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248
Fig. 25.3 Posterioranterior
x-ray of the lumbar spine
with lines drawn along
endplates of each vertebrae
demonstrating how to localize
incision site
A.A. Sama
Good spot for
incision to access
multiple levels
Approaching from
concavity on right
side with two miniopen incisions
allows access from
T12-L5 without
entering chest
Fig. 25.4 Preoperative and postoperative posterioranterior standing scoliosis x-rays showing the correction achieved
25 Lateral Interbody Decompression and Fusion: Which Side to Approach From?
Fig. 25.5 Clinical photograph of patient on operating
table in left lateral decubitus
postion with superimposed
posterioranterior scoliosis
x-ray demonstrating approach
from concave side and how
fl exing the operating table
would facilitate access to
the spine
By flexing the table in direction
of arrows, some of the deformity
is corrected as annuli are
released
249
osteotome remains in the plane of the disc will
minimize the likelihood of injury to the segmental vessels.
In 30 cases of adult degenerative scoliosis,
improvement of Oswestry Disability Index, Short
Form-12, and Visual Analog scores for back pain
improved by approach from the concave side at
130 levels without any increase in perioperative
complications [ 16 ].
25.5 Convex Approach
In cases of a large lumbar scoliosis with extreme
coronal decompensation, approach from the concavity may not be possible except to access the
lower lumbar levels. Due to the extreme degree
of coronal deformity and lumbar curvature in
these cases, the upper lumbar disc spaces may
actually be vertical and directed perpendicular to the fl oor when the patient stands, making approach from the concavity diffi cult if not
impossible (Fig. 25.6 ). These upper discs may
be brought into a more approachable position in
patients with fl exible curves, but in patients with
rigid curves, the levels may not be approachable
with a lateral technique without entering into the
thoracic cavity usually from the convex side. In
cases where approach to the lower levels can be
facilitated by approach from either the concave
or convex sides of the curve, partial correction
can be achieved. This partial correction may
make the upper lumbar levels more approachable
through a second incision in a more orthogonal
plane to the upper lumbar disc spaces usually
from the concavity through a second incision to
facilitate fusion if necessary (Fig. 25.7 ).
In cases where multiple incisions may be
needed, especially when approaching a curve
from the convexity, the lower lumbar incision is
made where it will afford the best approach to the
L4–5 level. It is usually possible to have access
to L3–4 and L4–5 with this incision. Where the
second, more cephalad incision will allow access
to the L1–2 and L2–3 levels. Working in the disc
space to release the annulus is somewhat easier
coming from the convexity (Fig. 25.8 ).
25.6 Other Considerations
In patients with unilateral radicular pain associated with foraminal stenosis or secondary to
scoliosis, approach on the ipsilateral side as the
radiculopathy may serve a dual purpose. First, it
provides the best opportunity to release and correct the deformity thereby opening the ipsilateral
foramen and providing thorough indirect decompression. Second, it mitigates the likelihood of
having a neuropraxia related to the approach on
the side contralateral to the presenting symptoms.
[ 7 , 17 – 23 ]
250
A.A. Sama
This patient with 80° curve L3-5 was
selectively approached from convex side at L3-4
L45 with excellent correction
Fig. 25.6 Standing Anteriorposterior scoliosis x-ray and
coronal CT scan image showing the diffi culty that would
be encountered with an attempt at access from the concave
Regardless of the side of the approach, a good
practice is to advise patients undergoing anterior
or lateral transpsoas surgery that they are likely
to have thigh pain, numbness, or mild weakness
secondary to local irritation associated with the
dissection and retraction around the psoas and
the lumbar plexus. The majority of these postoperative symptoms should resolve within 6 weeks
postoperatively. [ 7 , 17 – 23 ]
In patients who have previously had retroperitoneal surgery, it is prudent to avoid the side of
side in this patient. Anteriorposterior standing scoliosis
x-ray showing fi nal correction after approach from the
convex side and posterior realignment
the prior retroperitoneal approach if possible. If
lateral surgery is contemplated from the side of
the prior retroperitoneal approach, consultation
with a general or vascular surgeon may be warranted. Patients who have had prior radiation
treatment to the lumbar or abdominal area may
also require special consideration in planning
for the lateral approach (Fig.
25.9 ).
