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Файл:Ординатура / Хирургия / Библиотека им академика М.И. Перельмана / Книга_6031_Библиотеки_им_академика_М_И_Перельмана.pdf
110
B. Meyer et al.
evolving fi eld, with advances in techniques, technology, and instrumentation occurring regularly.
During preoperative planning, several key
interdependent features must be assessed, which
will determine the degree of diffi culty to be
expected during any rod maneuver:
1. Length of the construct
2. Severity of coronal and sagittal deformity
3. Desired/necessary degree of reduction
4. The number of distinct curves the rod must
traverse
5. Any complicated connections, such as with
iliosacral screws
These elements exist in concert with comprehensive classifi cations that may trigger differential treatment [ 7 ].
1 . Length of construct : Since almost all cases are
Schwab type V or IV with a preponderance of the
former [ 8 ], the vast majority of constructs can be
considered as short (up to L2) or intermediate (up
to T10). They will thus comprise (depending on
the inclusion of S1) either 4 or less segments in
the former group or up to 8 in the latter.
2 . Severity of deformity : Coronal Cobb angles
>30° as well as subluxations > 6 mm will
increase the diffi culty. Any major sagittal imbal-
ance [ 9 , 10 ], which is a major limiting factor in
MIS corrections, also complicates the correc-
tion. If the construct is considered and requires
extension to the construct to the upper thoracic
area, then two curves must typically be tra-
versed (thoracolumbar and lumbosacral) [ 10 ].
3 . Degree of correction : The degree of sagittal
correction can be critical to optimal outcomes.
If the sagittal vertical axis (SVA) exceeds
10 cm, osteotomies will be needed for correc-
tion. This also limits the ability of the surgeon
to pass a single rod, as it is not possible to pass
a lordotic rod into a severely kyphotic spine.
Thus a two-rod technique may have to be uti-
lized. Non-kyphotic deformities can often be
corrected through appropriate contouring with
anterior releases [ 11 , 12 ]. Coronal deformities
even below 30° cannot be properly corrected
with derotation techniques alone [ 13 , 14 ] given
the stiffness of the spine. In these cases appro-
priate anterior or intersomatic releases may be
necessary using multiple MIS TLIFs or antero-
lateral approaches. Curves greater than 30°
should be preferentially reduced below this
limit by anterior asymmetric release and intersomatic fusion. A reduction of the remaining
curve is then possible by derotation.
4 . The number of distinct curves the rod must
traverse : Passing a rod through both the thoracolumbar and lumbosacral junctions requires
the rod to be in an “S” shape to have the proper
fi nal contour. Thus, it may not be possible to
access all the screw saddles appropriately
without a small opening in the muscle fascia.
5 . Any complicated connections, such as with
iliosacral screws : Since the iliac screw heads
will be offset laterally and dorsally to pedicle
screws, proper screw entry site planning is
critical. Starting the sacral screws in a more
cranial position and leaving them 3–6 mm
proud, along with starting the iliac screws
caudally and more ventrally, can improve the
ease of connections. However, it is also often
necessary to place a small lateral bend in the
caudal aspect of the rods as well.
The following steps would be performed in a
long-segment MIS deformity surgery:
– Once all screws and screw extenders are in
place and lined up with the aid of the markers
and lateral fl uoroscopy, the rod measurement
tool is placed on the skin next to the extenders
after being bent to be in contact with the skin
over the complete length.
– A rod of the corresponding length is fi rmly
attached to the steerable rod inserter before
any contouring. Compensation for any curvature is critical. The rod is then bent in the
appropriate planes to achieve the desired
degree of deformity correction.
– Starting on the concave side, the most cephalad
extender is held perpendicular to the skin, and the
rod entry point estimator is attached to mark the
place for the stab incision. Rods are often inserted
in a cranio-caudal direction for safety reasons.
Laminar shingling minimizes the risk of unintentional rod passage into the spinal canal.
– The passage of the rod is controlled by lateral
fl uoroscopy to ensure that it remains below
the muscle fascia. Movements should be
smooth without excessive force. Once the rod
is in the fi rst window, this can be controlled
with a rod confi rmation tool brought into the
13 Rod Contouring, Passage, and Connection
ab c
de f
Fig. 13.1 Rod passage with rotation of the rod along its long axis to drive the rod laterally or medially to engage all
the screw heads in a deformed spine. This requires a bend at the leading portion of the rod
111
extender shaft or by slightly twisting the
extender. This is repeated for every screw.
