LAMENESS LOCATOR

Lameness Locator is your friend not your enemy

2012-02-26T20:47:00.000-08:00

I was once told this by a practicing equine veterinarian, "[Lameness Locator] devalues the need/expertise of the veterinarian". This was my response.

This is something that I have run into many, many times and it is a completely misplaced concern. In fact I think it is quite sad and depressing. Anyone who thinks this really knows nothing about Lameness Locator and, in my opinion, is trivializing the role of the veterinarian in diagnosing and treating lameness in the horse. First of all, Lameness Locator is sold to equine veterinarians only. It will never, ever, over my dead body, be sold to anyone other than equine veterinarians. There is good reason for this. The information provided by Lameness Locator is only helpful to equine veterinarians, anyone else and the information will be useless and potentially abused. Also, the client knows nothing about the Lameness Locator results, it is just a bunch of squiggly lines to them. It requires the equine veterinarian to explain it to them. Does this thinking also apply to radiographs, to ultrasound? Does taking radiographs devalue the need/expertise of the veterinarian. Does performing an ultrasound devalue the need/expertise of the veterinarian? Of course not. It actually increases the need/experience of the veterinarian. Without the veterinarian interpreting the results the images are pretty worthless. Of course you have to be able to interpret the images and if you do not use Lameness Locator you cannot interpret the reports. There is also much, much more to working up a lameness than picking the correct limb or limbs. This is just the tip of the iceberg, moments in the time span of a complete lameness evaluation. Understanding the history, use of horse, limb palpation, blocking, image interpretation, deciding how next to proceed, image interpretations, deciding what imaging to perform, putting all the pieces together, conversing with the owner, finding out what he/she really wants…..This is where the skill, knowledge, expertise, and if I may add, the art, of the equine veterinarian shines through in lameness evaluations. Pinning the bulk of the perception of the need/experience of the veterinarian on picking the correct limb or limbs is very short-sighted. In my opinion is it a cheap portrayal of reality.

Ross and Dyson, "Lameness in the Horse": A study.

2011-12-31T08:57:00.000-08:00

You have heard of Bible study. The line by line dissection of passages searching for spiritual meaning and the literal, or not so literal, interpretation of what the passages really mean. Everyone would agree that the bible is a must read for the Christian.

Well, for the equine practitioner interested in lameness evaluation, a must read is the chapter in Ross and Dyson’s new “Lameness in the Horse”, which can be thought of as a sort of version of an equine lameness bible. Although the entire book is excellent, chapter 7, by Dr. Ross, is by itself worth the price of the book. The chapter is not an easy read, but if read slowly and deliberately, and studied in depth, the reader will find it chock full of pearls of wisdom that are, for the most part, not only obviously Dr. Ross’ professional opinion, which by itself would be adequate, but remarkably consistent with experimental studies. For those of you currently using Lameness Locator it is definitely a beneficial read.

http://www.elsevier.ca/ISBN/9781416060697/Diagnosis-and-Management-of-Lameness-in-the-Horse?vm=r

I have read and studied, in depth, this chapter in the latest version of the textbook (as well as in earlier versions) and have reconciled it with published, evidence-based equine veterinary literature as well as with what I have measured in our lameness laboratory and in research and clinical cases using the Lameness Locator system. In an attempt to make sense of what you have come to expect with Lameness Locator results in light of what is described in this chapter, I will periodically, starting today, take and interpret, giving my own opinion, certain “passages” from this chapter. Perhaps this will stimulate comments and discussion by others.

The first point I would like to consider, and actually concede, is the difference between Dr. Ross’ definition of compensatory lameness and mine. Dr. Ross defines compensatory lameness as a true lameness, an actual secondary or complementary lameness, from overloading of limbs due to the primary lameness. Compensatory lameness, as defined in the Lameness Locator training manual and other training publications, is an apparent, but false lameness, due to load shifting away from the primary lame limb. Theoretically, this compensatory movement, should be abolished once the primary lameness, for example after a successful block, is abolished. Long term compensatory load-shifting, however, can develop into a true, i.e., painful, secondary lameness, which of course, would not be immediately abolished after blocking out the original, primary lameness. This definition of compensatory lameness, as an apparent, but actually false lameness, has always been made clear in the Lameness Locator literature. But, I would concede that it is probably not semantically appropriate to use the noun “lameness” to describe something that is not really painful.

The Lameness Locator system picks up asymmetric torso movement. So, it will measure apparent, but false lameness, as a true lameness. It is up to the user to decide, drawing from his/her knowledge and experience, about compensatory movement patterns and secondary lameness occurrence (studying this chapter will help), what is what. This is another example of why Lameness Locator, as it is with any medical device, will be useless in the hands of anyone other than an equine veterinarian.

Understanding the difference between an actual compensatory or secondary lameness and compensatory movement that only looks like lameness is paramount to understand the Lameness Locator results as well as to understand much of what is described in Chapter 7 of Ross and Dyson.

For the next blog entry, I will try to describe what Dr. Ross means by this passage, “Moderate-to-severe hindlimb lameness can mimic ipsilateral forelimb lameness….”, which can be found as the last sentence on page 66, in the section entitled, “Determination, Grading, and Characterization of Lameness”. I will be concentrating on the word “mimic”."

Law of Sides, Why I Use Lameness Locator on Every Case

2011-12-27T14:59:00.000-08:00

I had a case the other day that points out 2 things very clearly, 1) the second part of the “Law of Sides” and 2) why I put Lameness Locator on all my lameness cases.

The second part of the “Law of Sides” is the second rule for evaluating compensatory lameness patterns in the other half of the body in horses with primary lameness in one limb. The first rule, which is not the subject of this post, states that, when a horse is trotting, an apparent ipsilateral lameness, e.g., a right forelimb and a right hind limb lameness, is most likely a primary hind limb lameness with a compensatory, and therefore false, forelimb lameness. This first part of the “Law of Side” is well known to most equine practitioners, something that happens very often, and is something to definitely watch out for when performing lameness evaluations in horses. The second part of the “Law of Sides” is, however, most often understood as just the opposite, i.e., an apparent contralateral lameness, e.g., a right forelimb and a left hind limb lameness, that is most likely a primary forelimb lameness with a compensatory, and therefore false, hind limb lameness. But this second part of the “Law of Sides” is a little less simple that this above explanation implies. The compensatory pattern of vertical pelvic movement, which is what Lameness Locator uses to detect hind limb lameness, can be one of two different possibilities, or it can be both. A primary forelimb lameness may cause an apparent compensatory, but false, ipsilateral hind limb impact type lameness, or an apparent compensatory, but false, contralateral hind limb pushoff type lameness, or both. This pattern of compensatory vertical pelvic movement has been measured experimentally, and the contralateral hind limb pushoff pattern is more common and significant, but both can occur.

Here is an explanation of this observed pattern. If a horse has a primary forelimb lameness, when it is trotting, it will shift its weight backward slightly during the diagonal stance phase including the affected forelimb. So, the pelvis will fall more on the contralateral hind limb compared to the ipsilateral hind limb. This makes it appear like, and with Lameness Locator, measure like, the horse is coming down less hard on the ipsilateral hind limb. Thus, the ipsilateral hind limb impact type lameness. However, if the horse is trotting in a straight line, in order to keep going in a straight line, the horse will then push off harder on the opposite diagonal stance phase, the one including the normal forelimb. So the pelvis will rise more during pushoff of the ipsilateral hind limb. This makes it appear like the horse is not pushing off so hard on the contralateral hind limb, the one in the same diagonal stance phase as the lame forelimb. Thus, the contralateral hind limb pushoff type lameness. Horses with forelimb lameness can display no compensatory vertical pelvic movement pattern, or it can display one of the above mentioned patterns or both.

