Summary
The extensive nature of this topic warrants this review paper to
be divided into two parts: ‘Basic trimming in foals’ and
‘Therapeutic farriery in foals’. Management of the feet and limbs
during this juvenile period will often dictate the success of the
foal as a sales yearling or mature sound athlete. Overall hoof
care in the foal is often a joint venture between the veterinarian
and the farrier. The orthopaedic disorders discussed in this
paper that require input from the two professions are flexural
limb deformities (FLD) and angular limb deformities (ALD). The
concept of protecting the foot from the deleterious effects of
mal-loading created by many FLDs and ALDs is just as important
as using the symptomatology as an instrument to correct the
deformity. This paper presents a review of the current
information regarding the farriery for these two limb deformities
while dispelling some of the anecdotal methodology, such as
the use of toe extensions to treat flexural deformities, that
presently exists. Considering the deficiency of information in the
literature, segments of this text will be based on the author’s
extensive clinical practice, comprehensive clinical records
and comparisons of case outcomes.
Evaluation of the feet and limbs
The reader is referred to the section ‘Evaluating the foal’ in
Farriery for the foal: A review part 1: Basic trimming (O’Grady
2019). The importance of evaluating limb conformation, early
recognition of changes in flight pattern, limb placement and
foot loading patterns cannot be over emphasised. It is also
important to recognise changes in overall body condition or
accompanying developmental disorders as these may occur
prior to the onset of an angular limb deformity.
Flexural deformities
Flexural deformities have been traditionally referred to as
‘contracted tendons’. The primary defect is a shortening of the
musculotendinous unit rather than a shortening of just the tendon
portion, making ‘flexural deformity’ the preferred term (Adkins
2008; Hunt 2011; O’Grady 2012, 2014, 2017; Caldwell 2014, 2017).
This shortening produces a functional length that is less than
necessary for normal axial alignment of the digit; this results in
fixed flexion of the various joints of the distal limb especially the
distal interphalangeal joint (DIPJ) (O’Grady 2012, 2017).
Flexural deformities may be congenital or acquired. The
outcome and prognosis will vary with the severity and
subsequent treatment of the flexural deformity.
Congenital flexural deformities
Congenital flexural deformities are present at birth, may
involve one or a combination of joints (e.g. carpal,
metacarpophalangeal and distal interphalangeal joints) and
are characterised by abnormal flexion of a given joint or all
involved joints and the inability to extend the joint. Proposed
aetiologies of congenital flexural deformities include malpositioning of the fetus in utero, nutritional mismanagement
of the mare during gestation, teratogens in various forages
ingested by the mare and maternal exposure to influenza
virus; it is also possible that the deformities could be genetic
in origin (Hunt 2012; Caldwell 2014, 2017). Treatment of foals
with a congenital flexural deformity varies with the severity
and location of the deformity. It is not uncommon to see a
foal born with a flexural deformity (generally bilateral) that
involves a combination of joints in the forelimb such that the
foal will stand and walk on the toe of the hoof capsule, is
unable to place the heel on the ground and will assume a
‘ballerina’ stance with weight borne on the toes. A mild to
moderate flexural deformity in which the foal can readily
stand, nurse and ambulate is generally self-limiting and
resolves with conservative treatment. Brief intervals of exercise
for 1 h once or twice daily in a small paddock on firm footing
for the first few days of life may be all that is necessary for the
deformity to resolve. If the condition is unresponsive by the
third day post-partum, i.v. administration of oxytetracycline
(2–3 g), repeated every other day if necessary, is frequently
beneficial (Madison et al. 1994; O’Grady 2012; Caldwell
2017). Although this treatment is in widespread use, caution
must always be advised when administering this medication
to a neonate. A variety of bandaging techniques and splints
have been proposed, along with physical therapy to
potentially stretch the involved soft tissue structures, thus
possibly hastening recovery (Hunt 2011, 2012; Caldwell 2017).
In the author’s opinion, the traditional use of a toe extension
is not indicated, as applying a toe extension will generally
result in the neonate becoming ‘clumsy’, stumbling and
being unable to ambulate. The ‘lever arm’ principal of the
toe extension to stretch the tendon is unrealistic and does not
come without a price which is the likelihood of damage to
the hoof capsule (O’Grady 2017).
Foals with severe congenital flexural deformities of one
isolated joint or multiple joints present at birth that prevent
the foal from standing and ambulating, require therapeutic
intervention early in the clinical course of the case.
Treatments include aggressive physical manipulation and
stretching of the legs in conjunction with a variety of forms of
external coaptation aimed at fatiguing the muscular section
of the musculotendinous unit. Bandaging, transient static
splinting with PVC bracing or dynamic splinting with an
articulating brace, application of a flexible tension band
along the dorsal aspect of the limb and casting are
accepted techniques when properly applied and managed.
Application of a cast in a mildly extended position shortly
after birth will often improve a severe flexural deformity
enough to allow splinting or bandaging until the condition
fully resolves (Hunt 2011, 2012; Caldwell 2017).
The less common variation of a flexural deformity that
occurs in neonates is an isolated unilateral deformity of
the DIPJ and does not correct with manual extension
applied to the joint. The deformity occurs in all degrees
but is often severe and difficult to manage. Again, toe
extensions are not beneficial and typically cause the foal
to stumble. Although it is difficult to apply, useful external
coaptation to this area, articulating extension braces
attached to a foot cuff, application of a cast or
application of a flexible tension band with surgical tubing
will provide appropriate mechanics to this region (Hunt
2012; Caldwell 2017).
