Virtual Hoof Care for Horses

Virtual Hoof Care
Sound Hooves for all Horses

© EquineSoundness2007

Chapters

Hoof Anatomy
Hoof Physiology


If you ever had a horse
with “bad” feet, you will
be interested to know
that in the end there is
no such thing. The
horse is designed with
excellent feet from
birth.

These are the hooves of our poster
child from the first slide: “Echo”, a
Belgian Warmblood


Hoof Anatomy
In order to understand the way
the hoof grows and how
pathology effects the hoof,
we need to be very familiar
with the anatomy of the hoof,
better even with the anatomy
of the whole horse. In this
chapter we are going to look
at the external and the
internal structures of the
hoof .


Outside of the Hoof


Inside the Hoof


Coffin Bone
The coffin bone is different
from any other bone in the
horse's body.
The triangular shape is
very strong.
This is the only bone that is
covered by corium instead
of periosteum.
Corium produces horn. More
about that later.
The bottom edge of the
coffin bone is very sharp.


Navicular Bone

The navicular bone is
situated in the back of the
coffin bone and helps the
deep digital flexor tendon
to change direction from
the horizontal connection
on the coffin bone to the
more upright direction of
the bones above the coffin
bone.


Short Pastern Bone
The short pastern bone sits
partially in the hoof capsule.
It connects the coffin bone
with the long pastern bone.
The coffin joint (connection
between the coffin bone
and the short pastern bone)
can only move in two
directions (back and forth).


Long Pastern Bone

The long pastern bone
forms the fetlock joint
together with the
cannon bone and the
sesamoid bones.


Sesamoid Bone

The sesamoid bones help
the tendons in the back
of the hoof to make the
turn and to run
smoothly up the leg.


Cannon Bone

The cannon bone forms
on the lower end the
fetlock joint with the
long pastern bone. On
the upper end it forms
the carpal joint (knee)
with an array of smaller
bones.


Splint Bones

The splint bones are
remnants from the
development of the
horse from a four-toed
wood dweller to a one-
toed open range
animal. They are
attached on both sides
of upper end of the
cannon bone and have
no bony connection on
their lower end.


Corium

The coffin bone is
covered by corium.
Corium is unique as it
produces horn. The
horn produced is
actually waste protein
excreted by the body.
There are various coria
in the hoof.


Perioplic Corium

The perioplic corium
covers the very top of
the hoof capsule. It is
very thin, highly
dependent on water
and prevents the hoof
from drying out.


Coronary Corium

The coronary corium
produces the hoof wall
and the bars. It
produces horn tubules
which are connected to
each other with soft,
connective
(intertubular) horn.


Sole Corium

The sole corium produces
the sole horn. The sole
horn is slightly softer
than the wall horn.


Frog and Bulb Corium

The frog and bulb corium
produces soft horn that
has a high water
content.


Laminar Corium

Often also described as
lamellae corium, the laminar
corium originates from the
outer surface of the coffin
bone and produces the
lamellae which suspend the
coffin bone in the hoof
capsule by growing outward
and merging with the
structures of the hoof wall in
a Velcro-like fashion.


Blood Supply in the Hoof

The inside of the hoof is very vascular. The
digital arteries enter the hoof from above
and branch off
to nourish the
heel region,
the coronary
band and the
sole.


As the lower leg has no
muscles to pump the
blood through the leg to
the heart, the blood
pumping is supported
through the hoof
mechanism – the ability
of the healthy hoof
capsule to contract and
expand.


Through this blood supply
the body not only nourishes
the various parts of the
hoof, it also rids itself of
surplus protein by building
horn through excretion of
waste protein


Venogram

This shows
once again
how vascular
the hoof is


Horn Structures
The outer wall is the hard outer
covering that is most easily
recognizable as the horse's
hoof. It is quot;deadquot; tissue in that
it has no blood or nerve supply
and is made primarily of
hardened protein tissue called
keratin.

The outer wall grows from the
coronary band down toward
the ground. Damaged wall can
not heal at the site of damage,
but must grow out and be
replaced by new horn.