I have taught the “Law of Sides” to veterinary students for the last several years and I have usually told them that the second part tends not to be a problem, either for subjective evaluation or for using Lameness Locator, because the primary forelimb lameness has to be quite severe before you will actually appreciate the asymmetric vertical pelvic movement. The following case proves me wrong and reinforces that there are always exceptions to any rule. It is also a very good example of why it is good to put Lameness Locator on all lameness evaluations, even when it, at first, looks like an easy lameness.

This following case presented as a right forelimb lameness by a referring veterinarian, who is also a very good friend of mine. He is an experienced equine practitioner with years of lameness experience. He was convinced that the horse has a right forelimb lameness, but could not block it out, so sent it to me for a 2^nd opinion and further workup. When I looked at the horse I saw what I thought was a right forelimb and right hind limb lameness. My first thought was the first part of the “Law of Sides”, i.e. the horse truly had a right hind limb lameness with a compensatory but false right forelimb lameness. The Lameness Locator results showed very clearly that the vertical pelvic movement pattern was a classic compensatory pattern for primary right forelimb lameness; an ipsilateral (right) hind limb impact type lameness, and a contralateral (left) hind limb pushoff type lameness. Without the Lameness Locator results I may have become flustered with the subsequent results of the many blocks that we later performed on the right forelimb. Did we really have a right forelimb lameness, or should I block the right hind limb? I stuck to my guns because of the Lameness Locator results and finally blocked the horse out to the shoulder. The point being that, even in the apparently easy cases (I would have thought the horse had a right hind limb lameness), you just cannot tell until you are well into the case, whether the Lameness Locator results will be helpful to you. Deciding to use Lameness Locator in the middle of an examination, as a second thought, is added work. You have to go get the sensors, apply them to the horse, re-trot the horse up and down, and it is just a pain in the neck. Putting the sensors on at the beginning of the examination in all lameness cases prevents this added work. If you do not need the information and you find just what you thought you would find, then nothing is lost.

I have used this approach, putting Lameness Locator on all my lameness cases, for the last several years. I have yet run into the client that is not willing to pay the few extra dollars (we charge an extra $75 per lameness evaluation when Lameness Locator is used). Most appreciate the extra objectivity and are interested in looking at the results themselves.

this is just a practice run

2011-11-20T08:17:00.001-08:00

this is just a practice run

When lunging, use Elasticon to prevent gyro sensor rotation!

2011-11-02T13:29:00.000-07:00

I do not know exactly why it is that the gyro sensor has the propensity to rotate around to the back of the limb when the horse is lunging, but it does. Usually you do not actually see it rotate, and, frequently, you do not even notice it sitting on the back of the pastern either, until it is too late. You just see weird results. Hopefully it is noticed and corrected. Worse yet, it could go unnoticed and decisions get based on wrong results. Here is an example.

This horse has obvious left hind limb lameness with a suspected compensatory left forelimb lameness. This is the baseline straight evaluation.

But, then the horse was lunged and evaluated, as usual, first to the left and then to the right. When lunged to the left the left hind limb and left forelimb, which is most likely compensatory, are easily seen.

The horse was then lunged to the right. Obviously something is not right. The report now indicates a right hind and right forelimb lameness. While trying to reconcile this in our heads, i.e. we are seeing a left hind and the computer is picking up a right hind, someone noticed that the gyro was on the palmar aspect of the right front limb.

You cannot tell from the results when the gyro started rotating and when it actually reached the palmar aspect of the right front pastern. It could have started rotating anytime between the start of collection of lunge left and end of collection lunge right. Here is the problem with a rotated gyro. It is actually a fairly complicated situation.

1. The gyro does not have to be “exactly” on the dorsal surface of the pastern. As long as it is approximately on the dorsal surface the collection and analysis will be OK. We have not studied this in detail but my guess is that as long as the gyro sensor has not rotated so much that it is on the extreme medial (it usually rotates medially) or lateral aspect of the pastern the analysis will be correct.

2. When the gyro rotates 90 degrees such that it is on either the medial or lateral aspect of the limb, you can expect anything and everything. Sometimes the analysis will be correct, sometimes it will be exactly opposite, sometimes it will switch back and forth between limbs, and sometimes an analysis cannot actually be performed (i.e. the software will crash). This is because the software cannot decipher the timing of right forelimb stance correctly, because the right forelimb gyro signal is weak. It may happen to get it right, it may happen to get it wrong, it may break up the trial into segments and sometimes get it right and sometimes get it wrong, or it may not even recognize the second or gyro channel as something coming from a horse, so…. it crashes. You can see this is what happened in the lunge right collection for the forelimb evaluation. .

3. When the gyro rotates 180 degrees such that it is on the palmar aspect of the limb, you can expect the results to be exactly the opposite of that reported. Right becomes left and left becomes right. This is what happened in the lunge right collection for the hind limb evaluation.

Here, by the way, it the correct evaluation, after we put the gyro in the right orientation and recollected the data.

So, just as a matter of course, if I am going to evaluate the horse during the lunge, I simply place a single strip or throw of Elasticon around the top edge of the pastern wrap, as shown. This will give you peace of mind and save you from a few headaches.

Philosophy of Lameness: Using Lameness Locator to “chase” a second lameness.

2011-10-22T08:02:00.000-07:00

Finding a horse with a hind limb and a forelimb lime that appear “lame” is a pain, for you and the horse. I have always struggled with what to do in a situation like this. Using the inertial sensors, which is more sensitive to detecting asymmetry of torso motion, which could be due to lameness, may make this determination even more difficult. This is especially true since hind limb asymmetry, which may be difficult to pick up with the naked eye, is easily picked up with the inertial sensors. I am, at least partially, guided by the “Law of Sides” that proposes that the most significant problem in an apparent ipsilateral lameness is the hind limb, while in an apparent contralateral lameness the most significant problem is usually the forelimb. This first part of the “Law of Sides” is generally true, but the second part is somewhat misleading. In fact, horses with primary forelimb lameness will have what appears to be either, or both, an ipsilateral hind limb impact lameness or/and a contralateral hind limb pushoff lameness. Close consideration of these observations quickly uncovers a “chink in the armor” of “The Law of Sides” for peeling out these multiple-limb lameness problems. Where is the likely primary problem in a horse that has an ipsilateral lameness and the primary component of the hind limb lameness is “impact”. It could go both ways.

This is where patience and experience and, if I might add, a realization that not every case follows the rules, is your strongest ally. This is also why putting the inertial sensors into the hands and use of non-veterinarians is a recipe for disaster. Here is a case with an apparent right forelimb and right hind limb lameness, which is primarily impact in type, which ended up being a primary right forelimb diagnosis. It was the history given by the owner, and maybe flexion tests, which helped to sort the case out. In addition this case shows that a significant effect of the block may be a change in the type of lameness, rather than simply a reduction in amplitude of vertical head movement asymmetry.

Here is the baseline straight. Subjectively the horse maybe had a very mild right front. Nothing was certain in the hind. From this report we see the right front (4 strikes) and the right hind (3 strikes). The right hind is of impact type.