– The complete passage requires twisting move-
ments of the inserter up to 90° to both sides
along the long axis of the rod to “steer it medi-
ally or laterally ” (Fig. 13.1 ). A combination of
tactile feedback and fl uoroscopic control is used.
– From the center to periphery, the extenders are
then reduced in a stepwise fashion with the aid
of the reduction nuts, which are facilitated by
the markers visible on the extender ends.
Usually three rounds are needed until com-
plete reduction to allow successive correction
to avoid screw pullout.
– The contralateral rod is inserted after the nec-
essary pre-contouring. The inserter is detached
after all set screws are tight and fi nal imaging
control, has been performed.
References
1. Ringel F, Stoffel M, Stüer C, Meyer B. Percutaneous
transmuscular pedicle screw fi xation of the thoracic
and lumbar spine. Neurosurgery. 2006;59(ONS Suppl
4):361–7.
2. Foley KT, Gupta SK. Percutaneous pedicle screw fi xation of the lumbar spine: preliminary clinical results.
J Neurosurg. 2002;97 Suppl 1:7–12.
3. Wang MY, Anderson DG, Poelstra KA, Ludwig SC.
Minimally invasive posterior fi xation. Neurosurgery.
2008;63 Suppl 3:197–203.
4. 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(7): 459–67.
5. 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.
6. Scheufl er KM, Cyron D, Dohmen H, Eckardt A. Less
invasive surgical correction of adult degenerative
scoliosis, part I: technique and radiographic results.
Neurosurgery. 2010;67(3):696–710.
7. Silva FE, Lenke LG. Adult degenerative scoliosis: evaluation and management. Neurosurg Focus. 2010;28(3):E1.
8. Schwab F, Farcy JP, Bridwell K, et al. A clinical
impact classifi cation of scoliosis in the adult. Spine
(Phila Pa 1976). 2006;31(18):2109–14.
9. Villard J, Ringel F, Meyer B. Sagittal balance: a useful
tool for neurosurgeons. Adv Tech Stand Neurosurg.
2012 (in press).
10. Le Huec JC, Charosky S, Barrey C, Rigal J, Aunoble S.
Sagittal imbalance cascade for simple degenerative spine
and consequences: algorithm of decision for appropriate treatment. Eur Spine J. 2011;20 Suppl 5:699–703.
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11. Acosta F, Liu J, Slimack N, Moller D, Fessler R, Koski T.
Changes in coronal and sagittal plane alignment following minimally invasive direct lateral interbody fusion for
the treatment of degenerative lumbar disease in adults: a
radiographic study. J Neurosurg. 2011;15:92–6.
12. Khoo LT, Palmer S, Laich DT, Fessler RG. Minimally
invasive percutaneous posterior lumbar interbody
fusion. Neurosurgery. 2002;51:S166–81.
13. Cheng JS, Lebow RL, Schmidt MH, Spooner J. Rod
derotation techniques for thoracolumbar spinal deformity. Neurosurgery. 2008;63 Suppl 3:149–56.
14. Lee SM, Suk SI, Chung E-R. Direct vertebral rotation:
a new technique of three dimensional deformity correction with segmental pedicle screw fi xation in adolescent idiopathic scoliosis. Spine. 2004;29(3):
343–9.
Percutaneous Sacropelvic Fixation
Michael Y. Wang
1 4
14.1 Introduction
Lumbopelvic fi xation has increasingly become
an important adjunct for stabilization of the lumbosacral spine. The ability to place larger diameter and longer screws anterior to the center of
gravity of the body promotes stability both
regionally and globally and can also reduce the
likelihood of a pseudarthrosis or hardware construct failure [ 20 ]. For these reasons, the use of
iliac screws and bolts has become popular since
the original descriptions of the precursors to
these methods by Allen and Ferguson [ 1 ].
Current indications for iliac screw fi xation
include situations where substantial biomechanical stabilization is required in the lumbosacral
spine. This includes settings with long constructs,
spinal deformity, severe osteoporosis, a previous
failed fusion, or severe instability due to trauma,
tumor, or infection [ 3 , 6 , 7 , 10 ]. In addition, iliac
fi xation is useful in cases where no other feasible
caudal fi xation points are available, such as for
revision fusion surgery. Because the human pelvis contains a signifi cant cancellous bone space
bordered by inner and outer cortical walls, screws
or bolts of a substantial diameter and length can
be placed safely for fi xation. This allows the
M. Y. Wang , M.D., FACS
Departments of Neurological Surgery &
Rehab Medicine , University of Miami Miller
School of Medicine , 1095 NW 14th Terrace,
Lois Pope Life Center, D4-6 , Miami , FL 33136 , USA
e-mail: mwang2@med.miami.edu
placement of screws between 65 and 120 mm in
length and 7.0–10.0 mm in diameter [ 16 ].
