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Part I
Introduction
History and Rationale for the Minimally Invasive Lateral Approach
Luiz Pimenta , Luis Marchi , Leonardo Oliveira ,
Fernanda Fortti , Etevaldo Coutinho ,
Rubens Jensen , and Rodrigo Amaral
1
1.1 Introduction
The minimally invasive lateral approach, since
its fi rst technical report [ 1 ], has been shown to be
a less invasive alternative to access the anterior
column of the thoracolumbar spine, providing
direct visualization of the spinal structures while
reducing adjacent vascular, sympathetic, and
visceral trauma associated with open anterior
approaches. In addition, less blood loss, less
postoperative pain, shorter hospital stay, and
faster return to daily activities are associated
with this technique [ 2 – 5 ]. The lateral approach
has been utilized in an increasingly number of
surgical indications. It was fi rst described to treat
low back pain associated with degenerative disc
disease above L5 level, avoiding patients with
severe central canal stenosis [ 6 ]. Over the years,
indications were extrapolated, showing that indirect decompression of the neural structures can
be achieved by disc height restoration [
ligamentotaxis can derotate the vertebral body,
L. Pimenta (*)
Instituto de Patologia da Coluna (IPC) ,
São Paulo , Brazil
University of California , San Diego , Brazil
LuizPimenta@luizpimenta.com.br
e-mail:
L. Marchi • L. Oliveira • F. Fortti • E. Coutinho
R. Jensen • R. Amaral
Instituto de Patologia da Coluna (IPC) ,
São Paulo , Brazil
7 ], and
providing coronal alignment [ 8 – 12 ]. Other
published indications, with or without posterior
supplementation, are adjacent level disease,
pseudoarthrosis, trauma, infection, sagittal
alignment, spondylolisthesis revision surgeries,
and total disc replacement [ 13 – 25 ]. The scien-
tifi c evidence has been growing and being highlighted in high-impact publications in the
literature, showing its advantages, effi cacy, and
safety related to this technique. These advances
make surgeons responsible for learning and
using these new techniques and technologies in
order to provide their patients better clinical and
radiological results with less complications.
1.2 Historical Approaches to the Lumbar Spine
The fi rst description of a lumbar laminectomy
dates from 1829, by Smith, to treat progressive
paresis following a lumbar fracture [ 26 ].
Thenceforth, new approaches and surgical indications emerged in the literature, being the early
reports of fusion published in 1930s [ 27 ] for the
treatment of spondylolisthesis, what would later
be called anterior lumbar interbody fusion (ALIF)
[ 28 ]. This technique allows the surgeon to prepare
a greater surface area, with better blood supply and
better load distribution in comparison to the posterior column, essential in the process of fusion [ 29 ].
Obviously, the anterior approach has inherent
© Springer International Publishing Switzerland 2017
M.Y. Wang et al. (eds.), Lateral Access Minimally Invasive Spine Surgery,
DOI 10.1007/978-3-319-28320-3_1
3
4
Fig. 1.1 Comparison of cage contact area for PLIF, LLIF, and TLIF ( Left to right )
L. Pimenta et al.
disadvantages, as abdominal muscle dissection,
mobilization of the great vessels and abdominal
content, dissection of the presacral plexus, retrograde ejaculation, and urinary retention. An access
surgeon is often in collaboration with the spine
surgeon. Nowadays, the anterior approach progressed and the utilization of laparoscopic techniques allowed the surgeon to perform the surgery
with smaller incisions, what is now considered a
mini-open technique [ 30 ]. The procedure consists
of blunt dissection of the abdominal musculature,
manual dissection of the retroperitoneal space,
while self-retaining retractors allows direct visualization of the anterior spinal column, enabling a
large cage insertion for interbody fusion.
On the other hand, the minimalization of the
posterior approach to herniated discs and spondylolisthesis have led to less disruptive techniques, in attempt to decrease tissue trauma and
enhance clinical outcomes. Jaslow [
31 ] and
Cloward [ 32 ] initially described the posterior
lumbar interbody fusion approach (PLIF) separately in the 1940s. This approach has the advantage to directly decompress the neural structures
during interbody cage placement. However, it
requires cauda equina retraction and higher risk
of nerve roots injury [ 33 ]. A modifi cation of this
technique was proposed by Harms in 1982 [ 34 ],
with a unilateral approach that theoretically
require less tissue trauma, less bone resection and
dural retraction, called transforaminal lumbar
interbody fusion (TLIF). Both PLIF and TLIF do
not allow inserting large implants, generating
less contact between the endplates and the graft,
which may impair fusion (Fig. 1.1 ).
