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FIGURE 39-4
Procedure 39 | Lumbar Internal Laminectomy 369
FIGURE 39-5
FIGURE 39-6
n
The facetectomy should also be performed in a “trumpeted” manner to preserve
the pars interarticularis and facet joint.
n
Using a high-speed burr, the facet complex is undercut to avoid destabilizing
the joint.
Step 4
n
Attention is then turned toward the contralateral side.
n
The microscope is angled toward the opposite side, and the patient can also be
tilted contralaterally to allow visualization underneath the deepest portion of
the interspinous ligament.
n
The base of the spinous process, as well as the deepest portion of the interspi-
nous ligament, is then undercut with the drill, taking care to avoid detaching
the spinous process. The base of the spinous process must be adequately undercut to achieve sufficient contralateral visualization. In many cases, the “wishbone” portion of the cephalad and caudal lamina, that is, the junction of the
lamina with the spinous process, must be resected. A high-speed burr is used
to undercut the spinous process and drill the undersurface of the contralateral
lamina (Figure 39-5).
n
Once the contralateral ligamentum flavum can be visualized adequately, a dis-
sector is used to confirm that the anterior surface of the ligamentum flavum is
free from the underlying dura. A curette is used to separate dura from ligamentum flavum (Figure 39-6).
370 Procedure 39 | Lumbar Internal Laminectomy
A
FIGURE 39-7, A-B
B
S T E P 4 P EA R L S
• In areas of tight adhesions between
ligamentum and dura, small pieces of
ligamentum flavum can be left behind.
• The removal of the ligamentum flavum
and medial facetectomies bilaterally
serves to effectively increase the
cross-sectional area of the spinal canal.
• See Figure 39-11, A and B for a
schematic and photograph, respectively,
showing the spinal canal after bilateral
decompression by unilateral
laminotomy.
FIGURE 39-8
n
The ligamentum flavum can then be removed using Kerrison rongeurs and
curettes. Figure 39-7, A is an illustration showing contralateral ligamentum
flavum being removed with Kerrison rongeurs. In Figure 39-7, B, the contralateral ligamentum flavum is being resected under the operating microscope.
n
A malleable retractor or a Penfield dissector may be placed underneath the
spinous process to protect the underlying dura and neural elements during
decompression (Figure 39-8).
n
Finally, the decompression is completed by undercutting of the contralateral
medial facet using Kerrison rongeurs until a probe can be passed freely into the
foramen. Figure 39-9 shows decompression of the contralateral lateral recess
and foramen with a Kerrison. Figure 39-10 shows use of a dental tool (also
known as a hockey stick) dissector to assess adequacy of contralateral and
lateral recess decompression.
Procedure 39 | Lumbar Internal Laminectomy 371
FIGURE 39-9
A
FIGURE 39-11, A-B
FIGURE 39-10
B
S T E P 4 P IT FA L L S
• Unintentional durotomy is perhaps the
most common complication seen with
this procedure. Any dorsal durotomy
should be repaired in a watertight
manner with suture and a collagen
overlay. The authors use fibrin glue, but
hydrogel polymers are an alternative.
• Occasionally, a durotomy occurs over a
root sleeve or is not sewable because
of an extremely thin dura. On those
occasions, the authors repair the dura
with a collagen overlay and glue
without suturing.
372 Procedure 39 | Lumbar Internal Laminectomy
Step 5
n
The wound is then copiously irrigated and hemostasis is obtained. The fascia,
subcutaneous tissue, and skin are closed sequentially in the usual fashion.
n
The placement of a subfascial or epifascial drain is per the preference of the
surgeon and the degree of hemostasis achieved.
Postoperative Care and Expected Outcomes
n
Complications associated with this procedure include infection, unintended
durotomy and possible cerebrospinal fluid leak, nerve root injury, and postoperative instability.
n
The risk of progression of instability after such a decompression has been esti-
mated at 10% to 15%.
n
In cases of spondylolisthesis or deformity, there is a higher chance of surgical
failure. Patients should be counseled about this preoperatively.
Evidence
Adams M, Hutton W, Stott J. The resistance to flexion of the lumbar intervertebral
joint. Spine 1980;5:245-53.
Oertel M, Ryang Y, Korinth M, et al. Long-term results of microsurgical treatment
of lumbar spinal stenosis by unilateral laminotomy for bilateral decompression.
Neurosurgery 2006;59:1264-9.
This study presented long-term results after unilateral laminotomy for bilateral
decompression. In a series of 102 patients available for long-term follow-up
(mean, 5.6 years), 92.2% of the patients remained improved. Repeat surgery for
restenosis was necessary in 7 patients and for spinal instability in 2 patients.