For cases that require access to the upper
lumbar or lower thoracic levels, approaching
from the patient’s right side may aid in avoiding
25 Lateral Interbody Decompression and Fusion: Which Side to Approach From?
L1-2 and L2-3
become
accessible
once fractional
curve improved
from convexity
L1-2 & L2-3
not
accessible
preop
Preoperative coronal cat scan Postoperative coronal CT scan
Fig. 25.7 Preoperative and postoperative coronal CT scan images showing lumbar spine
251
Insertion of Cobb elevator to
release annulus entering convex
side
Fig. 25.8 Intraoperative fl oroscopic Anteriorposterior images showing release of the disc space and insertion of the
interbody cage correcting the coronal segmental deformity and restoring disc space height
Insertion of implant from convex
side demonstrating angulation of
disc space
Implant inserted from convex
side achieving correction of
angulation of disc space
252
Patient with history
of right
nephrectomy for
renal cell
carcinoma, severe
foraminal stenosis
from DDD with
collapse and
scoliosis
A.A. Sama
Two level transpsoas
lateral interbody
decompression and
fusion performed from L
retroperitoneal
transpsoas approach with
percutaneous pedicle
screws with excellent
outcome
Fig. 25.9 Standing Anteriorposterior scoliosis x-ray showing correction with selective apical fusion throught the lateral approach and with posterior percutaneous pedicle screws in a patient with prior retroperitoneal surgery
entry into the chest given that the right hemidiaphragm is usually higher than the left.
Oftentimes, dissection onto one of the lower
ribs and subperiosteal dissection above that rib
allows for a safe approach. If necessary the rib
can be removed for bone graft or to allow access.
Once the rib has been removed, a retropleural
plane can be established working posteriorly and
inferiorly to reach the upper lumbar vertebrae
and discs.
The position of the psoas and lumbar plexus
should be evaluated on the MRI. If there is a difference from right to left in the position of the
psoas, the approach is safest on the side where
the psoas is located more posteriorly and closest
to the vertebral body [ 10 , 12 ].
Conclusion
In summary, the anterior lateral approach to the
spine is a powerful tool in the treatment of lumbar conditions that require fusion. Studies have
shown that it can be applied safely and effectively. There are issues unique to the approach
that must be considered and discussed with
patients. The decision of whether to approach
from the left or the right side should be based
on the pathology being addressed and the surgeon’s preference. Guidelines to consider are
outlined above. Whichever the side selected,
it should be the side that affords the safest
approach to the desired levels to be addressed
in order to achieve the best correction of the
condition for which the surgery was indicated.
25 Lateral Interbody Decompression and Fusion: Which Side to Approach From?
253
References
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TransPsoatic Approach (ALPA): a new technique for
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2. 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;6:435–43.
3. Fantini GA, Pappou IP, Girardi FP, et al. Major vascu-
lar injury during anterior lumbar spinal surgery: incidence, risk factors, and management. Spine (Phila Pa
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and sagittal plane alignment following minimally invasive direct lateral interbody fusion for the treatment of
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the psoas muscle and lumbar plexus with respect to
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psoas major and abdominal large vessels with respect
to the X/DLIF approach. Eur Spine J. 2011;20:557–62.
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safe working zones using the minimally invasive lateral retroperitoneal transpsoas approach: an anatomical study. J Neurosurg Spine. 2010;13:260–6.
14. Shimizu S, Tanaka R, Kan S, et al. Origins of the segmental arteries in the aorta: an anatomic study for
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vascular anatomy for total en bloc spondylectomy in
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in the treatment of adult degenerative scoliosis.
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18. Pumberger M, Hughes AP, Huang RR, et al.
Neurologic defi cit following lateral lumbar interbody
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Stand-Alone Lateral Surgery for Spinal Deformity
Amir Ahmadian and Juan S. Uribe
2 6
26.1 Introduction
Spinal deformity is term used to defi ne many
different types of pathologies in either adult or
pediatric patients; hence, it can include both congenital and degenerative defects. Pediatric or adolescent scoliosis/deformity and its treatment are
beyond the scope of this chapter. Furthermore,
a stand-alone lateral construct in pediatric spine
deformity is not well established in the current
literature, and hence posterior or combined techniques are mainly used. Adult spinal deformity
is characterized by spinal curvature >10° with
associated derangement of spinopelvic alignment
[ 1 , 2 ]. Adult scoliosis consists of primary degen-
eration that developed over time after skeletal
maturity most likely secondary to asymmetric
degeneration of discs, osteoporosis, and vertebral
body compression fractures or progressive idiopathy that developed prior to skeletal maturity.
