Добавил:
Sekretar
kiopkiopkiop18@yandex.ru
t.me/Prokururor I Вовсе не секретарь, но почту проверяю
Опубликованный материал нарушает ваши авторские права? Сообщите нам.
Вуз:
Предмет:
Файл:Ординатура / Хирургия / Библиотека им академика М.И. Перельмана / Книга_6012_Библиотеки_им_академика_М_И_Перельмана.pdf
Chapter 20 Lateral and Posterior Approaches to the Lumbosacral Spine 363
A
B
FIG. 20.15 (A) Exposure of the lumbar disc by retracting the thecal sac medially. (B) View of microdiscectomy
under a microscope. The thecal sac is retracted medially by a nerve root retractor. ((A, From Benzel E. Spine
Surgery: Techniques, Complication Avoidance, and Management. Philadelphia: Churchill Livingstone; 2004.)
SECTION
III
FIG. 20.16 Structures relative to the pedicle.
medially (Fig. 20.15). Care must be used not to retract too
vigorously to avoid too much tension on the exiting nerve
root. Bleeding from the epidural veins commonly occurs.
Hemostasis can be obtained with bipolar cautery and/or the
use of cottonoids, Surgicel, and thrombin-soaked Gelfoam.
Cottonoids can be placed in the cephalad and caudal extremes
of the exposure to collapse the vessels and provide a working
window. e key to intracanal anatomy is the pedicle (Fig.
20.16). e disc space is just cephalad to the pedicle, and the
intervertebral foramen above the pedicle accommodates the
exiting nerve root. e traversing nerve root lies just medial
to the pedicle and exits the intervertebral foramen caudally.
e disc space can be found by retracting the traversing nerve
root medially and exploring the space above the pedicle. Feel
for the disc space with a Peneld 4. It should be a raised, white,
so structure.
If a total laminectomy is needed to decompress or expose
the dura and nerve roots, remove the fascia entirely from the
tip of the spinous process bilaterally. Dissect the muscles o
of the spinous processes and lamina subperiosteally and take
care to protect the facet joints. e pars interarticularis must
FIG. 20.17 Axial magnetic resonance image of the lumbar spine. The arrow
is pointing to the lateral recess.
be exposed fully to avoid transecting it during the decompression. A rongeur can be used to remove the spinous processes.
e laminectomy may be performed many ways. A high-speed
burr may be used to thin the lamina down to a thin cortical
shell over the dura and then removed with a Kerrison rongeur.
Alternatively, the tip of a rongeur may be inserted under the
caudal edge of the cephalad lamina to remove the lamina. Use
the rongeur to cut from the underside in an upward direction.
is will lessen the chance of catching dura. A Kerrison rongeur
can be used to complete the laminectomy near the pars and
the cephalad edge. To adequately decompress the nerve roots,
the lateral recesses and intervertebral foramen must also be
explored (Fig. 20.17). A Woodson elevator or dural guide may
be used to gently compress the dura and expose the lateral
recesses. is will expose the ligamentum avum in the lateral
recess and intervertebral foramen. is ligamentum avum
should be removed to perform an adequate decompression.
e medial aspect of the caudal pedicle marks the medial
364 SURGICAL ANATOMY AND APPROACHES
Pedicle
border of the intervertebral foramen. Oen, osteophytes from
the facet joints compress the exiting nerve root. Care must be
taken when removing these osteophytes to avoid injury to the
exiting nerve root and to avoid iatrogenic instability caused
by too much removal of the facet joint. Typically, removal of
less than 50% of the facet joint will preserve its stability. is
may necessitate the use of a 1- or 2-mm Kerrison rongeur.
e use of curved Kerrison rongeurs can be helpful here.
Bearing in mind that the facet joints are oriented sagittal in
the lumbar spine, cutting the undersurface of the facet joint
provides a greater means of decompressing the nerve roots
while preserving the overall stability of the joint.
With the advent of pedicle screw xation for the lumbar
vertebrae, there are now several additional anatomic relationships that are of importance at the level of the posterior bony
elements. e location of the pedicles is identied by anatomic
landmarks and by radiography or image-intensication uo-
roscopy in the operating room.
In the lumbar region, the center of the pedicles is usually
at the inferolateral edge of the facet joint, on an imaginary
transverse line bisecting the transverse processes (Fig. 20.18).
