Effect of limb positioning on the radiographic appearance of the distal and proximal interphalangeal joint spaces of the forelimbs of horses during evaluation of dorsopalmar radiographs


Contino, E.K.; Barrett, M.F.; Werpy, N.M.

Journal of the American Veterinary Medical Association 244(10): 1186-1190

2015


To determine the effect of limb positioning on the radiographic appearance of the distal and proximal interphalangeal joint spaces of the forelimbs of horses during evaluation of dorsopalmar radiographs. Evaluation study. 14 forelimbs from 9 adult horses. Each horse was in standing position with its forelimbs positioned on blocks. Dorsopalmar radiographs of each foot were obtained with the forelimbs positioned squarely (the metacarpus of both forelimbs was perpendicular to the ground as determined by visual examination [abducted 0°]; baseline) and abducted 5° and 10°. The width of the space at the medial and lateral aspects of the distal and proximal interphalangeal joints (medial and lateral joint space width, respectively) was measured. Mediolateral joint balance was calculated as the difference between the widths of the lateral and medial joint spaces, and joint space width and mediolateral joint balance were compared among all 3 positions. As the extent of limb abduction increased, the medial aspect of the proximal and distal interphalangeal joints became narrower, compared with the corresponding lateral aspect of those joints. For both the distal and proximal interphalangeal joints, the mediolateral joint balance differed significantly among all limb positions. Forelimb position significantly affected the mediolateral joint balance of the interphalangeal joints of horses. Thus, it is crucial that the forelimbs of horses be squarely positioned when dorsopalmar radiographs are obtained for accurate evaluation of interphalangeal joint space and balance.

Effect
of
limb
positioning
on
the
radiographic
appearance
of
the
distal
and
proximal
interphalangeal
joint
spaces
of
the
forelimbs
of
horses
during
evaluation
of
dorsopalmar
radiographs
Erin
K.
Contino,
DVM,
MS;
Myra
F
Barrett,
DVM,
MS;
Natasha
M.
Werpy,
DVM
Objective—To
determine
the
effect
of
limb
positioning
on
the
radiographic
appearance
of
the
distal
and
proximal
interphalangeal
joint
spaces
of
the
forelimbs
of
horses
during
evalu-
ation
of
dorsopalmar
radiographs.
Design—Evaluation
study.
Animals-14
forelimbs
from
9
adult
horses.
Procedures—Each
horse
was
in
standing
position
with
its
forelimbs
positioned
on
blocks.
Dorsopalmar
radiographs
of
each
foot
were
obtained
with
the
forelimbs
positioned
squarely
(the
metacarpus
of
both
forelimbs
was
perpendicular
to
the
ground
as
determined
by
visual
examination
[abducted
0°1;
baseline)
and
abducted
and
10°.
The
width
of
the
space
at
the
medial
and
lateral
aspects
of
the
distal
and
proximal
interphalangeal
joints
(medial
and
lateral
joint
space
width,
respectively)
was
measured.
Mediolateral
joint
balance
was
calcu-
lated
as
the
difference
between
the
widths
of
the
lateral
and
medial
joint
spaces,
and
joint
space
width
and
mediolateral
joint
balance
were
compared
among
all
3
positions.
Results—As
the
extent
of
limb
abduction
increased,
the
medial
aspect
of
the
proximal
and
distal
interphalangeal
joints
became
narrower,
compared
with
the
corresponding
lateral
as-
pect
of
those
joints.
For
both
the
distal
and
proximal
interphalangeal
joints,
the
mediolateral
joint
balance
differed
significantly
among
all
limb
positions.
Conclusions
and
Clinical
Relevance—Forelimb
position
significantly
affected
the
medio-
lateral
joint
balance
of
the
interphalangeal
joints
of
horses.
Thus,
it
is
crucial
that
the
forelimbs
of
horses
be
squarely
positioned
when
dorsopalmar
radiographs
are
obtained
for
accurate
evaluation
of
interphalangeal
joint
space
and
balance.
(J
Am
Vet
Med
Assoc
2014;244:1186-1190)
t'oot
characteristics,
including
joint
balance,
influ-
ence
the
gait,
joint
biomechanics,
and
soundness
of
horses."
Results
of
1
study'
indicate
that
DIP
joint
imbalance
affects
intra-articular
pressure
and
alters
ar-
ticular
contact
area,
leading
the
investigators
to
suggest
that
DIP
joint
imbalance
may
predispose
that
joint
to
the
development
of
osteoarthritis.
Additionally,
im-
proper
mediolateral
balance
has
been
associated
with
sheared
heels,
chronic
heel
soreness,
quarter
and
heel
cracks,
and
ossification
of
the
ungular
(collateral)
car-
tilages.