Orpen N, Corner J, Shetty R, et al. Micro-decompression for lumbar spinal stenosis:
the early outcome using a modified surgical technique. J Bone Joint Surg Br
2010;92:550-4.
There was an overall success rate of 87.9% using this technique among 374
patients, with an overall complication rate of 2.41%. The authors experienced
five cases of unintentional durotomies. In addition, they observed a 0.8% rate
of postoperative instability, as documented on flexion/extension studies.
Spetzger U, Bertalanffy H, Reinges M, et al. Unilateral laminotomy for bilateral
decompression of lumbar spinal stenosis. Part II: clinical experiences. Acta
Neurochirugica 1997;139:397-403.
This series included 29 patients who underwent a bilateral decompression
through a unilateral laminotomy. Twenty-five patients were followed up after a
mean period of 18 months. Of these patients, 88% reported having excellent or
good overall postoperative outcomes, and 80% reported complete resolution or
improved low back pain. Neurogenic claudication improved in all patients. An
inadvertent dural tear occurred in one patient. Morphometric studies showed
an increase in the cross-sectional area of the dural sac, as well as increase in
the interfacet diameter after surgery. In those patients with preoperative
degenerative spondylolisthesis, no further deterioration occurred during the
follow-up period.
Weiner B, Walker M, Brower R, McCulloch JA. Microdecompression for lumbar
spinal canal stenosis. Spine 1999;24:2268-72.
This is an excellent technical article on this technique. Outcomes were reported
on 30 patients, with 26 patients having good to excellent outcomes.
P R O C ED U R E 4 0
Minimally Invasive Presacral
Retroperitoneal Approach
for Lumbosacral
Axial Instrumentation
Zachary A. Smith, Murat Cosar, Ian T. Johnson,
Daniel Raphael, and Larry T. Khoo
Introduction
n
Lumbar fusion is a frequently used technique to treat spinal disorders, including
symptomatic instability resulting from traumatic and iatrogenic causes, stenosis,
spondylolisthesis, and scoliosis. Traditional anterior or posterior approaches are
chosen for direct exposure of the lumbosacral spine. These traditional approaches
are often poorly tolerated by patients, because they require significant muscle
dissection and retraction, ligamentous disruption, osseous stripping, neural
retraction, annular disruption, sympathetic dysfunction, and bowel injury and
the additional risk of vascular injury with anterior approaches. In addition, traditional anterior spinal approaches place the abdominal viscera, ureters, retroperitoneal structures, sympathetic plexi, and great vessels at risk. The advent of
minimally invasive spinal surgical techniques has allowed surgeons to perform
interbody fusion and screw placement with less pain, less damage to muscles,
decreased blood loss, improved postoperative length of stay, and fewer medications than open surgery.
n
Degenerative disease of the lumbar disk space frequently affects the anterior
column of the lower lumbosacral spine, because normal loading of the lumbar
spine directs more than 80% of the axial load over the anterior column in the
lower levels. As such, traditional open fusion treatment of spinal instability and
back pain at the L4-5 and L5-S1 segments is extremely common. Because of
the potential risks of open surgical approaches, technological advances using
small incisions and portals have allowed surgeons to perform lumbosacral fusion
by posterolateral or anterior approaches through less invasive and tissue-sparing
techniques. Recently, a soft tissue–sparing minimally invasive approach to the
axial lumbosacral spine has been developed.
Indications
n
Degenerative disk disease
n
Pseudarthrosis
n
Postlaminectomy instability
n
Spondylolisthesis (grade 1 or 2)
n
Unsuccessful previous fusion
374 Procedure 40 | Minimally Invasive Presacral Retroperitoneal Approach for Lumbosacral Axial Instrumentation
Contraindications
n
Spondylolisthesis (grade 3 and 4)
n
Pararectal infection
n
Exceptional patient body habitus
n
Prior rectal surgery
n
Rectal fistulas
n
E X A M IN AT I ON / I M A GI N G
P I T F A L L S
• Patient selection is critical to avoid
lumbosacral anatomic configurations
that do not allow safe access and/or
cage placement. These include
• Hypercurved sacrums
• Unreduced grade 1 or higher
spondylolisthesis
• Overly flat sacrums and cases where
there is severe inflammation,
adhesion, or scarring of the presacral
retroperitoneal fat pad
• Prior surgical conditions, as well as
postinflammatory changes may result in
scarring that may make dissection
difficult and dangerous. Such scarring
and inflammatory tissue may adhere
the rectum, colon, ureter, and vascular
structures to the sacral face, making
blunt dissection difficult and riskier.
