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27 Lumbar Disc Arthroplasty
369
The rare complication of wear debris reactions, such as granuloma or pseudotumor formation, is often unpredictable except in patients
with known reaction or allergy to any of the
materials utilized in the replacement disc. If
this information is known, such patients are not
candidates for L-TDR [3, 12, 14, 16, 27].
Careful surveillance for thromboembolic
events is advisable as these patients are at particularly high risk because of the mobilization of the
great vessels. Postoperative DVT chemical prophylaxis should be discussed with the access vascular surgeon. Infections are rare but if they do
occur decompression and fusion procedures with
or without removal of the hardware are often
indicated.
Conclusion
Lumbar disc replacement surgery continues to
evolve based on our expanding knowledge of
lumbar segmental biomechanics and results of
long-term Level 1 evidence-based clinical trials.
Data from recent long-term multicenter prospective randomized trials as well as meta-analysis studies reveal superiority to fusion in both
clinical and radiographic outcomes. Devices
which permit controlled posterior translation of
the superior articular facet processes in flexion
and also limit the over-distraction of the disc
interspace correlate with improved clinical outcomes. Careful patient selection, including facet
joint assessment with appropriate imaging and
diagnostic pain injections, is recommended
especially at the L5-S1 level. Expanded indications include broad-based disc herniations with
spinal stenosis, multilevel degenerative disc disease, and hybrid surgical indications. The principles of lumbar disc replacement surgery
include careful patient preoperative evaluation
and selection, meticulous and careful spine
access, and appropriate implant selection based
on vertebral body dimensions. Further assessment of endplate morphology needs to be considered to ensure optimal clinical and
radiographic outcomes.
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Minimally Invasive Posterior Lumbar Fusion Techniques
Luis M. Tumialán
Abbreviations
ALIF Anterior lumbar interbody fusion
AP Anteroposterior
MIS Minimally invasive surgery
MR Magnetic resonance
TLIF Transforaminal lumbar interbody fusion
VAS Visual analog scale
Introduction
In 1997, Foley and Smith introduced a paramedian transmuscular approach to the lumbar spine
to perform microdiscectomies through a cylindrical access port secured after dilatation of the
paraspinal muscles [1]. Building on the familiarity of the transmuscular decompression techniques, surgeons combined well-established
percutaneous techniques for instrumentation of
the pedicles. The subsequent development of
minimally invasive techniques to accomplish the
goals of lumbar fusion followed a logical step-
L.M. Tumialán, MD (*)
Department of Neurosurgery, Barrow Neurological
Institute, St. Joseph’s Hospital and Medical Center,
350 W. Thomas Rd., Phoenix, AZ 85013, USA
luis.tumialan@barrowbrainandspine.com
e-mail:
28
wise progression from that minimally invasive
decompression platform.
From an anatomical standpoint, the paramedian transmuscular access to the lumbar segment
lent itself especially well to transforaminal access
to the disc space. In short order, the tenets of
interbody fusion established by Cloward [2] were
applied to the unilateral transforaminal corridor
popularized by Harms and Jeszenszky [2, 3]. As
spine surgeons synthesized percutaneous and
minimally invasive techniques with experience
in traditional midline open surgery, the minimally invasive transforaminal lumbar interbody
fusion (MIS TLIF) arose as the leading procedure for the management of single-level lumbar
degenerative disc disease.
Currently, three main approaches to the MIS
TLIF reflect the evolution of the procedure:
percutaneous microendoscopic, mini-open, and
hybrid (percutaneous/mini-open) approaches.
The first main approach that arose was instrumentation of the pedicle by a purely percutaneous technique with tubular access to the
segment for decompression and interbody; this
technique was popularized by groups led by
Foley and Fessler [4, 5]. The percutaneous
instrumentation of the pedicle reconciled the
anatomical challenge of attempting to expose
pedicle screw entry points through the same
incision that also exposes the midline elements.