Acquired flexural deformities
Acquired flexural deformities (AFD) involving the DIPJ are
generally noted when the foal is between 2 and 4 months
old and generally involves the DIPJ initially. It is commonly a
unilateral condition but occasionally affects both forelimbs.
The aetiology of this deformity is unknown, but speculative
causes include genetic predisposition, improper nutrition (i.e.
overfeeding, excessive carbohydrate [energy] intake,
unbalanced minerals in the diet) and excessive exercise
(Adkins 2008; Hunt 2011; O’Grady 2012, 2017; Caldwell 2017).
A study looking at grazing patterns in a small number of foals
showed that foals with long legs and a short neck tended to
graze with the same limb protracted (van Heel et al. 2006).
Fifty percent of the foals in this study developed mis-matched
feet with a higher heel on the protracted limb leading the
researchers to feel there may be a possible correlation
between conformational traits and an acquired flexural
deformity. It is the author’s opinion that a large contributing
factor to this syndrome is contraction of the muscular portion
of the musculotendinous unit caused by a response to pain
(Kidd and Barr 2002; Caldwell 2017). The source of such pain
could be discomfort anywhere along the distal limb,
including physeal dysplasia or trauma causing foot pain in
foals exercising on hard ground. Rapid weight gain in the foal
may result in physeal overload and pain. Discomfort may
follow aggressive hoof trimming where excessive sole is
removed, thus rendering the immature structures within the
hoof capsule void of protection and prone to bruising
(O’Grady 2012, 2017). The foal then becomes unwilling to
bear full weight on the affected feet. Any discomfort or pain
in the foot or lower portion of the limb coupled with reduced
weight-bearing on the affected limb appears to initiate a
flexor withdrawal reflex; this causes the flexor muscles
proximal to the tendon to contract, leading to a shortened
musculotendinous unit and an altered position of the DIPJ.
This shortening of the musculotendinous unit shifts weightbearing to the dorsal section of the foot causing
inflammation of the lamellae in dorsal hoof wall, increased
load on the dorsal sole, bruising of the sole, hoof wall
separations, reduced hoof wall growth of the dorsal aspect
of the hoof wall and excessive hoof wall growth at the heel
to compensate for the shortening. As the flexural deformity
may be secondary to pain in these cases, it is essential that
possible sources of pain should be carefully identified and
localised by physical examination and, if necessary, by
regional analgesia and diagnostic imaging. The possibility of
a genetic component should also be considered for
acquired flexural deformities, as some mares consistently
produce foals that develop a flexural deformity in the same
limb as the dam or grand dam in which a similar deformity is
present (Hunt 2012; Caldwell 2014; O’Grady 2017). It also
appears that many individual foals have a propensity to
acquire a flexural deformity as a group of foals can be fed
the same ration, maintained in the same environment, have
the same farriery and exercise routine yet only the odd foal
will develop a flexural deformity (O’Grady unpublished data,
2012).
Mild acquired flexural deformities of the DIPJ
The initial clinical sign of a mild flexural deformity of the DIPJ
may only be abnormal wear of the hoof at the dorsal toe,
which is often discovered by the farrier during routine hoof
care. Closer or subsequent investigation may reveal that the
dorsal hoof wall angle is increased, a prominent coronary
band may be present but the heels of the hoof capsule are
still on the ground. However, after the heels of the hoof
capsule have been trimmed to an appropriate length, the
heels may no longer contact the ground. Most foals affected
to this degree may already have a mildly broken forward
hoof-pastern axis. Increased palpable digital pulse, heat in
the affected foot and signs of pain may be noted when
small hoof testers or even thumb pressure is applied to the
solar aspect of the toe dorsal to the frog are not uncommon
clinical findings. Hoof tester pain is generally due to lack of
sole thickness, trauma and excessive weight-bearing on the
dorsal toe. A recent method of classifying flexural deformities
of the DIPJ using a grading system (Grade 1–4) has been
proposed (Redden 2003). It is always beneficial to classify the
severity of the flexural deformity to devise an appropriate
treatment plan and monitor the response to a given therapy.
It also becomes a useful part of the foal’s record.
|
Fig 1: a) Grade 1 flexural deformity. b) After the foot is trimmed.
Note the bevel created under the toe.
|
|
Conservative treatment such as restricting exercise to
reduce further trauma to the foot is paramount. Correcting
the nutritional status of the foal (i.e. weaning the foal to
avoid possible excessive nutrition from the lactating mare
and/or decreasing carbohydrate intake), administering an
anti-inflammatory agent (NSAID) to relieve pain, administering
oxytetracycline to foals with acquired flexural deformities to
facilitate muscle relaxation and carefully trimming the palmar
section of the hoof are, in the author’s opinion, is a
reasonable starting point. The NSAIDs should be administered
short-term and judiciously in foals due to the potential side
effects, such as gastroduodenal irritation and nephrotoxicity.
