Osteochondrosis of the tarsocrural joint and osteochondral fragments in the fetlock joints: incidence and influence on racing performance in a selected group of Standardbred trotters


Fabio Torre, D.V.M.; Motta, M.

Proceedings of the Annual Convention of the AAEP 46: 287-294

2000


The relationship between tarsocrural osteochondrosis (OCD) and presence of osteochondral fragments in fetlock joints has been previously investigated in racehorses, especially Standardbreds. The increased knowledge of the problem and the introduction and spread of arthroscopy probably reduced the negative effects of these lesions on racing careers. A large group of Standardbred yearlings have been radiographically investigated in this study, and racing results of horses affected by tarsocrural OCD or osteochondral fragments in the metacarpo/tarso-phalangeal joints have been compared with results of non-affected horses. Most of the lesions did not negatively affect the racing performance, and a fair to good prognosis can be anticipated for selected radiographic lesions identified in yearling Standardbreds.

TIMELY
TOPICS
Osteochondrosis
of
the
Tarsocrural
Joint
and
Osteochondral
Fragments
in
the
Fetlock
Joints:
Incidence
and
Influence
on
Racing
Performance
in
a
Selected
Group
of
Standardbred
Trotters
Fabio
Torre,
DVM
and
Mario
Motta,
Professor
of
Physics
The
relationship
between
tarsocrural
osteochondrosis
(OCD)
and
presence
of
osteochondral
frag-
ments
in
fetlock
joints
has
been
previously
investigated
in
racehorses,
especially
Standard-
breds.
The
increased
knowledge
of
the
problem
and
the
introduction
and
spread
of
arthroscopy
probably
reduced
the
negative
effects
of
these
lesions
on
racing
careers.
A
large
group
of
Standard-
bred
yearlings
have
been
radiographically
investigated
in
this
study,
and
racing
results
of
horses
affected
by
tarsocrural
OCD
or
osteochondral
fragments
in
the
metacarpo/tarso-phalangeal
joints
have
been
compared
with
results
of
non-affected
horses.
Most
of
the
lesions
did
not
negatively
affect
the
racing
performance,
and
a
fair
to
good
prognosis
can
be
anticipated
for
selected
radiographic
lesions
identified
in
yearling
Standardbreds.
Authors'
addresses:
Clinica
Equina
Bagnarola,
Via
Armiggia,
25,
40050,
Bagnarola,
Bologna,
Italy
(Torre);
and
Dipartimento
di
Fisica,
University
di
Bologna,
Viale
Berti
Pichat
6/2,
40127
Bologna,
Italy
(Motta).
0
2000
AAEP.
1.
Introduction
Intra-articular
bony
fragments
represent
a
frequent
finding
in
Standardbred
horses.
Their
incidence
and
clinical
significance
have
been
the
subject
of
several
surveys
and
clinical
reports.
Several
studies
and
surveys
have
been
published
in
the
past
15
years,
in
order
to
focus
on
different
aspects
of
equine
osteo-
chondrosis
(OCD)
and
osteochondral
intra-articular
fragments
including
proposed
causes
and
aetiopatho-
genesis,
1-6
epidemiology,
?-14
genetic
factors,
15-17
clin-
ical
aspecta,18-22
and
surgical
management
23-28
The
sites
of
predilection
of
developmental
and
trau-
matic
lesions
in
Standardbreds
have
been
identified
and
today
routine
pre-sale
or
pre-purchase
radio-
graphic
investigations
mostly
focus
on
the
tarsocrural
and
fetlock
joints.
Surveys
on
yearlings
are
also
use-
ful
in
order
to
evaluate
the
incidence
of
lesions
in
a
population
and
for
planning
preventative
surgery,
most
of
the
lesions
having
developed
by
1
year
of
age.
The
purpose
of
this
study
was
to
investigate
the
inci-
dence
of
OCD
in
the
tarsocrural
joint
and
osteochon-
dral
fragments
in
the
fetlock
joints
of
a
large
group
of
Standardbred
yearlings,
and
to
compare
the
racing
performance
of
affected
and
unaffected
horses.
2.
Materials
and
Methods
This
study
includes
three
groups
of
Standardbred
yearlings
from
three
different
generations
(born
in
1990,
1991,
and
1992)
admitted
to
the
selected
ses-
sion
of
the
Standardbred
yearling
sales
in
Italy.
NOTES
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TOPICS
Each
yearling,
before
acceptance,
had
to
meet
cer-
tain
standards
of
pedigree
and
conformation.
