The wooden shoe as an option for treating chronic laminitis
Reprinted with permission from Equine Veterinary Education (EVE). Original published in Equine Veterinary Education Vol 21 Febuary 2009.
S. E. O'Grady* and M. L. Steward†
Northern Virginia Equine, PO Box 746, Marshall, Virginia 20116; and †Shawnee Animal Hospital, 1509 North Kickapoo Street, Shawnee, Oklahoma 74804, USA.
Various farriery methods have been described for treating
chronic laminitis, yet no particular method has become
the preferred choice. The wooden shoe may possess
certain advantages such as redistributing load evenly over
the palmar/plantar section of the foot due to its flat solid
construction and the mechanics (bevelled perimeter,
breakover and heel elevation) that can be incorporated
directly into the fabrication of the shoe. It should be
apparent that the advantages of this farriery option will
also be limited unless strict attention is paid to the details
involving radiology, foot preparation and alignment of the
distal phalanx within the hoof capsule.
Chronic laminitis is a frustrating and often disheartening
disease for veterinarians, farriers and horse owners to
manage. Our ability to rehabilitate horses with laminitis,
despite the type of farriery employed, is related to the
severity of damage to the lamellae (Hunt 1998). For this
reason, treatment failures with any given methodology are
commonplace. Chronic laminitis is defined by the
presence of mechanical collapse of the lamellae and
displacement of the distal phalanx within the hoof capsule
(Hood 1999). The various forms of displacement of the
distal phalanx recognised are: dorsal capsular rotation,
distal displacement (sinking) medial or lateral
displacement of the distal phalanx or any combination of
the above (O'Grady et al. 2007a; Parks and O'Grady
2008). The most common type of displacement
encountered is dorsal capsular rotation. If dorsal capsular
rotation is severe, the instability of the distal phalanx
combined with the weight of the horse often leads to
prolapse of the sole or penetration of the distal phalanx
through the sole. The wooden shoe has become another
farriery option that has been found to be a consistently
successful method to address dorsal capsular rotation
(Fig 1) (Steward 2003; O'Grady et al. 2007a). The wooden
shoe allows the distal phalanx to be realigned, has all the
mechanical components of other farriery systems
previously advocated for the treatment of chronic laminitis
yet may possess many additional advantages over
previous methods used. One major advantage may be its
ability to distribute weightbearing evenly over a specified
section of the foot due to its flat solid construction.
Other advantages are:
- Readily accessible materials
- Simplicity of construction
- Mechanics such as breakover and heel elevation can be fabricated into the shoe
- Nontraumatic application
- Bevelled perimeter of the shoe concentrates the load under the distal phalanx
- Solid base of shoe allows maximum recruitment of surface area in the palmar/plantar section of the foot to accept load
- Solid base combined with an appropriate Silastic material places even pressure and load across the palmar/plantar section of the foot
- Heel elevation, when necessary, can be applied in a uniform manner
- Easily altered according to the radiographic guidelines and structural requirements of individual foot conformation.
|Fig 1: A wooden shoe attached to a hoof model. Note the mechanics incorporated in the shoe - bevelled perimeter of the shoe for lateral/medial breakover, extended dorsal to palmar breakover and heel elevation.
|Fig 2: Radiograph of asymmetrical distal displacement of the distal phalanx on the medial side. Note that the red line drawn through the solar foramina is not parallel with the ground. Also note the disparity in the joint space from the lateral to the medial side (yellow arrow).
|Fig 3: a) The basic wooden shoe where the proximal piece is cut vertical and the thicker piece is cut on a 45° angle. Note the wedge pad attached to the wooden shoe for heel elevation if necessary. b) An expanded view of the construction of the wooden shoe.
|Fig 4: Ethyl vinyl acetate (EVA) glued to a 1⁄2 inch section of plywood and sanded into a dome shape. Note the leather pad on the foot surface of the wooden shoe, which is cut in the form of a 'W' to further unload the toe.
|Fig 5: Wooden shoe fabricated from a single piece of plywood. Note the recess in the foot surface of the shoe created with a router used to remove pressure from the dorsal aspect of the foot.
|Fig 6: A wooden shoe with the thinner section of plywood cut in the shape of a 'W' to distribute the weight under the palmar area of the foot and unload the dorsal toe. A wedge pad has also been cut in the shape of a 'W' and added to the shoe for heel elevation.
|Fig 7: a) Schematic illustration of a radiograph with dorsal capsular rotation showing the lines drawn parallel to the solar surface of the distal phalanx and the line drawn parallel to the dorsal surface of the distal phalanx (Illustration courtesy of Andrew Parks, University of Georgia, USA). b) The illustration applied to a radiograph with dorsal capsular rotation. Black line represents the widest part of the foot.
