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Файл:Ординатура / Хирургия / Библиотека им академика М.И. Перельмана / Книга_6030_Библиотеки_им_академика_М_И_Перельмана.pdf
Anterior Correction of Thoracic Scoliosis
29
Using the Kaneda Anterior Scoliosis System
(KASS)
Kiyoshi Kaneda and Yasuhiro Shono
Goals of Surgical Treatment
To obtain three-dimensional correction of the thoracic scoliosis and a well-
balanced spine.
Diagnosis
Thoracic scoliosis is defined as scoliosis with its apex of the major curve
located within the T2 to T11-T12 disc levels. Standing posteroanterior (PA)
and lateral x-ray films are utilized to determine the magnitude of the curvatures and spinal balance (Fig. 29–1). Physical examinations to clarify waist
asymmetry, bilateral shoulder height asymmetry, and rib hump deformity
are performed. Flexibility of the curvature is determined by preoperative
bending films and traction x-ray films.
Indications for Surgery
1. Single thoracic curve (King type III and IV curves) is best indicated for
this procedure.
2. Curve magnitude more than 50 degrees.
3. Adult patients with severe thoracic scoliosis.
Contraindications
1. Single anterior correction surgery is not indicated for patient with
double major curve pattern (King type I and true type II curves).
However, false double major curve (type II curve with flexible and
small lumbar curve) can be treated by selective major thoracic curve
correction.
2. Scoliosis with structural high thoracic curve (type V, etc.)
Advantages of Anterior Approach for Thoracic Scoliosis
1. Short fusion
2. Three-dimensional correction of the deformity
3. Improved cosmesis and rib hump
4. Avoids intervention to the back muscles of the spine
5. No skin protrusion caused by implants as seen in the posterior instrumentation procedure
Disadvantages
1. Spinal balance decompensation in a false double major curve (type II)
2. Shoulder height asymmetry with a structural high thoracic curve
3. The associated morbidity of a thoracotomy
Procedure
Positioning of the Patient
1. The patient is positioned on the flat table with the convexity of the
curve up (lateral decubitus position).
2. The head is placed on a pillow with the cervical spine straight.
3. An axillary pad is placed to prevent circulatory disturbance of the
upper extremity.
4. A pillow is placed to secure the space between the fibula head and
table to prevent pressure on the peroneal nerve.
5. The scapula and arm elevated and secured proximally.
Skin Incision
1. Skin incision is made along the rib of the uppermost vertebra or one
above it where instrumentation is planned. In thoracic scoliosis, this is
usually the fifth, sixth, or seventh rib.
2. To avoid skin incision crossing the breast, a skin incision is placed obliquely from the angle of the rib to be resected, posteriorly to the costal
cartilage of the 10th or 11th rib, anteriorly. This incision allows exposure of the vertebra as distal as T10 or T11.
3. To approach T12 or more distally located vertebrae, additional entry
site needs to be prepared. Usually, an additional entry site is placed on
the 10th or 11th rib. No additional skin incision is required, because
the 10th or 11th rib can be approached subcutaneously.
4. Through this site, lower thoracic and, by posterior partial transection
of the diaphragm and through the retroperitoneal approach, upper
lumbar vertebrae can be accessed.
Exposure
1. The serratus anterior and latissimus dorsi muscles are transected in a
plane parallel to the course of the rib to be transected. A cuff of serratus
muscle is left on the lower pole of the scapula to facilitate its reattachment when the wound is closed and stay sutures should be placed on
the cut edges of the muscles attached to the scapula for latter reattachment.
2. The scapula is displaced superiorly and rotated to expose the underlying rib.
3. The rib periosteum is incised, and stripped subperiosteally from the
rib. The rib is cut as far posteriorly as possible. The anterior portion of
the rib is resected 3 to 5 cm distal to the costochondral junction.
4. The pleura is incised at the bed of the resected rib superiorly and distally for the length of the wound to gain access to the thoracic cavity. A
retractor is used to open and hold the ribs apart during surgery.
5. The segmental vessels are identified and ligated at the levels where instrumentation is planned.
6. The intervertebral discs and the intervening cartilage plates located
among the fusion range are removed. In a stiff, large thoracic curve,
mobilization requires resection of the entire annulus to the opposite
concave side.