Each
accepted
horse
was
then
submitted
to
a
basic
radio-
graphic
examination
including
at
least
one
view
(lateromedial)
for
each
fetlock
and
two
views
(dorso-
lateral-plantaromedial
oblique
and
plantarolateral-
dorsomedial
oblique)
for
each
tarsocrural
joint.
Extra
views
were
obtained
when
needed,
particu-
larly
in
order
to
better
visualize
the
distoplantar
aspect
of
hind
fetlocks
(dorsolateral-plantaromedial
and
dorsomedial-plantarolateral
oblique
views
with
a
45°
proximodistal
direction).
A
radiographic
re-
port
was
prepared
for
each
horse.
Because
of
the
radiographs
selected,
comments
concerned
only
the
tarsocrural
and
metacarpo/tarso-phalangeal
joints.
For
each
joint,
the
following
lesions
were
recorded:
Tarsocrural
Joint
Fragments
or
large
defects
of
the
intermediate
ridge
of
the
tibia
Fragmentation
of
the
lateral
troclear
ridge
of
the
talus
Fragmentation
of
the
medial
malleolus
Metacarpoltarso-phalangeal
Joint
Palmar/plantar
proximal
fragmentation
of
the
proximal
phalanx
Un-united
proximoplantar
eminence
of
the
proximal
phalanx
Osteochondrosis
(Type
I,
II,
and
111
18
)
of
the
sagittal
ridge,
lateral
or
medial
condyles
of
the
distal
metacarpus/tarsus
Dorsoproximal
fragmentation
of
the
proximal
phalanx
Apical
fragmentation
of
the
proximal
sesamoid
bones
The
racing
career
as
two-
and
three-year-old
was
evaluated
for
each
horse
when
the
last
generation
of
the
group
(horses
born
in
1992)
completed
the
third
year
of
life
and
data
were
obtained
by
the
Italian
Trotting
Association
(ENCAT).
The
following
pa-
rameters
were
examined
for
each
horse:
Number
of
starts
at
2
years
of
age
Number
of
wins
at
2
years
of
age
Number
of
placings
at
2
years
of
age
Earnings
at
2
years
of
age
Record
time
at
2
years
of
age
Number
of
starts
at
2
and
3
years
of
age
Number
of
wins
at
2
and
3
years
of
age
Number
of
placings
at
2
and
3
years
of
age
Earnings
at
2
and
3
years
of
age
Record
time
at
3
years
of
age
The
horses
were
divided
in
two
groups,
character-
ized
by
the
absence
of
lesions
(group
without
radio-
graphic
lesions)
or
by
the
presence
of
one
or
more
lesions
(group
with
radiographic
lesions).
The
racing
results
of
the
group
with
radiographic
lesions
were
compared
with
the
results
of
the
group
without
ra-
diographic
lesions.
No
clinical
information
was
available
for
the
horses
and
some
of
the
horses
with
lesions
were
likely
to
have
been
treated
surgically.
In
order
to
define
a
possible
prognostic
score
for
each
lesion,
racing
results
of
horses
characterized
by
the
presence
of
the
same
lesion
were
evaluated
and
com-
pared
with
the
results
of
the
total
group
and
the
group
without
radiographic
lesions.
3.
Results
The
total
group
of
three
generations
examined
com-
prised
764
yearlings
(410
males,
354
females).
In
186
yearlings
(24%),
one
or
more
joints
with
radio-
graphic
lesions
were
recorded,
whereas
578
year-
lings
had
no
radiographic
lesions.
In
60
yearlings
(8%),
two
joints
with
radiographic
lesions
were
re-
corded;
in
4
(0.5%),
three
joints
with
lesions;
and
in
only
one
case
four
joints
with
lesions
were
identified.
Lesions
were
found
in
117
tarsocrural
joints,
and
in
110
fetlock
joints.
The
total
number
of
joints
with
lesions
was
227.
The
histogram
in
Figure
1
sum-
marizes
the
location
of
different
lesions.
Lesions
were
classified
according
to
their
type
and
location
and
each
lesion
was
identified
with
a
number
(1
to
20,
see
legend
in
Fig.
1).
In
the
tarsocrural
joint
(Table
1),
the
lesions
had
the
following
locations:
Intermediate
ridge
of
the
tibia:
100
joints
(54
on
the
right,
and
46
on
the
left)
Lateral
troclear
ridge
of
the
talus:
9
joints
(6
on
the
left,
and
3
on
the
right)
Medial
malleolus:
7
joints
(2
on
the
left
and
5
on
the
right)
Miscellaneous
lesions:
1
joint
The
dimensions
and
number
of
fragments
of
the
same
lesion
were
not
recorded.