However, if there is severe facet arthrosis, the lateral edge of
the facet joint may be lateral to the true pedicle entry site. In
these cases, also refer to the pars interarticularis. e lateral
border of the pars typically corresponds to the medial border
of the pedicle. In the lumbar region, from this point, one may
use a pedicle nder, with a 20-degree medial inclination at L5,
10 degrees at L4, 5 degrees at L3 and L2, and no inclination at
L1 (Fig. 20.19). One may follow the progress of the pedicle
nder by feeling inside the pedicle with a pedicle feeler and
by checking with the image intensier or by radiographs. In
the lateral view, the probe/marker should be parallel to the
disc space.
Posterolateral Approach to the Lumbar Vertebral Bodies
e posterolateral approach provides direct access to the transverse processes and the mammillary processes of the facets
through a longitudinal paraspinal incision, retracting the erector
spinae muscles medially. is area provides an excellent bed for
posterolateral lumbosacral fusion even in the face of preexisting pseudarthrosis, laminar defects, or spondylolisthesis. is
approach is the basis for minimally invasive transforaminal
lumbar interbody fusions.
Technique
General endotracheal anesthesia is recommended for this
procedure. e patient is placed on the operating table in the
prone position with chest rolls on either side of the thorax to
protect ventilation or on a radiolucent table with chest and
hip pads.
A longitudinal paramedian incision is made at the lateral
border of the erector spinae muscles (approximately 2 ngerbreadths from the midline) centered over the level of interest.
e incision is extended to the lumbar fascia, and the erector
spinae muscles are identied. e interval between the erector
spinae muscles and the multidus is found aer opening the
fascia, and dissection proceeds between these muscles down
to the facet joints and the transverse processes of the vertebrae
(Fig. 20.20). e paraspinal muscles are retracted medially, the
transverse process at the desired level is tagged with a radiopaque
marker, and radiographs are made to conrm the vertebral level.
For a minimally invasive transforaminal interbody fusion, this
exposure is adequate to perform a decompression and fusion.
If access to the vertebral body is desired, the dissection can
be carried further anteriorly. e transverse process is divided
with an osteotome and is retracted laterally with its musculotendinous attachments. e vertebral pedicle is palpated, and
the lumbar nerves are identied and protected as they leave
their foramina above and below the pedicle (Fig. 20.21). e
psoas muscle is carefully separated from the vertebra using a
Pedicle
5°
L4 L5
10°
FIG. 20.19 Transaxial position of the pedicle screws. FIG. 20.18 Pedicle entry points.
5°
20°
Chapter 20 Lateral and Posterior Approaches to the Lumbosacral Spine 365
communicans
Vertebral body L4
muscle
FIG. 20.20 Cross-section of the lumbar spine and paraspinal structures at
the level of the third lumbar vertebra. The arrows point to the interval
between the erector spinae muscles and the multidus.
Elevated psoas
muscle from vertebra
Posterior ramus
lumbar artery
Intervertebral
foramen
Erector spinae
muscle
FIG. 20.21 Lumbar vertebrae as viewed from the posterolateral approach.
The dissection proceeds directly anterior to the stump of the transverse
process, along the pedicle of the vertebral body in front. Note the lumbar
segmental vessels draped over the waist or midportion of the vertebral
bodies. By dissecting directly anterior to the pedicles, one can avoid these
vessels as well as the lumbar nerves leaving the neural foramina below the
pedicles.
Divided transverse
process
Ramus
Pedicle
Lumbar artery
Anterior ramus
lumbar nerve
periosteal elevator. e lumbar vessels lie on the waist or midportion of the vertebral body posterior to the psoas muscle
and should be separated from the body during this portion
of the dissection. ey may be clamped and cauterized, if
necessary. An opening may be made in the lateral aspect of
the vertebral body anterior to the pedicle, using a curette or
drill (Fig. 20.22). e lesion may be identied grossly at this
time, but should be veried radiographically with a curette
placed within the lesion. rough this approach, specimens
may be obtained from the lateral, central, or anterior aspect
of the vertebral body or pedicle. e lesion may be curetted,
and small chips of cancellous bone gra may be installed to
stimulate osteogenesis within a sterile defect. e wound is
Quadratus
lumborum
muscle
Erector spinae
FIG. 20.22 Posterolateral approach to the lumbar vertebrae, lateral to the
erector spinae muscle mass and behind the psoas. The transverse process is
divided and retracted laterally with its musculotendinous insertions to gain
access to the lateral aspect of the vertebral body.
copiously irrigated with saline and inspected for hemorrhage.
e margins are allowed to fall together, and the lumbar fascia
is closed with interrupted sutures. e skin is repaired, and the
patient is nursed with some form of external spinal support,
depending on the postoperative stability of the spine.
