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54
Anterior and Posterior Decompression and
Stabilization in Patients With Metastatic
Disease Using the Transpedicular Approach
Fintan J. Shannon and Patrick J. Boland
Goals of Surgical Treatment
1. A single posterior incision
2. Three-column tumor decompression
3. Durable immediate fixation
Diagnosis
The diagnosis of metastatic disease to the spine is made from the history,
physical examination, radiographic studies, and histologic examination.
Plain radiographs, isotope bone scan, and computed tomography are all
used, but magnetic resonance imaging (MRI) is the established gold standard. Preoperative evaluation of the entire spine is essential to (1) provide
detailed assessment of the offending lesion, and (2) to detect and quantify
the degree of tumor involvement in adjacent levels. Positron emission
topography (PET) scans may be valuable in distinguishing osteoporotic
fractures from those due to tumor.
Angiography and embolization should be done preoperatively in
patients with suspected vascular tumors (e.g., myeloma, renal cell, thyroid
and some sarcomas). Surgery should be performed within 48 hours of em-
bolization.
Indications for Surgery
1. Failed radiotherapy or history of radiotherapy to spinal cord tolerance
2. Radioresistant tumors (e.g., renal, melanoma)
3. Patient with expected survival more than 2 months
4. Circumferential bony disease with or without spinal cord compression
(Fig. 54–1)
5. High-grade spinal cord compression from epidural disease
6. Disease involving the vertebral body and one/both pedicles with or
without posterior disease
7. Extensive unresectable paraspinal mass (precluding anterior vertebral
body access)
8. Any medical contraindication to an anterior/transcavitary approach
a. Compromised pulmonary function
b. Concurrent medical illness
c. Previous anterior surgery
d. Previous radiation to abdomen/thorax
Contraindications
1. Isolated anterior epidural tumor
2. Disease confined to vertebral body only
3. Primary resectable bone tumors
Advantages
1. The entire procedure can be performed through a single posterior inci-
sion.
2. Allows excellent circumferential access for decompression of spinal
cord and nerve roots.
3. Circumferential stabilization is achieved.
4. Immediate postoperative mobilization without orthosis.
5. Significant pain relief.
6. Low risk of postoperative morbidity; eliminates the morbidity of thora-
cotomy/anterior abdominal surgery.
Disadvantages
1. Anterior dura not well visualized.
2. Anterior visualization and instrumentation is more difficult when
compared with an anterior approach.
3. Anterior bleeding can be more difficult to control.
Procedure
Setup and Approach
Following induction of general anesthesia, the patient is turned from the
supine to the prone position. Bolsters should be placed along each side of
the patient extending from the axilla to the anterior superior iliac spine.
With this arrangement, the anterior chest and abdominal walls should
clear the table and be able to expand. The table is tilted so that the patient
lies in a mild Trendelenburg position. Alternatively, the patient may be
placed in the knee-chest position. The head is placed in a Mayfield pin
fixation device.
The gluteal cleft and the C7-T1 spinous processes mark the midline,
and typically all spinous processes are palpable between these levels. The
level of interest is confirmed by using the 12th rib to identify T12 and then
counting up or down as appropriate. The L4 spinous process is located on
the same axial plane as the iliac crest, which is easily palpable laterally.Intraoperative x-ray confirmation may be carried out if necessary.
A posterior midline incision centered over the affected level is made long
enough to expose the entire length to be instrumented (Fig. 54–2).
If a posterior soft tissue tumor mass is present, sharp dissection is used
outside the mass, prior to its excision with the posterior bony elements.
During the stripping of paraspinous muscles from the spinous process and
laminae, care must be taken to avoid inadvertently plunging through the
vertebral lamina, which may be deficient owing to tumor destruction.
Tumor Decompression
1. The posterior bone work is initiated by removing the spinous process
of the involved vertebra with a rongeur.
2. Following clear identification of the affected lamina, transverse
process, and pars, the posterolateral aspect of the tumor mass is then
removed in piecemeal fashion.
