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49 Transpedicular Stabilization withFreehand Technique ontheThoracic Spine
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5 mm of inferior articular process is removed so as to
expose the base of the superior articular process.
49.6.2 Instrumentation [1–6]
• The starting point for each thoracic level is slightly variable and is based on the posterior element anatomy of the
transverse process and the base of superior articular facet.
The ideally entry point in the thoracic pedicle is at the
junction of a horizontal line along the inferior border of
facet joint and vertical line at the junction of the outer third
and inner two-thirds of the facet joint. The starting point in
the proximal region (T1–T3) is at the middle of transverse
process; in the mid- and lower thoracic region, it is at supe-
Fig. 49.2 Preoperative X-ray with the patient in prone position on the
operative table. The measurement of the sagittal angle of all pedicles to
be instrumented
Fig. 49.3 The wide posterior exposure of the thoracic spine
rior third of transverse process, and in T12, the entry point
is at middle and tip of transverse process (see Fig.49.4).
• Before making the entry into the pedicle, initial neuromonitoring recordings with SSEP and TMEP are performed to establish the preinstrumentation neural status
of the patient.
• The entry point is made rough with rouger or a 3.5 mm
acorn-tipped burr to prevent slippage of awl, to visualize
of cancellous bone, and to create space to lodge the head
of pedicle screw.
• Then the further passage in the pedicle is made with
appropriate amount of ventral pressure using the gearshift
(2mm blunt-tipped pedicle nder).
• The surgeon must be careful to the axial and sagittal position
of vertebrae space to position the probe down the pedicle
shaft appropriately. The information about the axial and sagittal angle is given by the images obtained preoperatively.
• In the thoracic spine without scoliosis and kyphosis, the
pedicle nder should be angled 7–10 toward the midline
and 10–20 caudally. When the spine is deformed or scoliotic, these angles are different and asymmetrical.
• The trajectory of pedicle screw is completed with the
gearshift going down to the pedicle and reaching the cancellous bone near to anterior cortex of vertebra body. At
this moment, new neuromonitoring recordings are performed with SSEP, TMEP, and EMG.The EMG is taken
with direct stimulation of gearshift inserted into the pedicle trajectory. These data are used to investigate the integrity of pedicle trajectory (see Fig.49.5).
• The surgeon sensitivity during the penetration of cancellous bone through the pedicle to vertebral body is an
important step and depends on appropriate learning curve.
Any sudden advancement of the pedicle nder suggests
penetration into soft tissue, and thus a pedicle wall violation or vertebral body violation has occurred. Decision of
screw diameter and length is based on preoperative
assessment but conrmed intraoperatively.
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P. T. M. Cavali
Fig. 49.4 The starting point for each thoracic pedicle
Fig. 49.5 The EMG with direct stimulation of gearshift immediately
after complete perforation of pedicle trajectory
Fig. 49.6 Palpation of ve walls of pedicle tract with exible ball-
tipped probe
• It is important to avoid penetration of the anterior cortex
to prevent visceral and vascular injuries. Approximately
90% of strength of the screw comes from the pedicle and
posterior half of the vertebral body.
• Once the trajectory of pedicle screw is completed and
neuromonitoring data have not demonstrated any signal
of wall violation, the pedicle nder (gearshift) is removed.
The tract is visualized to make sure that only blood is
coming out.
• Excessive bleeding from the pedicle hole may indicate
epidural bleeding secondary to medial wall violation, and
the presence of cerebrospinal uid means more medial
violation with dural lesion.
• At this point, if any of these situation occurs such as inappropriate neuromonitoring data or signs of violation of
pedicle wall, there is an opportunity to redirect the pedicle
nder into an appropriate position in the pedicle so that
complete intraosseous borders can be obtained.
• Palpation of pedicle tract is the next step. With a exible
ball-tipped probe, the ve walls are palpated (see Fig.49.6).
cd
49 Transpedicular Stabilization withFreehand Technique ontheThoracic Spine
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345
a
b
Fig. 49.7 Preoperative
assessment of the patient (a,
b) and intraoperative
conrmation and
documentation immediately
after complete
instrumentation (c, d)
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• The integrity of ve walls: medial, lateral, superior
(cranial), inferior (caudal), and oor (anterior cortex) is
essential to insert the screw. The most important walls
are medial and inferior because of the presence of the
spinal cord and nerve root, respectively. In the literature, the critical violation of any pedicle wall is dened
as more than 2mm, and the most common violated wall
is the lateral followed by the medial one.
• The measurement of pedicle tract is performed with the
same exible ball-tipped probe after conrmation of
integrity of the ve walls. Then the tract is tapping, and an
adequate screw in length and diameter is inserted into the
pedicle.
• The next imperative step is the conrmation and documentation of intraosseous placement of all pedicle screw
via images using uoroscopy or radiography at the end of
surgery (Fig. 49.7) and by neuromonitoring data
performed after insertion of each screw during the surgery
with SSEP, TMEP, and triggered EMG.
• With the screws inserted in appropriated position, the previously rods are placed according to the preoperative
plan.
