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Файл:Ординатура / Хирургия / Библиотека им академика М.И. Перельмана / Книга_6030_Библиотеки_им_академика_М_И_Перельмана.pdf
A
B
Figure 16–1
(A) Anteroposterior fluoroscopic image of trocar placed into vertebral body. (B)
Anteroposterior fluoroscopic image of unilateral polymethylmethacrylate
(PMMA) with trocar placed in contralateral pedicle for further injection of PMMA.
C
(C) Anteroposterior fluoroscopic image of completed vertebroplasty procedure.
(Courtesy of Kyphon, Inc.; used with permission.)
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A
Figure 16–2
(A) Inflatable balloon tamp (KyphX). (B) Inflatable balloon tamp (KyphX) with
graduated injection device and pressure transducer. (Courtesy of Kyphon, Inc.;
used with permission.)
B
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A B
C
Figure 16–3
(A) Osteoporotic vertebral compression fracture with kyphosis. (B) Inflatable bone tamp placed through working cannula. (C) Inflation of bone tamp with correction of ky-
phus and creation of void. (D) Filling of void with PMMA from anterior to posterior.
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D
A
Figure 16–4
(A) Preoperative lateral x-ray showing contiguous compression fractures at L1 and L2 with resultant kyphosis. Previously treated L3 compression fracture. (B)
Postoperative lateral x-ray showing completion of kyphoplasty procedure with correction of kyphosis. (Courtesy of Dr. Frank Phillips, University of Chicago.)
B
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16 VERTEBROPLASTY AND KYPHOPLASTY
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cations. Kyphoplasty is not recommended for metastatic or hemangiomatous lesions of the spine, but it is indicated in multiple myeloma.
Procedure
The concept of kyphoplasty was developed by Mark Reiley of the Berkeley
Orthopaedic Group in Berkeley, California. The device is an inflatable bone
tamp (Fig. 16–2) that is inserted percutaneously through a cannula, which
is placed into the vertebral body in the same manner as vertebroplasty. The
advantage of this is twofold. First, a void is created in the vertebral body that
can accept PMMA that is of higher viscosity and injected under low pressure. Because the cement is not being forced into the interstices of the
trabecular bone, the risk of leakage is diminished. Second, inflation of the
bone tamp can effect a reduction of the end-plate depression, thereby cor-
recting the deformity. As such, the device can be employed in acute fractures to relieve pain, but also to reduce the deformity and therefore reduce
the risk of pulmonary complications and subsequent fractures.
Positioning of the patient is on well-padded rolls and not on a Kambin
or Wilson frame. The approach to the vertebral body is the same as for
vertebroplasty, percutaneously via the transpedicular or extrapedicular
approach with a Jamshidi needle. Once the Jamshidi needle is appropriately positioned at the junction of the pedicle and body within bone, the
trocar is removed, a guidewire is placed in the hollow core of the needle,
and the Jamshidi needle is removed. A cannulated blunt dissector is then
passed over the guidewire into the vertebral body and then a tract is
created into the vertebral body, directed slightly medial and inferior. The
blunt dissector is left in place, and the working cannula is passed over it, to
become seated just anterior to the posterior cortex. The blunt dissector is
removed, leaving the working cannula in place. The rest of the procedure
is performed through this working cannula.
A 3- or 5-mm hand drill bit is used to cut a path into the anterior half of
the vertebral body, the drill coming to rest a few millimeters posterior to
the anterior cortex. This is performed with frequent imaging to prevent
penetration of the anterior cortex of the vertebral body and injury to the
great vessels. Once the path is cut, the drill bit is removed and small fragments of bone in the path are packed down with the obturator.
Next, the deflated balloon tamp is passed down the working cannula
under image guidance to the end of the path created by the drill. Care is
taken not to pierce the anterior cortex again. There is a guidewire within
the balloon tamp and radiographic marker to facilitate positioning of the
balloon tamp. Once the balloon is positioned, the guidewire is removed,
and gradual filling and inflation of the balloon is undertaken. The balloon
is inflated with sterile saline and radiocontrast dye to monitor the position
of the balloon with frequent (every 0.5 cc) imaging. The liquid is delivered
to the balloon via a flexible cannula connected to a twist syringe with a
pressure transducer to monitor volume and inflation pressure. The end
points for inflation are adequate reduction of the fracture, proximity of balloon to a cortex, or exceeding the recommended filling pressure of the balloon tamp. Various balloon volumes and sizes (15 to 30 mm) are available
to suit the needs of different-sized vertebral bodies. The procedure is repeated on the contralateral side.
Having inflated the tamps bilaterally, reduction of the fracture is accomplished, and a void is left when the balloons are deflated. The balloons
are withdrawn, and PMMA is injected via the working cannula into the defect in the vertebral body. Care must be taken to advance the cement injector to the most anterior portion of the cavity, such that retrograde filling occurs. This provides a more homogeneous cement plug, and forces blood
out the working cannula or veins, avoiding trapping blood anteriorly.