5
Consequently,
evaluation
of
interphalangeal
From
the
Departments
of
Clinical
Sciences
(Contino)
and
Environ-
mental
and
Radiological
Health
Sciences
(Barrett),
College
of
Veter-
inary
Medicine
and
Biomedical
Sciences,
Colorado
State
University,
Fort
Collins,
CO
80523;
and
the
Department
of
Clinical
Sciences,
College
of
Veterinary
Medicine,
University
of
Florida,
Gainesville,
FL
32610
(Werpy).
The
study
was
performed
at
Colorado
State
University.
Supported
by
the
Colorado
State
University
Department
of
Environ-
mental
and
Radiological
Health
Sciences.
The
authors
thank
Dr.
Francisco
Olea-Popelka
and
James
zumBrunnen
for
assistance
with
statistical
analyses
and
Katie
Yant
for
production
of
the
line
drawing.
Presented
in
abstract
form
at
the
58th
Annual
Convention
of
the
American
Association
of
Equine
Practitioners,
Anaheim,
Calif,
De-
cember
2012.
Address
correspondence
to
Dr.
Contino
).
ABBREVIATIONS
DIP
Distal
interphalangeal
PIP
Proximal
interphalangeal
joint
spaces
and
balance
is
frequently
performed,
es-
pecially
in
horses
with
lameness
isolated
to
the
foot
or
DIP
joint.
Although
the
equine
foot
can
be
visually
exam-
ined,
evaluation
of
the
interphalangeal
joint
spaces
is
best
accomplished
with
dorsopalmar
and
lateromedial
radiographs
of
the
foot.
To
accurately
assess
joint
bal-
ance,
a
horse
should
be
standing
squarely
with
its
forelimbs
on
symmetric
wooden
blocks
such
that
the
metacarpus
is
perpendicular
to
the
ground.
6
7
In
our
experience
in
a
clinical
setting,
the
forelimb
is
not
always
positioned
in
this
manner.
Although
it
may
seem
obvious
that
limb
position
would
affect
the
ra-
diographic
appearance
of
the
interphalangeal
joints,
a
scientific
basis
for
this
assumption
is
lacking.
Thus,
the
goal
of
the
study
reported
here
was
to
objective-
ly
quantify
the
effects
of
limb
position
on
the
radio-
graphic
appearance
of
DIP
and
PIP
joint
spaces
of
horses
during
evaluation
of
dorsopalmar
radiographs.
We
hypothesized
that
DIP
mediolateral
joint
balance
as
calculated
by
measurements
obtained
from
dorso-
1186
Scientific
Reports
JAVMA,
Vol
244,
No.
10,
May
15,
2014
palmar
radiographs
would
differ
significantly
between
radiographs
that
were
obtained
with
the
forelimb
squarely
positioned
and
those
that
were
obtained
with
the
forelimb
abducted.
Materials
and
Methods
Animals—Horses
owned
by
clients
of
the
Colo-
rado
State
University
Veterinary
Teaching
Hospital
and
veterinary
students
were
recruited
for
the
study
in
ac-
cordance
with
university
policy.
All
study
procedures
were
approved
by
the
Institutional
Animal
Care
and
Use
Committee
of
Colorado
State
University,
and
own-
er
consent
was
acquired
for
each
horse
prior
to
study
enrollment.
All
horses
included
in
the
study
were
or
had
been
previously
used
for
recreational
or
competi-
tive
riding
purposes
and
received
routine
foot
care
(ie,
trimming
or
shoeing
every
5
to
8
weeks).
Horses
were
at
various
stages
of
their
individual
trimming
or
shoe-
ing
cycle
when
examined.
Horses
were
excluded
from
the
study
if
visual
examination
of
the
forelimbs
revealed
marked
bilateral
conformational
abnormalities
such
as
clinically
evident
mediolateral
imbalance,
dorsopalmar
imbalance,
hoof
wall
deformities,
or
improper
toe
con-
formation
(ie,
toed-in
or
toed-out
stance).
Horses
with
inadequate
conformation
in
1
forelimb
were
included
in
the
study,
but
only
the
forelimb
with
correct
confor-
mation
was
evaluated.
Positioning
of
horses
for
radiography—Initially,
horses
were
positioned
squarely
(the
metacarpus
of
both
forelimbs
was
perpendicular
to
the
ground)
as
deter-
mined
by
visual
examination
from
the
front
and
side.