PEARLS
For lateral interbody fusions, it is often easier to adjust the table
1.
to get the perfect AP and lateral, and just have the C-arm rotate
between 0 degrees and 90 degrees.
2.
For lateral interbody fusions, take frequent images to ensure
good position. Since you are using a smaller incision and thus
see less, you must rely on imaging more to make sure that you
are in the right position.
3.
For lateral interbody fusions, study the MRI preoperatively to get
an idea of where the nerves are. If the neuromonitor shows that
the nerve is in the eld, be prepared to convert to another form
of interbody fusion.
4.
To adequately decompress the nerve roots, the lateral recesses
and intervertebral foramen must also be explored.
PITFALLS
For lateral interbody fusions, aggressive deployment of the
1.
retractor or repeated passes with the initial dilator may injure
the nerve.
2.
For lumbar decompressions, be careful about removing too
much of the pars or facet joints to avoid iatrogenic instability.
3.
When placing pedicle screws, if there is severe facet arthrosis,
the lateral edge of the facet joint may be lateral to the true
pedicle entry site.
KEY POINTS
1. Lateral interbody fusion is a good technique for correction of
degenerative scoliosis, multilevel fusions, or adjacent segment
degeneration. This can be done in a minimally invasive fashion
that will improve recovery while maximizing results.
2.
Since the lateral approach to the spine requires traversing the
psoas, neuromonitoring is required to decrease the risk of nerve
injury. Also, since the incision is smaller and less tissue dissection
is done, there is a greater reliance on imaging.
3.
The posterior approach to the lumbar spine is commonly used
for microdiscectomies and lumbar decompressions.
SECTION
III
366 SURGICAL ANATOMY AND APPROACHES
4. The key to intracanal anatomy is the pedicle. The disc space is
just cephalad to the pedicle, and the intervertebral foramen
above the pedicle accommodates the exiting nerve root. The
traversing nerve root lies just medial to the pedicle and exits the
intervertebral foramen caudally.
5.
The posterolateral approach provides direct access to the
transverse processes and the mammillary processes of the
facets through a longitudinal paraspinal incision, retracting the
erector spinae muscles medially. This is a muscle-splitting
approach and is the basis for minimally invasive transforaminal
lumbar interbody fusions.
KEY REFERENCES
1. Bateman DK, Millhouse PW, Shahi N, et al. Anterior lumbar spine
surgery: a systematic review and meta-analysis of associated
complications. Spine J. 2015;15(5):1118-1132.
2.
Rodgers WB, Gerber EJ, Patterson JR. Intraoperative and early
postoperative complications in extreme lateral interbody fusion
(XLIF): an analysis of 600 cases. Spine. 2011;36(1):26-32.
3.
Isaacs RE, Hyde J, Goodrich JA, et al. A prospective,
nonrandomized, multicenter evaluation of extreme lateral
interbody fusion for the treatment of adult degenerative
scoliosis: perioperative outcomes and complications. Spine.
2010;35(suppl 26):S322-S330.
4.
Alimi M, Hofstetter CP, Cong GT, et al. Radiological and clinical
outcomes following extreme lateral interbody fusion. J
Neurosurg Spine. 2014;20(6):623-635.
5.
Patel AA, Zfass-Mendez M, Lebwohl NH, et al. Minimally Invasive
versus open lumbar fusion: a comparison of blood loss, surgical
complications, and hospital course. Iowa Orthop J.
2015;35:130-134.
6.
Ozgur BM, Aryan HE, Pimenta L, et al. Extreme Lateral Interbody
Fusion (XLIF): a novel surgical technique for anterior lumbar
interbody fusion. Spine J. 2006;6(4):435-443.