3. A high-speed bur is used to thin the lamina to a cortical shell prior to
its excision with a rongeur. The ligamentum flavum and posterior
epidural tumor is then removed with tenotomy scissors. It is necessary
to resect one half of the laminae above and below the resected tumor
level to gain access to the cranial and caudal vertebral discs (Fig. 54–3).
4. Bilateral facetectomies are accomplished using the burr, and each
tumor-laden pedicle can be gently curetted from inside outward, collapsing it in on itself once the core is removed. If a pedicle is disease
free, the high-speed bur is used to remove its cancellous core and preserve the medial cortical margin (Fig. 54–4).
Nerve roots encased in tumor can occasionally be dissected free by
sharp dissection, but if necessary, a thoracic motor nerve root on one or
both sides can be clipped and divided distal to the ganglion to improve
access to the vertebral body. Nerve roots should be preserved in the lumbar
spine whenever possible and when a major radicular feeding artery to the
cord has been identified on preoperative angiography (the artery of Adamkiewicz).
The cancellous or tumor-laden bone of the vertebral body can be removed using the high-speed burr, or it can be removed piecemeal using an
angled cup curet and pituitary forceps (Fig. 54–5). A very thin rim of bone
is left at the circumference of the vertebral body, both to provide a mold
into which the polymethylmethacrylate (PMMA) can be injected and to
prevent extrusion into the mediastinum or retroperitoneum. Typically, the
posterior longitudinal ligament (PLL) is sacrificed and the anterior longitudinal ligament is preserved. In the thoracic spine, the plane between the
dura and the PLL may be difficult to identify, but can be sharply dissected
with tenotomy scissors (Fig. 54–6). Care should be taken not to enter the
thoracic, mediastinal, or retroperitoneal spaces during removal of the
vertebral body.
All disc material above and below the resected body is removed using a
scalpel and a sharp angled curet until the adjacent vertebral end plates are
encountered. This ensures bone to cement contact above and below.
Instrumented Stabilization
Insertion of Steinmann Pins and PMMA
1. Right-angled clamps are used to create starting holes in the vertebral
body end plates above and below.Steinmann pins of medium diameter
are cut to an appropriate length, gently curved and driven, one at a
time, through the end plate of the cranial vertebral body using a needle
holder with a gentle rotational movement. The pin is then driven back
through the starting hole in the caudal vertebral body. The second pin
■
250
SECTION III THE LUMBAR SPINE
Eurostile
Tumor
Preserve
nerve
roots
Cord
Skin
incision
Circumferential tumor
Vertebral
body
Body
A
Circumferential tumor
Figure 54–1
B
(A,B) Tumor involving the anterior, middle, and posterior columns of the spine. The tumor may surround
or invade the canal; thus it is called a “circumferential tumor.”
Tumor
Pedicle
removed
Pedicle is burred
to gain access
to tumor
Rib 12
L4
Figure 54–2
Posterior midline incision spanning the length of proposed instrumentation.
Cancellous pedicle
cone burred
(lateral view)
Tumor
Thinned laminae
removed with
rongeur
Figure 54–3
Resect one half of the laminae above and below the resected tumor level to gain access to the
cranial and caudal vertebral discs.
Eurostile
Figure 54–4
Decompression of the tumor through the intact pedicle using a burr. The
medial cortical margin must be preserved.
54 TRANSPEDICULAR APPROACH
251
■
Figure 54–5
The cancellous or tumor-laden bone of the vertebral body can be removed using
the high-speed burr, or it can be removed piecemeal using an angled cup curet
and pituitary forceps.
Tumor-laden
bone of vertebral
body removed
piecemeal
PLL
Tenotomy
scissors
Identity plane
and posterior longitudinal
between dura
ligament
Scissors
(Axial view of 6A)
A
Dura
Figure 54–6
(A,B) Tenotomy scissors are used to develop the plane between the dura and the
posterior longitudinal ligament (PLL).
■
252
SECTION III THE LUMBAR SPINE
Eurostile
PLL
B
Fill with
t
cement
T2
T3
T4
Pins
inserted
Figure 54–7
Steinmann pins are placed through the end plates of the vertebral bodies. The pin
is placed through the cranial end plate and then driven back through the caudal
body. The second pin is placed on the contralateral side in similar fashion.
