Mediolateral Balance 10-22-04 Pete Ramey with 2018 edits
When I was first learning the farrier trade, I was fortunate enough to be taken under the wing of an old shoer right before time caught up with his wrecked body enough to put him out of business. He had been taught decades before by another old shoer, and I doubt very seriously that either of them had ever read a paragraph of a farrier text and definitely not a veterinary paper. My mentor's methods were very simple. Keep the horses barefoot and routinely trimmed during the off season to drive up the sole, keep the heels low and the shoe way back under the horse. “Cheat” the toes back if you need to so he doesn’t trip on them, leave the frog alone and most of all, leave the healthy sole alone and let it tell you where the foot wants to be. In fact, I am pretty sure I never really used a hoof knife until I was on my own – at least I know I never needed to sharpen a knife under his watch. We just scraped away any loose flakes of exfoliating sole and leveled off the walls above the remaining sole plane in prep for the shoe.
His nutritional knowledge was apparently limited to a strong
distaste for fat on a horse – he liked muscle and ribs. “You’d
better back off on that horse’s feed or he won’t be able to
carry you anywhere.” That is pretty much all I remember, as far
as the horses and their hooves go; the rest was all about the
metal work.
As I later studied
deeper into corrective shoeing and worked hard to educate
myself, I became obsessed with the world of hoof gauges,
measurements, T-squares, formulas, dots, bridges, COAs, HPAs,
ratios and mapping. I came to think my old teacher as a “cowboy
shoer”— incompetent even. I failed to notice the fact that the
people in the fancy barns who used the more-expensive
educated farriers with the high-dollar rigs (and 100 reasons
to cut sole from the horse) had horses and hooves that were
wrecked with problems. I also conveniently forgot for a while
that very few of the horses in my teacher’s care ever had a
problem at all. When they did it was usually from some injury
and not sore feet. Which came first, the chicken or the egg? My
answer at that time would have been wrong.
Since then, I have
systematically had to unlearn many of the things I learned to do
to the horse that once made me feel superior to my old mentor
and at the same time developed a deep respect for the pure, raw
effectiveness of his simple, "uneducated" ways passed down
through the generations.
He balanced trims
and shoes using the horse’s natural sole plane. I never saw him
cut into the sole on one side to achieve some mediolateral
balance goal. After a short trip into other methods, I have
realized that more often than not, his method works the best.
But I have seen the sole plane be wrong, so as always, the truth
is not quite so simple – it depends.
First, what is my
idea of correct mediolateral balance? In over 99% of hooves, I
believe that the best you can do is leave the same amount of
sole covering both sides of the coffin bone and both sides of
the lateral cartilages. Then leave the same amount of quarter,
heel wall and bar standing above that sole on each side. Even in
most horses with angular deformities, the limb can torque
towards straightness when the ground-balanced foot is loaded,
providing the best chance of adapting the joints toward
straightness.
But… I have seen
horses with malformed or remodeled coffin bones that were
thicker on one side and joint spacing up the limb correct only
when the ground plane of P3 is tilted up out of a parallel
orientation to the ground. I have seen joints seized in
positions that would not let the bottom of the foot reach the
ground on one side. And I have seen arthritis cases that show
pain reaction to a balanced foot and move better when the
internal foot is out of balance with the ground. I do believe
that most of these cases were caused by long-term balancing with
the hairline or by T-squaring to the limb. Regardless of the
cause, once this damage occurs, it is often best to do whatever
you can to provide comfort. This can mean intentionally
imbalancing the foot to provide pain relief and to support
permanent imbalances in the limbs. Understand, though, that in
these cases you are in salvage mode, not rehab mode.
These cases are best identified and treated with radiographs, by
studying the movement of the horse, and through experimentation.
Those exceptions
aside, the vast majority of the time it is best to balance the
internal structures of the foot (P3 and the lateral cartilages) to the ground. To accomplish
this in the field, I combine four very flawed indicators:
1)
Radiographs
Looking at a
quality zero degree DP radiograph, it is easy to measure and
compare exactly how much sole is on each side, thus to determine
if the mediolateral ground plane of P3 is parallel with the
ground. This is a very useful tool for sorting through imbalance
issues, but it has a big flaw – you can really only see the
mediolateral balance in one spot near the widest part of the
foot on a radiograph. You can’t see heel or toe balance.
