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Procedure 22 | Posterior Thoracolumbar Fusion Techniques for Adolescent Idiopathic Scoliosis 217
FIGURE 22-14 FIGURE 22-15
S T E P 3 B PI T FA L L S
• Do not spin the drill too fast. A
fast-moving drill can go through
concrete or steel with little tactile
feedback. A slow-moving drill will
provide much feedback, as it touches
cortical versus cancellous bone.
S T E P 3 P EA R L S
• The surgeon should be able to
distinguish the dense medial cortical
bone surrounding the spinal cord from
the pedicle by feel. This drill technique
depends heavily on tactile feedback; so,
the surgeon’s hands should be kept
“soft” and the drill spun slowly.
• In a type D pedicle of the thoracic spine
(absent pedicle channel), the surgeon
may bypass the pedicle laterally and
enter into the vertebral body. There are
no vital structures in this area.
• If it is difficult to enter the pedicle,
consider a laminotomy and feel the
pedicle from the inside using a dental
instrument. The surgeon may also use
fluoroscopy to visualize the pedicle.
FIGURE 22-16
•
Step 3B:
A 1.9-mm wide drill bit is used at a very slow speed to enter the
pedicle (Figure 22-14). The surgeon’s hands must be kept “soft” to allow a
change of direction based upon the manual feedback of the drill. The 1.9-mm
drill is drilled into a depth of about 22 mm, which is the extent of the flute
length of this particular drill bit. A ball-tipped pedicle probe is used to verify
that the pedicle hole is completely surrounded by bone and that there has
been no cortical violation of any of the five walls of the pedicle—medial,
lateral, cephalad, caudad, and floor (Figure 22-15).
Step 3C:
•
The hole is widened with a 3-mm drill bit (Figure 22-16). A balltipped probe, again, verifies that the pedicle hole is completely surrounded
by bone.
218 Procedure 22 | Posterior Thoracolumbar Fusion Techniques for Adolescent Idiopathic Scoliosis
FIGURE 22-17 FIGURE 22-18
FIGURE 22-19 FIGURE 22-20
•
S T E P 3 C ON T R O V ER S I E S
• Pedicle screws may be placed at every
level, particularly in children with
a significant amount of growth
remaining, to prevent crankshaft
phenomenon.
• For standard adolescent idiopathic
scoliosis, the authors place a pedicle
screw at every level on the left
(concave) side, because this is the
correcting rod and will distribute the
stress over multiple points. For the right
(convex) rod, a minimum of two pedicle
screws should be placed in the top and
the bottom of the construct, and two
pedicle screws should be placed at the
apex to allow for derotation.
Step 3D:
should enter very easily, with little force. If the intent is to place a 35-mm
screw, the gearshift pedicle probe will be inserted to about 40 mm of depth
(Figure 22-17). A ball-tip probe is then used again to ensure that there is no
cortical breech, and it should verify solid bone at the bottom of the channel
(Figure 22-18). A clamp is placed at the probe–bone interface to mark the
length of the pedicle (Figure 22-19). The ball-tip probe is then held up against
the screw that has been selected for insertion, to make certain the screw is
the proper length. This eliminates communication or selection errors that
could result in placing a wrong-sized screw (Figure 22-20).
Step 3E:
•
drill, but it could also be done by hand (Figure 22-21).
A gearshift pedicle probe is used to finely dilate the hole. The probe
The pedicle screw is then inserted. The authors do this with a power
Procedure 22 | Posterior Thoracolumbar Fusion Techniques for Adolescent Idiopathic Scoliosis 219
S T E P 3 P IT FA L L S
• As the pedicle screw goes in, the
transverse process may push on the
head and direct the pedicle screw to a
different location. Often, part of the
transverse process must be removed to
avoid this. Anteroposterior (AP) and
lateral imaging may be used to ensure
that the pedicle screws are in the
correct position.
• Whenever the pedicle screw tips appear
to touch in the AP image, it is likely
that one or both of the screws are in
the canal. Also, if a screw tip crosses
the midline of the vertebral body,
suspect a medial wall violation (Figure
22-22).
• Make certain that the uppermost screw
is not in the disk, because this may
cause late pain.
• If one cannot obtain solid fixation with
a pedicle screw, consider alternative
fixation techniques, such as a
sublaminar wire or hook.
FIGURE 22-21
FIGURE 22-22
220 Procedure 22 | Posterior Thoracolumbar Fusion Techniques for Adolescent Idiopathic Scoliosis
FIGURE 22-23 FIGURE 22-24
FIGURE 22-25
S T E P 4 P EA R L S
• For very stiff curves, complete posterior
osteotomies and use of reduction
screws are helpful.