T5
T6
T7
T8
T9
T10
T11
T12
Figure 54–9
Posterior instrumentation is inserted into the spine spanning the reconstructed
segment.
Cover pins
with cement
A
Figure 54–8
(A,B) Polymethylmethacrylate (PMMA) is introduced into the cavity using a widenozzle syringe with a suction catheter attached.
Eurostile
Keep 1cm
gap (cord
o cement)
B
54 TRANSPEDICULAR APPROACH
253
■
Figure 54–10
The operative magnetic resonance imaging (MRI) documenting the exact location
and confines of the tumor.
A
B
Figure 54–11
(A,B) Disease involving the vertebral body and one or both pedicles with or
without posterior disease.
Figure 54–12
A lateral radiograph taken prior to discharge for use as a baseline against which
future studies can be compared to assess alignment of the spine and implanted
hardware.
■
254
SECTION III THE LUMBAR SPINE
Eurostile
is then inserted on the contralateral side of the cavity and parallel to
the first (Fig. 54–7).
2. The length should be such that each pin spans the resection cavity and
is anchored within the caudal and cranial vertebral body (∼ 1 cm).
3. The pin position must be checked with a lateral x-ray prior to cement
insertion. It may be convenient to insert the pedicle screws after the
Steinmann pins, so that one x-ray will suffice.
4. Slow-curing PMMA is mixed with tobramycin and loaded into a widenozzle syringe with a suction-tip catheter attached. The cavity should
be thoroughly irrigated, dried, and free of all gross blood prior to introduction of the cement. The cavity is filled from the deepest portion
outward until the Steinmann pins are covered (Fig. 54–8). Typically
the cavity resulting from removal of one vertebral body will accommodate one half to three quarters of one 40-g cement mix. A 0.5- to 1-cm
gap should exist between the spinal cord and the anterior cement
block. The area is copiously irrigated with cool saline and an angled
instrument is used to keep the semisolid acrylic away from the dura.
When the acrylic has hardened, the surgeon then proceeds with posterior instrumentation.
Not infrequently, the paravertebral muscles are infiltrated with tumor,
and sections of muscle, subcutaneous tissue, and occasionally skin must
be excised. Plastic/reconstructive surgeons should be available for intraoperative consultation and assistance as necessary. Local muscle flap
coverage (e.g., trapezius, latissimus dorsi) should be considered where
skin is compromised secondary to previous radiation, tumor involvement,
or previous surgery.
Exposure Secrets (Fig. 54–11)
1. Embolize suspected vascular tumors preoperatively.
2. In vascular tumors, insert pedicle screws before proceeding with
piecemeal vertebrectomy.
3. Sacrifice a thoracic nerve root to improve visualization of verte-
brectomy cavity.
4. Avoid pedicle screws in thin patients or at the apex of a kyphosis; use
sublaminar hooks.
5. If expected survival is greater than 12 months, supplement with bone
graft posteriorly (note: if using autograft, e.g., iliac crest, ensure that
this area is not involved with tumor preoperatively).
Insertion of Pedicle Screws
The pedicle screws may be inserted before proceeding with anterior resection. This is particularly advisable in vascular tumors such as myeloma,
renal cell, thyroid, and some sarcomas. A bleeding tumor bed renders the
patient at increased risk and can impair visualization of the operative site.
The soft tissues are stripped subperiosteally off the posterior elements.
The lumbar spine pedicle is located at the junction of the transverse
process, lamina, pars interarticularis, and the caudal tip of the superior
facet. When this point is identified, a high-speed bur (size) or rongeur is
used to penetrate the cortex. The pedicle probe is inserted and advanced
carefully in an anteromedial (lumbar spine) direction following the path of
least resistance. Never force this instrument! When the instrument no
longer advances with relative ease, you have reached the cortical bone of
the anterior vertebral body margin. A ball-tipped probe is inserted to ensure an intact bony circumference and measure the depth. If at this point
you are not confident of your position, place a Steinmann pin in the hole
and take a lateral x-ray. Tap the proposed channel and insert the screw.
One-quarter-inch rods are then contoured to the shape of the spine and
locked to the hooks or pedicle screws (Fig. 54–9).
