Making Sense of Laminitis

Photo: Raul Bras, DVM, CJF

Farriers and veterinarians discussed ways to work together to treat this devastating hoof disease.

Laminitis, also referred to as "founder," is an often devastating disease of the hoof that can cripple or kill afflicted horses. It's such an important equine disease that each year veterinarians, farriers, and horse owners from throughout the United States gather at the International Equine Conference on Laminitis and Diseases of the Foot. The 2012 edition, titled "The Equine Limb: Advanced Treatments and Diagnostics," took place Nov. 2-3 in Monterey, Calif., at the Monterey Conference Center. Steinbeck Country Equine Clinic, in nearby Salinas, Calif., also hosted a half day of hands-on wet lab sessions.

This year's lecture lineup drew approximately 95 attendees; among them were many farriers. Said conference co-director James Orsini, DVM, of the University of Pennsylvania's New Bolton Center: "This year's theme was really about bringing the veterinarian and farrier together in treating the horse."

Laminitis Overview and Anatomy

Nora Grenager, VMD, Dipl. ACVIM, of Grenager Equine Consulting, in Middleburg, Va., presented an overview of laminitis and the anatomical structures of the hoof and lower leg that it affects.

The equine hoof is a complex anatomical feature that plays a critical role in horse health. "Hooves carry all the weight of the horse, yet are relatively small," Grenager said. "That means hooves need to be flexible, strong, and resilient."

And in the healthy horse, a hoof is all of those things--the perfect structure to support and propel an athletic quadruped prey animal. However, when things go wrong in the hoof, they tend to go very wrong due to the complexity of the structure within the restrictive hoof capsule, Grenager said. Laminitis is one of those very big problems. It's so big, in fact, that it is considered a leading cause of death in horses, second only to colic. And while the disease is not always fatal, it impacts a staggering number of animals; 15% of all horses will suffer a bout of laminitis in their lifetimes.

To understand what laminitis is and how it affects the horse, it's important to have at least a rudimentary understanding of the structures at play during a laminitic episode. With that in mind, Grenager outlined the hoof anatomy involved for the horse owners in attendance.

Those structures include the:

  • Hoof wall The hard, exterior "capsule" of the hoof.
  • Coffin bone (also called the third phalanx, P3, or pedal bone) The largest, hoof-shaped bone within the hoof capsule.
  • Laminae The Velcro-like tissues within the hoof that suspend the coffin bone inside the hoof wall.
  • Blood vessels and nerves These supply the hoof tissues with critical oxygen and nutrients and remove waste -products.
  • Deep digital flexor tendon (DDFT) A tendon that attaches to the back of the coffin bone and runs up the backside of the hoof. "The DDFT is a large component of how a horse flexes his foot each time he takes a step," Grenager explained.
  • Frog The V-shaped, calluslike cushion on the underside of the hoof.
  • Sole The bottom of the hoof.

So, how do these structures work together and, in the case of laminitis, fail together?

In the simplest terms, laminitis is the inflammation of the laminae within the horse's hoof. Each hoof includes 550 to 600 primary laminae, each with 150 to 200 secondary laminae. These tissues offer shock absorption during locomotion, holding the coffin bone in place and supporting the horse's entire body weight against gravity during movement.

When the laminae become inflamed, they fail to support the coffin bone. The horse's continued weight-bearing and movement can cause the coffin bone to rotate within the hoof or to sink toward the ground. The former occurs when laminae near the toe fail; the latter happens when the laminae throughout the hoof break down, a case commonly referred to as a "sinker." Both can result in the coffin bone protruding through the sole.

Regardless of whether the coffin bone remains in the hoof capsule or penetrates the sole, laminitis causes a painful, debilitating, and potentially deadly failure of basic hoof function.

Common Clinical Signs of Laminitis

Classic clinical signs illustrate this painful disease. Recognizing these signs during early onset and seeking immediate veterinary care can improve the outcome of treatment, said Orsini. He and Grenager described the phases, clinical signs, and degrees of laminitis.

Orsini explained that practitioners and researchers divide laminitis cases into three categories: acute (rapid onset with short but severe course), chronic (lasting for a long period of time or marked by frequent recurrence), and subclinical (not yet showing clinical signs). The condition most frequently occurs in the front hooves, which carry the majority of the horse's weight (estimated at approximately 60%), although it can affect the hind hooves as well.

