Добавил:
Sekretar
kiopkiopkiop18@yandex.ru
t.me/Prokururor I Вовсе не секретарь, но почту проверяю
Опубликованный материал нарушает ваши авторские права? Сообщите нам.
Вуз:
Предмет:
Файл:Ординатура / Хирургия / Библиотека им академика М.И. Перельмана / Книга_6031_Библиотеки_им_академика_М_И_Перельмана.pdf
24 Role of Neuromonitoring in Minimally Invasive Lateral Approaches to the Spine
Fig. 24.4 Patient in the
lateral decubitus position
with the table broken
237
electromyography (EMG). Each of these modalities has been proposed to play an important role
at specifi c stages of surgery. During spinal surgery, it has been suggested that neurophysiological testing helps to avoid unforeseen neuronal
or vascular injury, reduces the risk of a permanent postoperative defi cit, and provides localization of specifi c nerve roots. SSEPs comprise
signals recorded from multiple positions along
the afferent pathway of primarily proprioceptive tracts. These are transmitted via the dorsal
columns of the spinal cord. As mentioned above,
when patients are positioned laterally, SSEPs
can be particularly useful in possibly identifying
and reversing impending damage to peripheral
nerves within both upper and lower extremities
(by repositioning the extremity of concern) [ 9 ].
A peripheral disturbance in neuronal transmission may be resultant of stretch or compression
in any of the extremities in this lateral position.
As an example, the peripheral nerve(s) in the top
arm, primarily at the site of the brachial plexus,
can be stretched if proper padding techniques
are not administered. The bottom arm can also
experience similar strain as nerve(s) can be compressed if the head is not positioned properly in
a neutral fashion and/or an axillary roll is inappropriately placed. Furthermore, compression of
the ulnar nerve can occur in either of the arms
if they are not adequately padded. The break in
the surgical table can cause the bottom leg to be
compressed or the top leg to be stretched past its
functional threshold. It is of utmost importance
for the neuromonitoring team to have reliable
peripheral SSEP responses (recorded from Erb’s
point in the upper extremities and the popliteal
fossa in the lower extremities) to distinguish
between changes caused by positioning, surgical
manipulation, pharmacological events, or underlying physiological issues.
MEPs are elicited by transcranial activation of
the motor cortex and are transmitted through the
lateral corticospinal tracts of the cord, exiting at
each nerve root level, continuing transmission of
the signal to the motor axons that innervate each
of the designated muscles. MEPs have been proposed to be a very sensitive test for assessment of
motor function and may allow for more rapid
identifi cation of potential damage to neural structures. Although further study is needed, some
practitioners feel that effective MEP methods and
techniques can give additional prognostic information for the assessment of patient outcomes.
From a technical perspective, EMG electrodes
are placed in the muscles that supply the nerve(s)
that may be at risk during a given procedure.
For the lateral approach, these muscles include
the iliopsoas, vastus lateralis, biceps femoris,
238
Iliopsoas
Vastus lateralis
K.D. Than et al.
Biceps femoris
Tibialis anterior
Abductor hallucus
Fig. 24.5 Diagram for placement of EMG leads for lateral approaches to the spine
tibialis anterior, gastrocnemius, and abductor
hallucis muscles (Fig. 24.5 ). Depending upon the
neuromonitoring group’s protocol, the electrodes
used to monitor MEP responses may be suffi cient
to also monitor the EMG. However, in general,
more extensive coverage of muscles is applied
to EMG monitoring than is to MEP monitoring.
It should be noted that any electrodes used to
monitor EMG can theoretically be used to record
MEP responses as well; two additional cortical
stimulating electrodes are placed to add MEPs
as a modality when requested. Both SSEP and
EMG monitoring are limited in the information
each can give the surgical and neuromonitoring
teams (such as an ischemic event at an individual
root level). Thus, MEPs may provide the surgeon with more data that can assist with surgical
decision-making.
For the minimally invasive lateral transpsoas
approach, the most common and benefi cial neuromonitoring technique is EMG. EMG can provide real-time feedback, allow for surgical
correspondence with specifi c nerve roots, and
safely guide retractors. There are two forms of
EMG: (1) free-running, which assesses continuously for evidence of nerve root manipulation,
and (2) triggered, where nerves are intentionally
stimulated to elicit a response (Figs. 24.6 and
24.7 ). EMG has high sensitivity but low specifi c-
ity in predicting postoperative neurologic defi cits
and thus is frequently used in combination with
other forms of neuromonitoring [ 10 , 11 ].