Note 1
1. The proximal thoracic spine will usually accommodate screws with a
diameter of 5 to 6 mm, whereas 7- to 8-mm screws are used in the lumbar spine.
2. If screw purchase is poor, (a) consider augmentation with PMMA, (b)
consider using sublaminar hooks, or (c) consider extending your construct to the level above/below.
3. As a general rule, we use pedicle screws below T7 and sublaminar
hooks above.
4. Avoid high-profile pedicle screws in thin patients, especially at the
apex of a kyphosis. Sublaminar hooks generally have a lower profile, a
lower chance of skin irritation, and can be used where the vertebral
body is diseased.
Note 2
Preoperative MRI is essential to accurately document the presence or absence of disease in the adjacent vertebrae. For a one-level spondylectomy,
posterior instrumentation should extend two levels above and below the
disease. Titanium implants are used to facilitate future postoperative imaging and two cross-links are used to increase torsional stability (Fig. 54–10).
Pitfalls
1. Incorrect pedicle screw placement
a. Too superior: may enter disc space with poor screw purchase
b. Too inferior: risk of nerve root injury
c. Too medial: spinal canal compromise; epidural plexus injury
d. Too lateral: epidural plexus injury; poor screw purchase
2. Incorrect Steinmann pin placement
3. Incomplete filling of cavity with cement
a. Ensure dry cavity
b. Insert cement when in liquid phase
Complications
1. Skin necrosis/wound breakdown
a. Secondary to previous radiotherapy/tumor invasion/previous
surgery
b. Prominent hardware
c. Poor mobility/pressure necrosis
2. Extrusion of cement anteriorly: avoid pressurization
3. Dural leak: especially in previously irradiated epidural tumor
4. Accidental nerve root injury
5. Instrumentation failure: pedicle screw
6. Pedicle screw cut out (soft bone)
Postoperative Care
1. Drains removed at 48 hours or when drainage is less than 100 cc/24
hours.
2. Early mobilization without orthosis, usually day 1.
3. Standing lateral (Fig. 54–12) and anteroposterior (AP) radiographs are
taken prior to discharge for use as a baseline against which future studies can be compared to assess alignment of the spine and implanted
hardware.
Suggested Reading
Bilsky MH, Boland PJ, Lis E, Raizer JJ, Healey JH. Single-stage post-
erolateral transpedicle approach for spondylectomy, epidural decompression, and circumferential fusion of spinal metastases. Spine
2000;25:2240–2250.
Eurostile
54 TRANSPEDICULAR APPROACH
255
■
55
Spondylolysis Repair
Modified Scott Wire Technique
Kim W. Hammerberg and James M. Osborn
Goals of Surgical Treatment
To unite the pars defect and maintain the lumbar motion segment function.
Diagnosis
Repetitive stress spondylolysis is demonstrated by anteroposterior (AP),
lateral, and oblique radiographs of the lumbar spine. Bone scans can be
helpful in differentiating an acute lysis from a chronic lysis with pseudarthrosis. Computed tomography (CT) scans or magnetic resonance imaging
(MRI) can also be helpful in detecting a lysis as well as determining its
chronicity.
Indications for Surgery
1. Refractory back pain
2. Normal disc morphology on MRI
3. Low-grade slip (쏝 5 mm)
4. Less than 30 years of age
Contraindications
1. Significant disc degeneration
2. Radicular symptoms requiring decompression
3. Slips 쏜 5mm
4. High-demand patients
5. Significant dysplasia in the posterior elements
6. Other mitigating factors (e.g., rheumatoid arthritis, chemotherapy)
Advantages of This Technique for Direct Repair of
Spondylolytic Defect
1. Preservation of motion segment with less distortion of normal spinal
mechanics.
2. Shorter operative time.
3. Less average blood loss.
4. Low-profile, inexpensive instrumentation.
5. Hardware can be retained.
6. Does not interfere with posterior segmental fusion if a salvage procedure is required.
Disadvantage
Pseudarthrosis rate of between 4 and 37%.
Procedure
The basic principles of pseudarthrosis surgery apply: meticulous debridement, autogenous bone graft, and compression across the fracture site.
