If you’re looking to prevent devastating coffin bone rotation or sinking in a horse with laminitis, researchers have reported the best option might be heart-bar shoes, based on a new study examining biomechanics of common shoeing approaches in these animals.

Researchers studying cadaver forelimbs recently found that heart-bar shoes stabilize the coffin bones in laminitic horses’ feet so well that they don’t move any more than they do in healthy hooves wearing the same shoes, said Mandi J. Lopez, DVM, MS, PhD, Dipl. ACVS, professor and director of the Laboratory for Equine & Comparative Orthopedic Research at Louisiana State University’s School of Veterinary Medicine, in Baton Rouge.

By contrast, the worst-case scenario for laminitis was standard, open-heel shoes. The researchers found that the third phalanx (P3)—or coffin bone—moves away from the coronary band at the top of the hoof morewhen the foot is shod with “normal”, open-heel, steel shoes than when barefoot, she said.

“The study results provide unique data about the impact of shoe design on the behavior of the coffin bone and hoof capsule,” Lopez said. “We hope they provide a foundation or platform to help guide novel shoe designs to support hooves during recovery from laminitis.”

Comparing Laminitic and Nonlaminitic Cadaver Limbs as they ‘Step’

Despite how common laminitis is and widespread, long-held beliefs about the best way to shoe laminitic horses, very little scientific research exists on the topic, Lopez said.

Lopez and her team sought to test the design and function of shoes in horses with laminitis, she said. “Weakened (laminitic) hoof tissue needs stabilization to heal properly just like damaged skin can require stitches and bones can need implants.”

“Our goal was to precisely measure the specific effects of shoe shape on the motion of the third phalanx within the hoof capsule and the hoof capsule itself,” Lopez explained. “After many years of work to set up an accurate and reliable laboratory simulation and using high- tech motion capture technology, we were able to accomplish our objective.”

After validating their equipment and setup, Lopez and her fellow researchers collected 16 cadaver forelimbs, from the fetlock down, of horses euthanized for reasons unrelated to the study. Half the limbs were affected by laminitis, and the others were considered healthy.

A certified farrier trimmed and leveled each hoof before applying one of three kinds of shoes: a standard (open-heel) shoe, an egg-bar (full circle) shoe, or a heart-bar ( bar across the back heels plus frog coverage) shoe. Each foot was fitted once with each kind of shoe for testing.

The team placed light-emitting diode markers for motion detection at several key places on each hoof. Then, using a mechanical testing system equipped with a custom fitting they built, they evaluated each hoof’s response to pressures that simulate walking. The researchers used optoelectronic sensor units to show how the hoof capsule and coffin bone moved during the simulations, testing each foot four times while barefoot and then four times with each kind of shoe.

Shoe Type Significantly Affects Coffin Bone Movement in Laminitic Hooves

Lopez and her colleagues found that in both laminitic and nonlaminitic feet, the hoof wall deformed and the coffin bone moved during loading and unloading—force phases as expected in a horse’s hoof while placing and lifting a foot during a step.

Coffin bone movement also varied considerably between laminitic and nonlaminitic feet, she explained. In nonlaminitic feet, movement followed a similar displacement pattern whether unshod or shod.

That wasn’t the case for laminitic feet, said Lopez. The coffin bone moved considerably less when the foot was fitted with an egg-bar or heart-bar shoe than when barefoot. In fact, the coffin bone moved the most in laminitic feet that were equipped with standard open-heel shoes, she said. That was especially true during the maximum force of the step and during the unloading phase of the step cycle, she said.

“We expected that weakened tissues would have greater motion compared to normal, but some shoes, like egg bar and heart bar, effectively stabilized the coffin bone in laminitic hooves,” said Lopez. Even so, in the end that finding “wasn’t particularly surprising” since it has been expected in the field for quite some time, she added.

Different Hoof Deformation and Coffin Bone Movement Patterns in Laminitic vs. Healthy Feet

Laminitic hoof capsules followed a distinctly different pattern of deformation than nonlaminitic hoof capsules, said Lopez. For example, the change in heel width closest to the ground was significantly greater in unshod laminitic hooves compared to shod, regardless of the shoe type. However, in nonlaminitic hooves, the change in unshod hooves was only greater compared to hooves with heart-bar shoes.

In nonlaminitic feet shod with egg-bar or heart-bar shoes, the coffin bones moved away from the dorsal wall (front) of the hoof compared to unshod. However, the effect was exactly opposite in laminitic hooves where coffin bones tended to move toward the dorsal wall with egg-bar and with heart-bar shoes compared to unshod. In laminitic hooves, both open-heel and egg-bar shoes tended to increase movement of the coffin bone away from the coronary band, while heart-bar shoes did not.

“From our perspective, the most impactful information was that the direction of coffin bone motion was different between healthy and unhealthy tissues for some shoes,” Lopez said.

“Perhaps the most compelling point from the study is that predictions or assumptions about shoe effects on healthy hooves cannot be directly applied to laminitic hooves,” Lopez said. “That is, changes in hoof deformation and the coffin bone motion resulting from shoe shape are likely not identical, and they are sometimes almost opposite, in healthy versus unhealthy tissues.”

The findings could pave the way for additional studies allowing researchers to not only fine-tune therapeutic farriery for laminitic horses but also learn more about hoof/shoe biomechanics, she said.