A percutaneous approach spared the patient the
lateral exposure needed from a midline
approach, which was linked with extensive tis-
© Springer International Publishing AG 2017
L.T. Holly, P.A. Anderson (eds.), Essentials of Spinal Stabilization,
DOI 10.1007/978-3-319-59713-3_28
371
372
L.M. Tumialán
sue trauma. Instead, the instrumentation of the
pedicles was accomplished with direct cannulation of the pedicle through a distinct operative
site, which was nothing more than a stab incision. With the percutaneous technique, there
was no need to widely expose the anatomy,
with the resultant disruption of the musculature
and consequential decrease in blood flow
because of the considerable muscle-retractor
interface. The benefit of minimizing the extent
of exposure translated into reduced postoperative discomfort, shorter hospitalizations, and a
lower risk of infection [5–7].
Refinements to the minimal access ports
prompted further evolution of the percutaneous
form of the procedure. Instead of four stab incisions for the percutaneous pedicle fixation and
the incision for the paramedian transmuscular
decompression and interbody, an expandable
minimal access port secured over the facet
allowed for exposure of the entire transforaminal
corridor in addition to access to the pedicle screw
entry point. In this manner, a hybrid percutaneous mini-open procedure was described.
However, limitations to the percutaneous procedure prompted surgeons to consider the application of other minimally invasive techniques and
other minimal access ports. The first limitation was
the radiation exposure to the surgeon involved in
percutaneous instrumentation of the lumbar spine
[8]. The recent availability of computer- assisted
navigation has minimized this concern. However,
as MIS TLIF continues to be used more in an
ambulatory surgery setting, it is unlikely that computer-assisted navigation will increase in this setting given its cost. The second limitation was the
inability to perform a posterolateral fusion. While
this inability may be of varying importance given
the high reliability of interbody fusion, access to
the transverse processes also provided access to
the facet joint contralateral to the transforaminal
approach. Having that access is becoming increasingly important to preserve, if not restore, segmental lordosis. In a comparison study of anterior
lumbar interbody fusion (ALIF) and TLIF, Hsieh
and colleagues [9] demonstrated a two-degree loss
of lumbar lordosis and a loss in foraminal height in
a TLIF cohort compared to an ALIF cohort.
To address these limitations, surgeons began
to explore what has been labeled the mini-open
TLIF. With this technique, expandable minimal
access ports are used to directly visualize the
pedicle screw entry points for instrumentation of
the spine, and then that same exposure is simultaneously used to complete the decompression on
one side and the posterolateral fusion and a modified Smith-Petersen osteotomy on the other [10].
The most important element of a minimally
invasive procedure is that the result can be equivalent to its open counterpart. All surgeons should
explore the various technologies available as they
proceed through their learning curves to achieve
the goals of decompression, stabilization, and
successful long-term clinical outcomes.
Throughout that process, a thoughtful analysis of
the clinical and radiographic outcomes should
guide each surgeon to the technique that works
best in his or her hands. Among the radiographic
criteria that should be scrutinized is the capacity
to restore foraminal height and segmental lordosis
in the short term and to achieve radiographic
union and subsidence of the interbody in the long
term. Additionally, an analysis of validated clinical outcomes measures should be used to carefully examine the patient’s return to functional
mobility and demonstrate improvements in visual
analog scale (VAS) leg and VAS back scores. The
thoughtful analysis of those outcomes, both clinical and radiographic, will lead surgeons to find the
minimally invasive technique that offers the most
reliable surgical intervention. In keeping with that
spirit of refinement, the technique described in
this chapter represents the technique that evolved
during the author’s learning curve while performing over 500 MIS TLIFs.
Indications and Patient Selection
The most common indications for the MIS TLIF
are single-level and two-level lumbar degenerative pathologies that include spondylolisthesis,
recurrent disc herniation (third recurrence), recurrent facet cyst, and advanced degenerative disc
disease with radiculopathy [
experience, three-level lumbar degenerative disc
11]. In the author’s
28 Minimally Invasive Posterior Lumbar Fusion Techniques
373
disease may not be outside the realm of minimally
invasive surgery, but it does tend to be outside the
realm of the MIS TLIF. A three-level pathology
may be best treated with a combination of other
surgical approaches, such as transpsoas interbody
approaches, minimally invasive decompressions,
and percutaneous instrumentation.
