Ridecamp: Re: [RC] navicular horse

Some Tips For Shoeing Navicular Horses
Or, Looking at the Problem from a Different Point of View
© Rob Kalb 1996
Based upon my previous and ongoing shoeing experience, combined with
lots of observation and study, I've formulated a theory about shoeing
horses with navicular. Please keep in mind that this is just my view
based upon what I know now, and that could change a year from now. But
by shoeing horses accordingly, I've had good results.
There are three conformation types contributing to navicular syndrome.
They are as follows:
Upright pasterns causing displacement of the navicular bone.
Shallow heels contributing to concussive and deep flexor pressure damage
to the navicular bone.
One leg being longer than the other. I refer to this as compressive-type
navicular syndrome.
Upright Pasterns
In the horse with upright pasterns, the job of the navicular bone has
been changed from its normal function. No longer does it act as a
fulcrum for the deep flexor tendon. It also has the additional increased
function of bearing weight, due to the angle of the joint between P2 and
P3. The angle should be normally close to 0 degrees. Instead of the
pastern and fetlock joint flexing towards the ground, as with a normal
hoof pastern axis, the fetlock flexes very little. This drives the
navicular bone out of its normal position.
The result is a stressing of the suspensory ligaments of the navicular
bone and the newly discovered chondrocoronary ligaments. Over time,
calcium spurs start to form at the medial and lateral aspects of the
navicular bone. When these spurs are forced into sensitive tissue by the
action of the pastern, the result is pain I feel that no shoe known to
man can correct this problem. The only way to make the horse comfortable
is to perform a neurectomy.

After surgery, I like to shoe the horse with as close to an unbroken
hoof-pastern axis as possible. Use a plain light or rim shoe with a
rockered toe. I?ll use pads if the sole of the hoof is unusually tough
or hard, in order to retain moisture in hopes of improving the shock
absorption properties of the hoof. I've been shoeing a horse like this
for two years with no hint of unsoundness. Early diagnosis and treatment
is always a contributing factor in determining the prognosis and outcome
of any case.
Shallow Heels
A low shallow heel on a hoof also means a thin digital cushion, causing
a decrease in the hoof's ability to absorb concussion. This condition
also puts the navicular bone closer to the ground. Hooves of this type
also have very little concavity, which adds to the problem. As a result
of the continuous concussive forces received by the navicular bone, it
starts to remodel. Remember: Bones react to stress and shock the same
way metal does. Bend a wire hanger back and forth repeatedly, and it
breaks. Bend it, then let it rest a while and the bend is harder than
the unbent portion of the hanger. Do this repeatedly - bend, rest, bend,
rest - the bend becomes very hard to straighten. In the horse, if the
bone is stressed almost to the point of failure, the body says, ?Hey,
wait a minute, we need more bone here.? It then sets up the facilities
to do so. In the case of the navicular bone, I feel that in some horses,
the stress is too constant, or frequent. The remodeling process
accelerates almost out of control, resulting in poor quality boney
tissue with sharp points and edges that inflict pain during the bearing
phase of limb motion.
To quote Dr. Dane Frasier, DVM, endurance rider, ?The horse?s body
responds to stress by adapting. If stress is placed upon a tissue group
repeatedly before the end of the adaptation period of that tissue group,
the result is failure of that tissue group. For hard tissue - bone,
tendon, and ligament - the adaptation period is 7 to 10 days.? By this
time you're probably saying, ?I thought he was going to talk about
shoeing navicular horses, not wire hangers and some endurance rider.?
Trust me it all comes together.
Remember, in the type of conformation were talking about here, the
hoof-pastern axis is usually broken back, the heels are low or
nonexistent, and there is little or no concavity to the hoof. Also, I've
noticed the hoof is disproportionately longer than it is wide, adding
pressure from the deep flexor tendon during the breakover phase of the
leg, to further complicate matters. All of these factors directly relate
to an increase in pressure and shock to the navicular bone, I feel,
stressing it to the point of failure. To shoe this horse correctly, we
need to eliminate or reduce these forces to the best of our ability. For
shoe type, depending on whether it is one or both hooves, with this
particular conformation, I choose from the following:
1) Tennessee navicular bar shoe, with or without pads, depending on the
degree of lameness and concavity of sole.
2) A hand-made roller motion shoe with SWELLED, not blocked heels, or a
keg shoe with heel caulks. We donut want the hoof sticking to the
ground. We want it to be able to slide, not hit and stick, sending this
jarring shock wave through the whole limb.
Also, I like to RADICALLY ROCKER THE TOE! Not 15 degrees as mentioned in
the Butler book, but about 45 degrees from the first nail holes forward.
There is usually a lot of toe that can be dropped back on this type of
hoof. Watch the horse move to see where the hoof breaks over. Is it
straight over the front or off to the side? If its off to the side,
rocker the shoe off to the side as well. Rasp the toe down to match the
rocker on the shoe, then finish seating the toe hot. Yes, burn it in.
This shoe will increase hoof angle, and facilitate breakover.
For pads, I like to use thick leather with just enough silicone to fill
the commisures or Hoofprints Impak pads with the same packing. If the
heels are really low and the frog is flat and thin when measured from
ground surface to the inside of hoof (you know when you look at it, and
push on it), I will use a steel egg bar shoe brought back to the bulbs
of the heel, toe rockered 15 to 20 degrees, and a 2- or 3-degree wedge
pad conservatively packed so as not to apply excessive pressure to frog
and sole of hoof.
I rarely use the Tennessee navicular bar shoe. I usually use it only
when both feet are affected. For more hoof angle, use wedge pads. If the
toe is farther from the fetlock joint than I'd like, I rocker it. I
don't set the shoe back to the white line and rasp the hoofwall down to
the shoe. This compromises the structural integrity of the hoof capsule
at the toe. By rockering the toe, I can significantly decrease the
breakover point, still thin the hoof wall to about half its original
thickness, and retain a structurally sound hoof capsule.
  The above-mentioned suggestions are designed to achieve the following:
Decrease concussion by increasing the size of the hoof with a bar shoe,
and dampen shock waves with pads and packing. Remember, when a horse is
galloping on a surface of hard packed dirt, each hoof receives an impact
of 310 G?s. On a 1000 lb. horse, that's 310,000 lbs. per hoof. The
larger the ground surface of the hoof, the lower the PSI of the impact
will be.