Common clinical signs of equine laminitis ¬include:

  • Reluctance or inability to walk;
  • Weight-shifting;
  • Increased respiratory rate and frequently increased heart rate;
  • A glazed, pained expression;
  • When front feet are affected, a stance with the hind legs camped under the body and forefeet camped out;
  • Bounding digital arterial pulses (throbbing); and
  • Feet that are hot to the touch.

Unfortunately, Orsini noted, recent research shows that structural failure of the laminae occurs hours, or even days, before these clinical signs are evident.

Additionally, Grenager described three degrees of clinically evident laminitic changes related to degree of hoof damage and coffin bone rotation that a horse might suffer. Those include:

  • Mild No radiographic changes, lameness and clinical signs resolve within days;
  • Moderate Mild radiographic changes, horse treated for months, lifelong management but possible return to work; and
  • Severe Severe radiographic changes, ends athletic career, possibly fatal.

After a mild laminitis episode with no radiographic changes, Grenager said a horse needs at least a few weeks off, followed by a slow return to work. After a moderate episode, if any radiographic changes are evident a horse might require four to six months of treatment and rehabilitation for hooves to stabilize. In severe cases the hope is usually for a pasture sound horse or possibly a broodmare, Grenager said.

Possible Causes of Laminitis

This often frustrating disease has many different causes that result in the same breakdown of the hoof laminae. As Orsini put it, "All roads lead to Rome."

If "Rome" is the result of laminitis with rotation or sinking of the coffin bone, then many roads lead there because the equine hoof is what's referred to as a shock organ. "When there's an overwhelming systemic inflammatory response, often secondary to infection or trauma, there's one organ in each species that really gets the brunt of the effects," Grenager explained. "In people it tends to be the lung, but in horses it's the hoof."

So when horses get sick, their hooves (specifically, the laminae) take the figurative and literal brunt of the problem.

Grenager outlined the possible causes of laminitis, including:

  • Endocrine disorders, such as pituitary pars intermedia dysfunction (PPID, or equine Cushing's disease) or equine metabolic syndrome (EMS). "Endocrine-¬associated laminitis is probably the most common type we see," Grenager said. "This is part of the spring pasture-associated laminitis with which most people are familiar. Endocrine disease encompasses horses that are easy keepers and may have EMS, other horses with documented insulin resistance, and horses with equine Cushing's ¬disease."
  • Toxemia, or systemic inflammatory response syndrome (also called SIRS), which is related to grain overload, post-foaling uterine infection, and infectious diarrhea, among other causes;
  • Exposure to black walnut extract, either digested or via contact with hooves, as with bedding;
  • Supporting limb laminitis, where one leg is injured and the weight-bearing supporting limb is affected ("This is the type of laminitis Barbaro had," Grenager pointed out); and
  • Traumatic laminitis, once called "road founder," from overuse, often on hard surfaces.

Other less common causes include allergies, hoof infections, fever, and limb swelling. All possible causes are made worse by poor hoof care and obesity, Grenager concluded.

Laminitis Terminology: SIRS Rather Than Sepsis

Horse owners have long heard that laminitis can be associated with sepsis, a word that describes an overwhelming bacterial infection of the body. It came from our veterinarians and laminitis researchers, who've frequently referred to the term "sepsis" when discussing the disease, using it interchangeably with SIRS.

Now, said Orsini, veterinarians and researchers are turning to SIRS as the more appropriate term when discussing, treating, and preventing equine laminitis.

"We've used both the terms 'sepsis' and 'SIRS' in laminitis research, following a convention used in human research," he said when he presented during the conference news hour. As it turns out, that convention isn't a perfect analogy when it comes to horses.

Systemic inflammatory response syndrome describes a cascade of inflammation that frequently leads to laminar failure in the hoof. However, as the word "systemic" implies, this inflammatory response affects various body systems. This means that while our focus is often on the foot, much more is going on within the SIRS-afflicted horse. Research shows that, in these cases, subclinical inflammatory indicators are evident in the liver, lungs, and kidneys before the onset of clinical laminitis.

