THE SIGNIFICANCE OF THE POSTERIOR CRUCIATE LIGAMENT

THE
SIGNIFICANCE
OF THE POSTERIOR
CRUCIATE
THE STABILITY
OF THE KNEE
IN
AN
EXPERIMENTAL
J. POURNARAS,
From
the Department
ofOrthopaedics
STUDY
IN
P. P. SYMEONIDES,
and the First
LIGAMENT
DOGS
G. KARKAVELAS
Surgical
Department,
Aristotelian
University
of Thessaloniki
The significance
of the posterior
cruciate ligament in the stability of the knee was investigated
in dogs
and it was compared with that of the anterior cruciate ligament by studying the changes produced in the knee
after transection
of either ligament.
Osteophyte
formation
and changes
in articular
cartilage
were less
prominent
after division of the posterior
cruciate
ligament.
A complete
longitudinal
tear of the medial
meniscus was found in eight out of the 10 dogs who had undergone
section of the anterior cruciate but in none
of the 10 with section of the posterior cruciate. It appears that, in dogs at least, the posterior cruciate ligament
is less important
than the anterior in the stability of the knee.
Although
ligament
the number
ofruptures
ofthe posterior
cruciate
is progressively
increasing,
the significance
of
this ligament
in the stability
clarified.
Until
a few years
of the knee has not yet been
ago clinical
and experimental
research
was focused
on the anterior
cruciate
ligament,
but recently
the posterior
cruciate
ligament
has become
the subject
of interest.
Hughston
et al. (1976,
1980)
considered
the posterior
cruciate
ligament
as the main
stabiliser.
By contrast,
Dandy
and
Pusey
(1982)
reported
after a mean follow-up
of 7.2 years that many patients
with unrepaired
tears of the posterior
cruciate
ligament
had maintained
good function.
In our experimental
work the role of the posterior
cruciate
ligament
in
the
stability
of
the
ligament
is nearly
always
accompanied
by coincident
damage
to the capsule
or other ligaments.
While
animal
experiments
concerning
the significance ofthe anterior
cruciate
ligament
have been carried
out by various
authors
(Marshall
1969; Marshall
and
Olsson
1971) such an investigation
on the posterior
cruciate
does not appear
to have been reported
as yet in
the English
literature.
knee
was
investigated
in dogs and it was compared
to the role of
the anterior
cruciate.
This was done by studying
the joint
changes
which were progressively
produced
after section
of the posterior
or anterior
cruciate
ligament,
since it has
been proved
that there is a direct relationship
between
the amount
of the change
and the degree
of instability
(Marshall
and Olsson
1971 ; O’Donoghue
et al. 1971).
Dogs were chosen
as the experimental
animals
because
their knees and cruciate
ligaments
are similar to those of
man anatomically
and functionally.
In addition,
the role
ofthe posterior
cruciate
ligamentperse
cannot be studied
in man
because
in clinical
practice
rupture
of this
MATERIAL
Twenty-one
adult
Skeletal
divided
into
shape:
while
of each
the
other
Assistant
8, Thessaloniki,
Professor
ofOrthopaedic
Greece.
Surgery
Requests
©
for reprints
1983 British
Editorial
0301 -620X/83/2038-0204
204
should
be sent
Society
$2.00
to Dr J. Pournaras.
of Bone
and
Joint
each
the
the
anaesthesia
of either
arthrotomy
the
curved
knife.
other
structures
the
patella
ligament
sign
became
of the
joint
in
immobilised.
arthrotomy
only
intact
to serve
dogs
they
wound
were
could
housed
and
weekly
dogs
were
killed
months,
and
ligament.
The
dog
jump.
(one
14 (seven
out
The
The
parapatellar
side.
With
by closure
The
left
or
or anterior
completed
for the
by a
cartilage
posterior
skin).
in
under
sodium.
articular
was
followed
performed.
in an
healing
dogs
carried
of its length
the
and
In one
and
leg
was
sham
knee
not
operation
of all
animals
as a control.
and
: two
measuring
were
150 square
clinically
checked
metres
daily
so
until
thereafter.
by an overdose
pair)
pairs)
with
area
They
at four
of intravenous
months,
at six months
a sham
four
after
pentobarbital
(two
section
operation
was
killed
range
of movement
pairs)
of the
at five
cruciate
six months
after
operation.
