The frog generally
is viewed as the blood pump of the foot. However, the frog has
no major blood supply. It is my (Chapman's) belief that it serves
little function, if any, in forcing or acting to pump venous blood
back up the leg.
of the horny wall and the corium of the third phalanx is formed
by the laminae. In the normal foot, the bond between these laminae
cannot be broken. It is only after death of these structures that
they can be separated.
The sole is
the horny covering or plate of horn on the bottom of the hoof.
It is not usually as tough as the wall. Its origin is the solar
matrix and it receives its blood supply from arteries branching
from the terminal arch, drained by the subsolar venous plexus.
The bond between the matrix and the sole is papillar, rather than
laminar. They, too, cannot be separated in a healthy foot. Only
when the foot is injured or in the case of founder, can they be
band (coronet) produces the central laminar portion of the horny
wall. The coronet is similar to the human cuticle and houses a
mass of minute capillaries. The horny wall starts below the coronary
band and extends downward until it reaches the sole. The wall
including these laminae is extremely important, as it is responsible
for bearing most of the weight of the horse.
The deep digital
artery is the main blood supply to the third phalanx. It enters
the hoof both medially and laterally at the bulb of the heel,
passes through the foramen on either side of the semilunar crest,
and forms the terminal arch. This artery is not protected by anything
but the sole until it passes through the plantar foramen of the
third phalanx where it anastomoses with its partner of the opposite
side. If this artery or its branches which perforate the wall
of the third phalanx are destroyed, the horse will also be ruined.
This is why a hoof cast, improperly applied, is so dangerous.
Cases are known in which the blood supply was shut off and the
digital artery was destroyed.
of the vascular system of the complete hoof consists of two-thirds
veins and one-third arteries. Two major vessels are the circumflex
vein and circumflex artery which run along and the distal peripheral
edge of the third phalanx. At no point can sharp divisions be
recognized. Each part unites and becomes continuous with the other.
is usually a sign of some underlying disease process which commonly
includes diseases of, damage to, or infections of the intestinal
tract; toxemia, as following retained afterbirth; stress and trauma,
such as occur with dystocia; deep necrotic wounds, resulting in
septicemia; pneumonia, which is severe and often may be necrotic;
drugs, especially high levels of steroids and reactions to different
drugs; and finally, mechanical laminitis, such as road founder,
trimming and/or shoeing which forces the horse to walk on the
sole or allows the shoe to put pressure on the sole.
must be corrected before a favorable response can be expected.
point to consider is that not only the cause must be determined,
but also the extent of the damage to the feet. Measures need to
be taken to correct this damage and steps must be taken to prevent
swell in the early stages. Pressure increases between the hoof
wall and the third phalanx. It is this pressure that causes the
eventual necrosis, and it is this pressure that causes the rotation
of the third phalanx. It is our opinion that the pressure from
the deep flexor tendon is a negligible factor in rotation of the
third phalanx, unless there is a pre-existing flexor deformity,
or unless the heels are cut abnormally low or the toe is elevated
to create a secondary flexor deformity.
between founder and flexor deformity is very complex and will
be discussed later.
conditions seen in many laminitic horses include: overfed, overweight
and under-exercised; stall confinement; being shod too young (as
yearlings); having feet that are too small and flexor deformities.
the white line will appear to be bright red, and the horse will
show no clinical signs of lameness. In the early stages of laminitis,
the horse will be stiff and frequently will be diagnosed as a
case of shoulder lameness. At the initial onset of laminitis,
the vascular apparatus of the sole is not affected. It is only
after laminae become damaged that the wall and third phalanx start
of the third phalanx is not present, then one can supplement the
diagnosis by running the finger down the middle of the leg to
the coronary band. If it encounters a depression behind the coronary
band, straight vertical displacement of the bony column down through
the hoof capsule (sinker) is likely. This is disastrous, as it
does not show up radiographically except at the coronary band,
and means that 100% of the laminae have separated. Furthermore,
this straight vertical displacement is often missed. It will show
only at the coronary band, anteriorly on a lateral radiograph,
and will have the appearance of the hoof capsule going proximally
up the leg.
sinking process is stopped, the hoof will slough. Due to the anatomy
and weight of the equine species, when the bony column sinks,
the coronary area of the hoof is jammed onto the coronary plexus,
cutting off the blood supply to the plexus. This is tantamount
to leaving a tourniquet on the leg.
