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18 Anterior Spinal Column Augmentation Techniques
There does seem to be a trend toward early intervention showing that patients treated less than
7 weeks after their fracture event do better from a
pain standpoint than those treated later [27].
Patients who are hospitalized for pain control do
benefit from early vertebral augmentation. This
results in shortened hospitalization, fewer readmissions, and lower overall costs [28].
Preoperative Considerations
When planning the procedure, the following factors must be taken into account: the size of the
vertebral body, the size of the pedicle, if transpedicular or parapedicular approaches will be used,
if KP or VP is desired, and if unilateral or bilateral needle placement is the chosen technique. A
wide vertebral body with a severe compression
deformity and wide pedicles may dictate a bilateral approach to restore height and ensure there is
enough volume of PMMA to reach both sides
equally. However, in the smaller vertebral body
where fracture height restoration is of less interest, a unilateral approach may be sufficient.
Two pedicle approaches are used.
Transpedicular is used whenever possible dictated by pedicle diameter. In patients with
diameters <4 mm, a parapedicular approach
may be used. In this technique, the cannula
enters the bone, exits along the lateral edge of
the pedicle, and reenters the vertebral body.
This is possible in the thoracic spine where the
rib shields any neurovascular structure. Pedicles
in the high to mid-thoracic spine may be small
and severely angled making the parapedicular
approach the more viable option. The differing
trajectories for transpedicular and parapedicular are shown in Fig. 18.3. Vertebroplasty at our
institution is almost always performed from a
unilateral approach. Preoperative trajectories
should avoid the neuroforamina starting high
on the pedicle with a slightly inferior and
medial trajectory, planning length, and angles
of approach.
Due to longer procedural time, at our institution, kyphoplasty is reserved to single-level deformity or disease in younger patients where the
level of deformity is believed to cause progression
of deformity in the future and where fracture
reduction is believed to have a reasonable chance
of being accomplished. Vertebroplasty is done
over multiple levels due to its speed in older
patients where the goal is pain control and maintaining fracture stability without reduction.
Surgical Technique
Vertebroplasty
This procedure is performed under conscious
sedation or general anesthesia and should be
done in a facility with spine surgery capabilities.
Biplanar fluoroscopy is essential and can be done
either in the interventional suite or the operating
room. It can be done with single C-arm alternating between lateral and AP pictures or by using
Fig. 18.3 Trajectories showing parapedicular and transpedicular approaches
I.K. White et al.
Fig. 18.4 Showing patient positioning with standard C-arm positioning and two C-arms allowing for biplanar fluoroscopy. This same setup can be done in the interventional suite
dual arms which speed the procedure, especially
when treating multiple levels.
The patient is positioned prone on a radiolucent operating table, and the face and pressure
points are padded as well as the elbows and axilla
to prevent brachial plexus and ulnar injuries
(Fig. 18.4). We have not found a Foley catheter
necessary. Although general anesthesia is not
necessary, trained personnel should administer
the conscious sedation, and vital signs should be
continually monitored. The patient is then
prepped and draped sterilely.
Based on preoperative images, the parapedicular or transpedicular approach is selected. The
level of interest is then localized using fluoroscopy, placing the initial mark on the skin just lateral to the superior lateral border of the pedicle of
interest on the AP image when using transpedicular trajectory (Fig. 18.5). When using the parapedicular trajectory, the skin incision should be
made 7–11 cm off of midline to allow for a more
medial trajectory. The cranial/caudal trajectory
should be the same as transpedicular. The skin is
injected with 1% lidocaine with 1:200,000 epinephrine or 0.5% Marcaine with 1:200,000
epinephrine down to the pedicle making sure to
inject the periosteum. A 2 mm incision is then
made either with an 11 blade or 15 blade knife
and a No. 11 Jamshidi biopsy needle with trocar
in place. Fluoroscopy can be used to plan the
ideal trajectory. If using the transpedicular
approach, the needle is advanced to the bone and
located at the superior lateral aspect of the pedicle. Alternating between AP and lateral views,
the course of the needle should follow the trajectory of the pedicle with slight triangulation ending up in the anterior half of the vertebral body.
The needle should be advanced in 1–2 mm increments. When using the transpedicular approach,
this is usually done bilaterally as the PMMA
has difficulty reaching the contralateral aspect of
the body.
