THE
Studies
Evolution,
in its
HENRY
LAMINECTOMY
LAROCCA,
NEW
Characteristics,
ORLEANS,
the
the
Division
Re-exploration
often
reveals
binding
Division
of Orthopaedic
of Orthopaedic
of the
the formation
down
the
nerve
cauda
equina
organised
to the
body.
The only previous
study
and Ford
(1948),
who suggested
was derived
from the surgically
Because
perineural
Surgery,
the
after
after
surface
the
fibrous
of the
operation
overlying
have
studied
the
diminishing
represented
erector
and
spinae
the nerve
development
Simple
of
lumbar
laminectomy
roots
the
weeks
and
twelve
and was in contact
with
surrounded
the posterior
under
the intact
neural
weeks
VOL.
in
56B,
for
surrounding
of the
disc
pose
of the muscle
scar
an
and
Ontario
removal
the dura
and
the
of a disc
and,
at times,
adjacent
vertebral
was carried
out
after disc excision
important
clinical
by Key
in dogs
problem,
we
into
and
fibroblastic
the
to the posterior
through
tissue
A-The
extends
and lateral
the surgical
have
activity
B-The
haematoma.
seen
at
dense
surfaces
of the dura
devise
a method
defect.
attempted
to
of
January
NO.
carried
out
AND
in eighteen
RESULTS
dogs.
At
as far laterally
as the intervertebral
were killed
at three days,
one week,
after
the
fifth
segment
the
foramen,
were scarified
three
weeks,
six weeks,
operation.
preparations
disclosed
a consistent
and sequential
pattern
of
day a haematoma
completely
filled the laminectomy
defect
the surface
layers ofthe
erector
spinae
muscles
(Fig. 2). The haematoma
and lateral
surfaces
of the dura and extended
for a variable
distance
arches
above
and below
the level of the surgical
defect.
on a paper read at the annual
Based
mass
extends
Orleans,
1
METHOD
was
A study
of the histological
response
(Fig.
1). At the third
*
New
Toronto,
laminectomy
tissue
may
muscle
and
its formation.
superficial
layers
of the annulus,
with a fine curette.
Three
dogs
D.C.,
Hospital,
diagrammatically.
EXPERIMENTAL
nine
University,
surface
operation
binds the undersurface
scar which
OF AMERICA,
of the source
of this scar formation
that the perineural
fibrosis
found
damaged
annulus
fibrosus.
fibrosis
after
Tulane
Wellesley
previous
posterior
STATES
in Dogs
CANADA
fibrous
FIG.
The phenomena
and Prophylaxis
UNITED
TORONTO,
Surgery,
of well
roots
Effects
LOUISIANA,
IAN MACNAB,
From
MEMBRANE*
meeting
ofthe
American
Academy
ofOrthopaedic
Surgeons,
Washington,
1972.
3,
AUGUST
1974
545
546
H. LAROCCA
At
I. MACNAB
the end of the first week fibroblastic
activity
spinae.
Fibroblasts
could
be seen to follow
the
erector
fibrous
scar
aspect
AND
gradually
of the
formed,
dura
to the
starting
nerve
from
roots.
the
was noted
extensions
erector
at the deep surface
of the haematoma.
spinae
If at laminectomy
the
and
extending
nerve
root
over
was
of the
A thick
the
lateral
exposed
as far
as the foramen,
this fibrous
scar also extended
out into the foramen.
A dense,
tough
membrane
thus formed
to fill the defect : this has been termed
the “laminectomy
membrane”
(Fig. 3).
It was noted
that the haematoma
that formed
in the anterior
part of the canal in response
to the scarification
procedure
resolved
by the third
week ; in these experiments
no significant
fibroblastic
activity
occurred
and
as a result,
the dura
to the canal
wall.
In all the animals
except
posterior
surface
of the intervertebral
disc,
as a result
of the interference
at operation,
and
nerve
roots
did
not
become
adherent
one, the neural
structures
did not adhere
to the
in spite of curettage
of the annulus.