7. Following discectomy, the rib heads and the associated ligamentcapsular structures of the rib head joints located among the fusion
range are resected to achieve effective destabilization of the rigid deformity and to obtain maximum three-dimensional correction (Fig. 29–
2).
Instrumentation and Correction
1. The vertebral plate with tetraspikes is tapped into the lateral portion of
the each vertebra where instrumentation is planned. The vertebral
plate must be positioned straight laterally on the vertebral body to prevent misdirected screw insertion.
2. Instrumentation can be applied to the thoracic vertebrae as proximal as
T5 (in some cases T4). In general, proximal vertebral bodies (T5, T6,
and T7) are anatomically small in size. Also, young children usually
have small vertebrae. In these situations, it is difficult to insert two
screws into one vertebral body. Thus, the authors use a single-hole
plate and single rod-screw fixation at proximal vertebrae and two-rod
fixation at distal segments in these situations.
3. The vertebral screws are inserted into the vertebral bodies through the
screw holes of the plate. The screw holes are designed to control the
vertebral screw insertion direction.
4. An awl is used to penetrate the near cortex and establish a path for the
tap.
5. The tap is designed with a long threaded section. This feature allows
reliable penetration of the opposite cortex because the near cortex remains in the threaded section of the tap shaft. It is extremely important
to check the tip of the tap penetrating the contralateral cortex of the
vertebral body by touching the tip with the surgeon’s finger. An integrated depth gauge provides accurate measurement for screw length
determination.
6. Either the open or closed screw (6.25-mm diameter) is inserted into the
staple holes so that it is securely seated and the tip can be palpated
with the surgeon’s finger on the opposite side of the vertebral body. It is
very important to engage the far cortex to provide bicortical fixation. It
is equally important that the screw heads line up so that the rod may be
more easily introduced into them.
7. We use the vertebral screws, which are available in 2.5-mm increments
in length, to obtain optimum screw tip penetration. In addition, the
screw has a blunt tip, which can be safely placed near the vascular
structures. Furthermore, owing to increased cortical fixation area, the
fixation strength of the blunt-tip screw is enhanced when compared
with a conventional sharp-tip screw.
8. The anterior screw should be inserted parallel to the posterior border
of the vertebral body and the posterior screw in a slight anterior direction, which prevents penetration of the screw into the spinal canal.
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SECTION II THE THORACIC SPINE
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Figure 29–1
Preoperative standing posteroanterior (PA) and lateral x-rays of
the type IV thoracic scoliosis patient. (A) The standing preoperative PAradiograph shows a thoracic curve of 68 degrees from T5 to
L1 with a compensatory left upper thoracic curve of 40 degrees.
(B) The standing lateral radiograph shows lordotic deformity of 2
degrees.
Eurostile
29 KANEDA ANTERIOR SCOLIOSIS SYSTEM (KASS)
141
■
T6
T7
T5
T8
T4
Plates and
discs removed
Eso
Ao
Figure 29–2
The intervertebral discs and the intervening cartilage plates located among the fusion area are removed. To achieve effective destabilization of the rigid thoracic
deformity, the rib head joints and the associated ligament-capsular structures are
resected. Before (A) and after (B) resection of the intervertebral disc and the rib
head joints (indicated by arrows).
T9
T10
T11
T12
T6
T7
T8
T5
Anterior and posterior screws
engage opposite
cortex
T9
T10
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142
T11
T12
L1
SECTION II THE THORACIC SPINE
Eurostile
Figure 29–3
After completion of the scoliosis correction with the Kaneda anterior scoliosis system (KASS). A combined configuration
(combined one-rod and two-rod fixation) is demonstrated.
Eurostile
Figure 29–4
Follow-up radiographs show the instrumentation placed from T5 to L1 (singlescrew fixation at T5-T7 and two-screw fixation at T8-L1; combined configuration) (A). The thoracic scoliosis was corrected to 24 degrees, and the upper
thoracic compensatory curve corrected spontaneously to 27 degrees with wellbalanced spine. (B) In the lateral radiograph, lordotic deformity was corrected
to 12 degrees of kyphosis.
29 KANEDA ANTERIOR SCOLIOSIS SYSTEM (KASS)
143
■
These screw insertion angles provide strong biomechanical stability.
