Many advances have been made over the last few
years in shoeing the laminitic horse. We have seen much
success in treating these cases but we still see far too many
failures. A couple of farriers have made significant strides
with their shoes - Burney Chapman with the heart-bar shoe1
and Gene Oveneck with his digital support system2.
Both of these shoeing procedures require attention to detail,
a skilled farrier and both procedures rely on posterior
support using the frog and related structures. Numerous other
methods of foot care have been recommended for treating
laminitis with varied success; the ideal has yet to be found.
We must remember that the outcome of these cases is directly
proportional to the extent of the lamella damage suffered
during the original insult. For the purpose of this
discussion, we will focus on the chronic laminitic horse. We
are still unclear in the veterinary profession as to when a
horse becomes chronic. Is it when radiographic changes first
take place within the hoof capsule or is it when rotation
and/or displacement stop? When should a laminitic horse first
be shod? This is a difficult question with no clear-cut
guidelines. Hopefully our medical treatment and foot support
in the acute stage was effective in halting the disease
process rendering the horse comfortable, on minimal medication
and having gone a reasonable length of time with no further
radiographic changes. It is at this stage that shoeing should
be considered. There are many horses that have such severe
lamella damage that they will not respond to any method of
therapeutic shoeing. Every laminitic case must be approached
on an individual basis and not every shoeing method will work
for every horse.
PURPOSE OF SHOEING:
The veterinary literature abounds with reports of corrective
shoeing for laminitis and distal phalanx rotation and/or
displacement. The primary purpose of shoeing a laminitic horse
is to protect the foot, minimize breakover, relieve dorsal
hoof wall pressure, prevent sole pressure and provide
posterior support by using the frog and heels of the foot3.
If the above five points cannot be accomplished then, in many
cases, the animal may be better left unshod. To minimize
breakover, the shoe should be placed just in front of the apex
of the distal phalanx (P3). Shoeing methods that increase
weight bearing through the hoof wall, especially in the toe
area, will increase pressure on the compromised lamina. This
may worsen or prolong the problem.
TYPES OF SHOES:
There are countless types of shoes used to treat laminitic
horses. Among the most popular are:
- the heart-bar shoe
- the egg-bar/heart-bar shoe (full support shoe)
- an egg-bar shoe with a square, rolled or rockered toe
- a reverse shoe which leaves the toe open, often used
with a frog support pad
- an open shoe with extended heels, using a heel insert
such as a frog support pad or rubber polysiloxanea
- Elite wedge shoes
- the digital support system shoe
- various types of glue-on shoes and modifications thereof
All of the above shoes allow us to address, to some degree,
the primary purpose of shoeing the laminitic horse. The above
list also allows the farrier to take into consideration his or
her individual skill level and particular interest in
therapeutic shoeing.
GOALS OF SHOEING
There are three main biomechanical forces imposed on the foot
of a horse with laminitis. Firstly, there is the vertical load
of the horse's weight placed on the hoof with compromised
laminae. An attempt to counteract this force is made through
various means of support. The second biomechanical force
placed on the foot is the proximal-palmar pull of the deep
digital flexor tendon (DDFT). Lengthening the shoe and
manipulating the hoof angle may effectively reduce it. The
last biomechanical force is the bending force or lever arm
placed on the compromised laminae by the dorsal hoof wall.
This force can be effectively managed by moving the breakover
point closer to the perimeter of the third phalanx.
THEREFORE, THE GOALS OF SHOEING THE LAMINITIC HORSE SHOULD BE
FIRST, TO EASE BREAKOVER; SECOND, TO DECREASE THE DISTRACTIVE
FORCE OF THE DEEP DIGITAL FLEXOR TENDON AND THIRD, TO SUPPORT
THE PALMER/PLANTAR PART OF THE HOOF. To ease breakover
effectively, radiographic guidance is used to place the shoe
just in front of the third phalanx. Breakover is further
enhanced by a square-toe shoe, a rolled or rocker-toe shoe or
the use of an open-toe shoe. This effectively decreases the
lever arm associated with the hoof wall (sometimes-excess)
present in front of the third phalanx.