In one dog,
extrusion
of nuclear
material
occurred,
and this
was associated
with dense
scarring
which
bound
derived
from the laminectomy
membrane.
The formation
ofthe
laminectomy
membrane
the
performed.
was
directly
proportional
to the
size
of the
the rawed
surface
of the erector
spinae
was
placed
The
laminectomy
extent
of the
was
fibrosis
to the
disc,
a consistent
in addition
to the
ofevery
laminectomy
result
scar
defect.
At the conclusion
in direct
membrane
peridural
root
contact
was
of every
with
placed
laminectomy
the dura.
between
It seemed
the muscles
would
be discouraged.
To study
this, in two dogs simple
segments.
The contents
of the spinal
logical,
therefore,
and the dura,
to
the
presume
development
that
if an inert
of peridural
fibrosis
laminectomy
canal
were
was
lightly
done at the
manipulated,
third,
fifth
but the
and seventh
annulus
was
left untouched.
The third
segment
served
as a control.
At the fifth segment
the surgical
defect
was packed
with Gelfoam.
At the seventh
segment
the defect
was covered
with a
Silastict
membrane.
These
animals
were killed
five weeks
later.
It was found
that Gelfoam
served
as an efficient
interposing
membrane
in both animals,
preventing
entry
of the laminectomy
membrane
into the spinal
canal.
In neither
animal
was
there
any adherence
of the scar to the dura
or to the nerve
roots
(Fig. 4).
Similar
results
were obtained
where
Silastic
sheeting
had been used as the interposed
membrane.
It was believed
that perineural
fibrosis
might
also be reduced
by surrounding
the nerve
root
with
dogs
in which
segment
encircled
millimetres.
The
an
the
by
impervious
the
root
barrier
root
canals
was
surrounded
a split
Silastic
introduction
of
of
Silastic
the
by
tube
of Gelfoam
or
fifth
l5
Gelfoam.
and
seventh
Gelfoam
and
centimetres
into
the
This
at
in
canals
was
segments
the
investigated
were
seventh
length
with
surrounding
At
segment
a wall
the
in eighteen
scarified.
nerve
the
the
thickness
roots
fifth
root
was
of
was
12
followed
by a constant
sequence
of events.
Initially,
the interstices
of the foam
filled with the cellular
elements
of blood
(Fig.
5).
By the third
day the foam
began
to fragment
and a leucocyte
infiltration
occurred.
By the third
week,
considerable
lysis
of the Gelfoam
had
been
accomplished
and the remaining
material
was irregular
and filiform
in appearance.
At the
sixth week there was no evidence
whatever
of any remaining
Gelfoam.
Of significance
is the
fact
that
the
and subsequently
with Gelfoam
The roots
surrounding
resorption
of this
substance
is not
associated
with
invasion
of granulation
tissue,
no scar tissue
replaces
it. After
six weeks
the roots
that had been
were all free and mobile
in the root canal.
enclosed
in a Silastic
tube remained
free in the tube and isolated
scar
tissue
interesting
that initially
formed
a thin flat stalk
no
matter
the blood
continuous
*
Gelatin
t
Dimethyl
how
dense
the
scar
tissue
happened
clot extended
into the tube,
from the outside
of the tube
foam,
to be (Fig.
encircled
from
6).
the
It was
and as the scar matured
it
to a thin layer of scar tissue
Upjohn.
siloxane
polymer,
Dow
Corning.
THE
JOURNAL
OF
BONE
AND
JOINT
SURGERY
THE
Figure
2-On
the
third
day
after
from
the
posterior
is
seen
anterior
LAMINECTOMY
laminectomy
outside
of the canal
through
the defect
and lateral
surfaces.
(Masson’s
trichrome
in blue. It fills the surgical
defect
and has
attachments
within
the spinal
canal,
where
j.4
the surgical
547
MEMBRANE
defect
is filled with
a haematoma,
which
into contact
with
the dura
and
the nerve
roots
stain,
x 07.)
