The Value of Quality Foot Radiographs and TheirImpact on Practical Farriery
Reprinted with permission from the American Association of Equine Practitioners.
Originally printed in the 2012 AAEP Convention proceedings
Randy B. Eggleston, DVM, Diplomate ACVS
Radiographic evaluation of the horse's foot for the
purpose of consultation with the farrier is becoming
more popular but is still an underutilized use of
radiographic imaging. In the absence of lameness,
detailed radiographic evaluation of the horse's foot
is very useful in preplanning and management of
trimming and shoeing of a horse's foot and in the
prevention of lameness. A horse's exhibiting poor
foot conformation, imbalance, or abnormal patterns
of growth can be clues to impending foot disease and
lameness. Radiographic evaluation of a horse's
foot gives tremendous insight into the relationship
between the structures within the foot and between
the foot and distal limb.
Digital photography has also been shown to be
useful and accurate in the assessment of the horse's
foot.1 However, the relationship of the distal phalanx
with the hoof capsule cannot be appreciated
with photography alone.
The quality of information obtained from a radiographic
study depends solely on the quality of the
radiographs ("garbage in, garbage out"). Producing
quality radiographs is dependent on the use of quality
equipment, developing a proficiency at operating
that equipment, and maintaining consistency when
performing radiographic studies. A systematic approach
should be taken when planning a radiographic
study of the foot; the "point-and-shoot"
approach is not always the best approach. Taking
multiple standard views, although not always necessary,
is important to avoid missing a diagnosis.
Additional projections may be required to further
investigate initial findings or confirm a diagnosis.
There are a number of preplanning questions that
must be asked before performing foot radiographs:
(1) What is the purpose of the study: investigation
of lameness or consultation with the farrier? (2)
What do I expect to gain from the study: source of
lameness or information useful in managing the
foot? (3) What information do I need to obtain from
the study: relationship of the hoof capsule and the
distal phalanx? The answers to these questions
will guide in planning the study with regard to the
appropriate views to be taken, the appropriate technique,
and the appropriate positioning of the foot
and centering of the x-ray beam.
Taking the time to examine the foot and prepare it
properly will avoid the need, risk, and expense of
repeating images and will improve the quality and
therefore the interpretation of your radiographic images.
Before performing a full series of foot radiographs,
it is common practice to recommend
removing the shoes. However, when acquiring
radiographs for the purpose of trimming and shoeing
issues, leaving the shoes in place can be beneficial.
Direct visualization of the weight-bearing surface
and the position of the shoe in relation to the hoof
capsule and distal phalanx can help in the planning
process. This simplifies evaluation of break-over,
sole depth, and balance of the foot. If a source of
lameness has been localized to the foot, removal of
the shoes may be necessary to obtain the additional
views necessary to fully evaluate the foot. Proper
shoe removal technique is a skill that the veterinarian
must be comfortable with.
Fig. 1. A, Dorsoproximal–45-degree–palmarodistal oblique view (DP-45-PDO). B, Radiographic image of a foot that has not been
packed. Note the artifact associated with the sulci of the foot. C, Traditional packing with putty material (Play-Doh©) eliminates
the majority of artifact; however, packing artifact can still be present. D, Foot is placed in a water bath, resulting in displacementof all gas and packing artifact.
Cleaning the foot of all particulate matter as well
as removing any fragmented wall and overgrown
sole and frog will reduce the potential for gas artifacts.
Any flakiness of or accumulations of debris
on the outer wall can be removed with either a rasp
or a sanding block. Radiographs taken to guide
trimming and shoeing do not require packing the
foot; if additional films are required, packing the foot
is recommended. Packing the sulci with appropriate
putty material reduces the likelihood of radiographic
artifact due to gas in the sulci. Liberal use
of the packing material should be used to fill the
depths of the sulci; however, overpacking will cause
packing artifact along the margins of the packing.