Briefly,
a
horse
was
considered
to
be
standing
in
a
square
position
from
the
front
when
a
plumb
line
dropped
from
the
point
of
the
shoulder
bisected
the
forelimb
and
hoof
into
medial
and
lateral
halves
of
equal
size,
and
from
the
side
when
a
plumb
line
dropped
from
the
point
of
the
shoulder
bisected
the
forelimb
and
hoof
into
cranial
and
caudal
halves
of
equal
size.
With
the
horse
standing
squarely,
the
length
of
the
forelimb
was
measured.
The
point
where
the
forelimb
connects
to
the
torso
(intersec-
tion
of
the
extensor
carpi
radialis,
brachialis,
and
lateral
head
of
the
triceps
brachii
muscles)
forms
an
easily
dis-
tinguishable
inverted
V
shape
that
was
used
as
the
proxi-
mal
landmark
for
forelimb
measurement
(Figure
1).
The
length
of
the
forelimb
from
this
landmark
to
the
ground
was
measured
with
a
weighted
string.
The
horses
were
then
positioned
squarely
with
both
forelimbs
on
identical
wooden
blocks
that
mea-
sured
4
cm
in
height;
this
was
the
baseline
position
(0°
abduction).
For
each
limb
evaluated,
a
dorsopalmar
radiograph
was
obtained
with
the
limb
in
baseline
po-
sition.
Then,
dorsopalmar
radiographs
were
obtained
with
the
limb
abducted
and
10';
the
order
in
which
the
radiographs
were
obtained
at
the
2
abduction
an-
gles
was
determined
in
a
random
manner.
The
trigono-
metric
tangent
function
was
used
to
determine
how
far
the
limb
had
to
be
abducted
from
the
baseline
position
to
achieve
and
10°.
Briefly,
with
the
limb
in
baseline
position,
the
hoof
created
a
90°
(right)
angle
with
the
ground.
The
trigonometric
tangent
function
states
that
in
a
right
triangle,
the
tangent
of
an
angle
is
the
length
of
the
opposite
side
of
the
triangle
divided
by
the
length
of
the
adjacent
side
of
the
triangle.
Thus,
if
the
length
of
the
limb
is
defined
as
the
opposite
side
of
the
tri-
angle
(Figure
1),
then
the
distance
the
foot
needs
to
be
moved
laterally
to
achieve
abduction
of
is
equal
to
the
length
of
the
limb
divided
by
the
tangent
of
85°,
and
the
distance
the
foot
needs
to
be
moved
laterally
to
achieve
abduction
of
10°
is
equal
to
the
length
of
the
limb
divided
by
the
tangent
of
80°.
All
measurements
were
calculated
from
the
midline
of
the
toe,
and
the
same
investigator
(EKC)
measured
and
positioned
all
limbs.
Dorsopalmar
radiographs—With
the
limb
in
base-
line
position
and
abducted
and
10°
from
baseline,
dorsopalmar
radiographs
were
obtained
with
a
digital
radiographic
system.a
For
the
radiograph
obtained
with
the
limb
in
the
baseline
position,
a
laser
level
centered
on
top
of
the
x-ray
generator
was
used
to
project
a
la-
ser
beam
on
the
forelimb
being
evaluated.
The
location
of
the
generator
was
adjusted
until
the
projected
laser
beam
bisected
the
forelimb
and
hoof
into
equal
medial
and
lateral
halves
(ie,
the
dorsal
midline
of
the
limb
was
visually
approximated
by
the
projected
beam).
The
x-ray
beam
was
directed
parallel
to
the
ground
and
fo-
cused
on
the
dorsal
midline
at
the
level
of
the
coronary
band.
The
film
focal
distance
was
consistently
main-
tained
at
1
m
for
all
radiographs,
which
were
obtained
by
1
investigator
(EKC).
Figure
1—Illustration
of
a
horse
standing
squarely
(the
metacar-
pus
of
both
forelimbs
was
perpendicular
to
the
ground
[O
abduc-
tion])
when
viewed
from
the
front.
The
black
dot
on
the
left
forelimb
represents
the
intersection
of
the
extensor
carpi
ra-
dialis,
brachialis,
and
lateral
head
of
the
tri-
ceps
brachii
muscles,
which
forms
an
easily
distinguishable
invert-
ed
V
shape
that
was
used
as
the
proximal
anatomic
landmark
for
measurement
of
forelimb
length.
A
diagram
of
a
right
tri-
angle
has
been
super-
imposed
on
the
right
forelimb
as
a
visual
aid
to
describe
how
the
trigonometric
tangent
function
was
used
to
determine
the
distance
that
the
foot
had
to
be
moved
laterally
(X)
to
achieve
abduction
of
and
10°.
In
a
right
triangle,
the
tangent
of
an
angle
is
the
length
of
the
opposite
side
of
the
triangle
divided
by
the
length
of
the
ad-
jacent
side
of
the
triangle.