We are all
familiar with the typical laminitis gait of "walking on eggs"
or "glued to the ground." Examination with hoof testers
indicates soreness anterior to the point of the frog.
horses we see are chronic. The condition has been coming on over
a period of days, weeks or months. The signs have just been ignored
or called something else, until the animal finally assumes the
typical stance. Many early cases are called "stiff-gaited",
"sore in the shoulders" or "stone-bruised".
Many have pads under the shoe to protect the feet. Many are also
on "Bute" or a similar product which will mask the clinical
Some of these
animals have obvious evidence of other clinical diseases such
as diarrhea, colic, retained membranes or pneumonia.
point here is that we have to look closely at these sore, stiff
or sick individuals to be aware that we may be dealing with an
early case of laminitis.
cases show no soreness to the hoof tester. Some appear lame only
in one foot but may be lame in the other foot after a volar nerve
pulse is always present; however, if it is pounding, this is an
indication of laminitis: the greater the laminar swelling, the
stronger the pulse.
both feet are mandatory. One pedal bone usually rotates before
the other. A lateral X-ray of the foot is taken to pinpoint the
amount of rotation. This is important to determine the exact location
to apply the support of the heart bar shoe. A helpful tip to determine
the exact location for support is:
Place a thumbtack
about 1 cm. back from the anterior tip of the frog before the
X-ray is taken. This is used only as a point of reference.
Take lateral X-rays with the foot on a block so that the X-ray
beam is parallel to the ventral border of the third phalanx.
X-rays are often negative in the early stages, but evidence of
previous problems may exist such as sole bruises, pedal osteitis,
or re-shaping of the third phalanx.
accurate diagnosis and prompt treatment are the responsibility
of the veterinarian, and will result in the majority of the horses
being returned to service.
begins with an accurate diagnosis and evaluation of the primary
problems can span a wide range, from no obvious signs of abdominal
abnormalities which respond to minimal treatment, to the other
end of the spectrum where we use antibiotics, sulfas, anti-inflammatory
drugs, fluids, plasma and blood.
It is important
in all cases to begin with a CBC and continue treatment until
it is within normal limits and all clinical signs have disappeared.
I (Platt) also routinely run a SMAC 20, which helps determine
which systems are involved. It is necessary to evaluate the electrolyte
balance, thus giving a baseline for subsequent comparisons.
The CBC ranges
from 2,500 to 25,000, with the differential counts being equally
varied. I (Platt) cannot categorize laminitis based on blood values.
The WBC is usually elevated in chronic cases of enteritis, and
it also rises with necrosis and abscesses of the feet. Acute cases
often have a depressed WBC value.
may result in laminitis within 24 hours. One should not wait for
the signs to appear. A gas-sterilized stomach tube is used to
flush the uterus with 3-5 gallons of warm tap water. The uterus
is filled and siphoned until all the membranes are removed and
the return water is clean. This is repeated 4-5 times daily until
the water is clean. I (Platt) use very few antibiotics in such
must be directed to the feet.
When the shoes
are removed, the sole is examined for bruises, blood at the white
line, and soreness anterior to the frog. Nerve blocks are used,
if necessary. A posterior digital block alone will not help a
laminitic horse. The anterior nerve must also be blocked to anesthetize
of pain is a significant clinical sign. In some cases, this pain
must be controlled to some degree, but by using the least amount
of drugs possible. If the laminae are tearing loose and the bone
is likely to rotate, it is wrong to mask the signs with pain-killing
drugs or nerve blocks. By using pain-killing drugs, the horse
continues to walk and cause more tearing of laminae hastening
the separation process. Two grams of phenylbutazone is the maximum
dose of anti-inflammatory agent used. I (Platt) never use a nerve
block for the purpose of exercise.