While the placement of iliac screws has
become widely accepted, there remain several
methods for ensuring proper hardware placement. Manual digital palpation of the lateral iliac
wing to the sciatic notch allows the surgeon to
directly determine the screw trajectory and bony
confi nes manually. More recently indirect palpation of the inner cortical walls of the pelvis using
a curved pedicle fi nder has been advocated, minimizing the need for soft tissue disruption. In
either case extensive muscular dissection over
the posterior superior iliac spine is needed to
expose the screw entry points.
Pain secondary to iliac screw placement may
be due to several causes, including hardware
prominence, disruption of the sacroiliac joint,
and screw loosening [ 4 ]. However, local soft tis-
sue destruction and muscular devitalization for
surgical exposure may play a role as well. For
these reasons, we have sought to develop a
method for the minimally invasive placement of
iliac screws.
Percutaneous pedicle screw fi xation techniques
have now become widely accepted as an option for
lumbosacral fi xation [ 2 , 5 , 8 , 9 , 11 – 14 , 17 ]. The
general principle of percutaneous pedicle screw
instrumentation has been fl uoroscopically guided
K-wire placement followed by screw tract preparation and hardware placement using cannulated
instruments and implants. The use of screw extensions then allows the surgeon to control the implant
and secure and connect it to the adjacent levels.
M.Y. Wang et al. (eds.), Minimally Invasive Spinal Deformity Surgery,
DOI 10.1007/978-3-7091-1407-0_14, © Springer-Verlag Wien 2014
113
114
M.Y. Wang
We have sought to extend these methods for application in sacropelvic fi xation and initially
described the technique in a case report [ 19 ]. We
have since expanded the application of this method
report here our preliminary results with imagebased percutaneous iliac screw placement.
14.2 Surgical Technique for Image-Based Iliac Targeting
X-ray imaging is used to visualize the body of the
ischium by angling the fl uoroscope in a steep
Ferguson view in the sagittal plane and in the
plane of the ilium in the coronal plane. This
“obturator outlet view” allowed for visualization
of the inner and outer tables as well as the “teardrop” confi guration of the ischial body (Figs. 14.1
and 14.2 ). This teardrop shape is the overlapping
of the two-dimensional projection of the inner
and outer tables of the ilium from medially to laterally [ 15 ]. Thus, targeting this region insures
proper screw placement.
The screw entry site is located just ventral to
the posterior superior iliac spine (PSIS). A drill
or small osteotome is used to remove the cortical bone so that the screw head may be recessed
to minimize hardware prominence. This entry
site into the cancellous bone also minimizes the
risk of inadvertent entry into the sacroiliac
joint. A Jamshidi needle is then advanced to a
depth of 80 mm under fl uoroscopic guidance to
keep the tip of the needle within the teardrop.
This is followed by K-wire exchange and placement of a cannulated awl, tap, and instrumentation with Viper™ titanium alloy percutaneous
iliac screws (Depuy Spine, Inc, Raynham,
Massachusetts).
Hardware connections were made between
screws and rods with the assistance of screw
extensions. Subfascial rod passage was performed in a cranial to caudal direction by
inserting the rod through the most cranial
screw’s incision. This allowed for precise control of the length of rod passed beyond the
iliac screw saddle distally in an effort to minimize hardware prominence. In several cases
two-plane rod bending was necessary to place
the distal rod laterally to meet the iliac screw
head.
a
bc
d
Fig. 14.1 ( a – c ) Artist’s depiction of a technique for min-
imally invasive sacroiliac screw placement. A small skin
and muscle opening is placed medial to the PSIS to allow
entry into the cancellous bone. Cannulation then occurs
under fl uoroscopic guidance. ( d ) Percutaneous cannulated
iliac screws measuring 8 mm in diameter and 65 mm long
14 Percutaneous Sacropelvic Fixation
a b
115
Fig. 14.2 ( a ) Obturator outlet view with fl uoroscopy
demonstrating the “teardrop” projection as the idealized
endpoint for the screw tip. ( b ) Intraoperative view show
the coronal and sagittal angulation needed to obtain the
14.3 Clinical Applications
We have placed 61 sacropelvic screws using this
technique [ 18 ]. All patients underwent CT scan-
ning with three-dimensional reconstruction to
assess screw placement and were found to have
no bony breaches. This experience has increased
our confi dence that the targeting method innovated by Chapman and colleagues is reliable and
safe. Furthermore, use of the obturator outlet
view does not require special equipment, image
guidance, or other advance technique.