Positioning and Incision
Endotracheal anesthesia is established. The patient is placed in the prone
position with support of the thorax and iliac crests, and the abdomen left
free. The incision is midline, centered over the spinous processes, and
should extend only one level above and below the lesion. The lumbar
aponeurosis is split and freed from the spinous processes utilizing the full
extent of the incision. A Cobb elevator is used to subperiosteally reflect the
paraspinal muscles across the lamina and the face of the facets bilaterally.
Care should be taken to preserve the facet capsules and confine the exposure to the pars at the pathologic level only. Self-retaining retractors are
used to hold the soft tissues clear of the operative field.
Dissection of the Pars Interarticularis and Repair of the Defect
The fibrofatty tissue of the pseudarthrosis is removed using curets and
rongeurs. Care should be taken to denude the sclerotic parts to raw bleeding bone. Once the pseudarthrosis has been debrided, the defect can be
bone grafted and repaired. Prior to beginning the repair the inferior one
third of the inferior facet of the vertebra above is amputated using a small
osteotome (Fig. 55–1). Some authors believe that an enlarged inferior facet
can contribute to the pathologic defect. Routinely 18-gauge Drumond
wires are used. With a hand or power drill, a hole is made in the base of the
superior facet of the involved vertebra exiting at the junction of the facet
and the superior pedicle. A wire is then passed in a ventroinferior to dorsosuperior direction through the drill hole, leaving the button on the ventral
wall of the superior facet of the involved segment (Fig. 55–2). This procedure is then repeated on the opposite facet at the same level. One wire
from each pair is passed beneath the spinous process, across the midline,
and twist-tied to the remaining wire. When both sides are tied, each side is
tightened in sequence until the pars defect and graft material are compressed (Fig. 55–3).
Wound Closure
The wound is closed in three layers: the deep fascia is closed tightly with
an interrupted absorbable stitch, and suture of the subcutis and skin follows. A drain is placed superficial to the fascia.
Surgical Secrets
1. Facet capsules should not be violated, if possible.
2. Partial (one-fourth to one-third) facetectomy should be carried out superior to the defect and may serve as bone graft material.
3. To increase the fusion surface, decorticate the lamina and transverse
process at the involved level and place bone graft.
4. Ample autogenous bone graft should be used. We prefer autogenous
iliac crest. To aid in cosmesis we harvest the graft through the same
midline incision as used for the repair.
Pitfalls
1. Anatomic variation.
2. Nerve root injury secondary to reduction of the neural foramen.
3. Pseudarthrosis.
4. Hardware failure.
5. Salvage requires standard posterolateral fusion.
Postoperative Care
1. Standing on the first postoperative day
2. Molded TLSO for 3 months
3. Running activities suspended for 6 months
4. Contact sports suspended for 12 months
Suggested Readings
Bradford DS, Iza J. Repair of the defect in spondylolisthesis or minimal
degree spondylolisthesis by segmental wire fixation and bone grafting.
Spine 1985;10:673–679.
Buck JE. Direct repair of the defect in spondylolisthesis. J Bone Joint Surg
Br 1970;52:432–437.
Buck JE. Further thoughts on direct repair of the defect in spondylolisthe-
sis. J Bone Joint Surg Br 1979;61:123.
Hefti F, Seelig W, Morscher E. Repair of lumbar spondylolisthesis by hook
screw. Int Orthop 1992;16:81–85.
Jakab G. The operative treatment of spondylolisthesis with compression
screws. Arch Orthop Unfall-Chir 1997;90:103–111.
Jeanneret B. Direct repair of spondylolisthesis in female gymnasts. Clin Or-
thop 1976;117:68–73.
Johnson GV,Thompson AG. The Scott wiring technique for direct repair of
lumbar spondylolisthesis. J Bone Joint Surg Br 1992;74:426–430.
Morscher E, Gerber B, Fasel J. Surgical treatment of spondylolisthesis by
bone grafting and direct stabilization of spondylosis by means of a
hook screw. Acta Orthop Trauma 1984;103;175–178.