Orsini outlined the causes of SIRS to include:

  • Infection or endotoxemia;
  • Trauma;
  • Ischemia (restricted blood supply to ¬tissues);
  • Immune-mediated diseases;
  • Surgery;
  • Hypo- or hyperthermia; and
  • Profound hypoxia (oxygen deprivation) or hemorrhagic shock.

In the case of SIRS laminitis related to pleuropneumonia (bacterial infection secondary to pneumonia or lung abscesses), enterocolitis (inflammation of the small intestine and colon), and endometritis (inflammation of the innermost lining of the uterus), the connection to bacterial infection (or resulting sepsis) is obvious. However, SIRS can occur without evident infection or sepsis. For example, both the black walnut exposure and carbohydrate overload models of laminitis used in research settings result in SIRS-associated laminitis without infection or sepsis.

The switch in terminology from sepsis to SIRS might sound like simple semantics, but the change of perspective can influence how veterinarians view and treat horses with SIRS. Treatment focus turns to decreasing inflammation both systemically and in the hoof, Orsini said.

Understanding inflammation's relationship to laminitis also indicates a need to identify SIRS before laminar damage occurs. To that end Orsini presented the following proposed diagnostic indicators of SIRS in adult horses:

  • A rectal temperature above 105°F or below 98°F (normal is 98.5-101.5°F);
  • An elevated heart rate beyond 60 beats per minute (normal is around 30-40);
  • Hyperventilation or tachypnea (abnormally rapid breathing); and
  • An increased white blood cell count.

Recognizing these clinical signs early and initiating prompt and vigorous treatment at the first sign might prevent or allay the progression to multiple-organ dysfunction or failure and the onset of laminitis, Orsini said.

The Obel Grading System for Describing Laminitis

Veterinarians use an evaluation method called the Obel grading system to classify equine laminitis cases and track case progression during diagnosis and treatment.

Raul Bras, DVM, CJF, APF, of the podiatry department at Rood & Riddle Equine Hospital, in Lexington, Ky., described this system and emphasized its importance in helping both veterinarians and farriers understand individual laminitic cases.

The Obel system classifies clinical signs of laminitis-related pain into four categories:

  • Grade I Horses shift weight from one foot to the other or incessantly lift feet. Lameness isn't evident at a walk, but at the trot horses will have a shortened stride.
  • Grade II Horses move willingly at a walk and trot, but they do so with a noticeably shortened and stabbing stride. A foot can be lifted off the ground without difficulty.
  • Grade III Horses move reluctantly and resist attempts to lift affected or contralateral feet.
  • Grade IV Horses express marked reluctance or absolute refusal to move.

Identifying a laminitic horse's pain level is subjective, Bras noted, which is why the Obel grading system's four stages work as helpful guides for practitioners to quantify and communicate each case's clinical signs. Using the system also creates a benchmark for monitoring the improvement or worsening of the disease.

No matter the stage, laminitis is a complex disease and brings on new challenges as clinical signs worsen. "Treatment goals and strategies are different at each stage," Bras said. "This affects our drug strategies and shoeing protocols."

Evaluation and Treatment of the Laminitic Horse

The key to treating and managing a laminitis case, said Bras, is a thorough examination and an aggressive but flexible treatment plan, along with owner commitment. "With laminitis we're always trying to stay ahead of what might happen next," he said. He described how he approaches suspected laminitis cases:

Physical examination of the horse Bras takes a case history to help identify ¬potential causes of laminitis, which can include endocrine disorders, gastrointestinal disease (including that resulting from black walnut ingestion or exposure), infection, or trauma. He explained that the goal is to eliminate the triggering event if possible.

External examination of the hoof The external hoof exam includes palpation of the coronary band, which can feel spongy in the case of a sunken coffin bone caused by laminitic failure, Bras said, adding that the hairs that rim this area will often stand up rather than lie flat against the hoof. He also uses hoof testers to apply pressure to the sole and to check for painful reactions, especially around the toe.

Radiographs (X rays) Radiographs are the standard diagnostic modality for identifying bony changes and are an important tool in diagnosing and creating a treatment plan for laminitis. Veterinarians use both a lateral (side) and dorsal (rear) image to evaluate whether the coffin bone has rotated or sunk inside the hoof capsule.