This is the conundrum. Should I go with the right front as the primary or the right hind as the primary? The owner helped here, by indicating that the lameness, now about 2 weeks old, was more dramatic and, he thought, right front, several days prior to presentation. Flexion tests helped also (not shown), with a right hind flexion test negative, and a right forelimb flexion test positive. But, it was still an educated guess.

Here is the result of a right forelimb biaxial, palmar digital nerve block.

No change, at least not in the right forelimb. The right forelimb is a little worse. The right hind limb is now below threshold. Just maybe I picked the correct limb to start blocking. Also, the horse did not look any different subjectively.

Here is the result of a right forelimb biaxial, abaxial sesamoid nerve block.

In addition to the horse looking subjectively better, we can see a dramatic shift in the type of lameness from primarily midstance to definitively end of stance. Notice that if only the a1/a2 value was being tracked, this improvement in block would not have been “picked up”. Uh oh, the right hind limb lameness is back, but not it is pushoff and impact. Could this be a true lameness or some weird compensation from the block? Don’t know yet.

Here is the result of a right forelimb biaxial, low 4-point block. Not much different than after the abaxial sesamoid block, except that perhaps both right front and right hind are slightly better.

We ended up radiographing the right front limb and found an OCD lesion in the medial condyle of the pastern. Because of the history and age of the horse we decided at this time not to pursue the potential right hind limb lameness. Although we were picking it up with the inertial sensors, we were not “seeing” it and it was not part of the problem originally suspected by the owner.

The purpose of this case presentation was merely to point out a few; 1) ipsilateral lameness with hind limb impact type can be difficult to interpret, 2) do not rely only on a1/a2 values to detect improvement after blocking, 3) sometimes the most dramatic change after blocking is a change in the type of lameness. One other point is worth mentioning, and actually this is the main point of the post. Why did I not “chase” the potential right hind limb lameness? Now we are getting more into the “philosophy” of lameness than into understanding the specifics of the LL report, but it has just been my experience that chasing after a second lameness (after you think you have found the primary lameness), is usually a futile exercise. Secondary lameness can occur frequently and this lameness can be either in the same limb or other limbs. I think this is usually from overuse or overstress secondary to the primary lameness. Usually this secondary lameness is widespread within an affected limb and almost impossible to block out. Anyone who has had an iliotibial band syndrome secondary to primary leg lameness in the other side can attest to what I am getting at. If this right hind limb is persistent and is seen at recheck examination, I will think more of it.

A case example. Using the "4 strike rule" with Lameness Locator reporting

2011-10-19T12:19:00.000-07:00

After using Lameness Locator and looking at its reports over the years, I have developed what I call the "4 strike rule" for quickly evaluating the report. The more strikes against a certain limb, the more confident you should feel that that limb is, in some way, involved in the lameness of the horse. It is up to the user, taking into consideration everything else he has uncovered (history, limb palpation), to make the final determination of what limb(s) is(are) the primary cause of lameness and what limb(s) is (are) secondary. Here is a good example of a case sent in by a current Lameness Locator user.

THE 4-STRIKE RULE

Baseline Straight:

Forelimb Evaluatio:

1. Is there an accumulation of rays in a particular quadrant?

Yes. Accumulation of rays pointing down (LF midstance) - strike 1 LF

2. Is the A1/A2 ratio for either LF or RF greater than threshold of 0.5?

Yes, A1/A2 for the LF is 0.67 - strike 2 LF

3. Is either the mean of Maxdiffhead or Mindiffhead (or both) outside the normal threshold range of +/-6 mm?

Yes. The Maxdiffhead is -15.7 - strike 3 LF

Note: When evaluating maxdiffhead and mindiffhead, either or both can be elevated above threshold for this 3^rd strike. Impact lameness will have elevations in both maxdiffhead and mindiffhead of the same sign. Pushoff lameness will have elevations in both maxdiffhead and mindiffhead, but they will be of opposite sign. Midstance lameness will only have elevations in mindiffhead.

4. Is the standard deviation of the elevated mean(s) less than the absolute of that elevated mean?

Yes. The standard deviation is 10.3 mm, which is less than the absolute value of the mean (15.7) – strike 4 LF

Conclusion of forelimb evaluation: 4 strikes, gives strong evidence for a LF midstance lameness.

Hind Limb Evaluation:

Note: for hind limb evaluation there are 2 subplots. The subplot on the left is the status of the left hind limb and the subplot on the right is the status of the right hind limb. Red rays up indicate lack of pushoff on the affected limb. Green rays down indicated decrease impact on the affected limb. The longer the rays the more significant the asymmetry of pushoff or impact between right and left

1. Is there an accumulation of rays in a particular quadrant ?

Yes, there is an accumulation of long red rays up on the LH. The horse is pushing off less hard (a lot) on the LH. There is also an accumulation of short green rays down on the left. The horse is coming down less hard (a little) also on the left. Strike 1 LH

2. Is the A1/A2 ratio for either LH or RH greater than threshold of 0.17?

Yes, A1/A2 for the LH is 0.62. Strike 2 LH

3. Is either the mean Maxdiffpelvis or Mindiffpelvis (or both) outside the normal range of +/- 3 mm?

Yes. The Maxdiff is -16.5 mm and the Mindiff is -6.7 mm. Strike 3 LH.

Note: For the hind limb, Maxdiff always indicates lack of pushoff. So, horses with hind limb push off lameness will have elevated Maxdiffpelvis. Mindiff always indicated lack of impact. So, horses with impact lamenesses will have elevated Mindiffpelvis. Also, positive values always indicate right and negative values always indicated left hind limb lameness.

4. Is the standard deviation of the elevated mean value(s) less than the absolute value of their respective means?

Yes, Maxdiffpelvis is -16.5 mm with a standard deviation of 4.3 mm (very consistent LH pushoff deficiency). Also, the Mindiffpelvis of the pelvis is -6.7 mm with a standard deviation of only 1.9 mm (very consistent LH impact deficiency, albeit not as severe as the push off component). Strike 4 LH.

Note: The standard deviation is important because it gives the user an appreciation for the variability of the collected data. When the standard deviations are smaller than the absolute value of their respective means, then the lameness is consistent to one side. When the lameness is consistent to side then the confidence of detecting lameness is increased.

For example, the MaxDiffpelvis of this horse -16.5 mm with a standard deviation of 4.3 mm. Therefore the MaxDiffpelvis over all the collected strides ranged from -20.8 mm to -12.2 mm. All strides had a negative MaxDiffpelvis, so all strides were “off” on the LH. The LH asymmetry was very consistent.

It is always important to inspect the MaxDiff and MinDiff mean values and their respective standard deviations. Evaluating the A1/A2 ratio alone does not give the user any appreciation of data variability. Also, when data variability is high the A1/A2 values may be artificially increased or decreased, depending on the situation. The A1/A2 value, by itself, also does not give the user any indication of type (i.e., impact or pushoff) of lameness.

Highly variable data tends to be more of an issue with forelimb evaluations (due to head tossing, acting up, etc). For example, say you had a mean Mindiffhead of 9 mm but the standard deviation was 15. That mindiffhead values over all strides actually ranged from +24 mm (indicating RF) to -8 mm (indicating LF). Standard deviations higher than the absolute value of the mean could signify either inconsistent lameness or it could mean that the horse was acting up too much, creating false asymmetry. Lameness Locator is equipped with algorithms to lessen this affect, but very badly acting horses, with lots of head tossing and shaking, still adversely affect the results.

