Step 1: Total Facetectomy
This report describes L4-L5 posterior lumbar interbody fusion for L4
degenerative spondylolisthesis. The patient undergoes general endotracheal
anesthesia and is positioned prone on a table or frame to decrease abdominal
pressure. A routine posterior approach through a midline 10-cm incision is
employed, thus exposing the L4 and L5 vertebrae. Laminectomy is performed for
almost all of the caudal two-thirds of the L4 spinous process and laminae,
including both inferior facets, with use of an osteotome
(Fig. 1, A). We use
the cut-line of the laminectomy as a landmark for the cranial end of the
superior facet, as the superior facet is usually hypertrophic in patients with
degenerative spondylolisthesis. The cranial attachment of the ligamentum
flavum is then resected by undercutting of the L4 lamina. Next, the medial
edge of the superior facets of L5 and the cranial portion of the L5 lamina are
excised with use of an osteotome (Fig. 1,
B). After confirming the location of the cranial edge of
the L5 pedicle, we then make a cut at the cranial edge of the L5 superior
facet above the L5 pedicle with use of an osteotome. These procedures enable
total resection of the ligamentum flavum and exposure of the neural elements
(Fig. 1, C). The
resected bone is used for bone graft as blocks or chips. Meticulous hemostatic
control of the extradural venous plexus with use of a bipolar cautery is
necessary for fine exposure of the intervertebral disc. The extradural venous
plexus is comprised of three components: the cranial (L4) nerve root, the
caudal (L5) nerve root, and the thecal sac. At first, the scar and epidural
veins are electrocoagulated with a bipolar cautery with cauterization ending
at the cranial wall of the L5 pedicle, which serves as a safety zone. Next,
after the medial wall of the L5 pedicle is identified, the epidural veins
around the L5 nerve root and the thecal sac are electrocoagulated and cut and
the L4 nerve root is identified and protected while the epidural veins around
the L4 nerve root are electrocoagulated. The thecal sac and the L5 nerve root
are then retracted with a nerve-root retractor to identify the posterior wall
of the intervertebral disc and the vertebral body. If bleeding from epidural
vessels cannot be controlled with bipolar electrocautery, control is best
achieved with use of a topical hemostatic agent and packing with
cottonoids.
Step 2: Total Discectomy
To achieve an effective interbody arthrodesis, we are convinced that
preparation of the fine-bone-graft area is one of the most important parts of
the
procedure1-3.
The fine-bone-graft area is defined as a wide and flat area with preservation
of the osseous end plate. Subtotal discectomy consists of excision of as much
of the anulus and the perimeter of the end plate as necessary to achieve an
extensive bone-graft area yet allow preservation of the osseous end plate. We
believe that total facetectomy facilitates identification of the lateral
border of the intervertebral disc and achievement of the widest bone-graft
area possible. After the posterior aspects of the disc are exposed, the
intervertebral disc space is enlarged with a lamina spreader that is placed in
the space between the laminae at L4 and L5. Discectomy is then performed
centrally, with use of a scalpel, at the junction of the anulus and the end
plate, leaving the peripheral border of the disc intact while retracting the
neural elements (Fig. 2,
A). After subtotal resection of the anulus with rongeurs,
a small Cobb elevator is used to separate the cartilaginous end plate from the
osseous end plate. This maneuver must be performed with care to preserve the
integrity of the subchondral osseous end plate. If the end plates are
excessively concave, a chisel may be used to flatten the contour of the end
plates slightly, taking care to preserve as much of the osseous end plate as
possible (Fig. 2, B).
Whenever the anterior portion of the intervertebral disc is manipulated, it is
important to confirm the exact location of the anterior edge of the disc. The
anulus and cortical end plate at the anterior portion of the disc space are
raked out with a curet and excised. Finally, the irregular surface of the
osseous end plate is flattened with use of an appropriately sized disc shaver.
In these steps, excessive retraction of the neural elements is unnecessary, as
the total facetectomy provides more working space and a wide-angle approach to
the neural elements and intervertebral
disc1. We believe
that preservation of the osseous end plate and provision of a large amount of
bone graft are important to the prevention of subsidence and essential to good
fusion1-3.
Step 3: Cage and Bone Graft (Figs.
3 and
4)
A large amount of bone graft also appears to be important to the success of
the interbody arthrodesis procedure. The bone-grafting procedure involves the
insertion of autologous bone blocks, autologous bone chips, and Brantigan
interbody fusion cages (DePuy Spine) in the manner of a sandwich (a minimum of
two autologous bone blocks, then two chip-filled fusion cages, then a minimum
of two more autologous bone blocks). Thus, with bilateral discectomy, one cage
is inserted on either side of the vertebral midline, followed by insertion of
bone blocks laterally. The two rectangular cages are used to prevent collapse
of the graft and to avoid subsidence. In our series, the same size cage
(height, 10 mm; width, 10 mm; length, 25 mm) was used for 97% of the patients.
