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Procedure 34 | The Transpsoas Approach for Thoracolumbar Interbody Fusion 319
S T E P 3 P EA R L S
• When performing this procedure at
rostral levels, the diaphragm can push
the surgeon’s dilators and retractor
downward. Therefore it is important to
push the diaphragm out of the way
when coming in with the PAK needle
and various dilators.
• The authors secure the retractor to
the vertebra with a pin. Depending
on the angulation of the retractor and
the location of the retractor on the
vertebral body, the authors choose
a vertebral body where the risk of
injuring a segmental vessel is least
likely, and, if this is the rostral toward
the chest, they prefer to secure the
retractor to the more rostral vertebra
to maximize resistance against the
rib cage.
Step 3
n
The C-arm is swung to the anteroposterior position.
n
Serial dilators are used to sequentially dilate the psoas muscle. Figure 34-4, A
is a fluoroscopic image showing first dilator being passed over the guidewire
down to the level of the disk space. Figure 34-4, B shows serial dilators being
placed in this matter to open a working channel between fibers of the psoas
muscle. The dilators should be gently rotated back and forth during placement
to separate the fibers of the psoas.
n
Free-run and triggered electromyography are only useful in identifying motor
nerve structures and do not aid in identifying any sensory branches.
n
Dilator placement may elicit a free-running electromyographic response, which
indicates mechanical irritation to the motor nerve structures. This is just an
indication of mechanical contact.
n
Some manufacturers offer directional stimulated dilators, which use triggered
electromyography to identify the location of motor nerve structures. The dilator
is rotated during insertion, while constant electrical current is applied or variable
current stimulation is performed. The subsequent electromyographic response
assists with motor nerve identification relative to the dilator. Directionally stimulated dilators of increasing size are inserted sequentially until the retractor is
placed over the final dilator.
A
FIGURE 34-4, A-B
B
320 Procedure 34 | The Transpsoas Approach for Thoracolumbar Interbody Fusion
n
At this point, a small surgical field is within view at the deep end of the retractor.
Some surgeons prefer to perform the procedure through this port, while others
choose to expand the retractor to allow a larger field of vision.
n
A shallow or short docking retractor technique has also been described for dis-
secting through the psoas to identify any neural structures before docking
against the vertebral body.
n
Direct field stimulation using a ball-tip stimulating probe can be helpful for
identifying any motor nerve structures that may be pressed between the annulus
and the retractor.
n
Any suspected neural structures can be swept out of the field.
n
The ball-tip probe stimulator should be used to sweep the area before pin or
shim placement for anchoring of the retractor system. The retractor is then
secured to the patient with a pin in the vertebra.
n
The retractor is then further secured to the table using an articulating arm
(Figure 34-5).
A
FIGURE 34-5, A-B
B
Procedure 34 | The Transpsoas Approach for Thoracolumbar Interbody Fusion 321
S T E P 4 P EA R L S
• Great care is taken not to violate the
anterior/longitudinal ligament. The
anterior longitudinal ligament should
be identified before starting the
diskectomy.
• Frequent fluoroscopic shots should
be taken to ensure that instruments
are not being past pointed into the
abdomen.
Step 4
n
A radical diskectomy is performed under anteroposterior (AP) fluoroscopy. A
no.15 blade is used to incise the disk. Great care is taken not to violate the
anterior/longitudinal ligament. The anterior longitudinal ligament should be
identified before starting the diskectomy.
n
Subsequently, a small Cobb elevator is taken across the disk space under AP
fluoroscopy and is confirmed to pass just beyond the disk space. This is done
with the aid of a mallet. Figure 34-6 is an AP fluoroscopic image showing a
small Cobb elevator being passed into the disk space. Note the presence of the
still-present guidewire, which is removed only after passing the small Cobb
elevator initially into the disk space. Also note the retention pin, which secures
the retractor, in this case, to the inferior vertebrae.
FIGURE 34-6
322 Procedure 34 | The Transpsoas Approach for Thoracolumbar Interbody Fusion
n
The Cobb elevator is then rotated to release the contralateral annulus. A small
Cobb elevator is passed all the way across to the contralateral annulus (Figure
34-7, A) and then rotated to release the annulus (Figure 34-7, B). This is critical
in correcting deformity. Subsequently, a larger Cobb elevator is used for the
same procedure and to obtain greater release.
n
Care should be taken to avoid injury to contralateral neural and vascular struc-
tures when releasing the contralateral annulus.
n
A series of curettes (Figure 34-8, A), rasps (Figure 34-8, B), a uterine curette,
and rakes are used to radically excise the disk and prepare the end plates. This
is once again performed under lateral fluoroscopic guidance.
A
FIGURE 34-7, A-B
A
FIGURE 34-8, A-B
B
B
Procedure 34 | The Transpsoas Approach for Thoracolumbar Interbody Fusion 323
S T E P 5 P EA R L S
• If the trial is bouncing while attempting
insertion, this generally means that
not enough of a diskectomy has been
performed. The trial should be removed
if it does not pass readily into the disk
space, or more disk material should be
removed.
• For dosing of RhBMP2/ACS, the authors
use 2 to 4 mg in each polyether ether
ketone (PEEK) cage.