Evaluating the lunge:

Notes on Lunging Data: DO NOT USE THRESHOLDS FOR NORMAL… they do not hold when the horse is moving in a circle because the horse’s torso is tilted. Instead, it is best simply to compare lunging in one direction to lunging in the other direction and then to look for 1) unexpected patterns, and 2) large differences in patterns between directions. These differences can be easily seen often simply by a quick inspection of the ray diagrams. Closer inspection by comparing values and signs of maxdiff and mindiff between directions can also be helpful. In general, in normal horses, the ray diagrams should be close mirror images of one another and the rays should be similar in length.

In the above example

Lunging left:

In the forelimb ray diagram, although the rays are pointing toward end of stance on the inside limb (this is an abnormal, odd pattern), ray length is short. This is not very impressive.

In the hindlimb ray diagram the green down on the left is not normal. re is definitive decreased push off (red rays) and impact (green rays) of the LH. The red rays up on the left are not normal. The green rays down on the left are normal when the horse is lunging to the left. See below, #2.

Note: There are a few commonly seen hind limb patterns of maxdiffpelvis and mindiffpelvis when horses are lunging. Normal patterns depend somewhat on the firmness of the lunging surface.

1) When horses are lunging on a firm surface, it is not uncommon to normally (i.e. in sound horses) see what appears to be an inside hind limb impact lameness and sometimes an inside hind limb impact and pushoff lameness.

2) When horses are lunging on a soft surface, it is not uncommon to normally (i.e., in sound horses) see what appears to be an inside hind limb impact and outside hind limb pushoff type lameness.

In the above example the inside hind limb impact lameness (green down on the left) can be considered normal. But, the inside hind limb pushoff lameness is not usually seen in normal horses.

Lunging right:

In the forelimb ray diagram there is a strong LF (outside limb) impact asymmetry. This is not commonly seen in normal horse.

In the hind limb ray diagram, the green down on the left is not normally seen.

Taking into consideration lunging in both directions, these few observations stand out.

1. There is a LF asymmetry in both directions. This is evidence of a LF lameness.

2. The hind limb ray diagrams have accumulations of rays while lunging in either direction but these rays are not mirror images of one another when comparing lunging in one direction to lunging in the other. The LH pushoff lameness going to the left is abnormal. The LH impact lameness going to the right is abnormal.

Overall Evaluation:

Looking at straight line data alone, one would be suspicious that the LF is compensatory for the LH, however, the lunge data is suspicious of a LF and LH. Determining primary and compensatory lameness from lunging data has not been validated and tends to be confusing. Also, it is not uncommon for forelimb lameness issues to be exacerbated during the lunge and for hind limb lameness to be more easily seen during the straight line trot. So, this horse may have a primary hind limb lameness when traveling in a straight line and both (LF and LH) when lunging. Only the vet, with additional examination, blocking, and possibly other diagnostic procedures will be able to sort this out.

Lameness Locator: What is in a name?

2011-10-18T13:48:00.000-07:00

“Lameness Locator”, the name, was first coined by Dr. Ted Kellerman, then a 4^th year veterinary student at the University of Missouri, now an equine practitioner and Lameness Locator user outside St. Louis, Missouri. He said, and it later turned out to be true, that the body-mounted inertial sensor system that we developed as an aid to subjective evaluation of lameness in horses needed a name. “Body-mounted-inertial-sensor-system used as an aid-to-subjective-evaluation-of-lameness-in-horses” is simply too long. Being busy at the time and not very good at things like that, I thought the name was rather catchy. It flowed easily off the lips and was easy to remember. I could imagine 2 “L’s” crossing each other as a simple logo. I overlooked the potential negative connotation engendered by the simplification.

So, let us set this straight, Lameness Locator does not “localize lameness” in the sense of “localizing” within the limb. This is, nor will it ever be, a claim. Localizing lameness within the limb, now and in the future, can only be accomplished through thorough veterinary investigation including observing the horse in motion, limb palpation, blocking, and imaging. Maybe this just seemed so obvious to me that I failed to see it as some have. “Locator” refers simply to “locating” the affected limb or limbs and determining whether the lameness is likely to be impact or pushoff type. This of course, is practical and informative, but hardly unbelievable. There is really no compelling reason to assume the narrowest interpretation of the term “Locator”, though it is clear from some of the comments I have fielded, that this is the case.

It seems it is too late to change the lame, at least not at this time and not without a lot of effort and cost. Also, a survey of current users concluded that the name “Lameness Locator” was good enough. So, for now the name will remain.

But we are always open to suggestions. Send us your ideas. If we decide later to rebrand, we acknowledge the source.

news on Lameness Locator

2011-04-10T03:53:00.000-07:00

Here is a new video and story about LL.

MU Researchers Use Motion Sensors to Determine Equine Lameness from MU News Bureau on Vimeo.

COLUMBIA, Mo. –The most common ailment to affect a horse is lameness. A University of Missouri equine veterinarian has developed a system to effectively assess this problem using motion detection. This system has been referred to as “Lameness Locator.”

Kevin Keegan, a professor of equine surgery in the College of Veterinary Medicine at MU, has been tracking horse movement related to equine lameness for years. Because equine lameness may begin subtly and can range from a simple mild problem affecting a single limb to a more complicated one affecting multiple limbs, veterinarians and horse owners know that early detection is the key to successful outcomes. The problem, Keegan says, is that detection still relies on simple visual observation with the naked eye.

“We’ve been developing objective methods of lameness detection and evaluation since the early 1990s as an aid to subjective evaluations,” Keegan said. “We started with treadmills and high speed cameras, and those worked pretty well, but they weren’t really practical due to high cost and they cannot be used in the field. Plus, horses do not move on a treadmill like they do on regular ground. In some cases with mild lameness, or in cases with multiple limb lameness, even experts looking at the same horse may disagree on whether lameness is present or on its severity. An objective method would be helpful to take some guesswork out of the evaluation.”

Working with Frank Pai, a professor in mechanical engineering at MU, and Yoshiharu Yonezawa at the Hiroshima Institute of Technology in Japan, the team developed an inertial sensor system, now in commercial use, which places small sensors on the horse’s head, right front limb and croup, near the tail. The sensors monitor and record the horse’s torso movement while the horse is trotting. The recorded information is compared against data bases recorded from the movement of healthy horses and other lame horses. These comparisons can help equine veterinarians improve and streamline their evaluation in a way they’ve never been able to do before.

“There are two reasons why the Lameness Locator is better than the naked eye,” Keegan said. “It samples motion at a higher frequency beyond the capability of the human eye and it removes the bias that frequently accompanies subjective evaluation.”

The product has drawn attention from outside the veterinary world; the National Science Foundation (NSF) has awarded a two-year Small Business Technology Transfer (STTR) Phase II Grant of $500,000 for further research and development of the current technology. The grant was awarded to Equinosis, a faculty start-up with license from the University of Missouri to develop and commercialize the product, after successful completion of a Phase I study which was instrumental in developing the prototype. Equinosis has subcontracted to the University of Missouri to complete some of the additional research. In this second NSF grant, the goals include expanding analysis to other gaits in horses, like the foxtrot, pace and canter, improving existing analysis sensitivity, developing a parallel device for horses that measures incoordination from neurological disease, improving sensor design, expanding analysis to type lameness based on diagnosis, developing sensors and expanding analysis to detect and evaluate lameness in dogs, and porting existing analysis to run efficiently on smaller computing platforms such as cell phones or iPads.