In an attempt to minimize tissue trauma and
improve biomechanical support, an anterolateral
retroperitoneal approach was described, with
posterior dissection and retraction of the psoas
muscle [ 35 – 37 ]. However, iatrogenic neural defi -
cits and muscle hypotonia subsequent to lumbar
plexus compression due to psoas retraction may
occur [ 38 ]. The psoas traverse minimizes nerves
compression, but carries an inherent risk of direct
nerve injury. Early attempts to surpass this issue
include evoked EMG monitoring, but with a
60-degree approach and patient in prone position
[ 39 ]. This orientation routinely incarcerates
nerves of the lumbar plexus, hindering safe
access to the intervertebral disc and placement of
intervertebral devices (Fig. 1.2 ). Nevertheless,
this experience provided advances in the use of
EMG monitoring in spine surgery, despite the
little usefulness, safety, and effectiveness of this
surgical approach.
1.3 Development of Lateral
Access Surgery
The complications and technical challenges associated with anterior endoscopic surgery led to the
development of a new trajectory to the intervertebral discs (Fig. 1.3 ). It was described as lateral
endoscopic transpsoas retroperitoneal approach
(LETRA) and was fi rst presented in 2001 [ 40 ].
This technique utilized a blunt fi nger dissection
of the retroperitoneal space, insertion of tubular
portals with endoscopic visualization, but without EMG monitoring. The fi rst clinical report on
1 History and Rationale for the Minimally Invasive Lateral Approach
Fig. 1.2 60-degree approach
with the patient in prone
position, with routinely
incarcerated nerves of the
lumbar plexus during access
Fig. 1.3 Very fi rst
drawing of the initial idea
of a 90-degree approach to
the lumbar spine, what
would become in the future
the LLIF
5
85 consecutive patients has shown 14 % incidence
of postoperative psoas weakness and 3.5 %
incidence of slight thigh atrophy [ 1 ].
Thus, there was a need to develop tools that
allow secure lateral access to the lumbar spine,
overcoming the disadvantages and preventing
iatrogenic neurological injuries. An expandable
retractor was developed (NuVasive®, Inc., San
Diego, CA) to provide direct visualization of the
surrounding structures, improving visibility
achieved by endoscopic viewing. To guide the
passage through the psoas muscle, an EMG neuromonitoring prevented the blind traverse of the
psoas muscle, protecting the integrity of the neural structures. Thereby, the lateral lumbar interbody fusion (LLIF) is defi ned as a 90-degree
6
L. Pimenta et al.
Fig. 1.4 Relevant anatomy for lateral access surgery of the lumbar spine
lateral, retroperitoneal transpsoas approach to the
anterior spinal column, with minimum tissue
trauma by use of blunt fi nger dissection of the
retroperitoneal space and tactile guidance of the
fi rst dilator to the psoas surface. Figure 1.4 shows
the relevant anatomy for lateral access surgery in
lumbar spine. The utilization of a split-blade
the restoration of the normal disc and foraminal
heights, allowing indirect decompression of the
neural structures through an anterior intervertebral fusion, correcting sagittal and coronal alignment, stabilizing the targeted level and facilitating
bone ingrowth without the morbidity of open
surgeries.
retractor generates a customizable working portal
that allows direct visualization, with the
opportunity to insert a wider cage implant in
1.4 Validation of the Technique
comparison to other anterior interbody devices.
The bilateral annular release allows the device to
reach both sides of apophyseal ring, generating a
more stable construction and greatest biomechanical advantage. The technique also permits
The initial experience in lateral access surgery
included less complex surgical indications, like
1- or 2- level interbody fusion for degenerative
conditions [ 5 , 41 ]. As the procedure maintains
1 History and Rationale for the Minimally Invasive Lateral Approach
7
intact all ligaments that play a role in ligamentotaxis, the slippage reduction in spondylolisthesis
[ 16 , 23 ] and vertebral derotation in degenerative
scoliosis [ 10 – 12 , 42 ], added to minimal collateral
muscle and bone damage, with decreased risks
and complications, demonstrated the superiority
in several aspects of lateral access surgery over
open traditional techniques [ 43 ].