P. T. M. Cavali
49.7 Tips andTricks
• In order to prevent violation of the medial wall of pedicle,
the half medial part of the superior facet and its caudal
projection must be avoided (see Fig.49.8).
• If the pedicle screw was misplaced and its reposition was
not possible in the appropriate place, the screw can be
inserted by the in-out-in technique (more lateral and more
convergence technique).
• The insertion of pedicle screw in scoliotic spine can be
difficult, especially on the concave side; then the orientation of the surface of superior facet can be helpful
once the direction of pedicle screw has an angle
Fig. 49.8 The red region is the half medial part of the superior facet
(must be avoided), and the blue landmark is the entry point of pedicle
screw
slightly perpendicular to the surface of the superior
facet. This is useful for axial and sagittal orientation
(see Fig.49.9).
49 Transpedicular Stabilization withFreehand Technique ontheThoracic Spine
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ab
347
Fig. 49.9 The perpendicular relationship between axis of pedicle and surface of superior facet, even in sagittal plane (a) as in the axial plane (b)
References
1. Bergeson RK, Schwend RM, DeLucia T, etal. How accurately do
novice surgeons place thoracic pedicle screws with the free hand
technique? Spine. 2008;33(15):E501–7.
2. Chung KJ, Suh SW, Desai S, etal. Ideal entry point for the thoracic pedicle screw during the free hand technique. Int Orthop.
2008;32:657–62.
3. Kim YW, Lenke LG, Kim YJ, etal. Free-hand pedicle screw placement during revision spinal surgery. Spine. 2008;33:1141–8.
4. Modi HN, Suh SW, Fernandez H, et al. Accuracy and safety of
pedicle screw placement in neuromuscular scoliosis with free-hand
technique. Eur Spine J. 2008;17:1686–96.
5. Oram E, Polly DW, Gilbert JRTJ, etal. Is it safer to place pedicle
screws in the lower thoracic spine than in the upper lumbar spine?
Spine. 2007;32:9–54.
6. Schizas C, Theumann N, Kosmopoulos V.Inserting pedicle screws
in the upper thoracic spine without the use of uoroscopy or image
guidance. Is it safe? Eur Spine J. 2007;16:625–9.
Posterior Correction ofAdolescent
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Idiopathic Scoliosis (AIS)
TorstenBräuer
50
50.1 Introduction and Core Message
Operative correction of AIS has evolved tremendously
over the last decades trending in the favored use of posterior correction by means of all-pedicle-screwconstructs, stiffer rods, higher screw density, and last but
not least intraoperative neuromonitoring (IONM) substantially supporting intraoperative distraction and derotation of the deformed spine rendering highly effective
correction. A satisfactory correction of AIS is favored
by the use of xed angle screws (FAS) versus multiaxial
screws (MAS), due to the fact of unsurpassed stability
of FAS in comparison to all other pedicle screw designs.
The use of FAS, whenever possible, may address more
effectively correction of the deformity both in the coronal plane by transporting FAS on stiff rods in a controlled manner leading to a relatively elongation of the
posterior spine, as well as in the sagittal plane by allowing to introduce superior forces on the screws with less
deterioration of the screw stability in order to perform
consequent spine de-rotation with a modied DVR procedure removing the AIS pathognomonic hunchback.
40° up to 6:1. The threshold for operative treatment of AIS
are COBB angles of 40°–50° in order to prevent rising
COBB angles later in life of the patient, if not treated. AIS
can occur as a single, double, or triple curve and may be
located in the thoracic spine, the lumbar spine or both thoracic and lumbar spine. Natural history of untreated AIS is
reported in recent literature to be back pain (even though not
disabling), cosmetic concerns and suggests that AIS does not
lead to severe long-term health consequences—in contrast to
reports from the late twentieth century reporting severe back
pain, pulmonary disablement, increased risk of early death,
and social isolation (Figs.50.2, 50.3, 50.4, 50.5, and 50.6).
50.3 Contraindications
The main contraindication to posterior scoliosis surgery
would be medical instability and inability to survive surgery.
Predominantly most of the AIS patients eligible for posterior
correction and xation nd oneself in ASA I and II with no
or little evidence for osteopenia/osteoporosis (Figs. 50.7,
50.8, 50.9, 50.10, 50.11, and 50.12).