When using the parapedicular approach, the
cannula is initially located on the transverse process. The junction of the transverse process and
the facet is felt, and the Jamshidi needle is walked
inferiorly until it falls off the inferior edge of the
transverse process. The entry point is at the lateral vertebral body, immediately caudal to the
transverse process, and at the lateral junction of
the pedicle on the AP fluoroscopy. From this
entry point, the goal is to reach the middle of the
body on the AP while reaching the anterior half
of the vertebral body. It should be noted that the
parapedicular approach theoretically increases
the patient’s risk for pneumothorax in thoracic
cases. The location of the needle for unilateral
approaches is important as the amount of cement
able to be infused into the body is proportional up
to a point in pain reduction, and poor needle
18 Anterior Spinal Column Augmentation Techniques
Fig. 18.5 Choosing entry point on transpedicular and
parapedicular trajectories on the AP radiograph. Notice
the lateral starting point approximately 7–11 cm off of
placement can reduce the amount of cement that
is able to be symmetrically injected [27].
The surgeon should practice safety from
excessive radiation by using a clamp or lead
gloves to shield their hands. If multiple levels are
going to be done, it is preferred to place all
needles before cement injections. It used to be
common practice before cement injection to
inject a small amount of contrast to visualize the
venous channels present; however, this practice
has not been proven to have clinical utility [29].
Before injecting the bone cement, the operator
should check the needle to make sure it is deemed
to be in a suitable position. If the needle position
is deemed to be non-ideal, there is the option of
either replacing the needle or a curved inner cannula can be used to deliver bone cement throughout the entirety of the vertebral body.
There are several cement products on the market with differing properties; however, for the
majority of cases, PMMA is the bone cement of
choice. In commercial kits, it comes as two parts
(a methyl-methacrylate polymer powder and a
midline at the level of the pedicle for the parapedicular,
whereas the transpedicular is 1 cm off the superolateral
border of the pedicle of interest
liquid monomer), and, once mixing occurs, the
components begin polymerization. A radio-dense
material such as barium is added to aid visualization. The PMMA is mixed for 3–5 min until it is
the consistency of hair conditioner and loaded
into a 10 cc syringe. The cement for vertebroplasty is slightly less thick than that for kyphoplasty, which is more similar to the consistency
of toothpaste. During the hardening process,
PMMA undergoes an exothermic reaction which
may be responsible for some of the pain relief
experienced from the procedure. After the cement
is deemed to be at the appropriate consistency,
the injection tool is connected to the needle.
There are a number of devices now available, but
and have an attachment at the base for the needle
and for the syringe. The cement is then injected
under steady pressure. In the lumbar spine, usually 5–10 cc can be injected safely with decreasing amounts for severe fracture patterns and
fractures higher in the thoracic spine. During
injection, care must be taken not to let cement
I.K. White et al.
Fig. 18.6 After needle is placed, complications can arise with extravasation of cement into large draining veins, along
the body into the foramen, into the spinal canal, and out the fracture site into the paravertebral soft tissues
extravasation course beyond the borders of the
body. Anteroposterior and lateral images should
be taken to assess that the cement remains within
the borders of the body. The spinal canal should
be critically evaluated as cement extrusion into
the spinal canals should be avoided. Complications
related to extravasation are shown in Fig. 18.6.
After the cement is injected and the surgeon
satisfied with the amount injected and the fluoroscopic picture, the injection device is removed,
and the inner cannula of the Jamshidi needle
replaced. This needs to be maintained until the
cement has completely hardened as polymerization causes volume expansion of the PMMA
which can back up into the needle. After the
PMMA is hardened, the Jamshidi needle is
removed by twisting motion, and each incision
can be closed with a monofilament suture. The
patient should be kept supine for 1–2 h post-op
and then discharged home after meeting discharge criteria. Neurological examination should
be performed before discharge.
Kyphoplasty
Kyphoplasty is a procedure similar to vertebroplasty with the exception that an inflatable balloon tamp is inserted into the vertebral body. The
benefits of this procedure over VP are largely
radiographic and theoretical. The major benefit
is some height restoration to acute fractures
and decreased extravasation of cement due to
lower injection pressures and compacted bone
around the cavity which was created [30, 31].
Kyphoplasty has been shown to have greater volumes of cement injected per level, better shortterm pain relief, and better short- and long-term
kyphosis angles. Long-term clinical outcomes in
terms of pain at 1 year are similar [30, 31]. The
downside of kyphoplasty is the longer operative
times often necessitating general anesthesia.
Recently, the Kyphon device has come “off patent” making the procedure more affordable since
generic devices have entered the market reducing
costs. Kyphoplasty is often performed bilaterally
as this allows for maximal height restoration. In
our experience, end plate restoration is more
likely to occur in the acute period before fractures organize into the chronic phase.
