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Subject: Club Foot (Long)
From: lbm@avs.com (Linda B. Merims)
Date: 29 Nov 1993 23:58:55 GMT
Organization: Advanced Visual Systems Inc.
Jonas Herbertsson wrote:
:I have a 9 yo Swedish WB mare with a strange front foot. I haven't
:found out why this foot is different from the other but have some
:theories about it. Has anyone else seen this phenomenon and/or
:have any theories about it?
:
:- The right front foot is slightly smaller than the left one.
:
:- It grows significantly faster than the left one.
:
:- It has a slightly concave side profile at the toe.
:
:- If left unattended by the shoer the heel will be too high and
: the back of the foot will be very narrow.
This is, alas, something I know all too much about. The condition
is called "club foot." It is widely thought to be an inherited
defect, though it can easily skip generations. No studies
have been done that document and describe its heritability.
Indeed, the entire state of formal research on this defect is
abysmal. This may change as it is becoming a significant
problem in thoroughbred racing lines.
I know about it because the weanling Morgan filly I purchased
began to display this defect at about 9 months of age. This
set me off on a long, confusing, discouraging, but ultimately
somewhat enlightening search for information. This included
a literature search through the Cornell Vet School library.
WHAT IS IT?
You will never get anybody who can tell you exactly what is
wrong. All you will get is a description of the phenomena,
to whit:
||
||_ canon bone (base--fetlock)
//
Normal foot //_ first distal phalanx (P1--pastern)
//_ second distal phalanx (P2--short
pastern)
// third distal phalanx (P3--coffin bone)
||
||_ canon bone
//
Club foot //_ first distal phalanx (P1--pastern)
//_ second distal phalanx (P2--short
pastern)
|| third distal phalanx (P3--coffin bone)
The third distal phalanx (P3--coffin bone) is not in a smooth line
with the first two phalanxes. It is rotated to _some_ degree behind
the line it should be. Therefore, the bottom of the coffin bone is not
parallel to the ground. The horse is therefore standing to some
degree on its toe.
Appearance and Onset
Age at clear manifestation is about 9 months. Problem worsens
for two to six months, then stabilizes. After this period, the
horse doesn't become "more" club footed. Onset is probably earlier,
but only becomes obvious to the casual observer at about 9 months.
It doesn't appear to be caused or mitigated by anything in the horse's
environment.
For reasons nobody knows, 80% of club feet are in the off fore.
Only 20% occur in the near fore.
The foot takes on a dished profile. It is upright and boxy.
The heel grows faster than the toe, and the rear bulbs of
the hoof are round and full.
Though rotated, the coffin bone starts out wholly and correctly
attached to the front hoof wall.
The club footed horse cannot extend its coffin bone (and hence
point its hoof) to normal limits during a stride. Depending upon the
degree of club footedness, the horse travels short on that leg.
Sometimes it isn't even noticeable. Sometimes the horse is clearly
uneven, tied in, even limping.
Taxonomy--Degrees of Club Footedness
There are degrees of club-footedness. The best article I ever saw
on this was by a research vet named Rooney at the University of
Kentucky at Lexington, published in _The Blood Horse_ about three
years ago. Rooney taxonomized the condition like this:
Grade I -- slight rotation, may not even be apparent from the outside.
Grade II -- marked rotation, dished profile.
Grade III -- rotation more pronounced. Significant misalignment
also occuring in P1 and P2 as they are "pushed up"
by P3. Profile of front rim of coffin bone visible
as a crescent on the bottom of the hoof.
Grade IV -- front of coffin bone is vertical or behind the vertical.
Grades I's and mild II's can often compete without "the bad stuff" starting
to occur. Racehorse Easy Goer has a Grade I-II club foot (which ain't
going to help his value at stud). Grade III's are likely to have
have significant problems with anything more than the very
lightest use. Grade IV's are in very bad shape. Rooney said that
an estimated 20% of thoroughbreds foaled now display club footedness
to some degree.
Club Foot Not the Same As Contracted Tendons
A club foot is _NOT_ the same thing, though it is similar, to contracted
tendons. (Contracted tendons are bilateral instead of unilateral, occur
earlier in the foal's development (about 6 months), are affected by
environment, and are more amenable to corrective surgery. This is also
an inherited tendancy. For example, in Morgans, it is rampant in the
Waseekas In Command horses.) Vets will, however, often refer to a club foot
as "a contracted tendon," or "deep flexor contracture." Get them to clarify
which they mean. Unilateral is the tip-off. Also be aware that there is
something called a contracture of the superficial flexor tendon--but that's
a different story.
WHAT IS REALLY WRONG?
What actually seems to be wrong here is that, for some reason, the
deep flexor tendon, which attaches to the back of the coffin bone,
is pulling the coffin bone back from where it should be. What's
wrong? Nobody knows. Theories abound:
- the tendon is too short, or doesn't develop evenly at that
point in the foal's growth
- the leg is longer than the other leg
- the leg is shorter than the other leg
- the foal grazed one-footed too long and shortened
his tendon (the "grass foot" theory--markedly club footed horses
always graze with the club foot beneath them and the non-club foot
extended. They never exchange legs.)
