Lameness in the modern era: Let’s not slip in the VOMIT

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The era of quantitative gait analysis has opened new doors in lameness research, but three senior clinicians are warning of the risk from VOMIT.

VOMIT means Victim of Modern Investigational Technology. The acronym was coined by the medical community as a modern-day warning of the risks of looking at the image rather than the patient.

And herein lies the inherent risk with the rise of gait analysis technology, according to experienced equine clinicians Andrew Bathe, Carter Judy and Sue Dyson.

The trio, in a letter to the Equine Veterinary Journal, were commenting on a recent well-publicized editorial by Rene van Weeren and his colleagues asking whether it was time to redefine lameness, given results from quantitative gait analysis.

Van Weeren noted that when technology quantified the gait of horses considered sound by their owner, many fell outside the normal range and were hence deemed lame. The authors argued that clinicians should be cautious in their use of the term lameness and should discriminate clearly between asymmetry and lameness.

Bathe and his colleagues said while the editorial was balanced and they agreed with most of it, there were some comments they wanted to make.

Lameness, they said, was recognised as a continuum rather than a binary concept.

“Many athletes are not considered perfect from a gait point of view, but are able to compete successfully. This is apparent when watching horse inspections at shows – horses with a range of gait asymmetries are considered fit to compete.”

They said that understanding the range of acceptable normality was the biggest learning curve as a junior clinician.

Research has shown that many horses considered sound by their owners will show a degree of lameness.

“Whilst inertial systems may out-perform the human eye in terms of temporal and spatial resolution, they are a long way off being superior in terms of their critical analysis.

“A simple ‘the computer says lame’ analysis based just on gait asymmetry doesn’t allow for the huge number of variables that are considered in the mind of an experienced clinician looking at the gait of a horse and trying to determine its likely significance.

“Clinical problems often manifest when ridden, such as on turns, when jumping or performing specific movements. The biomechanics of the loading patterns make the problem obvious, in a way it may not be trotting in a straight line.”

Quantitative systems in their current form cannot replace the clinical evaluation of an experienced, observant and thinking clinician, they argued.

“Humans tend to think computers will keep them from making mistakes, when in reality with computers you are able to make mistakes faster and more efficiently.

“When quantitative gait analysis systems measure over half of normal populations as being outside the threshold values that have been set, then surely their range of ‘normal’ needs to be redefined.”

The significance of subtle gait asymmetry in a horse – no matter how it was assessed – needed to be determined by assessing its influence on the horse’s ability to perform its particular discipline, they said.

“This is best achieved by carefully observing the horse’s way of going on different surfaces and when being ridden as well as lunged, rather than by relying on automated quantification.

“Caveat utilitor,” they concluded, using the Latin term for “let the user beware”.

The original editorial by Dr van Weeren and his colleagues can he read here

Horsetalk’s report on the editorial can be read here.

van Weeren, P. R., Pfau, T., Rhodin, M., Roepstorff, L., Serra Bragança, F. and Weishaupt, M. A. (2017), Do we have to redefine lameness in the era of quantitative gait analysis?. Equine Vet J, 49: 567–569. doi:10.1111/evj.12715

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