The technical and technological advancement
have led to the development of different tools and
devices, expanding the range of indications. The
polyetheretherketone (PEEK) spacers adapts on
patient’s necessities, with different width, length,
sagittal angle, coronal angle, integrated fi xation,
like lateral plating that allow supplemental fi xation by the same lateral approach, and advancements in working portal, allowing greater safety
and effectiveness through better visualization of
the targeted structures, minor damage to adjacent
tissues, and greater integration with the new
instruments. This leads to a more effi cient surgery
with less risks and complications for patients.
Since it fi rst description, the published literature into lateral access surgery brought to light
greater knowledge regarding applications and outcomes of the procedure. This includes dozens of
peer-reviewed articles, and hundreds of abstracts
and posters presented at the most important scientifi c meetings all over the world. These scientifi c
evidences have allowed the expansion of surgical
applications. Currently, the applications of lateral
approach include pseudoarthrosis, discogenic low
back pain, degenerative back and leg pain, trauma,
infection, tumor, coronal and sagittal alignment,
revision, spondylolisthesis, motion preservation,
adjacent level disease, and others that require
access to the anterior column of the thoracolumbar
spine [
15 , 18 , 20 , 25 , 44 – 52 ]. These results will be
discussed throughout the book and so are not
addressed in this present moment.
1.5 Future Steps on Lateral
Approach
There is a continuous need in keeping medical
education, maintaining efforts on development
and research, and improving individualized patient
care. Multicenter studies and data collection are
essential for continued validation of new applications. The lateral approach extended the look on
various pathologies of the spine, with more safety,
effectiveness, and better clinical outcomes besides
signifi cant less morbidity. It is imperative that surgeons and medical societies continually assess the
value of the care we deliver using methods that
allow us to offer to our patients the best quality of
care. This is the new environment that we live in,
and we must always be up to date about new techniques and technologies and its validation in evidence-based medicine. The lateral access surgery
has revolutionized how interbody fusions can be
done, and the involvement of the spine surgeons
will be critical in the continued advancement of
this technique.
References
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JA. Grade 2 spondylolisthesis at L4-5 treated by
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39. Malberg M. eXtreme lateral interbody fusion (XLIF).
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Biomechanics of Lateral Spinal Reconstruction
Paul Porensky , E. Emily Bennett ,
and Edward Benzel
2
2.1 Introduction
The lumbar spine exists in a unique anatomical
and surgical environment, with biomechanical
and load-carrying characteristics distinct from
those within the cervicothoracic spine. The ability
to approach lumbar elements with a relatively
facile lateral trajectory affords new augmentation
and fi xation opportunities. Though our understanding of lumbar biomechanics in both physiological and pathological settings is well
appreciated, the vast majority of investigations of
lumbar surgical intervention have evaluated
posterior and anterior approaches. The growing
popularity of lateral lumbar surgery will undoubtedly lead to additional lumbar biomechanical
inquiry. A number of important questions need to
P. Porensky
Center for Spine Health , Neurological Institute,
Cleveland Clinic , Cleveland , OH , USA
E. E. Bennett
Department of Neurosurgery , Neurological Institute,
Cleveland Clinic , 9500 Euclid Ave, S-40 ,
Cleveland , OH 44195 , USA
E. Benzel , MD (*)
Center for Spine Health , Neurological Institute,
Cleveland Clinic , Cleveland , OH , USA
Department of Neurosurgery , Neurological Institute,
Cleveland Clinic , 9500 Euclid Ave, S-40 ,
Cleveland , OH 44195 , USA
benzele@ccf.org
e-mail:
be considered with respect to lateral surgery:
defi ning the benefi ts of maintenance of posterior
elements, the effects of disengaging load-bearing
facets, and the outcomes of vertebral interspace
height and alignment augmentation. The goal of
this chapter is to provide a review of normal lumbar anatomy and biomechanics, as well to review
and extrapolate what is already known to altered
mechanics in the setting of lumbar pathology and
lateral lumbar intervention.