The use of EMG is essential during the minimally invasive lateral transpsoas approach. In
a literature review, Uribe et al. [ 12 ] concluded
that the use of EMG during lateral approaches
has decreased the incidence of neurologic defi cit from 30 % to less than 1 % [ 13 – 16 ]. In this
review, the authors describe a method by which
the femoral nerve can be reliably positioned posterior to the retractor, thus minimizing the risk
of injury by retraction. By rotating the directional EMG probe, ideal positioning relative to
the femoral nerve can be confi rmed by observing
high stimulation thresholds anteriorly and low
stimulation thresholds posteriorly. (Stimulation
Gastrocnemius
24 Role of Neuromonitoring in Minimally Invasive Lateral Approaches to the Spine
239
thresholds refer to the amount of current required
to activate a nerve. Low thresholds indicate close
proximity to nerve, whereas high thresholds indicate further distance from it.)
Fig. 24.6 Nerve stimulators
are used to assess for nearby
nerves prior to expansion of
the tubular retractor
In a prospective, multicenter, industrysponsored trial, Tohmeh et al. [ 17 ] enrolled
102 patients undergoing extreme lateral interbody fusion (XLIF) at L3–L4 and/or L4–L5 to
a
Fig. 24.7 ( a ) Panel A shows baseline SSEP record-
ings during a lateral transpsoas interbody fusion. Panel
B shows baseline EMG. ( b ) Panel A shows stable SSEP
recordings. Panel B shows a triggered EMG of the left
iliopsoas, vastus lateralis, and biceps femoris at 2 mA.
( c ) Enlarged picture of triggered EMG
240
K.D. Than et al.
b
c
Fig. 24.7 (continued)
receive intraoperative real-time EMG recordings.
Recordings were taken using three successive
dilators at three points: surface of the psoas muscle, middle of the psoas muscle, and on the spine
itself. Recordings were made at four points (posterior, superior, anterior, and inferior) in a 360°
rotational fi eld. Zones III and IV were targeted
in the vast majority (90 %) of cases. The authors
found that lumbar plexus nerves were encountered in 55.7 % of all cases and, more commonly,
posteriorly 63 %. The feedback provided by EMG
allowed the authors to adjust their surgical trajectory. Postoperatively, transient hip fl exion weakness occurred in 27.5 % of patients, and transient
upper medial thigh sensory loss occurred in
17.6 %. Three other motor defi cits (two patients
24 Role of Neuromonitoring in Minimally Invasive Lateral Approaches to the Spine
241
with knee extension weakness and one patient
with ankle dorsifl exion weakness) were encountered, but all had resolved by 6 months postoperatively. Given the variable location of the nerves
and the good long-term outcomes of the patients,
this authors’ study supported the use of real-time
EMG during the minimally invasive lateral transpsoas approach.
One emerging neuromonitoring modality that
has recently entered the fi eld for use in this and
other spine surgeries is mechanomyography
(MMG). One potential drawback of EMG is its
susceptibility to electrical interference, which
can result in a poor signal-to-noise ratio and,
hence, the aforementioned low specifi city. Using
MMG, electrically stimulated probes induce
nerve root depolarization. Special sensors (accelerometers that are not susceptible to electrical
interference) are placed on correlating muscle
groups and detect the mechanical activity (movement) of muscle contraction after nerve stimulation. This feedback is delivered in real time to the
surgeon in a fashion similar to EMG activity.
Application of this modality to spine surgery is
still under development and, to date, no published
studies exist that examine its practicality or effi cacy. Preliminary results, however, suggest that
MMG has faster detection and higher sensitivity
than EMG [ 18 ].
