Vertebroplasty, the percutane-ous augmentation of vertebral body volume and strength by injection of a hardening material in a liquid state, was originally used to manage pain-ful neopla
Trang 1Percutaneous Treatment of Vertebral Body Pathology
Jeffrey M Spivak, MD, and Michael G Johnson, MD
Abstract
Minimally invasive methods of
treat-ing the symptoms of spinal
compres-sion fractures have attracted the
at-tention and interest of both surgeons
and patients over the past two
de-cades Vertebroplasty, the
percutane-ous augmentation of vertebral body
volume and strength by injection of
a hardening material in a liquid state,
was originally used to manage
pain-ful neoplastic vertebral body lesions
and pathologic fractures Surgical
acrylic cement was injected during
open surgery to strengthen vertebral
bodies with angiomas.1An analgesic
effect was noted, and indications for
the technique in neoplastic disease
ex-panded to include both primary and
secondary pathology Although most
metastatic lesions of the spine are
ef-fectively managed with radiation
therapy, pain relief is not universally
successful for those with marked
structural compromise or collapse
Vertebroplasty provides both analge-sia and vertebral structural stabiliza-tion in a single procedure
Kyphoplasty not only can facilitate increased stability, but it also may allow some correction in cases of acute and subacute fracture collapse and kyphotic deformity A percutane-ous inflatable balloon device (bone tamp), approved by the US Food and Drug Administration (FDA) since
1998, is used to restore vertebral body height The created void is then filled with a low-pressure, high-viscosity injection of a hardening support material Polymethylmethacrylate (PMMA) is currently used in both procedures
Both vertebroplasty and kypho-plasty can be used to treat painful acute, subacute, and chronic osteo-porotic compression fractures caused
by decreased bone mineral density and changes in bone architecture that accompany senile osteoporosis, espe-cially in postmenopausal older women.2-4 It is estimated that age-related osteoporotic compression fractures occur in more than 500,000 patients per year in the United States.5 Most of these fractures are successfully managed with analgesic medications and orthoses Medical evaluation and pharmacologic man-agement of a patient’s underlying os-teoporosis is imperative to minimize the risk of additional vertebral frac-ture Physical exercises, preferably movement exercises and extension protocols, are instituted once the ini-tial pain has resolved Only rarely do these fractures involve the posterior vertebral cortex and result in spinal canal compromise and neurologic deficit
Dr Spivak is Director, The Hospital for Joint Dis-eases Spine Center, New York, NY Dr Johnson
is Assistant Professor, Orthopaedics and Neuro-surgery, University of Manitoba, Manitoba, Win-nipeg, Canada.
None of the following authors or the departments with which they are affiliated has received anything
of value from or owns stock in a commercial com-pany or institution related directly or indirectly
to the subject of this article: Dr Spivak and Dr Johnson.
Reprint requests: Dr Spivak, The Hospital for Joint Diseases Spine Center, 301 East 17th Street, New York, NY 10003.
Copyright 2005 by the American Academy of Orthopaedic Surgeons.
Percutaneous vertebral body injection procedures currently are used to stabilize and
reinforce weakened or fractured bone resulting from metastatic disease and severe
osteoporosis Both vertebroplasty and kyphoplasty can reinforce the structure of a
vertebral body and provide pain relief, but the procedures have technical differences.
Kyphoplasty improves vertebral height to varying degrees in nearly three quarters
of patients Kyphosis is improved more effectively when the procedure is performed
within 3 months from the onset of fracture pain To date, it is unknown whether
vertebroplasty with preprocedure postural reduction can provide similar
improve-ment of deformity Complications are relatively infrequent with both vertebroplasty
and kyphoplasty Cement leakage from the vertebral body is more likely with
ver-tebroplasty than with kyphoplasty Leakage is more common in the treatment of
patho-logic fractures resulting from metastatic disease Clinical complications caused by
cement leakage and neural compression are infrequent Specific indications for these
injection procedures need to be more clearly refined Long-term outcomes,
includ-ing the fate of the injected material and the effect on adjacent vertebrae, have yet to
be determined.