For analgesia, the author will administer firocoxib (0.1 mg/kg
bwt q. 24 h) or flunixin meglumine (1.1 mg/kg bwt q. 24 h)
combined with a gastric protectant. Hoof trimming is
directed towards improving the hoof angle by lightly trimming
the heels from the middle of the foot palmarly until the hoof
wall at the heels and the frog are on the same plane. Over
trimming of the heels should be discouraged as this will
invariably cause the heels to lift off the ground which can be
noted on firm footing. The bars can be thinned in this
instance as an attempt to spread and possibly improve heel
expansion. Additionally, the heels of the hoof capsule
adjacent to the frog sulci may also be rasped to a 45° angle
in an attempt to promote spreading. If the sole thickness is
sufficient in the dorsal foot (does not deform with hoof testers
or thumb pressure), breakover is moved palmarly by creating
a mild bevel with a rasp, which begins just dorsal to the apex
of the frog and extends to the perimeter of the dorsal aspect
of the hoof wall (Fig 1). If improvement is noted, this trimming
regimen is continued and optimally performed at 2-week
intervals. If the toe is constantly being bruised or undergoing
abscessation, an acrylic or urethane composite (Equilox® or
Vettec®) can be applied to the dorsal aspect of the sole and
the distal dorsal aspect of the hoof wall to form a protective
toe ‘cap’. The acrylic composite-impregnated fibreglass
combination or urethane composite used to form the toe
cap will cover the solar surface with a thin layer of composite
from the margin of the dorsal hoof wall to the apex of the
frog, protecting that area from further damage and creating
or exacerbating lameness. Caution is advised when a
composite cap is applied as the sole-wall junction may be
stretched or have separations/fissures present which make it
|
Fig 2: Grade 3 flexural deformity.
|
|
|
Fig 3: Chronic grade 3 flexural deformity in a 3-month-old foal
that has acquired a tubular shape of the hoof capsule with the
coronet becoming horizontal.
|
|
|
Fig 4: Photograph of toe extension shows the leverage on the
hoof capsule and the point on the dorsal wall where the force is
exerted (red arrow). Note the heel off the ground. Illustration of
foot shows ground reaction force (GRF) is moving dorsally in the
toe as the muscle tendon unit shortens and tension increases in
the DDFT (Image courtesy of Andrew Parks).
|
|
susceptible to infection. Any separations should be explored
and then packed with clay or other suitable material prior to
the composite being applied. A bevel toward the toe can
be created in the composite with a rasp or motorised burr
(Dremel® tool) to facilitate breakover. If there is adequate
integrity of the dorsal section of the hoof wall, the author
believes the application of a toe extension to be
unwarranted and contraindicated (O’Grady 2017).
The above treatment for a mild flexural deformity is often
temporary as many foals will progress to a more severe
deformity and thus the farriery appears to work best when
initiated at the first sign of abnormal foot conformation
before a marked flexural deformity is apparent. Whenever
possible, the elimination of any possible or suspected inciting
causes should be pursued.The farriery for a mild flexural
deformity should always be combined with restricted
exercise. If the affected foot continues to improve or does
not regress, conservative treatment is continued. If a mild
flexural deformity progresses in severity to the stage where a
marked flexural deformity is present, the foal becomes a
surgical candidate.
Severe acquired flexural deformities of the DIPJ
A mild acquired flexural deformity may progress in severity
despite conservative treatment or a severe acquired flexural
deformity may be acute in onset. A severe acquired flexural
deformity is characterised by a foot with a hoof angle
greater than 80°, a prominent fullness at the coronary band,
a broken forward hoof-pastern axis, disparity in hoof wall
growth distal to the coronet at the heel relative to growth at
the toe and heels that fail to contact the ground (Fig 2). If
the flexural deformity is allowed to persist, the foot eventually
assumes a boxy, tubular shape due to the overgrowth of the
heels to accommodate the lack of ground contact; heel
length will approach the length of the toe (Fig 3). Increased
stress on the hoof wall at the toe will eventually cause a
concavity along the dorsal surface of the hoof wall. Stress
exerted on the sole-wall junction in the toe area will cause it
to widen, allowing separations to occur.
Farriers have traditionally applied toe extensions to create
a lever arm using a shoe or a composite to force the heel to
the ground, but this will only exacerbate damage to the
dorsal section of the foot, promote hoof wall separation and
delay breakover (Hunt 2012; O’Grady 2017). As it is important
to consider the use of a toe extension in biomechanical
terms and to understand the effect of this leverage, it is
necessary to briefly consider the moments about the distal
interphalangeal joint. The moments about the DIPJ are the
flexor moment and the extensor moment (a moment is equal
to force x distance). At rest, the extensor moment is the
product of the weight born by the limb (a force) and the
horizontal distance from the point at which the ground
reaction force GRF acts on the foot (centre of pressure CoP)
and the centre of rotation of the distal interphalangeal joint
(a distance). The flexor moment opposes the extensor
moment and is the product of the force (tension) in the
tendon and the shortest distance of the deep digital flexor
tendon (DDFT) from the centre of rotation. Normally these
two moments are balanced at rest, the GRF is dorsal to the
centre of rotation of the joint and the heels are on the
ground. In foals with a flexural deformity of the DIPJ, the
tension in the tendon increases (as a result of the shortened
musculotendinous unit), which increases not only the flexor
moment but the opposing extensor movement which moves
the CoP dorsally in the toe. At the point where the tension in
the tendon increases such that the CoP is at the dorsal limit
of the toe, any further increase in tendon tension cannot be
balanced by movement of the CoP because it is already at
the perimeter of the toe and can't move further dorsally,
therefore, the heels lift off the ground (Eliashar 2012). Adding
an extension to the toe of the foot allows the centre of
pressure to move further dorsally in the toe in an attempt to
counteract the tension in the tendon and force the heels to
the ground. The ability of the toe extension to do this is
dependent on the integrity of the tissues (hoof wall,
lamellae), however, the tissues are not generally strong
enough to withstand the additional stress and separation
occurs within the dorsal hoof wall. Therefore, placing an
extension or leverage on the dorsal hoof wall to counteract
the forces in the shortened deep digital flexor muscle tendon
unit is unrealistic and, in the author’s opinion, contraindicated
(Fig 4). Furthermore, extensions may contribute to lameness
due to excessive stresses on the DDFT when the foal puts full
weight on its foot and at the initiation of breakover.