More
lesions
were
identified
in
the
left
tarsocrural
joint
than
the
right,
but
the
difference
was
not
significant.
In
the
fetlock
joint
(Table
2),
the
lesions
were
distributed
as
follows:
Plantar
fragmentation
of
proximal
PI:
26
hind
limbs
(13
on
the
left
and
13
on
the
right)
Dorsodistal
OCD
of
the
metacarpus:
29
front
limbs
(14
on
the
left
and
15
on
the
right)
Dorsodistal
OCD
of
the
metatarsus:
33
hind
limbs
(18
on
the
left
and
15
on
the
right)
Dorsoproximal
fragmentation
of
the
proximal
phalanx:
24
front
limbs
(13
on
the
left
and
11
on
the
right)
and
11
hind
limbs
(7
on
the
left
and
4
on
the
right)
Un-united
lateral
eminence
of
the
proximal
phalanx:
2
left
hind
limbs
Apical
fragmentation
of
proximal
sesamoid
bones:
7
cases
in
5
horses
(in
2
cases
the
frag-
mentation
involved
both
sesamoids
in
the
same
fetlock)
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1
-1
TIMELY
TOPICS
50
4
46
7
8
9
10
11
12
13
14
15
16
17
18
19
20
Type
of
lesion
Fig.
1.
Lesion
distribution
histogram.
The
histogram
summarizes
the
incidence
of
each
type
of
lesions
recorded.
Each
number
refers
to
a
different
lesion
or
location.
1
=
OCD
left
intermediate
ridge
of
the
tibia.
2
=
OCD
right
intermediate
ridge
of
the
tibia.
3
=
OCD
left
lateral
troclear
ridge
of
the talus.
4
=
OCD
right
lateral
troclear
ridge
of
the talus.
5
=
fragmentation
of
the
left
medial
malleolus.
6
=
fragmentation
of
the
right
medial
malleolus.
7
=
left
proximal
plantar
P1
fragmentation.
8
=
right
proximal
plantar
P1
fragmentation.
9
=
dorsodistal
OCD
of
the
left
metacarpus.
10
=
dorsodistal
OCD
of
the
right
metacarpus.
11
=
dorsodistal
OCD
of
the
left
metatarsus.
12
=
dorsodistal
OCD
of
the
right
metatarsus.
13
=
left
front
dorsoproximal
fragmentation
of
Pl.
14
=
right
front
dorsoproximal
fragmentation
of
Pl.
15
=
left
hind
dorsoproximal
fragmentation
of
Pl.
16
=
right
hind
dorsoproximal
fragmentation
of
Pl.
17
=
miscellaneous
lesions.
18
=
left
hind
un-united
lateral
eminence
of
Pl.
19
=
right
hind
un-united
lateral
eminence
of
Pl.
20
=
apical
fragmentation
of
the
proximal
sesamoid
bone.
Miscellaneous
lesions
(irregular
defects
of
the
Due
to
different
combinations
of
lesions
within
the
dorsal
contour
of
the
sagittal
ridge
of
the
distal
same
joint,
a
total
of
134
lesions
resulted
distributed
metacarpus):
2
cases
in
110
fetlock
joints.
In
Table
3,
results
referring
to
the
10
parameters
examined
are
summarized
for
each
group.
Average
data
for
each
parameter
are
shown.
The
graphic
Table
1.
Distribution
of
Lesions
in
the
Tarsocrural
Joint
representation
of
the
data
was
characterized
by
the
Lat.
following
patterns:
Troclear
Intermediate
Ridge
Medial
Earnings
were
correlated
with
the
number
of
Ridge
Tibia Tibia
Malleolus
Miscellaneous
TOTAL
wins
100
9
7
1
117
Placings
were
correlated
with
the
number
of
starts
Table
2.
Distribution
of
Lesions
in
the
Fetlock
Joint
Plantar
Un-united
Apical
Fragmentation
OCD OCD
Dorsoproximal
PI
lateral
sesamoid
PI
Metacarpus
Metatarsus
PI
fragment
eminence
fracture
Miscellaneous
TOTAL
26
29
33
35
2
7
2
134
40
20
10
1u
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Wins
as
2-
an
d
3-y
ear
o
ld
e
TIMELY
TOPICS
Table
3.