“Our biggest challenge now is to introduce this to veterinarians, train them on the proper usage and interpretation of the data, and show them that it really works,” Keegan said. More technical information can be found at http://www.equinosis.com/.

Interpreting Lameness Locator: second part of the "Law of Sides"

2011-03-07T16:17:00.000-08:00

Had a case today that supports half of the second part of the “Law of Sides”, that is, a primary forelimb lameness will sometimes cause a compensatory contralateral hind limb lameness, and that the contralateral hind limb lameness is a pushoff type. On the left are the LL results of a horse before block with a very apparent RF beginning of stance (RF = 3.7, mean head diff max=23.1 mm with a sd of 13.8 mm, mean head diff min = 67.2 mm with a sd of 6.9 mm). Notice also that he has what appears to be a LH (contralateral hind limb) pushoff and impact type lameness. Pushoff because of the red rays up on the left (LH=0.72 and mean pelvic diff max = -17.7 mm with a sd of 4.7) and impact because of the green rays down on the left (LH 0.72 and mean pelvic diff min = -10.7 mm with a sd of 3.1 mm).

On the right is the horse as PD nerve block of the RF. The RF lameness is greatly improved. RF went from 3.7 to 0.97, rays are shorter and direction of rays are different (more on this later). But, now look at the left hind limb lameness. The pushoff component is gone. No more red rays up on the left. The impact component is pretty much unchanged, i.e the compensatory component is gone and the horse really had a left hind limb lameness.

This horse has navicular disease in the RF. It has had it for some time. Horses with chronic navicular disease will developing secondary problems, pedal osteitis in the same foot being rather common. The PD nerve block eliminates the impact (in the heel) component of the lameness, but the pushoff (in the toe) component is still present.

LAMENESS LOCATOR RESPONSE IN CHRONICLE OF THE HORSE

2011-02-12T12:23:00.000-08:00

For those of you that may be interested there has been some recent discussions in a forum on Lameness Locator in the Chronicle of the Horse. I have taken the liberty of answering some of the questions that have arose on this blog platform. You can look at this discussion yourselves by going to http://www.chronofhorse.com/forum/showthread.php?t=290494&highlight=LAMENESS+LOCATOR

Here is my response to some of the questions

Ok, so I, along with my engineering colleagues, are the developers of this inertial sensor system, now called Lameness Locator. All of your comments are valid and interesting. I have taken the liberty of responding to some of your comments. I hope that this is OK.

My only complaint/criticism about the device is that one of the sensors is placed on the right front foot. However, when I asked the vet if maybe my horse was setting off the sensor by moving differently in that right front because the device is wrapped around his pastern - the vet dismissed the possibility.

This is a common and understandable question by clients of veterinarians using the device. The sensor on the right forelimb is a gyroscope. It is used only as an indicator of when the right front limb is on the ground and when it is in the air. All of the lameness evaluation comes from the signals of the accelerometers on the horse’s head and pelvis, in other words calculation of lameness severity is entirely dependent on the acceleration up and down of the torso and has nothing to do with the limbs. There is no reason to think or believe that putting a wrap on the limb will cause the torso to move up and down any more or less. In fact, we have tested this fully and putting wraps or small weights on the limbs does not appreciably affect torso vertical acceleration and deceleration. It is possible that very heavy weights placed on the limb, such that the horse has to work to lift the limb, could affect torso acceleration but the sensors used in the system weigh only 28 grams, which is inconsequential. I guess it is possible that if you really wrap the limb tight, for example so tight as to constrict blood supply, that it can cause pain and this would in turn cause lameness, but the pastern wrap that holds the sensor on the right front limb does not have to be wrapped very tight.

What started out as a lameness exam for $150 turned into a $500 vet bill after all the other tests were done to try to pin-point the lameness because the device had me worried that there was something seriously wrong. My horse was mostly sound, but exhibiting some unevenness in his collected dressage work so I assumed it was his hocks (which he has had issues with in the past), but the sensors did not detect lameness in the hind.

Unfortunately it is the mild lameness problems, that nevertheless adversely affects the horse’s performance, that are the most difficult to pin down. I have been developing and using this system for many years now and if the horse has any asymmetry in hind quarter torso acceleration, and I have no doubt that the system will pick it up. I would have to know more about why the equipment did not pick up a lameness in the hind limbs of your horse. Here are the possibilities in order of likeliness. 1) The horse actually did not have a hind limb lameness. 2) the horse has mild bilateral hind limb lameness that was “exactly” equivalent in both hind limbs. Other manipulations, like flexion tests, may help to “bring out” the lameness. The equipment, by the way, can be used to measure the effect of flexion tests.

NC State took training from the developer of the system, wonder if your vet might have problems with the settings? The problem with technology is that it is only as good as the person operating it! But I am no vet...

NC State, and Dr. Michael Schramme, has been using this equipment now for almost 2 years. He is, I think, very good at analyzing the data. There is some training that is needed so that the veterinarian can get the most out of its use. Almost everyone that has the system now has either had personal face-to-face training or an in-depth, on-line training. There are only a few that have not yet done this. The training is not in lameness evaluation, which is not needed because most of the current users of this equipment could teach me a thing or two about lameness, but only in interpreting the analysis.

I also wonder if this type of equipment is more suited to significant lameness, localized to one leg. It would make sense, finer level of lameness hard to register, multi leg--confounding data. Also, if equally sore in hind legs, it would counter the numbers I would think...

I disagree. It is most beneficial for horses with mild lameness or in horses with apparent multiple limb lameness. It is designed for these types of cases. However, we now use it on every horse that comes in for lameness evaluation, for 3 reasons. 1) When you see the results on horses with easy lameness or in sound horses you rapidly gain more in-depth understanding of the analysis results, especially when using on horses while lunging and after flexion tests. 2) Sometimes what looks like an easy lameness in the beginning turns out (after blocking) not to be so easy and we wish we would have had the pre-blocking baseline against which to compare. 3) It takes too much time to run back into the clinic to get the equipment after we first decide that it is a case where it might be useful. The students and technicians in our practice are trained to “instrument” the horse right away. It takes only 3 minutes. Sometimes they are so fast that I may not even had time to palpate the horse first (something I always like to do first) and I have to remove the pelvic sensor because it gets in the way of my complete lameness palpation. I highly recommend to those who are using the system to, at least during the beginning weeks of use, put in on every lameness, pre-purchase, and “not performing right” case they evaluate.

It is theoretically possible for horses with bilateral lameness to be exactly equivalent in pain of lameness on every stride, but this in reality almost never happens. Navicular disease (for forelimb lameness) and distal tarsal arthritis (for hind limb lameness) are the most common culprits. However, for both these conditions and others that are frequently bilateral, the most common situation is one side is a little worse than the other. So, for example a horse with an average grade 3 lameness in the right front and an average grade 2 lameness in the left front will be measured as an average grade 1 lameness in the right front. This is a limitation of any objective method of lameness evaluation that evaluates asymmetry as a measure of lameness. Another situation that is much more common than a bilateral lameness that is exactly equivalent one side versus the other on every stride, is a bilateral lameness in which the lameness switches sides, back and forth sometimes several times during the same evaluation. In this case the thresholds between soundness and lameness may be reached for each limb. However, this will be displayed in the plots provided and this is perhaps when having more experience with analysis of results may be important. Also, for horses with bilateral lameness, veterinarians utilize other evaluations (other than just evaluating the horse trotting back and forth) like lunging and flexion tests to help “bring out” the lameness, one side compared to the other.

if my horse had improved with each nerve block I might have been much more convinced that it was his front right, but even after blocking everything from the knee down, he was still registering 0.446 (0 is the threshold.)