The lateral radiograph has always been considered the 'gold' standard for evaluating chronic laminitis but it does not allow identification of asymmetrical medial or lateral distal displacement (O'Grady et al. 2007a; Parks and O'Grady 2008). Therefore, the authors consider it crucial that a dorsopalmar (0° dorso palmar) radiographic projection must be included as part of the radiographic study for either acute or chronic laminitis. This allows the examiner to evaluate the distal phalanx in both a dorsalpalmar plane and a medial-lateral plane. High quality radiographs are required to visualise the osseous structures within the hoof capsule as well as the hoof capsule itself. Radiopaque markers can be used to determine the position of the distal phalanx in relation to surface landmarks.
The radiographic features of chronic laminitis are well documented (Redden 2003). The following observations from the lateral radiograph are important in assessing the severity, determining the prognosis and guiding treatment: the thickness of the dorsal hoof wall; the degree of dorsal capsular rotation; the angle of the solar surface of the distal phalanx relative to the ground; the distance between the dorsal limit of the solar margin of the distal phalanx and the ground; and the thickness of the sole.
The dorsopalmar radiograph is examined to determine
the position of the distal phalanx in the frontal plane.
Asymmetrical distal displacement of the distal phalanx on
either the lateral or medial side is present if an imaginary
line drawn across the articular surface of the distal
interphalangeal joint or between the solar foramina of the
distal phalanx is not parallel to the ground, the joint space is widened on the affected side and narrowed or
compressed on the opposite side, and the width of the
hoof wall appears thicker than normal on the affected
side. If the position of the coronary band is visible on the
radiograph, then the distance between the coronary
band and the palmar processes of the distal phalanx will
be greater on the affected than the unaffected side (Fig 2). The aetiology, diagnosis and management of
asymmetrical distal displacement of the distal phalanx will
be considered in a subsequent paper.
Goals of treatment for chronic laminitis
Trimming and shoeing has always been the 'mainstay' of treating chronic laminitis and is directed towards reducing/removing the adverse forces on the compromised lamellae. In considering hoof care in horses with chronic laminitis, there are 3 goals for therapy: to stabilise the distal phalanx within the hoof capsule; to
control pain; and to encourage new hoof growth to
assume the most normal relationship with the distal
phalanx as possible. Realignment of the distal phalanx to
create a better relationship of the solar surface of the
distal phalanx with the ground is used as the basis for
treating chronic laminitis (Redden 1997; Parks 2003;
O'Grady 2006). Applying the wooden shoe following this
procedure compliments the realignment of the distal
phalanx and appears to decrease the forces on the
lamellae due to the bevelled perimeter of the shoe. The
same shoeing principles are applied to the wooden shoes that are applied to other shoeing methods used in treating
chronic laminitis which are to recruit ground surface,
reposition the breakover palmarly and to provide heel
elevation as needed (Parks 2003; O'Grady 2006).
Construction of the shoe
The authors chose wood due to its accessibility, light
weight, the ease with which it can be constructed and
shaped (both before and after application) and its ability
to dissipate energy at impact while remaining rigid (Reid
1994; Steward 2003; O'Grady et al. 2007a). The wooden
shoe can be constructed in 2 ways. A wide web aluminium
shoe with a broad toe that is available in sizes 00 to 5 is
used as a template1. The basic shoe can be made from
2 pieces of plywood. One piece of plywood is 0.64–
0.95 cm thick and the second piece is 1.91 cm thick. Using
the aluminium shoe as a template, the thinner piece of
plywood is cut out with a vertical border while the thicker
piece is cut out with the border bevelled at a 45° angle
using an angle saw2. As a modification to the basic
pattern, the palmar or heel section of the wooden shoe
can be cut at a 15, 30 or 45° angle or left straight if desired.
The 2 pieces of plywood are glued together with the
thinner portion proximal and two 2.54 cm drywall screws or
wood screws are used to secure the 2 pieces together. A
wood rasp or belt sander is used to blend the cut angles
into a uniform slope (Figs 3a,b). Alternatively, the shoe can
also be fabricated from a single piece of 2.86 cm plywood
(purchased as sub-flooring plywood) using the same
technique as described above.
Recently, one author (M.L.S.) has occasionally
substituted ethyl vinyl acetate (EVA) for the thicker 1.91 cm
section of plywood and bevelled it in a similar manner. EVA
is an extremely elastic material that can be sintered to
form a porous material similar to rubber, yet with excellent
toughness. The compressibility and wearability of this
material allows 'selective' loading on the ground surface
of the shoe which appears to further decrease the stresses
on the lamellae and increase comfort (Fig 4). Additional
layers of plywood, rubber or EVA can be added to
increase the height of the wooden shoe when desired.