Summary
of
average
values
for
different
parameters
referring
to
the
racing
careers
of
the
total
group
of
yearlings,
the
group
with
radiographic
lesions,
and
the
group
without
radiographic
lesions
Group
S2y.o
S2&3y.o
W2y.o
W2&3y.o
P2y.o
P2&3y.o
T2y.o*
T2&3y.o*
ML2y.o
ML2&3y.o
Total
group
Without
radiographic
lesions
5,82
5,77
17,13
16,91
2,10
2,04
3,87
3,69
3,06
3,04
7,30
7,27
01.19,4
01.19,5
01.18,1
01.18,1
6.693
6.366
30.088
27.282
With
radiographic
lesions
5,96
17,76
2,29
4,37
3,12
7,38
01.19,2
01.18,1
7.708
38.811
*In
Italy,
we
do
not
use
the
time
referred
to
the
mile,
but
the
average
time
per
kilometer.
So
1.
18,
1,
for
example,
means
that
the
average
speed
during
the
race
was
1
minute,
18
seconds
and
1
tenth/kilometer.
S2y.o
Starts
as
2-year
old
S2&3y.o
Starts
as
2-
and
3-year
old
W2y.o
Wins
as
2-year
old
W2&3y.o
Wins
as
2-
and
3-year
old
P2y.o
Placings
as
2-year
old
P2&3y.o
Placings
as
2-
and
3-year
old
T2y.o
Record
time
as
2-year
old
T2&3y.o
Record
time
as
2-
and
3-year
old
ML2y.o
Earnings
(million
Lires)
as
2-year
old
ML2&3y.o
Earnings
(million
Lires)
as
2-
and
3-year
old
Record
time
was
an
independent
observation
that
did
not
correlate
with
other
data
Figures
2
and
3
respectively
show
the
correlation
between
number
of
starts
and
placings
(good)
and
between
number
of
starts
and
wins
(poor).
The
group
with
radiographic
lesions
was
charac-
terized
by
better
performances
when
compared
to
the
group
with
no
radiographic
lesions.
The
number
of
starts
as
2-
and
3-year-olds
in
the
group
with
radiographic
lesions
(5.96
and
17.76,
respectively)
was
higher
than
the
group
without
radiographic
Regression
of
Placings
on
Starts
for
2-3
year
old
horses
lesions
(5.77
and
16.91).
The
differences
increased
when
the
number
of
wins
was
examined,
especially
in
3-year-old
horses:
in
the
total
group,
the
average
number
of
wins
was
3.87,
in
the
group
without
ra-
diographic
lesions
3.69,
but
in
the
group
with
radio-
graphic
lesions
the
average
number
of
wins
at
completion
of
the
3-year-old
racing
career
was
4.37,
and
this
was
significant.
As
previously
noticed,
a
correlation
was
observed
between
the
number
of
wins
and
earnings.
The
av-
erage
earnings
of
2-year-olds
in
the
total
group
were
6.693
million
lire;
the
group
without
radiographic
lesions
had
a
lower
value
(L.
6.366
million)
and
the
group
with
radiographic
lesions
averaged
L.
7.708
million.
More
differences
were
observed
when
40
Regression
of
Wins
on
Starts,
as
2-and
3-year
old
Pla
c
ing
s
as
2-
an
d
3-y
ea
r
o
ld
15
30
12
••w
20
••
MD
10
•• ••••••• ••
0
20
40
60
80
100
120
10
20
30
40
50
60
Starts
as
2-
and
3-year
old
IND
0
Fig.
2.
Relationship
between
number
of
starts
and
placings
as
2-
and
3-year-old.
Each
horse
is
represented
by
a
spot,
and
their
distribution
in
a
narrow
area
suggests
good
correlation
between
the
two
parameters.
Starts
as
2-
and
3
year
old
Fig.
3.
Relationship
between
number
of
starts
and
wins
as
2-
and
3-year-old.
The
distribution
of
spots
in
a
large
area
suggests
poor
correlation
between
the
two
parameters.
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earnings
as
3-year-old
were
considered.
In
the
to-
tal
group,
the
average
was
L.
30.088
million;
the
group
without
radiographic
lesions
averaged
L.
27.282
million
whereas
the
group
with
radiographic
lesions
reached
L.
38.811
million.
The
differences
were
less
when
other
parameters
were
considered
(number
of
placings
and
record
times),
but
with
the
same
trend
of
the
group
with
radiographic
lesions
to
show
better
results
than
the
group
without
radio-
graphic
lesions.
The
incidence
of
each
type
of
lesion
and
its
possi-
ble
influence
on
the
racing
career
were
further
eval-
uated,
in
order
to
identify
prognostic
indicators.