Nachemson A. Repair of the spondylolisthetic defect and intertransversal
defect for young patients. Clin Orthop 1976;117:101–105.
Sue PB, Esses SI, Kostuik JP. Repair of pars interarticularis defect: the prog-
nostic value of pars infiltration. Spine 1991;16:S445−S448.
Tonino A, van der Werf G. Direct repair of lumbar spondylolisthesis. Acta
Orthop Scand 1994:65:91–93.
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256
SECTION III THE LUMBAR SPINE
Eurostile
Modified Scott
wire technique
Button
Button
L3
Inferior one third
facet resected
with osteotome
Drill hole in
base of
superior facet
L3
Button
Pseudoarthrosis
(debride and
place bone graft)
L4
L5
Figure 55–1
Anteroposterior diagram of modified Scott wire technique demonstrates the resection of the in-
ferior facet and placement of the wires.
L4
L5
Figure 55–2
Lateral diagram of modified Scott wire technique demonstrates the course of the wire through the facet/pedicle and
the position of the button.
AB C
Figure 55–3
Lateral (A), anteroposterior (B), and oblique (C) radiographs of a healed spondylolytic defect using the modified Scott wire technique.
Eurostile
55 SPONDYLOLYSIS REPAIR
257
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56
Decompression for Lumbar Fractures
Posterior
Behrooz A. Akbarnia
Goals of Surgical Treatment
1. The goals of surgical treatment, which are decompression, realignment, and stabilization, can be reached through this single posterior
incision.
2. To improve neurologic recovery when it is done in a timely manner
(Ciappetta et al, 1996; Clohisy et al, 1992; Dendrinos et al, 1995; Dimar
et al, 1999).
3. To stop the deterioration of neurologic function when the deficit is
progressive.
4. To restore sagittal alignment and stability.
Diagnosis
A careful clinical assessment of neurologic function is essential. Plain
radiographs and other imaging studies such as computed tomography (CT)
scan and magnetic resonance imaging (if soft tissue or disc injury is suspected) are the most helpful studies.
Indications for Surgery
Posterolateral decompression is used in the following conditions:
1. Spinal canal compression caused by bony fragments in patients de-
monstrating worsening of the neurologic deficit.
2. In patients with incomplete deficit in whom neurologic function has
reached a plateau.
3. In patients with normal neurologic function and significant canal com-
promise (more than 60 %), as well as kyphosis requiring anterior
column support to achieve spinal stability. This support is accomplished through a posterior interbody grafting.
4. In some patients with incomplete but nonprogressive neurologic defi-
cit or patients with canal encroachment but intact neurologic function,
the natural history of neurologic improvement may not be altered by
decompression.
Contraindications
1. When there is a significant comminution (McCormack et al, 1994) of
the vertebral body, loss of anterior height (more than 50 %), and kyphosis, especially in the thoracolumbar junction, the anterior approach for
decompression and structural grafting may be more appropriate.
2. Mild kyphosis, minimal comminution, no significant canal com-
promise, and no neurologic deficit.
3. Old posttraumatic kyphosis.
Advantages
1. Posterolateral approach allows decompression and stabilization to be
accomplished through a single approach.
2. It provides an alternative when anterior approach carries a higher risk,
because of patient’s general condition, associated trauma, and previous abdominal surgery.
3. It provides better visualization of the nerve roots, especially when
there is a possibility that they are entrapped in the laminar fractures.
4. In the lower lumbar spine anterior decompression and instrumenta-
tion may not be feasible because of vascular proximity, and therefore
the posterior approach may be preferable.
5. For lower lumbar spine burst fractures with neurologic deficit, post-
erolateral decompression is ideal because the spinal canal is wide and
the sagittal alignment is not significantly altered.
6. The laminar fractures and entrapment of the neural elements are also
more common in the lower lumbar spine burst fractures, which are
more accessible posteriorly. Dural tears could be repaired through this
approach.
Disadvantages
1. It is not clear whether the presence of fragments in the canal may cause
problems such as spinal stenosis at a later date.
2. Because there is no correlation between the degree of canal com-
promise and the neurologic deficit, especially in the absence of neurologic deficit, removal of bone fragments may be unnecessary (Fidler,
1988).