|
Fig 5: Radiograph shows a marked flexural deformity involving
the distal interphalangeal joint (red circle).
|
|
Radiographs should be used to assess changes in the joint
and the integrity of the distal phalanx. The author will
administer mild sedation (xylazine [0.33 mg/kg bwt, i.v.]
combined with butorphanol [0.022–0.066 mg/kg bwt i.v.]) and
place each of the foal’s feet on separate wooden blocks of
equal height, which allows normal or equal loading of both
forefeet. The forelimbs are positioned such that the third
metacarpal bone is perpendicular to the ground. Lateral-medial weight-bearing images of both forefeet should be
acquired. The degree of flexion of the DIPJ, the angle of the
dorsal hoof wall and abnormalities at the margin of the distal
phalanx should be assessed (Fig 5). When a marked flexural
deformity is noted during radiographic examination of the
feet, conservative treatment and hoof trimming alone are
generally unsuccessful in resolving the foot conformation.
Elevating the heels has been advocated to reduce tension in
the DDFT and to promote weight-bearing on the palmar
section of the hoof. However, although elevating the heels
will load the palmar section of the foot, improve the hoofpastern axis and make the foal more comfortable initially, the
author has not been able to subsequently lower the heel or
remove the wedge and establish an acceptable hoof angle
with the heel on the ground. Once a marked flexural
deformity of the DIPJ with the heels of the hoof capsule lifted
off the ground or a distorted hoof capsule characterised by a
foot with a steep hoof angle, a prominent fullness at the
coronet, a broken forward hoof-pastern axis, a disparity in the
length of the heel relative to the toe of the hoof and some
degree of concavity in the toe is apparent; the author
recommends transection of the accessory ligament of the
DDFT combined with the appropriate farriery.
The farriery is generally performed prior to the surgery
either before or while the foal is anaesthetised to prevent
manipulating the limb and handling the surgical site following
the procedure. A toe extension is not used; rather an acrylic
composite is applied to the solar region of the toe to create
a reverse wedge (Stone and Merritt 2009; Hunt 2012; O’Grady
2012, 2017). The wedge affords protection for the toe region
and appears to redistribute the load to the palmar aspect of
the foot, thus mildly increasing the stresses on the DDFT, and
appears to restore the concavity to the sole. The heels are
lowered with a rasp from the point of the frog palmarly, until
the sole adjoining the hoof wall (sole plane) at the heels
becomes solid. This will generally place the hoof wall and the
frog on the same horizontal plane. Any concavity or bending
in the dorsal aspect of the hoof wall is removed with a rasp in
order to redirect the forces directly under the coronet at
breakover. The ground surface of the foot dorsal to the frog
and the perimeter of the dorsal hoof wall are sanded and
prepared for the composite wedge using a rasp or motorised
burr (Dremel® tool). Deep separations in the sole-wall junction
at the toe are explored and filled with clay, if necessary, to
prevent tracts for infection beneath the composite. Foals
undergoing this procedure are usually between 3 and
5 months old; therefore, due to their size and weight,
reinforcing the composite with fibreglass is necessary to
prevent excessive wear.
|
Fig 6: Reverse wedge created from a composite. An aluminium
plate can be imbedded in the composite to prevent wear.
|
|
A small section of fibreglass is
separated into strands and mixed with the composite. The
acrylic composite is applied to the solar surface of the foot
beginning at the apex of the frog and extending to the
perimeter of the hoof wall where a thin lip is formed around
the perimeter of the dorsal hoof wall at the toe. The
composite is moulded into a wedge starting at 0° at the
apex of the frog and extending to 2° to 3° at the toe (Stone
and Merritt 2009; O’Grady 2012, 2017)
(Fig 6). If desired, a
piece of 1/8-inch aluminium plate can be cut out in the
shape of the dorsal aspect of the sole. Multiple holes are
drilled in the plate, and it is gently placed into the composite.
The aluminium is pushed down so that the composite
material extrudes through the holes, and the aluminium plate
is then covered with additional composite. This additional
reinforcement allows the older foals to be walked daily or
turned out in a small paddock without the foal wearing
through the composite. The foal is placed under general
anaesthesia, and the surgery is performed in a routine
manner that is well described in the veterinary literature.
