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multiple levels (> 3 levels) are done with posterior instrumentation xation being
performed 2–3days after XLIF [28–30]. If signicant motor disturbance, pain dys-
esthesia, lower limb myasthenia, and decrease in hematocrit are present, a magnetic
resonance imaging (MRI) or computed tomography (CT) should be conducted to
rule out a psoas hematoma.
For all patients, restrictions on bending, lifting, and twisting of the lumbar spine
are advised until a solid fusion mass can be expected to form, which usually takes a
minimum of 4–6weeks. Patients may use a soft lumbar corset for a back support
and pain control. A stronger clamshell brace is usually not necessary.
Outcomes
Phillips etal. published a multicenter prospective study of 107 patients undergoing
XLIF for degenerative scoliosis with 24-month follow-up; the mean Cobb angle
improved from 20.0° to 15.2°. The degree of correction did not correlate with
clinical outcome at 24months (P<0.001) [31]. The authors report an overall com-
plication rate of 24% with 12% considered major and no mortalities. They note
their complication rate to be lower than that of traditional surgical approaches,
which have been reported as high as 66% [31]. The authors propose the lower rate
of complications is due to the fact that the abdominal vasculature is not mobilized,
the ureter is not manipulated, and the peritoneal cavity is not retracted in XLIF
[31]. Similar results were demonstrated in a smaller series of 30 consecutive
patients undergoing XLIF for scoliosis including improvement in clinical scores
and a reportedly lower complication rate of 26.6% compared to traditional
approaches [32].
A recent systematic review of 21 studies reports that XLIF was successful in
improving VAS pain scores and Oswestry disability index outcomes [11]. Although
XLIF was effective at restoring coronal deformity (weight means: coronal segmental
Cobb angle 3.6–1.1°; coronal regional Cobb angle 19.1–10°), it appears to have a
smaller impact on lumbar lordosis and sagittal balance as compared to transforami-
nal lumbar interbody fusion (TLIF) or posterior lumbar interbody fusion (PLIF)
[11]. Some authors advocate the use of an additional lumbar interbody fusion at the
L5-S1 level to help achieve optimal deformity correction [33]. However, limitations
at deformity correction with XLIF are counterbalanced by the advantages of the
approach over TLIF/PLIF in reducing the risk of dural tear, nerve root, and paraspi-
nal muscle injuries [11]. XLIF also provides an opportunity to place an implant with
higher prole and greater width than TLIF or PLIF and provide a better restoration
of disc height [11]. In patients with scoliosis and concomitant neurological symp-
toms, neural decompression through laminectomy, facetectomy, or similar proce-
dures is indicated for symptom relief. However, improvement in leg and back pain
and improvement in radiographic parameters have been demonstrated with indirect
spinal decompression utilizing ligamentotaxis created with the anterior and poste-
rior longitudinal ligaments during XLIF [34].
J. H. Weinreb et al.
207
In a retrospective data analysis at two centers examining 84 cases of XLIF
with and without posterior spinal fusion, patients undergoing the combined
XLIF/PSF had increased estimated blood loss (245 vs 81ml, p< 0.0001) and
length of stay (3.3 vs 2.1days, P=0.002). The authors report that, according to
the literature, thigh weakness/numbness appears to be the most common post-
operative complaint. They attribute this to trauma of the psoas muscle during
the approach. The majority of these cases resolved with time, but a small per-
centage of patients with motor or sensory decits persisted, which is similar to
those following traditional direct anterior approaches and lower than those fol-
lowing traditional posterior approaches [35]. Additionally, a supra-psoas shal-
low docking approach has been described which suggests that many of these
postoperative morbidities may be avoided by docking on top of the psoas instead
of passing through it [36, 37].