T R E A T M E N T OP T I O N S
• Posterolateral fusion
• Transforaminal lumbar interbody fusion
• Posterior lumbar interbody fusion
• Anterior lumbar interbody fusion
Scarring of the presacral area
Examination/Imaging
n
The presacral anterior retroperitoneal approach requires dissection between the
layers of the Waldeyer fascia for safe access into the S1-2 junction of the sacrum.
n
Preoperative imaging, including long-cassette radiograph views that visualize
L4 to the sacral coccygeal tip, are essential in this preoperative planning process.
n
In addition, taking careful histories to identify conditions that may have resulted
in presacral scarring, combined with appropriate magnetic resonance imaging
(MRI) and/or computed tomography (CT) imaging to exclude such patients, is
equally important.
n
A careful screening during history taking is essential to identify patients with a
history of prior pelvic surgery, pelvic trauma, pelvic inflammatory disease, perianal infections, or other conditions that may have resulted in adhesions within
the presacral space, which may affect the perineal fat pad as well as the
Waldeyer fascia. In addition, a long sagittal-view CT scan with contrast or MRI
of the pelvis to visualize the extent of the presacral fat pad can be used to
exclude such adhesions of tubular structures preoperatively.
n
At the transsacral interbody, titanium construct requires solid intravertebral fixa-
tion; it is critical to identify preoperative focal osteopenia or osteoporosis in the
L5 and L4 vertebral bodies or sacrum, depending on the levels targeted for fixation. Focal bone density scans can now be obtained that can identify focal
significant bone loss, in these areas, that may make adequate bony fixation
difficult and increase the risk of significant subsidence and/or early implant
migration.
Surgical Anatomy
n
Neural structures in the presacral space include the hypogastric nerves 1 cm
lateral to the midline at the sacral promontory, parasympathetic nerves that arise
from the ventral roots of S3-4 in the male and S2-4 in the female. Although the
hypogastric nerves are located several centimeters laterally at S1-2, the surgeon
must be careful to avoid damage to these neural structures.
n
Vascular structures in the presacral space are the middle sacral artery and veins.
Bleeding from the transverse sacral vein or the midline sacral artery is also possible, but at S2, the midline sacral artery is often small or nonexistent. The risk
of venous bleeding is low, because the technique begins with sweeping the soft
tissues off the sacrum with a blunt dilator.
n
The AxiaLif (TranS1, Wilmington, N.C.) system combines the advantages of
minimal invasive spinal surgical techniques with a novel corridor of approach.
A trocar is advanced through a 2-cm paracoccygeal incision along the anterior
surface of the sacrum, using biplanar fluoroscopy, until a proper trajectory in
the center of the L5-S1 intervertebral space is obtained. This minimally invasive
approach to the lumbosacral spine also preserves the integrity of the muscles,
ligaments, blood vessels, and disk annulus.
Procedure 40 | Minimally Invasive Presacral Retroperitoneal Approach for Lumbosacral Axial Instrumentation 375
n
Ready access can be gained to the disk space through the naturally existing
presacral fat pad, while avoiding the anterior abdominopelvic cavity, great
vessels, neural elements, facets, lamina, and the dorsal musculoligamentous
complex completely. Significant segmental stiffness is immediately afforded by
distraction across the disk space. Because the ligaments and annulus are completely intact, this provides the strongest possible ligamentotaxis, thereby affording the best interbody fusion construct stiffness.
n
In addition, an important advantage is that there is no need for retraction of
the vascular or neural elements to place the prosthesis, because the size is
limited only by the diameter of the working portal. As distraction is achieved by
the differential screw pitch at the ends of the cage, a wide variety of distraction
heights can be obtained by simply altering the design of the implant. When
combined with percutaneous pedicle screw instrumentation system, additional
distraction, compression, and reduction maneuvers can also be applied to the
spine, as needed, before threading the cage across the interspace. Similar to
transsacral fibular dowel struts in the stabilization of high-grade isthmic spondylolisthesis, axially placed cages, such as the AxiaLif transsacral cage, provide
excellent resistance to shear, translation, flexion, and extension that is far superior to traditional interbody constructs.
n
This paracoccygeal, transsacral approach to the L5-S1 interspace allows the
surgeon to perform a near-total diskectomy without violation of the annulus or
surrounding ligaments, thereby significantly increasing the stiffness of the
motion segment with distraction. In addition, this leaves the area around the
disk, great vessels, and neural elements untouched and thus free of surgical
scarring, which is beneficial, given that future operations may require revision
or surgery at an adjacent level. Recent advances in this technique now allow
the surgeon to extend the fusion to include the L4-S1 interspace and extend
the fusion from L4 to S1. The development of this technology allows an expansion to the applications and indications for this technique.
P O S I TI O N I N G PE A R L S
• Intraoperative electromyography
(EMG) and/or somatosensory evoked
potentials (SSEPs) may be used for
neurophysiologic monitoring of neural
integrity during decompression,
interbody distraction, and screw
placement.