His hocks, however, which we know he has issues with - OCD, surgery, arthritis, etc. - only registered .152 which is only slightly above threshold and the vet said those numbers probably indicate stiffness and not lameness.

There are actually more than one value reported to the veterinarian that they should take into account when evaluating the results and not just the threshold value that you allude to. A horse can be lame when it is under the threshold if the variability in asymmetry is quite low (a very mild but consistent lameness) and the horse can be sound when it is over the threshold if the variability in asymmetry is quite high (data too variable to make a valid conclusion). There is by the way no threshold reported by the system that is normally “0”. I am pretty sure that your vet using the equipment understands this and it may have just been communicated in this fashion as a simplification.

Yeah, if the vets had walked out and said, 'this instrument is going to decide whether or not your horse is lame and needs surgery', I would never have gone for it.

I hope this never happens and I doubt that any current users would do this.

I wonder how the device deals with acceleration asymmetry in the horse's gait due to limb length disparity or high/lo hoof pairs.

This is an excellent observation and one that we have also thought about a few years back. We have tested this experimentally by artificially creating limb length and hoof angle asymmetry in both forelimb and hind limbs. It turns out that induced limb length asymmetry or hoof angle asymmetry in the front limbs has no to very little effect on torso vertical movement asymmetry in the short or long term. It seems that the soft tissue sling connecting the limb to the vertebral column dampens this effect. Induced limb length or hoof angle asymmetry in the hind limbs will affect results, but only in the short term (hours to days). After a few days of induced limb length or hoof angle asymmetry the effect on vertical torso acceleration not measurable. I do not know exactly how the horse does this, but it does.

but it's not meant to replace an experienced practitioner by any means.

Absolutely. It is not meant to and in fact cannot replace the experienced practitioner. Equine veterinarians and anyone else who knows much about lameness knows this. It is only a very sensitive aid.

We did have one set of results that we questioned turn out to be due to the fact that one of the sensors was a bit loose and moving a little on its own though...it kind of created a 'back ground' noise

The gyro data on the right front limb is remarkably resistant to “noise” created by jiggling in the pastern wrap. We filter the gyro signal. It can however, cause erroneous results if it rotates on the limb. If it rotates 90 degrees to the side of the limb you may not actually get any results. If it rotates all the way to the back of the limb you will get “opposite-of-true” results. The algorithms (a fancy word for “rules” or “equations”) depend on the gyro being positioned on the front part of the right forelimb. Putting them on any other limb will give erroneous results.

Or the vet I know of who kept saying one leg was lame when that foot had an egg bar on it and the other foot did not.
All can say is there is no substitute for well trained eyes and ears (oh wait..those are lots cheaper)

Limb length asymmetry, especially as small as that cause by a shoe on one foot, will not affect results. See above comments. There definitely is no substitute for well trained eyes and ears. Well trained eyes and ears do much more than evaluate the motion of the horse. Well trained eyes and ears evaluate the entire horse.

There is a HUGE presumption that asymmetry of amplitude = pain.

No "baseline control" mechanism to rule out other factors which can and do cause asymmetry in amplitude. I didn't even think about that. That could be a very valid threat to the reliability of the test.

This was, indeed, a huge presumption early on in development. However, disregarding foals and yearlings (young horses in general), which sometimes show dramatic “handedness” or natural asymmetry, it turns out that horses trotting in straight lines have remarkably symmetric vertical torso acceleration and deceleration when they are sound even when their limb movement is quite asymmetric. The same cannot be said about lunging. I am not saying that there are no horses out there that are sound but display significant asymmetry in vertical torso acceleration but they are uncommon.

I'm curious how a sensor on one leg could detect lameness in all four? I could understand if there was a sensor on each leg, but it seems a little weird to me with only one.

The gyro sensor has to be put on the right forelimb. The algorithms depend on this. The gyro sensor does not detect lameness. The gyro sensor just indicates when the right forelimb is on the ground and when it is in the air. All other limb placement can be approximated (which is all that has to be accomplished for the algorithms to function correctly) if the gait is known. If you put the gyro sensor on the left front limb it will give “opposite-of-true” results. I do not really know what would happen if your put the gyro sensor on the hind limbs. Probably it would give correct results if you put it on the left hind limb and “opposite-of-true” results if you put it on the right hind limb, but I have not done this specifically.

The MARKETING is aimed at folks who aren't engineers.

Actually right now there has been no real marketing to date, just word of mouth. When it is marketed it will be marketed only to equine veterinarians.

TOP 10 THINGS NOT TO DO WITH LAMENESS LOCATORTOR

2011-01-21T14:25:00.000-08:00

1. 1. LOOK AT THE COMPUTER INSTEAD OF THE HORSE. Owners appreciate and are highly interested in the extra measure of objectivity supplied by Lameness Locator, but not at the expense of your expert opinion. Lameness Locator will never substitute for skilled and experienced observation of the horse in motion. Look at the horse when it is moving. Refer to Lameness Locator’s results as an aid. Viewing the raw sensor signals as they are coming in is designed only to let the user know that the signals are being acquired correctly and it only takes a few seconds of viewing to see this. Studying Lameness Locator results without watching the horse is sort of like evaluating an ECG without auscultation of the heart with a stethoscope.

2. USE LAMENESS LOCATOR ONLY ON HORSES WITH DIFFICULT LAMENESS. Using Lameness Locator on every lameness evaluation is good practice. Understanding results from easy cases and in sound horses is a stepping stone to understanding results in difficult, mild cases, cases with compensatory movement patterns, and when evaluating the horse during the lunge. Performing standard, subjective evaluation and then only later deciding to use Lameness Locator wastes time. Running back into the clinic to get the sensors and computer, instrumenting the horse as an afterthought, and having to trot the horse up and down a second time takes too much time. Also, some cases which at first seem easy, may not be so easy after blocks and collecting a baseline evaluation before treatment or surgery can give you a benchmark against which to compare later during rechecks.

3. LOOK AT RESULTS FROM LUNGING IN ONE DIRECTION ONLY. Reported thresholds between lameness and soundness do not hold and are inaccurate for evaluating the lunge. Evaluate the horse lunging in both directions as separate trials and then use Lameness Locator’s dual reporting capability to compare lunging in one direction side-by-side to lunging in the other direction. Study and become well-acquainted with expected normal patterns of head and pelvic movement while lunging.

4. PUT THE GYROSCOPIC SENSOR ON ANY OTHER LIMB OTHER THAN THE RIGHT FORELIMB. Results will be wrong. If placed on the left forelimb results will be opposite of true.

5. FAIL TO CHARGE THE SENSORS DURING PERIODS OF PROLONGED INACTIVITY. Sensor batteries will leak charge slowly when not used during storage and fall below the minimum voltage required for Lameness Locator’s safe battery charger to function, requiring you to send the sensor back to Equinosis for recharging. NOTE: Generation 2 sensors, due out in February 2011, can be re-charged from 0 volts with the generation 2 safe battery charger, i.e. this problem will be mute with generation 2 sensors.