If
the
proximal
angle
of
the
triangle
is
or
10°
(ie,
extent
of
abduction),
then
the
remaining
angle
of
the
right
triangle
is
85°
or
80°,
respectively.
If
the
length
of
the
forelimb
is
defined
as
the
opposite
side
of
the
triangle,
then
the
X
to
achieve
abduction
of
is
equal
to
the
length
of
the
limb
di-
vided
by
the
tangent
of
85°
and
the
X
to
achieve
abduction
of
10°
is
equal
to
the
length
of
the
limb
divided
by
the
tangent
of
80°.
L
X
JAVMA,
Vol
244,
No.
10,
May
15,
2014
Scientific
Reports
1187
Joint
and
forelimb
position
Medial
joint
space
width
(mm)
Lateral
joint
space
width
(mm)
Joint
balance
(mm)
DIP
Baseline
4.1
±
0.4
(3.6-4.7)
4.6
±
1.1
(3.2-6.5)
0.4
±
1.1
(-1.5
to
2.3)
abduction
3.8
±
0.3
(3.4-4.3)
5.4
±
1.3
(3.6-7.3)
1.6
±
1.2
(-0.7
to
3A)*
10°
abduction
3.5
±
0.4
(2.8-3.9)
6.0
±
1.4
(4.2-8.0)
2.5
±
1.3
(0.6
to
5.2)*t
PIP
Baseline
2.0
±
0.3
(1.7-2.7)
2.0
±
0.2
(1.6-2.4)
0.0
±
0.3
(-0.7
to
0.4)
abduction
2.1
±
0.2
(1.7-2.3)
2.3
±
0.3
(1.9-2.8)
0.2
±
0.3
(-0.2
to
0.9)*
10°
abduction
2.0
±
0.2
(1.7-2.3)
2.4
±
0.4
(1.9-3.3)
0.4
±
0.4
(0.0
to
1.4)*t
Forelimbs
were
excluded
from
the
study
if
visual
examination
revealed
conformational
abnormalities
(me-
diolateral
imbalance,
dorsopalmar
imbalance,
hoof
wall
deformities,
or
improper
toe
conformation
[ie,toed-in
or
toed-out
stance]).
The
DIP
and
PIP
joints
were
measured
at
the
widest
aspect
of
the
distal
epicondyle
of
the
second
and
first
phalanges,
respectively.
Each
measurement
was
then
equally
divided
into
sixths,
and
the
medial
and
lateral
joint
space
widths
were
measured
at
1/6
of
the
distance
from
the
most
medial
and
lateral
aspects
of
the
joint,
respectively.
Joint
balance
was
calculated
by
subtraction
of
the
medial
joint
space
width
from
the
lateral
joint
space
width.
*Within
a
joint
and
column,
value
differs
significantly
(1
3
0.05)
from
that
at
baseline.
tWithin
a
joint
and
column,
value
differs
significantly
0.05)
from
that
at
abduction.
Measurement
of
interphalangeal
joint
space-
Each
radiograph
was
evaluated
by
2
investigators
(EKC
and
MFB).
The
width
of
the
space
at
the
medial
and
lateral
aspects
of
the
DIP
and
PIP
joints
(ie,
medial
and
lateral
joint
spaces,
respectively)
was
measured.
To
en-
sure
that
each
joint
space
was
measured
at
a
consistent
location,
the
DIP
and
PIP
joints
were
first
measured
at
the
widest
aspect
of
the
distal
epicondyle
of
the
second
and
first
phalanges,
respectively.
Each
joint
measure-
ment
was
then
divided
equally
into
sixths,
and
the
me-
P2
P3
Figure
2-Dorsopalmar
radiographic
image
of
the
distal
aspect
of
a
forelimb
of
an
adult
horse
standing
squarely;
lateral
is
to
the
right.
To
ensure
that
each
joint
space
was
measured
at
a
consis-
tent
location,
the
DIP
and
PIP
joints
were
measured
at
the
widest
aspect
of
the
distal
epicondyle
of
the
second
and
first
phalan-
ges
(horizontal
lines),
respectively.
Each
measurement
was
then
equally
divided
into
sixths,
and
the
medial
and
lateral
joint
space
widths
were
measured
at
1/6
of
the
distance
from
the
most
me-
dial
and
lateral
aspects
of
the
joint
(vertical
lines),
respectively.
P1
=
First
phalanx.
P2
=
Second
phalanx.
P3
=
Third
phalanx.
See
Figure
1
for
remainder
of
key.
dial
and
lateral
joint
space
widths
were
measured
at
1/6
of
the
distance
from
the
most
medial
and
lateral
aspects
of
the
joint,
respectively
(Figure
2).