To decrease the distractive pull of the deep digital flexor
tendon (DDFT), the heels of the shoe can be extended beyond
the heel of the foot. In addition to decreasing the force
exerted by the DDFT. The increased length of the shoe moves
the weight bearing function palmar/plantar and this appears to
further unload the toe. The assumption that less load is
placed on the toe is based on the fact that in subsequent
radiographs, there is a rapid increase in sole depth. Wedges
in the form of heel inserts (bar wedges) can be placed under
the heel if additional relaxation of the DDFT is necessary.
Palmar/plantar support can be accomplished through the use of
heart bar shoes. The heart bar shoe has the ability to
transfer much of the weight bearing function from the hoof
wall to the frog. Weight transfer can also be accomplished
through the use of wide-web steel or aluminum shoes, various
bar shoes, frog support pads and polysiloxane impression
material. (elastomere putty.) These methods utilize the
posterior portion of the foot, i.e. heels, bars and frog.
Addressing these three goals results in rapid growth of sole
which is necessary to protect the third phalanx and is
essential for long-term soundness.
RADIOGRAPHS
Emphasis must be placed on the necessity for current readable
lateral radiographs. From the radiographs, the clinicians
(veterinarian and farrier) can access the amount of rotation
and/or distal displacement of the third phalanx that has
occurred, the current position of the third phalanx and the
amount of sole depth that is present. Laminar separation or
abscessation can also be assessed. The radiographs are also
used as a baseline to follow the progression of the case at
periodic intervals. Of equal importance, the radiographs can
be used as a guide when trimming and shoeing the foot. When
taking the radiograph, a wire should be placed on the dorsal
surface of the hoof wall and another wire should be placed in
the top of the radiographic block. The horse should also have
a block of identical height placed under the opposite fore or
hind foot so weight bearing is evenly distributed. This allows
more accurate measurements to be drawn. Measurements can also
be made from the radiographs to determine the most accurate
point of breakover when fitting the shoe. This can be
accomplished by placing a radio-opaque marker near the apex of
the frog prior to taking the radiograph, and then measuring
the distance from this marker to the perimeter or tip of the
third phalanx. Alternatively, this distance can be measured
from the wire on the dorsal hoof wall. The amount of heel that
must be removed to realign the third phalanx within the hoof
capsule and the point on the ground surface of the foot where
the trimming should begin can also be accurately measured. The
degree of flexion in the coffin joint should be measured. It
has been our observation that chronic laminitic horses with
significant rotation and a high heel accompanied by marked
flexion of the coffin joint when weight bearing, require some
degree of heel elevation following trimming in order to become
comfortable. This can easily be accomplished with various
degrees of wedge heel inserts or, in severe cases, by an
inferior check ligament desmotomy or deep digital flexor
tenotomy. It is our feeling that chronic laminitis with
significant rotation results in a rapid shortening of the
musculo-tendonous unit of the deep digital flexor tendon.
SHOEING
Shoeing the laminitic horse should always be a combined effort
between a veterinarian and a farrier. Input from both parties
is necessary for a successful outcome. Over the last few
years, this author has been using a method of shoeing chronic
laminitic horses that encompasses the goals mentioned earlier
(minimize breakover, decrease the pull of the DDFT and support
the digit). The shoe has a wide margin of safety and is
relatively simple to construct. The foot is trimmed according
to the radiographs; the point where we want our breakover is
measured from the radiographs and marked on the sole of the
foot with a magic marker. The size and length of the shoe is
then determined. Our shoe of choice has been the plain or
wedge, Elite® aluminum shoe. These shoes have the properties
of being lightweight and easy to work with. The shoes have a
wide web, the nail holes are punched nicely and the fuller
extends back to the heels so it is easy to drill small holes
for additional nails, if desired. If the foot is bigger than
the available sizes of this shoe we usually employ a handmade
wide web steel shoe. The toe is squared on all shoes and a
grinder is used to roll the toe up to the inside of the swedge.