In kyphoplasty, docking of the needle tends to
be done in a similar fashion to vertebroplasty
done by the bipedicular approach (Fig. 18.7). The
kyphoplasty needle should have a mildly triangulated trajectory and lie in the posterior half of the
vertebral body. The stylet is moved, and a hand
drill is used to create a pathway for the balloon.
The drill should be stopped 3–6 mm from the
18 Anterior Spinal Column Augmentation Techniques
Fig. 18.7 Balloon-assisted kyphoplasty showing restoration of vertebral body height with packing out of cancellous
bone to create cavity and filling with cement under low pressure
most posterior aspect of the anterior cortex of the
body, and, at this point, the drill tip should
approximate the midline. The drill is then
removed, and the balloon tamp is inserted. The
markings on the balloon tamp are on the posterior
aspect of the balloon, and these markings should
be at least 5 mm from the tip of the cannula. The
tip of the tamp should not be less than 5 mm from
the anterior aspect of the vertebral body to assure
that inflation will not be inside the cortical bone.
Once the operator is satisfied with the balloon
position, balloons are inflated with contrast under
fluoroscopy and with continuous pressure monitoring. It is important to make sure that balloon
tamps do not violate the cortical bone on any surface as this will increase the risk of cement
extravasation. The balloons should not be inflated
to more than 220 psi, which is the maximum recommended pressure. From our experience, staggering the balloon inflation helps delineate the
level of inflation of each balloon as the contrast
can obscure visualization if one is fully inflated
on the lateral imaging. This also aids in symmetric fracture reduction. Once satisfactory inflation
is achieved, balloons are deflated and removed.
In the event that the fracture displaces after the
balloons are deflated, there is the option to keep
one inflated for the injection of the cement. Small
cannulas containing PMMA at the consistency of
toothpaste are inserted. It should be noted that
this is thicker than the consistency of PMMA
used for vertebroplasty. These are injected by
hand, taking care to watch for extravasation.
Typically cement is injected in small increments bilaterally to allow for better visualization
and less fluoroscopy time. Once the surgeon is
satisfied with the final images and cement has
hardened, the trocars are removed, and the incisions can be closed with monofilament suture.
Postoperative imaging can be left to the surgeon’s
discretion, but oftentimes the patient can be discharged the same day.
Kiva
The Kiva implant is a polyetheretherketone
(PEEK-Optima) coil deployment system that
allows fracture reduction in a controlled manner
over a removable Nitinol Osteo guidewire. As the
implant is deployed, the coil stacks upon itself
adding substance to the body while reducing the
fractured end plate. Once the coil is completely
deployed, it forms a hollow cylinder ideally with
its borders from end plate to end plate. PMMA is
injected after the device is deployed to fill the
I.K. White et al.
Fig. 18.8 (a) KIVA device docking needle is placed in a
transpedicular trajectory with inner trocar in place. (b)
Trocar is removed, and KIVA deployment device is
attached. (c) The coil knob is turned to deploy the coil
completely. The KIVA device is then deployed over the
coil using the knob on the other side. The coil is then
center, containing the PMMA within the walls of
the cylinder as shown in Fig.
18.8a–d.
The Kiva implant is deployed through a unilateral transpedicular approach. The setup is the
same for both vertebroplasty and kyphoplasty,
and the procedure can be done under local or
general anesthesia. The initial needle is placed in
a similar fashion in the anterior half of the verte-
retracted and the device detached, and (d) a
polymethylmethacrylate- filled plunger fills the center of
the device through holes in the center of the device in a
controlled fashion similar to kyphoplasty. The device both
restores height and decreases radiographic cement
extravasation
bral body. It does not have to reach the midline as
with other unilateral approaches. At this point,
the stylet for the needle is removed, and the head
of the device is inserted near the most anterior
part of the vertebral body. The device is then
turned medially with the top of the device deploying the coil. Once the coil is deployed, the implant
is deployed over the coil slowly increasing the
18 Anterior Spinal Column Augmentation Techniques
anterior vertebral body height. Once the graft is
deployed, PMMA is injected through the deploying device through the graft into the center of the
cylinder that the graft created. The graft is then
detached from the deploying device, and the
wound is closed.
The Kiva device was recently compared to
kyphoplasty in the KAST trial. The major finding
was the Kiva device showed significantly less
cement extravasation. This can be explained by
the device’s ability to keep the PMMA central.
This finding did not result in any difference in
clinical outcomes. There was also a decrease in
adjacent level fractures but this failed to meet significance. Overall the trial showed that the Kiva
implant is a safe alternative to kyphoplasty.
