Journal Watch: Objective Measurements Spark Debate Over Lameness Definition & Evaluation Protocols

by Nancy S. Loving, DVM

Many of your horse-owning clients have horses for the purpose of pursuing an equestrian athletic endeavor in addition to the companionship and relationship built with their horse. Clients want their horses to perform to their utmost potential, free of lameness or pain as much as possible. This means that lameness (or soundness) workups are a large part of an equine practitioner’s business. Historically movement evaluation has relied on visual observations but with increasing demands for evidence-based veterinary practice, technology is implemented  to provide a more objective assessment of a horse’s locomotion.

Recently, an ongoing and informative discussion by expert diagnosticians on lameness has been presented in the editorial content of the Equine Veterinary Journal. One of the prevailing controversies focuses on just exactly “what is lameness?”

One concern is that attaching a label of “lame” to a horse is fraught with negative connotations that impact horse owners regarding performance, fitness to compete, or sale of their horse. Another concern centers on whether lameness is a “disease” in itself or is simply a terminology that encompasses a number of clinical signs representative of an underlying pathology. Most practitioners likely agree that just as “colic” is not a disease in itself but rather is a descriptive term for abdominal pain that develops due to a potpourri of reasons, similarly, “lameness” may be considered a descriptor that indicates the horse has asymmetry of bilateral movement.  Keegan (2018) describes bilateral movement as the comparison of right to left halves of stride as weight is shifted to less painful limbs.

Yet another concern expressed in the editorials is whether all gait asymmetries represent some abnormal problem with the horse. Bathe, Judy & Dyson (2018) point out that not all gait asymmetry correlates with an underlying pathological problem – some asymmetries are associated not with pain but rather with a mechanical or neurological issue  that restricts or alters limb motion. In addition, a horse with bilateral limb pain may appear symmetrically “lame” despite the fact that both limbs experience pathology (van Weeren et al., 2018).

When I was but a young, budding veterinarian over three decades ago, a wise practitioner said something at an AAEP meeting that stuck with me for the course of my career: When an owner complains about poor performance, it is important to watch that horse work in the intended discipline. Most notably, he described a roping horse in which the musculoskeletal issue only surfaced at a sliding stop with the calf attached firmly to the saddle horn, which placed undue pressure on the withers. While this may not specifically be a limb problem, it is important to watch a horse in its athletic pursuit.  Bathe et al. and van Weeren et al. also note the importance of visual and conventional assessment of how a horse exercises on different surfaces, terrain, turns, and in sport-specific undertakings. Keegan points out that the beauty of using inertial sensor technology is that it can be used in circumstances not confined only to a straight-line trot out or circles on level surfaces – like flexion tests, nerve & joint blocking effectiveness, and the ridden evaluation. Still, it is important to encourage conventional visual assessment in all cases, using the computer-based analysis as a complementary tool.

Another point of contention (Bathe et al, and van Weeren) is based on whether it is a realistic expectation that horses, in general, should be 100% symmetric in their gait in order to perform their job. It is possible that even normal horses without musculoskeletal pathology or pain demonstrate gait asymmetry – this could be due to different levels of one-sided muscle strength, incorrect training, rider imbalances and error, saddle fitting problems, behavioral issues or the mood of a horse on any given day, to name a few possibilities. All writers of the editorials agree that lameness is a “continuum” rather than being a binary, i.e. a lame or not lame, enterprise.  Inertial sensors can measure slight variations along the continuum.

Proponents of the evidence-based use of inertial sensors to detect gait asymmetry argue that the point of this technology is not meant to supersede veterinarian clinical judgment but rather to work as an ancillary tool for diagnosis, just as radiography, ultrasound, MRI or other imaging techniques help to corroborate clinical evaluation and experience. Keegan (2019) emphasizes that, “Inertial sensor systems outperform the naked human eye because of better temporal resolution; but do not perform a critical analysis, no more than a thermometer, or a radiograph.” Inertial sensors are able to identify if there is limb function asymmetry. As a time saving method, use of inertial sensors enable a practitioner to focus on the limb(s) most responsible for asymmetric movement and then can perform further diagnostic testing to rule in or out areas of the limbs, neck or back. Keegan notes that an equine practitioner “should be using time, skills and experience figuring out how important it (the asymmetry) is and what is causing it.” Just as importantly, as time goes by, researchers in the field of objective lameness measurement  may better define thresholds for what is and what is not likely to be pathological (van Weeren et al.).

One issue at the heart of the debate is that younger generations of equine practitioners may come to rely on technology rather than using human discrimination and diagnostic skills for lameness evaluation. A young intern once approached me with a radiograph of a splint bone taken with DR radiographic equipment when it first became available. The radiographic technique was flawless; the problem – the wrong oblique view was taken so that the fractured splint bone was not in evidence. As with everything in medicine, there is a learning curve, and clinical skills develop with experience. Basing lameness evaluation purely on computerized technology is fraught with risks, particularly with misinterpretation  of data without corroboration of other clinical evidence.   The reasons described above make this a plausible argument; however, there is a remedy for this – education for the practitioner to use the technology appropriately and in a learned manner.