are removed and the sole cleaned and examined for soreness anterior
to the frog. Some of the early tell-tale signs of laminitis occur
visually in the form of bruises to the horny sole. This sign is
usually noticed while trimming the foot, in that red spots are
seen. They normally appear only in the front feet but occasionally
will be seen in the hind feet as well. The reason this problem
is more prevalent in the front feet is because two thirds of the
weight of the horse is carried by the forelimbs; however, the
hind feet are occasionally affected and require stabilization
of the third phalanx.
of the third phalanx can be accomplished with the use of the heart
bar shoe. A good analogue of laminitis is trauma to the human
fingernail: the nail becomes loose. A person can grow a new nail
but does not have to walk on that fingernail until it can grow
again! In order to enable the horse to grow a new hoof, it is
necessary to stabilize the third phalanx and support the bony
column. The blood supply to the sole and the third phalanx must
not be restricted in the process.
As noted earlier,
the frog has no major blood supply. There are a few capillaries
that are protected by the thick, horny cushion of the frog; thus,
considerable support can be applied to the frog without causing
In the early
stages, before the hoof is deformed, the foot should be trimmed,
as nearly normal as possible, to fit the pastern axis. The heel
should not be lowered in order to align the third phalanx parallel
to the ground. If the heel is lowered, it places more stress on
the deep flexor tendon, separating the third phalanx further from
If the rotation
is severe or the pain is severe in acute cases, one should remove
the anterior hoof wall. This allows space for the swollen laminae.
It allows drainage when the laminae are necrotic and sloughing.
It also removes the pressure exerted on the coronary band by a
loose hoof wall. It is not necessary to cover the tissue with
acrylic. We use merthiolate under a wrap to dry out the tissue.
The sole is
removed if abscessed or necrotic tissue is present. The object
here is to remove anything that is not normal. Constant debridement
of the sole is important. The sole is also treated with merthiolate,
which creates less proud flesh than does iodine.
If a farrier
is not present, which is often the case, a two-inch roll of gauze
is taped to the frog. The roll is flattened and unrolled to the
point where there will be even pressure on the frog and both hoof
walls. Elastikon tape (two-inch) is used and will stay in place
for 2-3 days. A piece of carpet, cut to fit the frog, can also
of support that one can apply to the frog depends on each individual
case. The amount of pressure depends on the amount of rotation
at the time of application and whether the sole is dropped. It
is recommended that one can start by shoeing the "worst"
foot first. The animal can stand on the so-called "good"
foot while the farrier is working on the "worst" one;
then, the foot will have some support when the horse is required
to stand on it.
bar shoe is prepared by the farrier. The amount of support is
as critical as the point of support, and cannot be left to chance.
The heart bar shoe is a precision instrument. It can cause much
damage, when not applied in the proper manner. It is the only
way we know to support the skeletal column of the horse. We have
some support under the bone and we do not have to rely on the
laminae to hold the whole horse.
OF THE THIRD PHALANX WITH THE USE OF THE HEART BAR SHOE.
bar of the shoe is usually made of 1/4" by 1/2" stock
and is V-shaped just like the frog. This bar, on the normal light
horse of today (Thoroughbred, Quarter Horse, Arabian, etc.), should
extend along the frog to a point 3/8" posterior to the apex.
A width of 5/8" is plenty for a hand made shoe with full
fullering, as this makes removal of the shoe much easier at the
time of reset. THE HEART BAR MUST NOT TOUCH THE SOLE OR BARS OF
THE FOOT. If a keg shoe is to be used, it should not be a wide-webbed
shoe. (A keg shoe is any manufactured, store-bought, machine-made,
presized, or stamped shoe).
The shoe is
shaped to the hoof wall and measurement is made to see how far
forward the bar should extend along the frog. When this measurement
is made, the bar is welded in place. It should be noted that anything
touching the sole will hinder the blood supply to that area.
toe is rolled severely until is turned up, resembling a sled-runner.
This is done to move the fulcrum of the toe posteriorly until
it is nearly under the distal end of the third phalanx. This reduces
the energy it takes for the deep flexor tendon to force (break)
the toe over and will diminish tearing of the laminae.
It is not
advisable to cut out the toe in the front of the shoe (open-toe).