Generally, closed screws should be placed at the end vertebrae of the
fusion and open screws in the vertebrae between the top and bottom of
the fusion.
9. Prior to inserting the rod, bone chips obtained from the resected rib are
grafted into the intervertebral disc spaces.
10. The rod (4.75-mm diameter; smooth surface) is cut to a suitable length
to span the screws in the curve. If the curve is relatively mild and flexible, the rod is contoured close to the physiologic sagittal curvature.
But if the curve is severe and rigid, the rod should be contoured to partially adapt to the scoliotic curvature. This will be necessary to allow
rod insertion.
11. Once the first rod is contoured, it is inserted into either of the end
closed screws first, then dropped into the open screws, and finally into
the remaining end closed screw.
12. If there is difficulty while trying to insert the rod into any of the open
screws, the rod introducer is used to push the rod down into the openheaded screw. A cap is slid as far as possible onto the open screw head.
13. The screw heads are tightened temporarily; a pair of the special rod
benders is used to bend the first rod in situ. This produces increased
kyphosis, restoring a more physiologic sagittal alignment. These
special benders were specifically designed to be placed over the screw
heads, thereby minimizing the angulatory forces that might loosen the
screws during the rod-bending process.
14. Once the rod has been placed in its final position, the large compressor
is placed between the screws around the first rod located near the apical vertebra or disc. The set screws are released and compression force
is applied between the screws. The remaining vertebrae are also compressed. This is done sequentially by starting with the interior screws
first and then working out toward the end vertebrae screws. The
screws are protected from slipping on the rod by using the rod holder.
Compressive force is applied between the rod holder, which is placed
on the far side of the previously secured screw. Providing the compression force against the rod holder instead of the previously tightened
screw head lessens the risk of screw loosening. As the screws are compressed together, the set screws are tightened. Compression force application not only corrects the scoliosis but also tends to produce more
kyphosis.
15. After the first rod application and correction procedure, the second
rod is introduced in the same manner as the first rod. The first rod
should be inserted with little effort as the deformity has already been
corrected by the first rod.
16. Compression force is applied to the second rod in the same manner as
the first rod. In most cases, the first rod can be regarded as the correcting rod and the second rod as the fixation or stabilizing rod.
17. After the correction procedure is completed, the excessive portion of
the rods beyond the end screws of the construct should be cut with a
rod cutter.
18. Final inspection of the construct includes rechecking each set screw
for secure tightening using the true torque wrench. A final view of the
Kaneda anterior scoliosis system (KASS) is shown in Figure 29–3. Follow-up PA and lateral x-rays are shown in Figure 29–4.
Closing Procedure
1. After completion of the instrumentation procedure, implants are
covered by a Teflon sheet to avoid direct contact of the metal to the
lung.
2. A chest suction tube is inserted. Bleeding from the discectomy spaces
is controlled with fibrin gel.
3. Routine closure of the chest, muscles, and skin completes the procedure.
Pitfalls and Complications
1. Surgeons must recognize the rotational deformity of the thoracic
scoliosis, and the vertebral plates must be positioned straight laterally
on the vertebral body to prevent misdirected screw insertion.
2. The anterior vertebral screw is inserted parallel to the posterior vertebral body line in the transverse plane, and the posterior vertebral screw
is inserted 10 to 15 degrees obliquely to the posterior vertebral body
line pointing anteriorly to prevent screw insertion into the spinal
canal.
3. Bicortical fixation is essential to obtain maximum fixation strength of
the vertebral screws. To confirm this, the tip of the screw is palpated
with the surgeon’s finger on the opposite side of the vertebral body.
This also prevents excessive screw tip penetration.
4. Beware of proximal screw pullout when single screw-rod fixation is
employed. Resection of the entire annulus to the opposite concave side
should be performed to effectively mobilize the proximal thoracic
vertebrae. Well-mobilized vertebrae prevent screw pullout during correction force application.
Postoperative Care
1. Chest x-rays until the chest tube is removed (drainage less than 80
cc/day).
2. Patients are allowed to ambulate the next day.
3. If spinal balance is not satisfactory after surgery, a brace is used for
about 5 months.