J Am Acad Orthop Surg 2005;13:6-17
Trang 2Although many physicians think
that osteoporotic compression
frac-tures routinely heal uneventfully
without significant long-term
se-quelae, this may not be accurate Both
thoracic and lumbar compression
fractures have been associated with
decreased lung capacity.6 The
pres-ence of five or more thoracic
compres-sion fractures has been associated
with a higher risk of death from
pul-monary complications in women
aged 65 years and older.7 Residual
kyphotic deformity may result in loss
of sagittal balance with significant
limitation of functional abilities, pain,
and a generalized poor overall health
perception.8 In other cases, a
pro-longed period of incapacitating back
pain affects the patient’s quality of
life and increases the likelihood of
bed rest–related morbidity, including
pressure sores, pneumonia, and
thromboembolic disease
Indications
Both vertebroplasty and kyphoplasty
may be used to augment painful
weakened or fractured vertebrae in
a variety of clinical settings (Table 1)
Controversy exists as to the specific
indications for these procedures
Pro-ponents of their aggressive early use
are generally concerned with the
po-tential disease-related morbidity,
in-cluding progressive kyphosis and
per-sistent pain and disability Advocates
of more limited use are concerned with
the incidence of procedure-related
morbidity, including immediate
com-plications, the long-term effects of the
cement used, and potential negative
biomechanical effects on adjacent
vertebrae
Stabilization of a painful
metastat-ic vertebral lesion is the least
contro-versial indication for percutaneous
vertebral augmentation Interruption
of the posterior vertebral cortex by
tu-mor or fracture is a relative
contrain-dication because risk of extravasation
into the spinal canal is increased
Sig-nificant spinal canal compromise by tumor or fracture fragments is an ab-solute contraindication, as is complete vertebral body collapse
Currently, both vertebroplasty and kyphoplasty are most commonly used to stabilize acute and subacute osteoporotic vertebral compression fractures with collapse and/or ky-phosis (Fig 1) With vertebroplasty, some positional reduction of the ky-photic deformity may be achieved
Although the low-viscosity cement injection will not further correct any kyphosis, generally it will limit pro-gression Kyphoplasty has the
add-ed theoretical benefit of being able to correct kyphosis because insufflation
of the bone tamp can elevate the de-pressed end plates Therefore, kypho-plasty may be preferable when cor-rection of kyphosis is a primary indication
The medical condition of the pa-tient must be taken into consideration when selecting one of these invasive procedures Kyphoplasty typically is performed under general anesthesia, whereas vertebroplasty routinely is
done using only intravenous sedation and local anesthetic Therefore, ver-tebroplasty may be preferred in pa-tients with multiple significant med-ical comorbidities who are being treated for painful vertebral lesions with minimal or no deformity
Patient Assessment
Clinical assessment of the patient with
a painful vertebral lesion or fracture includes a complete history and phys-ical examination along with appropri-ate radiologic studies Important in-formation includes the nature of any trauma associated with the onset of pain, known occurrence of a primary
or metastatic lesion, previous osteo-porotic fractures, and an assessment
of risk factors for osteoporosis if that diagnosis has not yet been made Physical examination should include measurement of height compared with historic data from the patient, visualization of thoracic kyphosis or loss of lumbar lordosis, palpation of tenderness along spinous processes
Table 1 Indications and Contraindications for Percutaneous Vertebral Augmentation by Vertebroplasty or Kyphoplasty