A full rim pad is used in most cases. This is used to clear the
third phalanx off the ground when it has prolapsed through the
sole. I (Chapman) use a thermoplastic casting material. It will
not be attacked by iodine, copper sulfate or water. It is a very
good cushioning agent.
nailed on the hoof, the shoe is placed on the foot by hand and
squeezed down on the frog. If the horse moves away and acts like
it hurts, then there is too much support. This can be adjusted
by knocking the bar down a little. If the shoe is nailed to the
hoof and the horse does not want to bear weight on it or will
not put the foot on the ground, too much pressure has been applied;
the shoe should be removed and the bar adjusted. These shoes should
never be put on a horse that is nerve blocked. The horse must
be able to feel the pressure and thus indicate if the correct
support has been applied.
foot is shod, the horse is walked to see how it reacts; then,
the other foot is shod in the same manner.
been expressed to the effect that the heart bar shoe causes abscessation;
however, most of the horses I (Chapman) see already have serious
sepsis. After the heart bar shoe is properly applied, the sepsis
clears within 90-120 days - in less severe cases, frequently within
30 to 60 days. Use of the heart bar does allow better drainage
of the solar corium. Pressure on the apex of the frog does appear
to cause abscesses under the frog, especially when too much pressure
is applied or the angle is incorrect.
In any case
of founder, if the rotation is more than three or four degrees,
abscesses are likely. The shoe can be harmful if it is built or
put on improperly, especially if it touches the sole. It cannot
overlap the frog in any way, and the apex of the bar must never
extend over the apex of the frog. It should be at least 3/8"
posterior to the point of the frog. This is extremely important.
This is very
important. The hemograms are continued, and constant evaluation
of the internal condition, as well as the feet, is important.
The shoes must be reset every 3-4 weeks, and pressure evaluated.
If we are trying to return the third phalanx to its normal position,
X-rays must be taken.
cases with numerous abscesses have to be re-evaluated and treated
daily, and the feet have to be wrapped, soaked, etc. Proud flesh
must be controlled.
It is vitally
important that we understand the relationship between pain relievers
and a loose hoof, so we can prescribe the amount of exercise or
lack of same for each particular case.
If we use
pain-relieving drugs, we can create two important problems: (1)
abscesses can form without our knowledge but the early symptoms
are masked, and (2) too much movement may cause the animal to
tear loose damaged laminae, where they would normally be more
require exercise, but each must be treated as an individual. If
the whole wall is loose, then exercise is not recommended. Most
need to be walked at least 10 minutes, four times a day, or maybe
5 minutes every hour.
start "stiff and sore" but improve as they continue
moving. These horses do not need much forced exercise but they
do need to be moved at frequent intervals. They also do best if
kept in a pasture where they have to move to feed and water.
A good plane
of nutrition is necessary to promote healing and a feeling of
well-being. We prefer good pasture and/or alfalfa with oats or
a mixed grain ration. The only supplement I recommend is methionine.
STRAIGHT VERTICAL DISPLACEMENT
When it is
evident that the horse is affected with a straight vertical displacement,
a heart bar shoe should not be used. Instead, the heart bar shoe
should be simulated by using a thermoplastic casting material.
This, designed for human splints, can be heated in hot water and
molded into any desirable shape. A thermoplastic-material shoe,
with clips, is cut in the shape of the hoof. A triangular-shaped
wedge, also of thermoplastic material, is cut out to fit over
the frog and bradded to the simulated shoe. The material can be
0.6 cm. to 1.8 cm. thick, depending on how flat the sole is at
the time. A good average is 1.25 cm. This triangular-shaped piece
must not overlap the frog in any manner.
Next, a pad
of gauze, cotton or even disposable diapers is cut to fit around
the wedge to pad the sole. This padding must be thicker than the
frog support wedge. For example, if the wedge is 1.25 cm. thick,
the padding should be 1.8 cm. thick. This is all put together,
first by placing medicated gauze sponges next to the exposed laminae,
then molding the thermoplastic material clips (toe, quarter, and
heel) around the foot and taping the "shoe" to the hoof
with elastic tape. The horse is now bearing nearly all of its
weight on the frog. Palpation of the coronary area allows the
finger to slide rather easily over the coronary band.
will have the most severe sepsis, because of the widespread damage;
the coronary plexus, it is hoped, will still be alive. All laminar
vessels, laminae, venous plexus and, in many instances, the circumflex
vein and the circumflex artery are destroyed. It is rare for the
deep digital artery to be so damaged; however, if it is, the chance
for recovery is very remote.