Hoof support Bras described many therapeutic orthotic shoe options (some custom made and others prefabricated) available for supporting laminitic hooves, as well as his method for casting. When applying hoof support, Bras strives to alleviate weight bearing from the toe and distribute the load over other hoof structures. "If a horse has a mechanical failure, you need a mechanical fix," Bras said to explain his philosophy on supporting the laminitic hoof with a shoe or cast. "If you break your foot, you're not going to walk around barefoot. You'll wear one of those special boots and use a cane."

Anti-inflammatory medications and cryotherapy Reducing inflammation is an important step in making a horse more comfortable and limiting additional hoof damage caused by laminitis. "I use the usual anti-inflammatories such as Bute (phenylbutazone) as needed, and cryotherapy (cold therapy applied to the affected hoof) also seems very useful when we believe the horse is going through a bout of laminitis," Bras said.

Strict stall rest "If you suspect laminitis, stall rest should be implemented to try to prevent coffin bone displacement due to the compromised laminae and the forces applied on it," Bras advised.

When treating chronic laminitis, Bras said, the ability to successfully rehabilitate the foot is largely dependent on the health of the coffin bone. He bases prognoses on:

  • Amount of lamellar damage suspected;
  • Overall hoof conformation;
  • Duration of the disease;
  • Amount of coronary band damage (such as shear lesions);
  • Vascular (blood flow) damage as evaluated using venograms;
  • Client goals for the horse;
  • Economics/financing for the owner; and
  • Quality of nursing aftercare.

"He's going to have good days and bad, ups and downs," Bras said of the laminitic horse. "It takes a pretty strong commitment from the horse owner to care for him." And, even with aggressive treatment and the best aftercare, a positive outcome is never guaranteed, Bras said, listing the following potential complications:

  • Coffin joint subluxation (partial dislocation);
  • Overcorrection (negative palmar angle of the coffin bone, leaving the rear of the structure lower than the toe);
  • Undercorrection due to scar tissue;
  • Seroma (fluid accumulation in the ¬tissues that can lead to bone infection);
  • Coronary band pathologies (separation, including shear lesions and a need for partial hoof resection);
  • Compromised coffin bones from osteomyelitis (bone infection);
  • Marginal rim fracture;
  • Deep digital flexor tendon (DDFT) contracture due to decreased laminar resistance; and
  • Sinking of the coffin bone within the hoof capsule.

Lastly, Bras fielded questions about DDFT tenotomy. The procedure involves transecting (cutting) the DDFT at mid-cannon level with the goal of releasing tension on the coffin bone. He said he's experienced varying degrees of success and recommends the surgery only in extreme cases after other methods have failed.

Using MRI to Identify Laminitic Changes

Magnetic resonance imaging (MRI) might offer evidence of laminitic changes in a horse's hoof before the disease is otherwise identified. Equine radiologist and consultant Alexia McKnight, DVM, Dipl. ACVR, of McKnight Insight, in Chadds Ford, Pa., shared her anecdotal experience identifying laminitic changes via MRI.

"Always expect the unexpected when you're doing MRI," McKnight said, adding that most of what we know about laminitis and MRI is from investigative research on a few clinical cases and from lameness cases not initially associated with the disease.

MRI has proven itself as the "gold standard" for diagnosing neurologic and musculoskeletal issues in people, McKnight said. In equine medicine, she explained, MRI has gained popularity and become more accessible over the past 15 years. Due to this availability, along with development of dedicated equine MRI systems and improvement of MRI unit design (i.e., more open designs and standing MRI options for horses), veterinarians now use this technology frequently to investigate lower-limb lamenesses as well as conditions of the head (including the brain and sinuses).

An MRI study yields highly detailed multiplane and multislice cross-sectional images. The horse's body (like the human body), is made up of abundant hydrogen atoms in water and fat that are constantly spinning within and between cells. The MRI unit polarizes those hydrogen atoms within its magnetic field during the imaging process, McKnight explained, allowing anatomic information to be decoded. Complex algorithms crunch the captured data into two-dimensional images that show structures and defects often indiscernible with other diagnostic imaging modalities such as radiography, ultrasonography, and computed tomography (CT).

Radiography and CT, for example, best show bone, while ultrasonography can produce images of accessible soft-tissue structures, such as many tendons and ligaments, in exquisite resolution. Veterinarians and radiologists use MRI to evaluate both bone and soft tissues with superior contrast and anatomic detail, allowing an unprecedented view of what's going on inside the leg and foot and making irregularities easier to identify.