• Before starting the reduction maneuver,
make certain the patient’s mean arterial
pressure is 75 to 80 mm Hg or higher.
• Sterile mineral oil applied to the rod
maximizes mobility of the entire system
and minimizes friction of the screws on
the rods.
• Vertebral column manipulation works
best with fixed or uniaxial screws. In
general, the authors place uniaxial
screws on the right (convex) side at the
apex of a Lenke 1 curve, as well as on
the right side of the countertorque,
customarily at approximately L1.
FIGURE 22-26
Step 4: Rod Placement and Correction of Deformity, Including Vertebral Derotation
n
A malleable template is used to determine the length of the rod, erring toward
cutting the rod too long, rather than too short (Figure 22-23).
n
The left correcting (concave) rod is placed first in the standard scoliosis
patterns—hypokyphotic or normokyphotic curves. The right (convex) rod may
be placed first in a hyperkyphotic curve.
n
Screw caps are placed on the rod very loosely to allow rod motion (Figure
22-24).
n
Vertebral column manipulators are placed at the apex of the curve, as well as
at the end vertebra, such as L1 for a typical Lenke 1 curve (Figure 22-25). Torque
and countertorque are applied to the vertebral column manipulators for a vertebral column derotation (Figure 22-26).
Procedure 22 | Posterior Thoracolumbar Fusion Techniques for Adolescent Idiopathic Scoliosis 221
FIGURE 22-27 FIGURE 22-28
S T E P 4 P IT FA L L S
• If there is not enough kyphosis bent
into the rod or the rod is not stiff
enough, it is easy to lose thoracic
kyphosis. In the majority of curves, the
authors use a stainless steel
or a rod of equivalent stiffness to
produce and maintain physiologic
kyphosis.
1
-inch rod
4
S T E P 4 C ON T R O V ER S I E S
• The authors believe that the best
way to assist the lumbar curve for
spontaneous correction is to fully
derotate the lower instrumented
vertebra and apply appropriate
compression and distraction so that
the vertebra is perpendicular to the
rods. Others believe that the lower
instrumented vertebra of a selective
thoracic fusion should be tilted into
the lower lumbar curve to prevent
decompensation.
S T E P 4 I MP L A N T
C O N T RO V E R S IE S
• Many surgeons treating deformities
prefer stainless steel for its strength and
ability to bend.
• Titanium may be preferred for MRI
compatibility.
• Cobalt chrome rods are relatively new
and may combine the best of strength
and MRI compatibility but may be too
stiff for pedicle screws not designed for
this type of rod.
n
The rod is then rotated 90 degrees so that the scoliosis may turn into physi-
ologic kyphosis in the thoracic spine and lordosis in the lumbar spine (Figure
22-27).
n
Screws are first tightened at the apex of the curve and, in the thoracic region,
distraction is placed between the screws before tightening them to correct the
scoliosis in the coronal plane and produce kyphosis in the sagittal plane. In the
lumbar region, compression is placed to correct scoliosis and produce lordosis.
After all screws are tightened, the vertebral column manipulators are removed.
n
For an upper left thoracic curve with significant derotation, a separate derotation
maneuver may be performed between the apex of the upper thoracic and midthoracic curve.
n
Additional rod contouring can be performed using in-situ or “L” benders as
needed. Care must be taken with “L” benders to maintain kyphosis, because
the rod customarily wants to flatten out.
n
The right rod is then placed. Often, the amount of kyphosis in the right rod is
underbent to place a downward force on the right side of the apical vertebra,
to help further derotate the spine. Appropriate compression and distraction is
performed (Figure 22-28).
n
Transverse connectors (“cross-links”) are generally not needed.
Step 5: Closure
n
Make certain all set screws are given a final tightening.
n
AP and lateral fluoroscopy images are taken to evaluate correction of the spine
and to confirm the correct position of pedicle screws, ensuring no evidence of
medial or lateral breech.
n
Use a M8 Midas Rex burr or equivalent to perform decortication of all exposed
bone.
n
Autograft is used from the spinous processes and facet joints, combined with
cortical/cancellous crushed allograft placed directly along the exposed and
decorticated bone underneath the rods. Areas of open canal may be covered
with Gelfoam, being careful not to place the Gelfoam or bone graft into the
canal.
n
To relieve postoperative pain by delivering bupivacaine, the authors typically
place On-Q catheters (ON-Q PainBuster Post-Op Pain Relief System, I-Flow
Corporation, Lake Forest, Calif.) along the implants at this stage.