Traditional packing in horses that have deep center
sulci or overgrown bars can be difficult in eliminating
all gas artifacts. Placing the foot in a water
bath is an effective method of displacing trapped gas
deep within the sulci or wall (Fig. 1). The water
depth should be at a level just proximal to the heel
bulbs. Placing the cassette or digital sensor in a
plastic protective cover (trash bag) prior to placement
of the foot will reduce the potential for water
damage. A 50% increase in technique is recommended
when using digital radiography; when using
film-screen radiography, a significant increase in
milliamperes will also be necessary and will depend
on whether a grid is used or not.
Digital radiography (DR) has become commonplace
in equine practice and gives rise to a number of
advantages over film/screen radiography when evaluating
the foot. The advantages of DR over film/
screen radiography include digital postprocessing,
improved image quality, and improved archiving.
Digital radiographs have tremendous exposure latitude
compared with plain film radiography. With
a single image from a single exposure, the clinician
has the ability to adjust brightness and contrast,
allowing for visualization of multiple tissue densities.
Once captured, processed, and saved, the images can
be archived electronically, resulting in
easier storage and follow-up evaluation, comparison,
and manipulation.2 Despite the advantages of
digital technology, like any imaging technology, it
has its limitations. Furthermore, high-quality conventional
radiographs are satisfactorily diagnostic
for many purposes. However, because there is less
exposure latitude with conventional film/screen radiography,
it is important to establish standard
technique charts, taking into consideration the view
to be taken, what information is to be obtained from
the particular view, and the size of the foot.3 Additionally,
because the same degree of detail and
contrast is not as obvious on conventional film, establishing
multiple techniques (soft tissue and bone)
for each view is necessary to visualize and evaluate
soft and osseous tissues.
Fig. 2. Radiopaque markers (barium paste) placed at the appropriate locations aids in accurate identification of coronary band, dorsal hoof wall contour, and distal hoof wall.
Accurate identification of key points on the foot,
allowing for evaluation of dorsal hoof wall and heel
angles, sole depth, and medial and lateral wall
height, is not always possible, depending on the
technique used and the conformation of the foot.
Digital radiography allows improved visualization
of soft tissues; however, accurate identification of
the coronary band and heels can still be difficult.
Edge burn-through (saturation artifact) at the periphery
of soft tissues is a common artifact with
digital radiography.4 This in particular can result
in inaccurate assessment of hoof wall thickness.
Rigid metallic markers are often used to identify the
true border of the dorsal wall; however, accurate
identification of the wall length and contour is impossible
unless the marker equals the length of the
toe and can be contoured to the true shape of the
wall. Running a 2-mm bead of barium paste (can
be easily stored in and applied from a 60-mL syringe)
directly over the dorsal median hoof wall,
extending from the coronary band to the tip of the
toe, allows for accurate identification of the toe
length, wall contour and border, and an appreciation
of hoof wall distortion. Due to the increased beam
attenuation of the barium paste, a halo artifact
(U¨berschwinger) may be seen surrounding the barium,
but this will not preclude accurate border identification.
5 Spot marking at (1) widest point of the
proximal (coronary) and distal wall in the quarters,
(2) proximal and distal wall in the heels, and (3) 2.0
to 2.5 cm dorsal to the apex of the frog will aid in the
evaluation of quarter angles, quarter wall height,
heel angle and height, sole depth, and toe-to-heel
ratio (Fig. 2). Marking the dorsal hoof wall becomes
very useful in horses with upright feet, the
best example being the club-footed horse. As the
foot grows out in these horses, there is a propensity
for the dorsal wall to distort and flare, producing
multiple angles to the dorsal wall. Radiographic
evaluation of the dorsal wall with a conforming
marker allows accurate assessment of the distortion
of the wall and true angle of the foot.
It is crucial that the positioning of the patient,
foot, and x-ray beam be flawless when evaluating
the foot for the purposes of podiatry. True assessment
and measurement of the dorsal hoof wall and
heel angle, sole depth, joint congruity, medial to
lateral balance, and toe-to-heel ratio is dependent on
proper positioning. Slight abduction or adduction
of the limb or shifting of weight can cause joint
incongruity on the horizontal beam dorsal-palmar
view. The horse should be placed on a firm, level
footing, with the limbs squarely beneath the horse.