Shoe height is dictated by the conformation of the hoof
and the amount of displacement of the distal phalanx
present; i.e. the greater the rotation of the distal phalanx,
the more shoe height is necessary in order to achieve a
more palmar placement of breakover. If the sole is
prolapsed or the distal phalanx has penetrated the sole, a
recess can be created in the dorsal surface of the shoe by
cutting a half moon shape in the thinner piece of plywood
using a router under the prolapsed tissue or a hand grinder
can be used to create a trough in the shoe below the
area of the sole or bone that has prolapsed (Fig 5).
The same end can be achieved by cutting the thinner
piece of plywood or a leather pad in the shape of a 'W'
and then attaching it to the thicker section of plywood as
described above (Fig 6). If heel elevation is required, the heels can be raised accordingly by applying a wedge pad
to the hoof surface of the wooden shoe. The angle of the
wedge is usually 2–4° depending on the amount of heel
horn removed. The wedge pad is attached to the shoe
with 2.54 cm drywall screws or wood screws. An alternative
method to raise the heels is to cut the ground surface of
the wooden shoe itself at an angle to the hoof surface.
Application of the shoe
A generalised outline will be used to describe the
preparation of the foot and application of the wooden
shoe in horses with dorsal capsular rotation; bear in mind
each case of chronic laminitis must be treated on an
individual basis. The foot must be trimmed appropriately,
and the shoe sized and positioned in relation to the
underlying distal phalanx regardless of the conformation
of the hoof. Therefore, measurements must be made from
a lateral radiograph taken prior to shoeing as a guide. To
use the radiograph for guidance, a vertical line is drawn
from the center of rotation of the distal end of the second
phalanx to the ground. This line should correspond to the
widest part of the foot and can be used as a landmark on
the foot to begin the trim. Next a line is drawn parallel to
the solar border of the distal phalanx, starting 15 mm distal
to the palmar process of the distal phalanx and
continuing dorsally. The hoof wall to be removed in the
heel area can be determined from the mass below this
line. A second line is drawn 15 mm dorsal and parallel to
the dorsal surface of the distal phalanx; this line is used to
align the dorsal hoof wall with the parietal surface of the
distal phalanx (Fig 7a,b) (Parks 2003; Parks and O'Grady
2003; O'Grady 2006).
The initial step is to trim the heels and quarters of the wall
as well as the angle of the sole to coincide with the first line
drawn on the radiograph. Any exfoliating horn is removed
from the frog and the bars are trimmed on an angle to
widen the sulci. If possible, the ideal end product is to have
the hoof wall at the heels and the frog trimmed so that
they are on the same plane. This alone increases the
ground surface in the heel area and thus the ability to
accept load. If the foot can be trimmed to coincide with
the line drawn parallel to the solar surface of the distal
phalanx, the palmar aspect of the ground surface of the
foot will be on a different plane to the dorsal aspect of the
ground surface, which will often unload the dorsal section
of the foot. The dorsal hoof wall is trimmed to approximate
the line drawn parallel to the parietal surface of the distal
phalanx to create a more acceptable alignment
between the dorsal hoof wall and the parietal surface of
the distal phalanx.
Following the trim, the foot is placed on the ground and
the horse is observed for any additional discomfort.
Additionally, the horse is observed to see whether the heel
of the foot is touching the ground at rest, and whether the
horse lands markedly toe first as it moves in a straight line. If
any of these signs are present, heel elevation will be
necessary to compensate for the increase in tension in the
deep digital flexor tendon caused by lowering the heels of
the hoof capsule. Heel elevation is generally used if a
flexural deformity involving the distal interphalangeal joint
described as phalangeal rotation is noted radiographically
(O'Grady et al. 2007b). (Capsular rotation describes the
divergence of the dorsal hoof wall from the dorsal parietal
surface of the distal phalanx independent of the
relationship of the distal phalanx with the phalangeal axis
whereas phalangeal rotation describes rotation of the
dorsal surface of the distal phalanx palmarly/plantarly from
its normal orientation and relationship with the first and
second phalanges.) The trim should never violate normal
farrier practices, such as invading sensitive tissue.
Fitting the shoe
A line is drawn across the widest part of the trimmed foot.
Next, the foot surface of a wooden shoe is measured from
dorsal to palmar and then a line is drawn across the
middle of the shoe from lateral to medial. The correct size
of the shoe is determined by superimposing the line drawn
across the foot and the line drawn on the shoe on top of
each other; the appropriate size shoe will extend from the
line drawn across the foot to the end of the heel or 0–8 mm
palmar to the heel. Using a 1.98 mm drill, a guide hole is
drilled through the lateral and medial side of the hoof wall
at the widest part of the foot and 3.75 cm drywall screws
or wood screws are placed in each hole and screwed in
until just visible on the ground surface. To recruit the sole,
bars, frog and sulci for weightbearing, deformable
impression material3 is applied to the palmar/plantar
section of the foot of the foot.
|Fig 8: Wooden shoe being further secured to the foot using screws as struts and 5 cm fibreglass casting tape.