• They also use demineralized bone
matrix and pack it into the disk space
before removing the retractor.
• In cases where the chest has been
entered and the purse-string closure
has been performed, the authors
have not had to use chest tubes.
Postoperative radiographs have shown
the patient to have less than 10%
pneumothorax, which can be
monitored.
S T E P 5 P IT FA L L S
• Great care should be taken to preserve
the anterior longitudinal ligament. If,
at any point, there is a sudden give
of the trial, most likely the anterior
longitudinal ligament has been violated.
• If the anterior longitudinal ligament has
been violated, the procedure can be
salvaged by eventually directing the
trials and cage more posteriorly. Great
care, however, should be taken to avoid
this situation, because any violation of
the anterior longitudinal ligament puts
the vascular and viscous structures at
risk.
Step 5
n
Serial trials are then placed into the disk space, and positions are confirmed
under AP fluoroscopy.
n
After each trial, more disk material is removed.
n
The final trial should fit snugly into the disk space (Figure 34-9).
n
The disk space is then irrigated, and a polyether ether ketone (PEEK) spacer
filled with demineralized bone matrix and recombinant human bone morphogenetic protein-2/absorbable collagen sponge (RhBMP2/ACS) (Infuse, Medtronic
Minneapolis, Minn. Tenn.) is malleted into position.
FIGURE 34-9
324 Procedure 34 | The Transpsoas Approach for Thoracolumbar Interbody Fusion
n
AP (Figure 34-10, A) and lateral (Figure 34-10, B) fluoroscopy imaging confirms
placement of the spacer before the removal of the insertion handle. Figure
34-10, C is a photograph of the actual prosthesis in place.
n
The retractor is then removed. The retractor should be removed with the blades
open to visualize the retroperitoneal contents and ensure there is no bleeding.
In addition, this ensures that any demineralized bone matrix placed does not
come out into the retroperitoneal space.
n
In cases where the chest is entered, a red rubber catheter is inserted through
an incision communicating with the thoracic cavity. The thoracic incisions are all
closed watertight.
• The incision through which the catheter is coming out is closed last with a
purse-string stitch placed around the catheter.
• The anesthesiologist is asked to have the patient perform a Valsalva
maneuver.
• At the same time, the catheter is connected to suction and then pulled out
while the purse-string suture is closed in watertight fashion.
A
C
FIGURE 34-10, A-C
B
Procedure 34 | The Transpsoas Approach for Thoracolumbar Interbody Fusion 325
P O S T OP E R AT IV E P I T F A L L S
• Complications commonly seen, such
as thigh paresthesias and hip flexor
and quadriceps weakness, are usually
related to neural structures that have a
close relationship to these muscles.
• Retroperitoneal structures, such as the
ureter and kidney, can be injured, in
addition to bowel and vasculature,
although the rates of these injuries are
probably significantly lower than in
traditional abdominal approaches.
• If at any point there is excessive
bleeding from this approach, the
exposure can be readily converted to a
laparotomy and/or thoracotomy.
Postoperative Care and Expected Outcomes
n
Typically, the authors will follow surgery, on the same day or on a different day,
with posterior fixation.
n
With a deformity correction, rotational deformity appears not to be corrected
using this methodology; rather, this can be corrected using pedicle screw
instrumentation.
n
Postoperatively, a substantial portion of the patient’s complaint is of thigh
dysesthesias. These tend to improve with time and generally resolve.
n
A very small percentage of patients may have transient psoas or quadriceps
weakness. To minimize this risk, the authors avoid using a posterior blade,
especially at L4-5. In addition, should there be any sustained neural irritation
during the dilation stages of the muscle or placement of a retractor, they consider avoiding that level.
n
On several occasions, a nerve has been visualized in the field, and the authors
decided to perform interbody fusion by another approach.
Evidence
Anand N, Baron EM, Thaiyananthan G, Khalsa K, Goldstein TB. Minimally invasive
multilevel percutaneous correction and fusion for adult lumbar degenerative
scoliosis: a technique and feasibility study. J Spinal Disord Tech 2008;21:459-67.
This is a technical paper reviewing the transpsoas technique, among other
minimally invasive spine surgery (MISS) techniques used for circumferential
deformity correction and fusion. Experience with 12 cases is reported. The mean
surgical time for anterior procedures was 4.01 hours (standard deviation [SD]
1.88), and for posterior procedures, it was 3.99 hours (SD 1.19). The mean Cobb
angle preoperatively was 18.93 degrees (SD 10.48), and postoperatively it was
6.19 degrees (SD 7.20).
Anand N, Rosemann R, Khalsa B, Baron EM. Mid-term to long-term clinical and
functional outcomes of minimally invasive correction and fusion for adults with
scoliosis. Neurosurg Focus 2010;28:E6.