Figure
3-The
mature
laminectomy
posterior
attachments
to the erector
spinae
muscle
it adheres
to the dura and nerve roots.
(Masson’s
stain,
x3.)
extends
along
their
membrane
mass
and
trichrome
FIG.5
Figure
4-Cross-section
of the spine
showing
that
an interposing
membrane
of Gelfoam
inserted
into
the
laminectomy
defect
is capable
of limiting
the laminectomy
membrane
to the exterior
of the spinal
canal.
(Masson’s
trichrome
stain,
.‘: 3.)
Figure
5-A
mass
of Gelfoam
is noted
to be in contact
with
the nerve
root
on the right.
Its interstices
are filled
with
blood
clot.
(Masson’s
trichrome
stain,
xO7.)
voi.
56B,
‘co.
3,
AUGUST
1974
H. LAROCCA
548
AND
I. MACNAB
FIG.
6
The nerve root on the right has been encircled
by a tube of Silastic.
A stalk of scar enters
through
the slit in the tube and is continuous
with a fine layer of scar immediately
about the
root.
The tube serves as an efficient
barrier
against
the laminectomy
membrane
which
approaches
it posteriorly.
(Masson’s
trichrome
stain,
x 3.)
7
FIG.
8
of a nerve root which has been enclosed
in a Silastic tube for twelve weeks.
The
is intact, and the arterioles
supplying
it are seen to be filled with micropaque,
indicating
(Haematoxylin
and eosin.
x 100.)
Figure
8-Positive
reproduction
of a radiograph
of the arterial anatomy
of spinal cord and roots, injected with micropaque.
The arterial supply of the root
enters from the antero-lateral
margin
of the spinal cord and courses
longitudinally.
The arteries
of the roots
are noted to be patent within the Silastic
tubes.
(x 2.)
FIG.
Figure
7-Cross-section
architecture
of the root
ante-mortem
patency.
THE
JOURNAL
OF
BONE
AND
JOINT
SURGERY
THE
that
surrounded
always
the
a free
root.
Between
the
animals
showed
were
killed
the motor
Microangiographic
(Fig. 7).
granules,
MEMBRANE
this
of scar
thin
layer
549
and
the
wall
of the
tube
there
was
space.
The effect of Silastic
tubing
week,
two weeks
and three
one
LAMINECTOMY
the
latency
on the viability
of the nerve was studied
weeks
after
implantation
of the Silastic
nerve
roots
time
studies
8).
the
exposed
by laminectomy.
and the root conduction
time
showed
that the microvascular
On histological
examination
indicating
that they were
the Marchi
stain
(Fig.
reaction
to ensheathing
were
the arterioles
patent.
The
In the dogs studied
nerve with a Silastic
in nine
tube.
were
myelin
further
Just
Electrical
to be normal
pattern
had
dogs
before
stimulation
in every
not been
instance.
disturbed
noted
to be filled with micro-opaque
sheath
was shown
to be intact
we could
tube.
not
find
evidence
of
any
by
adverse
DISCUSSION
Although
it was shown
by Key and Ford (1948) that perineural
adhesions
from
the annulus
after
excision
of a disc, our experiments
suggest
that
peridural
fibrosis
is the
rawed
with clinical
experience.
the site of the previous
under
the
adjacent
continuity
with
These
a wide
favoured
the
surface
of the
Re-exploration
laminectomy.
portions
of intact
scar
extends
that
experiments
muscles
laminae.
around
demonstrated
that
dura
the fibrous
animals
studied
was
completely
canal.
tubing
after
extensive
dissection
clinical
application
must
lumbar
nerve roots.
was
dangerous,
to translate
the
experience,
these experiments
following
precautions
should
be as restricted
as possible,
2) a dry
field
should
extensively
exposed
of the erector
spinae
shown
Standard
.
lumbar
in limiting
This
is in accord
is always
laminectomy
was
tissue
at
extends
seen
to be in
defect.
always
more
marked
when
of a large
epidural
haematoma
limits of the laminectomy
defect.
