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Файл:Ординатура / Хирургия / Библиотека им академика М.И. Перельмана / Книга_6048_Библиотеки_им_академика_М_И_Перельмана.pdf
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The K-wire is then dilated and tapped. Some recommend undertapping (i.e.,
using a tap 1mm smaller than the planned screw diameter). Care should be taken to
ensure that the tap is not advanced over the tip of the K-wire in order to prevent
K-wire pullout. It is once again important to mimic the trajectory of the K-wire as
closely as possible with the tap in order to avoid an unintentional binding and
advancement of the K-wire. The surgeon should be careful not to make a bend in the
wires as this can alter the trajectory and also fracture the K-wire if it is not made of
nitinol. It is best to avoid exposing only a small segment of the wire distal to the
instrument as this increases the likelihood of kinking the wire [1, 8, 9, 17, 18].
The next step is placing the pedicle screw over the K-wire. In general, screw size
is determined using preoperative imaging studies. However, the surgeon may also
determine a new screw size using intraoperative lateral images and knowledge about
the depth of tap insertion. Here, the same trajectory as the K-wire should also be
closely followed. Screw placement is performed in the usual manner according to
the specic instrumentation used. Once the screw is embedded in the vertebral
body, the K-wire can be removed. This may be difcult, and in some cases requires
a little extra force, which can be problematic especially in osteoporotic patients.
Care should be taken to avoid pulling out the screw with the K-wire, and the use of
pliers or vise grip to pull out the K-wire is recommended. A rotational maneuver, in
which the handle of the screw inserter is levered against and the wire is pulled and
bent, can be utilized in order to avoid putting force on the screw itself. Additionally,
the screw can be loosed 2–3mm, which typically loosens the K-wire as well, facili-
tating removal. With this technique, it is important to remember to fully tighten the
screw once the K-wire is removed [5].
Rod Passage Techniques forMultilevel Constructs
Preoperative preparation is vital to safe rod placement, as any disparities between
adjacent screw saddles would hinder rod-screw connection. Additionally, screw
pullout can occur with too great a force placed on the screws during rod attachment.
Thus, care should be taken to ensure proper planning of screw entry points and
attention given to screw head depths in order to circumvent these obstacles. As with
open procedures, it may be necessary to pass the rod multiple times in order to
properly bend the rods for complex or multiplane deformities [5].
Once the percutaneous pedicle screws have been placed as outlined above, the
rod must be passed down to and through the screw heads. In order to do so, before
passage, the rod length must be measured and then contoured before passage.
Currently, smaller size rods are already bent in some degree of lordosis; however,
the rod can be further manipulated as appropriate for the patient. In order to prop-
erly do so, a two-handed technique is preferable. With this technique, the dominant
hand is on the rod holder, while the nondominant hand manipulates the screw exten-
sions. As the dominant hand pushes the rod holder toward the contralateral hand, the
contralateral hand rotates and derotates the screw extensions. This enables accurate
and efcient rod placement in multilevel constructs [2, 5, 17, 19].
B. L. Cohen et al.
217
Using a specialized rod holder with a ratchet for axial rotation, the rod is tun-
neled subfascially via either the top or bottom incision. If rod placement seems
difcult, the rod may inadvertently be driven above the fascia, and thus may be
diverted to an incorrect trajectory. If this is the case, on a lateral image the rod will
appear in a too posterior position. To prevent this, care should be taken to avoid cut-
ting the fascia too much superiorly or inferiorly before placing pedicle screws.
Additionally, it is generally easier to tunnel the rod from cranial to caudal [5, 8]. In
addition, the distal end of the rod should be placed on the proximal screw and slide
over the screw head. This enables the rod to be under the fascia at a deeper depth.
After the rod has been passed through all screw extensions, it is axially rotated
180°. Before placing the locking/set screws and disengaging the rod, AP and lateral
images should be obtained in order to ensure proper screw-rod engagement and rod
lengths (the rod should have enough length at both the top and the bottom). Set
screws are then utilized to x the screws to the rod. A specialized tool may be used
to move the rod into the screw saddles if the rod does not fully engage the saddles
in its ideal nal position [5, 8, 19].
