SEPTEMBER 2017 THE RIDER /17 Laminitis - Compromised Suspension & Support


By Dr. Bri Henderson BVMS MRCVS ACVSMR-resident Cheltenham Veterinary Centre, Caledon, Ontario 905-838-3451 I don’t know anyone


that would disagree that this summer has had an odd weather pattern. Fluctua- tions of cool/wet weather with short spikes of heat and humidity have contributed to an increase in the number of laminitis cases then we would typically see during this time of year by driving up the sugars in the pasture. Laminitis accounts for


approximately 15% of lameness issues in horses… . But what is it? Simply, laminitis is an inflammation of the laminae within the foot of a horse (think of walking on a finger with a blood blister). Laminae can be found covering the entire surface between the hoof capsule and the coffin bone. It forms a tight bond that is able to withstand up to 4500lb on a single foot dur- ing athletic competition. The laminae are designed to be able to be an equal and opposite force to the pull of the deep digital flexor ten- don (DDFT). The DDFT runs down the back of a horses’ leg and attaches to the bottom (solar) surface of the coffin bone. Like any big elastic, it wants to “re- coil”. Without the opposing force of the laminae, the DDFT would be able to pull the tip of the coffin bone downwards, out of the hoof capsule. In laminitis cases where the laminae are so damaged that they can no longer oppose the DDFT, the coffin bone rotates and sometimes sinks, resulting in “Founder”. See Figures at right. The tip of the coffin


bone has been remodelled and blunted over time. This gives it the “ski tip” appear- ance.


What causes laminitis? The most common


cause we see is obesity and insulin resistance. The char- acteristic image is of an in- sulin resistance pony that has a thick cresty neck and large fat pads behind the shoulders and on the rump. While this holds true, a more subtle body condition type has emerged within our sport horses where they de- velop fat pads over their rib cage. These horses often do not have the top line that their level of work suggests they should have and can be “flat backed” under the sad- dle.


How is it possible that


insulin resistance and ele- vated blood glucose causes laminitis? There are a few things happening that make these horses more likely to have issues…. (1) When the fat storage cells reach max- imum capacity they get stressed and release a sub- stance that is inflammatory to the body. Anything that creates a chronic underlying inflammation within the body sets that organ up to be “at risk” for major disease.


(2) Under normal circumstances, insulin would tell the cells to suck up the glucose from the blood for energy and their own nutrition. Because the cells aren’t listen- ing to the insulin’s signal to pull glucose inside the cell, they end up starving and unable to function properly. (3) Insulin causes blood vessels in the limbs to contract (get smaller). This reduces the blood flow to the foot and further reduces the supply of fresh oxygen and nu- trition. Infection or sepsis is another major cause of acute


laminitis. As I write this article, cases of Potomac Horse Fever are popping up around Ontario. This dis- ease causes a significant colitis/diarrhea. As we dis- cussed in last month’s article - when the large colon is inflamed, it becomes leaky and allows bacteria and tox- ins to enter the body’s blood stream. In addition to the systemic (whole body) inflammation, these toxins also


attack the laminae and cause lamini- tis which can be severe and life threatening. Any case of significant diarrhea/colitis puts the horse at risk to develop laminitis. During foaling season you will notice that two words that get your veterinarian out ASAP is “Retained Placenta” in a broodmare. The reason for the panic is that the retained placenta begins to effectively decompose within the uterus and creates a significant in- fection that easily reaches the blood stream. Similar to the colitis sce- nario, once the bacteria and toxins are in the blood they create systemic inflammation and gain access to the laminae in the feet. Less common causes of


laminitis include mechanical or “Support limb” laminitis. Remem- ber that the blood supply to the foot is dependent upon the horse walk- ing around. They were never de- signed to stand still in stalls. In horses with a prolonged severe lameness on one foot are naturally going to put more weight on the op- posite foot. The constant pressure on the limb reduces blood flow to the laminae and starves the tissues of oxygen. The result is a build up of “cell garbage” (like lactate) that creates inflammation and therefore, laminitis. We all remember the magnificent race horse “Barbaro”. In the end it was his “good foot” that became compromised from bearing the load while his fracture was healing. The resulting support limb laminitis created a situation where euthanasia was the best op- tion for him as he literally didn’t have a good leg to stand on any- more.