50.2 Indications
Adolescent Idiopathic Scoliosis (AIS) (see Fig. 50.1) is
stated in current literature with an average prevalence of
0.47–5.2% and therefore has to be considered as a common
disease interfering with patients attaining puberty. The
female-to-male ratio can vary substantially from 1.5:1 to 3:1
and will grow with increasing age. Curves with higher Cobb
angles will affect girls even more: female-to-male ratio gains
in curves between 10° and 20° from 1.4:1 to curves above
T. Bräuer (*)
Spine Section of the Orthopedic Department Norwegian University
of Science and Technology (NTNU), Trondheim, Norway
e-mail: Torsten.Brauer@stolav.no; torsten.brauer@hotmail.com
© Springer-Verlag GmbH Germany 2023
U. Vieweg, F. Grochulla (eds.), Manual of Spine Surgery, https://doi.org/10.1007/978-3-662-64062-3_50
50.4 Technical Prerequisites
FAS (xed angle screws—enabling more consequent correction), MAS (multiaxial screws—primarily used by the author
as most proximal implant averting proximal junctional
kyphosis [PJK]) which substitutes FAS if preferred. The use
of hooks instead of pedicle screws is possible, however in
recent times, is less prevalent but provides on occasion to be
used as a salvage procedure when applying pedicle screws is
not achievable. Stiffer (CoCr stronger than Titanium Alloy)
and thicker rods (stiffness increases to the fourth power of its
diameter!), cross-connectors (not mandatory with a screw
density tending to 2.0), bending bars which provide faster,
smoother, more efcient, and harmonic contouring of the
rods, avoiding (in comparison to the use of the French bender
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T. Bräuer
Fig. 50.1 3D-print in 4 aspects (from anterior-left-posterior-right) in the ratio 1 to 1 of the presented AIS case, which was obtained preoperatively
on the basis of a low-dose CT
forceps) multiple break-points of the rods which may weaken
the stability of the rod in the long run (CoCr less forgiving
than Titanium alloy for interchanging bending). Likewise
several rod reducers to accomplish on the level inserting of
the rod to the screws protecting against undesirable “pull- out”
of the FAS/MAS and by doing so eliminating the need for
reduction tabs. The author encourages the bilateral use of distraction forceps to assist scheduled screw transport on the
rods (explicit explanation of the technique follows in the
course of this chapter), just as well the use of four counter
torques enabling to perform a modied straight forward
Direct Vertebral Rotation (DVR). Besides coronal and in situ
benders for exceeding contouring of the already screwinserted rods for additional correction of the spinal deformity
and a radiolucent table to ease X-ray control after completed
setting of the screws, especially if there is the desire to use
uoroscopic assisted or intraoperatively navigated setting of
the pedicle screws instead of freehand placement.
Last but not least, Intraoperative Neuromonitoring
(IONM), which has become the gold standard providing
50 Posterior Correction ofAdolescent Idiopathic Scoliosis (AIS)
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351
Fig. 50.4 32-Channel intraoperative neuromonitoring
Fig. 50.2 Monoaxial pedicle screw (FAS)
Fig. 50.3 Forming of the CoCr-rod using bending bars with less pres-
sure point generation compared to the use of a French bender and the
option of deforming the metallic microstructure more by tension than
by pressure
Fig. 50.5 Posterior aspect displaying shoulder imbalance, thoracic,
and thoracolumbar hunchback
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T. Bräuer
Fig. 50.6 Anterior aspect
both SSEPs (somatosensory-evoked potentials) and MEPs
(motor-evoked potentials) and offering maximal security for
the time being, has to be considered as compulsory to inhibit
neurologic disaster to the best possible conditions.
50.5 Planning
The purpose of AIS correction is to achieve optimal deformity improvement by maintaining as much as possible
mobile motion segments in the vertebral column. Preoperative
evaluation focuses on details of curve location, magnitude,
and exibility. These parameters are used in combination
with patient maturity factors (e.g., RISSER-sign, menarche)
to determine optimal treatment decision, but denitive studies are not yet available that put in order specic surgical
tactics. The goal is at all times to fuse as little of the spine as
possible while effectively treating existing major curvature.
At present, the Lenke classication system is regularly used
Fig. 50.7 Better visibility of both thoracic and thoracic lumbar gibbus
when bending the patient forward
Fig. 50.8 Side view presenting the rotation in both the thoracic and
thoracic lumbar spine appearing as double hunchback
to categorize adolescent idiopathic scoliosis. This system,
rst published in 2001, consists of the following three
components:
• Curve type (1, 2, 3, 4, 5, or 6).
• Lumbar spine modier (A, B, or C).
• Sagittal thoracic modier (−, N, or +).
50 Posterior Correction ofAdolescent Idiopathic Scoliosis (AIS)
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353
Fig. 50.9 X-ray coronal view Lenke type 4CN Triple Major
On coronal and sagittal radiographs, the six types specied by Lenke etal. have specic characteristics that distinguish structural and nonstructural curves in the proximal
thoracic (PT), main thoracic (MT), thoracolumbar (TL), and
lumbar (L) regions. Regional curves are measured, the major
curve is recognized, and a determination is made as to
whether the minor curve is structural (i.e., curve does not
bend out on bending pictures below 25°). The curve is then
allocated to the relevant numeric type (1 through 6). The
lumbar spine modier is made on the relation of the center
Fig. 50.10 X-ray sagittal view Lenke type 4CN Triple Major
sacral vertical line (CSVL) to the apex of the curve. If the
CSVL passes between pedicles of apical lumbar vertebrae,
the modier A is assigned; if it touches a pedicle, the modier B is assigned; and if it does not touch apical lumbar vertebrae, the modier C is assigned. The sagittal thoracic
modier is based on the sagittal Cobb angle from T5 to T12.
If the angle is less than 10° (hypokyphotic), the modier is
assigned; if it is 10–40° (normal), the modier N is assigned;
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