Frequent AP and lateral images are taken. The volume of cement that can
be safely injected is known by the volume that the balloon tamp had been
inflated. Cement injection is stopped when it approaches the posterior cortex, an end plate or lateral wall, or if leakage is seen. The cement applicator
is left in place until the cement is hard to prevent creating a tail upon extraction of the applicator (Fig. 16–3). The techniques may also be used for
the treatment of multiple contiguous fractures to achieve normal sagittal
alignment (Fig. 16–4).
Postoperative management is similar to that for vertebroplasty. No brac-
ing is required.
Complications
Incidence of clinically significant complications is 2.7 %.
Results
1. Average kyphosis reduction—17 degrees
2. Average restoration of anterior body height—45%
3. Good to excellent pain relief—90 to 95 %
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17
Thoracic Pedicle Screws
Pedicular Approach
Archibald H. von Strempel
Goals of Surgical Treatment
To stabilize the thoracic spine; to correct a kyphotic deformity.
Diagnosis
Instability of the thoracic spine can be caused by fracture, tumor, or
spondylodiscitis. Kyphotic deformity can caused by delayed fracture,
Scheuermann’s disease, or other reasons for a hyperkyphotic thoracic
spine. The diagnosis is made by physical findings and a standing anteroposterior (AP) and lateral x-ray of the whole spine completed by a lateral
view of the thoracic spine in supine position with traction (Fig. 17–1).
Indications for Surgery
Thoracic spine instability, painful hyperkyphosis, significant thoracic cosmetic deformity due to hyperkyphosis, thoracic pedicular approach for
bone biopsy of the vertebral body.
Contraindications
1. Children or small adults in whom the pedicle size does not allow
screw placement with a diameter of 5 or 6 mm.
2. Severe osteoporosis.
Advantages
1. No implant contact to neural structures of the spinal canal.
2. High stability; pedicle screw can loaded by three-dimensional correc-
tion forces.
Disadvantages
1. Medial screw misplacement can lead to severe neurologic deficits.
2. Thoracic pedicle diameter (mostly the transverse diameter) can be too
small for 6-mm screws even in normal adults.
Procedure
The patient is placed in a prone position on a frame or pillows with no
pressure on the abdomen. The arms are positioned cranially with anteversion of the shoulders. Lateral C-arm control is helpful, but image quality
can be poor in the upper thoracic area due to ribs and shoulder. The surgeon should be able to do the thoracic pedicular approach even without Carm control. If the following rules are respected, the risk of medial misplacement of the screws is very low. Attention must be given to the correct
entry point of the thoracic pedicle. If the pedicle seems to be too small on
an AP x-ray (pedicle size is limited by transverse diameter), a computed tomography (CT) scan should be done in the levels that are to be instrumented. We do not recommend pedicle screws with an outer diameter less
than 6 mm in adults or adolescents because of the risk of breakage. In the
pediatric population, we recommend 5-mm screws.
The medial wall of the thoracic pedicle is thicker than the lateral, and
the length of the pedicle is shorter compared with the lumbar pedicle.
Even if the transverse pedicle diameter is not much bigger than the screw
diameter, the stability of the inserted screw is sufficient, because a greater
part of the screw is inserted in the thoracic vertebral body compared with
the lumbar situation. In the following technique the screw can cut the thinner lateral wall but not breach the more important medial wall of a pedicle,
which is not much bigger than the screw. With an oblique screw orientation a lateral pedicle fracture can be avoided. If the anatomic conditions do
not allow the implantation of a 6-mm-diameter screw, we recommend the
use of hooks, claws, or wires to fix the internal fixateur to the spine.
Exposure
A midline incision is made one spinous process above the most cranial
vertebra down to the spinous process of the most caudal vertebra. The extensor muscles are dissected laterally to the tips of the transverse
processes. The inferior facet is resected except in the most cranial vertebra,
where the capsule is excised only (Fig. 17–2). The lateral border of the superior facet is identified with a probe. A parallel line of the lateral border of
the superior facet corresponds to the y-axis of the entry point to the
pedicle. The transverse process is divided in three horizontal parts. A parallel line between the middle and the cranial third of the transverse
process corresponds to the x-axis. The intersection of both axes does not
correspond to the center of the pedicle but to the lateral border of the oval
pedicle and it is more lateral than the entry point for the Roy-Camille technique (Fig. 17–3A-C). We open the cortex over this point with a Perthes
awl, which is directed in the horizontal plane 20 to 25 degrees from lateral
to medial and 5 to 10 degrees in the sagittal plane from cranial to caudal. If
a lateral C-arm control is available, we find the ideal direction in the sagittal plane on the C-arm view.We prepare the screw hole with a 3.2-mm drill,
which is used speedless or at very low speed pushing the drill machine up
and down carefully. A penetration of the anterior cortex has to be strictly
avoided. Another option is to prepare the screw hole with a probe. The
length of the screw is measured with a depth gauge. With a 3-mm ball-tip
probe, the integrity of the interior pedicle wall is evaluated for penetration.