The rod has been accurately placed through the screw extensions if the screw
extensions are blocked from turning, and if, with proper lighting and suction, the
rod can be directly viewed within the screw extensions. Additionally, correct posi-
tioning can be determined by tactile feedback of rod movements when placing a
screwdriver into the extensions. It is important to ensure that the screw is not too
deep, as this would inhibit angulation of the polyaxial screw and hinder rod accom-
modation. In order to minimize stress between the rods and the screws, the screw
heads should be aligned on lateral image [5].
The last step is wound closure. The wound is closed in layers, and a fascial repair
may be performed if it is large using a zero size vicryl with CT-1 needle followed
by 2.0 vicryl for subcutaneous layer. Closure is achieved with small-diameter
resorbable monolament suture. This can be buried in the dermis with a subcuticu-
lar technique. In cases in which keloid formation is likely, the ends of the suture can
be left out of the body and removed 4–7days after surgery. The wound should be
kept dry and covered. In most patients cyanoacrylate glue is utilized in order to
reduce stress on the skin and serve as a semiocclusive antibacterial barrier. In gen-
eral, a drain is solely recommended in instances in which decompression was per-
formed and there is open lamina or exposed dura [5, 8].
Pearls and Pitfalls
• Surgical table and patient positioning are vital in the acquisition of clear
unobstructed imaging.
• Proper AP and later images should be obtained in 2-D uoroscopy for each
level to be instrumented on.
• A nger can be used in order to guide the cannula down the transverse
process and places the needle near the desired starting point. This decreases
the number of images required and thus exposure to radiation. The trocar
tip should be removed from the cannula to avoid perforating a glove [8].
25 Percutaneous Lumbar Screws
218
Owl’s Eye (Magerl) Technique forPedicle Cannulation
Owl’s eye or Magerl technique for pedicle cannulation utilizes one uoroscope for
imaging along the long axis of the pedicle as opposed to AP imaging. This is an
oblique C-arm view that peers down the barrel of the pedicle. This technique may
be considered if the anatomy of the pedicle is not clear using the standard AP tech-
nique discussed previously. This is benecial as it decreases exposure to ionizing
radiation. However, some pitfalls include the increased C-arm realignment and
increased difculty in handling the uoroscope [5, 8].
Percutaneous Pedicle Screw Fixation Using Image Guidance
Image-guided technology utilizes an intraoperative CT scanner to create virtual
images that help guide the surgeon and that allow customization of screw size. This
technique enables the surgeon to view axial images, which can facilitate more accu-
rate screw placement within the pedicle [20]. It also has the potential to minimize
radiation exposure to the surgical team, as they can step out of the room or hide
behind lead shields during imaging [8, 20, 21]. Furthermore, the use of navigation
has reported accuracy rates of pedicle screw insertion ranging from 92% to 98%.
While the approach is similar to the process outlined for true AP images, there are
• The Jamshidi needles should be docked over the 3 o’clock (right) and 9
o’clock (left) positions before they are entered into the bony cortex.
• Pedicle cannulation and K-wire placement should be performed at all indi-
cated levels utilizing AP images in order to avoid switching between the
AP and lateral C-arm positioning.
• K-wires should be advanced to the anterior half of the vertebral body, tak-
ing care to avoid violation of the anterior cortex. Additionally, caution
should be taken to avoid unintentional K-wire advancement. Marking the
needle 20 mm above the level of the skin can help the surgeon remain
mindful of advancement.
• A rotational or twisting maneuver can be useful in instances where the
K-wire pullout is difcult.
• In order to facilitate rod passage, it is best to avoid sinking the screw too
deep.
• Obtain images to verify accurate placement of screws, screw-rod engage-
ment, and appropriate rod length before locking the construct and remov-
ing the screw extenders and retractors.
• Keep manual control of the guidewire as all instruments are passed over it.
B. L. Cohen et al.
219
some key differences that the surgeon must be aware of. These include the cumber-
some nature of the machine and the need for direct line of sight between the camera
and the navigated instruments. Additionally, image-guided technology requires
additional time to set up and register the instrumentation and reliance on technology
that may fail without bailout. Thus, it may be preferable to utilize the two- dimensional
uoroscopy technique described above per the discretion of the surgeon [20–22].