Limb conformation should also be evaluated prior to
taking radiographs. When placing the foot on the
positioning blocks, it is important to allow the foot to
position itself as dictated by the limbs conformation
(toed-in, toed-out). To reduce magnification, the
foot should be placed on the positioning block in such
a way that the foot is as close as possible to the
cassette or sensor plate.
Fig. 3. Rotating positioning block. A, Note copper metal insert used for identification of weight-bearing surface. B, Rotation of the block allows for accurate placement of the limb due to variations in conformation. C, Lateromedial (L-M) radiograph demonstrating identification of weight-bearing surface.
Commercial positioning blocks and stands are
available that aid in standardizing focal distance,
foot placement, and alignment of the x-ray beam.
Wood blocks of the appropriate size and height work
well; commercial blocks are available, but they are
also simple to fabricate to the practitioner's desired
specifications. A variation of the standard block
and one that the author uses is one that has been
adapted from one originally described by Caudron.4
It is composed of two independent circular blocks
connected in such a way that allows rotation of the
two halves. A cooper wire is embedded in the surface
of the block, forming a 15-cm circle; this acts as
a radiographic marker for the weight-bearing surface.
Regardless of the beam angle with the surface
of the block, a line drawn from the two apices of
the ellipse will be parallel to the weight-bearing
surface (Fig. 3). The rotational component of the
block works well for horses that exhibit abnormal
conformation such as a toed-in or toed-out conformation.
When the foot is placed on the block, the
rotation of the block allows the foot to position itself
naturally, influenced by the horse's conformation,
thereby alleviating the possibility of positional artifacts
such as joint space asymmetry. When designing
or purchasing a positioning block, it is important
to take into consideration the height of the block and
the center of the x-ray beam of your particular x-ray
machine. Incorporating some type of metallic
marker within the surface of the block is useful in
aiding accurate identification of the ground surface,
thus improving the accuracy of foot measurements.
The lateromedial and horizontal dorsopalmar projections
are the most useful views to perform when
evaluating the foot for conformation and balance.
Consideration of the area of interest as well as having
solid anatomical knowledge of the horse's foot is
important when performing these radiographic
Fig. 4. Lateromedial view (L-M). A and B, Beam orientation is perpendicular to the dorsopalmar plane of the foot. Parallel
alignment with the heel bulbs is useful in proper alignment of the x-ray machine. The beam is centered at a point halfway between
the toe and the heels and 1.5 to 2 cm proximal to the weight-bearing surface. C, Shoe placement and point of break-over can be
evaluated with L-M projection taken with the shoe on.
Fig. 5. Proper alignment of the x-ray beam demonstrating uneven alignment of the solar margins of the distal phalanx in a horse with
poor conformation. Evaluation of the horizontal dorsopalmar/plantar (HD-P) projection confirms the presence of poor hoof conformation.
The lateromedial (L-M) projection is performed
with the horse standing squarely on a flat, level
surface with each foot on a positioning block of equal
height. It is important that the cannon bone be
perpendicular to the floor in both the medial-tolateral
and dorsal-to-palmar planes. Keeping the
horse's head and neck straight is also important to
reduce the influence of uneven loading of any one
limb. Focal-film distance usually ranges between
24 and 28 inches; it is important to be consistent and
that once the technique is established, the focal-film
distance remains constant. Once the horse is positioned
squarely, proper beam alignment and positioning
is the next step in obtaining a workable
image. If the area of interest is the distal phalanx
and the purpose of the study is evaluating foot balance
and symmetry, the center of the beam should
be aimed 1.5 to 2.0 cm proximal to the weight-bearing
surface and midway between the toe and the
heel; the beam angle should be parallel with the heel
bulbs and the ground surface.3,6 This beam alignment
will produce a film that shows the medial and
lateral solar margins and palmar processes of the
distal phalanx superimposed on one another (in the
"normal" foot) (Fig. 4). Any obliquity in the image
can be corrected by raising or lowering the central
beam to adjust for variation in sole depth, or adjusting
the beam angle in relation to the heel bulbs.