Using Navigation
In a very select set of instances, visualization of
the vertebral column may be obscured in the
severely osteoporotic, severely obese, or when
vertebral levels are near the diaphragm. In these
patients where the landmarks are obscured, placing the needle can be very dangerous. Spinal
navigation in these patients should be considered.
A reference arc should be attached to the spinous process rostral to the most superior level
that needs to be addressed with the camera at the
head of the bed. The areas of fracture can be
localized with C-arm. The patient is then prepped
and draped, and the O-arm is also draped so as to
use the biplanar fluoroscopy function of the
O-arm. Once acquisition is taken, the O-arm is
moved rostral, and the navigated pedicle access
needle can be used using three-dimensional navigation for either parapedicular or transpedicular
trajectories. A Kirschner wire is then placed
down the needle into the vertebral body, and the
access needle is removed leaving the K-wire in
place. If multiple levels are to be done, K-wires
should be placed at every level that needs to be
addressed. Vertebral augmentation cannulas are
then placed over the K-wires, and vertebroplasty
is performed under the fluoroscopy function of
the O-arm, and, after all levels are completed, a
three-dimensional scan can be taken to confirm
the location of the cement within the body.
Although this technique is substantially more
time consuming, it provides a greater level of
safety in those patients with anatomy that one is
unable to visualize on plain fluoroscopy.
Illustrative Case
History of Present Illness
This is a case of an 82-year-old female who has
a history of osteoporosis confirmed by DEXA
scan (T scores <−2.5) on calcium supplementation and teriparatide, who sustained an osteoporotic compression fracture at T10 3 years prior
to vertebroplasty treatment due to intractable
pain. She did well after the procedure and
returned to her prior functional status until
6 weeks later when, while mopping her floor,
the patient felt a pop in her back causing her to
lose her breath and fall to the floor in pain. She
did not note any numbness, tingling, weakness,
or loss of continence.
Physical Examination
Upon initial presentation, she was at her neurologic baseline without deficits. She was alert and
conversational, oriented x3. She was very tender
to palpation over her mid to lower back. All
extremities were moving with 5/5 movement
with good sensation in all and she did not have
any perigenital/anal anesthesia.
Radiographic Evaluation
Her preoperative radiographs are shown in
Fig. 18.9a, b showing acute compression fractures at T11 and T12.
Initial Management
She was treated with bracing and pain control,
and, although she was able to return home, her
activity level decreased secondary to pain at her
2- and 6-week appointments. Her standing
I.K. White et al.
Fig. 18.9 (a) AP preoperative radiographs demonstrating compression fractures at T11 and T12. (b) Sagittal radio-
graphs demonstrating the same pathology
radiographs looked grossly similar at this
appointment showing an intact posterior cortex,
but her son reported that she mainly was sitting
in her wheelchair without much activity over
this time period. It was at this point they decided
she would like to undergo vertebroplasty.
Procedure and Outcome
The unilateral parapedicular vertebroplasty was
performed under conscious sedation. Fourteen
milliliters of PMMA was injected at each level
without complication. Trajectories are shown in
18.10a and b. In recovery, she felt immediate
Fig.
pain relief. Postoperative radiographs show
excellent cement fill without extravasation
(Fig. 18.11a, b). At 3 months post-surgery, she
has returned to her baseline functional status.
Technical Pearls
• When performing these procedures and especially when doing multiple levels, biplanar
fluoroscopy can be used. This can be done in
an interventional suite or positioning two
C-arms.
• It is always imperative to obtain true AP and
lateral images of the targeted vertebrae.
• When doing multiple vertebrae, it should be
noted that a single batch of cement should
be kept at cool temperatures to slow polymerization. One batch typically can do three
vertebrae, and, at our institution, no more
than three levels are ever done at one time
due to PMMA toxicity and a higher risk of
adverse events. A larger amount of PMMA
should be used in kyphoplasty as there
should be enough bone cement to fill the
cavity created and the surrounding trabecular bone.
• When treating a significantly collapsed vertebra with kyphoplasty, there are two techniques that have been shown to keep the
fracture reduced. If there is unilateral collapse, the cavity contralateral to the collapse
can be filled first, allowing some cement to
pack the trabecular bone providing a structural buttress. The second balloon can then be
withdrawn.