6. FAIL TO CHECK TO SEE IF THE RIGHT FORELIMB GYROSCOPIC SENSOR ROTATES TOWARD THE BACK OF THE LIMB. If the right forelimb sensor rotates toward the back of the limb results will be compromised, yielding either odd or opposite-of-true results. Sensor rotation on the right forelimb occurs most commonly when horses are moving vigorously with animated forelimb movement, especially during the lunge. A good prevention is to place 1 throw of Elasticon tape around the top edge of the pastern wrap before collecting data.

7. FAIL TO CHECK TO SEE THAT THE HEAD ACCELEROMETER IS ON THE HEAD, THE PELVIC ACCELEROMETER IS ON THE PELVIS, AND THE GYROSCOPIC SENSOR IS ON THE RIGHT FORELIMB. Misplacing sensors in the wrong positions will yield strange results.

8. FAIL TO CHECK TO SEE THAT THE RIGHT FORELIMB GYROSCOPIC SENSOR IS PLACED IN ITS PROPER ORIENTATION ON THE RIGHT FORELIMB (LABEL OUT AND LED UP). Upside down or backward orientation of the pastern sensor will yield results that are opposite of true. NOTE: Generation 2 sensors should be positioned with label out and LED towards the inside of the limb.

9. GET THE RIGHT FORELIMB GYROSCOPIC SENSOR DIRTY OR WET. Getting water into the gyroscopic sensor’s 3-pronged battery charging port (rain, puddles, and fluids from blocking the right front limb) will short out the sensor battery and destroy the sensor. Getting dirt, dust, or fine sand into the 3-pronged battery charging port will plug the port and potentially prevent future charging. A good measure to protect the right forelimb sensor is to place a single piece of duct tape over the opening before placing on the right forelimb. Turn the sensor on first.

10.

10. BLOCK OR COVER THE LITTLE BLACK ANTENNAE ON THE USB RECEIVER. Blocking the antenna, for example using a USB extension cord and taping the receiver to the back of the tablet PC (to protect the USB plug from damage), will augment surrounding RC interference and either significantly decrease range of transmission or prevent transmission altogether. The first symptom of interference will be lack of synchronicity or simultaneous tracking of all 3 sensors. To prevent damage to the USB receiver sticking out of the side of the tablet PC use an extension USB elbow. These are inexpensive and can be purchased on line (http://www.google.com/products/catalog?hl=en&rlz=1C1GGGE_enUS356US362&biw=1024&bih=653&q=flexusb&um=1&ie=UTF-8&cid=9608387493089874738&ei=LFo2TaPvGIL6lwfWyumQAw&sa=X&oi=product_catalog_result&ct=result&resnum=2&ved=0CF8Q8wIwAQ#) or directly from Equinosis.

CHANGING SELECTION OF TROTTING STRIDES

2011-01-17T09:10:00.000-08:00

I made this movie to describe how to change the delta value when LL does not select desired trotting strides. This happens only occasionally but is good to know, especially for use after flexion tests when rarely no strides are selected by default. Click on this link Adjusting Delta in Lameness Locator

when to use Lameness Locator

2011-01-15T12:22:00.000-08:00

Some have asked me how I used Lameness Locator. I have been practicing and looking at lameness in horses for 28 years now. For many cases that I look at, I think I am pretty certain which leg they are most lame in just after seeing them trot up and down in a straight line for a few strides. So, one would think that I would think that Lameness Locator is only good to use on those few cases in which making the decision of the most lame limb is difficult or when the lameness is so mild that even picking it up and differentiating lameness from other causes of poor performance is difficult. After using this equipment for many years I realize that it is difficult to predict when the information provided by Lameness Locator will be beneficial to me.

So, I use it on all lameness cases and pre-purchase evaluations presented to me. There are 3 distinct advantages to this approach. 1) You learn how to use the equipment and how to interpret the report better and faster. Seeing results of obvious cases, lame and sound, reinforces understanding of the plots and lameness variables so that, when the difficult case is encountered the user can interpret better and in more depth the Lameness Locator report. For example, peeling out the meaning of ipsilateral and contralateral lameness, compensatory lameness patterns, the expected patterns when lunging the horse on hard or soft surfaces, etc. 2) Sometimes I just do not know when the Lameness Locator data will be valuable. Maybe the lameness is obvious but response to blocks afterwards will not be. Maybe I want to show the owner that the horse is lame in the left hind but they think it is lame in the left front. Maybe I want to follow the horse later after treatment and I need a baseline to compare to. 3) Evaluating a horse subjectively first and then only later using Lameness Locator takes too much time, especially if you have to bring the horse back in somewhere to instrument, or you have to run to get the sensors and computer to some other area of the clinic. If it happens to become a case when the data is not that valuable, let us say for an obvious lameness (like a horse presenting for removal of carpal chip or even a horse with a obvious tendon injury) so be it, I have not wasted much time just getting the data. Besides, I may want to look at the horse post treatment anyway.

Here at the University of Missouri it has just become the standard of lameness evaluation. Of course the clinicians still evaluate subjectively and look at the horse when it is moving (and not the computer). Everyone (technicians, clinicians, some students) are trained to instrument the horse, collect data and work through the software. The clinician basically does her/his lameness evaluation and then looks over in between trials (straight line trot, lunge, etc) to see the results. After all it only takes about 3 minutes to instrument the horse and a few seconds to evaluate data for each trial. After using it for some time I can honestly say that my lameness evaluation is not lengthened because of using Lameness Locator. In many cases, because I can measure the lameness more clearly, let us say during a straight line trot, the lameness evaluation is actually shortened, because I may not have to lunge the horse to bring out the lameness.

NEW SAVE FUNCTION IN LAMENESS LOCATOR

2010-12-25T10:58:00.000-08:00

A new function is coming to the Lameness Locator interface that will allow much easier saving of results to show the owner or to incorporate into existing medical record management software. After viewing the LL report and then closing to continue the user will be presented with the this window. It is querying the user to ask if they want to save the pdf file of the report into a particular location with a particular file name. The most likely selection for users will be OK. Selecting OK will save the pdf file with a descriptive file name (or easier location later) starting with the owners's last name and including the horse's name and any other information added about trial information. This file will be automatically saved in the Documents/Equinosis/Lameness Locator 2011 folder in a self-generated subfolder with the owner's name, and in a self-generated subfolder with the horse's name. NO MORE PECKING AWAY AT THE ON-SCREEN KEYBOARD TO SAVE A FILE!!!!!!!!!!!
So, just select OK. Remember to back up and then empty your Documents/Equinosis/Lameness Locator 2011 subfolder occasionally.

2010-12-20T11:13:00.000-08:00

For those who have commented that it takes too long to put the sensors on the horse, I made this video. I have always told people that the horse can be instrumented in less than 5 minutes. I was wrong. I can instrument the horse in less than 3 minutes

Adam and Stashak's Lameness in Horses

2010-12-10T22:10:00.001-08:00

Coming out in February, in chapter 3 (Examination for Lameness; Objective Assessment of Lameness) there is an in depth description of using inertial sensors for evaluation of lameness in horses. In this chapter much of the description concerns Lameness Locator. There are descriptions of "Detecting forelimb lameness", "Detecting hind limb lameness", "Detecting Compensatory Lameness", "Using LL to Quantify Response to Flexion Tests", and "Using LL to Evaluate Lameness during the Lunge". Current users will find these descriptions helpful. I would highly recommend it for your libraries.

what one right hind limb lameness looks like lunging

2010-11-24T22:09:00.000-08:00

I thought I would show an interesting case with results of LL. It is interesting because of the results of lunge and flexion test evaluations and because of a strong definitive diagnosis based on bone scan.