A grinder is also used to concave the solar surface of the
shoe. The inside edge of the shoe is placed so it corresponds
to the mark placed on the sole for breakover. This mark is at
or just in front of the third phalanx.
The length of the shoe should extend beyond the heels of the
foot to a perpendicular line drawn from the hairline at the
bulbs of the heels to the ground. The shoe can be lengthened
or shortened if necessary, depending on the conformation of
the foot. This not only decreases the distractive force of the
DDFT; it also shifts the weight bearing function to this area.
As a routine, we have placed at least a 2o wedge
heel insert under the shoe. The amount of heel elevation can
also be determined from the radiographs. This counteracts any
shortening of the musculo-tendonous unit of the DDFT. If there
is significant rotation or distal displacement, this is
accompanied by some degree of contracture of the DDFT. It may
be possible to remove these wedges gradually over time.
The last point to consider is palmar/plantar support. This can
be accomplished very effectively and safely through the use of
rubber-polysiloxane. This is a dental impression material
consisting of a putty base and a catalyst. When the two are
mixed together they cure to form a firm resilient material
that molds to the heel area of the foot. In this manner, we
are able to utilize all of the structures in the heel area,
which are capable of providing additional support, not just
the frog. After the shoe is fitted, plastic gutter guard is
placed between the shoe and the heel insert. The bar wedge is
attached to the shoe with copper rivets. The gutter guard can
cover the entire solar surface or an area on the bottom of the
foot from the point of the frog back. By placing the material
over just the frog, the sole can be monitored for
discoloration, seepage of serum or prolapse. The two
components of the polysiloxane are mixed thoroughly and pushed
through the gutter guard until the material is observed
underneath the heel insert. Additional material is added until
the elastomere putty is level with the ground surface of the
shoe, creating a platform-like structure. The foot is held off
the ground until the material sets (approximately one minute,
but varies slightly with temperature. Allowing the impression
material to cure with the weight off the foot assures that the
material forms a mirror image of the contour of the palmar/plantar
portion of the foot and to not be pushed out from weight
bearing. It therefore provides uniform support when weight is
borne on the foot. If there is adequate sole thickness noted
on the radiographs and the sole is intact, the entire solar
surface can be filled with the impression material. If the
shoe is of adequate length and the load has been concentrated
in the heel area, then the additional support to the sole
dorsal to the frog provided by this resilient material may be
beneficial. If the sole surface is compromised and requires
treatment, an aluminum treatment plate can be easily attached
to the shoe. The treatment plate can be fitted to the inside
of the swedge on the toe of the shoe so one doesn't lose the
function of the rolled toe. One-quarter inch Allen head screws
are used to attach the treatment plate. The screws are
countersunk in the treatment plate. This type of screw head
will facilitate breakover when compared to bolts or studs.
Forshams hoof packing can be placed in the screw heads in
between removal of the plate to prevent material from
accumulating there.
CONCLUSIONS
Success with this method is based on clinical impressions
and numerous cases which became comfortable post-shoeing.
Gross and radiographic improvement of the affected feet was
also noted on subsequent resets. Shoeing the chronic laminitic
horse is seldom curative and treatment usually entails
long-term maintenance. Regardless of the type of shoe used, it
is important for the veterinarian and farrier to consider the
biomechanical forces exerted on the foot and the use of
radiographs as a guide to trimming the foot for a consistent
successful outcome.
REFERENCES:
1) Chapman B, Pratt G. Laminitis. Proc Am Assoc Equine
Pract 1984; 30:129.
2) Ovnicek G, et. al. Wild horse patterns offer a formula for
preventing and treating lameness. Proc Am Assoc Equine Pract
1995; 41:260.
3) White N A, Leesburg, VA, Personal Communication, 993.
Advance Cushion Support- Advance Equine, P.O. Box 54,
Versailles, KY 40383 |