All
radiographs
were
viewed
by
use
of
a
commercial
viewing
systemb
with
the
capability
to
obtain
measurements
to
the
near-
est
0.1
mm.
The
mediolateral
joint
balance
(ie,
joint
balance)
was
defined
as
the
difference
in
the
width
between
the
medial
and
lateral
aspects
of
the
joint
and
was
calcu-
lated
by
subtracting
the
width
of
the
medial
joint
space
from
the
width
of
the
lateral
joint
space.
Therefore,
the
joint
balance
was
0
when
the
widths
of
the
medial
and
lateral
joint
spaces
were
equal,
<
0
when
the
medial
joint
space
was
wider
than
the
lateral
joint
space,
and
>
0
when
the
lateral
joint
space
was
wider
than
the
me-
dial
joint
space.
Data
analysis-A
histogram
was
created
to
visually
examine
data
for
normality,
and
a
Shapiro-Wilk
test
was
performed
to
formally
evaluate
data
for
normality.
De-
scriptive
statistics
were
generated
for
the
widths
of
the
medial
and
lateral
joint
spaces
and
joint
balance
for
the
DIP
and
PIP
joints
by
use
of
a
commercial
spreadsheet
program.c
For
both
the
DIP
and
PIP
joints,
a
mixed
linear
regression
model
was
used
to
compare
the
joint
balance
at
each
of
the
3
positions
(baseline
and
and
10°
abduction),
with
limb
included
in
the
model
as
a
random
effect
and
limb
position
included
in
the
model
as
a
fixed
effect.
Regression
analyses
were
performed
with
commercially
available
software,d
and
values
of
P
0.05
were
considered
significant.
Results
Fourteen
forelimbs
(8
left
and
6
right)
from
9
adult
horses
(7
active
and
2
retired)
were
evaluated.
Horses
ranged
from
4
to
24
years
of
age
and
153
to
173
cm
in
height.
Breeds
represented
included
Quarter
Horse
(n
=
3),
Thoroughbred
(1),
Morgan
(1),
American
Paint
(1),
and
mixed
(3).
Horses
were
used
for
western
per-
Table
1-Mean
±
SD
(range)
width
of
the
space
at
the
medial
and
lateral
aspects
of
the
joint
(medial
and
lateral
joint
space
width,
respectively)
and
mediolateral
joint
balance
of
the
DIP
and
PIP
joints
in
the
forelimbs
(n
=
14;
right,
8;
left,
6)
of
9
adult
horses
as
determined
from
evaluation
of
dorsopalmar
radiographs
obtained
with
the
forelimbs
positioned
squarely
(the
metacarpus
of
both
forelimbs
was
perpendicular
to
the
ground
as
determined
by
visual
examination
[abducted
0°];
baseline)
and
abducted
and
10°.
1188
Scientific
Reports
JAVMA,
Vol
244,
No.
10,
May
15,
2014
A
L4
-mmi..11111.11hrmajlilit
.011111L-
Figure
3—Dorsopalmar
radiographic
images
of
the
distal
aspect
of
a right
forelimb
of
an
adult
horse
that
is
standing
squarely
(A;
baseline)
and
with
the
limb
abducted
(B)
and
10°
(C);
lateral
is
to
the
left
in
all
panels.
For
both
the
DIP
and
PIP
joints,
notice
that
the
width
of
the
space
at
the
medial
aspect
of
the
joint
decreases,
whereas
the
width
of
the
space
at
the
lateral
aspect
of
the
joint
increases
as
the
extent
of
limb
abduction
increases.
See
Figure
1
for
remainder
of
key.
formance
(n
=
4),
trail
riding
(3),
or
English
perfor-
mance
(2).
The
mean
length
of
the
forelimbs
evalu-
ated
was
0.89
m
(range,
0.84
to
0.95
m).
The
mean
distance
required
to
abduct
forelimbs
and
10°
was
7.9
cm
(range,
7.4
to
8.4
cm)
and
15.7
cm
(range,
14.7
to
16.8
cm),
respectively.
DIP
and
PIP
joint
measurements—Measurements
of
the
medial
and
lateral
joint
space
widths
and
joint
balance
for
the
PIP
and
DIP
joints
are
summarized
(Table
1).
For
both
the
DIP
and
PIP
joints,
the
space
at
the
medial
aspect
of
the
joint
became
narrower
and
the
space
at
the
lateral
aspect
of
the
joint
became
wider
as
the
degree
of
limb
abduction
increased
(Figure
3).
Consequently,
the
joint
balance
increased
significantly
between
baseline
and
abduction,
between
baseline
and
10°
abduction,
and
between
abduction
and
10°
abduction
for
both
joints.