- the inferior check ligament which attaches the deep flexor tendon
at its mid-point to the top of the canon bone is too short and
the tendon can't stretch as much as it should
- it is a secondary effect of other leg defects
- misshapen base of canon bone resulting in unstable flexor tendons,
which "tighten up" in an effort to stabilize the leg
- calf knee
- my own off-the-wall theory is an ingrown frog
TREATMENT
Two treatments exist:
1. The traditional treatment has been to carefully keep shaving down
the horse's heel to bring P3 into more normal alignment. The idea
is that you keep gently removing heel, letting the weight of
the horse slowly "stretch" the deep flexor tendon back to where
it should be.
2. The new treatment is desotonomy of the inferior check ligament.
You cut this ligament (which acts as the emergency brake to
prevent the coffin/deep flexor from hyperextending), thus letting
the deep flexor "relax" and take the pull off the coffin bone.
Treatment Called Into Question
Treatment 1 is now being discredited by research (that was one of the
main points of _The Blood Horse_ article) as being counterproductive.
However, that's what most farriers have been taught and you're going to have
a devil of a time talking them out of it.
The Bad Stuff--What Eventually Goes Wrong with a Club Footed Horse?
The reason this therapy is being discredited has to do with all "the bad
stuff" that can start happening to a club-footed horse undergoing use
heavier than the leg can stand:
- The front rim of the coffin bone is rotated. In Grade III's, it
is even visible as a crescent in the bottom of the hoof. With
heavy use, the leading edge of this coffin bone can chip and
start to deteriorate. This is very serious for the eventual
utility of the horse. It is essentially a broken foot.
- Eventually, the laminae holding the coffin bone to the hoof wall
begin to break down, and you get a mechanical founder--the coffin
bone separates from the hoof wall.
Shaving Heels Considered Harmful
The problem with Treatment 1 is that it rests on the theory of
gently "stretching" the deep flexor tendon. An attractive theory.
Rooney says this is nonsense. By shaving the heels:
- you have removed the horse's base of support at the heels.
The dynamics are complicated without a diagram, but essentially
you have set up a tug-of-war between the laminae and deep flexor
tendon. Rooney says the deep flexor tendon is going to win and
you will get mechanical founder.
- because the horse can no longer land flat on its foot, it is
going to jab its toe into the ground at every stride, concussing
the leading edge of the coffin bone.
I agree with Rooney. This is _exactly_ what happened to my filly
(a Grade III) after her various "therapeutic" heel trims. After a trim, you
could slip a piece of paper 3/4 of the way under her foot. She
was standing on her toe. No deep flexor "stretching;" the rotten
dynamics set up by this situation only slowly corrected itself
as the heel grew out again. By 18 months she had coffin deterioration
and separation from the hoof wall. By 2 she was a lame horse.
High Ringbone
The downside to letting the heels get long is another side effect:
- P1 and P2 are also being pushed up out of alignment. You are likely
to get progressive high ringbone (arthritic bone spurs on the outside,
non-weight bearing parts of the joint) where P1 and P2 meet.
High ringbone, however, is not as serious as the effects of trimming heels
too much.
Trim--But Not Too Much
You _do_ have to trim the heels on a club foot more often than on
a normal foot. The trick is to only trim the excess and never
so much that the horse is not bearing weight and landing unevenly on the foot.
This way, you avoid putting strain on the deep flexor/laminae. Never try
to "carve" a normal looking foot out of a club foot. Never try to make
it match the other foot. (Good luck debating this with your farrier.)
Honest, they do better with a long heel. (Jonas, if your horse is healthy
and happy with how she's being trimmed now, great, don't change.)
Efficacy of Desotomy Questioned
Treatment 2, desotomy of the inferior check ligament, was originally
developed as a treatment for bilateral contracted tendons. When performed when
the horse is very young (before 2), it can help the situation. However,
studies on the efficacy of the surgery have not distinguished between club
foot and contracted tendons. It is now being thought that it is more
effective for contracted tendons, and only moderately effective to
ineffective for club feet. (It helped my filly only a little.) It is
also questionable whether a horse without an inferior check ligament should
be racing or jumping.
SUMMARY
A horse with mild club footedness can lead an active, athletic life.
But, the greater the degree of rotation, the worse the skill exercised
with heel trimming, the harder the use given the animal will all
contribute to development of "the bad stuff." (I havn't heard of navicular
problems being associated with this defect, but all that means is that I
havn't heard it.) Too much bad stuff and you have an unusable horse.
You take side x-rays to determine the degree of rotation, and of separation (if
any) of the coffin from the hoof wall.
You take bottom x-rays to determine the degree of chipping/degeneration
in the leading edge of the coffin bone.
Nerving for a horse in distress over the long term secondary effects of
a club foot is available as a last resort. It really fixes nothing, but may
alleviate the horse's distress.
If you breed such a horse, you may luck out and get a normal foal.
But somebody down the line is going to start scratching their
head when _their_ foal is about 9 months old when they begin to
notice that one of their feet (probably the off fore) is starting
to look awful funny.
Linda B. Merims
Waltham, MA
(I guess you can tell this got to be a bit of an obsession with me.)
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