 Relieve pressure of the deep flexor tendon on the navicular bone. This
is achieved by raising the heels and facilitating breakover by rockering
the toes. I am careful not to raise the heels too much to avoid
transferring stress to the superficial flexor tendon, causing possible
problems in that area. I try to maintain an unbroken hoof-pastern axis.
The rule is: As the hoof angle increases, pastern angle decreases, the
deep flexor is relaxed, and the superficial flexor is tightened. I hope
Just put this thought in the back of your head: With the best of
intentions while trying to solve one problem, if you get carried away
you can easily cause others somewhere else. One leg longer than the
other (compressive-type navicular syndrome) This condition is fairly
easy to fix, if it hasn't progressed too far. I just stand the horse on
a flat, level, hard surface, get both front hooves side by side, use a
tape measure and measure from the ground to a point on the inside of the
knee that is an easily recognizable reference point. Are the two
measurements the same? If not, I look at the feet. Does one have a high
heel and the other a low heel? If so, the one with the high heel is
usually the short one.
Next I check the distance of the shoulder blade from the top of the
wither. Are they equal on both sides? I trim the high-heeled hoof and
try to get a hoof angle that will come close to matching the other hoof.
It is usually the low-heeled hoof that is afflicted with navicular
syndrome, because it is carrying more of the horse than it was designed
to do. I find that most farriers will put a wedge pad on the low-heeled
hoof. This is not good, as it further increases the load on an
already-overloaded leg. I've worked on horses that were shod this way
for quite some time. The result was a hoof that avulsed the hoof wall
from the second or third nail holes back to the bulbs of the heel, all
the way to the hairline. The heel bulbs dropped over the back of the
shoe almost to the ground. This is what happens when you lengthen a leg
that is already longer than it should be.  To beat all, no one can
figure out why the horse still wont go sound. Weave got him in a bar
shoe and wedge pad on that navicular foot and cant figure it out. Maybe
we should probably just put him down. But lets try to save him, instead.
I trim the low heeled hoof, leaving as much heel as possible, (that is
if there's any still there). I measure the toe length and try to get it
the same on both feet. For shoes, I use a shoe that fits the low-heeled
hoof the best.
The high-heeled hoof is usually smaller in size. I trim the heels to fit
the smaller hoof. With both feet trimmed, now I check the difference in
leg length. On horses with up to about a 1 inch difference, I?ll use a ¼
inch or 3/8 inch lift on the short leg. I can leave it as a full pad or
cut the center out and make a rim pad.

Before applying the shoes, I measure from the end of the toe on the
high-heeled hoof to the center of the fetlock joint. I check this
measurement with that of the other hoof. If on the low-heeled hoof the
distance is greater, I rocker the toe to move the breakover point to
that of the high-heeled foot. This means that if you measured 4 inches
from the center of fetlock to toe on the high-heeled foot and 4 ¾ inches
on the low-heeled foot, rocker the shoe and hoof ¾ of an inch back from
the toe end. If I need to go further, I make sure I have enough foot to
do it. This will get both hooves breaking over at the same distance from
the center of the fetlock joint. The result will be an easing of the
pressure from the deep flexor tendon on the afflicted navicular bone.
The lift on the short leg will get it carrying more of the load. This
arrangement should build up the shoulder muscles in the short leg,
making both legs the same length fairly quickly. It usually works in one
to three shoeings. Remember not to get carried away with the thickness
of your lift pads. If the knees are not the same distance from the
ground on the first shoeing, that's OK.
I hope this information is taken as a guide to help look at these horses
in a different light. I have shared it with you because it works for me
most of the time. Not every procedure works the same on every horse. It
is my hope that some of you other Farriers will try it, add to it or
detract from it, as you so wish. But most of all, I hope that by using
these guidelines, and adding your own ideas and intuitive decisions, you
are able to restore a comfortable and useful life to horses that were
otherwise thought to be hopelessly lame.

--
Rob Kalb
Rob's Equine Hoof Care
Phelan CA



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