Practitioners turn to MRI because it has been useful for pinpointing lameness causes when other diagnostic imaging options have not, said McKnight.

While MRI is especially useful for identifying bony, soft tissue, and articular changes in the lower leg, veterinarians typically do not use it to diagnose laminitis. While reviewing MRI images for other lameness issues and comparing those findings to those of horses with known laminitis, however, McKnight started seeing structural changes indicative of early or mild laminitis. In her experience, McKnight said, "MRI can help identify laminitis and risk factors before the horse knows he has it."

She said those clues can include various combinations of:

  • Laminar stretching;
  • Loss of corium distinction (ability to visualize the deep inner layer of the sensitive hoof wall);
  • Coffin bone reactions;
  • Signal and architectural changes of the dorsal hoof wall;
  • Signal and architectural changes of the sensitive sole;
  • Hoof wall defects;
  • Fluid pockets and tracts within the hoof wall ("The foot is oozing exudate," McKnight described.);
  • Abscesses; and
  • Vascular abnormalities (predominantly using an additional MR venography technique).

Based on her experience reviewing cases over the past seven years with MRI, McKnight said she can appreciate the subtleties of some of these laminitis indicators. "In addition, in some horses that present with known laminitis for MRI assessment, the changes found seem to be helpful in prognosticating the clinical outcome," she concluded.

Supporting a Foundered Foot with a W-Shoe

Foundered hooves often require extra support to help them heal and grow while also offering the horse pain relief. But, rarely is the hoof undamaged and easy to shoe after a laminitic episode, said Chris Gregory, MS, CJF, FWCF, of Heartland Horseshoeing School, in Lamar, Mo. In these complicated cases Gregory employs W-shoes custom-made for each horse and hoof.

Gregory, who authored Gregory's Textbook of Farriery, discussed the design and implementation of the W-shoe in his lecture, "Introduction to the Principles of Using a W-Shoe on Foundered Feet."

A W-shoe is a hand-forged therapeutic bar horseshoe named for its appearance, which takes on the form of an abstract "w." As opposed to a traditional bar shoe, the W-shoe has an open toe (imagine a standard horseshoe place backward on the hoof) and a v-shaped frog support that attaches to the bar and creates the "w" shape.

The W-shoe is related to a heart bar shoe, which is a continuous bar shoe with the same v-shaped frog support. Some people refer to the W-shoe as an "open-toed heart bar" because of the striking similarity.

"The W-shoe isn't as common as a heart bar or frog-support pad, primarily due to knowledge and farrier skill--or lack thereof," Gregory explained.

In theory, heart bar shoes transfer weight from compromised weight-bearing parts of the hoof to other structures so the latter can share the load. The W-shoe (like a heart bar) transfers weight from the damaged hoof wall to the frog.

When using a W-shoe to manage a foundered horse, Gregory often uses a pour-in filler (commonly sold under the brand name Equipak), made of urethane, that covers the sole and further distributes weight across the hoof.

Modifying the traditional weight-bearing of a hoof to help a laminitic horse requires an educated and experienced farrier working in coordination with a veterinarian, Gregory said. "Whenever a shoe is applied that causes an area of the foot to bear more load than it was meant to, there's always a potential for problems, especially if the shoe is applied without sufficient knowledge or skill," he warns.

When describing the benefits of using the W-shoe, Gregory said it:

  • Can be easier to fit than a heart bar shoe;
  • Eliminates the possibility of the shoe putting pressure on the toe;
  • Can be easier to keep on the foot than other shoes;
  • Makes the horse less likely to stumble;
  • Is easier for the farrier to make than a one-piece heart bar shoe; and
  • Can be made by cutting the toe off a heart bar shoe.

He concedes that the W-shoe isn't perfect and pointed out specific drawbacks, as well, including:

  • It does not provide the stabilization or protection that the full heart bar does;
  • The horse's toes might penetrate the ground more than desired if he is on soft terrain; and
  • It might cause unusual foot remodeling if overused.

Considering the pros and cons of using the W-shoe, Gregory said it offers a much-needed option when a veterinarian and farrier are working to make a laminitic horse more comfortable. "The W-shoe is just another arrow in our quiver (for treating laminitis) and not a cure-all, every-horse answer to founder," Gregory said.