The ability to proficiently select patients offers
the greatest likelihood of clinical and radiographic success. Patients with elevated body
mass indices should be encouraged to make every
effort to move toward their ideal body mass index
before surgery and to continue that trend after
surgery. It has been the author’s experience that
instituting a core-strengthening program before
surgery may further facilitate the weight-loss
goal. Concern for osteoporosis in a patient should
prompt a bone mineral density study; evidence of
osteoporosis should prompt consideration of formal treatment for 3–6 months before surgery, but
should not alter the decision to proceed with a
minimally invasive approach.
Preoperative Considerations
After obtaining a history and performing a physical examination, anteroposterior (AP), lateral,
and flexion-extension radiographs, along with
magnetic resonance (MR) images, are obtained.
The MR image can clearly demonstrate compression of the neural elements, which should correlate with the patient’s neurological examination
and subjective complaints. MR imaging may also
adequately demonstrate alignment and allow for
grading of spondylolisthesis. Patients may present with either unilateral symptoms or bilateral
symptoms. Unilateral symptoms mandate a
transforaminal approach from the symptomatic
side. Bilateral symptoms, in the presence of bilateral foraminal stenosis, may mandate bilateral
facetectomies. In the setting of bilateral facetectomies, bilateral access to the disc space may be
considered; however, the author’s preference is
to perform a unilateral transforaminal interbody.
Careful analysis of the T1-weighted parasagittal
MR image is critical in assessing the neural fora-
men compromise, which may help in deciding
whether facetectomy is needed. In the setting of
central stenosis with symptoms of neurogenic
claudication, severe foraminal stenosis on one
side alone may prompt a transforaminal approach
from that side.
Flexion and extension studies are helpful in
determining the degree of stability of the segment. Extension studies are particularly helpful
in determining how much reduction will be
obtainable by positioning (Fig. 28.1).
The AP and lateral radiographs will be predictive of the type of imaging that can be obtained
with fluoroscopy in surgery. It is valuable to
appreciate a severe coronal imbalance before surgery, so that necessary adjustments can be made
to the fluoroscope and incision. Figure 28.2 illustrates the capacity to adjust the fluoroscope based
on preoperative imaging. In this patient with a
severe coronal imbalance to the left, her symptomatic side, an AP preoperative radiograph
prompted a preoperative AP fluoroscopic image
to guide the angle for the fluoroscope and to
guide the markings for the incisions.
Any concern for scoliosis on AP or lateral
imaging should prompt standing 36-inch scoliosis films. It is important to recognize that there is
an inherent limitation to the amount of lumbar
lordosis that may be restored in a single-level
MIS TLIF. In the author’s experience, 12
degrees of lordosis is at the upper threshold that
can reliably be achieved. Therefore, a significant
mismatch in lumbar lordosis and pelvic incidence warrants careful consideration of the
operative plan.
Surgical Technique
The operative goals of the MIS TLIF include
instrumentation of the pedicles, decompression
of the neural elements, and restoration of the disc
height and segmental lordosis through interbody
placement. The operating room, the scrub technician’s back table, and a Mayo stand should all be
set up to facilitate the flow of the operation to
accomplish these goals. The MIS TLIF, which is
374
L.M. Tumialán
Fig. 28.1 Grade 1 spondylolisthesis. Standing lateral
neutral, flexion, and extension radiographs demonstrating
the mobility of Grade 1 spondylolisthesis. (a) Standing
neutral radiograph revealing a subtle Grade 1 spondylolisthesis. (b) Flexion study clearly demonstrating anterior
translation of the L4 vertebral body on L5. (c) Extension
performed through two paramedian incisions
with instrumentation placed under direct visualization of the bony anatomy and minimal fluoroscopy, has a logical progression of three phases:
instrumentation phase, decompression phase,
and interbody phase. Creating these distinct
phases of the operation allows the entire operative team to anticipate and thereby facilitate, if
not expedite, each phase of the operation.