When an entire
hoof resection is done, it is amazing how fast the hoof will regenerate,
taking 6-1/2 to 7 months to grow a complete new hoof. Constant
nursing care is essential to salvage these horses. Intermittent
suppuration occurs for 20 to 90 days. The entire area must be
treated as an open wound, the hoof being kept clean, bandaged
and turbulated daily. Also, the use of merthiolate and iodine
three basic reasons for removing the horny wall or doing a hoof-resection:
the pressure on the coronary plexus by the coronary edge of the
To debride any necrotic laminae entrapped between the third phalanx
and the wall. This can be treated as an open wound. Systematic
antibiotics are of very little value, as there is no blood supply
to carry medication to this area.
When pressure is applied to the third phalanx via the apex of
the frog, the anterior edge of the third phalanx will have no
resistance against it, thus forcing the third phalanx back into
a more normal position.
When sole abscesses occur, the feet should be turbulated daily
a in hot povidone-iodine solution every other day. Epsom salts
and hot water are used between, and the feet are treated and bandaged.
Reducine is not recommended in any instance of severe founder
where the horse is down and has decubitus ulcers. Hoofmaker and
ichthammol ointment have been more effective in my experience.
steps have been followed the horse should be taken off any medication
such as phenylbutazone or flunixin meglumine. These drugs should
be withdrawn slowly. Methionine, which exerts its maximum effect
within 45 days, is fed in the grain daily at the rate of 20 Gm.
per 1,000 lb. body weight. Turbulation, as noted is effective.
Merthiolate should be used on the exposed areas. We have found
that merthiolate has abetter drying effect and penetration. The
application of a good hoof conditioner around the coronary band
and heel is advised. The use of an acrylic to cover exposed tissue
is not necessary.
bar shoe or simulated thermoplastic heart bar shoe should be reset
regularly, approximately every four weeks. This is essential to
keep the correct support of the third phalanx. At each shoeing
the pressure should be re-assessed and adjusted to the individual
case. It is important that the feet be kept clean. Material packed
up next to the sole causes extreme pain. Severely lame horses
should be turned out in a pasture, if possible. A box stall is
not recommended but a clean stall should be bedded with straw.
Sawdust and sand are abrasive and contribute to decubitus ulcers.
Each time the horse is removed from the stall it will be stiff
but the farther it walks the easier it will be to move more freely.
Exercise depends on the severity of the individual case. Horses
which do not improve with exercise should not be forced to walk
because the exercise-induced pain is a result of tearing of structures
too weak to tolerate the pressure.
DEVICES AND RELATED PROBLEMS
The heel grows
faster than the toe on a foundered foot, the reason being the
reduced blood supply to the anterior wall. The coronary vessels
are compressed by the upward pressure of the loose anterior hoof
wall. Therefore, it is important to monitor the frog support because
the increased heel growth causes the heart bar to grow away from
the frog, thereby losing frog support.
are a new dimension that results in failure, unless diagnosed
early and corrected.
tendon deformities are the most damaging, because the tendon is
directly associated with the third phalanx. I (Platt) use inferior
check ligament desmotomy to gain relief for the deep tendon. If
this does not correct the problem, then tendon is cut.
of severe founder go on to abscess formation. Usually one foot
is worse than the other, but the degree of lameness is important
because the soreness increases as the abscess forms.
abscess is usually anterior to the point of the frog, and the
sole begins to bulge as it forms. The next location is lateral
to the point of the frog, along the border of the sole and the
wall. Sometimes, these are severe enough to warrant removal of
the entire sole. These abscesses must be opened as they form,
or they will undermine the sole and break out at the heel or work
up the laminae and break out at the coronary band.
are opened (if necessary) and flushed with hydrogen peroxide.