Discussion
Results
of
the
present
study
indicated
that
limb
po-
sition
significantly
affected
the
appearance
of
both
the
DIP
and
PIP
joint
spaces
on
dorsopalmar
radiographs
of
the
forelimbs
of
clinically
normal
horses.
For
example,
the
mean
mediolateral
joint
balance
of
the
DIP
joint
increased
from
0.4
mm
at
baseline
(0°
abduction)
to
1.6
mm
at
abduction
and
2.5
mm
at
10°
abduction.
The
mean
distance
that
the
forelimb
had
to
be
moved
to
achieve
abduction
of
and
10°
was
7.9
and
15.7
cm,
respectively.
The
mean
width
of
the
forelimb
hooves
of
all
study
horses
was
approximately
14
cm;
thus,
lateral
movement
of
the
forelimb
less
than
the
width
of
1
hoof
had
a
significant
effect
on
the
radiographic
appearance
of
interphalangeal
joint
spaces
and
calculation
of
joint
balance.
Therefore,
it
is
critical
that
the
forelimbs
of
horses
be
properly
positioned
(ie,
abduction)
when
dorsopalmar
radiographs
are
obtained
so
that
interpha-
langeal
joint
balance
can
be
accurately
assessed.
The
space
at
the
medial
aspect
of
the
joint
(medial
joint
space)
became
narrower
and
the
space
at
the
later-
al
aspect
of
the
joint
(lateral
joint
space)
became
wider
as
the
forelimb
was
abducted
from
baseline;
however,
not
all
joints
transitioned
from
a
balanced
(joint
bal-
ance,
0)
to
an
unbalanced
state
when
the
limb
was
ab-
ducted.
Some
horses
had
a
joint
balance
<
0
at
baseline.
As
expected,
forelimb
abduction
in
those
horses
invariably
caused
the
medial
joint
space
to
narrow
and
the
lateral
joint
space
to
widen,
and
joint
balance
was
frequently
achieved
in
those
horses
with
the
forelimb
abducted.
Conversely,
for
horses
with
balanced
joints
at
baseline,
the
joint
balance
deviated
from
0
and
generally
increased
with
forelimb
abduc-
tion.
In
the
present
study,
mediolateral
joint
balance
varied
substantially
among
horses,
as
evidenced
by
the
calculation
of
means
with
large
SDs
for
both
the
DIP
and
PIP
joints
at
all
limb
positions
(baseline
and
and
10°
abduction).
Ad-
ditionally,
this
variation
was
limb
depen-
dent
rather
than
horse
dependent.
For
example,
in
one
of
the
study
horses
that
had
both
forelimbs
evaluated,
abduction
of
1
forelimb
resulted
in
the
interphalangeal
joints
transitioning
from
balanced
to
unbalanced,
whereas
abduction
of
the
con-
tralateral
forelimb
resulted
in
the
interphalangeal
joints
transitioning
from
unbalanced
to
balanced.
For
accurate
evaluation
of
the
interphalangeal
joint
spaces,
it
is
recommended
that
the
horse
be
positioned
squarely
(the
metacarpus
of
both
forelimbs
perpendicu-
lar
to
the
ground
as
determined
by
visual
examination)
when
dorsopalmar
radiographs
are
obtained.
Proper
positioning
can
be
achieved
by
visual
assessment
of
the
horse
from
the
front
and
side
and
can
be
enhanced
by
the
dropping
of
a
plumb
line
from
the
point
of
the
shoulder
to
the
ground
or
a
laser
level
centered
on
top
of
the
x-ray
generator.
These
methods
were
useful
in
the
present
study
and
are
feasible
for
use
in
the
field.
Some
equine
practitioners
have
suggested
that
improper
positioning
of
the
forelimb
can
be
distin-
guished
from
true
mediolateral
imbalance
radiographi-
cally
because
improper
positioning
will
cause
medio-
lateral
imbalance
of
all
joints
in
the
distal
aspect
of
the
limb.
6
However,
in
the
present
study,
dorsopalmar
ra-
diographs
obtained
at
baseline
and
abduction
were
sometimes
difficult
to
distinguish
from
one
another,
especially
if
the
person
evaluating
the
radiographs
was
unaware
of
the
limb
position.
Generally,
dorsopalmar
radiographs
obtained
at
10°
abduction
were
obviously
malpositioned.
Furthermore,
the
mean
medial
and
lat-
eral
widths
of
the
PIP
joint
space
changed
0.4
mm
between
baseline
and
10°
abduction,
and
such
small
changes
may
not
be
readily
detectable.