Presenting symptoms of this condition primarily
include radiculopathy, chronic low back pain and
neurogenic claudication caused by concurrent
spinal stenosis.
Classifi cation of type and progression of adult
deformity both radiographically and clinically
is critical to the treatment paradigm [ 3 ]. Timing
of surgical intervention, surgical approach, and
length of constructs for operative stabilization
A. Ahmadian, M.D • J. S. Uribe , M.D (*)
Department of Neurological Surgery ,
University of South Florida , Tampa , FL , USA
e-mail: juansuribe@gmail.com
or correction have been controversial. Minimally
invasive spine surgery (MIS) was initially
developed to address morbidity associated with
traditional, open spinal surgery. As the fi eld
has continued to advance, MIS techniques have
been implemented in the treatment of adult spinal deformity (ASD). One such technique is the
minimally invasive lateral retroperitoneal transpsoas interbody fusion (MIS-LIF), which was
fi rst described by Pimenta in 2001 [ 4 , 5 ]. This
approach has been used to deliver stand-alone
interbody cages. Indications for operative intervention remain the same across any surgical
approach and include progression of deformity,
pain, and neurological defi cits. Stand-alone MIS
lateral constructs are relatively new to the previously established surgical paradigms. Patient
selection is key in any surgical intervention but
particularly in the decision for a lateral MIS
stand-alone construct.
26.2 Patient Selection
Once the decision to proceed with surgical intervention is made, selecting the most appropriate
and patient specifi c approach can be challenging. There are no “one size fi ts all” constructs for
spinal deformity. Stand-alone lateral constructs
should be reserved for patient who at unacceptably high operative risk for alterative conventional or MIS combined approaches. Patients with
unrelievable pain, progressive degenerative scoliosis with advanced age, signifi cant co-mobility,
M.Y. Wang et al. (eds.), Minimally Invasive Spinal Deformity Surgery,
DOI 10.1007/978-3-7091-1407-0_26, © Springer-Verlag Wien 2014
255
256
A. Ahmadian and J.S. Uribe
and signifi cant anesthetic risk should be considered for less invasive interventions. Additionally,
to consider a lateral stand-alone construct, the
radiographic evaluation should exhibit reasonable coronal/sagittal balance. Finally, all patients
being considered for stand- alone constructs
should be evaluated for degree of osteopenia
or osteoporosis. The vertebral body end-plate
strength is greatly dependent on the bone density
[ 6 ]. Patient with osteoporosis or advanced osteo-
penia should not be considered for stand-alone
lateral fusion but rather a nonoperative treatment
options or a limited decompression. However,
this can lead to a deformity progression and
worsening of symptoms.
26.3 Advantages and
Disadvantages
As previously stated, the decision for surgical
intervention and approach, particularly lateral,
is multifactorial. Morbidity of surgical approach
required postoperative care, operative/anesthetic
risk, and a patient’s preoperative medical comorbidities are of particular importance in proceeding with a lateral stand-alone construct. The risk
profi le of anterior, posterior, lateral, and combined approaches is different and must be considered [ 7 – 10 ]. Minimally invasive techniques
(MIS) have potentially less surgical and postoperative morbidity [ 11 , 12 ]. There are certain
advantages to MIS lateral approach that make
stand-alone feasible. It is not a destabilizing technique as compared to the posterior approaches in
which important stabilizing structures have to be
violated to gain access to the intervertebral disc
space. In addition, it is associated with shorter
operative time and decreased blood loss [ 5 , 13 ].
The MIS lateral approach also allows for generous
discectomy and end-plate preparation allowing
placement of larger interbody implant placement from one diaphysis to the other, with less
likely device subsidance [ 14 , 15 ]. On the other
hand, the MIS lateral approach allows access to
more levels with less vascular risk and preservation of anterior longitudinal ligament (ALL) as
compared to the traditional anterior interbody
fusion (ALIF). The risk of lumbar plexus injury
is greater for lateral techniques particularly in the
lower lumbar levels with a relative preservation
of sympathetic plexus which is a particular concern associated with a direct anterior approach.
Furthermore, compared to posterior approaches,
there is increase risk to retroperitoneal organs
and vessels.