24.4 Outcomes in Lateral Spine
Surgery
The most worrisome complication after any spine
surgery is postoperative motor defi cits. In a prospective, non-randomized, multicenter, industrysponsored trial, Isaacs et al. [ 19 ] performed XLIF
on 107 patients (322 levels) with degenerative
scoliosis. Thirty-six patients (33.6 %) had some
evidence of postoperative weakness, with 80.6 %
of such patients suffering from hip fl exion weakness. This was transient in the vast majority of
cases (86.2 %). Seven patients (6.5 %) were considered to have a “major” motor defi cit, defi ned
as a postoperative decrease in motor grade by
more than two grades at any point and/or having
no evidence for improvement by 6 months. Only
one patient was considered to have an injury of
lumbar plexus origin, although further detail
was not provided by the authors. The authors
did conclude that the risk of experiencing any
complication was lower in patients who received
stand-alone XLIF compared to supplemental posterior instrumentation; in those who did receive
posterior instrumentation, the complication rate
was lower in those who had percutaneous screw
placement compared to open screw placement.
According to this study, “(the) strongest independent predictor of complications was the total
number of levels operated per patient.” Of note,
several important long-term outcome measures
were not included in this study, including postoperative sagittal vertical axis measurements and
fusion and pseudarthrosis rates.
Cahill et al. [ 20 ] retrospectively reviewed 118
patients who had undergone minimally invasive
lateral transpsoas interbody fusion at 201 levels,
all with continuous EMG monitoring. Ipsilateral
nerve injury (specifi cally of the femoral nerve)
occurred in two patients, both at the L4 and L5
levels. This equated to a 4.8 % risk of injury at
L4–L5 compared to no neurologic complications
at any other level. Echoing the aforementioned
conclusions of Guerin et al. [ 5 ], these authors
also recommended “judicious” use of this surgical procedure at L4–L5. In another study [ 21 ],
two out of 58 patients suffered iatrogenic femoral
nerve injury, although the specifi c vertebral levels instrumented were not specifi ed. Rarely, contralateral femoral nerve injury can occur. Two
such cases have been reported secondary to interbody placement: one due to an osteophyte fracture compressing the contralateral nerve root and
another due to a far lateral disc herniation with
the same result [ 22 ]. Both patients recovered
after reoperation for decompression of the injured
nerve root.
In the aforementioned Cahill et al. study [ 20 ],
fi ve patients (4.2 %) suffered from postoperative
abdominal paresis/fl ank bulge, presumably secondary to injury to the T11 and T12 motor nerves
during exposure and closure of the abdominal
wall. All fi ve cases occurred at the L3–L4 level
or higher. A larger multi-institutional study
of 568 patients found 10 who developed this
242
K.D. Than et al.
complication (1.8 %) [ 23 ]. Eight of these patients
had resolution of their abdominal wall paresis
within 6 months, whereas the other two were
lost to follow- up. Conservative treatment of this
complication consists of wearing an abdominal
corset. To avoid the complication, the authors
suggested sequential and gentle muscle dilation
with blunt instruments, dissection, and mobilization of any encountered nerves and, in the retroperitoneal space, blunt dissection in a posterior to
anterior and superior to inferior trajectory so as to
“run with” the trajectory of the nerves.
While motor defi cits impact a patient’s functionality, sensory changes can also be very bothersome. In a retrospective review of 59 patients
who underwent the minimally invasive lateral
transpsoas approach, Cummock et al. [ 24 ] found
that approximately 60 % of patients suffered
from postoperative thigh pain, numbness, and/or
paresthesias. Half of the patients had resolution
of these symptoms at 3 months postoperatively,
while 90 % had resolution by 1 year.
The lack of signal changes during intraoperative neuromonitoring does not guarantee that a
patient will have normal neurologic function
postoperatively. Houten et al. [ 25 ] reported two
cases of postoperative neurologic defi cit (one
patient with profound quadriceps weakness and
another with antigravity hip fl exor and quadriceps weakness) despite normal intraoperative
monitoring.
24.5 Recommendations
In summary, while the minimally invasive lateral
transpsoas approach is being used increasingly in
spine surgery, it can be fraught with complications (specifi cally, injury to the lumbar plexus).
There are a few strategies to employ when utilizing this surgical approach. First, the surgeon
must have a good understanding of the safe
working zones at each lumbar level. This is simple enough, as the safest zone is Zone III at L1–
L2, L2–L3, and L3–L4. At L4–L5, Zone II is the
safest, but there should be a low threshold to
abort the procedure at this level due to the
relatively high risk of neurologic complication.
Second, neuromonitoring with EMG should
always be used, and trajectories should be
adjusted if there is any evidence for fi ring on
EMG. The role of MEP and SSEP monitoring is
less clear, although SSEP monitoring may be of
benefi t to minimize positioning-related brachial
plexus injuries.