Navigation set-up will require additional set equipment like the stealth machine,
intraoperative O-arm which can be replaced by preoperative CT, or even a robotic
arm which can be quite expensive as an upfront investment by the institution.
Complications
As discussed previously, much of the appeal of MIS procedures is the decreased
pain and recovery times associated with this approach. Minimizing the risk of
wound infection has contributed greatly to the growing popularity of minimally
invasive techniques. This decline is due to the decreased soft tissue devasculariza-
tion, the reduction in operative site dead space, and reduced intraoperative bleeding.
Nonetheless, many complications seen in the open approach can also be present
with MIS, albeit to a lesser degree. For example, there is still a risk of postoperative
anemia secondary to usual intraoperative excessive blood loss; however since MIS
techniques confer less intraoperative blood loss, this risk is reduced [23].
Additionally, it is important to note that while many of the possible techniques to
avoid complications are the same in both MIS and open procedures, there are some
unique considerations in the use of the MIS technique [5].
Percutaneous lumbar xation enables the muscles to be left intact, thus reducing
muscle destruction. However, this may lead to soft tissue irritation in some patients.
Although self-limiting, this muscle spasm is extremely painful and should be man-
aged appropriately with non-narcotic agents and physical treatments if necessary. In
the use of lumbar screws, complications can arise from misplacement of any of the
instruments and damage to any of the nearby vital structures. It is essential to con-
rm placement with imaging. The K-wire has increased potential for injury as
although it is temporary, it remains in the body for a large amount of time and can
migrate. Thus, K-wire management is vital to avoid unintentional advancement or
pullout. Again, this should be veried with imaging in order to avoid intraoperative
complications relating to mechanical instrumentation. Postoperative complications
can present differently based on its time of onset and severity. These can include
mechanical, neurological, and infectious. Additionally, there have been cases in
which the screw head detached from the stem on postoperative day 1. There have
also been reports of pullout of pedicle screws later in the 2–3weeks into the postop-
erative period [24, 25]. Furthermore, multilevel fusions can negatively affect adja-
cent vertebral levels. As with any new technique, MIS presents a learning curve that
must be acknowledged. The surgeon should be aware of this in order to minimize
complications [5, 10].
25 Percutaneous Lumbar Screws
220
Postoperative Care
Percutaneous pedicle screw xation does not require care beyond that given to a
regular spine surgical patient. These patients can and should be mobilized almost
immediately after surgery in order to reduce the risk of venous thromboembolism,
atelectasis, pneumonia, and skin breakdown. An external orthosis should be used in
higher risk cases such as long segment xation, osteopenia, or compromised xa-
tions. In select cases, electronic bone stimulation can be utilized to promote fusion.
Physical and occupational therapy can be helpful in providing patients activities that
may help reduce the risk of construct failure or nonunion [5, 23].
Limitations
While the advantages of minimally invasive surgery have been disputed in the treat-
ment of localized pathologies, surgeons are recognizing that as the morbidity of the
procedure and/or the debility of the patient rises so do the advantages of this
approach. Increasingly, many authors are demonstrating the use of minimally inva-
sive surgical techniques in the treatment of adult spinal deformity. While there has
not been a study demonstrating that the minimally invasive technique is better than
open surgery, the trend is in that direction due to the advantages mentioned above.
However, some potential limitations arise from decreased visualization of the anat-
omy and the necessity of image guidance, which increases operating times and can
expose the patient and healthcare workers to additional radiation [1, 7].
References
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screw xation. J Clin Neurosci. 2011;18:741–9.
2. Mohamed M, Mohi Eldin ASAH.Percutaneous trandpedicular xation: technical tips and pit-
falls of sextent and pathnder systems. Asian Spine J. 2016;10(1):111–22.
3. Foley KT, Holly L, Schwender JD. Minimally invasive lumbar fusion. Spine J.
2003;28(155):S26–35.
4. Foley KT, Gupta SK, Justis JR, Sherman MC.Percutaneous pedicle screw xation of the lum-
bar spine. Neurosurg Focus. 2001;10(4):1–9.
5. Handbook of minimally invasive and percutaneous spine surgery. St. Louis: Quality Medical
Publishing, INC; 2011. p.154.
6. Danison AP, Lee DJ, Panchal RR.Temporary stabilization of unstable spine fractures. Curr
Rev Musculoskelet Med. 2017;10:199–206.