The case is a 6-year-old QH filly with a 2 month history of lameness. The owner acquired the horse 4 months prior to presentation with the hopes of turning it into a barrel racer. The horse was previously a race horse. The owner suspected something wrong when the horse started balking at taking the right lead and becoming difficult when riding the horse in a circle to the right. Previous veterinary examination did not detect lameness and resulted in a suggestion that the problem was behavioral. Our visual and palpation examination revealed very little. The only physical examination abnormality was a slightly lower tuber sacral on the right compared to the left when the horse was standing squarely on both hind limbs. Everything else was normal. Visual evaluation at the trot in a straight line indicated, maybe, a mild right hind limb lameness.

LL results are in the first report above.

LL report indicates a right hind limb lameness, primarily of the pushoff type (MAXDIFFPELVIS = 5.2 mm, threshold is +/- 3 mm). There may also be a very, very mild left forelimb lameness because MINDIFFHEAD (-6.7 mm) is barely outside threshold (+/- 6 mm). The right hind limb lameness is more important.

The 2nd report above is a dual report with lunging to the left on the left and lunging to the right of the right. While lunging to the left the horse has variable vertical head movement but there is no pattern indicating consistent asymmetry (star pattern). While lunging to the right the horse is showing a very mild left forelimb pushoff type asymmetry. This is not an unexpected pattern, but may be an indication of a very mild left forelimb lameness, which is consistent with the straight line evaluation. What is most interesting is the vertical pelvic movement patterns while lunging.

The pattern on the left (lunging to the left) is a normal expected pattern, an inside hindlimb impact type asymmetry (pelvis moves down less during stance) and an outside hind limb pushoff asymmetry (pelvis is pushed up less after stance). The horse does not have an impact lameness on the left hind limb and a pushoff type lameness on the right hind limb. I remember like so. The horse is moving in a counterclockwise pattern and the rays (green pointing down on the left and red pointing up on the right) point in a counterclockwise direction. The pattern on the right (lunging to the right) is not a normal expected pattern. The impact asymmetry on the right hind limb (pelvis is moving down less during the right stance phase) is normal. The horse does not have a right hind limb impact lameness. However, the horse does not have the same expected pattern in the left hind limb (less upward movement of the pelvis after pushoff of the left hind limb) like it shows in the right hind limb while lunging to the left. This is because the horse has a push off type right hind limb lameness, which is overwhelming the expected pattern in the left hind limb.

Remember the lameness value magnitudes do not matter too much when evaluating the lunge. The most important thing to evaluate are the patterns.

The horse also had a positive right hind limb flexion test. Note in the 3rd dual report above that the MAXDIFFPELVIS increased from 6.6 mm before flexion to almost 11 mm after flexion.

This horse subsequently had a bone scan. There was increased uptake in the right sacroiliac joint.

Do not cover the antennae

2010-11-23T20:14:00.002-08:00

Obstruction of the antennae on the bluetooth receiver plugged into the USB port of the tablet computer will adversely affect transmission from the LL sensors. This may cause a decrease, at the minimum, in the range of the LL sensor transmission. Worse yet, obstructing the antennae, may cause lack of synchronicity between channel transmission such that the different sensors (head, pelvis, right front pastern) may begin data collection at different times. This will cause the LL algorithms to dysfunction and give odd results.

The bluetooth receiver plugged into the USB port sticks out to the side. In this position it is susceptible to breakage at the USB prong. We have had to replace a few of these receivers at some sites, at a cost of about $40/receiver. As an attempt to prevent this, one user has found a flexible USB to USB cable, allowing them to tape the bluetooth receiver to the back of the tablet computer, effectively getting it out of the way of harm. Unfortunately placing the antennae of the receiver up against the back of the tablet PC can obstruct the antennae, which can result in lower range of transmission and defective transmission with lack of channel synchronicity. So, don't do this.

As an alternative, you can purchase a USB port elbow. This will get the USB prong of the bluetooth receiver up and out of the way to prevent damage, yet keep the antennae sticking up for unobstructed transmission. If the USB port elbow breaks it is only a few bucks ($3-$7).

d

2010-11-23T20:14:00.001-08:00

2010-11-22T14:11:00.000-08:00

Dr. Nick Kleider sent me this the other day. His observation was that the horse measured with a greater lameness (forelimb and hindlimb) when trotting fast than when trotting slow. Attached is the dual report of the horse trotting slow (left report) and trotting fast (right report). I would agree with this observation.

1. A1/A2 ratio of RF increased from 0.42 to 1.16. This is a very large change. A better indicator, however, is the increase in the HEAD DIFF MIN from 5.8 mm (just below threshold) to 11.5 mm (above threshold).

2. A1/A2 ratio of LH increased from 0.18 to 0.53. This also is a very large change. The absolute value of PELVIS MAX DIFF also increased from -2.2 mm (below threshold) to -5.7 mm (above threshold).

You know that the report on the right is from the horse when trotting faster since the stride rate is 1.67 strides/second and only 1.33 strides/second on the left. This is fairly large difference in trotting speed. A change in lameness with a large change in speed should not be unexpected. Other laboratories, using objective methods of gait analysis, have found this to be the case. The ironic thing, however, is that sometimes the lameness is worse at higher speeds and sometimes lameness is worse at lower speeds. Knowing which lameness conditions are more likely to be worse at higher speeds and which are more likely to be worse at lower speeds would probably be very valuable to the clinician in the field, but as far as I know this information has not been uncovered. Besides type of lameness, the severity or extent of pathology, probably has something to do with it also.

My guess is that this horse has both a mild right forelimb lameness and a mild left hind limb lameness. Without additional info (like results of lunge or flexion tests, very careful palpation of the limbs) it is a tossup to decide which one to go after first.

Thank you Dr. Kleider for sending this.

A start

2010-05-16T16:50:00.000-07:00

Last night I started this blog at the urging of a friend of mine. The goal of this blog will be to serve as a posting board for opinions and helpful tidbits from current Lameness Locator users. I think it would be a good idea also to post case material to share with everyone (please do not post material with horse or owner identifying information). I will contact all current Lameness Locator users about the new existence of this blog. Occasionally I will give my opinion about how to properly use Lameness Locator, how to use Lameness Locator in specific instances, like during the lunge or after flexion tests, how to interpret compensatory lameness patterns, etc. I will also sometimes speak out about what I consider a "Luddite-like" response from some veterinarians who seem hostile to (at the worst) or very skeptical (at the least) about the idea of Lameness Locator and objective lameness evaluation in the horse in general. I know that there are some out there with misinformed or under-informed opinions about Lameness Locator, how it was developed, how it works, and what its inventors claim it can do. This blog may also be useful for veterinarians who may be interested in learning more about Lameness Locator.

It may take me some time to learn this blog interface, so be patient with me. In the mean time, it would be great if any current users were to start it off.

I will try to post at least one comment every day, even if it is but a single line.

Today, was born my Lameness Locator blog.