The shoe is now set in place on the ground surface of
the foot and attached using the 2 dry wall screws or wood
screws. The foot is placed on the ground and allowed to
bear weight in order for the impression material to
conform between the palmar section of the foot and the
shoe in the optimal form. Two or 3 more holes are drilled
through both sides of the hoof wall and the shoe is
secured in place using additional screws. These holes may
be predrilled from the solar surface of the foot if desired to
ensure accurate screw placement in the wall. If the mass
of the hoof wall is insufficient or if the quality of the hoof
wall is insufficient to hold the screws, screws can be
placed in the wooden shoe against the outer surface of
the hoof wall to act as struts and 5 cm casting tape4 is
used to form an attachment between the hoof wall,
screws and wooden shoe (Fig 8). With the foot on the
ground, a vertical line is drawn from the dorsal aspect of
the coronary band to the ground. The point where the line
meets the ground is where the breakover point of the
shoe should be positioned (Figs 9a,b,c). This point will
usually be just dorsal to the dorsal limit of the solar margin of the distal phalanx. Setting the breakover to this point in
the shoe is easily accomplished using a hoof rasp with the
foot being held in the farrier position. Deep digital
tenotomy has been the recommended treatment when
penetration of the distal phalanx through the sole has
occurred secondary to dorsal capsular rotation. One
author (S.E.O.) has observed that the wooden shoe has
provided an alternative and often better means to treat
this condition without surgery.
|Fig 9: a) Application of a wooden shoe with impression material. Black line is the widest part of the foot. Red line denotes the point of breakover on the ground surface of the shoe. b) A wooden shoe fabricated from a single piece of plywood with the same guidelines as shown in (a). c) Radiograph of foot following the application of a wooden shoe. Again, note that the black line is the widest part of the foot; the red line denotes the point of breakover on the ground surface of the shoe.
Prolapse of the sole or penetration of the distal phalanx
If the sole bulges distal to the level of the hoof wall or if the distal phalanx has penetrated the sole, the foot is trimmed to establish realignment, the wooden shoe is fitted to the trimmed foot and heel elevation is applied to the shoe to decrease the forces on the deep digital flexor tendon (Redden 1997). Before applying the shoe, the wooden shoe is placed against the solar surface of the foot and pressed against the sole or the exposed corium of the distal phalanx. The moisture of the tissue or a suitable dye applied to the corium will create an impression on the foot surface of the wooden shoe which can then be cut out using a router or a trough can be created with a grinder as illustrated in Figure 5. The shoe is now applied with screws and fibreglass tape, being sure that the impression material is concentrated palmar to the apex of the frog and not allowed to migrate dorsally. A window can be created in the fibreglass tape and the affected area can be packed with an appropriate antiseptic from the front of the shoe.
The authors have used the wooden shoe in their combined
practices for the past 5 years and found this technique
provides another very consistent farriery option when
treating a horse with chronic laminitis. Removing the stress
on the lamellae has always been difficult with traditional
shoes used to treat chronic laminitis as the shoe is placed
under the hoof wall concentrating the load on the
compromised lamellae. The solid plane of the wooden
shoe, combined with the impression material allows load
sharing across the ground surface of the foot especially in
the palmar section of the foot and appears to decrease
the load borne by the hoof wall. This concept of load
sharing is very helpful in horses with foot conformation that
has limited hoof mass in the palmar section of the foot.
Furthermore, cutting the perimeter of the wooden shoe at
a 45° angle around the circumference of the foot is
thought to decrease the lateral/medial torque on the
lamellae especially when the horse turns (Steward 2003;
O'Grady et al. 2007a). Therapeutic shoes used for treating
chronic laminitis are often deficient in providing sufficient
breakover and heel elevation due to the physical limits of
the particular shoe whereas increasing the height of the wooden shoe allows the desired mechanics to be
fabricated into the shoe. Shoe height enhances
mechanical advantages as it allows dorsal breakover,
lateral medial breakover and heel elevation to be
incorporated into the shoe in a uniform manner. Creating
a recess in the shoe under the distal phalanx in the toe
area relieves the load on dorsal aspect of the foot while
the weightbearing function is concentrated in the palmar
section of the shoe. When displacement of the distal
phalanx within the hoof capsule is severe, the wooden
shoe seems to be an excellent method to act as a
transient treatment to build sufficient hoof mass (wall and
sole) to where a more conventional shoe can be applied
or the horse can remain barefoot. It should be noted that
the heel elevation provided by the wooden shoe should
not be discontinued abruptly when this farriery method is
changed but rather decrease the heel elevation
gradually over the next few months.
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