REFERENCES
1. Bateman DK, Millhouse PW, Shahi N, et al. Anterior lumbar
spine surgery: a systematic review and meta-analysis of
associated complications. Spine J. 2015;15(5):1118-1132.
2. Lindley EM, McBeth ZL, Henry SE, et al. Retrograde
ejaculation aer anterior lumbar spine surgery. Spine.
2012;37(20):1785-1789.
3. Jarrett CD, Heller JG, Tsai L. Anterior exposure of the lumbar
spine with and without an “access surgeon”: morbidity
analysis of 265 consecutive cases. J Spinal Disord Tech.
2009;22(8):559-564.
4. Rodgers WB, Gerber EJ, Patterson JR. Intraoperative and early
postoperative complications in extreme lateral interbody fusion
(XLIF): an analysis of 600 cases. Spine. 2011;36(1):26-32.
5. Isaacs RE, Hyde J, Goodrich JA, et al. A prospective,
nonrandomized, multicenter evaluation of extreme lateral
interbody fusion for the treatment of adult degenerative
scoliosis: perioperative outcomes and complications. Spine.
2010;35(suppl 26):S322-S330.
6. Alimi M, Hofstetter CP, Cong GT, et al. Radiological and
clinical outcomes following extreme lateral interbody fusion.
J Neurosurg Spine. 2014;20(6):623-635.
7. Patel AA, Zfass-Mendez M, Lebwohl NH, et al. Minimally
invasive versus open lumbar fusion: a comparison of blood
loss, surgical complications, and hospital course. Iowa Orthop J.
2015;35:130-134.
8. Phan K, Rao PJ, Kam AC, et al. Minimally invasive versus
open transforaminal lumbar interbody fusion for treatment
of degenerative lumbar disease: systematic review and
meta-analysis. Eur Spine J. 2015;24(5):1017-1030.
9. Ozgur BM, Aryan HE, Pimenta L, et al. Extreme Lateral
Interbody Fusion (XLIF): a novel surgical technique for
anterior lumbar interbody fusion. Spine J. 2006;6(4):435-443.
10. Pumberger M, Hughes AP, Huang RR, et al. Neurologic
decit following lateral lumbar interbody fusion. Eur Spine J.
2012;21(6):1192-1199.
11. Houten JK, Alexandre LC, Nasser R, et al. Nerve injury during
the transpsoas approach for lumbar fusion. J Neurosurg Spine.
2011;15(3):280-284.
12. Cummock MD, Vanni S, Levi AD, et al. An analysis of
postoperative thigh symptoms aer minimally invasive
transpsoas lumbar interbody fusion. J Neurosurg Spine.
2011;15:11-18.
13. Balsano M, Carlucci S, Ose M, et al. A case report of a rare
complication of bowel perforation in extreme lateral interbody
fusion. Eur Spine J. 2015;24(suppl 3):405-408.
SECTION
21
Lateral Lumbar Interbody Fusion
CHAPTER
History
A variety of approaches to the interbody space exist to surgically
manage pathologies of the lumbar spine.1 e advantage of inter-
body fusions over posterolateral fusions are superiority in fusion
rates as well as segmental coronal and sagittal correction.
Open anterolateral thoracolumbar approaches have been
associated with vascular/bowel injury, abdominal hernia, ileus,
and retrograde ejaculation.5 However, the minimally invasive
lateral retroperitoneal transpsoas approach has minimized these
approach-related complications.
are associated with signicant infection rates, blood loss, opera-
tive time, length of hospital stay, prolonged recovery, and delayed
return to work due to procedural morbidity.
Following instrumentation advances in visualization, lighting technology, and specialized surgical instruments t for
smaller incisions, minimally invasive surgery (MIS) became
progressively more popular. Aer Obenchain et al. described
a laparoscopic approach to anterior lumbar interbody fusion
(ALIF) in 1991, MIS techniques to the spine began to rapidly
6,9
evolve.
of the minimally invasive lateral retroperitoneal transpsoas
approach for lateral lumbar interbody fusions (LLIFs) in
2001.6 However, Harmon described the approach in 1963.
MIS approaches such as LLIFs were developed for several
reasons, including the ability to meet increasing patient
demands and expectations for shorter hospital stays, earlier
return to work, improved cosmesis, and decreased postoperative pain.
requires access to the interbody space from the mid to upper
thoracic spine (e.g., T6, occasionally T5) through L4–L5. e
lateral approach is possibly best suited for levels L2 to L4 due
to anatomic considerations (the 12th rib and iliac crest).