Painful metastatic lesion with intact posterior vertebral cortex
Fractures or neoplasms with spinal canal compromise Chronic (>3 months) compression
fracture with nonunion
Vertebra plana (complete vertebral body collapse) Progressive kyphosis to≥20° in a
subacute (<3 months) compression fracture
Subacute (<3 months) compression fracture with persistent pain and dysfunction despite adequate nonsurgical management
Fractures and metastatic vertebrae with posterior vertebral cortex involvement and compromise
Acute compression fracture with≥20°
kyphosis or≥40% collapse Less than one-third vertebralbody height remaining Acute compression fracture with one or
more prior compression fractures and kyphotic deformity
Trang 3or widening between adjacent
process-es, and a thorough neurologic
eval-uation
Plain radiographs should include
standing anteroposterior (AP) and
lateral views centered at the level of
the fractured vertebra, as well as a
standing lateral 36-in radiograph of
the entire spine to assess overall
re-gional and segmental sagittal
align-ment Flexion and extension lateral
radiographs may be helpful in assess-ing the degree of fracture mobility and healing (Fig 2) If tolerated by the patient, a hyperextension lateral ra-diograph over a bolster should be considered before performing an in-jection procedure, to assess the poten-tial for postural reduction of vertebral collapse and kyphosis
(MRI) is able to visualize both
verte-bral and soft-tissue pathology In pa-tients with osteoporotic fractures, dif-fuse or focal signal changes of decreased intensity on T1-weighted images and increased signal
intensi-ty on T2-weighted images may be in-dicative of an active fracture not yet fully united MRI is particularly help-ful with multiple compression defor-mities when trying to determine which are still active and therefore more likely to be painful The extent
of marrow involvement in patients with metastatic disease can be as-sessed, with special attention paid to the nonfractured vertebrae MRI also will demonstrate the soft-tissue mass associated with a metastatic patho-logic fracture and can be used to as-sess the integrity of the posterior ver-tebral cortex The integrity of the posterior wall may not be as well vi-sualized as with computed tomogra-phy (CT) scans; therefore, any ques-tionable involvement or compromise
of the posterior vertebral cortex seen
on MRI should prompt further eval-uation with a CT scan
CT provides excellent detail of the bone involvement, and it is the best imaging procedure for assessing the extent of vertebral body and poste-rior element fracture The combina-tion of CT scan and plain radiographs
is helpful to fully classify the fracture type It is important to distinguish be-tween a compression fracture, with collapse of the anterior vertebral cor-tex (with or without upper or lower end plate involvement), and a burst fracture, in which the posterior wall
of the vertebra is fractured, as well.9 Generally, burst fractures demon-strate more uniform vertebral col-lapse, whereas compression fractures show more anterior wedging or ky-photic collapse
Technetium Tc 99m–labeled bone scanning can be useful in assessing for increased metabolic activity de-noting increased bone turnover, as seen in infiltrative lesions and incom-pletely healed fractures Bone scans are particularly useful in assessing
Figure 1 A,Lateral radiograph in a 72-year-old man made 2 days after a minor fall
dem-onstrating a compression fracture of L1 B, Lateral radiograph taken 3 weeks later
demon-strating progression of anterior vertebral collapse at a time when the patient was having
worsening pain The patient was treated with kyphoplasty Postoperative lateral (C) and
anteroposterior (D) radiographs showing restoration of the collapse and minor disk space
extravasation of cement The patient had immediate full resolution of pain, which persisted
at 6 months postoperatively.