Operating Room Setup
The patient is positioned on a Jackson table that
has the capacity to rotate, which will facilitate the
decompression phase. Positioning the patient on
the Jackson table will also optimize the capacity
to restore segmental lordosis and minimize blood
loss by decreasing intra-abdominal pressure.
Hyperextension of the hips will also optimize
capturing the maximum lumbar lordosis that can
be achieved. An electrophysiologist connects the
patient for neuromonitoring. The operating
microscope is positioned on the side of the transforaminal approach. The fluoroscope is positioned with the image intensifier opposite the
side of the microscope. It is the author’s preference not to obtain fluoroscopic images at this
study demonstrating near anatomical reduction of the L4
vertebral body on L5. The extension study predicts how
much reduction can be achieved just by positioning the
patient on a Jackson table (Used with permission from
Barrow Neurological Institute, Phoenix, Arizona)
point unless there is a significant coronal imbalance demonstrated on preoperative AP and lateral
radiographs. Instead, the bony landmarks are palpated, and the L4–L5 level is approximated on
the basis of the anterior superior iliac spine.
However, it is commonplace in other institutions
to obtain both preoperative AP and lateral fluoroscopic images before preparing and draping the
patient. If the operative level is L3–L4, then the
planned incisions are shifted upward; for L5–S1,
the incisions are shifted downward. Two incisions 28 mm in length and 3.5–4 cm from the
midline are marked (3.5 cm for patients with a
low body mass index, 4 cm for a high body mass
index). The patient is prepared and draped with
the fluoroscope draped immediately into the field
(Fig. 28.3).
Instrumentation Phase
Step One: Plan and Confirm Incisions At this
point in the operation, because the incisions were
planned with palpation of the bony landmarks,
the level must be confirmed with fluoroscopy. A
spinal needle is passed through the midpoint of
the proposed incision and a fluoroscopic image
taken. The incision is accordingly adjusted,
28 Minimally Invasive Posterior Lumbar Fusion Techniques
375
Fig. 28.2 Severe coronal imbalance requiring an L4–L5
MIS TLIF. (a) Anteroposterior (AP) radiograph demonstrating the severe coronal imbalance (image has been
flipped to match fluoroscopic images taken at surgery).
(b) Preoperative photograph shows a Steinmann pin
placed over the operative segment to plan the incisions
and adjust the fluoroscope. (c) AP fluoroscope image
Fig. 28.3 Planning and confirmation phase of the MIS
TLIF. Photographs of the planning and confirmation
phase. (a) Photograph of the two 28-mm proposed incisions located 3.5 cm off the midline based on landmarks.
(b) Spinal needles are docked onto the facet to confirm the
demonstrating a true lateral despite the coronal imbalance. Optimizing visualization of the pedicles with a true
lateral facilitates instrumentation. (d) Lateral and (e) AP
fluoroscopic images demonstrating placement of the
interbody and the pedicle screws (Used with permission
from Barrow Neurological Institute, Phoenix, Arizona)
level. (c) Lateral fluoroscopic image confirms the ideal
placement of the incision parallel to the disc space (Used
with permission from Barrow Neurological Institute,
Phoenix, Arizona)
376
L.M. Tumialán
Fig. 28.4 Securing the minimal access ports.
Fluoroscopic images demonstrating the securing of the
minimal access ports. (a) Lateral fluoroscopic image demonstrating the initial dilator docked onto the L3–L4 facet
joint. (b) Subsequent lateral fluoroscopic image with the
right-sided expandable minimal access port in position
remarked, and infiltrated with a lidocaine/bupivacaine hydrochloride mixture to begin pain control. Two incisions 3.5–4 cm lateral to the midline
and 28 mm long are made. Blunt dissection is
used to dissect down to the fascia, which is then
divided with cautery. The division of the fascia is
slightly more medial than the skin incision, which
will optimize a trajectory toward the pedicle. At
L3–L4 and L4–L5, the fascial opening has to be
more generous in the rostral direction to reach
rostral pedicle screw entry points. At L5–S1, the
fascial opening needs to be more generous in the
caudal direction to reach the sacral pedicle screw
entry point. Direct palpation of the facet and
transverse processes should be easily performed
before beginning the dilatation process.
