Virtualhoofcare

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Virtual Hoof Care

Sound Hooves for all Horses


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 BoneThe 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 BoneThe 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 StructuresThe outer wall is the hard outer

covering that is most easily recognizable as the horse's hoof. It is "dead" 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 "braces". 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 LigamentsTendons, 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 TendonThe 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 InsulationHorses 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 PumpBy 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 "spring" 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 FormWhile 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."

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

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.comJerry 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, AustraliaBiomeridian, 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.

http://www.healthehoof.com/

http://www.horsesrunningwild.com/

http://www.freedomfarms.net/

http://www.hoofcareunltd.com/

Virtualhoofcare

Health & Medicine

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