Human Barefoot Trends: What Can They Tell Us About Horses?

Barefoot running and glovelike minimalist barefoot running shoes have gained popularity among human athletes in recent years. And, much like the shoes vs. barefoot controversy in the horse world, the benefits and drawbacks of going shoeless are highly debated in human podiatry, said Grenager.

She presented trends and topics in laminitis research, including the work of Pat Reilly, chief of farrier services at University of Pennsylvania's New Bolton Center, who authored the paper "The Barefoot Paradox," published in the October 2011 Journal of Equine Veterinary Science.

Research has found that human barefoot runners:

  • Use 2% less oxygen than their shod counterparts;
  • Have varied ground impact patterns; and
  • Have lower ground-impact forces.

These findings could suggest an increase in performance longevity for the barefoot human athlete prior to tiring and decreased instances of injury. However, Grenager noted, a correlated improvement in performance hasn't been universally supported by performance records.

Additional studies by the U.S. Navy investigating barefoot running in humans found use of minimalist shoes:

  • Resulted in stronger feet;
  • Reduced foot-to-ground impact;
  • Improved balance; and
  • Increased proprioception (the ability to sense the position, location, orientation, and movement of body parts).

Drawbacks noted by the U.S. Navy included less overall support and protection of the foot and a necessary transitional training period as subjects moved from wearing shoes to running barefoot.

Podiatrists in general do not recommend minimalist barefoot shoes for people with pre-existing foot problems or those who find foot pain relief from using custom orthotics. "We believe we can extrapolate these findings to horses," said Grenager, as evidenced by the rise in use of nontraditional orthotics in horses.

That, she added, means horses with foot issues, including those with laminitis-related hoof changes (and especially acute laminitis) are likely to benefit from hoof support such as shoes or casting. Current options for horses include a wide variety of specialty shoes, boots, molded urethanes, glue-on shoes, and hoof casts.

Grenager concluded that the ideal situation for an individual horse likely balances the horse's pre-existing hoof conformation with competing demands of protection, support, traction, freedom of movement, and optimal biomechanics.

Stem Cell Therapy as a Potential Laminitis Treatment

Stem cell therapy might offer practitioners an additional treatment option for the fight against laminitis. While researchers have not yet completed any formal studies of stem cells and laminitis, both Bras and John Peroni, DVM, MS, Dipl. ACVS, of the University of Georgia's College of Veterinary Medicine, have clinical experience using stem cells to treat laminitis cases.

Mesenchymal stem cells (MSC) are multipotent stromal (connective tissue) cells that can differentiate into many types of cells, including those that make up bone, cartilage, and fat. Research shows that stem cell therapy helps improve the quality of healing in orthopedic (bone) lesions.

"MSC therapy is an attractive treatment modality (for laminitis) because of its potential to positively influence tissue repair," Bras said. The hope is that it would also help repair laminar damage and stabilize the coffin bone within the hoof capsule.

In addition to the possibility of healing tissues, studies show that stem cell treatment has an anti-inflammatory effect, which might offer an additional benefit to the laminitic horse.

However, using stem cell therapy for laminitis isn't without concern, Peroni said, noting that stem cells could theoretically block capillaries, which are vital in supplying blood to the laminae. "The last thing you want to do is plug things up," he explained.

Peroni's experience using stem cell therapy in laminitic horses consists mostly of cases with few treatment options-remaining.

Questions also remain on how, when, and where to implement stem cell therapy when treating a laminitic horse. "A lot is largely unanswered," Peroni said. But, he added, when talking anecdotally about using stem cell therapy for laminitic horses, "people are reporting that horses seem to do well and quality of healing improves. My interest is in learning if these therapies help horses, and I believe they do."


About the Author

Michelle N. Anderson, Digital Managing Editor

Michelle Anderson serves as The Horse's digital managing editor. In her role, she produces content for our web site and hosts our live events, including Ask the Vet Live. A lifelong horse owner, Anderson competes in dressage and enjoys trail riding. She's a Washington State University graduate (Go Cougs!) and holds a bachelor's degree in communications with a minor in business administration and extensive coursework in animal sciences. She has worked in equine publishing since 1998. She currently lives with her husband on a small horse property in Central Oregon.

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