If the abscess breaks at the coronary band, the wall distal to
the abscess is removed and the area treated with peroxide and
The more severe
case requires removal of the hoof wall. If such is the case, a
heart bar shoe is built using Orthoplast, and the foot wrapped
using disposable diapers and tape. The bandage is changed daily,
using merthiolate to dry out the tissues until a new hoof grows
and can be shod. This takes approximately five months.
Lysis of the
third phalanx can occur from osteomyelitis and loss of blood supply.
The severe cases result in chronic abscesses. This problem is
corrected only by surgical removal of the damaged portion of the
third phalanx under general anesthesia. A tourniquet is applied
at the fetlock. All abscesses are removed, including the lytic
bone. A pressure wrap is applied for 48 hours to control hemorrhage.
A heart bar shoe made from Orthoplast and two disposable diapers
are applied to the hoof. The wound is treated daily with "sugardine"
and covered with disposable diapers. "Sugardine" is
a paste made from Betadine scrub and table sugar.
healing process has begun, it is treated with merthiolate. This
is usually around 30 days following surgery.
I have "cultured"
most of these lytic areas, and all of them have produced Gram-negative
organisms, and the most common being E. coli. I (Platt) use systemic
gentamicin on all post-surgical cases. As always, the hemograms
are monitored to determine when to discontinue antibiotic therapy.
These cases may be shod 60 days after surgery, with heart bar
on shoes and devices that work with very little consistency are:
(1) the egg bar shoe has no stabilizing effect on the bony column,
(2) the reverse shoe gives no stabilization to the third phalanx,
(3) the reverse wedge pad places more tension on the deep flexor
tendon thus causing more rotation, (4) the hoof cast compresses
the blood supply to the venous plexus of the sole if not properly
applied, and is dangerous for general use, (5) a bar shoe with
the bar across the center of the shoe sometimes squeezes the deep
digital artery, destroying the blood supply to the third phalanx,
(6) a pad with packing under it gives no stability to the bony
column and frequently causes pressure on the sole, destroying
its blood supply, and (7) a shoe that raises the heel and takes
the stress off the deep flexor tendon aligns all the laminae perpendicular
to the ground, causing the bony column to sink.
JAMES R. COFFMAN, D.V.M., M.S.
Mr. Chapman and Dr. Platt are to be complemented on their effective
application of anatomy, farriery and appreciation of systemic
disease process to bring about this improved approach to therapy
of horses affected by laminitis. Two principal considerations
are fundamental to a discussion of their paper.
of laminitis fundamentally is determined by the presence or absence
of unresolved underlying problems. Dr. Platt has stated that laminitis
is caused by some other problem and, that to manage it successfully,
that problem must be identified and corrected. This concept might
best be phrased in another way. The pathogenesis of laminitis
is essentially the same in all instances; the preponderance of
evidence suggests arteriovenous shunting, associated with peripheral
vasoconstriction and hypercoagulation (endotoxin being a likely
inciting agent). With this concept in mind, Dr. Platt's statement
can then be taken at face value. Certainly laminitis commonly
coexists and appears to be related to a variety of systemic disease
processes, the most common being cardiovascular disorders (including
verminous arteritis), gastrointestinal disorders (especially those
which denude the mucosa of the bowel), chronic respiratory disease,
renal disease and chronic liver disease. In chronic laminitis,
gastric and colonic ulcers, chronic renal disease and diffuse
lung abscesses are particularly common. Gastrointestinal ulceration
may be a pre-existing problem, the aftermath of the initiating
incident, or the result of chronic administration of phenylbutazone
or other non-steroidal anti-inflammatory agents. Chronic renal
disease frequently occurs in two forms: glomerulonephritis, as
an aftermath of onset events, and medullary necrosis, as a result
of phenylbutazone therapy. Diffuse or multifocal pulmonary abscesses
logically would be the result of bacterial emboli emanating from
septic foci in the feet via venous drainage. The presence of such
unresolved problems as those described above is, in my experience,
associated with a poor prognosis. However, horses with consistently
normal hematology and serum chemistry values, which do not have
degenerative changes in the third phalanx, have a good prognosis
when shod with heart bar shoes, particularly if they have been
affected for less than two months.