and a dilator in position to begin the process on the left
side. After the second minimal access port is secured,
exposure of the pedicle screw entry points can begin
(Used with permission from Barrow Neurological
Institute, Phoenix, Arizona)
not allow for movement in any direction. There is
little utility in subsequent fluoroscopic images
after confirmation of the initial dilator unless the
dilators are dislodged. The length of the retractor
blades is determined by the measurements on the
outside of the dilator and the expandable minimal
access which has been secured in position. If two
surgeons are operating, the process is repeated on
the contralateral side. If one surgeon is operating,
the exposure and the instrumentation is completed on one side before proceeding with the
dilatation and exposure of the contralateral side.
Upon completion of securing the minimal access
ports, the fluoroscope is rolled to the foot of the
bed and kept there until the exposure of the pedicle screw entry points is completed.
Step Two: Secure Expandable Minimal Access
Ports The first dilator is placed over the top of
the facet on one side and confirmed with a fluoroscopic image. The ideal trajectory of the dilator is
parallel to the disc space in the center of the facet
(Fig. 28.4). Once the ideal position is captured,
the first dilator is anchored into position and
sequential dilators placed on top. As the dilators
increase in diameter, they will reach a point
where they will begin to engulf the entire facet.
There is an unmistakable sensation of the final
dilator encompassing the entire facet that does
Step Three: Exposure of the Pedicle Screw
Entry Points Any desire to open the minimal
access port should be suppressed until the entire
facet is exposed. Opening the blades of the minimal access port too soon can result in a compromised exposure from a wall of muscle collapsing
over the anatomy. Under ideal circumstances, a
thin veil of muscle is all that resides over the top of
the facet; this muscle can be quickly painted away
with cauterization. Once the entire facet can be
visualized, exposure proceeds onto the inferior lateral aspect of the facet where the transverse process
28 Minimally Invasive Posterior Lumbar Fusion Techniques
377
of the caudal segment will be quickly encountered.
At this point, it is reasonable to begin to open the
inferior blade of the expandable retractor to further
visualize the pedicle screw entry point. Within the
first few minutes of exposure, the caudal pedicle
screw entry point should come into view.
Following the inferior articular process in the
rostral direction will locate the pars interarticularis and more rostrally to the pedicle screw entry
point. With exposure of the pars interarticularis, a
gradual opening of the rostral blade will provide
access to the transverse process and the rostral
facet. It is essential to prevent any disruption of
the facet capsule of the facet located above to
mitigate the risk of adjacent segment degeneration. The focus for exposure of the rostral pedicle
screw entry point should be the transverse process and the pars interarticularis first with the
inferior lateral aspect of the facet last.
Fluoroscopy at this phase is of little utility;
rather, it should not be used until the transverse
process of the levels to be instrumented can be
clearly visualized. The pedicle is reliably at the
junction of the midpoint of the transverse process,
lateral inferior facet, and pars interarticularis.
When all four of these entry points can clearly be
visualized, the fluoroscope is rolled back into
position. The drill is then used to make a small
opening at the junction of these three anatomical
landmarks after confirmation with a lateral fluoroscopic image. A pedicle probe with 15–20 degrees
of angulation (at L3 or L4) or 20–25 degrees of
angulation (at L5 or S1) is then used to probe into
the pedicle with the sagittal trajectory parallel to
the superior endplate of the vertebral body.
Probing the pedicle is a purely tactile process.
There is an unmistakable sensation of having the
tip of the pedicle probe advance as it displaces the
cancellous bone within the center of the pedicle.