The surgical aftercare is at the discretion of the attending
clinician. Oxytetracycline may be used with the surgery
during the perioperative period to facilitate relaxation of
other soft tissue structures secondarily involved (joint capsule,
collateral ligaments) (Hunt 2012). Controlled exercise in the
form of daily walking or turn out in a small paddock with firm
footing such as a round pen is essential. There is the potential
for pain with the initiation of exercise due to the shortening of
soft tissue structures such as the joint capsule and suspensory
ligaments to the navicular bone, requiring close monitoring of
the foal, and exercise should be increased sequentially. The
foal is trimmed at roughly 2-week intervals, based on the
amount of hoof growth at the heels with the objective of
establishing normal hoof capsule conformation. The
composite wedge is removed one-month post-surgery. At
subsequent trimmings, the heels are trimmed as necessary
from the middle of the foot palmarly such that the frog and
hoof wall are on the same plane and hoof wall at the toe is
trimmed from the dorsal aspect of the hoof wall until the
desired conformation is attained. No sole dorsal to the frog is
removed. This type of trim promotes sole growth and creates
approximate proportions on either side of the COR. When the
desired foot conformation is reached, the foot is trimmed in a
routine manner monthly. It is important to emphasise that
when the hoof capsule returns to an acceptable
conformation, only that portion of the sole that is shedding
should be removed. This avoids causing discomfort in the
dorsal solar section of the foot that can result in the foal
redeveloping, to some degree, the original flexural deformity.
The higher-grade clubfoot appears to have a tendency to
revert back to the original deformity if not managed properly.
Angular limb deformities
Angular limb deformities (ALD) are common in foals and
require early recognition and treatment (Greet 2000; Hunt
2000; Greet and Curtis 2003; Auer 2006; Witte and Hunt 2009;
Garcia-Lopez 2017; O’Grady 2017). This subject receives
tremendous attention in any discussion of foal conformation
and it refers to a lateral or medial deviation in axial alignment
of the limbs when the animal is viewed from the frontal
plane. It is understood that a certain amount of deviation
can be normal in young foals and does not require any
special farriery or surgical intervention (Hunt 1998, 2000; Auer
2012; O’Grady 2017). Objective data is lacking regarding the
dynamics involved in the development of acquired angular
limb deformities, however, it is recognised that many foals
change axial alignment during various stages of their
development. Serial evaluation and treatment of limb
deviations is an integral component of management on most
breeding operations.
Angular limb deformities may occur anytime during the
animal’s life but are most commonly treated from birth
through the yearling growth period. The primary lesion
appears to be an imbalance of physeal growth; for assorted
reasons, growth proceeds faster on one side of the physis vs.
the other. Although this is described as a discrepancy of limb
length of the medial vs.
|
Fig 7: Carpal valgus. Note the limb below the carpus deviates
away from the midline (red line).
|
|
lateral side from an imbalance of
physeal growth; another discrepancy in loading the limb with
lack of soft tissue support may also create an ‘apparent’
ALD. Angular limb deformities can be further classified into
two categories; valgus deformities occur when the deviation
occurs lateral to the axis of the limb distal to the affected
joint (away from the midline) and varus deformities occur
when the deviation is medial to the axis of the limb distal to
the affected joint (toward the midline)
(Fig 7). The most
common location of valgus angular limb deformities is the
carpus and tarsus while varus deformities are most often seen
at the fetlock and to a lesser extent at the carpus.
Limb alignment of young foals should be observed
standing and walking without restriction on the head and
neck (not leaning) toward and away from the examiner.
Overall body development and maturity should be noted. It
is important to take note of foot placement especially when
working with distal limb deviations. This will determine the
necessity for corrective measures on the feet such as
trimming or placement of a composite extension on the hoof
capsule to alter the forces on the physis and change the
rotation of the limb on contact with the ground. This practice
is especially beneficial with a fetlock varus deviation with
inward rotational deformities in foals 2–4 weeks of age in
which there is a limited time frame for correction.
Carpal/tarsal valgus
It is apparent that a mild carpal valgus of 2–5 degrees offers
the newborn foal a comfortable stance while nursing and
eating off the ground and is considered acceptable. If the
deviation exceeds 5–8 degrees then it becomes a concern
and should be monitored (Hunt 1998, 2000; Auer 2012). A few
days of stall confinement on firm bedding or limited exercise
in a small paddock (2–3 times a day) is a rewarding, costeffective treatment for early carpal or tarsal valgus (GarciaLopez and Parente 2011).
|
Fig 8: Two-month-old foal trimmed to show the proportionality of
the foot on either side of a line drawn across the widest part of the
foot. Note the hoof wall at the heels and the frog trimmed to the
same plane.
|
|
It may be helpful to digress and briefly mention routine
hoof care before discussing treatment of angular limb
deformities. The technique for using farrier tools when
trimming foals was discussed under the trim in Part 1 of this
review. The veterinary and farriery literature abounds with
various trimming methods that are thought to affect the
various limb conformations; however, none of these methods
have been substantiated or documented to be efficacious.
The author trims the heels such that the heels of the hoof wall
and the frog are on the same plane, visualises a line across
the middle of the foot (located just dorsal to the COR) and
then reduces the toe to make the foot proportional on either
side of the line across the widest part of the foot. When the
trim is complete, the solar surface of the foot will be level
rather than having the lateral to medial orientation of the
foot changed by rasping one side of the foot more than the
other (Fig 8). Farriery texts describe trimming a foal lower on
the outside of the foot when the foot turns out and trimming
the foal on the inside of the foot when the foot turns in;
however, remembering that a toe-out or toe-in stance
originates from the limb, this practice will do nothing more
than place excessive stress on one side of the hoof capsule
If the angular limb deformity is greater than 5–8 degrees or
shows no improvement in the first few days of life, radiographs
should be part of the physical examination of a foal with ALD
(Garcia-Lopez and Parente 2011; Garcia-Lopez 2017).