Any adjustment in the height of the central beam
should be done with spacers, thereby eliminating
the possibility of hand-held errors.
The lateromedial projection is useful in evaluating
the relationship of the distal phalanx with the hoof
capsule and distal limb (hoof-pastern axis), location
of break-over, shoe placement, and quantitative parameters.
Malalignment of the foot and pastern is
seen in 72.8% of horses with forelimb lameness.7
Malalignment of the medial and lateral solar margins
is common with imbalance or poor conformation,
though many normal horses have some
asymmetry of the distal surface of the distal phalanx.
Additionally, resorption and remodeling of
the distal phalanx can alter the dorsal contour, solar
margins, and length of the distal phalanx as well as
alter the shape and angle of the solar margin, complicating
interpretation (Fig. 5). These changes are
seen with laminitis, pedal osteitis, and other sources
of chronic inflammation (heel bulb avulsions, osteomyelitis,
etc). Investigation with the orthogonal
view (HD-P) will help to clarify any solar margin
asymmetry seen in the L-M view.
If the navicular bone is the area of interest, the
x-ray beam should be centered at a point halfway
between the dorsal and palmar coronary band and
approximately 1 cm distal to the coronary band.
For the distal interphalangeal joint, the x-ray beam
is centered on the coronary band at the junction of
the dorsal and middle one-third of the coronary
Additional radiographic abnormalities commonly
identified in the L-M projection include osteophyte
or enthesophyte formation associated with the distal
interphalangeal (DIP) joint and navicular bone and
small focal irregularities at the insertions of the
deep digital flexor tendon and the distal sesamoidean
The horizontal dorsopalmar/plantar (HD-P) view
is also performed with the horse standing squarely
on two positioning blocks with the foot placed toward
the back of the block. The cassette is placed
on the palmar/plantar surface perpendicular to the
ground surface. The beam orientation is parallel to
the dorsal-palmar/plantar long axis of the foot on the
median plane of the foot. For consistency, the x-ray
beam is also centered 1.5 to 2 cm above the weightbearing
surface of the foot. Depending on the block
surface and the horse's conformation, using the dynamic
rotary block may add additional accuracy to
the interpretation of this image by alleviating any
artifact produced by poor conformation or foot placement.
Placement of a small dot of barium paste at
the hairline on the medial and lateral coronet will
result in accurate identification of the proximalmost
extent of the medial and lateral coronet. This
beam alignment will produce a film that projects of
the extensor process of the distal phalanx on the
median plane of the second phalanx (Fig. 6). Regardless
of whether a unilateral or bilateral study is
being performed, both feet should be placed on
blocks of equal height. Correct positioning reduces
the likelihood of artifactual changes to the joint
space that might otherwise be interpreted as joint
asymmetry and foot imbalance.
Fig. 6. Horizontal dorsopalmar view (HD-P). A, Beam orientation is parallel to the dorsopalmar plane of the foot and bisecting the
axial plane of the foot. As with the L–M projection, the x-ray beam is aimed 1.5 to 2 cm above the weight-bearing surface of the foot or 7 cm distal to the dorsal coronary band on a line perpendicular to the weight-bearing surface. B, Placement of a radio-opaque marker on the axial-dorsal surface of the wall helps in accurate identification of the extent of the hoof capsule. C, Shoe placement and accurate assessment of distal medial and lateral aspect of the wall can be evaluated with L-M projection taken with the shoe on.