Lesions
affecting
the
tarsocrural
joint
were
con-
sidered
as
a
single
group,
because
most
cases
were
OCD
of
the
intermediate
ridge
of
the
tibia.
The
number
of
wins
and
earnings
as
3-year-old
(5.15
and
37.641
million,
respectively)
of
horses
affected
by
tarsocrural
OCD
were
less
but
similar
in
compari-
son
with
the
corresponding
values
of
the
full
group
with
radiographic
lesions.
Data
referring
to
yearlings
affected
by
fetlock
le-
sions
(with
the
exclusion
of
apical
fragmentation
of
the
proximal
sesamoid
bone)
showed
higher
earn-
ings
as
2-year-olds
(L.
10.239
million)
and
as
3-year-
olds
(L.
42.348
million)
when
compared
with
the
total
group,
with
the
group
without
radiographic
lesions,
and
with
the
group
with
radiographic
le-
sions.
The
group
of
horses
with
osteochondrosis
of
the
sagittal
ridge
or
condyles
of
the
metacarpus/
tarsus
had
poorer
racing
results
in
comparison
with
the
average
results
of
the
group
without
radio-
graphic
lesions.
Despite
higher
number
of
starts
(18.45
as
3-year-olds),
with
corresponding
increase
in
placings,
wins
were
2.11
as
2-year-olds
and
3.41
as
3-year-olds
and
earnings
were
L.
4.801
million
as
2-year-olds
and
24.049
as
3-year-olds.
In
the
case
of
plantar
fragments
from
proximal
PI,
there
was
slight
increase
in
wins
(4.42)
in
comparison
with
other
groups,
and
very
significant
rise
in
earnings
as
3-year-olds:
L.
58.121
million.
The
latter
result
suggests
the
possible
presence
of
one
or
more
excel-
lent
performers
in
this
relatively
small
group.
In
horses
with
dorsoproximal
fragmentation
of
PI,
average
earnings
of
16.463
as
2-year-olds
and
65.209
as
3-year-olds
were
recorded,
suggesting
minimal
influence
of
this
lesion
on
the
athletic
fu-
ture.
Finally,
although
rare,
the
presence
of
apical
fragmentation
of
the
proximal
sesamoid
bones
was
associated
with
the
poorest
results.
The
5
cases
in
which
the
lesion
was
observed
(2
involving
both
sesamoids
in
the
same
fetlock),
had
average
2.5
wins
at
3
years
of
age
and
earnings
of
L.
3.968
and
9.450
million
at
2
and
3
years
of
age,
respectively.
4.
Discussion
The
group
of
yearlings
examined
in
the
present
study
can
be
considered
representative
of
the
Italian
Standardbred
population
due
to
the
large
number
of
horses:
each
generation
was
represented
by
nearly
8%
of
the
Standardbreds
born
in
the
corresponding
year.
Standardbred
trotters
are
the
most
widely
inves-
tigated
breed
for
OCD.
3
Hoppe
7
examined
a
large
group
of
Standardbreds
and
Swedish
Warmblood
horses
affected
by
tarsocrural
OCD
and
lesions
were
found
in
166
out
of
212
joints
of
Standardbreds.
Alvarado
et
al.
9
examined
a
mixed
group
of
stallions,
mares,
and
two
generations
of
yearlings
on
the
same
Standardbred
farm.
Several
radiographic
features
were
considered
significant
in
that
study
and
this
produced
a
large
percentage
of
radiographic
findings
considered
pathologic:
25%
of
horses
were
affected.
Yearlings
affected
by
OCD
accounted
for
31.5%.
During
the
following
twelve
years
since
Hoppe's
study,
several
surveys
on
equine
OCD
have
been
published.
The
introduction
of
arthroscopy
has
im-
proved
knowledge
of
the
incidence
of
OCD.
Im-
proved
prognosis
after
surgical
treatment
of
selected
lesions
2,26
has
possibly
influenced
long
term
results
in
terms
of
athletic
performance
in
this
study.
The
methods
employed
to
evaluate
the
racing
ca-
reer
referred
to
10
performance
parameters,
this
allowed
identification
of
the
most
significant
and
well-correlated
data.
Earnings
and
wins
were
well
correlated,
whereas
number
of
starts
(which
has
been
frequently
considered
the
main
parameter
in
similar
studies)
mostly
correlated
with
number
of
placings,
and
the
latter
is
a
poor
indicator
of
the
racing
career.
Record
times
had
independent
vari-
ations.