The hoof wall is made out of
hard horn tubules (with or
without dark pigment) as
you can see in this
picture. The horn tubules
are produced by papillae
in the coronary bulge and
the grow in spiral form,
which gives them
elasticity and resilience.
The hard horn tubules are
connected with soft
connective horn.


Directly below the hair bearing
skin, above the coronary band is
the perioplic ring. This is a band
of soft tissue that produces the
periople, a thin layer of skin that
covers and protects the
coronary band. The periople is
highly water containing horn that
protects the coronary band from
drying out. In the heel region the
periople becomes wider and
forms a thicker layer. Here it
surrounds the heels and merges
with the frog/bulb.


The bars are a
continuation of the
wall. In old farrier
texts bars are
referred to as
quot;bracesquot;. This may be
a more descriptive
term. As can be seen
here, the bars end at
the middle of the frog.
The bars are made
out of hard horn
tubules, connected
with soft horn, just
like the walls.


The sole is a modified form of
hard horn that covers the
bottom of the hoof. Like the
wall it contains no nerves or
blood. The sole provides a
protective covering for the
sensitive structures and
tissues beneath. The sole
horn is also produced by
papillae, however, as the
sole horn papillae are less
dense, the sole horn not
quite as hard as the wall
horn.


The frog horn is the soft
horn growing between
the bars.


The Lateral Cartilage(s)

Positioned on each side
of the hoof and
connected to the coffin
bone, short and long
pastern bone, the
lateral cartilage serves
as a shock absorber
and eases breakover.
They can be felt under
the skin on both sides
and in the back of the
hoof.


Tendons and Ligaments
Tendons, tendon injuries, tendon
strain, tendon pressure, almost
every horse owner is concerned
about the tendons. And for good
reasons. Tendon injuries are
slow to heal and often do not
heal well. But there may be a
solution, let’s first look at the
intricate anatomy of the tendon
and ligament apparatus.


Deep Digital Flexor Tendon
The deep flexor tendon, (DFT or DDFT) originates
at the deep flexor muscle of the leg, and inserts
(attaches to) at the semi lunar crest of the coffin
bone after passing over the fulcrum points
formed by the navicular and sesamoid bones. It
flexes (folds) the leg when the deep flexor
muscle contracts.

It is running over the back of the knee in the carpal
canal and held in position by a carpal check
ligament.

It then extends down the back of the cannon bone
between the superficial digital flexor tendon and
the suspensory ligament.

In the middle of the cannon bone the deep digital
flexor tendon is joined by the carpal check
ligament, known as the inferior check ligament.

The tendon then passes over the sesamoid bones,
before passing between the two extensions of
the superficial digital flexor tendon.


When a tendon gets injured it is important to have the
healing happen with as little scar tissue as possible.
Tendon scar tissue is made of fibers that are not
oriented in the same direction as healthy tendon
fibers. Tendon tissue can only heal correctly under
pressure. Given the opportunity, the injured horse
will first use the leg very gingerly, putting no more
pressure on it than the injured tendon can support.
Then gradual he will add more pressure and the
tendon will heal strong and completely.


Functions of the Hoof

The function of the hoof is
to carry and move the
body, anytime and
regardless of
temperature, terrain
and age of the horse.


Protection

The thick horn capsule
protects the inside of the
hoof from mechanical
forces. It grows enough to
withstand the natural
abrasion of 10 and more
miles a day. The more the
horse moves, the more horn
will be produced.


Temperature
Insulation
Horses living for months
on end in snow and ice
around the arctic circle
maintain a steady
temperature inside the
hoof capsule; “hot”
shoeing does not
overheat the inside of
the hoof.


Traction
The hoof is conical in shape,
the wall meets the ground
at an angle, giving the hoof
a wedge-like action on soft,
slippery ground.

Frog, bulb and heels are all on
the same level in a sound
hoof. On weight bearing this
provides a suction cup
effect on very slick terrain,
like wet pavement or ice.


In the heel-bar triangle
the walls and bars act
like skid brakes. The
wall protrudes in a
naturally worn hoof just
above the sole level.


Shock Absorption

In a natural hoof the
bones are aligned in
such a way that upon
weight bearing the
impact force is partially
absorbed similar to a
leaf spring.