Pimenta has been given credit for being the creator
12–14
Last, LLIFs can be used for any condition that
6,7
Open posterior approaches
8
Indications
2–4
10,11
Sina Pourtaheri
R. Todd Allen
John Attenello
Steven R. Garn
tilt/lateral-listhesis, atback, and long adult thoracolumbar
12,15–17
fusions.
over posterolateral fusions due to the mechanical and biologic
advantage of the interbody space.
is under compression and load sharing while having a large
surface area.
tension, has muscle creep, and has limited surface area.
erefore, interbody fusion is indicated for pseudarthrosis following posterolateral fusion. Furthermore, multilevel posterolateral lumbar fusions have signicantly high pseudarthrosis
rates compared to interbody fusions.
fusions have a relative indication for interbody fusion.
Interbody fusions provide superior fusion rates
18–24
e interbody space
18–24
However, the posterolateral space is under
25,26
erefore, multilevel
Advantages
LLIF and ALIF have superior fusion rates over TLIF due to
mechanical and biologic factors: a more thorough discectomy
and large surface area of gra extending to the apophyseal ring
bilaterally.
indirect decompression, ALIF, TLIF, and LLIF provide sig-
nicant height restoration compared to posterolateral fusion,
with LLIF and ALIF providing superior height restoration.
In regard to coronal tilt and lateral-listhesis, LLIF and TLIF
are superior to ALIF and posterolateral fusions.
regard to lumbar lordosis, ALIF and LLIF are superior to
TLIF.
shorter operative time, decreased blood loss, shorter length
of stay, and shorter time to return to work compared to open
TLIF.
compared to ALIF.
an anterior column reconstruction or release (ACR), which
can achieve similar lordosis correction as pedicle subtraction
osteotomy.
and are not applicable for xed sagittal imbalance.
18–24
In regard to foraminal height restoration and
36,42,43
In regard to morbidity, ALIF and LLIF provide
12,44,45
Furthermore, LLIFs minimize ileus-related issues
49,50
41,46-48
Last, LLIF allows for the option of
One caveat is that ACRs require a mobile disc
36–41
18–24
27–35
In
III
Absolute indication for interbody fusion (ALIF, posterior
lumbar interbody fusion [PLIF], transforaminal lumbar interbody fusion [TLIF], LLIF) is the treatment of pseudarthro-
12,15–17
sis.
Relative indications are foraminal height loss, coronal
Contraindications
L5–S1 interspace is a relative contraindication to LLIF since
the iliac wing precludes access to the disc space. L4–L5 may
367
368 SURGICAL ANATOMY AND APPROACHES
also occasionally be obstructed by the iliac crest and a lumbarized sacrum has been described as a relative contraindication
to this approach.51 e more caudal levels carry a higher risk
of injury to iliac vasculature and lumbar plexus because the
lumbar plexus begins to course more anteriorly and the iliac
vasculature more laterally.41 In most cases, access to L5–S1 is
limited by a high lateral ilium, anterior course of the neural
elements over the lateral disc at that level, and/or the vasculature. Uncommonly, L5–S1 may be approached when the
intercrestal line transects the mid to lower L5 body or the
L5–S1 disc. Rostrally, the 12th rib may obstruct access from
T12 to L2, which may require rib excision or manipulation.
Other contraindications to LLIF include bilateral retroperitoneal scarring from prior approaches (e.g., nephrectomy,
retroperitoneal abscess and subsequent scarring), high-grade
spondylolisthesis, and pregnancy.
47,52,53
In high-grade spondylolisthesis, the more anterior exiting nerve root is horizontalized and creates diculty in the placement of even the smallest
interbody gra.
LLIF may also be potentially contraindicated if direct
decompression is required, such as with congenital stenosis,
large posterior osteophytes, severe facet hypertrophy with
lateral recess stenosis, sequestered disc, and radiculopathy that
persists in exion.
