Kevin G. Keegan, DVM, MS, DACVS |
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I was recently asked by a practitioner about using the Equinosis Q with Lameness Locator as part of a baseline evaluation on horses with no perceived indications of lameness, but measure as lame. Her concern was that owners would think that every horse tested is lame and in need of further work up. So how should one approach this scenario when obtaining baseline evaluations on horses?
Lameness is a clinical sign not a disease. I repeat the mantra many times. Many horses (I am guessing at least 70%) will measure strong evidence of lameness in at least one trial. Many horses will measure asymmetrically (i.e. with lameness) but perform without difficulty and with good success, as if they were perfect athletic specimens. However, establishing what we refer to as the baseline gait signature of a horse over time is still invaluable for the veterinarian. If called upon to evaluate this horse for lameness when the horse does later develop pathology or get injured, or become clinically affected in some way, this baseline signature analysis can be used for reference.
Blocking every horse that shows lameness with the inertial sensors is excessive. Not blocking any of them is ignoring information. You must put everything together; therefore, this equipment will not work in the hands of non-veterinarians, or I even dare to say, veterinarians who do not have a good sense of lameness problems in horses.
So, what is a baseline gait signature? This is simply a consistent pattern of vertical head and pelvic movement measured repeatedly in a horse over time.
Amplitude of asymmetry. It is this particular horse’s “usual”. It may have an identifiable cause, it may not. Only by thoroughly examining the horse and, sometimes, by completely working the horse up with blocks and imaging, can one determine the identifiable cause. For example, a horse, with no history or complaint of lameness, which always measures with a mild left hind limb lack of push off, is one day thought to be “off” by the owner or trainer. The depth of your evaluation of this horse will depend greatly on whether your new evaluation finds this same amplitude of left hind limb lack of push off, or something new, like a right hind decreased impact, or a significant worsening of the left hind limb decreased push off.
History of asymmetry. Let’s say you are evaluating a horse for the first time as part of a baseline evaluation using the Q. It is my opinion that you should not make any conclusions based only on a baseline analysis unless, a) there is some other historical evidence that the horse is not performing well, or b) you uncover during the rest of your examination (observation and especially palpation) something that is not right. You are mainly trying to establish how this particular horse moves and then use this information to pay attention to the horse down the road - perhaps evaluating it again after some time in training. Then you are looking for a change. The results should direct you to concentrate on specific limbs in your palpation and (although I am not a strong proponent of flexion tests due to their lack of specificity), with flexion tests.
Consistency of asymmetry. I also always repeat the trial to confirm that lameness measured is stable, meaning it is not changing in limb, amplitude or timing. If the client is not complaining of poor performance but the Q measures lameness, concentrate on and look at every square inch of the identified limbs. If you cannot identify an abnormality in the horse, I do not think that it is prudent to declare anything definitive about the presence of abnormality in this single snap-shot in time. However, I think it is imperative to monitor the horse periodically - especially horses in regular athletic competition at intervals that you think are appropriate depending on the age, size, breed and discipline of the horse.
At the risk of repeating myself, do not just completely ignore evidence of lameness. Make sure you go over the horse with a fine-tooth comb. The intensity and depth of your examination after getting the results will depend greatly on the individual horse. For example, all middle-aged Quarter Horses that develop even mild forelimb lameness, I recommend radiographing their forelimb feet. I have had horses measure with lameness but show no other clinical signs and have no palpable abnormality, but later develop overt lameness in that limb. I wish I had radiographed or blocked earlier.
Case 1
Here is a case that may help illustrate the points. An owner brought a barrel horse in for an analysis at the start of the season. We measured, with strong evidence, but could not see, a mild forelimb lameness. The owner did not want to block the horse, but, because the owner was interested in selling the horse in the future, we decided to radiograph the foot. It was, after all, a Quarter Horse. The x-rays were normal. I just advised her to stay on a regular schedule of trimming and shoeing. She used the horse successfully, without any complaint of lameness, for more than 1 year and then sold the horse.
After a few months of heavy use under the new owner, the horse started to develop right forelimb (now not so mild, and visible) lameness, which was isolated to the right forelimb foot by the local vet. The new owner returned the horse to the seller (my client) and we re-worked the horse up. The right forelimb lameness did not block out to a coffin joint block, but did block out to a PDN. Radiographs indicated very mild, early changes in the flexor cortex of the navicular bone. Because we checked this out one year earlier (reacting to results of the objective evaluation) and had evidence that the horse did not have navicular changes at that time, you can imagine how this shed a more favorable light on the seller. One could argue that we should have worked up the mild right forelimb lameness with blocks and other imaging and, in retrospect, I wish I had; but the treatment recommendations were successful for the owner for over one year.
Case 2
This was another barrel horse from an owner who frequently has me look at his horses before they go into a season of competition. On at least 2 occasions, once at the beginning of the season and once about midway through, even though the horse was performing well, we measured a very mild right hind limb lameness. I could not find anything wrong with the horse on physical examination and did not attempt to block the horse out.
Near the end of one season the horse slipped and fell at a barrel and came up visibly lame in the right hind limb. We could not block out this lameness, and ended up doing a bone scan. We found a fractured third trochanter, which was treated with limited activity and gradual return to exercise. The horse recovered and it is performing regularly now. Was this early and regular appearance of a mild right hind limb lameness (invisible to the naked eye but measurable) a harbinger of the fractured third trochanter? What saved me in the eyes of my client is that I did not ignore it completely and each time we measured it I went over the horse thoroughly. My client realized that this was something only a bone scan would uncover, perhaps, if it was indeed pre-existing in some way. It also made him a big believer in the sensitivity of the equipment and now routinely has his horse screened at the beginning of the season.
Case 3
Lastly, this was an interesting Warmblood case several ago. I was asked to look at a lameness by an owner who did not think there was anything wrong because she was using it regularly for dressage without problem. However, the trainer thought the horse was lame in a hind limb and would not ride the horse without it being checked out. When we examined the horse, it looked to me that the horse was mild to moderately lame in a front and a hind limb, and it measured this way. However, despite blocking the horse over several days we could not isolate the lameness. I recommended to forget about the lameness, ignore the trainer (or get another one), and use the horse.
The owner went on to use the horse for five years without incident. She changed trainers and I did not hear from her again until she decided to sell the horse. The horse had failed the pre-purchase evaluation with a left forelimb lameness and what the examining veterinarian called "chronic end stage arthritis" in the left front coffin joint. The potential buyer accused the seller of fraud despite her turning over all records before the sale. She brought the horse back to me, naturally distressed with new-found interest in finding the cause of this lameness. Guess what? I saw and measured exactly what I saw and measured five years earlier; same limbs, same amplitude.
A second time I tried to isolate the lameness including blocking the coffin joint (the radiographs of the coffin joint were within normal limits) and was unsuccessful. I blocked the entire left forelimb up through the shoulder and bicipital bursa with no improvement in the lameness either to the naked eye or with inertial sensor measurement. I recommended a bone scan but she decided to take the horse home, keep him and just ride him. She used the horse without incident for several months, and again tried to sell the horse. The sale was nixed by another veterinarian who only evaluated a video of the horse, this time for a left hind limb lameness. I do not know if the owner will ever sell this horse, but I have evidence that the horse looks exactly like it did five years ago, no one can really localize the lameness, and it has been used regularly without any progression of its gait signature. There may be pathology in this horse somewhere, but the disease is not progressing. It is staying the same, requiring no treatment, and the horse is performing regularly. This is valuable information to have and only with this information does she have any hope of selling this horse. It is my opinion that this horse just moves asymmetrically.