An
easy
conclusion
from
those
data
was
that
by
increasing
the
number
of
races
one
can
in-
fluence
the
number
of
placings,
but
not
the
number
of
wins
nor
earnings.
The
latter
two
parameters
presumably
represent
a
figure
of
the
intrinsic
qual-
ity
of
the
race
horse.
The
incidence
of
tarsocrural
and
fetlock
lesions
was
similar
to
that
reported
in
previous
literature.
When
results
of
horses
affected
by
different
types
of
lesions
were
evaluated,
differences
for
previous
re-
ports
became
evident
overall.
The
group
with
radiographic
lesions
had
better
results
when
com-
pared
with
the
total
group
and
with
the
group
with-
out
radiographic
lesions.
This
trend
was
confirmed
by
all
10
parameters,
especially
wins
and
earnings.
It
is
not
easy
to
explain
these
results.
Horses
had
not
been
clinically
evaluated,
and
subsequent
med-
ical
or
surgical
treatment
were
not
known.
It
can
be
speculated
that
improvements
in
both
diagnostic
and
surgical
techniques
allowed
trainers
and
veter-
inarians
to
identify
and
treat
lesions,
mostly
by
ar-
throscopic
surgery.
It
can
also
be
hypothesized
that
the
presence
of
(or
predisposition
to
develop)
some
lesions
is
genetically
linked
to
a
good
athletic
genetic
capacity.
Alternatively,
stallions
and
mares
could
transmit
inferior
genetic
quality
but
not
OCD
or
predisposition
to
develop
lesions.
A
similar
hypothesis
was
proposed
by
Storgaard
Jorgensen
et
al.,
31
in
order
to
explain
results
similar
to
ours
ob-
tained
by
horses
affected
and
non-affected
by
OCD.
AAEP
PROCEEDINGS
/
Vol.
46
/
2000
291
TIMELY
TOPICS
No
clinical
signs
were
recorded
in
the
latter
study,
similar
to
our
study.
Alvarado
et
al.
9
reported
similar
groups
to
ours.
In
the
population
of
Standardbreds
they
examined,
32.7%
of
lesions
were
classified
as
OCD
of
the
fet-
lock,
43.7%
of
lesions
involving
the
dorsodistal
metacarpus/tarsus,
43.7%
the
palmaro/plantaro-
proximal
PI,
and
12.5%
dorsoproximal
PI.
Yearlings
affected
by
OCD
and
subchondral
bone
cysts
had
a
number
of
starts
slightly
lower
when
compared
to
the
normal
group,
but
a
significant
rise
in
average
earnings
($4.78
US
versus
$2.99
US).
Another
study
3
investigated
three
groups
of
horses
affected
by
different
types
of
fetlock
lesions
in
comparison
with
a
normal
group.
Horses
affected
by
fetlock
lesions
had
a
significantly
lower
number
of
starts
when
compared
with
the
group
of
unaffected
horses,
but
little
differences
in
earnings.
More
recently,
Storgaard
Jorgensen
et
al.
31
compared
radiographic
findings
of
a
large
group
of
Standardbreds
with
sub-
sequent
racing
performance
and
longevity.
These
authors
found
no
significant
association
between
ra-
diographic
abnormalities
and
performance.
No
statistical
significance
was
found
in
differences
be-
tween
starts
and
earnings
of
normal
and
affected
horses.
Horses
with
multiple
lesions
had
lower
earnings,
but
this
was
not
statistically
significant.
This
study
did
not
provide
information
about
treat-
ment
of
horses
affected
by
OCD,
and
it
was
hypoth-
esized
that
15%
of
horses
may
have
been
surgically
treated.
Similarly,
a
radiographic
survey
per-
formed
on
German
Standardbreds
33
showed
a
12.4%
prevalence
of
tarsocrural
OCD.
No
significant
dif-
ferences
were
found
in
number
of
starts,
wins,
plac-
ings,
or
earnings
between
affected
and
non-affected
horses.
33
The
latter
study
referred
to
a
group
of
horses
examined
between
1970
and
1985,
mostly
before
the
advent
and
spread
of
equine
arthroscopy.
A
lower
morbidity
of
equine
tarsocrural
OCD
has
to
be
expected
after
preventative
and
curative
arthro-
scopy
has
become
routine
practice.
Lesions
affecting
the
tarsocrural
joint
were
not
differentiated
between
different
locations
when
the
racing
career
was
evaluated.
As
anticipated,
OCD
of
the
intermediate
ridge
of
the
tibia
was
widely
prev-
alent.