Vertebral body fractures have also been reported in several case studies fol-
lowing XLIF with interbody cage placement. Predisposing factors for vertebral
body fractures have been suggested to include osteoporosis, high body mass
index, multilevel constructs, cage subsidence, and xed-angle lateral plate
design [38–40]. Cage subsidence, another concern following XLIF which
results in postoperative disc height loss, has been reported in several stand-
alone XLIF series [39, 41]. In one study, subsidence with disc height loss of
50–100% was seen in 30% of standard 18mm AP length cages following stand-
alone XLIF.Increasing the AP length to 22mm in this study decreased this rate
to 11%, and the authors suggest that using a larger interbody cage, size may
decrease subsidence [41].
Case Study
Figure 24.3a, b depict the lateral and AP radiographs of a 45-year-old female who
presented with severe sciatic neuritis down her right leg. The AP radiograph shows
a 51-degree rightward lumbar scoliotic curve, and the lateral radiograph shows ade-
quate sagittal balance.
The patient failed conservative therapy and, due to her continued symptoms,
elected to undergo multilevel lateral interbody fusion with anterior lumbar interbody
fusion and plating at L5-S1. Positioning of the patient is shown in Fig.24.3c, while
postoperative radiographs are shown in 24.3d.
At a second stage 14 days later, the patient underwent percutaneous pedicle
screw instrumentation L1-pelvis to augment the stability of the construct.
Postoperative AP and lateral radiographs are shown in Figs.24.3e, f. The rightward
lumbar curve was corrected to 15°. No blood transfusion was required.
The patient recovered well postoperatively and now fouryears out of surgery has
had maintenance of their deformity correction, no reoperation, and lasting relief of
her symptoms.
24 Lateral Lumbar Interbody Fusion forLumbar Scoliosis
208
Conclusion
Minimally invasive spine surgery as represented by lateral interbody fusion is a new
but growing eld of spine surgery. The lateral approach has inherent advantages as it
is less traumatic to the soft tissues and decreases the risk of neural element injury that
is present with traditional transforaminal and posterior approaches. It also avoids vital
neurovascular structures and bowel, which are dangers of the anterior approach. This
minimalist approach tends to lower patient morbidity and allow for faster recovery.
However, the lateral approach is not without its own risks, including damage to
the psoas muscle and the overlying genitofemoral nerve which results in hip exion
weakness and paresthesias in the inguinal region, respectively. Moreover, exposure
and access are limited, especially in the L5-S1 and T12-L1 interspaces.
XLIF may be used to treat foraminal stenosis via indirect decompression of the
neural elements with restoration of disc height. The lateral approach has also been
shown to be effective in addressing scoliotic deformity with measurable improve-
ment in the coronal plane. The impact on sagittal plane deformity is more limited
in comparison to anterior and posterior approaches. In many cases, the lateral
approach must be supplemented by an additional posterior or anterior procedure.
Further research is warranted to further characterize the long-term outcomes of
lateral interbody fusion and to develop new techniques that may enhance its efcacy
in decompression and curve correction.
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(c). Postoperative radiographs after the rst stage (d) and the second stage (e, f)
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211© Springer Nature Switzerland AG 2020
J. R. O’Brien et al. (eds.), The Resident’s Guide to Spine Surgery,
https://doi.org/10.1007/978-3-030-20847-9_25
Chapter 25
Percutaneous Lumbar Screws
BriannaLindseyCohen, KarthikMadhavan, andMichaelY.Wang
Introduction
Minimally invasive procedures are growing in popularity due to tissue sparing and
minimal postoperative pain. This chapter describes percutaneous lumbar fusion
techniques, including advantages and disadvantages, techniques, complications,
and patient selection strategies.
Pedicle screw instrumentation can be utilized to stabilize fusion for various spi-
nal pathologies via the creation of a rigid and stable construct. Recent developments
in instrumentation have enabled preservation of muscles, ligaments, and bony struc-
tures of the spine that help facilitate recovery and improve outcomes. Furthermore,
percutaneous techniques preserve muscle and ligaments adjacent segment disease.