26.4 Biomechanics
Biomechanical comparisons between the standalone lateral and stand-alone ALIF have demonstrated its increased rigidity to promote
arthrodesis [ 16 ]. Stand-alone lateral is more rigid
in lateral bending and fl exion-extension when
compared to stand-alone ALIF [ 16 ]. Though the
biomechanical advantage of a lateral stand-alone
construct is its favorable rigidity in all six basic
movements, it falls short to the addition of unilateral and bilateral pedicle screws, which are
much more rigid overall. Stand-alone construct
should be reserved for patients free of any signifi cant gross instability. Patients with instability would best be treated with additional spinal
instrumentation. For similar reasons, stand-alone
constructs may not be optimal for gross deformity correction, though it does have a very limited application in this patient population. In
addition, a unifi ed bilateral pedicle screw and
rod construct provides stability across multiple
segments as compared to a lateral stand-alone
construct, which stabilizes one segment at a time
and protects subsidence. Phillips et al. presented
radiographic evaluation of a cohort of patient
with lumbar stand-alone constructs and who
exhibited no loss of Cobb angle, with minimal
improvement in lumbar lordosis of 9.8 % and
18.7°, respectively [ 17 ]. As expected spinopelvic
parameters signifi cantly improve with addition
of posterior instrumentation, which emphasizes
26 Stand-Alone Lateral Surgery for Spinal Deformity
257
the importance of patient selection of stand-alone
constructs.
26.5 Anatomical Considerations
Retroperitoneal transpsoas approach involved
traversing the nerves of the lumbar plexus both
within and outside of psoas muscle. There are
four major nerves traveling outside of the psoas
muscle and include subcostals (T12), iliohypogastric (L1), ilioinguinal (L1), and lateral femoral cutaneous (L2–L3) nerves. They originate
from the posterior border of the psoas muscle
and descend obliquely through the retroperitoneal space. These free nerves are most vulnerable at the initial stages of the approach during
abdominal muscle and retroperitoneal dissection
superfi cial to the psoas and hence necessitate
delicate blunt dissection [ 18 ]. The genitofemoral
(L1–L2) nerve initially travels within the psoas
muscle, across the L2/L3 disc space, for a short
distance before emerging and continuing on the
anterior surface of the muscle.
The L2, L3, and L4 roots merge to form
the femoral nerve which courses deep within
the psoas muscle to pass under the inguinal
ligament prior to giving off cutaneous (medial/
intermediate femoral cutaneous/infrapatellar
branch/saphenous nerve) and muscular branches.
Variation in proximal trajectory of the femoral
nerve has been described as it transverses the
psoas muscle [ 19 , 20 ]. Though anatomical varia-
tions to the lumbar plexus have been described in
the literature, large population studies to establish a more accurate measure of the prevalence of
the surgically relevant variability are lacking [ 21 ,
22 ]. Variations in trajectory of the femoral nerve
should be strongly considered when establishing
an operative corridor with utilization of directional EMG monitoring to prevent nerve injury.
Finally, the obturator nerve (L2–L4) courses
through psoas muscle posterior to the femoral
nerve. It emerges from the medial aspect of the
psoas muscle and travels just lateral to the sacrum
prior to exiting the pelvis though the obturator
foramen. Finally, the sympathetic plexus runs on
the anterior surface of the vertebral body and is at
risk especially with lateral corpectomies or anterior longitudinal ligament (ALL) releases.
The fi bers of the sympathetic plexus/ganglion are found along the lateral edge of the ALL
and have communicating branched with lumbar
plexus nerves. The communicating branches consist of the white (presynaptic) and gray (postsynaptic) rami communicans. Moreover, these fi bers
generally reside at the inferior aspect of the vertebral body.
The intended trajectory of the lateral retroperitoneal dissection is mid-vertebral body
in the A-P plane for placement of intervertebral cage. The approach is anterior to the neural foramen and hence vulnerable to lumbar
nerves injury rather than specifi c root injury.
Lumbar nerves have contributor from multiple
roots, therefore a much more clinically signifi cant outcome if injured. All nerves of the
lumbar plexus have a dermal sensory representation, except for the intrinsic motor branches
supplying the psoas muscle. Clinical diagnosis of specifi c lumbar plexus nerve injuries
can sometime depend on overlapping sensory
defi cits, which can make diagnostic evaluation
more diffi cult.
