Many horse owners go their whole lives caring for
horses’ hooves with little knowledge of the hoof capsules’ inner
workings—the interaction of the bones, tendons, ligaments, and
other parts that lie beneath. They might be aware of how the hoof’s
outer condition reflects its external health, but the hoof’s
appearance also provides a wealth of information on its internal
well-being. It’s much more than just a covering for the end of the
limb or the equine equivalent of the human
fingernail.
Long-term hoof imbalances put excess strain on the bones and soft tissues, potentially compromising the structures’ shape and sturdiness long-term. Conversely, damaged or misshapen internal structures can effect congruent changes in hoof shape.
In part 1 of this series we described internal hoof
structures and common problems. Now we’ll put it all together by
discussing external hoof anatomy, common problems, and how they
relate to the internal structures.
When you look at the hoof as the horse stands, you are
seeing the hoof wall. It grows down from the coronary band, the
junction between the hoof and the skin. The toe is closest to the
horse’s nose, the heels are closer to his tail, and the quarters
are between.
If you pick up the hoof to look at the bottom, you will
see the wall wrapping around the outer edge and the white line just
inside of it (easier to see in a freshly trimmed foot). Moving
rearward from the toe, you’ll find the sole that covers the
majority of the hoof’s bottom. There is also a triangular elastic
structure pointing forward from the heels called the frog (which
aids in shock absorption). In the center of the frog and on either
side are grooves called the central and lateral sulci. Lastly, we
have the heels directly behind the frog and the bars at the
rearward ends of the hoof wall, where the wall turns inward and
then forward away from the heels.
Most healthy hooves have the following characteristics, says Amy Rucker, DVM, owner of Midwest Equine, in Columbia, Missouri.
Also consider the following signs of hoof health:
Aside from looking for obvious injury, “Visual
examination of the foot—its growth pattern, shape, and external
characteristics—hints at internal areas of the foot that bear more
‘load’ or stress (and, thus, need unloading),” explains
Rucker.
Increased stresses on parts of the hoof can have three results:
The hoof doesn’t exist in a vacuum, however—O’Grady
encourages owners to also consider limb conformation, which can
change how forces are distributed within the hoof capsule, leading
to hoof wall deformation.
Let’s start with the problems that involve damage and
disease of outer structures, then we’ll move on to problems related
to hoof balance.
With puncture wounds from stepping on a nail or similar sharp object, the real risk isn’t the hole, but the expressway it provides for bacteria to get deep inside the body and cause infection. Rucker strongly recommends leaving the object in place if possible until the veterinarian can radiograph (X ray) the foot to see what internal structures are affected.
Scarring from coronary band damage can cause
altered hoof growth below the injured area for the rest of the
horse’s life.
“These injuries need to be bandaged and treated to restore alignment of hoof tubules for healthy future growth,” Rucker advises.
“Visual examination of the foot hints at internal areas of the foot that bear more load or stress.”
Dr. Amy Rucker
Minor chips, cracks, and missing chunks of wall might be nothing to sweat over, but more serious damage such as deep quarter cracks and large missing pieces of hoof can be much more painful and problematic.
“If you have a large chunk of the hoof missing with bleeding, have a vet out because the horse may need a pressure wrap to keep the wall from bulging and regrowing incorrectly,” says Rucker. “The vet can also radiograph quarter crack cases to help the farrier treat them,” based on any internal damage that might have happened.
Abscesses are pockets of infection (like pimples) that can break open at the thinner coronary band area or rupture through the sole/white line. Once the abscess bursts, lameness improves immediately because of the reduced pressure.
“Anytime a horse is non-weight-bearing lame, I worry about a fracture or septic (infected) tendon, but it’s usually an abscess,” says Rucker. “They’re horribly painful, and (a non-steroidal anti-inflammatory such as) phenylbutazone (Bute) won’t resolve the pain.”
White line disease is an opportunistic fungal or bacterial infection that strikes where the wall is already stressed or cracked, softening the inner hoof wall so it crumbles and allows outer wall layers to detach.
“You have to remove enough wall to get air to affected
areas (to help kill the microbes breaking the wall down), support
the remaining foot with a special shoe, and lay the horse off while
the wall regrows,” says Rucker.