References
1. McAfee PC, et al. Minimally invasive anterior retroperitoneal approach to the lumbar spine. Emphasis on
the lateral BAK. Spine (Phila Pa 1976). 1998;23(13):
1476–84.
2. Laws CJ, et al. Direct lateral approach to lumbar
fusion is a biomechanically equivalent alternative to
the anterior approach: an in vitro study. Spine (Phila
Pa 1976). 2012; 37(10):819–25.
3. Benglis DM, Vanni S, Levi AD. An anatomical study
of the lumbosacral plexus as related to the minimally
invasive transpsoas approach to the lumbar spine.
J Neurosurg Spine. 2009;10(2):139–44.
4. Uribe JS, et al. Defi ning the safe working zones using
the minimally invasive lateral retroperitoneal transpsoas approach: an anatomical study. J Neurosurg
Spine. 2010;13(2):260–6.
5. Guerin P, et al. The lumbosacral plexus: anatomic
considerations for minimally invasive retroperitoneal
transpsoas approach. Surg Radiol Anat. 2012;34(2):
151–7.
6. Moro T, et al. An anatomic study of the lumbar plexus
with respect to retroperitoneal endoscopic surgery.
Spine (Phila Pa 1976). 2003;28(5):423–8; discussion
427–8.
7. Dakwar E, Vale FL, Uribe JS. Trajectory of the main
sensory and motor branches of the lumbar plexus outside the psoas muscle related to the lateral retroperitoneal transpsoas approach. J Neurosurg Spine. 2011;
14(2):290–5.
8. Fahim DK, et al. Avoiding abdominal fl ank bulge
after anterolateral approaches to the thoracolumbar
spine: cadaveric study and electrophysiological investigation. J Neurosurg Spine. 2011;15(5):532–40.
9. Kamel IR, et al. The use of somatosensory evoked
potentials to determine the relationship between
patient positioning and impending upper extremity
nerve injury during spine surgery: a retrospective
analysis. Anesth Analg. 2006;102(5):1538–42.
10. Paradiso G, et al. Multi-modality neurophysiological
monitoring during surgery for adult tethered cord syndrome. J Clin Neurosci. 2005;12(8):934–6.
11. Paradiso G, et al. Multimodality intraoperative neurophysiologic monitoring fi ndings during surgery for
24 Role of Neuromonitoring in Minimally Invasive Lateral Approaches to the Spine
243
adult tethered cord syndrome: analysis of a series of
44 patients with long-term follow-up. Spine (Phila Pa
1976). 2006;31(18):2095–102.
12. Uribe JS, Vale FL, Dakwar E. Electromyographic
monitoring and its anatomical implications in minimally invasive spine surgery. Spine (Phila Pa 1976).
2010;35(Suppl 26):S368–74.
13. Rodgers WB, Gerber EJ, Patterson J. Intraoperative
and early postoperative complications in extreme lateral interbody fusion: an analysis of 600 cases. Spine
(Phila Pa 1976). 2011;36(1):26–32.
14. Wang MY, Mummaneni PV. Minimally invasive surgery for thoracolumbar spinal deformity: initial clinical experience with clinical and radiographic
outcomes. Neurosurg Focus. 2010;28(3):E9.
15. Tormenti MJ, et al. Complications and radiographic
correction in adult scoliosis following combined
transpsoas extreme lateral interbody fusion and posterior pedicle screw instrumentation. Neurosurg Focus.
2010;28(3):E7.
16. Bergey DL, et al. Endoscopic lateral transpsoas
approach to the lumbar spine. Spine (Phila Pa 1976).
2004;29(15):1681–8.
17. Tohmeh AG, Rodgers WB, Peterson MD. Dynamically
evoked, discrete-threshold electromyography in the
extreme lateral interbody fusion approach. J Neurosurg Spine. 2011;14(1):31–7.
18. Jogani J, Wybo C, Bartol S. Innovation in spine surgery: miracles of MMG. International society for the
advancement of spine surgery. 2011. SAS11.
19. Isaacs RE, et al. A prospective, nonrandomized, multicenter evaluation of extreme lateral interbody fusion
for the treatment of adult degenerative scoliosis: perioperative outcomes and complications. Spine (Phila
Pa 1976). 2010;35(Suppl 26):S322–30.