If significant resistance is met, it is likely that a
cortical wall has been encountered. Forcing the
probe at this point is a recipe for a breach. It is a
worthwhile endeavor to remove the probe, evaluate the entry point, and consider an AP image. If
the probe advances with a converging trajectory,
it need not be advanced more than 30 mm. Most
pedicle probes are graduated with markings every
5 or 10 mm. If electrophysiological monitoring is
used, the pedicle probe may be stimulated to
20 mA. The generation of a compound motor
action potential will mandate careful evaluation
of the entry point, an AP image, and identification
of the breach with a ball-tipped probe [12]. If no
compound motor action potential is generated,
the pedicle probe is removed, and the ball-tip
probe confirms intact medial, lateral, superior,
and inferior walls along with a bottom within the
vertebral body. A tap is used to further prepare for
the pedicle screw. Typically, the hole for the pedicle is undertapped by 1 mm (i.e., if the intention
is to place a 7.5-mm- diameter screw, then a 6.5mm tap is used). Knowing the length of the tap is
also valuable in determining the length of the
screw. Once the threads of the tap have been buried, a lateral fluoroscopic image can determine
the ideal length of the pedicle screw to be placed
(Fig. 28.5). The process described above is
repeated for all pedicle screws. If two surgeons
are operating, simultaneous confirmation of the
pedicle screw entry points is a strategy to minimize fluoroscopy. After all the pedicles have been
tapped, all four screws may be secured into position. More recent pedicle screw configurations
allow for either headless screws or lower profile
tulip heads, neither one of which interferes with
the decompression phase. An alternative is to
place guidewires to mark the pedicle screw holes.
Decompression Phase
Step One: Exposure of the Lamina and Pars
Interarticularis
the pedicle screws, the fluoroscope is now rolled
to the head of the bed and the operating microscope placed into position. The base of the spinous process is exposed, along with the entire
hemilamina extending out to the pars interarticularis. When all the bony anatomy can be clearly
visualized from pedicle screw to pedicle screw
and to the base of the spinous process, drilling of
the osteotomy cuts may begin.
Step Two: Osteotomy Cuts
cut is a horizontal osteotomy made just below the
rostral pedicle screw (Fig.
After successful placement of
The first osteotomy
28.6). A drill is used to
378
L.M. Tumialán
Fig. 28.5 Pedicle screw placement sequence. (a) Lateral
fluoroscopic image with a drill at the junction of the midtransverse process, inferior lateral facet, and pars interarticularis. (b) Pedicle probe with a converging trajectory of
15–20 degrees parallel to the endplate advances with the
unmistakable tactile feel of displacing cancellous bone.
(c) After the integrity of the pedicle is ensured with a ball-
thin the bone down to the ligamentum flavum,
extending the osteotomy medial into the lamina
to the junction of the spinous process. The next
osteotomy is a vertical osteotomy cut that undercuts the base of the spinous process so that the
contralateral recess may be reached. Once again,
drilling continues until the bone is thinned to the
level of the ligamentum flavum. Completion of
the osteotomy cuts allows for removal of the inferior articular process and lamina. Removal of this
large segment of bone provides a large amount of
autograft that can be milled and used for graft in
the disc space. Access to the superior articular
process and caudal lamina allows for an osteotomy of the superior articular process and the
superior aspect of the rostral lamina. The caudal
pedicle screw is a guide for the level of the oste-
tipped probe, the pedicle is undertapped. The length of the
tap threads determines the ideal length of the screw. (d) In
this case, the 5.5-mm tap measured 37.5 mm and a
40-mm-long, 6.5-mm-diameter pedicle screw was placed
(Used with permission from Barrow Neurological
Institute, Phoenix, Arizona)
otomy of the superior articular facet. Extending
the bone work medially and caudally to the pedicle screw allows for a generous foraminotomy of
the traversing root and the insertion of the ligamentum flavum for the segment.
Step Three: Resection of the Ligamentum
Flavum After bony resection, the ligamentum
flavum may be accessed from insertion point to
insertion point. Rotating the operating table away
from the surgeon is helpful in accessing the contralateral recess. A plane may be developed over
the top of the thecal sac with a right-angle balltipped probe and a Kerrison punch used to resect
the ligamentum flavum. A piecemeal approach is
one way to complete the decompression. Another
viable alternative is to identify the insertion