We have applied percutaneous iliac screws in
the settings of spinal infection, trauma, deformity, and neoplasia (Figs. 14.3 , 14.4 , and 14.5 ).
In these settings, its use has been for the same
indications and biomechanical purposes as traditional open sacroiliac fi xation. It should also be
noted that later explantation of screws may also
be necessary given the relatively high rates of
screw loosening with long-term follow-up after
fusion has occurred.
One drawback of the technique may be that
screw explantation is more diffi cult than when
using an offset connector. While we have a limited experience with explantations, it would
require mobilization of the rod from the screw
saddle a suffi cient distance to allow screw
obturator outlet view to allow percutaneous screw placement over a guidewire, with screw extensions to allow for
construct assembly
removal, as opposed to open cases where the offset connector can simply be disengaged.
One of the practical drawbacks of this minimally invasive method involves the diffi culties
associated with connecting complex threedimensional constructs beneath the fascia. For
example, mating S1 pedicle and iliac screws will
often require a lateral offset connector or complex two-plane rod bending given the more lateral and dorsal location of the iliac screw head
(Fig. 14.6 ). We initially avoided this problem by
avoiding connections with an S1 pedicle screw,
thus allowing greater length along the rod to transition dorsally and laterally to the iliac screw
head. However, we recognized that this resulted
in a biomechanically inferior construct when
compared to open surgery. In this series three
patients had concomitant S1 pedicle screws, all
later in the series after we had acquired experience in planning screw placement to allow easier
screw-rod connection (Fig. 14.3 ). In these cases
careful attention must be paid to recessing the
iliac screw saddles and increasing the sagittal
distance between screw heads (i.e., placing the
S1 screws high in the pedicle and starting the
iliac screw in a more caudal position).
Furthermore, keeping the screw heads in line in
the coronal plane will minimize the need for
116
M.Y. Wang
two- plane rod bending. Additional problems
with the minimally invasive approach in these
settings include (1) inadvertent entry into the sacroiliac joint or pelvic cavity with the sharper
Jamshidi needles and (2) diffi culties with creating a recessed location for the screw saddles to
prevent hardware prominence.
Ultimately, the safety of this technique can
only be demonstrated with larger clinical series.
The bony pelvis can vary in thickness and
ab
geometry, and the soft tissues, including neural
and vascular structures, do not conform to a standard or reliable anatomic arrangement. Thus,
minimally invasive iliac screw placement can
prove more diffi cult due to variations in pelvic
anatomy when the traditional landmarks cannot
be directly palpated or visualized. However, the
ability to fi xate the pelvis will likely signifi cantly
expand the spectrum of pathologies that are treatable using a minimally invasive approach.
Fig. 14.3 ( a ) Case of a 46-year-old paraplegic who
developed a sacral decubitus ulcer. This was treated with
a local fl ap, which failed, and he subsequently developed
osteomyelitis at the lumbosacral junction due to exposed
bone. ( b and c ) The patient failed 6 months of intravenous
antibiotic treatment with progression of osteomyelitis and
back pain with deformity and bony destruction as demonstrated on MRI and CT imaging. ( d ) The patient was
treated with an anterior debridement of L4–S1 with iliac
crest autograft reconstruction and ( e ) percutaneous instru-
mentation from L4 to the ilium. ( f ) Proper iliac screw
placement was confi rmed with CT scanning. ( g ) The sur-
gical incisions avoided the infected and affected soft tissues. ( h ) Fixation, debridement, and antibiotic treatment
resulted in resolution of the open wound without need for
another soft tissue fl ap to promote healing
14 Percutaneous Sacropelvic Fixation
117
cd
e
Fig. 14.3 (continued)
118
M.Y. Wang
f
g
h
Fig. 14.3 (continued)
Fig. 14.4 ( a – d ) AP and
lateral imaging of a patient
with lumbar degenerative
scoliosis and positive sagittal
balance which was treated
with minimally invasive
interbody fusion and
percutaneous instrumentation
demonstrating the use of
percutaneous iliac screws in
correction with S1 pedicle
screws. ( e ) CT scanning
demonstrates proper recession
of screw saddles to minimize
hardware prominence
a
14 Percutaneous Sacropelvic Fixation
bc d
119
e
Fig. 14.4 (continued)