27
Special consideration should be taken with stand-alone
LLIF without posterior instrumentation since lateral xation
alone may not provide sucient stabilization.54 Stand-alone
LLIF may be contraindicated at levels under high biomechanical stress such as isthmic spondylolisthesis, osteoporosis, or
adjacent fusion.54 Levels at the apex of deformity or associated
pars fracture may require posterior instrumentation.
54
FIG. 21.1 Lateral decubitus positioning for lateral lumbar interbody fusion
to minimize upper and lower extremity neurapraxia and proper taping
technique of the iliac crest (A), chest (B), greater trochanter (C), and leg (D)
to secure the patient to the operating room bed.
Technique
LLIF is a lateral approach to the intervertebral disc space
and/or vertebral body through a less invasive (or minimally
invasive), retroperitoneal-transpsoas approach. e patient is
positioned in the lateral decubitus position, typically le side
up, with axillary roll in place and moderate-sized “sticky”
rolls for anterior and posterior stabilization (Fig. 21.1).
Patients are taped carefully; at times, the table may be bent
to level the iliac crest away from the disc space. Orthogonal,
anteroposterior, and then lateral uoroscopic images are taken
(Fig. 21.2). e vertebral bodies and disc spaces are marked
supercially on the skin under uoroscopy to determine the
appropriate direct lateral incision. A second, posterolateral,
1.5- to 2.0-cm incision is made just above the pelvis within
one ngerbreadth length from the direct lateral incision (Fig.
21.3). e trajectory of this posterolateral incision is lateral to
the paraspinal muscles and medial to the oblique muscles in
an avascular plane to enter the retroperitoneal space (see Fig.
21.3). e posterolateral incision allows the surgeon to enter
the retroperitoneal space safely from a posterior approach by
starting behind the transverse process and marching anteriorly to the psoas (see Fig. 21.3). e purpose of this incision
is to avoid entering into the peritoneum when going from the
direct lateral approach, thus preventing an inadvertent bowel
FIG. 21.2 Breaking of the operating room bed to position the iliac crest
away for L4–L5 access and even L5–S1 with angled instruments.
injury. Once your nger is on the psoas, bring the index nger
to the deep surface of the oblique muscles to determine the
safe trajectory of the direct lateral approach (Fig. 21.4). With
the lateral skin incision marking, center it over where you
palpate your nger in the retroperitoneal space. Develop the
lateral approach dissection to the external oblique muscle.
Again, check the trajectory through the oblique muscles by
bringing your nger in the retroperitoneal space to the psoas;
Chapter 21 Lateral Lumbar Interbody Fusion 369
FIG. 21.3 The posterolateral incision allows for a safe trajectory with the direct lateral approach through the
retroperitoneal space to prevent bowel injury.
SECTION
III
FIG. 21.4 From the posterolateral incision, palpate the psoas and bring the index nger to the undersurface of
the abdominal wall to guide the trajectory of the initial dilator safely away from the bowel.
then, go directly vertical from there to the undersurface of the
oblique muscle (see Fig. 21.4). Allow your nger to sweep the
retroperitoneal fat anteriorly for a safer corridor. Blunt dissection through the oblique muscles and transverse abdominal
fascia is made with two Kocher clamps at the same time. e
Kocher clamps spread in opposite directions of each other to
develop the plane through the muscles in line with their bers
to avoid segmental innervation disruption of the muscles and
subsequent pseudohernia. rough this passage hole, place
the rst dilator (see Fig. 21.4). Let the nger from the postero-
lateral incision localize the midpoint of the psoas and feel the
peak of the disc space (Fig. 21.5). Dock the dilator on this spot
and obtain a lateral radiograph to determine that you are at
the correct level and centered on the posterior 40% of the disc
space (Fig. 21.6). Now, stimulate the dilator and rotate it in all
directions to determine proximity of the lumbar plexus (Fig.
21.7). Pass a guidewire through the dilator to anchor the dilator
to the disc space (Fig. 21.8). Place larger dilators sequentially.
With each dilator, stimulate in all directions to determine the
proximity of the lumbar plexus (Fig. 21.9).6 Slide the retractor
FIG. 21.5 On palpation, the disc space is the peak compared to the valley
of the vertebral body.