3. For severe kyphotic deformity requiring strut grafting, the anterior ap-
proach is more feasible.
Procedure
The posterolateral approach has been described for decompression of the
spinal canal and the removal of retropulsed fragments caused by burst fractures. These techniques have not included extensive removal of the
pedicle on a routine basis (Flesch et al, 1977; Garfin et al, 1985). It is difficult to achieve full access to the anterior and middle columns of the spine
without removing the major part of the pedicle. Therefore, the technique
described in this chapter has been developed to allow better exposure and
more effective decompression and grafting via the posterolateral approach.
Using plain radiographs, CT, and other imaging studies, as well as clinical assessment, the pedicle to be approached is selected. This is usually on
the side with the worse neurologic deficit. If neurologic deficit is the same
bilaterally or in patients with normal neurologic function, the side with
more bony fragments or with a larger degree of compression is selected.
Surgical approach through a single pedicle is sufficient in most cases. The
opposite pedicle is left intact for the purpose of instrumentation. The comminution of the opposite pedicle is determined by preoperative CT scan. It
is often possible to use this pedicle as a site of a pedicle screw. It may be
necessary to extend instrumentation if more than one level of decompression is required (Akbarnia, 1997).
If there is laminar fracture, more extensive decompression should be
planned. Intraoperative imaging may include plain radiographs, myelogram, and ultrasonography. Special instruments are required for this procedure to access the entire canal reaching the medial cortex of the opposite
pedicle (Fig. 56–1).
Technique Secrets
The patient is taken to the operating room and, depending on the stability
of the fracture, is placed over rolls or a frame of choice, with the usual precautions. Spinal cord monitoring and cell-saver techniques are used when
possible. Once the usual posterior midline approach to the spine is made,
the level of fracture and the pedicle to be decompressed are identified by
an intraoperative lateral radiograph. The following is the technique
sequence:
1. Temporary reduction and stabilization. The spine is temporarily stabi-
lized on one side by the appropriate implants to prevent unnecessary
motion during the decompression. Partial or complete reduction of the
sagittal deformity can be achieved during this stage. If pedicle screw
fixation is planned, the opposite pedicle may be used for insertion of
an additional screw for more stability (Fig. 56–2).
2. Removal of the pedicle. The pedicle to be removed is identified at the
junction of the superior articular process, lamina, and transverse
process. The transverse process is fully exposed. The entrance of the
pedicle is removed by a power drill or a rongeur and the pedicle is
probed. The lack of resistance at the burst fracture site is noted. The
base of the transverse process is then osteotomized by removing the
posterior cortex of the transverse process with a Leksell rongeur and
then the anterior cortex using a Kerrison rongeur. Once the osteotomy
is completed, the transverse process is left floating with its soft tissue
attachments.
The direction of the pedicle is verified again using a pedicle probe,
and the lateral cortex of the pedicle is identified and removed using
rongeurs. The medial and inferior wall is usually preserved. By staying
next to the cortex, injury to the segmental vessels at the waist of the
vertebral body is avoided and the nerve roots are protected. It is often
possible to preserve the inferior articular process and avoid damage to
the facet joint. If a more extensive posterior decompression is needed,
however, the inferior articular process can also be removed.
The cancellous bone of the pedicle is identified and gradually removed by enlarging the opening. Initially, a straight curet, followed by
right- and left-angled curets (Fig. 56–3), is used to provide access to the
vertebral body. The medial and inferior cortices of the pedicle are usually left intact to protect the dura during this stage of the procedure.
3. Decancellization of the vertebral body. Using special right- and leftangled curets, the cancellous bone anterior to the posterior cortex of
the vertebral body (and fragments) is gradually removed to create
space so the fragments can be reduced (Fig. 56–4). These curets are
used with two hands in a rotary motion (Fig. 56–5). The cup of the
curet always moves away from the posterior cortex and the dura. A
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258
SECTION III THE LUMBAR SPINE
Eurostile
Figure 56–1
Set of specially made long-handle instruments for posterolateral decompression.
Eurostile
56 DECOMPRESSION FOR LUMBAR FRACTURES
259
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