With these advances in percutaneous pedicle instrumentation and numerous advan-
tages over the traditional method, interest in this approach has and will continue to
rise [1, 2].
At rst, learning and utilizing this new technique may seem difcult; however,
there are some basic principles outlined in this chapter to help guide the surgeon in
its safe and effective utilization [1, 3].
B. L. Cohen · M. Y. Wang
Department of Neurological Surgery and The Miami Project to Cure Paralysis,
University of Miami Miller School of Medicine, Miami, FL, USA
K. Madhavan (
*)
Department of Neurological Surgery and The Miami Project to Cure Paralysis,
University of Miami Miller School of Medicine, Lois Pope Life Center, Miami, FL, USA
212
Indication
Percutaneous xation can be performed in the majority of circumstances in which
open pedicle screw xation is indicated. Specically, this technique can be utilized
in order to provide supplemental xation to interbody or posterior fusion proce-
dures, to stabilize the spine in cases of infection or tumor, or as a temporal internal
brace in a trauma setting [4–6].
Advantages andContraindications
Minimally invasive surgery is becoming increasingly popular in the treatment of
both degenerative and traumatic disorders. Percutaneous lumbar fusion enables the
insertion of hardware under the guidance of uoroscopy or navigation fostering
accurate multilevel screw placement while minimizing the trauma associated with
the traditional open approach. The reduced paraspinal muscle damage achieved in
this approach has led to decreased operative blood loss, postoperative pain, and
narcotic usage. Additionally, the use of the percutaneous technique has translated to
earlier hospital discharge and return to work, a milder spike in serum/urine muscle
breakdown products, and greater trunk strength. Furthermore, percutaneous xation
minimize muscle injury as the muscles are split as opposed to being detached or
retracted. Thus, because it spares soft tissue and muscle retraction, percutaneous
screw xation enables medial angulation required for screw placement. This is in
opposition to the open approach, in which the fascia-muscles, if not released exten-
sively, may act as an obstacle that can precipitate a lateral breach. Moreover, the use
of the AP view for pedicle cannulation fosters efciency as it enables two skilled
surgeons to work simultaneously, further decreasing operative time [1–3, 5, 7–9].
With the advancement of new technologies, minimally invasive techniques are
gaining a role in more complex procedures in the spine. For this chapter, we will
consider multilevel procedures as those needing a rod passed through at least four
screws. Multilevel minimally invasive procedures can be used to treat many condi-
tions ranging from traumatic injuries to adult and children spinal deformities, infec-
tions, and tumors [5, 10].
However, this procedure should not be performed if unable to visualize pedicle
anatomy with radiographic imaging or navigation. Rod placement strategies will be
discussed in a later section [5].
Possible disadvantages of percutaneous screw xation include potentially increased
operative times in less experienced surgeons, the need for a steep learning curve, and
loss of surgeon control, feel, or sight of the open anatomy. Thus, the use of this
approach may be limited by the surgeon’s willingness and ability to perform it [2].
Moreover, as imaging modalities are vital to percutaneous screw xation, other
approaches should be considered in patients in whom proper images cannot be obtained
or interpreted. This may be due to obesity, osteopenia, retained abdominal contrast,
severely deformed anatomy, or low-quality C-arm image intensiers [3, 5, 8, 9, 11].
We will explore possible strategies to overcome some of these challenges later on.
B. L. Cohen et al.
213
In addition, these imaging modalities increase radiation exposure to the patient
as well as the surgical team. Ionization radiation has been associated with a range of
morbidities, such as skin erythema or ulceration, cataract formation, reduced fertil-
ity or sterility, and malignancies. However, the radiation exposure to the eyes,
extremities, and deep tissues in the placement of pedicle screws is far below the
occupational exposure limit, thus this procedure has been deemed safe. Still, mea-
sures should be taken to reduce its exposure. These include pulsed image acquisi-
tion and lead shielding using lead aprons, thyroid shield, and lead-impregnated
gloves and goggles. It is recommended that the surgeon be positioned farthest from
the beam source, and all hands should be kept as far as possible from the source in
order to decrease radiation exposure [12–14]. Navigation and robotics have also
enabled minimization of radiation exposure to surgeon, staff, and patient.