Thus,
assess-
ment
of
proper
limb
position
is
difficult
to
assess
solely
by
evaluation
of
radiographic
images.
It
is
important
to
evaluate
the
position
of
the
limb
while
the
images
are
being
obtained
and
educate
technicians
about
the
im-
portance
of
proper
limb
positioning.
Given
the
increas-
ing
frequency
with
which
dorsopalmar
radiographs
of
equine
limbs
are
being
obtained
and
the
fact
that
these
radiographs
are
being
interpreted
in
various
locations
by
various
practitioners,
determination
of
an
accurate
and
standardized
method
to
indicate
limb
position
at
the
time
radiographic
images
were
obtained
warrants
further
study.
To
our
knowledge,
objective
studies
performed
to
assess
the
extent
of
mediolateral
imbalance
that
a
JAVMA,
Vol
244,
No.
10,
May
15,
2014
Scientific
Reports
1189
horse
can
tolerate
without
clinical
implications
or
the
development
of
lameness
are
lacking.
A
veterinarian
experienced
with
equine
lameness
in
both
clinical
and
research
settings
becomes
concerned
about
possible
pathological
changes
when
the
mediolateral
balance
of
the
DIP
joint
is
2
mm.e
In
the
present
study,
the
DIP
joint
achieved
a
mean
mediolateral
joint
balance
>
2
mm
with
the
limb
abducted
10°.
Interestingly,
re-
sults
of
1
study
8
indicate
that
catastrophic
musculoskel-
etal
injury
in
Thoroughbreds
decreased
as
the
ratio
of
lateral
to
medial
sole
width
and
surface
area
(ie,
condi-
tions
that
favor
mediolateral
imbalance)
increased.
Al-
though
that
study
8
measured
the
width
and
surface
area
of
the
soles
of
study
horses
rather
than
the
mediolateral
balance
of
the
interphalangeal
joint
spaces,
its
findings
emphasize
the
fact
that,
even
though
it
is
assumed
that
a
joint
balance
of
0
mm
is
always
ideal,
scientific
evi-
dence
to
confirm
that
presumption
is
lacking.
In
the
present
study,
the
joint
balance
of
the
PIP
joint
differed
significantly
among
the
3
limb
positions;
however,
it
is
unknown
whether
these
differences
are
clinically
relevant.
Abduction
of
the
limb
10°
from
baseline
resulted
in
a
0.4-mm
increase
in
the
joint
bal-
ance,
and
although
that
may
seem
inconsequential,
it
represented
a
20%
increase
in
the
width
of
the
lateral
joint
space
and
a
20%
decrease
in
the
width
of
the
me-
dial
joint
space
from
baseline,
which
might
be
clinically
relevant.
For
horses
in
which
mediolateral
imbalance
is
di-
agnosed,
it
is
important
to
correlate
radiographic
find-
ings
with
clinical
findings
such
as
the
presence
of
lame-
ness
isolated
to
the
interphalangeal
joints
or
region,
effusion
of
the
interphalangeal
joints,
and
imbalance
in
the
mediolateral
dynamic
landing
pattern
of
the
foot.
Additionally,
it
is
necessary
to
consider
the
cause
of
the
imbalance.
Mediolateral
imbalance
can
be
caused
by
narrowing
of
the
joint
space
owing
to
pathologi-
cal
changes,
discrepancies
between
the
lengths
of
the
medial
and
lateral
hoof
walls,
or
limb
position
when
the
radiograph
was
obtained.
In
horses
with
loss
of
ar-
ticular
cartilage,
the
primary
radiographic
abnormality
identified
is
narrowing
of
the
joint
space
in
the
affected
area.
Thus,
it
is
critical
that
the
limb
be
properly
posi-
tioned
when
the
dorsopalmar
radiograph
is
obtained
to
minimize
the
potential
for
misclassification
of
a
patho-
logically
narrowed
joint
space.
Standing
MRI
is
a
modality
that
is
becoming
fre-
quently
used
to
image
the
feet
of
horses,
and
the
re-
sults
of
the
present
study
might
be
applicable
to
the
interpretation
of
standing
MRI
images,
although
verifi-
cation
of
such
was
beyond
the
scope
of
the
this
study.
During
standing
MRI,
horses
must
be
positioned
in
a
base-wide
stance
(ie,
with
the
limb
abducted)
to
ac-
commodate
the
study
limb
within
the
magnet,
9
al-
though
the
degree
of
that
base-wide
stance
has
not
been
described.
Results
of
the
present
study
indicate
that
a
base-wide
stance
causes
a
narrowing
of
the
me-
dial
joint
space
relative
to
the
lateral
joint
space,
which
supports
our
clinical
observations
of
joint-space
incon-
gruency
on
standing
MRI
images.