Surgery
Immediately
of
was
knee.
sectioned
opposite
the
operation
was
right
middle
section,
(capsule
procedure
run
sodium
the
same
operation.
a medial
to the
at the
the
The
layers
body
was
to damage
After
and
through
cut
not
positive.
two
The
remained
taken
of the joint.
drawer
where
was
weight
was
dislocated
was
sex,
pentobarbital
performed
was
were
on the
by intravenous
by
dogs
ligament
procedure
used.
The
for a sham
performed
The
was
the
Care
selected
were
established
knees.
of the same
cruciate
cruciate.
were
of both
was
was
posterior
induced
flexed
14 to 20 kilograms
deformities
being
dog
cruciate
and
knee
pair
procedure
the
anterior
section
of
radiographs
twenty-first
pair
general
The
P. P. Symeonides,
MD, Professor
of Orthopaedic
Surgery
G. Karkavelas,
MD,
Pathologist
Aristotelian
University
of Thessaloniki,
Thessaloniki,
Greece.
10 pairs,
the
All
MD,
lateral
METHODS
weighing
absence
and
In all dogs
dog
dogs
and
anteroposterior
that
J. Pournaras,
P. P. Germanou
mongrel
maturity
AND
the
knee
after
were
death
examined.
THE
the
The
JOURNAL
knee
joints
OF BONE
of
and
both
AND
legs
JOINT
the
stability
were
then
SURGERY
THE
SIGNIFICANCE
OF THE
POSTERIOR
CRUCIATE
LIGAMENT
IN THE
STABILITY
OF
Hg.
Femoral
(Fig.
removed,
blocks
and
articular
from
and
the
into
toxylin
the
acid.
sections
seven
and
bone
All
and
were
taken
tibial
1 and
specimens
The
of nitric
(Figs
specimens
micrometers
plateau
fixed
The
black
inspected.
for
area
patella
from
also
taken
were
in a 10 percent
in a 10 per
cent
were
embedded
in paraffin
wax,
stained
site
from
where
the
bone
blocks
were
taken
for histology.
solution
decalcified
and
the
2
Bone
were
thick,
indicates
205
KNEE
histological
and
2). Specimens
were
blocks
of a dog.
dissected
cartilage
condyles,
knees
These
2) condyles
carefully
femoral
left
formalin.
solution
cut
the
capsule.
of neutral
(Fig.
covering
from
right
tibial
radiographed,
with
examination
the
1) and
THE
with
haema-
eosin.
RESULTS
The dogs started
two to four days
uneventfully
bearing
weight
on the operated
after the operation.
The wound
in 1 8 of the
delaying
in skin
healing.
dogs
; in two
there
Haemarthrosis
was
limb
healed
a slight
occurred
in one
dog after division
of the posterior
cruciate
ligament
; this
was drained
by aspiration.
In none of the dogs was there
any evidence
of infection.
All dogs, except
the one which
had had the sham
operation,
limped
after operation.
The limp decreased
progressively
and
became
minimal
by
the
end
of
the
study.
The posterior
or anterior
drawer
sign could
be
demonstrated
during
the whole period
of study in all
knees
with
transected
posterior
or anterior
cruciate
ligaments
respectively.
In most of the dogs in whom the
anterior
cruciate
had been cut there was also a clicking
sound
which
was
elicited
during
flexion
toward
the
Radiograph
the anterior
of both
cruciate
lateral
knees
of a dog killed
six months
after
ligament.
An osteophyte
is clearly
femoral
condyle
of the right knee.
division
seen at
of
the
had atrophied
and only remnants
at the site of origin
were detected.
In eight out of the 10 dogs with sectioned
anterior
cruciate
ligaments
a complete
longitudinal
tear (bucket
handle)
of the medial
meniscus
was found (Fig. 4). In
most
of them
.--‘
end
the
meniscus
was
totally
-
disorganised.
:..
m-
of the study.