This projection allows evaluation of medial to lateral
balance and conformation of the foot with observation
and measurement of the medial and
lateral wall length and angle, and the orientation of
the distal phalanx within the hoof capsule. Orientation
of the distal phalanx can be assessed by measuring
the distance from the articular surface of the
distal phalanx to the ground surface; the solar canal
can also be used as a reference point, but it is less
consistent. Using the solar margin as a point of
reference can be variable due to changes that can
occur in the bone.8 In horses with "ideal" conformation,
the articular surface of the distal phalanx is
parallel to the ground, as is a line between the
medial and lateral coronary band and, the medial
and lateral walls are of equal thickness, and the
distance from the medial and lateral solar margins
to the ground are similar.8 In horses with significant
rotation or angulation in the distal limb, the
relation of the distal phalanx with the ground may
not be as symmetrical. Furthermore, the distal interphalangeal
joint space should be approximately
even across its width regardless of angulation of the
phalanges. It is normal for the medial quarter wall
to be at a slightly steeper angle and subsequently
measure shorter in length.8 However, caution in
overinterpretation of joint incongruency is recommended,
because any malpositioning of the limb or foot can create the appearance of medial to lateral
imbalance (Fig. 7).
Fig. 7. HD-P view showing abnormal and normal distal interphalangeal joint symmetry in the same horse. A, The limb is slightly
abducted and the horse's weight is shifted to the contralateral limb. B, The horse is positioned squarely with both front limbs directly
underneath him and standing on identical positioning blocks.
Fig. 8. A, Measured lateromedial view (L-M). Quantitative assessment of the horse's foot. A, dorsal hoof wall length (DHWL); B,
dorsal hoof wall angle (DHWA); C and C, H-L zone, dorsal hoof wall thickness (DHWT); D, coronet to extensor distance (CED); E, solar angle (SA); F, sole depth (SD); G, heel angle (HA); H, toe-to-foot ratio (T:F). B, Measured horizontal dorsopalmar view (HD-P). Quantitative assessment of the horse's foot. A, lateral hoof wall length (LHWL); B, medial hoof wall length (MHWL); C, lateral P3 height (LP3H); D, medial P3 height (MP3H); E, lateral hoof wall angle (LHWA); F, medial hoof wall angle (MHWA); G, median angle
Quantitative methods of evaluating the horse's
foot have been developed.9 Measurements obtained
from the L-M and HD-P radiographic images
have been used to evaluate the effects of trimming
and shoeing,7,10,11 the stresses delivered to the deep
digital flexor tendon when hoof angle is
changed,12,13 the relationship between foot conformation
and lameness,1,14,15 and, in Thoroughbreds,
the relationship between solar angle and deep digital
flexor tendon injuries.12
Quantitative parameters that should be evaluated
include (1) the dorsal hoof wall angle (DHWA), (2)
the heel angle (HA), (3) the solar or palmar angle
(SA), (4) the dorsal hoof wall length (DHWL), (5) the
dorsal hoof wall thickness (DHWT), (6) the sole
depth (SD), (7) the distance between the dorsal coronary
band and the apex of the extensor process
(CED), and (8) the distribution of the dorsal and
palmar portions of the foot (toe-to-foot ratio, T:F),
separated by a line extending from the center of
rotation of the distal interphalangeal joint, perpendicular
to the weight-bearing surface (Fig. 8 and
Table 1). Subjective assessment of a well-taken radiograph
is frequently adequate for evaluating the
horse's foot; quantitative assessment is useful in
documenting changes in a foot over time and when
comparing feet on the same horse.
Changes in the DHWA, SA, and disproportionate
distribution of foot mass in relation to the center of
rotation can be appreciated on the L-M projection
and can be used to assess the dorsopalmar balance
of the foot. There is a wide range in what is
considered normal for the SA (2 to 8 degrees).