Occasionally, osseous abnormalities such as hypoplastic
carpal/tarsal bones will preclude correction of the problem
without splints or a cast. Radiographs will also reveal the site
and degree of deviation which will allow comparison later.
Carpal valgus deformities of less than 10 degrees are
generally handled successively with conservative treatment
(Garcia-Lopez and Parente 2011; Garcia-Lopez 2017).
Conservative therapy for the management of many mild
to moderate congenital angular limb deformities may be
successful in the newborn foal. Restricted exercise would be
either strict stall confinement or brief periods of turnout (1 h
two times daily) in a small area with firm footing. This allows
the physis to be stimulated but prevents stress, fatigue and
compression on the overloaded side of the growth plate
from excessive exercise. If the carpus can be corrected by
applying pressure with one hand on the inside of the carpus
and counter pressure with the other hand applied to the
outside of the fetlock, some form of coaptation such as
support tape, splints, dynamic splints or tube casts may be
helpful. The author uses a splint made from polyvinylchloride
(PVC) pipe, cut in half and fitted from the elbow to below
the fetlock applied for a few hours 1–2 times daily. It is
labour intensive, but the splints must be removed and
replaced periodically to prevent laxity. A full-length thick
cotton bandage is applied to the entire limb, and then the
PVC pipe is placed on the outside of the limb and secured
to the bandage with elastic tape. This will distract the
carpus laterally and load the limb more proportionally. The
splint is often the most cost-effective treatment available
but must be applied with caution, paying strict attention to
the details of application. Meticulous attention to applying
the splint is essential to prevent focal pressure and the
propensity of the foal to develop decubital ulcers. As the
foal improves, brief periods of turnout in a small area with
firm footing can be considered.
|
Fig 9: Grade 3 carpal valgus in a 2-month-old foal.
|
|
Acquired carpal/tarsal valgus deformities can be graded
from one to four according to severity (Fig 9). Mild to
moderate carpal valgus will generally respond to restricted
exercise and the use of a composite extension applied to the
medial side of the foot while the more severe cases require
surgical intervention combined with farriery (Hunt 1998, 2000;
Greet 2000; Auer 2006; Witte and Hunt 2009; Garcia-Lopez
2017; O’Grady 2017). Various clinicians have described
trimming the lateral side of the foot aggressively when there is
a valgus deformity in an attempt to increase the ground
surface on this side of the foot (Greet and Curtis 2003).
However, it is this authors’ opinion that the foal does not grow
sufficient horn at this age to make an appreciable difference
and changing the medial to lateral orientation of the foot
may have detrimental effects on the immature hoof capsule
as well as the physis. Using some form of extension to
increase the ground surface of the foot and change the
forces on the physis seems to be more beneficial (Cheramie
and O’Grady 2003; Greet and Curtis 2003; O’Grady 2017).
Periosteal elevation is a controversial surgery that is
routinely performed on foals with mild to moderate angular
limb deformities (Garcia-Lopez 2017). However, the author
has not referred a foal for this surgery in 20 years as the
author saw no difference when compared with foals that
had controlled exercise (brief turnout in a small paddock with
firm footing) and the application of a hoof extension
(O’Grady unpublished data, 2014). If stall confinement is used
initially, the mare and foal should be bedded on firm footing
(such as a thin layer of sawdust) for the foot extensions to be
effective. Initially, the author prefers using some form of
extension to increase the ground surface area of the foot on
a given side and change the forces on the affected joint.
Some type of composite applied to the hoof wall is preferred
rather than a cuffed shoe that is attached with glue as this
type of shoe appears to restrict movement of the hoof
capsule and contracts the foot especially the heels. As noted
previously in Footcare in foals: A review part 1, the author will
not apply a composite to a foal’s foot before 3 weeks of age
because of the potential detrimental effects of the excessive
heat
For carpal valgus, the composite extension is placed on
the medial side of the hoof and toward the heels which
appears to redirect the forces on the physis on the
overloaded side of the limb by moving the axis of weight
bearing towards the centre of the limb (Fig 10).
|
Fig 10: Urethane extension placed on medial side of hoof on foal in
Figure 9.
|
|
The extension
also appears to promote centreline breakover. The extension
is made from an acrylic composite mixed with fibreglass
strands or a urethane composite applied directly to the foot
and shaped to the desired width. Properly applied for
maximum results, the extension should begin at the contact
point of the heel and feather up most of the length of the
wall. It should not extend dorsally beyond the junction of the
quarter and toe to be of any benefit. Also, it should not be
built up on the sole but only tapered along the sole toward
the frog. The extension should be no wider than a vertical line
drawn from the coronet to the ground. If the extension is too
wide, it applies leverage on the attached side that will
invariably distort the hoof capsule. The extension should be
removed every 2–3 weeks for 1–2 days to allow the hoof wall
to dry out and not break up. Also, with chronic use, there
may be a restriction of hoof wall growth which may
contribute to long-term distortion of the wall. Strict controlled
exercise as described above is essential for this conservative
approach to be successful. In severe cases of carpal valgus
or cases that have not responded to conservative therapy,
surgery such as a transphyseal screw or staple or a wire
transphyseal bridge placed across the distal radial physis may
be necessary (Garcia-Lopez 2017; McCarrel 2017). The author
likes to combine a medial extension with the surgery,
however, it may affect the clinician’s ability to assess the limb
to accurately determine the time for implant removal (A.