A secondary flaw is that we often don’t
have radiographs available. Even if we do, if they are a month
old or more, they generally aren’t of use in the field for
making balance decisions. All that said, the first thing I do
when I am in doubt about a balance decision is order zero degree
DP radiographs – they can be very enlightening.
2)
Collateral Groove Heights off the Ground
As discussed in
http://www.hoofrehab.com/HorsesSole.html,
the collateral grooves provide a very important window into the
internal foot, because very consistently, it is approximately 7/16” (9mm) from
the bottom of each groove to the corium. So you can use the
collateral grooves to locate the coffin bone and the lateral
cartilages. If you measure the collateral groove depths on each
side of the foot and find that both sides are balanced with each
other, P3 and the lateral cartilages are probably balanced with
the ground. I generally compare the depths on each side an inch
behind the apex of the frog and at the deepest point, usually at
mid-bar. When you measure, try to hold the gauge either
vertically, or on the same angle on each side (sometimes
difficult or impossible at the back of the foot, but do try).
Figures 1, 2 and 3
There are two
scenarios I know of that cause the information provided by the
collateral grooves to be wrong. First, when there has been
simultaneous abscessing of the frog and solar coriums, the sole
and frog can disconnect creating a false sole and frog,
including a false collateral groove. Hopefully there are new
soles, frogs and accurate collateral grooves growing in
underneath, and eventually the false material will shed off
(hopefully after the new growth is approaching full thickness).
Until then, the information provided by the collateral grooves
is pretty useless.
The second scenario
that alters normal collateral groove distances to the corium is
fungal or bacterial infection. These are common in the central
sulci of the frogs (in fact I consider central sulcus infection
to be one of the most important lamenesses in horses – not just
because of how common they are or the pain they cause, but
because of the effects of the resulting toe-first compensation
that then thins soles at the toe, causes navicular damage,
destroys lamellar attachment and damages joints, ligaments,
tendons…). These infections are considerably less common in the
collateral grooves, but it does happen. Collateral groove
infections can eat their way to (even into) the corium, making
collateral groove measurements unusable. Be suspicious of
collateral groove measurements if you find pain response,
cottage cheese-like residue, or find the distinct smell of
fungal infection in the collateral grooves.
Even with these two
occasional exceptions, comparing collateral groove balance is
by-far the most accurate and reliable of the four indicators.
The biggest problem is that at the back of the foot, we don’t
always have access to the information hiding there – some
collateral grooves are too tight to accurately measure – you
sometimes don’t really know if you are measuring to the true
bottom or not. This fact alone makes these measurements just one
more useful indicator, rather than a solid stand-alone method of
balancing the lateral cartilages and P3 to the ground.
Critical Note:
The flexible
lateral cartilages tend to adjust to a preloaded position that
is prepared for the most common way that foot hits the ground
(for instance, lateral side higher in a hind foot of a horse
that is worked a lot at speed and reaches underneath the midline
at each stride). So it is okay if one lateral cartilage resides
higher on one side when the foot is at rest, dangling in your
hand. The caudal foot twists and distorts vertically at impact
to accommodate moving through turns and uneven terrain – you
still need to balance the sole, bar and heel wall the same
thicknesses covering each lateral cartilage, even if it appears
you are leaving the foot imbalanced because of this resting or
neutral position of the lateral cartilages.
3)
The Hairline
If a horse has been
well-maintained, has been moving correctly and has been
continually in balance, long-term, the coronet/hairline will be
ground parallel at the toe (when viewed from the front from
ground level) and also at the heels (when viewed from the back
from ground level). So it is common for people to use the
coronet as a stand-alone method. This is a mistake, because the
coronet lies and it lies often. If either excess load or excess
wall length (usually caused by less load/use/wear occurring on
that side) has been common on any area of the hoof wall, the
coronet migrates proximally (moves up the limb, relative to P3
and P2). If an area of
the wall has commonly been unloaded, the hairline migrates
distally (moves down the limb). This range of motion – where the
hairline might be currently residing relative to P3 and the
lateral cartilages – can vary by an inch or more.