1,7,10,12,16,17 Minimal decreases or flattening
of the SA and DHWA have been associated with
lameness.1 An increase in the solar angle decreases
the deep digital flexor tendon force, and
therefore the force on the navicular bone; a 1-degree
increase in solar angle increases the pressure on the
navicular bone by 6%.14 At the same time, changes
in the SA or DHWA will result in changes in the
hoof-pastern axis. The center of rotation (COR)
separates the foot mass into dorsal and palmar/
plantar proportions. The COR is located midway
between the dorsal and palmar/plantar aspects of
the distal articulation of the middle phalanx; a line
dropped from this point and perpendicular to the
weight-bearing surface divides the dorsal and palmar/
plantar foot mass. In the “normal” foot the T:F
should be between 50% and 67%.7,18 If viewed from
the solar surface, the widest point of the foot should
correspond to the COR. Horses with long-toe, lowheel
syndrome usually have a low dorsal hoof wall
and solar angle, a long, narrow frog, and disproportionate
foot mass with excessive mass dorsal to the
center of rotation (>67%) (Fig. 9). A solar angle of
less than 2 degrees is usually associated with a
dorsopalmar imbalance; the center of rotation of the
DIP joint is displaced toward the heels, resulting in
an increase in the T:F ratio.8
||Dyson, 2011; 300
Mixed Breed Lame
|Kummer, 2009; 40
|Cripps, 1999; 25
Mixed Breed Sound
|Eliashar, 2004; 31
Irish Draught Sound
Mixed Breed Sound
||50.5 ±3.6 Degrees
||39 ±7.3 Degrees
||2.5 ±2.2 Degrees
Fig. 10. Lateral to medial radiograph of a normal foot.
Fig. 11. Case 1.
The DHWA, HA, SA, DHWL, SD, and T:F are
changed or potentially changed when the foot is
trimmed and shod and results in an overall change
in the equilibrium and balance of the foot. Repeating
the L-M projection after trimming and shoeing
the foot is useful in evaluating the effects of the trim.
Radiography of the foot remains the most practical,
economical, and informative imaging modality
in the field. Having said that, the quality of the
information gained from a radiograph is only as
good as the quality of the radiograph itself. Using
high-quality equipment, maintaining that equipment,
and mastering radiographic technique and
image acquisition are imperative to obtaining quality
information. Depending on the information desired
from a radiographic study, a limited number of
views are required. Based on the information
gained from the standard study and the clinical
presentation of the case, there are numerous other
specialty views and techniques that can be performed
to gain additional information. As stated
previously, a detailed lameness examination is also
required to guide the practitioner in deciding what
radiographic views should be taken. Radiography
is also very useful in more thorough evaluation of
the sound horse's foot for consultation with the farrier
with respect to trimming and shoeing protocols.
Although DR has improved the ability to visualize
and evaluate some of the soft tissue structures
within the foot, there remain great limitations to
imaging most soft tissue structures within the foot.
Using radiographs to assess the relationship between
the hoof and the underlying osseous structures
as an aid in assessing foot balance is about
developing an understanding of the relationships
between the position of the hoof capsule, the angle of
the distal phalanx within the hoof capsule, the symmetry
of the interphalangeal articulations, and the
alignment of the phalangeals. It should be mentioned
as a caveat at the outset that there isn't a
comprehensive scientific study to document all of
these relationships, but between the studies that are
available and clinical experience, there is enough
information to entertain a fruitful discussion on the
Dorsopalmar balance is primarily related to two
factors: the length of the toe and the alignment of
the foot-pastern axis. Radiographs are a very useful
adjunct because they convey information about
both the relationship between the hoof capsule and
the distal phalanx, and the relationship between the
phalanges. The potentially most useful estimates
of balance that can be derived from a lateral radiograph
are the depth of sole, the angle of the solar
margin of the distal phalanx, and the position between
the center of rotation of the distal interphalangeal
joint and the ground surface of the foot.
The angle of the dorsal hoof wall, the horizontal
distance between the dorsal margin of the toe and
hoof capsule, and the angles formed by the interphalangeal
joints may also be evaluated. However,
as this information is related to the former variables,
it is supplemental rather than additive. Additionally, the angles at the interphalangeal joints
vary with weight bearing and posture of the horse.
Lateral Radiograph - Normal
Fig. 9. Image demonstrating long-toe/low-heel syndrome, resulting
in an abnormal distribution of sole mass in relation to the
center of rotation (COR). Seventy-six percent of the sole mass is
dorsal to the COR.
