb and hindlimb lameness were determined from receiver operating characteristics (ROC). Inter‐observer agreement was poor to fair, inter‐observer consistency was good (intraclass correlation coefficient: 0.667 for forelimbs and 0.617 for hindlimbs). ROCs indicated higher discriminative power for hindlimb lameness using pelvic asymmetry (90% sensitivity, 93% specificity) compared with forelimb lameness using head asymmetry (69% sensitivity, 89% specificity) or withers asymmetry (44% sensitivity, 89% specificity). When compared to expert lameness scores from videos of a limited number of Thoroughbred racehorses, preliminary guideline values for movement asymmetry screening for forelimb lameness (>|14.5 mm|) and hindlimb lameness (>|7.5 mm|) are higher than previously reported clinical thresholds of >|7 mm| for head movement and >|4 mm| for pelvic movement asymmetry.

What is lameness and what (or who) is the gold standard to detect it?

“…It is more than likely that, as in other biological variables, also in the case of locomotion asymmetry these reference values may vary a little with characteristics of the population studied, like breed, equestrian use, age and perhaps other factors. In fact, we already have scientific data pointing in this direction . It can, therefore, be expected that in the coming years with ongoing data collection we will be able to tailor and refine these reference 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

“…This is appropriate for the clinical lameness examination where the task is to identify the affected limb(s). A higher threshold value of 14.5 mm for Poll MinDiff has on the other hand been suggested based on a comparison of visual and quantitative data in Thoroughbred racehorses [ 62 ] which is similar to the daily and weekly variation of 14 mm and 19 mm, respectively, for this parameter in Thoroughbred racehorses in training [ 63 ]. This should be taken into account when interpreting movement asymmetry values in a ”screening” scenario.…”

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

“…This depends on the clinical or research question that needs answering. Here we concentrate on the sacrum, a popular location for quantifying movement symmetry in the context of lameness 10,16,20,23,24 …”

“…A further reduction in the data rate to 40 Hz increases the error to up to 4mm. This value is above the 3 mm threshold 16 for mild lameness suggesting that the influence of such reduced sample rates needs to be considered carefully when dealing with horses displaying mild asymmetries However, the values are still smaller than for example within‐ or between‐day variation in Thoroughbred racehorses in training and asymmetry values identified in Thoroughbred racehorses with lameness 23,24 . It is thus important to consider the intended application when considering whether a specific sample rate, which may be the maximum rate a particular device can achieve, is indeed sufficient.…”