7. Michael Y, Wang PVM. Minimally invasive surgery for thoracolumbar spibnal defor-
mity: initial clinical experience with clinical and radiographic outcomes. Neurosurg Focus.
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8. Sembrano JN, Yson SC, Santos ERG, Polly DW Jr. Percutaneous pedicle screws. In: Minimally
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9. Harris EB, Massey P, Lawrence J, Rihn J, Vaccaro A, Anderson DG.Percutaneous techniques
for minimally invasive posterior lumbar fusion. Neurosurg Focus. 2008;25(2)
10. DeWald CJ, Stanley T.Intrumentation-related complications of multilevel fusions for adult
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2012;32:N9–N13.
13. Mroz TE, Abdullah KG, Steinmetz MP, Klineberg EO, Lieberman IH. Radiation expo-
sure to the surgeon during percutaneous pedicle screw placement. J Spinal Disord Tech.
2011;24(4):264–7.
14. Hubbe U, Sircar R, Scheiwe C, Scholz C, Kogias E, Kruger MT, Volz F, Klingler J-H.Surgeon,
staff, and patient radiation exposure in minimally invasive transforaminal lumbar interbody
fusion: impact of 3D uoroscopy-based navigation partially replacing conventional uoros-
copy: study protocol for a randomized controlled trial. Trials. 2015;16(142)
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Spinal Disord Tech. 2014;27(7):390–4.
16. Weisse L, Suess O, Picht T, Kombos T.Transpedicular screw xation in the thoracic and lum-
bar spine with a novel cannulated polyaxial screw system. Med Devices (Auckl). 2008;1:33–9.
17. Dahdaleh NS, Smith Z, Hitchon PW.Percutaneous pedicle screw xation for thoracolumbar
fractures. Neurosurg Clin N Am. 2014;25:337–46.
18. Scheer JK, Harvey MJ, Dandaleh NS, Smith ZA, Fessler RG.K-wire fracture during mini-
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Indian J Neurotrauma. 2005;2(2):143–8.
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25 Percutaneous Lumbar Screws
223© 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_26
Chapter 26
Percutaneous Iliac andS2AI Fixation
LaurenMatteini
Pelvic instrumentation in the form of iliac bolts [1] or S2AI screws provides distal
xation to long-construct fusions for deformity or scoliosis [2]. The techniques,
while similar, provide unique challenges, such as necessitating cross-connectors for
iliac bolts, or breaching the sacroiliac (SI) joint in S2AI.Anatomically, the axial
spine consists of vertebrae from cervical to lumbar, ending atop the sacrum distally.
The sacrum articulates with the ilia bilaterally forming a at sacroiliac (SI) joint
with minimal motion. Both the ilium and the sacrum provide distal xation points
for instrumented spinal fusions. Studies have shown a high pseudoarthrosis rate at
the lumbosacral junction when distal xation ends at S1 [3–5]. Several biomechani-
cal studies have shown increased rigidity at the lumbosacral junction with the addi-
tion of iliac xation [6–9]. Alternatively, pelvic xation can serve as an adjunct to
internal xation or denitive treatment for comminuted sacral fractures and pelvic
ring injuries with spinopelvic dissociation.
The ilium provides a bony corridor from the posterior superior iliac spine (PSIS)
to the anterior inferior iliac spine (AIIS) that can hold one or two large diameter
screws. The sacroiliac joint is a wide, at joint between the sacrum and the ilium
bilaterally. This joint has two areas, the inferior half of which is lined with cartilage
and does allow minimal motion. S2AI screw trajectory is such that placement does
not always penetrate this area of articulation [10] and the long-term effects of such
are not well-studied.
Radiographically, this corridor of bone is visualized on the obturator outlet view
and known as the teardrop. The teardrop is the conuence of three points: the pos-
terior superior iliac spine, the sciatic notch, and the anterior inferior iliac spine [11].
This starting point can be entered from the PSIS with trajectory toward the AIIS or
via a sacral start point in S2 and directed across the sacroiliac joint toward the
L. Matteini (*)
Department of Orthopaedic Surgery and Rehabilitation, Loyola University Chicago,
Maywood, IL, USA
224
AIIS.Trajectory should be conrmed on the iliac outlet view to ensure the greater
sciatic notch is not penetrated. Alternatively, placement of these screws can be per-
formed with the assistance of CT-guided navigation [12].