This study presented a 22-month mean follow-up of 28 patients undergoing
transpsoas lumbar interbody fusion as part of a minimally invasive deformity
correction. The mean Cobb angle was 22 degrees (range 15 to 62 degrees),
which corrected to 7 degrees (range 0 to 22 degrees). The major complications
found were two patients with quadriceps palsies, from which they recovered
within 6 months; one patient with a sustained retrocapsular renal hematoma;
and one patient with an unrelated cerebellar hemorrhage. The authors
concluded that minimally invasive surgical correction of adult scoliosis results
in midterm to long-term outcomes similar to traditional surgical approaches.
Whereas operating times are comparable with those achieved with open
approaches, blood loss and morbidity appear to be significantly decreased in
patients undergoing minimally invasive deformity correction.
Davis TT, Bae HW, Mok MJ, Rasouli A, Delamarter RB. Lumbar Plexus Anatomy
within the Psoas Muscle: Implications for the transpsoas Lateral Approach to the
L4-5 Disc. J Bone Joint Surg Am. 2011 Aug 17;93(16):1482-7.
This article reviewed a neural structures of the lumbar plexus in the psoas
muscle of 18 cadaveric specimens.
Ozgur BM, Aryan HE, Pimenta L, Taylor WR. Extreme Lateral Interbody Fusion
(XLIF): a novel surgical technique for anterior lumbar interbody fusion. Spine J
2006;6:435-43.
This is an original-technique paper regarding the transpsoas approach. No
complications were seen in the authors’ first 13 patients. The authors concluded
that this approach allows anterior access to the disk space without using an
approach surgeon or having the complications of an anterior intraabdominal
procedure.
326 Procedure 34 | The Transpsoas Approach for Thoracolumbar Interbody Fusion
Wang MY, Mummaneni PV. Minimally invasive surgery for thoracolumbar spinal
deformity: initial clinical experience with clinical and radiographic outcomes.
Neurosurg Focus 2010;28:E9.
A retrospective study of 23 patients was undertaken to assess the clinical and
radiographic results with minimally invasive surgery performed for adult
thoracolumbar deformity. All patients underwent a lateral interbody fusion,
followed by posterior percutaneous screw fixation and possible minimally
invasive surgical transforaminal lumbar interbody fusion, if fusion near the
lumbosacral junction was necessary. The mean follow-up was 13.4 months.
Complications included two returns to the operating room, one for
cerebrospinal fluid (CSF) leakage and the other for hardware pullout. In this
study 30.4% experienced new thigh numbness, dysesthesias, pain, or weakness,
and in one patient, these new symptoms were persistent.
P R O C ED U R E 3 5
Lumbar Total Disk
Arthroplasty
Michael F. Duffy and Jack E. Zigler
I N D I CAT I O NS P I T F A L L S
• Active systemic infection or infection
localized to the site of implantation
• Osteopenia or osteoporosis defined
as dual energy x-ray absorptiometry
(DEXA) bone density–measured T-score
less than −1.0
• Bony lumbar spinal stenosis
• Allergy or sensitivity to implant
materials (cobalt, chromium,
molybdenum, polyethylene, titanium)
• Isolated radicular compression
syndromes, especially resulting from
herniation
Indications
n
Symptomatic, single-level degenerative disk disease in the lumbar spine (L3-S1)
in skeletally mature patients with no more than grade I spondylolisthesis at the
involved level and who have failed nonsurgical treatments for at least 6 months.
Examination/Imaging
n
Figure 35-1, A and B show flexion/extension lateral radiographs showing disk
height loss and degeneration at L5-S1. Note the absence of instability.
A
FIGURE 35-1, A-B
B
328 Procedure 35 | Lumbar Total Disk Arthroplasty
• Pars defect
• Involved vertebral end plate
dimensionally smaller than 34.5 mm in
the medial to lateral and/or 27 mm in
the anterior to posterior directions
• Clinically compromised vertebral bodies
at affected level because of current or
past trauma
• Lytic spondylolisthesis or degenerative
spondylolisthesis of grade greater
than 1
• Scoliosis (lumbar curve greater than
11 degrees)
• Absolute contraindications for an
anterior approach are significantly
calcified aorta, and extensive abdominal
wall reconstructions.
• Relative contraindications for the
anterior approach are age, morbid
obesity, previous intraabdominal or
retroperitoneal surgery, history of severe
pelvic inflammatory disease, and
previous anterior spinal surgery.
FIGURE 35-2
I N D I CAT I O NS
C O N T RO V E R S IE S
• Diagnosis of diskogenic syndrome by
diskography is considered controversial
by some authors.
• The upper limits of disk height loss for
arthroplasty are not clearly defined.
T R E A T M E N T OP T I O N S
• Continued conservative treatment with
medications, physical therapy, and
injections
• Fusion of the involved segment—
various techniques
• Artificial disk replacement at the
involved level
FIGURE 35-3
n
Use T2 weighted-sagittal magnetic resonance imaging (MRI) to document disk
degeneration (Figure 35-2).
n
Use axial MRI images to assess significant facet joint degeneration, which would
be a contraindication for arthroplasty.
n
Perform preoperative DEXA scan to verify adequate bone density (T-score greater
than −1.0) before the procedure.
n
Figure 35-3 is a computed tomography (CT) diskogram showing morphologic
changes at L5-S1; the patient reported 10/10 concordant pain. The L4-5 level
was normal with minimal discomfort.