20. Cahill KS, et al. Motor nerve injuries following the
minimally invasive lateral transpsoas approach.
J Neurosurg Spine. 2012;17:227–31.
21. Knight RQ, et al. Direct lateral lumbar interbody
fusion for degenerative conditions: early complication
profi le. J Spinal Disord Tech. 2009;22(1):34–7.
22. Papanastassiou ID, Eleraky M, Vrionis FD. Contralateral
femoral nerve compression: an unrecognized complication after extreme lateral interbody fusion (XLIF). J
Clin Neurosci. 2011;18(1):149–51.
23. Dakwar E, et al. Abdominal wall paresis as a complication of minimally invasive lateral transpsoas interbody fusion. Neurosurg Focus. 2011;31(4):E18.
24. Cummock MD, et al. An analysis of postoperative thigh
symptoms after minimally invasive transpsoas lumbar
interbody fusion. J Neurosurg Spine. 2011;15(1):11–8.
25. Houten JK, et al. Nerve injury during the transpsoas
approach for lumbar fusion. J Neurosurg Spine. 2011;
15(3):280–4.
Lateral Interbody Decompression and Fusion: Which Side to Approach From?
Andrew A. Sama
2 5
25.1 Background
Bertagnoli et al. initially described lateral lumbar
interbody surgery in 2003 when they described the
approach to implant prosthetic nuclear devices into
the lumbar spine [ 1 ]. Ozgur and Pimenta described
the extreme lateral transpsoas approach for interbody fusion in 2006 [ 2 ]. Over the last 7 years, the
popularity and applications for minimally invasive
lateral retroperitoneal approaches to the lumbar
spine have grown. As the indications and applications have broadened, so have the dilemmas regarding which side to approach. In cases of a one-level
fusion for degenerative disc disease, the point may
be moot, and the approach should be based on
which side appears easier to access on x-ray with
respect to the ribs or iliac crest or whether the
patient had prior retroperitoneal surgery on one side
or the other. In more complex cases with coronal
and sagittal deformities, the side of the approach
becomes more poignant.
25.2 Anterior Interbody Versus Posterior Interbody
The fi rst thing to decide is whether an anterior
or posterior interbody approach is warranted and
advisable. It has been demonstrated that both
A. A. Sama , M.D.
Department of Orthopaedic Surgery,
Weill Cornell Medical College , 523 East 72 Street ,
New York , NY 10021 , USA
e-mail: samaa@hss.edu
traditional posterior and anterior approaches to
the spine are associated with a variety of potential benefi ts and complications [
decision to approach anteriorly has been made,
then consideration for anterior retroperitoneal
transpsoas or anterior-to-the-psoas approaches
can be considered. Approaching from the anterior lateral aspect of the spine allows powerful
correction of the spine in both the coronal and
sagittal planes [ 6 ]. It also allows placement of
a large interbody spacer with large graft chambers to facilitate fusion. By restoring collapsed
disc space height, indirect decompression of the
neuroforamina and subarticular lateral recesses
can be achieved [ 7 ]. Careful evaluation of the
facet joints at the proposed fusion sites on preoperative CT scan or MRI is imperative to estimate
how much distraction and elevation of the disc
space will be possible from the lateral approach.
If the facets are ankylosed, it is not likely that
the surgeon will be able to correct the collapsed
disc space or the deformity anteriorly alone.
In these cases, a posterior approach for release
of the facets and correction of the deformity is
advisable prior to any interbody work. If the facets are not ankylosed and an anterior, lateral, or
transpsoas approach is contemplated, the surgeon
must decide on whether to perform a traditional
anterior approach, a direct transpsoas approach,
or an anterior-to-the-psoas lateral approach. In
cases with severe loss of lumbar lordosis, or in
the presence of lumbar kyphosis, release of the
anterior longitudinal ligament may be necessary
for optimal correction. Release of the anterior
3 – 5 ]. Once the
M.Y. Wang et al. (eds.), Minimally Invasive Spinal Deformity Surgery,
DOI 10.1007/978-3-7091-1407-0_25, © Springer-Verlag Wien 2014
245
246
A.A. Sama
longitudinal ligament from the transpsoas
approach is possible [ 8 , 9 ] but typically ill advised
because of the potential increased risk of injury
to the great vessels and diffi culty in controlling a
bleed if an injury were to occur. The lateral interbody approach also temporarily depends on the
integrity of the anterior and posterior longitudinal ligaments to help keep the spacer in place.