This fact makes the
hairline the least accurate of the four indicators. That said,
it does provide useful information about how the horse has been
moving and how the horse has agreed with previous balance
decisions. It is the most common way I first notice balance
issues when a horse walks up to me. You just have to take the
information provided with suspicion and then look to the other
indicators for confirmation.
4)
The Sole Plane
Horses have a very
strong tendency to callus the sole in a very uniform sole
thickness on each side of the foot. Additionally, even if you
are removing excess sole, if you exfoliate a sole down to the
same texture/moisture content on each side, the thickness on
each side will generally be in balance. In a vast majority of
cases, you can simply use the sole plane to balance the foot,
leaving the same amount of heel, wall and bar standing above the
sole on each side, as in the before and after trim pictures
below.
The flaw to this
method is that sometimes the sole does lie. Excess wear can
occur on one side, retained false sole can look exactly like
good callused sole on the other side of the foot. Donkeys, mini
horses (commonly) and some normal-sized horses (rarely) can grow
excess sole that fails to callus or change textures as it moves
away from the corium. Given the limitations of the other three
indicators, even with these exceptions at play, day in and day
out, the sole plane is our best indicator of mediolateral
balance. You just need to consider the other three so you don’t
get fooled when one of these exceptions occurs.
Putting It All Together
When I start a new horse, on each
individual foot, I consider all of the information I have
available from each of the four indicators. I watch the horse
move, looking for feet that land out of balance – ideally, I
want both heels on each foot to impact the ground simultaneously
when the horse is trotting in a straight line. I want the entire
foot to land flat to the ground when the horse is walking in a
straight line. This provides important information, but be
cautious with this indicator as well – some horses avoid pain on
the bottom of the foot by voluntarily side-loading. These horses
need treatment for whatever is causing the pain, but they still
have the same mediolateral balance needs as discussed above.
Once I get to know a horse – if all of the
indicators seem to agree with each other and there is no
evidence of imbalanced movement (excess wear on one side, one
bar or heel trying to flare, crush or roll under, etc.) – I tend
to shift to only using the sole plane for balance during
maintenance trims. If I do ever see any suspicious wear
patterns, distortion or movement, I immediately shift back to
gathering all of the information I can from the other
indicators.
In a nutshell, I am
processing the information from four very flawed sources (five
if you count the footfalls) and then guessing at mediolateral
balance. That sounds bad, I know, but it works much better than
considering any one of them alone. After all is said and done, I
seem to be good at sorting through imbalance issues, so I
suppose standing on shaky ground while thinking can be better
than being solidly and mindlessly entrenched in any one method
that can fail you.
Asymmetrical Feet
When viewed from the
front or back, many coffin bones have a steeper side and a more
sloping side opposite of each other. Likewise, the quarter walls
will also have steeper and more sloping sides. Generally
speaking, when these horses were born, the coffin bones and
walls were at the same angle on each side. This very common asymmetry is a
product of the way the individual horse moves – a remodeling,
perhaps an adaption. The side of the foot that has been
continually used more/loaded more by the horse will remodel into
the steep side of the foot. The side of the foot that is used
less/loaded less will remodel into the more sloping side of the
foot.
Most commonly, the
steep/more-used side of the front feet is the medial side,
unless the horse has angular deformity (toes in) at the lower
limb joints. In these cases, the steep/more-used side will tend
to be the lateral side. On hind feet, the steep/more-used side
will more commonly be the lateral side, as horses tend to reach
the hind limbs underneath the midline during normal movement,
placing more load on the lateral wall. Various problems, usually
hip or back problems can prevent the horse from moving this way,
usually causing the steeper/more-used side of the foot to be on
the medial side.
These steep and
flared sides of the foot need to be recognized and treated very
differently than each other. Horses are very good at slowing
down or speeding up the growth rate of the walls to accommodate
the current demand. They are not very good at growing different
amounts of wall on each side – high wear/demand in one spot of
the wall tends to accelerate the wall growth everywhere.
What very commonly
happens to these feet with distinct steep and more sloping sides
is that the wall’s growth rate will be perfect for the higher
demand at the steeper/more-used side of the foot – this side of
the foot will often self-maintain if given a chance, with little or no trimming
needed. But this almost always translates to excess wall growth
on the more sloping/less used/less wear side of the foot.
