Trying to determine the clinical significance of any biomechanical asymmetries has been a fundamental question for owners, vets and physiotherapists alike. It can be frustrating for vets when clinical lamenesses are diminished under the guise of asymmetry - "oh he's just a bit asymmetric, he's not really lame". (The word "unlevel" is often used interchangeably for asymmetric). This can be especially true during pre-purchase examinations, where nobody is keen to acknowledge a subtle lameness for what it could potentially mean. But can a horse be asymmetric in the absence of clinical lameness? And is there a definable threshold between physiological asymmetry and pathological lameness? Do asymmetries have consequences for training and therapy?
An interesting and accessible article has been published this week in The Horse, following scientific publication in Animals at the end of last year, (Macaire et al. 2022). Researchers at the National Veterinary School in Maisons-Alfort, France have been trying to answer some of these very questions. They have used highly sensitive inertial measuring units (IMUs) to quantify biometric vertical displacement data to quantify asymmetries and lamenesses. Henry Chateau, DVM, from the research team highlights that the potential over-diagnosis of horses as lame, when these sensitive systems pick up mild, non-pathological asymmetries, can have significant implications for the owner or trainer, particularly financial. As part of their study, 49 horses were assessed visually as perfectly sound by a team of locomotor experts. It was found that none of these horses were perfectly symmetrical however when their movement was analysed with the IMUs. This asymmetry may well be imperceptible to the naked eye. Data was used to determine thresholds above which an asymmetry could be considered a lameness although it was recognised that much more work is required in this area. The study further defined horses within each lame group as having a minimum grade of lameness as 2/10, as assessed by the research team. Any horse with a 1/10 lameness was excluded from both the sound and lame study groups. Horses with lamenesses in multiple limbs were similarly excluded. But perhaps these are the groups which holds the most interest for research and discussion.
This latest research is of significant and timely interest to Equilibre as we have just this week finished the data collection for our study into the prevalence of gait asymmetries and subtle lamenesses in horses which are in work and perceived by their owners to be sound. The data has yet to be fully analysed however it is clear that both asymmetries and low-grade lamenesses are readily identifiable using body-mounted inertial sensors in the vast majority of these horses. Watch this space to find out more.
Links:
Leste-Lasserre, C., 2023. Researchers Determine Fine Line Between Asymmetry and Lameness. The Horse.
Macaire, C., Hanne-Poujade, S., De Azevedo, E., Denoix, J.M., Coudry, V., Jacquet, S., Bertoni, L., Tallaj, A., Audigié, F., Hatrisse, C. and Hébert, C., 2022. Investigation of Thresholds for Asymmetry Indices to Represent the Visual Assessment of Single Limb Lameness by Expert Veterinarians on Horses Trotting in a Straight Line. Animals, 12(24), p.3498.
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