Proper Imaging Technique
Percutaneous screw placement requires reliance on intraoperative imaging, as there
are vital structures in close proximity and minimal exposure of spinal anatomy.
Although there are options in terms of imaging methods, the primary imaging
modality in the operating room for minimally invasive procedures is the C-arm. The
C-arm is portable and readily available in most hospitals, and it creates two-
dimensional photographs of the bony anatomy by superimposing all of the tissue
shadows that have been transversed by the uoroscopic beam [2, 5].
To ensure the success of this technique, proper AP and lateral images must be
obtained. On a properly aligned true AP view, the pedicles are symmetrical and lie
just inferior to the upper endplate. The anterior and posterior margins of the upper
endplate should be superimposed, and no double endplate shadow should be seen.
Additionally, the pedicles’ outlines should be on the upper half of the vertebral
body, and the spinous process shadow should be midline between the pedicles [1, 5,
8]. For lateral images, a at superior endplate should again be seen, with the lateral
aspects of both pedicles seen and superimposed. When rotation of the segment has
been eliminated, only a single shadow should be seen on the posterior cortex of the
vertebral body [9].
In obtaining both true AP and lateral images, it is preferable to tilt the bed to one
side, leaving the C-arm in the 0° and 90° positions. Additionally, due to the normal
lordosis of the spine, the C-arm may need to be adjusted for each spinal level in
order to keep the pedicle screws parallel to the endplates [8].
Patient Positioning
In the percutaneous placement of lumbar screws, appropriate patient positioning
and the radiolucent bed is necessary to ensure uoroscopic views. The abdomen is
free of compression, and all bony and vital structures are padded. Care should be
25 Percutaneous Lumbar Screws
214
taken to ensure good orthogonal alignment for imaging. Some cases may require
slightly altered positioning due to differences in each patient [2, 4, 5, 8].
Surgical Technique
Percutaneous Pedicle Cannulation withTrue AP
(Anteroposterior) Imaging
Once patient is positioned and properly draped, each vertebra is identied uoro-
scopically based on rib counting from above or sacrum from below. Once the levels
are identied, the uoroscopy is bought to position for the desired level. As men-
tioned above, generally, each vertebral level needs a slightly different sagittal angu-
lation of the C-arm due to the sagittal prole of the spine [5, 8].
It is important to identify the appropriate trajectory for each vertebral level. To
do so, the surgeon aligns a Kirschner wire (K-wire) horizontally on the skin such
that the wire is in line with the center of the pedicles in midline and marked. This is
followed by another image along the upper endplate of the vertebral body (VB). The
AP image is adjusted to be in the same plane as the horizontal axis of the endplate.
Now the K-wire is placed on the lateral aspect of the VB along the lateral border of
the pedicles. The vertebral level and necessary sagittal angulation of the C-arm may
be marked on the skin to facilitate rapid return to proper view for each level. This
process is repeated for each vertebral level to be instrumented [1, 5, 9]. It is recom-
mended to incise the skin slightly lateral to the lateral border of the pedicle on AP
imaging in order to ensure medial angulation of screws. A K-wire is placed on the
skin so that it is vertically in line with the lateral aspect of the pedicle. Once con-
rmed with imaging, these cephalocaudal lines are marked on the skin along the
K-wire in order to help guide incision locations, which are marked about 1cm lat-
eral to these lines. Obese patients may require the incisions to be placed more lateral
to accommodate for the increased tissue depth [5].