Acute versus Chronic Laminits Acute laminitis often results


Fig. 1 A normal foot with anatomical labels (Lancaster, Animals 2012)


from some form of systemic insult (infection, grain overload, pasture associated) that damage the lami- nae. Horses’ are often found in the typical “saw horse” stance where they have rocked backwards onto their hind limbs to relieve pressure on the toes of their front feet. They are often reluctant to walk and very painful when asked to turn in a tight circle. The feet may feel hot to the touch and the digital pulses are often easily palpated or “bounding”. Control of inflammation and sup- porting the hoof are the keys to re- ducing the exposure of the laminae to the damaging substances and controlling the severity of the laminitis attack. In contrast, chronic laminitis


Fig. 2 A chronically laminitic foot with rotation of the coffin bone.


horses have a mechanical issue which must be managed in order to prevent an acute attack to occurring and to maintain soundness. Chemi- cal treatment has a secondary role in chronic laminitis cases. Support of the foot and ensuring a balanced trim to reduce mechanical stress on an already compromised foot.


Treatment of acute laminitis. As mentioned earlier, in acute


laminitis cases, the immediate goal is to control and reduce inflamma- tion systemically and in the feet. This can be accomplished by Non- steroidal


inflammatory drugs Fig. 2b The bony column of a chronic laminitis pony.


(NSAIDs) like phenylbutazone or flunixin (Banamine). Personally, because so many of these cases are due to some sort of systemic inflam- mation/bacterial toxin exposure, I prefer using Banamine in my cases because at a 1/2 dose it has an “anti endotoxin” effect. In addition to anti-inflammatory drugs, the judi- cious use of ice therapy during the first 72 hours is of great benefit. Using 5L IV fluid bags filled with ice and water (secured using Elasto- plast) is a more straight forward way of icing feet safely. The key to


Fig. 3a + 3b: A chronically laminitic pony’s foot. Notice how distorted the hoof capsule is in 3a and the moth eaten (demineralized) edge of the coffin bone in 3b.


is maintain submersion in ice water con- tinuously for 48-72 hours. Ensuring that the foot is balanced


and removing any excess toe length helps to reduce additional mechanical forces on the inflamed structures. Once the foot is balanced, solar support through the use of therapeutic boots with impression material packed into the back 1/2 of the hoof (sulca and frog to the heel bulbs) is the easiest way to take the pres- sure off the toe area and improve com- fort in the patient. Alternative options include using heart bar shoes or wooden clogs with impression material packed in the back half of the foot. The most im- portant point to make is that each case is individual and must be managed as its own entity. What works for one case, may not work for the next. In cases where pasture associated


laminitis or insulin resistance is sus- pected as the cause, a drastic reduction of calories is also involved in the initial management.


Management of chronic laminitis. Maintaining the hoof balance


through frequent trims (every 4-5 weeks) +/- mechanical support through boots or shoes is the foundation of managing these cases. Nutritional management through the use of low non-structural carbohydrate diets (NSCs/sugar) and supplementation with omega fatty acids is beneficial. I think we underestimate the impact of our hay on laminitis cases. Testing your hay to determine exactly what you are feeding is key. Many cases that have been well managed and sud- denly find themselves in an active laminitis attack when “nothing has


changed” can be traced back to starting a new hay source which had sugar levels far greater than the previous source. Never underestimate the nutritional con- tent of your hay. Controlling and managing any un-


derlying diseases will also be critical. For example, insulin resistant horses often do best in dirt paddocks or turned out in grazing muzzles to reduce their in- take. Exercise also plays a key role in improving insulin sensitivity as much as possible. Recent studies from the U.K. established that 30-40 minutes of mod- erate exercise (sweaty and out of breath) 3-5 times per week was the most benefi- cial.


Managing acute and chronic


laminitis cases is most successful when the owner, farrier and veterinarian work as a team. Radiographs, blood work and nutrition consults/modification are the most common aspects of my role as a veterinarian, but without a knowledge- able farrier to balance and monitor the foot while it stabilizes, our chances of success diminish. Equally, the owner must be on board with the management required. The temptation to feed treats and the feeling of being ‘cruel’ by using dry paddocks and grazing muzzles is something all owners struggle with in the beginning. If we can focus on the ‘long game’ and the result of stabilizing the hoof and maintaining soundness in our patients then the end often justifies the means!


tact


For more information please con- Bri


Henderson sportsmedvet@gmail.com at


Dealer


Inquiries Invited!


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