In Figure 10, the depth of the sole is 19 mm, the
angle of the solar margin is 6° and the horizontal
distance between the center of rotation and the toe is
65% of total ground surface length. Additionally,
angle of the dorsal hoof wall is 57° and the horizontal
toe to distal phalanx distance is 3 cm.
Case 1. LF Distal Interphalangeal Joint Flexural Deformity
In Figure 11, there is asymetric hoof wall growth
as indicated by the asymetric growth pattern.
There is growth narrowing at the toe which widens
as it extends to the heels. Note the two different
DHWA's caused by the flaring of the mid-distal dorsal
hoofwall. Radiographically, the depth of the
sole is 10 mm; this is less than normal, though in
other horses it may be closer to normal. The angle
of the solar margin of the distal phalanx is 19°,
which is markedly greater than that of the normal
foot. Note that the dorsal 1/3 of the solar margin
has under gone significant remodeling due to the
deformity resulting in a solar angle of 0° in that
portion of the distal phalanx. The horizontal distance
between the center of rotation and the toe as a
percentage of overall ground surface length is 58%,
which is significantly reduced compared to the normal
lateral. Additionally, the angle of the dorsal
wall is markedly steeper (61°) than the normal
lateral. Also note that the significant distortion of
the distal dorsal hoof wall which is more accurately
highlighted with the radiopaque marker. The
horizontal distance from the toe of the capsule
to the dorsal margin of the distal phalanx is also
reduced. Furthermore, the foot-pastern axis is
clearly broken forward.
Case 2. Distal Interphalangeal Joint Dorsiflexion
(Negative Solar Margin Angle)
In Figure 12, there is significant asymetry in the
growth pattern throughout the foot. Note the ventral
divergence of the growth pattern in the heels
and the widening of the growth pattern at the toe.
The toe takes on a bulging or "bull nosed" appearance.
Clinical experience has shown that this foot
conformation is consistently predictive for horses
having negative solar margin angles when radio
graphed. Radiographically, the bulging appearance
of the DHW can be appreciated as well as the
dorsal margin of the distal phalanx. The distal interphalangeal
joint is dorsiflexed causing a brokenback
hoof-pastern axis. The depth of the sole is
24 mm at the dorsal margin of the distal phalanx; at
the plantar aspect this measurement is 18 mm.
In the hind foot it is common to see a significant
increase in the sole depth whereas in the front foot
sole depth may be consistent with normal and have
a reduced sole mass at the plantar aspect. The
angle of the solar margin of the distal phalanx is -2°
in the shod foot; if the foot was unshod the solar
angle would be -4°. The horizontal distance between
the center of rotation and the toe as a percentage
of overall ground surface length is 68%; this
is greater than it would be should the same foot have
a normal solar margin angle. As seen in horses
with flexural deformity the DHW exhibits multiple
DHWA's but due to convexity of the wall verses
concavity of the wall, the proximal DHWA measures
44° whereas the distal angle measures 62°.
Fig. 12. Case 2.
Dorsopalmar Radiograph - Normal
Fig. 13. Dorsal to palmar/plantar radiograph of a normal foot.
In Figure 13, the articular and solar margins of
the distal phalanx are parallel to the ground and
perpendicular to the axis of the proximal phalanges.
The distal interphalangeal joint space is even.
The coronary band when marked shows mediolateral
Case 3. LF Medial to Lateral Hoof Capsule Asymmetry
In Figure 14, the clinical features of this foot when
viewed from the dorsal aspect include a flare in the
medial wall and growth ring compression on the
medial side compared to the lateral side. These
features suggest increased stress/weight bearing by
the medial wall compared to the lateral wall. Additionally,
the horizontal distance between the pastern
joint and the coronary band appears less on the
medial side than the lateral side; personal experience
suggests that this indicates that the medial
side of the hoof has been displaced proximally.