In addition, experience is critical for knowing the most efficient process to work up a lame horse. If young (or more versed) equine practitioners start their lameness workup with their critical eye and then use the inertial sensors to corroborate or nullify their original assessment, such learning may improve their ability to discern many levels and nuances of lameness. Additionally, for complaints about performance problems, it is possible that subtle gait asymmetry may be undetectable to the human eye. It is always better to have a proactive approach to identifying a problem before it becomes severe enough that it is detectable and possibly not as likely to achieve resolution with therapy. Inertial sensors may help define these situations.

As an FEI endurance veterinarian for three decades at elite venues worldwide, I was impressed by how many differing opinions about a horse’s soundness, or not, came from 10-12 extremely qualified veterinarians watching the same animal trot out. Some have a trained eye; others not so much. The point is that there is a huge variation in how well equine practitioners of all levels of experience are able to see lameness and/or identify which limb or limbs might be involved. A recent report (Starke & Oosterlinck, 2018) presented 89 veterinarians with animations of various degrees of asymmetry ranging from 0-60%. For both fore and rear lameness, asymmetry of at least 40% (Grade 1/5) was necessary before at least half of the practitioners identified lameness in the correct limb.

From a welfare standpoint, this is important because many equestrian sports dictate that horses should not compete unless moving at a particular comfort level defined by the AAEP lameness scale. Then, subjective assessment by the venue veterinarian(s) may rightly or wrongly identify which individuals are fit to continue. This has important consequences for horse owners who have substantial investments in time and finances to develop their horses to a certain level of competition.

As I sit in front of my computer, I think back to the days of using a typewriter three decades ago to do my writing. Then came a computer to help with word processing. Then came the Internet to help disseminate the writing in an instant to publishers to get the word out to others in the equine industry. None of this altered my actual use of words to convey a message. But as a tool, the computer made it possible for rapid communication and dissemination of information. If inertial sensor technology is viewed as a tool to define an asymmetric gait rather than the end in itself, there is a strong possibility that equine welfare will improve through early recognition and appropriate treatment of true physical problems experienced by an equine athlete.

 

Letters & Citations

Letter #1: 13 August 2017

https://onlinelibrary.wiley.com/doi/full/10.1111/evj.12715

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

Letter #2: 27 December 2017

https://onlinelibrary.wiley.com/doi/abs/10.1111/evj.12791

Bathe, A. P., Judy, C. E. and Dyson, S. (2018), Letter to the Editor: Do we have to redefine lameness in the era of quantitative gait analysis?. Equine Vet J, 50: 273-273. doi:10.1111/evj.12791

Letter #3: 06 April 2018

https://onlinelibrary.wiley.com/doi/abs/10.1111/evj.12820

Adair, S. , Baus, M. , Belknap, J. , Bell, R. , Boero, M. , Bussy, C. , Cardenas, F. , Casey, T. , Castro, J. , Davis, W. , Erskine, M. , Farr, R. , Fischer, T. , Forbes, B. , Ford, T. , Genovese, R. , Gottschalk, R. , Hoge, M. , Honnas, C. , Hunter, G. , Joyce, J. , Kaneps, A. , Keegan, K. , Kramer, J. , Lischer, C. , Marshall, J. , Oosterlinck, M. , Radue, P. , Redding, R. , Reed, S. K., Rick, M. , Santschi, E. , Schoonover, M. , Schramme, M. , Schumacher, J. , Stephenson, R. , Thaler, R. , Vedding Neilsen, J. and Wilson, D. A. (2018), Response to Letter to the Editor: Do we have to redefine lameness in the era of quantitative gait analysis. Equine Vet J, 50: 415-417. doi:10.1111/evj.12820

Letter #4: 28 June 2018

https://onlinelibrary.wiley.com/doi/abs/10.1111/evj.12970

van Weeren, P. R., Pfau, T. , Rhodin, M., Roepstorff, L. , Serra Bragança, F. and Weishaupt, M. A. (2018), What is lameness and what (or who) is the gold standard to detect it?. Equine Vet J, 50: 549-551. doi:10.1111/evj.12970

Letter #5: 20 December 2018

https://onlinelibrary.wiley.com/doi/abs/10.1111/evj.13043

Adair, S. , Baus, M. , Bell, R. , Boero, M. , Bussy, C. , Cardenas, F. , Casey, T. , Castro, J. , Davis, W. , Erskine, M. , Farr, R. , Fischer, A. , Forbes, B. , Ford, T. , Genovese, R. , Gottschalk, R. , Hoge, M. , Honnas, C. , Hunter, G. , Joyce, J. , Kaneps, A. , Keegan, K. , Kramer, J. , Labens, R. , Lischer, C. , Marshall, J. , Oosterlinck, M. , Radue, P. , Redding, R. , Reed, S. , Rick, M. , Santschi, E. , Schoonover, M. , Schramme, M. , Schumacher, J. , Stephenson, R. , Thaler, R. , Nielsen, J. V. and Wilson, D. (2018), Letter to the Editor: A response to ‘What is lameness and what (or who) is the gold standard to detect it?’. Equine Vet J. doi:10.1111/evj.13043

Study

Published Online First: 21 September 2018

Starke, SD., Oosterlinck, M. (2018) Reliability of equine visual lameness classification as a function of expertise, lameness severity and rater confidence Veterinary Record doi: 10.1136/vr.105058