This
is
an
important
point
for
consideration
because
the
ability
to
accurately
evaluate
articular
cartilage
in
a
live
horse
by
means
of
low-field
standing
MRI
has
yet
to
be
investigated.
Forelimb
position
has
a
significant
effect
on
the
radiographic
appearance
of
the
interphalangeal
joint
spaces
of
the
forelimbs
in
clinically
normal
adult
hors-
es.
In
the
field,
a
plumb
line
or
laser
level
can
be
used
to
aid
in
ensuring
that
a
horse
is
squarely
positioned
in
preparation
for
obtaining
dorsopalmar
radiographs
of
the
forelimbs.
When
there
is
radiographic
evidence
of
narrowing
of
an
interphalangeal
joint
space,
it
is
im-
portant
to
consider
clinical
findings
as
well
as
limb
po-
sition
during
radiographic
examination,
which
can
be
difficult
to
determine
solely
from
radiographic
appear-
ance.
An
abnormally
narrow
DIP
joint
space
observed
on
a
dorsopalmar
radiographic
image
of
a
properly
po-
sitioned
forelimb
could
be
indicative
of
pathological
loss
of
articular
cartilage,
especially
in
horses
in
which
lameness
has
been
localized
to
the
DIP
joint.
Proper
positioning
of
the
forelimb
during
radiographic
exami-
nation
is
crucial
for
accurate
evaluation
of
the
interpha-
langeal
joints
of
horses.
a.
Mark
III,
Sound-Eklin,
Carlsbad,
Calif.
b.
iSite,
Philips
Healthcare,
Andover,
Mass.
c.
Excel,
Microsoft
Corp,
Redmond,
Wash.
d.
PROC
MIXED,
SAS,
version
9.1.3,
SAS
Institute
Inc,
Cary,
NC.
e.
Frisbie
DD,
Orthopaedic
Research
Center,
Department
of
Clini-
cal
Sciences,
College
of
Veterinary
Medicine
and
Biomedical
Studies,
Colorado
State
University,
Fort
Collins,
Colo:
Personal
communication,
2012.
References
1.
Viitanen
MJ,
Wilson
AM,
McGuigan
HP,
et
al.
Effect
of
foot
bal-
ance
on
the
intra-articular
pressure
in
the
distal
interphalangeal
joint
in
vitro.
Equine
VetJ
2003;35:184-189.
2.
Baxter
GM,
Stashak
TS.
Examination
for
lameness:
history,
visual
exam,
palpation,
and
manipulation.
In:
Baxter
GM,
ed.
Adams
and
Stashales
lameness
in
horses.
6th
ed.
Chichester,
West
Sussex,
England:
Wiley-Blackwell,
2011;109-122.
3.
Parks
AH.
Foot
balance,
conformation
and
lameness.
In:
Ross
MW,
Dyson
SJ,
eds.
Diagnosis
and
management
of
lameness
in
the
horse.
2nd
ed.
St
Louis:
Elsevier,
2011;286-287.
4.
Firth
EC,
Schamhardt
HC,
Hartman
W
Measurements
of
bone
strain
in
foals
with
altered
foot
balance.
Am
J
Vet
Res
1988;49:261-265.
5.
Balch
0,
Butler
D,
White
K,
et
al.
Hoof
balance
and
lameness:
improper
toe
length,
hoof
angle,
and
mediolateral
balance.
Compend
Contin
Educ
Pract
Vet
1995;17:1503-1509.
6.
Kaneps
AJ,
Turner
TA.
Disease
of
the
foot.
In:
Hinchcliff
KW,
Kaneps
AJ,
Geor
RJ,
eds.
Equine
sports
medicine
and
surgery.
London:
Saunders,
2004;266-267.
7.
Eggleston
RB.
Value
of
quality
foot
radiographs
and
their
impact
on
practical
farriery,
in
Proceedings.
58th
Annu
Cony
Am
Assoc
Equine
Pract
2012;164-175.
8.
Kane
AJ,
Stover
SM,
Bock
KB,
et
al.
Hoof
balance
characteris-
tics
associated
with
catastrophic
injury
of
Thoroughbred
race-
horses,
in
Proceedings.
44th
Annu
Cony
Am
Assoc
Equine
Pract
1998;281-283.
9.
Werpy
N.
Low-field
MRI
in
horses:
practicalities
and
image
ac-
quisition.
In:
Murray
RC,
ed.
Equine
MRI.
West
Sussex,
Eng-
land:
Blackwell
Publishing
Ltd,
2011;81.
1190
Scientific
Reports
JAVMA,
Vol
244,
No.
10,
May
15,
2014