Technical Notes
The S2AI start point is inferior and along the lateral edge to the rst dorsal foramen.
An AP view of the sacrum can provide visualization of the start point as seen in
Fig.26.1. With the trajectory toward the greater trochanter for reference, an incision
should be made approximately 1/2cm medial to the start point to allow placement
of the screw without issues with the skin. Sharp incision is made and dissection
through the fascia is crucial. A cannulated needle, such as the Jamshidi™, is then
placed onto the start point with an AP sacrum. The C-arm is then brought into the
obturator outlet view to identify the teardrop which demonstrates the iliac corridor,
as shown in Fig.26.2. The ideal image as shown in Fig.26.2a shows the teardrop
sitting atop the hip joint. The cannulated needle is then advanced down the length of
the iliac corridor. The S2AI trajectory appears more horizontal and with more pos-
teriorly oriented as it enters the sacrum more medially. At approximately 40mm, the
c-arm is rotated to view the iliac wing, iliac outlet view (Fig.26.2c). On this image,
one visualizes the SI joint and the needle crossing it into the ilium, as well as the
trajectory across the ilium but superior to the greater sciatic notch. Once conrmed
that the trajectory is in bone, the cannulated needle can be passed into the ilium to a
depth of up to 120mm [12]. The center needle is removed, and a guidewire is placed
down its length. The remainder of the cannulated needle is removed. The guidewire
can be used like a ball-tip probe to feel the track and ensure there is no breach.
Fig. 26.1 Cadaveric
uoroscopic images of S2AI
xation. AP sacrum
demonstrating S2 start point
on prone specimen, left.
Right-sided rst and second
dorsal foramen are outlined
L. Matteini
225
ab
c
Fig. 26.2 Cadaveric uoroscopic images of S2AI xation. Images (a) and (b) demonstrate the
teardrop view from obturator-outlet radiograph. The femoral heads are removed from this cadav-
eric specimen, but the teardrop is visualized atop the acetabulum. The cannulated needle/guidewire
trajectory has a more horizontal and posterior orientation. The notch view (c) shows the guidewire
across the SI joint and superior to the greater sciatic notch
Fig. 26.3 Cadaveric
uoroscopic image of iliac
xation. Image demonstrates
the teardrop view from
obturator-outlet radiograph.
The femoral heads are
removed from this cadaveric
specimen, but the teardrop is
visualized atop the
acetabulum. The guidewire
trajectory is directed down
the length of the ilium
26 Percutaneous Iliac andS2AI Fixation
226
Placing an iliac bolt requires an incision again medial to its start point on the
PSIS.Dissection is carried down through fascia to the PSIS.Through even a small
incision, a narrow leksell rongeur can be used to remove cortical bone in order to
countersink the head of the screw, making it less prominent. Alternatively, a high-
speed burr can be utilized to provide a cortical window for screw placement.
Following this, a standard pedicle gearshift probe may be utilized to develop the
tract from PSIS to AIIS in the iliac wing for iliac bolt placement. Again, the trajec-
tory is toward the greater trochanter, or visualized on the teardrop, obturator outlet
view. Once the iliac wing is probed, a guidewire is placed down the length of the
corridor for placement of the cannulated screw, as demonstrated in Fig.26.3.
Connecting one’s S2AI screw to the cephalad construct is simpler than an iliac
bolt, as the placement is such that the head of the screw is in-line with the construct.
Whereas the iliac bolt may require an additional connection to the cephalad con-
struct requiring larger mini-open incision or a separate incision altogether. In certain
cases, such as lumbopelvic xation for lumbopelvic dissociation, where an S1
screw is not placed, connecting an iliac bolt to L5 is feasible without additional con-
nections, as shown in Fig.26.4.
a
dc
b
Fig. 26.4 Post-operative radiograph (a) and CT (b–d) images depicting adjunct lumbopelvic xa-
tion for comminuted pelvic ring injury. The iliac bolt traverses the ilium passed the transsacral
screw and is afxed to the L5 pedicle screw without the need for a transconnector
L. Matteini