The spiral horn tubules act like
natural springs. The veterinarian
University in Zurich /Switzerland
conducted various studies
proofing the reversible
compression of horn tubules.
Horn tubules can only move
independently when the
connective horn between them
is intact and elastic.

The picture is a magnification of
these shock-absorbing horn tubules


Lamellae and laminar horn have a tight, but elastic
bond, they also contribute to shock absorption.


The lateral cartilage
functions as a lateral
shock absorber and
eases stress in
breakover


Heart Supporting Circulatory Pump

By being flexible (expanding on weight bearing,
narrowing during non- weight bearing) the
hoof capsule acts as a circulatory pump in
the area of the corium, supporting the
heart with each step by moving the blood
from the far end of the extremities back up
the leg to the body.


Feeling

The horse can feel the ground.

Intense pressure (as from a large
rock) tells the horse to pick up
the foot before putting full
weight on it and possibly doing
damage through bruising


Hoof Flexion (Hoof Mechanism)

The hoof is a very vascular structure, however
it is the structure the farthest removed from
the heart. In order for the blood to be pumped
back to the rump of the horse, against
gravity, the hoof is constructed to aid with this
pumping.


Upon weight bearing the frontal
wall of the hoof sinks
minimally towards the middle
of the hoof (see picture), the
lateral walls move slightly
down and out. When there is
no pressure on the
hoof, there is no pressure on
the lateral walls either.

During weigh bearing the solar vault is flattened, the frog gets closer to
the ground and the bulbs of the hoof are lowered. When weight is
removed, all structures quot;springquot; back into their original position.


The hoof capsule of a living horse
moves at it's widest point about
2mm (hard hoofed horses) to 3
mm (softer hoofed horses). When
the horse moves very fast the
spreading of the hoof capsule
becomes more pronounced.

An overextension of the same is
prevented by the bars. They
stabilize the hoof towards the
middle of the hoof structure. 1980
Prof. Preuschoff (University of
Bochum, Germany) proved with a
paint and glaze test that the entire
hoof wall moves upon weight
bearing. The movement begins on
either side of the coronet at the
center of the toe.


Here we see the hoof in
the non-weight bearing
situation. The space
between the coffin
bone and the hoof
capsule is narrow, the
corium is expressed.


Here is the hoof in the weight bearing phase. The coffin
bone sinks down in the hoof capsule. The increased
diameter of the hoof capsule upon weight bearing
allows for more space around the coffin bone. The
laminar corium fills with blood. The sole draws flatter,
makes room for the descending coffin bone and
therefore the solar corium also fills with blood.


When the foot is lifted for the next step, the hoof capsule
decreases in size, the blood in the corium is squeezed
out. It passes into the venous system inside and above
the coronary corium, which is in it's relaxed state when
the hoof is non- weight bearing.

In the non-weight bearing phase blood can reach the
arterial arch inside the coffin bone, but can go no further
because the hoof capsule is narrow, the corium is
pressed against the wall. Only when the hoof becomes
weight bearing again can the blood fill the lamellae
corium.


On weight bearing,
the slanted bulge of
the coronary
corium (together
with the extensor
tendon and the
slanted top of the
interior wall) press
against the
coronary venous
plexus and move
the blood up the
leg.


Hoof Form
While there are some
breed differences,
some breeds having
more slanted hooves,
others having more
upright hooves, the
same principles apply
to all hooves in as far
as form and function
match in the healthy
hoof. The hoof
capsule is, beside x-
rays, our only visual
tool.


The shape of the hoof
capsule is in general
determined by the
shape of the coffin
bone.


Healthy frontal
coffin bones
have a toe
angle of about
45º , healthy
coffin bones of
the hind feet
are about 55º


This top view just
reminds you of
the shape the
coffin bone
should be inside
the hoof capsule


Top: Front
coffin bone,
a rounder
shape
Bottom: Hind
coffin bone,
a more
elliptical
shape


Healthy coffin
bones
have a
more
shallow
solar vault
in the front
hooves, a
steeper
solar vault
in the hind
hooves


When viewed from
the front, the
coronet band is
level (horizontal)
and the hoof walls
diverge


From the side (lateral) the
healthy front hoof has a
30º hairline, sloping
from the heel towards
the toe, a 45º toe line in
the frontal hoof and a
105º angle between the
two. In general, if all
these angles are met in
a hoof, you can
ascertain that the coffin
bone is ground parallel.