Suggested Readings
Kaneda K, Shono Y. Kaneda anterior multisegmental instrumentation:
two-rod system for the treatment of thoracolumbar and lumbar scoliotic curvatures. In: Bridwell KH, DeWald RL, eds. The Textbook of Spinal Surgery. 2nd ed. Philadelphia: Lippincott-Raven; 1997:641–663.
Kaneda K, Shono Y, Satoh S, Abumi K. Anterior correction of thoracic
scoliosis with Kaneda anterior spinal system: a preliminary report.
Spine 1997;22:1358–1368.
Kaneda K, Shono Y, Satoh S, Abumi K. New anterior instrumentation for
the management of thoracolumbar and lumbar scoliosis: application of
the Kaneda two-rod system. Spine 1996;21:1250–1261.
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SECTION II THE THORACIC SPINE
Eurostile
Posterior Scoliosis Correction of
30
King II Curves
Hooks and Rods
Lawrence G. Lenke
Goals of Surgical Treatment
To balance, correct, and stabilize the curvature.
Diagnosis
True King II curve identification:
1. The King II curve is one where both thoracic and lumbar curves cross
the midline, with the thoracic Cobb greater than the lumbar Cobb and
the percent thoracic side bending being less than the percent lumbar
side bending correction. It is now well known that a thoracolumbar
junctional kyphosis (T10-L2 sagittal Cobb of greater than or equal to
+20 degrees) is a relative contraindication to a selective thoracic fusion
because one must stop near or at the apex of the sagittal plane
malalignment.
2. I found that a selective thoracic fusion can be performed when the
thoracic to lumbar (T:L) Cobb and AVTratios were greater than 1.2, and
the T:L AVR was greater than 1.0. In addition, there had to be an absence of any thoracolumbar junctional kyphosis, and a maximum lumbar Cobb measurement of 60 degrees on the upright film.
3. For a true King II curve definition, I feel the lumbar apex should
completely deviate from a vertically oriented center sacral line (as designated a Lenke type C lumbar modifier).
Selection of Fusion Levels
In a true King II curve treated with posterior hook-rod instrumentation, fusion levels normally extend from the neutral vertebra proximally (T4 or
T5) to the stable vertebra distally at the thoracolumbar junction (usually
T12 or L1).
The proximal thoracic region should also be evaluated in the coronal
and sagittal planes as well as clinically for a structural proximal thoracic
curve. If this is noted, then the instrumentation proximally should extend
up to T2 or T3 for inclusion of the structural proximal thoracic curve. It is
important to determine the stable vertebra off a vertically oriented center
sacral line that does not have any accommodation for mild pelvic obliquity.
When pelvic obliquity is greater than 2 cm, the radiograph should be per-
formed with an appropriate shoe lift under the short leg to level the pelvis.
The stable vertebra is the most proximal lower thoracic or upper lumbar
vertebra most closely bisected by this vertically oriented center sacral line
(CSVL). For most true King II curves, the stable vertebra is either T12 or L1.
If the T12-L1 disc is the “stable” segment, then I prefer to end the instrumentation at T12 as long as there is absolutely no thoracolumbar junctional
kyphosis. If there is any hint of thoracolumbar junctional kyphosis or in a
larger thoracic curve (쏜 70 degrees), I would recommend extending the instrumentation and fusion to L1 instead when using hooks.
Instrumentation Techniques
Following adequate subperiosteal exposure out to the tips of the transverse
processes of the intended vertebra to be fused, appropriate inferior facet
joint osteotomies for hook placement and fusion purposes is performed.
Hooks are then placed (assuming a T4-T12 instrumentation construct). The
left-sided concave hook pattern will normally begin proximal with a oneor two-level pedicle-transverse process (or supralaminar) claw of T4 or T4T5. Another up-going pedicle hook is placed two levels below the upper
most pedicle hook usually at T6, and then a down-going supralaminar
hook is placed three levels above the lowest instrumented vertebra (LIV), at
T9. A two-level supralaminar-infralaminar claw at T11-T12 completes the
concave hook pattern.