First, the cage (filled as tightly as possible with autologous bone chips) is
inserted while the neural elements are protected
(Fig. 3, A). As with
the discectomy, excessive nerve retraction is unnecessary. The cage is then
moved centrally, with the use of two chisels, by keeping one chisel in a fixed
position while twisting the other (Fig. 3,
B). Next, autologous bone blocks are inserted lateral to
the cage (Fig. 3, C and 3,
D). After one cage and bone blocks have been inserted on
one side, another cage and bone blocks are inserted in a similar manner on the
contralateral side. Bone blocks are harvested from the excised spinous
process, the laminae, the inferior facets, and the superior facets
(Fig. 4, A and 4,
B). Usually, three bone blocks of almost the same size as
the cage can be obtained from excised spinous processes and inferior facets,
and smaller bone blocks can be obtained from the excised laminae and superior
facets. The height of the bone block is made even to that of the cage. Surplus
bone is then broken into small chips with use of a bone mill and packed into
the cage (Fig. 4, C and 4,
D). No posterior iliac crest bone is used. Cages and
autologous bone blocks should be placed 3 to 5-mm deep to the posterior
vertebral margin. In addition, the upper edge of the grafted bone should be
examined to be certain that it does not impinge on the exiting L4 nerve
root.
Step 4: Pedicle Screw Fixation
We usually place pedicle screws after completion of the bone graft. To
avoid loosening or decreased fixation force, the pedicle screws must be aimed
carefully so that they are placed accurately on the first try. The starting
point for placement of the pedicle screw is important. We start the L4 pedicle
screw at the vertex of a triangular ravine between the lateral edge of the
lamina and the accessory process (Fig. 5,
A). The L4 pedicle screw is inserted in an upward
direction to avoid injury to the adjacent cranial facet joint by the screw
head. The L5 pedicle can be seen extending from the cranial to the medial
wall. We start by exposing the posterior tip of the L5 superior facet, which
will be used as the starting point for the L5 pedicle screw. Careful
identification of landmarks and sounding of the cavity are needed to prevent
canal penetration; however, we have not used fluoroscopic guidance or computer
navigation during insertion of the pedicle screw. Pedicle screw size is
determined by measuring the size of the pedicle on the preoperative computed
tomographic images; we have found that this measurement often reveals that a
screw of the same size as the L4 pedicle screw (width, 6.25 mm; length, 45 mm)
may be used. Intraoperative radiography is used to confirm that the pedicle
screw is in the proper position. A plate as short as possible is then selected
and bent to accommodate the inclination of the pedicle screw. First, the plate
is connected with the cranial pedicle screw at the upper (cranial) end of the
plate nest to avoid injuring the adjacent facet joint
(Fig. 5, B). As the
screw nut is tightened, the spondylolisthesis is gradually reduced
(Fig. 5, C). It is
important to confirm the location of the neural elements during the reduction
procedure because the cages or bone blocks often bulge posteriorly as the
reduction takes place. The caudal end of the plate is then connected, and the
screw head is cut. We have found that injury to the facet joint can be avoided
by making the starting point for placement of the pedicle screw less medial
and less cranial. In fact, we have confirmed the integrity of the L3-L4 facet
joint at revision surgery in patients with adjacent segment degeneration, and
we have found that none of these patients had L3-L4 facetjoint injury as a
result of the plate system.
CRITICAL CONCEPTSINDICATIONS:All patients considered for surgery have severe, disabling low back pain
accompanied by lower extremity pain that is unresponsive to conservative
treatment, including epidural steroid injection. Indications for posterior
lumbar interbody fusion are as follows:Spondylolisthesis with slippage in excess of 3 mm and a posterior opening
of >5° on a lateral flexion radiographLumbar canal stenosis or disc herniation requiring wide decompression and
discectomyCONTRAINDICATIONS:Active infectionMetastatic spinal tumorA massive defect of the vertebral end plates or bodies due to osteoporosis,
fracture, or intraspinal neoplasmPITFALLS:Bleeding can be extensive with this procedure; preoperatively, we strive to
have the patient donate 400 to 800 mL of autologous blood for transfusion.Forcible reduction of the spondylolisthesis or distraction of the
intervertebral disc space by pedicle screws carries a risk of vertebral
fracture or loosening of the pedicle screw, particularly in elderly
patients.Vascular injury. We have not encountered any major vascular injuries
intraoperatively. Nonetheless, the aorta and inferior vena cava lie anterior
to the spinal column, so whenever the anterior portion of the intervertebral
disc is manipulated, confirmation of the anterior edge of the vertebral body
is warranted.Excessive distraction of the intervertebral disc space. We usually install
the lamina spreader between the caudal edge of the remnant L4 lamina and the
superior edge of the L5 lamina. Excessive distraction with the lamina spreader
can cause slippage of the device or collapse of the lamina.Identification of the cranial (L4) nerve root. While excising as much as
possible along the peripheral border of the intervertebral disc, protection of
the cranial nerve root is necessary. When cranial nerve root exposure is
insufficient, manipulation at the peripheral border of the disc should be
undertaken with great care during disc excision and when inserting bone-graft
material. We are convinced that our low rate of neurological complications is
due to generous exposure of the neural elements
(Fig. 6).AUTHOR UPDATE:The principles of the procedure used today (and reported herein) resemble
those used in the originally reported series. However, slight modifications
have been made to the surgical technique. Specific changes include the
following:The improved procedure now permits less invasive access through smaller
incisions.If patients are elderly or have osteoporosis, we are more circumspect in
excising the cartilaginous end plate so as to avoid breaking the osseous end
plate. In addition, we try to graft a larger amount of bone, particularly in
elderly patients and/or patients with osteoporosis. A minimum of four
autologous bone blocks (two on each side) are placed around the cages.