Radiographic
findings.
In three dogs killed six months
after section ofthe anterior
cruciateligament,
osteophytes
at the lateral femoral
condyle
(intercondylar
fossa) could
be demonstrated
in the anteroposterior
radiographs
(Fig.
3). In another,
killed four months
after division
of the
anterior
cruciate,
osteophytes
were visible
at the tibial
spine. No osteophytes
could be seen radiologically
in the
knees of the dogs which
had undergone
section
of the
posterior
cruciate
ligament
or the sham operation.
No
special
radiographs
taken.
Macroscopic
VOL.
65-B.
findings.
No.
2. MARCH
(for
example,
In both groups
1983
tunnel
views)
the severed
were
Fig.
A bucket-handle
ligament
tear in the
after anterior
4
medial
meniscus
cruciate
ligament
in a dog killed
section.
six months
A
206
J. POURNARAS,
P.
P. SYMEONIDES,
complete
longitudinal
tear of the medial
meniscus
was
found even in the dog killed four months
after section of
the anterior
cruciate.
In the other two animals,
superficial
breaks
of the medial
meniscus
were noticed,
and such
breaks
appeared
also in the lateral
meniscus
of three
dogs of the same group. In none of the dogs with section
of
the
posterior
cruciate
meniscus
encountered.
breaks
of the medial
another
such changes
well.
ligament
was
a tear
of
the
In only one were
superficial
meniscus
noticed
(Fig. 5) while in
were found in the control joint as
G.
KARKAVELAS
osteophyte
formation
was much
less striking.
Small
prominences
were seen in only five dogs at the intercondylar margin
of the medial
femoral
condyle
and were
considered
as osteophytes
only
after
histological
confirmation.
No gross changes
were noticed
in the control joints,
except
in one where the anterior
cruciate
ligament
had
completely
disappeared,
probably
due to an old injury,
and this was accompanied
by osteophytic
formation,
marked
changes
in the articular
cartilage
and a longitudinal tear of the posterior
horn of the medial
meniscus.
In the dog that had had the sham operation
both knees
were
macroscopically
normal.
It was evident
when comparing
the two dogs of each
pair that the macroscopic
changes
were much less severe
in the dog with section ofthe posterior
cruciate
ligament.
Histology.
Osteophytes
and changes
in the articular
cartilage
were the main histological
findings.
The
cruciate
In the
merged
into the
were
Superficial
breaks
on the medial
meniscus
of a dog killed
alter
posterior
cruciate
ligament
section.
Large
osteophytes
were
observed
in the
six
months
operated
knees of all dogs with section
of the anterior
cruciate
ligaments
even in that killed at four months.
There were
two
standard
locations
of osteophytes
in this
group.
The
first, seen in all 10 dogs, was at the intercondylar
margin
Of the lateral
femoral
condy!e
near the trochlea
where the
anterior
cruciate
enters the intercondylar
fossa (Fig. 6).
The second one, present
in eight dogs, was located at the
posterior
edge of the medial
tibial plateau
(Fig. 7). Here
the large osteophyte
produced
marked
increase
of the
anteroposterior
diameter
of the medial tibia! condyle.
In
the dogs
with section
of the posterior
cruciate
the
Figure
6
ligament.
Large
Figure
osteophyte
macroscopically
7 Osteophyte
tbrmation
osteophytes
in the
dogs
ligaments
were impressive
great majority
they were
with the pre-existing
bone
femoral
or tibial condyles
covered
with
fibrocartilage
with
severed
anterior
under the microscope.
large, had completely
and were incorporated
(Figs 8 and 9). They
and
their
trabeculae
had
a more irregular
arrangement
than the normal
bone.
Apart from the osteophytes
at the lateral femoral condyle
and the posterior
edge of the medial tibia! plateau
which
were macroscopically
evident,
histological
examination
in this group revealed
also osteophytes
at the tibia! spine
(five dogs),
the medial
and lateral
edges of the tibia!
plateau
(four dogs) and the medial femoral
condyle
(two
dogs). The osteophytes
in the dogs with section
of the
posterior
cruciate
ligament
were microscopically
small,
immature
and
without
(or
with
very
little)
continuity
with the pre-existing
bone (Fig.