The right-sided hook pattern begins with a two-level pedicle-transverse
process claw at T4-T5, two up-going pedicle hooks at T7 and T9, and then a
supralaminar hook at the LIV (T12) (Fig. 30–1). The left-sided concave rod
is placed first. It is contoured to the appropriate coronal and sagittal
planes, engaged in the hooks proximally and cantilevered into the hooks
successively from proximal to distal. Hooks are seated from distal to proximal with the distal compression claw seated first, apical supralaminar
hook seated second, the apical pedicle hook third, and the proximal
pedicle claw last. Thus, compression forces are performed across the
thoracolumbar junction ensuring appropriate lordotic contour of the thora-
columbar junction, prior to any distraction forces at the apex and above.
Mild translational forces can be applied with in situ rod benders to further
correct the scoliosis.
Next, the right or convex rod is placed with hooks being seated proximally first at the upper level claw and proceeding distally down to the supralaminar hook placed at the LIV. Thus, compression forces are placed
from the apical pedicle hooks to the upper claw over the convexity of the
convex spine, then a distraction force is directed against the relative concavity of the lower right-sided thoracic spine. These forces are directly opposite to those that have been placed on the left-sided concave spine, as
one would expect.
It is unwise to perform a full 90-degree rod rotation maneuver on a true
King II curve for this has been shown to produce a high rate of lumbar
curve decompensation. Theories about this problem abound, with the
most logical being simple overcorrection of the thoracic curve beyond
what the lumbar curve can accommodate. In addition, torque/detorque
forces may be transferred from the thoracic spine into the lumbar spine
with this rod rotation maneuver. Efforts should be made to maintain an appropriate amount of tilt to the LIV such that it is not horizontalized. From
my experience, the degree of horizontalization of the LIV in a true King II
curve treated posteriorly directly correlates with the amount of coronal imbalance to the left produced by the instrumentation techniques. Thus, one
should always strive to maintain an appropriate amount of LIV tilt based
on the initial degree of both thoracic and lumbar Cobb magnitudes and the
preoperative LIV tilt. A safe level of LIV horizontalization is approximately
50% of the original value. In addition, one must limit the thoracic curve
correction to approximately 40 % of the original measurement to allow the
lumbar curve to spontaneously correct to that (Fig. 30–2). Because thoracic
curve correction is often limited, consideration for a convex thoracoplasty
may improve cosmetic correction of unacceptable thoracic rib humps.
We do perform intraoperative short cassette x-rays assessing the degree
of correction obtained on the thoracic curves. Our operative goal is to make
sure that the LIV has not been excessively horizontalized as a direct reflection of excessive main thoracic curve correction. In addition, one must be
careful not to contour in situ the lower thoracic region excessively, while
limiting apical thoracic curve correction as this can again excessively horizontalize the LIV and become detrimental on the lumbar curve spontaneous response (Fig. 30–3).
Conclusions
The proper selection and operative treatment of a true King II curve can
prove difficult. The surgeon must pay strict attention to the proper selection of a true King II curve pattern and the application of posterior instrumentation techniques that will provide adequate thoracic correction
without overcorrection. This will then allow appropriate spontaneous
lumbar curve correction and maintenance of overall spinal balance. Utilizing these techniques, successful instrumentation and fusion of a true King
II curve may be accomplished with posterior segmental hook-rod systems.
Suggested Readings
Bernhardt M, Bridwell K. Segmental analysis of the sagittal plane align-
ment of the normal thoracic and lumbar spines and thoracolumbar
junction. Spine 1989;14:717–721.
Bridwell KH, Betz RR, Capelli AM, Huss G, Harvey C. Sagittal plane analy-
sis in idiopathic scoliosis patients treated with Cotrel-Dubousset instrumentation. Spine 1990;15:921–926.
Bridwell KH, McAllister J, Betz RR, Huss G, Clancy M, Schoenecker PL.
Coronal decompensation produced by Cotrel-Dubousset “derotation”
maneuver for idiopathic right thoracic scoliosis. Spine 1991;16:769–
777.
Cotrel Y, Dubousset J, Guillaumat M. New universal instrumentation in
spinal surgery. Clin Orthop 1988;227:10–23.
Dubousset J, Cotrel Y. Application technique of Cotrel-Dubousset instru-
mentation for scoliosis deformities. Clin Orthop 1991;264:103–110.
Gray JM, Smith BW, Ashley RK, LaGrone MO, Mall J. Derotational analysis
of Cotrel-Dubousset instrumentation in idiopathic scoliosis. Spine
1991;16(suppl 8):S391−S393.
