Supporting Limb Laminitis Has Been the Undoing of Many Seriously Injured Horses—But That May Be Changing
byTori Repole| Jan 18, 2018
In 2006, nearly a decade before American Pharoah became the first Triple Crown winner in 37 years, a promising Thoroughbred colt by the name of Barbaro embarked on a journey with the intent of doing the same.
A catastrophic leg break sustained during the Preakness Stakes on May 20, 2006, brought Barbaro’s racing career to a tragic end, though it would ultimately be Supporting Limb laminitis, developed while being treated for his injury, that felled the Triple Crown favorite less than one year later.
The University of Pennsylvania’s New Bolton Center treated Barbaro throughout his treatment, and the facility continues to be a spearhead in laminitis research to this day. Dr. Andrew Van Eps, a resident in Large Animal Medicine at the time of Barbaro’s stay, is currently an Associate Professor of Equine Musculoskeletal Research at New Bolton Center. Below, the renowned veterinarian discusses the progress made in understanding Supporting Limb laminitis, as well as possible treatment and preventative measures of the future.
NF Style: What are the common forms of laminitis?
Dr. Andrew Van Eps: In 2006/2007, we still thought laminitis was all the same; regardless of what was causing it, we [believed] we were looking at one problem. It wasn’t until 2007/2008 that we started to realize [that] the different types had different pathways. The three common types of laminitis are:
- Supporting Limb, where we recognize the horse is putting too much weight on a limb for too long.
- The most common form world-wide, Endocrinopathic, is caused by endocrine disease. The mechanisms that lead to that seem to be directly related to the over production of insulin in the body. A direct action of insulin on the tissue in the foot causes it to fail.
- Sepsis-Related laminitis most commonly occurs in horses that are septic and have a systemic disease caused by infection or bacterial proliferation in the gut. Horses that have diarrhea, pneumonia, placentitis, or other kinds of systemic infections [can] get acute laminitis.
“We started researching Supporting Limb Laminitis in 2009 and a lot of what we’ve done has been a direct result of Barbaro.”
We can prevent [Sepsis-Related] laminitis just by cooling the feet when [a horse is] sick. Even though we’re still working on exactly why it happens and why the cooling works, we are able to prevent that form if the animal is in a situation where their feet can be continuously cooled.
Why does Supporting Limb Laminitis occur?
There is new evidence — from our group and some of our collaborators — that it’s a blood flow issue.
We started researching Supporting Limb Laminitis in 2009 and a lot of what we’ve done has been a direct result of Barbaro. What we found over this time is that it does appear that a reduced blood flow to the lamellar tissue — which joins the hoof to the bone — is the primary reason horses develop supporting limb laminitis.
Horses are very reliant upon cycling their leg load between limbs and they cycle their weight between front limbs about once a minute, even if they’re standing still. They increase their blood flow to the lamila tissue quite profoundly at the walk, though even just leaning their weight from one side to the other tends to maintain the blood flow in the tissue.
It seems that the combination of increase in absolute weight on a leg, and a decrease in the number of times they cycle their weight off that limb, is what tends to lead to Supporting Limb laminitis in horses that have a painful problem in the opposite limb.
The problem is that, when a horse has a fracture like Barbaro on one leg, the only way to approach getting the weight off the opposite leg is to either put the load back on the fractured leg, which a surgeon isn’t very keen to do, or [to] look for another way. Our research has also shown us that it may only be partial weight that we need to relieve off the supporting leg, and it may only need to be intermitted relief of that partial weight, if done in the correct way.
We’re focusing on methods of tracking how often [a horse is] cycling the load on their legs in order to get an early identification or warning indicator that we’ve got a problem in a horse. The second thing we’re focusing on are methods of how to increase the load cycling and reduce the weight, and there may be a couple of different options.
What methods could potentially help stabilize the load cycling and weight distribution?
There are a couple devices under testing here [at New Bolton Center] at the moment, but the other way is to potentially use slings. In the past, slings have always been all or nothing. The horses either slump into them, they’re lifted right off the ground, or they’re just wearing them like a jacket, and it’s not really doing much. There are new developments which add a dynamic component to slings which may be useful for partial load relief in these horses.
“I don’t think it’s going to be a pharmacologic drug treatment. I think it’s going to be a physical manipulation.”
I think the ability to use a dynamic sling to intermittently relieve partial weight off a supporting limb — and not put it back on an injured leg — is something that will potentially come into the realm of clinical use in places like this hospital.
Fairly basic physical manipulations, like physical therapy, might be something we could use clinically, even if it’s very slow and controlled.
How frequently does Supporting Limb laminitis form in a horse with a significant leg injury?
There has really only been one study that’s looked at the frequency with which it happens, and that was a study that looked at horses who had casts on their legs in a hospital environment. In that population of horses, about one in 10 developed supporting limb laminitis. The problem with this form of laminitis is that once horses develop it, the morality approaches 100 percent.
Can you talk about the innovative Robotic CT and how it will further efforts against Supporting Limb laminitis?
It’s exciting to have a method of three-dimensional imagery in a standing horse. We previously had to anesthetize horses for CT [Computed Tomography] or MRI [Magnetic Resonance Imaging] scans of the leg, so it opens up massive possibilities. It’s quite rapid and so sensitive that it can actually help identify pre-existing problems in a horse that perhaps were impossible [to detect] before without a major undertaking.
We’ve done a lot of CT scans to look at load and blood flow but we’ve had to do it on cadaver legs; we couldn’t do it on a live horse. Now that we can image them standing, we can inject a noninvasive contrast agent to look at blood flow on the different loads on a normal standing horse, which was never possible before.
We’re very excited about using the Robotic CT to actually study blood flow to the foot in the standing horse for the first time.
In five years time, where do you see the veterinary community on the topic of Supporting Limb laminitis?
I see us being able to identify horses that are truly at risk of developing the disease.
I am collaborating with a biomechanics expert at the University of Delaware and we are looking at using accelerometer devices. These accelerometer sensors are small, sensitive, and wireless, and you can place them on the limb of a horse.
If we can come up with an algorithm that identifies an instance of unloading on a leg, then we can actually count the frequency. You can then log that in a clinical patient, set a threshold, and say, “I want to know when this horse is [unloading] less than 60 times an hour.” Once you get alerted to that, you can make sure the horse gets walked X number of times, or you can apply a device or put [the horse] in a dynamic sling that is going to unload that leg once a minute.
This is what I foresee happening to this form of the disease. I don’t think it’s going to be a pharmacologic drug treatment. I think it’s going to be a physical manipulation. [The] data from our research is showing that it’s achievable in clinical practice.
-Photos via PennVet.
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