Objective Lameness assessment and Kinematics
When a horse is experiencing pain when bearing weight on a particular limb it will naturally look to reduce the force carried through that limb, by the simple laws of physics F=MA, this will in turn alter the horses movement, it will look to reduce either the mass (M) over the limb or the acceleration (A) of the limb, called antalgic gait, only when the animal needs to reduce the force to a larger extent that the gait will change to a “limp” (Keegan 2019).
Recent studies have shown that a large percentage of working horses are lame without recognition, a change in gait is the tell tale sign that equestrians use to recognise lameness but many horses can show changes too subtle to the naked eye, with only a drop in performance or change in behaviour to suggest discomfort (Dyson et al 2017), even amongst experienced veterinarians the observer agreement for lameness is questionable, this subjectivity effects the efficiacy of diagnosis and treatment (Hammarberg et at 2016).
The technology is available now to quantitively measure lameness by objective gait analysis through kinematics, this ability to asses more and more subtle gait abnormalities opens a new area of necessary research, is there such thing as a completely symmetrical gait and where do we draw the line between normal gait asymmetry and lameness (van Weeren et al 2017) for example, Hobbs et al (2018) used the technology to investigate the effects of asymmetrical conformation on gait, it found that a high low hoof conformation created asymmetrical propulsive forces which could cause adverse effects on the musculoskeletel system, does this mean that horse is lame? Or just predisposes to certain pathologies?
Serra Braganca et al (2018) suggested that lameness be defined as an assymetric gait caused by an underlying pathological dysfunction, but although this addresses the definition of lameness it creates a new subjectivity until this relationship can be quantified, the parameters that constitute lameness are being developed with vertical displacement being the most common focus, but the relationship between asymmetry and pain is still to be answered, bi-lateral lameness raises even more questions of a modality that assesses by side comparison (Serra Braganca et al 2018), although this technology enables easy recognition of gait irregularities, specifying the causality in terms of pathology is more complexed, Barry (1999) suggested that the technology be used to compliment conventional diagnostics.
As well as answering and raising questions on equine lameness detection the technology is being used to bring a new dynamic to other areas of research, saddle fit (Murray et al 2018, Mackechnie-Guire 2018), girth fit (Murray et al 2013) and rider-horse-tack relationships (Guire et al 2016), the technology gives the equestrian research world an objective method of analysing physiological and environmental effects on gait (Holt 2017, Taylor et al 2019), giving insight to the different equestrian professions on practical application, from saddlers to farriers (Stutz et al 2019).
The technologies applications go beyond objective lameness assessment and its use is becoming more wide spread in equestrian sports performance enhancement, analysing both the animal and the rider, enabling corrections to the rider’s position and changes to the horses care, from shoeing plans to physio treatments (Centaur biomechanics 2019).
The technology does have its limitations, the velocity of movement potentially effects the readings of hind limbs (Moorman et al 2017), placement of sensors has to be anatomically accurate to ensure reliability of results (Moorman et al 2017) and skin movement can effect readings as the sensors are placed superficially (Serra Braganca et al 2017), although quantification of these limitations can enable them to be factored into readings.
As the systems available become more varied, with differentials in quality, the reliability of the modality can come into question (Serra Braganca et al 2018).
How it works
· Sensors/markers are attached to specific anatomical regions of the Horse
· High speed cameras film the horse dynamically
· The information is filtered and analysed by computer software
· Subtle changes in gait are made manifest and a report is created describing the movement of the given horse
(Centaur biomechanics 2019)
Fig 1. Markers and computer software create a model of the horses movement.
(Centaur biomechanics 2019)
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