Parks, personal communication, 2012). In many cases, a
surgical procedure may be performed too early before
conservative therapy has allowed sufficient time to correct
the problem. It appears that valgus angular limb deformities
involving the carpus will respond to transphyseal bridge
surgery up to 14 months of age, resulting in full correction
(Garcia-Lopez 2017; McCarrel 2017). Obviously, if the valgus
deformity renders the carpus unstable, then surgery will be
required sooner.
Fetlock varus
Varus deformities involving the fetlock are common in either
the front or hindlimb of newborn foals (Fig 11).
|
Fig 11: Left forelimb fetlock varus in a 2-week-old foal. Note the
varus deformity combined with the toe-in conformation of the
digit.
|
|
|
Fig 12: Impression material is formed to match the concavity of
the sole and hold it in place. Impression material can be trimmed
to the desired width of the lateral extension (red arrow).
|
|
This deformity
can be congenital or acquired within the first week of life.
Fetlock varus is often confused with a foal that has a toe-in
conformation. The digit will deviate axially (toward the midline)
relative to the fetlock with fetlock varus; a foal with a toe-in
conformation will have a rotational deformity at or above the
fetlock but the digit will follow the axial alignment of the limb.
However, both conditions may occur concurrently. A fetlock
varus deformity requires early detection and treatment since
functional closure of the distal physis of the third metacarpal/
metatarsal bone is approximately 8 weeks of age. Foals with
fetlock varus should have their exercise restricted and will
generally respond to an extension applied to the lateral side of
the foot to change the forces on the lateral side of the physis.
The window of opportunity for treatment is small and the
extension should be applied at 1–3 weeks of age. As stated
previously, the author is reluctant to apply a composite to a
foal’s foot before 3 weeks of age. Alternatively, the author
uses a firm impression material (Equilox Pink®), moulds it to the
solar surface of the foal’s foot forming an extension on the
lateral side
(Fig 12). The impression material is moulded into the
concavity of the sole and the sulci of the frog which holds it in
place; it is then secured by covering the foot with kling gauze
and then taping the extension in place with 2-inch elastic
tape. Between 3–6 weeks of age, a composite extension can
be applied to the lateral wall as described above; however
the results are better if correction is started shortly after birth. In
severe cases, surgical intervention will be necessary combined
with a lateral extension. If the foal is presented for treatment
after 6 weeks of age, treatment becomes difficult and surgery
will be necessary for correction with the overall treatment
being less effective and not as cosmetic. Many fetlock varus
deformities are not evident until 8–10 weeks or even later and
obviously not addressed until that time. With the exception of
a severe fetlock varus deformity; it may be ill-advised to place
a transphyseal screw at less than 6 weeks of age because of
rapid correction at this early age which necessitates early
removal of the implant (R. Hunt, personal communication,
2018).
Carpal varus deviations are also recognised in young foals
and weanlings. Foals that develop carpal varus from birth to
1–2 months of age often have an ‘over at the knee’
appearance and buckle forward when standing. These foals
typically worsen with exercise and improve with rest. Dietary
control is important as is the judicious use of analgesics and
controlled exercise. Lateral extensions placed on the foot may
be useful but surgical intervention may be necessary if the
varus deformity is severe. Weanlings that develop carpal varus
are typically offset at the carpus, sometimes pigeon toed and
often have accompanying physeal dysplasia. If the physeal
dysplasia is kept under control; the deviation will often resolve.
If the condition fails to respond, surgery such as transphyseal
bridging or placement of a transphyseal screw in the physis of
the distal lateral radius may be necessary. In general, valgus
deviations are far easier to manage and are more prone to
spontaneously correct and appear much more forgiving from
a soundness standpoint than varus deviations.
Conclusions
The concept of protecting the foot from the deleterious
effects of mal-loading created by many FLDs and ALDs is just
as important as using the symptomatology as an instrument
to correct the deformity. Flexural and angular limb deformities
are often controversial and have a multitude of purported
treatments; it is therefore essential that appropriate
communication occur among the responsible parties to
avoid any misunderstanding and unnecessary or job
threatening miscommunications. Management of limb
deformities in foals, irrespective of the type, severity or origin,
are best managed through a coordinated effort between
the owner, farm manager, farrier and veterinarian. When
treating valgus and varus limb deformities especially fetlock
varus, prompt early recognition and treatment is best for
consistent correction. Most veterinarians are not able to
perform the farriery required to address foot and limb issues in
foals, so their reliance on a farrier becomes obvious. A
veterinarian not well versed in farriery should familiarise
themselves with good basic farriery and have a working
knowledge of this discipline. An avenue of communication
between the professions is not only necessary but mandatory.