Local anesthetic should be injected into the dermis prior to incision in order to
expand the skin to decrease the incision length and scar. Furthermore, a slightly
larger incision is preferred to avoid the use of tubular dilator retractors, as these can
lead to dusky or necrotic looking skin. The skin is incised down through the subcu-
taneous tissue and the thoracolumbar fascia is identied. The fascia and muscle may
be incised or left intact. Some prefer to incise the fascia in line with the muscle
bers to decrease the subsequent tension on the K-wire and dilators. The muscle
bers are then split via blunt dissection, and the surgeon can now palpate the facet
joint and transverse process [1, 2, 5, 8].
Care should be taken to ensure that incisions are large enough to accommodate
the instruments, as the instrumentation for muscle dilation and soft tissue protection
varies in terms of size. Next, a Jamshidi needle is inserted into the incision and
docked over the junction of the transverse process and facet, located adjacent to the
lateral aspects of the facet joints. The needle is held in place with long Kocher
B. L. Cohen et al.
215
clamps, while an AP image is obtained in order to ensure proper positioning. The
needle tip should be located directly over the mid-lateral wall of the pedicle, termed
3 o’clock on the right side, and 9-o’clock on the left. The AP view is also utilized to
ensure that the needle tip is not angled too cranially or caudally. If the needle is not
correctly positioned, it should be readjusted and its position should be reconrmed
with AP imaging. Once proper positioning is conrmed with imaging, the Jamshidi
needle should be tapped gently with the mallet in order to penetrate a few millime-
ters into the bony cortex. Positioning should be veried, yet again, by another AP
image, as the needle tip may have slipped due to the sloped nature of the bony sur-
face over the pedicle entry [2, 5, 15].
The shaft of the Jamshidi needle should appear in parallel with the upper end-
plate to enable the cannula to pass through the center of the pedicle. In order to
determine the appropriate depth of needle penetration into the pedicle, the shaft is
marked 20mm above the skin edge for the length of the pedicle. Then, while main-
taining the Jamshidi needle shaft aligned with the uoroscopic beam, the needle is
tapped gently with the mallet to break the cortical bone followed incremental force
to get to the depth of 20mm. An AP image should be obtained to ensure proper
positioning of the needle relative to the pedicle shadow. The needle tip should be
approximately at the base of the pedicle and should be viewed within the pedicle
shadow, approaching but not beyond, the medial border of the pedicle till the
Jamshiti needle is beyond 20-mm depth [5].
The K-wire is then inserted through the cannula and into the cancellous bone of
the vertebral body. This cancellous bone should be palpated at the base of the nee-
dle, and it should have a slight “crunchy” feel as the wire is driven through it. The
K-wire can then be advanced 15–20mm beyond the tip of the needle and into the
vertebral body. The cannula is then removed while holding the K-wire in place [5,
8, 15, 16].
The above technique is then repeated for all indicated levels, maintaining the
C-arm in the true AP position. A nonpenetrating clamp can be used to hold the wire
against the drape in order to avoid interfering with subsequent cannulation of indi-
cated levels. Once all appropriate pedicles have been cannulated and the K-wires
have been inserted, a proper AP image is obtained in order to visualize all the
K-wires. This image can be saved to one of the screens of the C-arm monitor in
order to compare the K-wire position on this AP view with the lateral image. Then,
the C-arm may be shifted to the lateral position and another image obtained. The
surgeon should ensure that each K-wire is in the appropriate position in both the AP
and lateral views [8, 15].
K-wires that are not in proper position should be removed and reinserted using
the above procedure either via the same or a new pilot hole. K-wires that are solely
through the posterior half of the vertebral body may be advanced further. However,
caution must be taken, as a laterally placed K-wire predisposes an anterior breach,
even though the tip appears well behind the anterior vertebral body wall on the lat-
eral image. Thus, the K-wire is not routinely advanced to this point, but it should be
advanced deep enough to be located in the anterior half of the body in order to avoid
unintentional pullout when removing the tap [5, 15].
25 Percutaneous Lumbar Screws