370 SURGICAL ANATOMY AND APPROACHES
FIG. 21.6 Dock the dilator on the posterior 40% of the disc space in the lateral plane to get access to the
anterior 60% of the disc space.
FIG. 21.7 Rotate the dilator 360 degrees while stimulating to ensure that the lumbar plexus is a safe distance
from the dilator in all directions.
over the nal dilator and obtain an anteroposterior radiograph
to determine whether the retractor is centered over the disc
with regard to cranial-caudal orientation (Fig. 21.10). Open
the anteroposterior retractor blades, which will translate the
anterior blade anteriorly toward the anterior longitudinal
ligament to give access to the anterior 60% of the disc space
(Fig. 21.11). Pivot the up-down retractor blades, which will
slide the top and bottom blades cranially and caudally over the
disc space and lateral osteophytes, respectively, for complete
access to the disc (Fig. 21.12). Turn on the light source. Obtain
an anteroposterior radiograph to establish that the up-down
blades have passed the osteophytic lateral edges of the vertebral body, above and below the disc space, therefore avoiding
inadvertent endplate fractures (see Fig. 21.10). At this point, it
is optional to pass the shim into the disc to anchor the retractor
rmly into the disc space (Fig. 21.13). Remove the guidewire.
It is recommended at this point to take the nerve probe to
nd the lumbar plexus and determine if the anterior and posterior blades are a safe distance from it. Perform the annulotomy.
rough the annulotomy, place the Cobb retractor directed
toward the inferior endplate to release the anulus from it (Fig.
21.14). Perform this under lateral uoroscopy to avoid injury
to the endplate. Take the Cobb retractor to the contralateral
side and rotate it 90 degrees to distract the contralateral anulus
(see Fig. 21.14). Perform the same task with the Cobb retractor
angled toward the superior endplate. e disc material is then
removed via a combination of blunt dilators, shavers, ring
curette, and pituitary (Fig. 21.15). Place a trial cage and obtain
anteroposterior and lateral images to determine the correct
size for lordosis, coronal tilt, and lateral-listhesis correction,
Chapter 21 Lateral Lumbar Interbody Fusion 371
FIG. 21.8 Anchor the dilator to the disc space with a guide wire when the position has been determined as
safe and adequate for the discectomy.
SECTION
III
A
B
FIG. 21.9 Sequentially dilate to larger sizes while stimulating each time to conrm safety of the corridor to the
disc space.
372 SURGICAL ANATOMY AND APPROACHES
FIG. 21.10 After sliding the retractor over the nal dilator, obtain a
radiograph to conrm that the cranial and caudal blades are centered over
the disc space to prevent inadvertent entry and/or fracture of the endplates.
FIG. 21.11 Open the retractor anteriorly to give access to the disc space.
as well as foraminal height restoration (Fig. 21.16). Place the
nal gra, packed with the surgeon’s preferred biologic for
bone growth, with the assistance of shims to prevent endplate
strain and/or fracture (Fig. 21.17).
FIG. 21.12 The cranial and caudal retractor blades can be pivoted to get
over the lateral osteophytes overlying the disc space.
A
Anatomic Considerations
Lumbar Plexus
A thorough understanding of the regional anatomy is essential
to avoid complications with the lateral approach. e close
proximity of the lumbar plexus poses a risk for permanent and
disabling nerve injury, manifested by weakness or radiculopathy. Meticulous examination of the preoperative magnetic
resonance imaging (MRI) for relation of the lumbar plexus to
the disc space, use of real-time neuromonitoring and biplanar
uoroscopy, and careful dissection of the iliopsoas can aid in
a safe approach.
Multiple studies have attempted to map out the relationship
of the lumbar plexus within the psoas and identify safe corridors or “safe zones” for accessing each disc space to avoid
injury to the plexus and the genitofemoral nerve.55 An early
cadaveric study by Moro et al. examined the lumbar plexus
through axial cuts of the lumbar spine and determined the safe
zone for the lateral retroperitoneal approach, excluding the
genitofemoral nerve, for L4–L5 and above.55 A cadaveric study
B
C
FIG. 21.13 Placement of the shim anchors the retractor to the disc space.
(A) Shim in the lateral view. (B) Shim blade inserter. (C) Removal of wire in
the disc space after anchoring of the shim into the disc to further stabilize
the retractor to the disc space.