Eurostile
30 POSTERIOR SCOLIOSIS CORRECTION OF KING II CURVES
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AB C
Figure 30−1
(A) A.T. is a 12-year, 3-month-old girl with a true King II adolescent idiopathic scoliosis. Her upright posteroanterior (PA) long cassette radiograph demonstrates a 57-degree right thoracic, 38-degree left lumbar
scoliosis. Her lumbar spine modifier is type C because the vertically directed CSVL falls completely medial to the apex of the lumbar curve (L2 body). (B) Long cassette lateral radiograph demonstrates her normalized thoracic kyphosis and lumbar lordosis without any thoracolumbar junctional kyphosis. (C) Side
D
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SECTION II THE THORACIC SPINE
Eurostile
bending correction to the right demonstrates thoracic correction to 41 degrees. (D) Side bending correction to the left demonstrates correction of the lumbar curve to 18 degrees.
Figure 30−1 (continued)
(E) She underwent a posterior instrumentation and fusion
with a segmental hook-rod system from T4 to T12. Hook pattern includes a proximal concave pedicle-transverse
process claw at T4, apical pedicle hook at T6, apical supralaminar hook at T9, and distal supralaminar-infralami-
nar claw at T11-T12. The convex rod includes a pedicletransverse process claw at T4, two apical pedicle hooks, and
a distal lowest instrumented vertebra (LIV) supralaminar
hook at T12. The left-sided (concave) hooks are seated
beginning distally (T12) and working proximally to T4. The
right (convex) hooks are seated from proximal (T4) to distal
(T12). Thoracic coronal correction was limited to 32
degrees, with spontaneous lumbar curve correction to 21
degrees at 2 years postoperative. The lumbar curve is now in
a type B position following the spontaneous correction. (F)
The 2-year postoperative lateral x-ray demonstrates adequate sagittal alignment without a junctional kyphosis. (G)
A preoperative standing photograph demonstrates the right
thoracic deformity without any significant lumbar deform-
ity. (H) A 2-year postoperative standing photograph demonstrates the normalized cosmetic alignment, level shoulders
and pelvis, and absence of any trunk shift.
EF
G
Eurostile
30 POSTERIOR SCOLIOSIS CORRECTION OF KING II CURVES
H
147
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Figure 30–2
(A) H.S. is a 13-year, 11-month-old girl with a 61degrees thoracic, 45-degree lumbar type II idiopathic
scoliosis. Although if one critically examines the relationship between the CSVL and the apex of the lumbar
spine (L2-L3 disc vs. L3 body), this line just touches the
medial aspect of the apical body or bodies. Thus, this is
a really a type B lumbar modifier. (B) The preoperative
lateral radiograph demonstrates thoracic hypokyphosis (T5-T12 = +10 degrees) with an absence of any
thoracolumbar junctional kyphosis. (C) Right-side
bending x-ray demonstrates correction of the main
thoracic curve to 16 degrees. (D) Left-side bending xray demonstrates correction of the left lumbar curve to
7 degrees.
A
B
C D
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SECTION II THE THORACIC SPINE
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Figure 30–2 (continued)
(E) The 3-year postoperative coronal x-ray demonstrates correction of the thoracic curve to 29 degrees,
and spontaneous correction of the lumbar curve to 31
degrees. The instrumentation and fusion extended
from T5 to L1. The construct included a left-sided
pedicle-transverse process claw at T5 (seated second)
and a T12-L1 supralaminar-infralaminar claw (seated
first). Apical Wisconsin wires were then used for mild
translational correction of the thoracic apex from T7-
T11. The right-sided construct included a T5 pedicle-
transverse process claw, apical pedicle hooks at T7 and
T10, and the L1 supralaminar hook. These were seated
from proximal (T5) to distal (L1). Coronal correction
has been limited purposely to accommodate the lumbar curve below. Adequate postoperative coronal
balance is noted at the 3-year posterior follow-up. (F)
Long cassette lateral radiograph at 3 years postoperative demonstrates normalized sagittal alignment
without any thoracolumbar kyphosis.
E
F
Eurostile
30 POSTERIOR SCOLIOSIS CORRECTION OF KING II CURVES
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