222 Procedure 22 | Posterior Thoracolumbar Fusion Techniques for Adolescent Idiopathic Scoliosis
n
Closure is performed with a running 1 Vicryl suture in the muscle layer, followed
by another running 1 Vicryl suture to close the fascia. The authors place a
Hemovac drain above the fascia and then close the adipose and subcutaneous
layers with one or more running 0 Vicryl sutures. Skin is closed with a 3-0
Monocryl suture in a running subcuticular fashion, followed by Dermabond
(Ethicon, Somerville, N.J.) applied over the closed incision. Benzoin is applied at
the sides of the incision, and Steri-Strips are placed after the Dermabond has
dried. The wound is then dressed with sterile 4 × 4 gauze and Tegaderm (3M,
St. Paul, Minn.) dressings.
Postoperative Care and Expected Outcomes
n
The patient is transferred to a standard hospital floor after recovery from anes-
thesia in the postanesthesia care unit (PACU).
n
Frequent incentive spirometry is encouraged.
n
Usually patients sit up by postoperative day 1 and walk by postoperative
day 2.
n
Typically, patients go home by postoperative day 5. Standing PA and lateral
spine radiographs are obtained before discharge (Figure 22-29, A and B, respectively). Patients return to school in 3 to 4 weeks and return to competitive sports
at approximately 3 months (Figure 22-30).
n
The authors do not routinely use postoperative bracing, unless there is an
intraoperative concern about bone quality or the patient has known compromised bone health.
A
FIGURE 22-29, A-B
B
Procedure 22 | Posterior Thoracolumbar Fusion Techniques for Adolescent Idiopathic Scoliosis 223
B
A
FIGURE 22-30
Evidence
Edwards CC, Lenke LG, Peelle M, et al. Selective thoracic fusion for adolescent
idiopathic scoliosis with C modifier lumbar curves: 2-16 year radiographic and
clinical results. Spine 2004;29:536-46.
The authors sought to determine the radiographic and clinical outcomes
following selective thoracic fusion in the treatment of main thoraciccompensatory C-modifier lumbar curves, with a mean of 5-years follow-up. They
found that lumbar curve correction occurs at the upper segments of the curve
and that satisfactory clinical and radiographic outcomes can be achieved
without fusion of the lumbar curve.
Kim YJ, Lenke LG, Bridwell KH, Cho YS, Riew KD. Free hand pedicle screw
placement in the thoracic spine: is it safe? Spine 2004;29:333-42.
This study evaluated 3204 transpedicular thoracic screws placed over a 10-year
period in 394 patients, using a freehand technique. No screws caused any
neurologic, vascular, or visceral complications. The authors concluded that the
freehand technique of thoracic pedicle screw placement, when performed in a
stepwise and consistent manner, is an accurate, reliable, and safe method of
thoracic pedicle screw insertion.
Kim YJ, Lenke LG, Cheh G, Riew KD. Evaluation of pedicle screw placement in
the deformed spine using intraoperative plain radiographs: a comparison with
computerized tomography. Spine 2005;30:2084-8.
Using postoperative CT scans to evaluate pedicle screw position, the authors
developed plain radiographic criteria to judge the accuracy of screw position
intraoperatively during index operations. Three radiographic criteria were
found to be sensitive and accurate for detecting lateral wall pedicle screw
violations, and also were specific and accurate for assessing medial wall
violations in scoliotic and kyphotic spinal deformities: (1) violation of the
harmonious segmental change of the tips of the inserted screws in the plain PA
radiograph suggested medial or lateral violation of the pedicle wall; (2) no
crossing of the medial pedicle wall by the inserted pedicle screw, as seen in the
plain PA radiograph, suggested lateral violation of the pedicle wall; and (3)
crossing of the imaginary midline of the vertebral body in the plain PA
radiograph by the position of the tip of the inserted pedicle screw suggested
medial violation of the pedicle wall.
224 Procedure 22 | Posterior Thoracolumbar Fusion Techniques for Adolescent Idiopathic Scoliosis
Lenke LG, Betz RR, Harms J. Adolescent idiopathic scoliosis: a new classification to
determine extent of spinal arthrodesis. J Bone Joint Surg Am 2001;83:1169-81.