Interestingly, the coronary band appears to be approximately
parallel to the ground. Radiographically,
one might expect the distal phalanx to be
tilted distolaterally and the medial side of the joint
space to be narrower laterally than it is medially.
However, radiographs show that the distal phalanx
is tilted distomedially. If this were the sole criteria
for farriery intervention, the intuitive solution
would be to trim the lateral side of the foot to restore
a "normal" horizontal alignment of the distal
phalanx. Examining the articulation of the distal
interphalangeal joint, however, shows it to be approximately
even medially and laterally, which is considered normal.
Additionally, the angle of the
pastern, is tilted laterally from the fetlock distally
(difficult to appreciate from this radiograph) so that
the axis of the pastern is at right angles to the
articular surface of the distal phalanx. Therefore,
in contrast to the initial intuitive position above,
these facts suggest that the alignment of the distal
phalanx in the hoof capsule is normal for this horse.
Therefore, the physical appearance of the foot and
the radiographs cannot be interpreted in isolation of
each other, and in this instance, the physical appearance
of the foot provides more information
about the balance of this limb than the radiographs.
Fig. 14. Case 3.
Case 4. RF Medial to Lateral Hoof Imbalance
Fig. 15. Case 4.
The foot in Figure 15 demonstrates a marked flare
of the medial hoof wall and considerable asymmetry
in the growth pattern of the wall. There is a rise in
the growth rings at the toe and widening of the rings
on the medial quarter. The coronary band also
takes on an undulating appearance. These features
suggest decreased loading/weight bearing by
the medial wall compared to the lateral wall and
increased loading or jamming at the toe. This
horse had severe White Line Disease and marked
lameness. Radiographically, the distal phalanx is
tilted distolaterally. Both the distal and proximal
interphalangeal joints show asymmetry between the
medial and lateral sides. Lastly, the distal phalanx
has displaced medially in the frontal plane in
relation to the middle phalanx. This pattern of observations
is almost conclusive of mediolateral imbalance.
Some of these findings may be present in
other circumstances in isolation which can lead to
misinterpretation if they are not all evaluated collectively.
For example, the tilting of the distal phalanx
and asymmetry of the interphalangeal joints
may occur in horses with uniaxial laminitis, but
with uniaxial laminitis, the medial wall should be
thicker than the lateral wall (not to mention different
clinical signs). Also, the distal phalanx may
occur tipped to one side in horses that have undergone
uniaxial cartilage loss in one of the two distal
articulations secondary to a degenerative process;
the affected side will show joint narrowing and may
be accompanied by tilting of the distal phalanx distally
on the other side, but the unaffected joint
should either not appear uneven or compressed on
the opposite side. Any ambiguity in interpretation
is likely to be cleared up by taking into account the
Case 5. RF Medial Uniaxial Laminitis
Fig. 16. Case 5.
The foot in Figure 16 demonstrates marked asymmetry.
Firstly, the center of the pastern does not
appear to be aligned with the center of the coronary
band; the coronary band appears to have shifted
laterally in relation to the coronary band. Additionally,
the medial wall has grown very little in
relation to the lateral wall as evidenced by the divergence
of the growth rings yet there is very little
disparity in medial and lateral wall length. The
separation that has occurred at the coronary band is
obvious because of the presence of granulation tissue.
Radiographically, there is marked tilting of
the distal phalanx. The interphalangeal joints are
asymmetrical, demonstrating narrowing laterally
and widening medially. Additionally, the distance
between the distal phalanx and the hoof wall is
increased. Furthermore, due to the displacement
of the medial distal phalanx the medial sole thickness
is also decreased. Also note that with relatively
similar medial and lateral wall length the
distance between the medial eminence of the distal
phalanx and the coronary band is increased in a
comparable manner to that seen between the extensor
process and the dorsal coronary band in horses
with classic dorsal rotational displacement. The
difference between this horse and the horse with
mediolateral imbalance is that the thickness of the
medial wall is significantly greater in this horse.
This radiographic appearance is almost pathognomonic
for laminitis with uniaxial distal displacement
of the distal phalanx.
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