2.2 Lumbar Anatomy
An understanding of lumbar spine anatomy is
essential to both appreciate the relevant
biomechanics in the physiological and pathologic
settings, as well as to understand the effects of
lateral surgery. A complex interplay of multiple
elements defi nes the lumbar region, including
osseous structures such as the vertebral body and
endplate, strong and mobile facet joints, and
active and passive soft-tissue components –
including muscles, ligaments, and intervertebral
discs. Select components contain mechanoreceptors, proprioceptors, and pain receptors that communicate with the central nervous system to
maintain stability and avoid injury. The combination of these elements serves four main functions,
including bracing viscera and the appendicular
skeleton, nerve root and thecal sac protection,
extremity control, and mobility. Each lumbar
© Springer International Publishing Switzerland 2017
M.Y. Wang et al. (eds.), Lateral Access Minimally Invasive Spine Surgery,
DOI 10.1007/978-3-319-28320-3_2
11
12
P. Porensky et al.
element must maintain stability, as well as support mobility and control. Our bipedal evolutionary trajectory has resulted in the development of
structures that are capable of impressive forceresistance, as well as effi cient and fl uid movement. The lumbar spine is itself a widely mobile
bridge to the lower extremities [ 1 ]. These lumbar
structures not only carry a greater load than the
cervical and thoracic spines but also lack the stabilizing effect of the ribcage and must support the
oversized lever arms required to maintain upright
posture [ 2 ].
2.2.1 Vertebra
The vertebral body is the basic functional unit of
the spine. The fi ve lumbar vertebral bodies are all
comparatively more massive than their thoracic
and lumbar counterparts, owing to their increased
force-carrying requirements. The bodies themselves become progressively larger from cranial
to caudal, with each level absorbing the majority
of the rostral axial load strain. A honeycombed
cancellous architecture, akin to the inner support
of an airplane wing, achieves a high strength to
weight ratio – approximately four times that of
cortical bone. Vertical struts connect from one
endplate to the other and absorb the axial loads;
outward bowing is contained by orthogonally oriented transverse struts, thereby converting forces
from vertical to horizontal [ 3 ]. Transverse ele-
ments also absorb shear forces. These oblique
struts sweep together at the pedicles to resist the
localized high tensile forces, then vertically to
the facet masses where vertical forces are again
defl ected, and fi nally to the lamina and spinous
process to resist further tensile and bending
forces [
directly related to weight-bearing status, with a
more complex cancellous arrangement within the
body and facet masses and a greater cortical concentration at the pedicle [ 2 ]. Fortunately this
arrangement provides greater pedicle screw pullout resistance, with the notable exception of the
sacrum. The pedicles assume a progressive
increase in mass from rostral to caudal. The
1 ].
The ratio of cortical to cancellous bone is
transverse diameter increases and the pedicle
height progressively decreases as the spine is
descended. The transverse pedicle angle also
increases with more caudal direction, while the
opposite is true in the sagittal plane [ 4 , 5 ].
2.2.2 Intervertebral Discs
Intervertebral discs are specialized structures that
have both the tension-resisting properties of a
ligament and load-carrying element akin to joint
cartilage [ 3 ]. Healthy discs provide spine mobil-
ity while also absorbing immense axial and shear
loads. Each disc has two distinct elements, the
nucleus pulposus and annulus fi brosus. The former, a remnant of the primitive notochord, is
composed of water (a 90 % majority), collagen,
and highly hydrophilic proteoglycans. The annulus is a circumferential bundle of laminated collagen sheets, each sheet overlaying the previous
in a different orientation and fusing with adjacent
layers [ 1 , 6 ]. The annulus is most robust ventrally
and weakest in the posterolateral margins. The
disc is bounded cranially and caudally by vertebral endplates, each composed of a thin layer of
cortical bone (~1 mm, though thinnest in the center adjacent to the nucleus pulposus) and hyaline
cartilage. Healthy endplates are no longer perforated by vascular feeders by the age of skeletal
maturity, though they become revascularized in
the setting of discal degeneration. The discs,
therefore, are the largest structures in the body
that rely on diffusion for nutrition and metabolic
exchange [
Axial loading results in increased intradiscal
pressure. These hydrostatic forces are transferred
to radial forces that are contained by the high tensile strength annulus as well as ridged and inelastic endplates [ 1 , 2 , 7 ]. Hyperfl exion and torsional
loading lead to maximal strain at the posterolateral annulus margins, which can result in progressive annular tear and subsequent back pain.
Complete failure of the annulus leads to nucleus
herniation and nerve root compression [ 1 , 6 ].
Senescence of the disc complex includes progressive nucleus desiccation and stiffening of the
circumferential annulus fi bers, the combination
7 ].