• The second technique can be used in the setting of vertebra plana which re-collapses after
balloon withdrawal. One milliliter of PMMA
can be injected into the body, and the balloon
can be reinserted and inflated allowing cement
18 Anterior Spinal Column Augmentation Techniques
Fig. 18.10 (a) Showing intraoperative parapedicular trajectory in the AP plane reaching the midline. (b) Showing the
same in the sagittal plane
Fig. 18.11 (a) Showing postoperative AP radiographs and (b) sagittal radiographs post-augmentation. It should be
noted that with vertebroplasty, end plate reduction and deformity correction are no different than preoperative imaging
to harden forming a thin shell of cement. The
balloon can then be withdrawn and the rest of
the cavity filled with cement.
this procedure involve the initial placement of the
trocars and extravasation of bone cement. Placing
Jamshidi needles through the neuro-elements can
be avoided by obtaining true AP and lateral
radiographs, lining up the end plates, pedicles,
Complications and Avoidance
and facet joints. If the image needs to be improved
in the osteoporotic patient, magnification on the
Preoperative planning must always focus on the
goals of the surgery while preventing complications. The two complications that can arise from
C-arm may be increased, the tube may be brought
closer to the patient, and the respirations may be
held until the Jamshidi needle is placed. As stated
I.K. White et al.
before, the transpedicular approach should start
on the superolateral aspect of the pedicle to avoid
damage to the nerve roots. The parapedicular
approach can be started lateral to the pedicle and
medial to the costovertebral joint. It should be
noted that the needle on this approach should not
be medial to the medial aspect of the pedicle until
it reaches the posterior aspect of the vertebral
body to once again avoid nerve root injury and
damage to the spinal cord. The parapedicular
approach is usually done in mid to high thoracic
fractures with transpedicular being reserved for
low thoracic and lumbar fractures. With these
precautions taken, the operator can be certain that
the needle is in good position and has not damaged any of the neural elements.
The most common complication occurring in
both vertebroplasty (VP) and kyphoplasty (KP)
is PMMA extravasation that occurs in 11–75%
of VP patients and 5–38% of KP patients. These
are radiographic leaks and are rarely symptomatic. Symptomatic leaks were reported in 1.48%
of VP patients and 0.06% of the KP patients
[30]. This higher leak rate is thought to be caused
by the higher pressures that VP cement is
injected under, the lower viscosity of the cement,
and the ability of kyphoplasty to pack out the
bone around the cavity that it creates. The majority of these leaks go into the paravertebral soft
tissue, but extravasation into the spinal canal can
be catastrophic, and having a spine surgeon at
the institution available to perform emergent
decompression is imperative. In order to avoid
this, it is advisable to do this under live fluoroscopy and to confirm an intact posterior cortex
when starting out.
Cement extravasation can be minimized first
by patient selection, choosing patients with an
intact posterior cortex if possible. The needle
should be placed in the anterior two-thirds of the
vertebral body to allow some room to fill the
body without reaching the posterior cortex too
early. It is essential to make sure the PMMA is at
a consistency thick enough to maintain its integrity. When doing a kyphoplasty, the balloon
should not be inflated to the point where there is
any outpouching through any of the cortical
bone so as not to create any breaches. When
deploying the PMMA, it should be done in small
increments 0.2–0.5 ml at one time with frequent
fluoroscopy. When using the bilateral approach,
small amounts of PMMA should be placed alternating each side one at a time as on the lateral
image large amounts of PMMA on one side can
obscure visualization of the contralateral PMMA
as it is being deployed. If there is any evidence
of breaches in the contrast, the procedure should
be stopped immediately. If vertebroplasty is
being performed and it is felt that a less than
adequate amount of contrast has been deployed,
the cannula can be repositioned. Although most
cement leaks are clinically inconsequential, if
there is a significant leak, the patient must be
examined before leaving the operating room,
and, in the face of a neurologic deficit, if a deficit
is appreciated, emergent decompression should
be considered.
Conclusion
Vertebral augmentation is a minimally invasive
technique with expanding indications in the
fields of oncology, trauma, and metabolic dysfunction providing pain relief, deformity correction, and spinal stability with minimal surgical
morbidity and, if careful, low complication rates.
Surgeon familiarity with these techniques have
led to utilization of these materials in hybrid
models both in the augmentation of pedicle
screw pullout strength and providing anterior
stiffness to an unstable spine allowing fewer segments to be fixated. Newer devices are currently
being developed that may provide greater deformity correction with less chance of cement
extravasation.
References
1. Cooper C, Atkinson EJ, O’Fallon WM, Melton LJ 3rd.
Incidence of clinically diagnosed vertebral fractures:
a population-based study in Rochester, Minnesota,
1985–1989. J Bone Miner Res. 1992;7(2):221–7.
2. Lindsay R, Silverman SL, Cooper C, et al. Risk of
new vertebral fracture in the year following a fracture.
JAMA. 2001;285(3):320–3.