The result of this constant excess growth is wall flare that is
very difficult to grow out.
These less-used
walls seem to overgrow and flare overnight because they are
growing at the same rate required by the more-used side of the
foot. It is difficult (and expensive) for a hoof professional to
get to a horse often enough to trim the walls before
they overgrow and flare, spreading separation into the new
well-attached growth. A useful trick is to teach the horse owner
to trim only that overgrowing, flared side of the foot on a
weekly basis. This stops you from wheel-spinning, when trying to
grow out the wall flare while working the rest of the foot on a 5-week trim cycle.
The most useful
trick for growing out these flares, though, is being careful not
to artificially accelerate the growth rate of the walls. This is
done by never trimming any part of the wall (this applies to
bars as well) that is not overgrown. Sounds easy – but it is the
hardest thing in the world for a professional to do – we tend to
want to leave it all pretty, shiny and clean. But any part of
the foot that is not overgrown should be left dirty. Only trim
those parts of the wall that are overgrown, or you will
artificially accelerate the growth everywhere.
I learned this from
teaching horse owners to trim their own hooves by doing weekly
light trims. If they were trimming the entire wall, they would
get the walls growing so fast they had to do big trims on
a weekly basis or the walls would overgrow and flare between
trims. Weekly trimming is great, and is the very best way to
grow well-connected walls – but you must only trim the parts of
the wall that overgrow, using the parts of the foot that
self-maintain as a guide for determining how much wall the
individual horse needs standing above sole in a given terrain.
In the before and after trim pictures below, the [right in
photo] side of the foot self-maintained perfectly during a
six-week trim cycle. It was left alone. The overgrown [left in photo] side
of the foot was trimmed to match the height above the sole and
the angle of the roll on the wall. This slows the growth rate
down, making it possible to grow out the wall flare using a
reasonable trim cycle.
Figures 4 and 5
For heel height discussion, read
http://www.hoofrehab.com/HeelHeight.html
Now to the Tricky Part - Balancing Asymmetrical Feet
Very often these
feet with distinct more- and less-used sides of the foot will
have good wall connection on the steep side of the foot because
this side of the foot has never overgrown. In contrast the
less-used side of the foot will have big wall flares because
they have constantly overgrown. Growing out these big wall
flares requires big trims to relieve the lever forces on the
walls (by the way, once you have identified a side of the foot
the horse doesn’t use much, you can get away with very aggressive
trimming on that side without making the horse tender-footed or
particularly at risk of bruising the sole - that tidbit was
worth the price of admission).
The trim required to
grow out the flares (generally, trim the walls to the level of
the sole and bevel/roll the full thickness of the wall) leaves
the sole with no wall protruding past it (or commonly, the wall
is already flared out level with the sole when you arrive). This
leaves many practitioners (including me, for many years) to
automatically over-trim the well-connected side of the foot in
the name of mediolateral balance. You may know the
well-connected side needs 1/4" of hoof wall standing above the
sole, but you trim it off anyway, because you need to balance to
the lack of wall height on the flared side of the foot, right?
This artificially accelerates the growth rate on both sides of
the foot, making the flare difficult-to-impossible to grow out.
To break out of this
trap, treat each side of these feet independently. This sounds
really wrong, I know, but this foot is not loading in a balanced
way no matter how you balance it. Plus, it turns out that in
most horse terrain that the foot can sink into a bit, this does
not imbalance the load or movement. The horse is balancing on
greater surface area of the sole and frog. That 1/4" of wall
standing longer than the sole just sinks into the dirt, offering
little-to-no resistance. Think of a snowshoe with a 1/4" thicker
frame on one side – it wouldn’t affect your movement through
snow.
Important Note: This does not
apply to hard, flat terrain. Hooves adapted for this type of
environment tend to need walls that are trimmed to or worn to
the level of the sole so that the wall and sole can share the
load.
Once you succeed in
growing well-connected walls on both sides of these asymmetrical
feet, start balancing them normally, allowing the same amount of
wall, heel and bar to stand longer than the sole on each side. This was a
temporary measure to break out of a trap.