This study describes a comprehensive classification system for adolescent
idiopathic scoliosis, which is based on three components: curve type (1 through 6),
a lumbar spine modifier (A, B, or C), and a sagittal thoracic modifier (−, N, or +).
This classification system was found to have improved interobserver and
intraobserver reliability over the King classification system.
Lenke LG, Edwards CC, Bridwell KH. The Lenke classification of adolescent
idiopathic scoliosis: how it organizes curve patterns as a template to perform
selective fusions of the spine. Spine 2003;28(20S):S199-207.
This retrospective radiographic review of 44 patients analyzes how the Lenke
classification for AIS can provide a template for determining which curve
patterns are appropriate for selective fusion of the spine. The authors found
that selective thoracic or thoracolumbar/lumbar fusions of the major curve can
be successfully performed, even when the minor curve completely deviates from
the midline. Decision making is based on the Lenke classification system, the
analysis of structural criteria between the planned fused and unfused regions of
the spine, and the clinical examination of the patient.
Newton PO, Yaszay B, Upasani VV, et al. Preservation of thoracic kyphosis is
critical to maintain lumbar lordosis in the surgical treatment of adolescent
idiopathic scoliosis. Spine 2010;35:1365-70.
This is a retrospective analysis of prospective data collected from a multicenter
series of 251 patients with a Lenke 1 deformity. The patients underwent
selective thoracic fusion by an anterior versus a posterior approach and had a
minimum of 2-year follow-up. The authors stress the importance of restoring
thoracic kyphosis at the time of the index operation, to prevent loss of lumbar
lordosis and resultant flat-back deformity in the future.
Parent S, Labelle H, Skalli W, et al. Thoracic pedicle morphometry in vertebrae
from scoliotic spines. Spine 2004;29:239-48.
A total of 325 thoracic vertebrae from scoliotic specimens and 358 thoracic
vertebrae from normal specimens were measured. The authors found that
pedicle width is significantly smaller on the concavity of moderate to severe
thoracic curves and advocate caution with the use of pedicle screws on the
concavity of scoliotic curves, especially at the apex of the deformity.
Ross PA, Smith BM, Tolo VT, Khemani RG. Continuous infusion of bupivacaine
reduces postoperative morphine use in adolescent idiopathic scoliosis after
posterior spine fusion. Spine (Phila PA 1976) 2011;36:1478-83.
This is a retrospective study of 244 children, aged 10 to 18 years, who
underwent posterior instrumented spinal fusion for adolescent idiopathic
scoliosis. Significantly fewer patients receiving continuous infusion of local
anesthetic (bupivacaine) through a catheter required a continuous basal
infusion of morphine, resulting in an overall reduction of opioid use on
postoperative day 1.
Suk SI, Kim WJ, Kim JH, et al. Indications of proximal thoracic curve fusion in
thoracic adolescent idiopathic scoliosis. Spine 2000;25:2342-9.
This is a retrospective review of 40 patients who underwent fusion for
idiopathic thoracic scoliosis. The authors concluded that idiopathic thoracic
scoliosis with a proximal thoracic curve of more than 25 and a level or elevated
left shoulder should be considered a double thoracic curve pattern and should
be treated by fusing both the proximal and the distal curves when using
segmental instrumentation.
Suk SI, Lee CK, Kim WJ, et al. Segmental pedicle screw fixation in the treatment
of thoracic idiopathic scoliosis. Spine 1995;20:1399-405.
This is the earliest article to directly compare all-hook, hybrid, and all-pedicle
screw constructs regarding initial correction and loss of correction at follow-up. All
pedicle screw constructs had superior correction and maintenance of correction.
P R O C ED U R E 2 3
Thoracoplasty for
Rib Deformity
Suken A. Shah and Avrum Joffe
I N D I CAT I O NS P I T F A L L S
• Detrimental to pulmonary function,
even at 2 years postoperatively
• Additional muscle dissection, blood
loss, and operative time
I N D I CAT I O NS
C O N T RO V E R S IE S
• Use of thoracoplasty seems to be on
the wane because:
• Early detection and treatment
of scoliosis is common, before
development of severe curves.
• Segmental spinal instrumentation
with pedicle screws allows threedimensional realignment of the spine
and derotation, reducing the rib
prominence.
• Objective data demonstrating
ongoing long-term benefit of this
procedure are lacking.
• Patients who would benefit most
from thoracoplasty because of severe
rib prominence (syndromic patients/
juvenile-onset scoliosis) may
sometimes be unable to tolerate the
procedure because of its effect on
pulmonary function.