Positioning
n
A standard setup for posterior lumbar surgery is used, with the spine surgeon
standing on the left or right side of the patient with an operation technician
and a surgical assistant. The C-arm and monitor is placed according to the
position of the surgeon (Figure 40-1, A and B).
n
The patient is positioned, under general anesthesia, prone on a suitable radio-
lucent spine operative table (Figure 40-1, C ).
n
A 20-Fr catheter may be inserted into the rectum, and the balloon is insufflated
with 10 to 12 mL of air to provide visualization of the rectum and to minimize
the risk of bowel injury during the process under lateral fluoroscopy.
n
The anus is covered with an occlusive dressing to separate it from the paracoc-
cygeal working area, which is more dorsal. A fluoroscopic C-arm is located in
the surgical field to provide real-time lateral and anteroposterior (AP) imaging.
The operation area is then washed and draped in the usual sterile fashion.
376 Procedure 40 | Minimally Invasive Presacral Retroperitoneal Approach for Lumbosacral Axial Instrumentation
Anesthesia
machines
Scrub nurse
Neurosurgeon
A
EMG
FIGURE 40-1, A-C
P O S I TI O N I N G PI T FA L L S
• During preoperative bowel preparation,
24 hours before surgery, the authors
allow the colon and rectum to be
empty, thereby mitigating the effects of
accidental viscus or bowel perforation.
This approach, combined with use of
appropriate intraluminal antibiotics,
such as Flagyl, and gram-negative
coverage, such as gentamicin, in
addition to usual gram-positive
coverage, is also prudent.
• During patient positioning, the use of
a radiolucent table, as well as highquality intraoperative imaging, is
essential before the procedure is
completely percutaneous and managed
with fluoroscopy without use of any
direct visualization. Similarly, the legs
and thighs must be separated with
rolls to allow the access instruments
that typically must be placed initially
between the thighs to achieve the
appropriate angle of approach in the
presacral space.
Monitor
B
C-arm
Assistant
C
P O S I TI O N I N G EQ U I P M EN T
• Several items of equipment are needed
to perform a transsacral AxiaLif fusion.
• First, the draped C-arm fluoroscopy and
monitor are essential for verifying the
position and localization of the patient
during surgery.
• The transsacral AxiaLif set is necessary
to perform the operation.
• Standard posterior lumbar minimal
invasive surgery instruments are
essential for the operation.
• Figure 40-2 shows the AxiaLif
instrumentation set: guide pin, serial
dilators, and other equipment used in
the procedure (see Figure 40-2, A).
Also used are cutting-loop devices and
disk extractors (see Figure 40-2, B), a
special wire brush–type capture device
(see Figure 40-2, C ), and the 3D-Axial
Rod prosthetic device (AxiaLif cage)
(Figure 40-2, D).
Procedure 40 | Minimally Invasive Presacral Retroperitoneal Approach for Lumbosacral Axial Instrumentation 377
A
C
FIGURE 40-2, A-D
B
D
378 Procedure 40 | Minimally Invasive Presacral Retroperitoneal Approach for Lumbosacral Axial Instrumentation
S T E P 1 P EA R L S
• Initial use of the finger dissection in the
presacral space anterior to the coccyx
is an excellent technique to begin to
separate the layers of the fascia and
mobilize the retroperitoneal fat
anteriorly. This is preferred, because
it is less traumatic and potentially
dangerous and uses sharp dissection in
this area. After generous separation of
the layers with the finger, the blunt
probe could then be used to continue
the dissection up to the S1-2 junction.
• Frequent use of biplanar fluoroscopic
guidance to confirm the trajectory
and angle of the initial Steinmann pin,
guide pin, and various instruments
are essential to avoid displacement
of the implant as well as to avoid
dislodgement of the working cannulas
from the safe bony corridor within the
sacrum.
Procedure
Step 1
n
A 15- to 20-mm incision is made 20 mm caudal to the left or right paracoccygeal
notch after giving local anesthesia (Figure 40-3).
n
Finger dissection may be used to ensure that the fascia is appropriately opened.
n
The guide pin introducer/stylet assembly is inserted into the incision at a suitable
angle (Figure 40-4, A) and slowly advanced along the anterior midline of the
sacrum to sweep the abdominal contents anteriorly under frequent biplanar
fluoroscopic control. Lateral fluoroscopy images (Figure 40-4, B-D) confirm
appropriate advancement along the ventral surface of the sacrum.
• Direct tactile feedback is obtained from the stylet to control continuous bony
contact of the introducer tip.
Paracoccygeal
notch
X
A
Paracoccygeal
notch
B
FIGURE 40-3, A-B
X
Incision
X