Hoof care in the first few months of life is serious business and
should never be taken lightly. Appropriate farriery combined
with medical/surgical input from the veterinarian is essential
when confronted with orthopaedic disorders related to the
limbs. Farriery plays a vital role in both the development of
the hoof and the conformation of the limb. A planned foot
care programme is time consuming whereas assembly-line
trimming is quick and easy, but the former thoughtful
approach is much more rewarding with a better outcome
ACKNOWLEDGMENTS
Conflict of Interest
No conflicts of interest have been declared.
Ethical animal researchNot applicable.
Declaration of EthicsNot applicable.
Source of fundingNone.
REFERENCES
-
Adkins, A. (2008) Flexural limb deformity. Proc. Br. Equine Vet. Assoc.
Congress 47, 41-42.
-
Auer, J.A. (2006) Angular limb deformities. In: Equine Surgery, 3rd edn.,
Eds: J.A. Auer and J.A. Stick. WB Saunders, St Louis. pp 1130-1149.
-
Auer, J.A. (2012) Angular limb deformities. In: Equine Surgery, 4th edn.,
Eds: J.A. Auer and J.A. Stick. Elsevier, St Louis. pp 1201-1221.
-
Caldwell, J.D. (2014) Investigation for Genetic Determinants of
Conginital Flexion Contractures and contracted Foal Syndrome in
Neonatal Thoroughbred Foals. PhD Dissertation, Texas A & M
University.
-
Caldwell, F.J. (2017) Flexural deformities of the distal interphalangeal
joint. Vet. Clin. North Am. Equine Pract. 33, 315-330.
-
Cheramie, H.S. and O’Grady, S.E. (2003) Hoof repair and glue-on shoe
technology. Vet. Clin. North Am. Equine Pract. 19, 519-530.
-
Eliashar, E. (2012) The biomechanics of the equine foot as it pertains
to farriery. Vet. Clin. North Am. Equine Pract. 28, 283-291.
-
Garcia-Lopez, J.M. (2017) Angular limb deformities. Vet. Clin. North
Am. Equine Pract. 33, 343-351.
-
Garcia-Lopez, J.M. and Parente, E.J.(2011) Angular limb deformities.
In: Diagnosis and Management Of Lameness In The Horse, 2nd
edn., Eds: M.W. Ross and S.J. Dyson. Elsevier, St. Louis. pp 640-
645.
-
Greet, T.R.C. (2000) Managing flexural and angular limb deformities:
the newmarket perspective. Proc. Am. Assoc. Equine Pract. 46,
130-136.
-
Greet, T.R.C. and Curtis, S.J. (2003) Foot management in the foal and
weanling. Vet. Clin. North Am. Equine Pract. 19, 501-517.
-
van Heel, M.C., Kroekenstoel, A.M., van Dierendonck, M.C., van
Weeren, P.R. and Back, W. (2006) Uneven feet in a foal may
develop as a consequence of lateral grazing behavior induced by
conformational traits. Equine Vet. J. 38, 646-651.
-
Hunt, R.J. (1998) Angular limb deformities. In: Current Techniques in
Equine Surgery and Lameness, 2nd edn., Eds: N.A. White and J.N.
Moore. Saunders, Philadelphia. pp 323-326.
-
Hunt, R.J. (2000) Management of angular limb deformities. Proc. Am.
Assoc. Equine Pract. 46, 128-129.
-
Hunt, R.J. (2011) Flexural limb deformities in foals. In: Diagnosis and
Management of Lameness in the Horse, 2nd edn., Eds: M.W. Ross
and S.J. Dyson. WB Saunders, Philadelphia. pp 645-649.
-
Hunt, R.J. (2012) Management of clubfoot in horses: foals to adult.
Proc. Am. Assoc. Equine Pract. 58, 157-163.
-
Kidd, J.A. and Barr, A.R.S. (2002) Flexural deformities in foals. Equine
Vet. Educ. 14, 311-321.
-
Madison, J.B., Garber, J.L., Rice, B., Stumf, A.J., Zimmer, A.E. and Ott,
E.A. (1994) Effects of oxytetracycline on metacarpophalangeal
and distal interphalangeal joint angles in new born foals. J. Am.
Vet. Med. Assoc. 204, 240-249.
-
McCarrel, T.M. (2017) Angular limb deformities. Vet. Clin. North Amer.
Equine Pract. 33, 353-366.
-
O’Grady, S.E. (2012) Flexural deformities of the distal interphalangeal
joint (clubfeet): a review. Equine Vet. Educ. 24, 260-268.
-
O’Grady, S.E. (2014) How to manage the club foot-birth to maturity.
Proc. Am. Assoc. Equine Pract. 60, 60-72.
-
O’Grady, S.E. (2017) Routine trimming and therapeutic farriery in foals.
Vet. Clin. North Am. Equine Pract. 33, 267-288.
-
O’Grady, S.E. (2019) Farriery for the foal: A review part 1: Basic
trimming. Equine Vet. Educ. Epub ahead of print; https://doi.org/
10.1111/eve.13072
-
Redden, R.F. (2003) Hoof capsule distortion: understanding the
mechanisms as a basis for rational management. Vet. Clin. North
Am. Equine Pract. 19, 443-463.
-
Stone, W.C. and Merritt, K. (2009) A review of the etiology, treatment
and a new approach to club feet. Proc. Am. Assoc. Equine
Practit. - Focus on the Equine Foot, pp 181-190
-
Witte, S. and Hunt, R. (2009) A review of angular limb deformities.
Equine Vet. Educ. 21, 378-387.