If the anterior longitudinal ligament is released
or ruptured, provisional fi xation of the interbody
spacer should be considered. Mobilization of the
vessels via a traditional anterior approach or even
from an anterior-to-the-psoas lateral approach
allows for safer access to release the anterior longitudinal ligament and correct the severe sagittal
deformity than posterior or transforaminal interbody approaches.
25.3 Approaching from the Concave or Convex Side of the Spine
Several factors should come into consideration when determining the side of the lateral
approach, especially in deformity cases. Things
to consider include the approach that would allow
the best access to the greatest number of levels
in order to achieve correction of the deformity.
A general rule of thumb is to allow the alignment
and approachability of the L4–5 disc to be the
guide if it is to be included in the fusion. A good
set of lumbar or scoliosis x-rays in the anteriorposterior and lateral planes are usually adequate
to begin planning the approach (Fig. 25.1 ).
The fi lms should be analyzed to determine if the
patient has scoliosis or spondylolisthesis in the
anterior- posterior or lateral planes. Depending
on the presence of one or more of these deformities, the approach that gives access to the L4–5
disc is usually preferred. Once the analysis of the
scoliosis or lumbar x-rays has been completed
and the surgeon has decided on the provisional
approach, careful evaluation of the preoperative
MRI (Fig. 25.2 ) should be undertaken to assess
the position of the psoas muscle, the lumbar
plexus, and the great vessels with respect to the
fusion levels under consideration [ 10 – 13 ].
25.4 Concave Approach
Fortunately, approaching from the side that
allows access to the L4–5 disc obliquity is usually
approaching from the concavity of a lumbar scoliosis (Fig. 25.3 ). When approaching from the
concavity, the surgeon is able to access multiple
levels from one well-placed incision as depicted
in Fig. 25.3 . Once the decision to approach from
the concavity has been made, the surgeon should
consider addressing the cephalad or most caudal
levels fi rst rather than addressing the apical levels
fi rst which will correct the deformity and likely
make access to the higher or lower levels more
diffi cult because they will be further displaced
upward under the ribs or lower into the pelvis,
respectively. Angled instrumentation to access
and prepare the disc spaces is now available from
most manufacturers. These angled cob elevators,
pituitary rongeurs, and curettes allow the surgeon
to access, prepare, and release the disc while preserving the end plates.
By addressing the curvature from the concavity, a signifi cant amount of correction can be
achieved in the coronal and sagittal plane deformities. Releasing the annulus of each disc and distracting the more collapsed side of the disc allow
for the most signifi cant correction. Approaching
from the concavity also allows approach to the
upper lumbar levels with less likelihood of entering the chest (Fig. 25.4 ). The operating table
can be used to help correct the deformity when
approaching from the concave side of the curve
by fl exing the break in the table (Fig. 25.5 ).
Care must be taken when approaching from
the concave side to avoid excessive bony destruction. This is especially true in patients with large
bridging osteophytes on the concavity of the
curve. Using an osteotome to enter the disc space
under fl uoroscopic guidance in the anteriorposterior view from the concavity of the curve
can help minimize bony destruction (Fig. 25.8 ).
The position of the segmental vessels must also
be considered with a concave-sided approach
[ 14 , 15 ]. The segmental arteries can be bunched
together and may be prone to injury when removing concave osteophytes. Again, using the fl uoroscopic guidance to be sure the trajectory of the
25 Lateral Interbody Decompression and Fusion: Which Side to Approach From?
247
Good position for
potential mini-open
incision
Would be
difficult to
access L4-5
L4-5 easily
accessible
over the iliac
crest
Fig. 25.1 Standing Anteriorposterior and Lateral Scoliosis x-rays showing coronal and sagittal decompensation
Note position of vessels
that would make ALIF more
difficult
Nerve roots exiting spine
and entering lumbar
plexus with psoas
bilaterally
Fig. 25.2 Axial T2 Weighted slice through lumbar segment to illustrate position of the psoas
Potential trajectory
for lateral inter-body
fusion