CRITICAL CONCEPTS
INDICATIONS:
All patients considered for surgery have severe, disabling low back pain
accompanied by lower extremity pain that is unresponsive to conservative
treatment, including epidural steroid injection. Indications for posterior
lumbar interbody fusion are as follows:
Spondylolisthesis with slippage in excess of 3 mm and a posterior opening
of >5° on a lateral flexion radiographLumbar canal stenosis or disc herniation requiring wide decompression and
discectomy
Spondylolisthesis with slippage in excess of 3 mm and a posterior opening
of >5° on a lateral flexion radiograph
Lumbar canal stenosis or disc herniation requiring wide decompression and
discectomy
CONTRAINDICATIONS:
Active infectionMetastatic spinal tumorA massive defect of the vertebral end plates or bodies due to osteoporosis,
fracture, or intraspinal neoplasm
Active infection
Metastatic spinal tumor
A massive defect of the vertebral end plates or bodies due to osteoporosis,
fracture, or intraspinal neoplasm
PITFALLS:
Bleeding can be extensive with this procedure; preoperatively, we strive to
have the patient donate 400 to 800 mL of autologous blood for transfusion.Forcible reduction of the spondylolisthesis or distraction of the
intervertebral disc space by pedicle screws carries a risk of vertebral
fracture or loosening of the pedicle screw, particularly in elderly
patients.Vascular injury. We have not encountered any major vascular injuries
intraoperatively. Nonetheless, the aorta and inferior vena cava lie anterior
to the spinal column, so whenever the anterior portion of the intervertebral
disc is manipulated, confirmation of the anterior edge of the vertebral body
is warranted.Excessive distraction of the intervertebral disc space. We usually install
the lamina spreader between the caudal edge of the remnant L4 lamina and the
superior edge of the L5 lamina. Excessive distraction with the lamina spreader
can cause slippage of the device or collapse of the lamina.Identification of the cranial (L4) nerve root. While excising as much as
possible along the peripheral border of the intervertebral disc, protection of
the cranial nerve root is necessary. When cranial nerve root exposure is
insufficient, manipulation at the peripheral border of the disc should be
undertaken with great care during disc excision and when inserting bone-graft
material. We are convinced that our low rate of neurological complications is
due to generous exposure of the neural elements
(Fig. 6).
Bleeding can be extensive with this procedure; preoperatively, we strive to
have the patient donate 400 to 800 mL of autologous blood for transfusion.
Forcible reduction of the spondylolisthesis or distraction of the
intervertebral disc space by pedicle screws carries a risk of vertebral
fracture or loosening of the pedicle screw, particularly in elderly
patients.
Vascular injury. We have not encountered any major vascular injuries
intraoperatively. Nonetheless, the aorta and inferior vena cava lie anterior
to the spinal column, so whenever the anterior portion of the intervertebral
disc is manipulated, confirmation of the anterior edge of the vertebral body
is warranted.
Excessive distraction of the intervertebral disc space. We usually install
the lamina spreader between the caudal edge of the remnant L4 lamina and the
superior edge of the L5 lamina. Excessive distraction with the lamina spreader
can cause slippage of the device or collapse of the lamina.
Identification of the cranial (L4) nerve root. While excising as much as
possible along the peripheral border of the intervertebral disc, protection of
the cranial nerve root is necessary. When cranial nerve root exposure is
insufficient, manipulation at the peripheral border of the disc should be
undertaken with great care during disc excision and when inserting bone-graft
material. We are convinced that our low rate of neurological complications is
due to generous exposure of the neural elements
(Fig. 6).
AUTHOR UPDATE:
The principles of the procedure used today (and reported herein) resemble
those used in the originally reported series. However, slight modifications
have been made to the surgical technique. Specific changes include the
following:
The improved procedure now permits less invasive access through smaller
incisions.If patients are elderly or have osteoporosis, we are more circumspect in
excising the cartilaginous end plate so as to avoid breaking the osseous end
plate. In addition, we try to graft a larger amount of bone, particularly in
elderly patients and/or patients with osteoporosis. A minimum of four
autologous bone blocks (two on each side) are placed around the cages.
The improved procedure now permits less invasive access through smaller
incisions.
If patients are elderly or have osteoporosis, we are more circumspect in
excising the cartilaginous end plate so as to avoid breaking the osseous end
plate. In addition, we try to graft a larger amount of bone, particularly in
elderly patients and/or patients with osteoporosis. A minimum of four
autologous bone blocks (two on each side) are placed around the cages.