10). The histological
examination
simply
confirmed
the presence
of osteophytes
at the medial
femoral
condyle
in five dogs and
revealed
a small osteophyte
at the tibia! spine in another.
No osteophytes
were discovered
in the control
joints
except the one with no anterior
cruciate
ligament.
seen at the lateral
femoral
condyle
of a dog killed five months
after
macroscopically
seen at the posterior
edge of the medial
tibial condyle
six months
after section
of the anterior
cruciate
ligament.
THE
JOURNAL
division
of the
OF BONE
of the anterior
cruciate
right knee of a dog killed
AND
JOINT
SURGERY
THE
SIGNIFICANCE
OF
Fig.
THE
POSTERIOR
CRUCIATE
LIGAMENT
IN THE
STABILITY
OF THE
8
Fig.
207
KNEE
9
Figure
8 - Histological
section
ofthe
femoral
condyles
ofa dog killed
five months
after division
ofthe
anterior
cruciate
ligament.
Large osteophyte
is protruding
in the intercondylar
groove.
It has already
established
complete
communication
with the pre-existing
bone (haematoxylin
and eosin,
x 3). Figure
9-Histological
section
of the medial
tibial
condyle
(posterior
edge) of a dog killed
six months
after section
of the anterior
cruciate
ligament.
Large
osteophyte
communicating
with the pre-existing
bone
is shown
(haematoxylin
and eosin,
x 3.7).
In the articular
cartilage,
two types of changes
were
taken
into account
and evaluated
: the morphological
features
and arrangement
of the chondrocytes
; and the
integrity
classified
of the
according
articular
surface.
Both
to McDevitt,
Gilbertson
types
and
were
Muir
(1977).
The chondrocytic
changes
were
seen at the
articular
cartilage
of the femur,
tibia and patella
and
were classified
into three grades : increased
cell density
(Figs
‘‘
I
..
k
Fig.
A small
months
complete
t
5\
-
1 1 and
12), occasional
cell
“doublets”,
and
clones
of two or more cells. The changes
in the articular
surface
were mainly seen at the tibial plateau,
towards
the tibial
10
osteophyte
at the medial
femoral
condyle
of a dog killed
six
after
section
of the posterior
cruciate
ligament.
There
is no
communication
with the preformed
bone (haematoxylin
and
eosin, x 12).
spine,
and
slight
roughening,
were
ening
and
fissures
classified
into
five grades
roughening
and
small
in the middle
zone,
and
: intact
surface,
clefts,
total
of the surface
layer (Figs 1 3 to 1 5). When comparing
two dogs ofeach
pair it was found that the changes
articular
damaged
cartilage
posterior
were
less severe
cruciate
ligament
rough-
disruption
the
in the
in the dog with
a
than
in the other.
-‘
#{182}
\
h:
:‘;.
Fig.
Figure
1 1 -Articular
roughening
of the
VOL.
65-B,
No.
: :
11
cartilage
from
the medial
tibial
condyle
articular
surface
and an increased
cell density.
2, MARCH
1983
Fig.
of
a dog
Figure
killed
12-The
six
months
after
posterior
control
joint
for comparison
12
cruciate
ligament
(haematoxylin
section.
There
is
and eosin,
x 44).
208
J. POURNARAS,
-
P.
.-.
;-,.
..,
.
P. SYMEONIDES,
.-
‘-
I?
...
KARKAVELAS
‘
:
‘
I
.
:a
t
.
.
.
#{149}‘.
:
.
:
...::
.:
.1,
‘.‘-
-
.i;:.
i
.
..
,..‘
.
I..
.
-
.
..
t
:
.‘
‘i:
. .
.
‘
“.
.
.‘
‘
‘I
G.
%j
. -
Fig.
Articular
Figure
cartilage
13-Roughening
However,
13
of the
Fig.
tibial condyles
of three
and small clefts.
Figure
the difference
as striking
as the
between
the
difference
dogs killed
six,
14-Roughening
two
groups
in osteophyte
four
was
cartilage
were noticed
four of which
belonged
the
anterior
No
were
seen
sham
operation.