A
more
detailed
study
will
be
useful
in
the
future,
because
lesions
affecting
the
lateral
troclear
ridge
of
the
talus
as
well
as
the
medial
malleolus
have
been
observed
to
carry
a
poorer
prognosis
for
resolution
of
joint
effusion,
26
and
poor
correlation
has
been
demonstrated
between
radiographic
and
arthroscopic
findings
on
the
medial
malleolus.
34
In
a
previous
survey,
13
tarsocrural
OCD
was
ob-
served
in
11.5%
of
a
group
of
Standardbred
year-
lings,
with
95%
of
lesions
located
in
the
intermediate
ridge
of
the
tibia.
Horses
with
radiographic
lesions
in
the
tarsocru-
ral
joint
performed
well
in
terms
of
wins
and
earn-
ings
as
2-
and
3-year-olds.
Unlike
the
fetlock,
the
tarsocrural
joint
frequently
shows
effusion
and,
more
rarely,
lameness
in
early
stages
of
training;
because
of
that
it
is
the
most
frequent
joint
subjected
to
preventative
arthroscopic
surgery.
This
may
ex-
plain
the
good
results
of
affected
horses
as
2-year-
olds
in
the
present
report.
In
a
retrospective
study,
22
racing
performance
of
114
Standardbreds
treated
for
osteochondrosis
of
the
intermediate
ridge
of
the
tibia
was
compared
with
racing
performance
of
456
healthy
control
horses.
Fifty-eight
of
the
114
horses
had
been
treated
surgically
and
56
had
con-
servative
treatment.
Horses
affected
by
bilateral
OCD
were
twice
as
likely
to
have
arthroscopic
sur-
gery.
The
114
affected
horses
had
significantly
fewer
starts
than
control
horses,
but
earnings
of
the
two
groups
of
horses
were
similar.
Based
on
previ-
ous
considerations,
one
can
argue
that
earnings
tend
to
change
independently
of
the
presence
of
tibiotar-
sal
OCD
in
Standardbred
racehorses.
A
recent
study
investigated
morbidity
of
osteo-
chondrosis
of
the
tarsocrural
joint
in
Standardbreds,
and
the
incidence
was
14.3%.
16
Early
studies
on
horses
receiving
conservative
treatment
for
OCD
of
the
tarsocrural
joint
suggested
that
a
poor
prognosis
should
be
given
for
racing
soundness,
35
'
36
and
neg-
ative
influence
of
OCD
on
performance
of
trotters
was
confirmed
by
Hoppe
and
Philipsson.
37
A
more
recent
study
showed
acceptable
results
with
conser-
vative
treatment
of
tarsocrural
OCD
in
Warmbloods
but
not
in
Standardbreds.
38
The
advent
of
arthro-
scopy
was
associated
with
significant
improvement
of
prognosis
after
surgical
treatment
of
selected
OCD
lesions.
A
study
performed
on
a
large
group
of
horses
operated
for
OCD
of
the
tarsocrural
joint
showed
excellent
results,
with
76.5%
of
horses
able
to
race
successfully.
26
The
latter
study
showed
dif-
ferent
prognosis
for
selected
lesions,
with
poorer
results
associated
with
OCD
of
the
lateral
troclear
ridge
of
the
talus.
When
horses
affected
by
fetlock
lesions
were
con-
sidered
as
one
group
(with
the
exception
of
cases
with
apical
fragmentation
of
proximal
sesamoid
bones),
earnings
and
wins
were
the
highest
observed
in
the
study.
It
must
be
observed
that
the
clinical
significance
of
some
lesions
of
the
fetlock
in
Stan-
dardbreds
has
been
questioned.
32
'
39
Because
of
dif-
ferent
aetiopathogenesis
of
fetlock
lesions,
a
detailed
analysis
of
results
of
horses
affected
by
each
type
of
radiographic
pattern
was
performed.
Osteochondrosis
of
the
sagittal
ridge
and
condyles
of
the
distal
metacarpus/tarsus
is
characterized
by
the
presence
of
one
or
more
fragments
or
defects
on
the
dorsodistal
metacarpus/tarsus
and
can
be
asso-
ciated
with
joint
effusion,
pain
elicited
by
flexion
and
lameness
under
race
training.
18,30,4o
Osteochondro-
sis
of
the
sagittal
ridge
or
condyles
of
the
distal
metacarpus/tarsus
has
been
reported
to
mostly
af-
fect
the
hind
limb
(10%
versus
4.3%
in
the
fore
limb),
11
with
tendency
of
affected
horses
to
have
lesions
in
multiple
limbs.