While the frontal view is
relatively easy to
remember, it takes
some more practice to
see correct hoof form in
the lateral view. Try and
take a protractor and
measure the angles in
this picture.


The lateral view of the
healthy hind hoof
shows a 30º hairline, a
55º toe line and a 95º
angle between the two.


In the healthy hoof the heel height, measured from the
point where the lateral cartilage curves down into the
hoof capsule, is about 3.5cm


The bars end at the
middle of the frog.


This picture
shows a nice
wide frog


The front hooves differ in form
and function from the hind
hooves. The hind quarters
provide propulsion. The horse
pushes off backward and
outward. It is physiologically
correct (both in terms of hoof
wear and traction) for the
outside wall of the hind hoof to
be more slanted than the
inside wall. The outside half of
the hind hoof is also slightly
wider than the inside.


Quarters


A near perfect foot. The
scoop on the bottom of
the hoof prevents the
hoof wall from binding
against the ground
when the hoof
becomes full weight
bearing.


Red line: Toe height
Green line: Toe length
Blue line: Coronet angle


Shoeing
Since horse shoes were

designed by medieval
blacksmiths with available
materials and not by modern
biomechanical engineers with
the horse’s hoof physiology in
mind, there are a number of
biomechanically pathological
effects of horseshoes.
Interestingly, little has changed

about the horseshoe since its
original medieval design.


“Of the 122 million equines found
around the world, no more than 10
percent are clinically sound. Some
ten percent (12.2 million) are
clinically, completely and unusable
lame.

The remaining 80 percent (97.6 million)
are some what lame...and could not
pass a soundness evaluation test.quot;

Ref: American Farriers Journal, Nov.
2002, v.26 #6, p.5.


When the shoe is applied, it does not
allow the hoof to flex. This causes
decreased blood flow into and out
of the hoof, depriving nerves of
blood supply thereby resulting in
the hoof becoming numb. The
shoe is usually made of steel, it is
very inflexible, and is solidly
fixated to the hoof. The vessels
that supply the hoof with blood are
also compressed decreasing the
efficient blood flow into and out of
the hoof. The limited blood flow
causes waste products to build up
in the hoof, minimizing nutrients
and oxygen from entering, which
in turn, causes decreased cellular
metabolism and tissue growth.


In addition, as described
above, the horses
hooves cannot
contribute to general
circulation when they
are restricted by
horseshoes and
confinement.


This tourniquet effect of horseshoes
was dramatically demonstrated in a
video produced in 1993 by Dr.
Chris PollittPhdDVSc MSC of the
Department of Companion Animal
Medicine and Science, University
of Queensland Brisbane Australia .

This investigator using freshly
prepared cadaver horse hooves
compared shod and non-shod
specimens measuring blood flow.

The application of shoes resulted in a
visible dramatic reduction in blood
flow and alteration in the
physiology of the horse's hoof.
Despite the obvious implications of
this work, it has not affected the
veterinary or farrier practices within
the horse community significantly.


If you would like to know more about the

effects of shoeing, anatomy of the hoof, or
basic trimming, please consider enrolling in
one of our Online Courses. Click on the
“Education” tab on our website
http://www.Equinesoundness.com


To take custody of a large
animal like a horse is a
huge responsibility. We all
are steeped in traditional
thinking and it often takes a
leap of faith to change our
surroundings. We will be
glad to have you as one of
our students.


Thank You
Fisher Lameness Foundation http://www.healthehoof.com
Perri Allemand http://www.horsesrunningwild.com
Jerry Schmidt http://www.freedomfarms.net
Claudia Garner http://www.hoofcareunltd.com
Dr. Andrew Parks “The Glass Horse – Equine Distal Limb”
Dr. Chris Pollitt, University of Queensland, Australia
Biomeridian, Draper, UT

for the use of their pictures and resources.

Some of the graphics/pictures came from unknown sources. If any copyrights have
been breeched by using them, please contact the webmaster and we will
acknowledge them or they will be removed immediately.


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