In
cruciate
in the
all
knees
dogs
histologically
group.
a
of the
thickening
present
microscopic
dog
that
of
at
to
changes
underwent
the
at the operated
not
formation.
Slight
changes
in the articular
the control
joint of five dogs,
the
capsule
14
Fig. 15
and six months
respectively
after
and fissures.
Figure
15-Disruption
x 1 1).
was
osteophyte
posterior
instability.
recently
articular
cartilage
experimental
In eight
out
ligament
medial
meniscus
section
of
anterior
the
main
findings
in the
of
this
work.
cruciate
Meniscal
were
with
a complete
was
the
tears
of 10 dogs
found.
posterior
None
cruciate
in dogs
cruciate
section
after
ligament
of the anterior
tear of the
bucket-handle
of the
showed
experimental
have
been
(Marshall
and Olsson
1971 ; Gilbertson
et al. 1977). It has been also reported
dogs
such
division
reported
1975;
that
with
tears.
of the
by others
McDevitt
rupture
of the
anterior
cruciate
combined
with tears of the menisci
are
seen
in dogs
clinically
(Tirgari
and
Vaughan
1975).
Furthermore,
the coexistence
of an anterior
cruciate
rupture
with a longitudinal
tear of the medial
meniscus
is often
Weinberg
Dameron
view that
encountered
in men
(Palmer
1938;
Kennedy,
and Wilson
1974; Smillie
1978; McDaniel
and
1980).
This
experimental
work
confirms
the
in dogs at least it is the rupture
of the anterior
cruciate
which occurs first and the meniscal
result of this injury.
The tear of the medial meniscus
should
to the rotatory
instability,
duced
after section
of the
which
anterior
tear
is a late
be attributed
is progressively
cruciate
ligament.
proThe
medial
collateral
ligament,
in an effort to prevent
anterior
displacement
of the tibia,
then becomes
lax and subsequently
cannot
prevent
lateral
rotation
of the tibia,
as
has been
described
in man
(Fowler
1980).
That
suggested
man “does
osteoarthrosis”.
Meniscal
tear
rupture
to rotatory
(Hughston
untreated
predispose
after
in dogs
1969;
ofthe
instability
has been
et al. 1976). Trickey
that
not
Osteophytes
and changes
ligament.
and eosin,
rotatory
does not lead
human
knees
(Marshall
formation
anterior
cruciate
(haematoxylin
cruciate
ligament
does not produce
knee.
DISCUSSION
tears,
of the
surface
does not follow section of the posterior
probably
because
injury to this ligament
ligament
Meniscal
division
ofthe
posterior
to meniscal
injury
have
of
been
Marshall
in
(1980)
also
instability
in
tears
the
or to late
anterior
observed
and
cruciate
reported
cruciate
experimentally
Olsson
1971 ; Gilbertson
1975) and in clinical
practice
(Tirgari
and Vaughan
1975). They are attributed
to the instability
of the knee.
The mechanism
of their production
is as yet uncertain.
Probably
the repeated
brane
at its insertion
stretching
may lead
and
bone
therefore
initially
indirectly
to new
a mechanical
in a vascular
Osteophytes,
present
dogs
one
osteophytes
were
anterior
cruciate
Section
of
were
location,
with cut posterior
produced
than
did
formation.
This
means
that
factor exists resulting
directly
one (Gilbertson
1975).
which
in only
of the synovial
memto vascular
proliferation
small,
were
cruciate
immature,
discovered
ligaments.
or
and
in only
Large,
six
mature
noticed
in all dogs after division
of the
and were present
in many
locations.
the
posterior
less severe
section
of
cruciate
ligament
changes
in the articular
the anterior
ligament,
also
cartilage
though
the
difference
osteophytes.
relationship
was not so impressive
as it was
with
the
It was also noticed
that there
was no direct
between
these
changes
and the osteophyte
formation.
evaluation
It must
be
ofthe
articular
admitted,
cartilage
as in the case of the osteophytes.