Thrush, a bacterial infection of the frog and
sulci, can be caused by a dirty/wet environment, says Rucker. But
that’s not always the case; other causes include anything that
impairs the horse’s natural hoof-cleaning mechanism—continuous
changes in the hoof’s inner structure, aided by movement, that keep
the horse’s foot clean. “Keep affected feet dry and clean and the
frog trimmed so you can get air and medications down into the
sulci,” she says.
Now let’s move on to hoof problems tied to the internal structures. In most mild cases, Rucker notes, the horse can return to soundness, but the more severe the problem, the greater the chances it will become long-term.
Club feet, caused by overly tight deep digital flexor tendons, have a steep toe angle and often a more horizontal coronary band when viewed from the side. The hoof-pastern axis is broken forward (hoof steeper than pastern), and the hoof might flare at the toe as a result of the tendon pulling the toe of the coffin bone down and rearward.
These features are similar to what’s seen when the coffin bone has become unstable and rotated downward at the toe from chronic laminitis, O’Grady adds. Both club footed and laminitis-affected horses exhibit a high palmar angle (heels of the coffin bone are significantly higher than the toe).
“If the white line is stretched at the toe, the case is more severe,” Rucker notes. “If radiographs show bone damage from the increased pressure on the toe, it’s harder to keep these horses sound.”
Long toe/low heel is the opposite of a club
foot; if the hoof-pastern angle is broken back, the horse probably
has a long toe and low heel. The long toe puts a lot of leverage on
the heels, crushing them even to the point that the hoof tubules
are horizontal (parallel with the ground). Horses with such heel
conformation typically have a poorly developed digital cushion and
thin collateral cartilages, says O’Grady.
Rucker adds that affected horses usually have a negative
palmar angle, heel pain, and might develop navicular and coffin
joint pain from the abnormal stress applied to those
structures.
Sheared heels occur when the coronary band is higher in one quarter/heel area of the hoof than the other, says O’Grady. This can result from compressive stress (the wall could be too long in that area) and is frequently accompanied by narrowed growth rings. The higher heel is also more prone to vertical quarter cracks.
Contracted heels occur along with a compromised digital cushion and, therefore, reduced shock absorption.
Thin soles can be caused by genetics
and/or overtrimming. Rucker explains that horses with thin-soled
feet often have flat soles (no cup) and an overly thin wall. “These
feet often have nail holes and growth rings close together because
the foot just isn’t growing well,” she comments.
Laminitis, if severe or chronic, can alter hoof growth. O’Grady explains that chronically laminitic feet usually have wider growth rings at the heel than at the toe (because the damage tends to be worse at the toe, compromising growth there more severely than at the heels).
Rucker adds that the dorsal wall and white line can
widen at the toe as the attachment of the hoof to internal
structures collapses and the hoof tubules begin to grow
outward.
Keep your horses sound by watching their feet for small changes on the outside that could indicate problems are brewing on the inside. Prevention or early detection are far simpler, cheaper, and more effective than treating lameness or injury.
“Understand the challenges of each limb and hoof’s conformation and manage the foot for maximum soundness with that conformation rather than conforming to a ‘perfect’ standard,” says Rucker. “Everyone tries to get their horses’ feet to look pretty and perfect, when having functional feet with plenty of mass is much more important than having pretty feet. (With the latter) the owner is happy, but the horse isn’t.”
Other Articles
CT Scans Can Help Diagnose Stifle Lameness
Diagnosing And Treating Equine Neck And Back Pain
Fossil Evidence Of Laminitis In Ancient Horses
Hoof Angles' Impact On Lameness
Examined
Hoof Cracks: Types And
Treatment
Hot Topics In Horse
Care: Horse Hoof Biomechanics
Joint Injections
MRI Diagnostics: Uses And Limitations
MRI To Evaluate Suspensory, Sesamoid Injuries
Physical Exam Of The Horse Hoof
Prepurchase Exams: A Health Care Must
Dr. Krystyna Stoffel, D.V.M.
651.226.6862
Nick Stoffel,
Farrier
651.270.1044
13014 265th Street, Welch, MN
55089
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