At this stage the screw position may be confirmed by placing a Kirschner wire into the pedicle canal and checking the orientation with AP
and lateral x-rays. If the desired screw length falls between two available
screws, we implant the shorter one. In hard sclerotic bone, we prepare
threads with a tap diameter 6 mm to the appropriate depths.
In some individuals the transverse processes have a special shape like a
bow so that the tips of the transverse processes are orientated toward the
posterior. In such a case the entry point would be too distorted and positioned posteriorly, and the way for the screw would be longer, requiring
greater precision regarding the entry point and direction of the screw axis
(Fig 17–3D). The risk of misplacement increases with the need for increased precision. To make it easier, a distal part of the transverse process
is resected away, allowing the entry point to be closer to the level of the surface of the superior facet.
The 12th thoracic vertebra often has variations of the facet joints and
the transverse processes. Often the transverse processes are short and the
facet joint is typically thoracic-oriented coronary. In a situation with a
more lumbar type of facet joint sagittally oriented, we follow the rules of
screw placement in lumbar pedicles. If the 12th thoracic vertebra shows
both variations—on one side a thoracic and on the other side a lumbar type
of facet joint—lateral C-arm control or a preoperative CT scan must be used
for correct placement.
We do not use different entry points and axes between the upper,
middle, and lower thoracic spine even if the coronal shape of the pedicle
changes from round to oval because the recommended technique minimizes potential misplacement for the entire thoracic spine (T1-T12). Only
low-profile screw-rod systems should be used in the thoracic spine to
avoid soft tissue problems such as pain or wound healing disturbance. We
prefer a hinged type of pedicle screw with a hinge between the screw head
and the shaft of the screw above the site where peak stresses and failures
typically occur in rigid rod screw constructs (Fig. 17–4). This reduces
stress shielding and facilitates the screw-rod connection.
Before an attempt is made to reposition the thoracic spine, posterior,
anterior, or combined releases have to be completed, if necessary. A bony
defect in the anterior column needs to be reconstructed.
A posterolateral spondylodesis is performed (Fig. 17–5), in cases with
anterior reconstruction of the anterior column or anterior release together
with an anterior spondylodesis.
Pitfalls
1. The 12th thoracic vertebra often is a transitional vertebra with ana-
tomic variations. Careful x-ray examination is necessary and a CT scan
can be indicated when anomalies are recognized like facet joint alteration, stump ribs, unilateral rib, etc.
2. The correct horizontal axis of the position of the pedicle screw (20 to
25 degrees) is important to avoid causing a fracture of the lateral wall of
the pedicle. In a rotated vertebra the establishment of the correct axis is
more difficult. At the apex of a structural scoliosis, rotation and torsion
of the vertebra can increase the difficulties further because the pedicle
by itself can be altered.
Complications
1. The uppermost and lowermost screws can break out when the correc-
tion of a rigid kyphotic deformity is attempted. Posterior release (Vshaped interlaminotomy with complete resection of the lower facets)
and/or anterior release (discectomy) should be done before the correction is attempted.
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A
Figure 17–1
Preoperative standing anteroposterior (AP) (A) and lateral (B) x-rays showing Scheuermann’s disease. (C) Preoperative radiograph of the hypomochlion view showing
Scheuermann’s disease.
BC
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t
Excise
Pedicle
X
Y
Entry
point
capsule
only
Resect
inferior
facet
1
Pedicle
Screw axis
2
3
4
5
6
7
8
9
10
11
Resect
inferior
facet
30°
A
B
Superior facet
Screw axis
5° –10°
C
Pedicle
axis
T12
Figure 17–2
Intraoperative situs after detachment of the extensor muscles.
Portion of
ransverse
process
resected
D
Figure 17–3
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SECTION II THE THORACIC SPINE
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(A–D) Four drawings showing entry point and axis for screw placement.
Figure 17–4
2
3
4
5
6
7
8
9
10
11
T12
T1
T2
Photograph of a hinged-type pedicle screw, the Segmental Spinal Correction System
(SSCS). (Courtesy of Ulrich Company, Ulm, Germany, with permission.)
A B
Figure 17–6
Postoperative standing AP (A) and lateral (B) x-rays of the spine showing correction and
stabilization of a Scheuermann’s hyperkyphosis.
Eurostile
Figure 17–5
Posterolateral spondylodesis.
17 THORACIC PEDICLE SCREWS
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