26.6 Operative Considerations
Intraoperative consideration of a lateral approach
to any type of spinal deformity is uniform and
includes understanding of regional anatomy,
avoidance of lumbar plexus injury, preservation
of the ALL, adequate end-plate preparation, and
restoration of disc height. However, with standalone constructs a great emphasis is made on utilization of vertebral ring apophysis and hence on
implant width or “footprint” to increase fusion
bed area and more importantly to protect the
implants from subsidence. Available width cages
include 18, 22, and 26 mm width and lordotic up
258
A. Ahmadian and J.S. Uribe
to 30° (Coroent, Nuvasive CA). Large-diameter
implants are less likely to subside compared
to small-diameter cages, possibly related to a
more effi cient transfer of force to the end plate
[ 23 – 25 ]. Utilization of dense bone of the vertebral ring apophysis for load bearing is a key concept for stand-alone lateral fusion as to minimize
the subsidence risk.
The preoperative planning is critical to ensure
that the patient is a good surgical candidate.
Preoperative imaging should include a magnetic
resonance imaging (MRI) to ensure that abdominal blood vessels will not hinder access to the
desired disc space and an A-P X-ray to determine which side will provide the best access,
especially at L4/5, in relation to the iliac crest.
The patient is then placed in the lateral position with the optimal side facing up. Placing the
concave side of a scoliotic deformity facing up
can facilitate correction by improving access to
the L4/5 disc space, allowing access to multiple
levels through fewer incisions and release of
soft tissue on the contracted side hence permitting placement of asymmetric cages. The legs
are fl exed maximally at the knee and hip to relax
tension on the psoas muscle and lumbar plexus
nerves. A roll is placed beneath the axilla to prevent brachial plexus injury, and a roll is placed
under the iliac crest to facilitate deformity correction and promote fl exion at the iliac crest for
improved access to the L4/5 level. Intraoperative
fl uoroscopy is then used to position the patient
in such a manner that a symmetric A-P image
with the pedicles equidistant from the spinous
processes is achieved. It is essential that these
images be as accurate and symmetric as possible
to prevent inadvertently dissecting too far anteriorly or posteriorly. In multilevel procedures, the
position should be reevaluated at every level to
address rotational deformity and changes related
to implant placement.
Once properly positioned, the patient is taped
and secured to the table. If needed, the table is
fl exed at the level of the iliac crest just enough to
give access to the disc space. Excessive fl exion of
the table can put tension on the lumbar plexus and
potentially promote nerve injury. The incision
is fl uoroscopically guided and marked at the
middle of the disc space based on the anatomic
safe zones [ 26 ]. If multiple disc spaces are being
approached, separate fascial incisions are made
for each disc space to help stabilize the retractor
and to minimize abdominal muscles dissection.
Once the fascial incision over the area of interest is completed, the external oblique, internal
oblique, and transversus abdominis muscles are
identifi ed and bluntly dissected until the transversalis fascia and retroperitoneal space are encountered. The psoas muscle is palpated. Sequential
dilators are then used to dilate the psoas muscle
and stimulated using triggered EMG (t-EMG).
The position of the femoral nerve can be estimated by the location of the sharp decreases in
the t-EMG threshold. Ideally, the sharp decreases
will be present when stimulating with the dilator posteriorly and increased thresholds present
anteriorly; thus, the femoral nerve can be estimated to be posterior to the dilators. This orientation will allow placement and opening of the
retractor with minimal risk of nerve injury. Once
the t-EMG stimulation with the fi nal dilator verifi es decreased threshold responses posteriorly
and increased threshold responses anteriorly, the
retractor is then placed. Once it is confi rmed that
disc space is visualized and no nerves are present in the surgical fi eld, lateral X-ray is obtained
to check the position of the retractor in relation
to the disc space. The shim blade is advanced
into the disc space fi rmly with image guidance
using A-P fl uoroscopy.
Once the retractor is in fi nal position, the
rest of the procedure must be performed as effi ciently and quickly as possible to reduce the
duration of retraction of the lumbar plexus. With
careful attention to keeping instruments in a
vertical orientation, a combination of box cutter
disc shaver, pituitary rongeur, rasp, and curettes
are utilized to prepare the disc space. Depending
on the preoperative X-ray, a straight or lordotic
polyetheretherketone (PEEK) interbody cage,
fi lled with a variety of biologics, is then placed
(Fig . 26.1 ).