From
the findings
of this
section
of
produced
knee
therefore
cruciate
the
posterior
minimal
than
did
and
section
study
cruciate
less
JOURNAL
it appears
ligament
pronounced
of the
anterior
be assumed
that
the
ligament
in the stability
THE
however,
that
the
changes
is not as easy
changes
cruciate.
role
of the
of the knee
OF BONE
AND
JOINT
in
that
dogs
in the
It may
posterior
in these
SURGERY
THE
animals
SIGNIFICANCE
is less important
ligament.
It seems
OF THE
than
very
POSTERIOR
that ofthe
likely
that
this
CRUCIATE
anterior
LIGAMENT
cruciate
is due
to the
fact
IN THE
that
division
very
little
STABILITY
OF
of the posterior
rotatory
THE
cruciate
instability
209
KNEE
ligament
produces
or none.
REFERENCES
Dandy
DJ,
Pusey
Fowler
PJ.
The
RJ.
The
long-term
classification
and
results
early
of unrepaired
diagnosis
tears
of knee
joint
of the
posterior
instability.
cruciate
Clin
Orthop
ligament.
1980:
J Bone
147:
Joint
Surg
[Br]
:92-4.
1 982 : 64-B
15-21.
Gilbertson
EM. Development
of periarticular
osteophytes
in experimentally
induced
osteoarthritis
in the dog : a study
using
microradiographic,
microangiographic
and fluorescent
bone-labelling
techniques.
Ann Rheum
Dis 1975:34:
12-25.
Hughston
JC, Andrews
JR, Gross
MJ,
Moschi
A. Classification
of knee
ligament
instabilities.
Part
I : the medial
compartment
and cruciate
ligaments.
J Bone Joint Surg [Am]
1976:58-A:
159-72.
Hughston
Surg
JC, Bowden
JA,
[Am]
1 980:62-A
Kennedy
JC,
McDaniel
Weinberg
WJ,
Andrews
: 438-50.
HW,
Dameron
Wilson
TB.
JL.
Periarticular
Marshall
JL,
Olsson
O’Donoghue
factors
GR, Jeter
long-term
I. On
the
injuries
to the
IS. Injuries
ofthe
kneejoint.
5th
Tirgari
M, Vaughan
Arthritis
ofthe
EL.
Injuries
VOL.
65-B,
No.
to the
2, MARCH
ligaments
posterior
1.
1983
and
ofthe
knee.
tears
model
and
ofthe
ed.
canine
cruciate
ligament.
anterior
ligament
ofosteoarthritis
formation
in the
knee
JW,
[Am]
Kenyon
1971
a clinical
London
and
Vet Rec
Diagnosis
and
ofthe
:7
Acta
York:
cruciate
ligament.
dog.
: results
J Bone
and
Clin
of operative
J Bone
study.
J Bone
and
reconstruction
Joint
Joint
biochemical
Orthop
in dogs.
R. Repair
study.
New
ligament
morphological
study
:53-A
cruciate
: a follow-up
: early
experimental
kneejoint:
stiflejoint.
posterior
of the
cruciate
A long-term
Edinburgh,
of the
function
anterior
GL, Johnson
W, Zeiders
results.
J Bone Joint Surg
Palmer
1980:147:76-8
Acute
anatomy
initiation
of the
Smillie
Trickey
The
LA.
H. An experimental
Instability
LC.
Norwood
ruptures
osteophytes:
S-E.
DH, Frank
influencing
AS.
Untreated
McDevitt
C, Gilbertson
E, Muir
1977:59-B:
24-35.
Marshall
JA,
treatment.
Surg
Surg
[Am]
[Am]
changes.
J Bone
Joint
1974:56-A
:223-35.
1980:62-A
: 696-705.
J Bone
Joint
Surg
[Br]
1969:62:37-47.
Joint
Surg
[Am]
of the
1971 :53-A
anterior
cruciate
: 156 1-70.
ligament
in dogs:
10-8.
Chir
Churchill
Scand
1938:81
Livingstone,
Suppl
53.
1978:214,
220.
1975:96:394-9.
treatment
ofearly
injuries
and
reconstruction
oflate
instability.
Clin
Orthop