In
the
present
study,
horses
affected
by
OCD
of
the
sagittal
ridge
or
con-
dyles
of
the
metacarpus/metatarsus
had
poorer
rac-
ing
results
in
comparison
with
control
groups
(total
292
2000
/
Vol.
46
/
AAEP
PROCEEDINGS
TIMELY
TOPICS
group,
group
without
radiographic
lesions,
and
group
with
radiographic
lesions).
Interestingly,
this
group
of
horses
was
able
to
race
more
frequently
than
others
and
this
possibly
means
that
dorsodistal
OCD
of
the
metacarpus/metatarsus
allows
some
ac-
ceptable
level
of
race
training,
but
prevents
good
results.
The
prognosis
after
surgical
treatment
of
OCD
of
distal
metacarpus/metatarsus
has
been
re-
ported
as
fair
to
good:
11
Plantar
fragmentation
of
proximal
PI
had
lower
incidence
compared
to
that
reported
in
previous
studies,8
,10,13
probably
because
the
appropriate
ra-
diographic
views
(dorsoproximal
lateral-plantaro
distal
medial
oblique
and
dorsoproximal
medial-
plantaro
distal
lateral
oblique)
were
not
routinely
performed.
Sandgren
et
al.
13
examined
a
group
of
Standardbred
yearlings
similar
to
the
group
re-
ported
here,
and
found
a
22.4%
incidence
of
palmar/
plantar
fragmentation
of
proximal
PI.
In
the
present
study,
all
fragments
from
proximal
plantar
PI
were
found
in
hind
limbs
and
mostly
medially,
according
to
previous
reports.
8,13
Proximoplantar
fragments
from
PI
have
been
described
as
develop-
mental
lesions
by
some
authors,
11
-
2642
but
previ-
ous
43
'
14
and
recent
6
studies
confirmed
the
traumatic
origin,
probably
by
early
avulsion
of
tissue
with
osteogenic
properties.
5
Yearlings
affected
by
plan-
tar
fragmentation
of
proximal
PI
in
the
present
study
had
high
earnings
and
number
of
wins.
Prognosis
after
surgical
treatment
of
this
lesion
has
been
re-
ported
as
good
2646
and
arthroscopy
led
to
further
im-
provement
during
the
past
10
years.
Dorsoproximal
fragmentation
of
PI
was
character-
ized
by
the
best
results
in
terms
of
wins
and
earn-
ings
as
2-
and
3-year-olds
of
affected
horses
when
compared
with
results
of
horses
affected
by
other
lesions.
A
study
performed
on
a
large
group
of
horses
submitted
to
arthroscopic
surgery
for
dorsoproximal
fragmentation
of
PI
resulted
in
73%
of
patients
(mostly
race
horses)
able
to
return
to
the
previous
use
and
73.6%
of
these
returned
to
the
same
level
of
performance.
46
Un-united
lateral
eminence
of
proximal
PI
in
the
hind
limb
had
incidence
similar
to
that
reported
by
Grondah1
12
and
no
specific
investigation
was
per-
formed
on
racing
performance,
owing
to
the
small
number
of
horses
involved.
Apical
fragmentation
of
proximal
sesamoid
bones
involved
5
horses
(2
with
fractures
of
both
lateral
and
medial
sesamoid
bones
of
the
same
fetlock)
and
was
associated
with
poor
racing
results.
Apical
frac-
ture
of
proximal
sesamoid
bones
selectively
affect
young
horses
in
training
and
racing
47
and
surgical
treatment
is
associated
with
good
to
fair
prognosis:
18
The
chronic
condition
may
have
negatively
influ-
enced
the
athletic
future
of
affected
horses,
espe-
cially
when
fractures
involved
both
sesamoids
of
the
same
joint.
In
conclusion,
this
study
confirms
the
incidence
of
tarsocrural
OCD
and
intra-articular
bony
fragments
in
metacarpo/tarso-phalangeal
joints
similar
to
pre-
vious
radiographic
surveys
on
Standardbreds.
The
analysis
of
the
juvenile
(2-
and
3-year-old)
racing
career
suggests
no
significant
influence
of
most
of
the
lesions
affecting
the
tarsocrural
joint
on
the
athletic
performance.
Selected
lesions
of
the
meta-
carpo/tarso-phalangeal
joint
may
negatively
affect
the
athletic
performance.
Further
studies
are
needed
in
order
to
better
assess
the
clinical
rele-
vance
of
each
lesion
and
the
possible
genetic
links
between
conformation,
presence
of
OCD,
and
ath-
letic
attitude.
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