on the benign
1945 ; Reynolds
the
nature
and
of Gelfoam
Ford
1953)
laminectomy
in preventing
(Correll,
which
in
membrane
penradicular
to the
adhesions
in the foramina,
sii#{231}eit is not resorbed
its
study
of the microvascular
pattern
of human
shown
to be effective
by the fifth week.
during
Though
the period
of fibrous
it is always
difficult,
tissue
and
response
at times
findings
of experimental
investigation
into the sphere
of clinical
on the formation
of the laminectomy
membrane
suggest
that the
always
be undertaken
at operation
: 1) the laminectomy
should
consistent
with thorough
decompression
of the involved
nerve;
be obtained
and
maintained
nerve
roots,
and the
muscles
by a barrier
SUMMARY
1
the
response
to be effective
around
nerve
roots
await
a more
detailed
Gelfoam,
however,
was
was completely
resorbed
and
successful
dura.
be formed
source
of
reveals
dense
scar
dura and sometimes
fibrosis
from
operative
exposure
was employed.
The presence
the extension
of the peridural
fibrosis
beyond
the
exterior
of the spinal
Though
Silastic
the
Periradicular
the
The experiments
corroborated
previous
reports
Prentice
and Wise
1945 ; Pilcher
and Meacham
the
overlying
of the spine commonly
This fibrosis
engulfs
the
might
a major
laminectomy
was
; and
3) at the
dura,
should
of impervious
AND
conclusion
be separated
material.
of the
from
the
decompression
rawed
surface
CONCLUSIONS
performed
at
multiple
levels
in
thirty
dogs,
and
manipulations
were carried
out in the spinal
canal
to observe
their effects
on periradicular
adhesion
formation.
The canal
was scarified,
packed
with Gelfoam,
or treated
with three
varieties
of Silastic
membranes.
The results
were serially
assessed
from three
days to twelve
weeks
by gross observation,
nerve
conduction
studies,
histological
examination
of transverse
sections
supply
56
VOL.
8
of the spine,
to the roots.
myelin
B,
1974
NO.
3,
AUGUST
study
of
lumbar
roots
and
micropaque
study
of
the
arterial
550
2.
H. LAROCCA
The
fibrous
covers
results
were
consistent
tissue elements
the laminectomy
and
nerve
3.
Gelfoam
membrane.
adhesions
4. Certain
biologically.
AND
I. MACNAB
The
ofthe
erector
spinae
muscle
defect
and extends
into
principal
source
of scar
is dorsally
mass.
This scar, the laminectomy
the canal
bilaterally
to adhere
in the
membrane,
to the dura
roots.
not contribute
to scar formation,
but instead
acts as an effective
interposing
Silastic
membranes
are capable
of providing
protection
against
nerve
root
without
interfering
with the anatomical
or physiological
integrity
of the nerves.
clinical
implications
of the study
are discussed.
does
This experimental
of Ontario.
study
was
carried
out
with
the aid
of a grant
from
the Workmen’s
Compensation
Board
REFERENCES
CORRELL,
J. T.,
Surgery,
J. A., and
KEY,
30-A,
PILCHER,
FORD,
Journal
and
E. C. (1945):
81, 585-589.
WISE,
Obstetrics,
L. T. (1948):
Experimental
Biologic
intervertebral-disc
investigations
of a new absorbable
lesions.
Journal
sponge
and
ofBone
andJoint
sponge.
Surgery,
621-630.
C., and
neurosurgery.
REYNOLDS,
H. R., and
PRENTICE,
Gynecology
MEACHAM,
W.
Surgery,
Gynecology
F. C., and
of Bone
FORD,
and
Joint
F. (1945):
gelatin
thrombin
81, 365-369.
An experimental
study of the use of Gelfoam
Obstetrics,
35-A,
980-982.
L. T. (1953):
Surgery,
Absorbable
and
THE
JOURNAL
OF
BONE
for
hemostasis
to fill defects
AND
JOINT
in bone.
SURGERY
in