T R E A T M E N T OP T I O N S
• Posterior/extrapleural thoracoplasty
• Anterior/internal thoracoplasty
P O S I TI O N I N G PE A R L S
• The patient should be prepared and
draped with wide margins for adequate
visualization of the rib prominence (the
lateral drapes should lie at the posterior
axillary line).
Indications
n
Adolescent/adult scoliosis: Rib prominence is associated with rigid, rotated,
decompensated thoracic and double major curves. In these patients, a convex
thoracoplasty may be necessary if it is not possible to fully derotate the curves
during posterior instrumented spinal fusion. An example would be a rib hump
greater than 4 cm, rib angle greater than 15 degrees, and curve flexibility less
than 50%.
n
Rib hump deformity is a common finding in the three-dimensional evolution of
adolescent idiopathic scoliosis. Albeit a cosmetic concern, rib hump deformity is
a major source of patients’ postoperative dissatisfaction if not corrected to their
expectations. The effect of thoracoplasty on pulmonary function has been a topic
of interest, with varying reports of clinical significance.
n
Rib prominence associated with a compensated curve, where posterior spinal
fusion is not necessary or a previously fused curve is present: the indication may
be poor appearance or discomfort when sitting in a chair or leaning against a wall.
n
To increase flexibility of the curve: concave rib osteotomies and elevation of the
concavity dorsally out of the chest may be present.
n
To procure autologous bone graft for fusion
Examination/Imaging
n
Measurement of angle of thoracic rotation (ATR) by inclinometer
n
Pulmonary function testing
n
Radiographs: full-length posteroanterior, lateral, bending, and Stagnara views
n
Clinical photos of the patient
Surgical Anatomy
n
Ribs/transverse process: parts of the ribs corresponding to vertebrae in the
structural curve are resected.
n
Thoracolumbar fascia
n
Serratus posterior
n
Latissimus dorsi
n
Intercostal neurovascular bundle
n
Pleura
Positioning
n
The patient is positioned prone on a Jackson table in the standard manner for
a posterior spinal fusion. Preparation and draping with wide lateral margins is
advised to better assess and visualize the rib prominence.
226 Procedure 23 | Thoracoplasty for Rib Deformity
P O RTA L S / E X P O S U R ES
P E A R LS
• The fascial plane interval should be
developed properly with minimal blood
loss and trauma to the muscle tissue.
• The incision needs to be carried slightly
distal to the lowest vertebra to be
fused, to allow adequate exposure of
all ribs to be resected.
P O RTA L S / E X P O S U R ES
P I T F A L L S
• Avoid any dissection in the high
thoracic area around the scapula,
because painful scarring may result.
P O RTA L S / E X P O S U R ES
I N S T RU M E N T A T I O N
• Cobb elevators
• Weitlaner retractors
• Rake
• Forceps
• Bovie electrocautery
P O RTA L S / E X P O S U R ES
C O N T RO V E R S IE S
• Alternatively, an incision may be made
directly over the rib prominence, lateral
to the midline, for direct access to the
ribs to be addressed; however, this is
cosmetically undesirable.
Portals/Exposures
n
Single incision technique
• An incision is drawn with a marking pen using the electrocautery cord. The
top of the cord is placed at C7 and the bottom at the midgluteal crease, and
a straight line is drawn down the spine.
• For a selective right thoracic spinal fusion with thoracoplasty, it is necessary
to extend the skin incision distally by 0.5 to 1 inch to retract the thoracolumbar fascia adequately from the midline.
• After skin incision, the spinous processes are outlined and the thoracolumbar
fascia incised.
• The thoracolumbar fascia is picked up with a forceps or retracted with a rake,
and the interval between the paravertebral muscle and fascia is developed
with a combination of sharp and blunt dissection, working laterally (Figure
23-1). The fascia is retracted dorsally and laterally toward the convexity of
the curve over the rib deformity. An assistant is required to hold retractors
for proper visualization.
n
For concave rib osteotomies to increase scoliotic curve flexibility, the steps are
similar.
Procedure
Step 1
n
The ribs that are to be resected are palpated, and a subperiosteal exposure of
the rib, 2 to 3 cm lateral to the transverse process, or as close to the apical
portion of the rib as possible, is started with Bovie electrocautery in its midline
(Figure 23-2).
S T E P 1 P EA R L S
• It is important to pull the periosteum
off the rib and not push as with
ordinary periosteal stripping, to prevent
slipping off the rib inadvertently and
plunging through the pleura.
FIGURE 23-1
FIGURE 23-2