Trang 4fracture activity in patients with
mul-tiple compression deformities
In-creased vertebral activity on bone
scan has been shown to be highly
pre-dictive of a positive clinical response
to vertebroplasty.10
Technique
Vertebroplasty and kyphoplasty are
both done with the patient positioned
prone on a radiolucent table This
al-lows for the use of biplanar
fluoros-copy The use of a Jackson radiolucent table and dual image intensifiers (which provide simultaneous pos-teroanterior [PA] and lateral imaging)
is optimal However, a single image intensifier can be used, rotating be-tween PA and lateral images as
need-ed For vertebroplasty, local anesthetic
is combined with intravenous seda-tion; for kyphoplasty, a general anes-thetic is more commonly used
Two techniques, the transpedicu-lar and the extrapedicutranspedicu-lar, can be used to place the injection trocar or
working cannula.11The transpedicu-lar approach is more commonly used
in the lumbar spine (Fig 3) The tip
of the injection trocar is started at the upper/outer corner of the visualized pedicle outline as seen on the PA radiograph (left pedicle, 10 o’clock position; right pedicle, 2 o’clock po-sition) Proper overall sagittal trajec-tory and starting point within the superior-inferior pedicle border are confirmed on the lateral radiograph before trocar advancement Trocar ad-vancement is visualized
fluoroscop-Figure 2 A 77-year-old man presented with a 4-month history of unremitting midback pain that limited ambulation and functional ability
and required narcotic use A, Standing lateral radiograph demonstrating an anterior compression deformity of T9 Note the diffuse spondy-losis and multilevel anterior bridging osteophytes B, Supine extension lateral radiograph demonstrating an intervertebral defect (arrow) just below the superior end plate C, T2-weighted sagittal MRI scan demonstrating the fluid-filled intervertebral cleft characteristic of a fracture nonunion Anteroposterior (D) and lateral (E) intraoperative fluoroscopic views with bone tamps inflated F, Postoperative lateral
radiograph after stabilization using percutaneous kyphoplasty Note the small amount of clinically asymptomatic anterior extravasation The patient experienced complete pain relief and remained asymptomatic 1 year postoperatively.
Trang 5ically When the trocar tip is midway
along the length of the pedicle on the
lateral view, it should be central in the
pedicle outline on the PA view When
it is through the pedicle and at the
posterior vertebral cortical margin on
the lateral view, the trocar should be
just within the medial border of the
pedicle outline on the PA view For
vertebroplasty, the trocar is advanced
until the tip is at the junction of the
anterior and middle thirds of the
ver-tebral body For kyphoplasty, the
po-sitioning trocar is exchanged for a
working cannula over a guidewire
The cannula is positioned near the posterior vertebral body margin while the working instruments (ie, drill, bone tamp, cement inserters) are advanced anteriorly until they are ap-proximately 3 mm from the anterior vertebral body border Convergence
of the tip toward midline should be followed on the PA view
The extrapedicular approach is commonly used in the thoracic spine (Fig 4) The starting point is more lat-eral than the pedicle, with the trajec-tory more medially directed, which enables a more medial trocar tip
placement within the vertebral body than a transpedicular route through the sagittally oriented thoracic pedi-cles would allow The trocar tip is first inserted lateral to the pedicle, either through the thoracic transverse pro-cess or along the transverse propro-cess/ rib junction Under biplanar fluoro-scopic visualization, the needle or trocar is advanced along the medial border of the rib until the lateral bor-der of the pedicle is reached on the
PA view and the posterior vertebral body margin is reached on the
later-al image For kyphoplasty, the trocar
Figure 3 Trajectory of the transpedicular approach A, Posteroanterior view B, Lateral view C, Axial representation Symbols along the
trajectory indicate the position of the trocar tip at various depths of insertion The tip should not pass medial to the medial border of the pedicle on the posteroanterior view until it is anterior to the posterior margin of the vertebral body on the lateral view = insertion point,
◊ = point at pedicle/vertebral body junction, = midvertebral body.
Figure 4 Trajectory of the extrapedicular approach for needle or trocar placement A, Posteroanterior view B, Lateral view C, Axial
rep-resentation Symbols along the trajectory indicate the position of the trocar tip at various depths of insertion The tip should not pass medial
to the lateral border of the pedicle on the posteroanterior view before the posterior aspect of the vertebral body is seen on the lateral view.
= insertion point, ◊ = point at pedicle/vertebral body junction, = midvertebral body.
Trang 6is advanced only minimally beyond
this position until the tip is anterior
to the posterior aspect of the
verte-bral body on the PA view and just
me-dial to the lateral border of the
pedi-cle on the lateral view The trocar is
then exchanged for the working
can-nula over a guidewire, with further
advancement of the working
instru-ments beyond the cannula toward the
anterior vertebral body For
vertebro-plasty, the injection trocar is advanced
further anteromedially toward the
central aspect of the vertebral body
An 11-gauge injection trocar is
used for vertebroplasty Regardless of
the trocar placement approach,
intra-vertebral venography is performed
before injecting the PMMA to exclude
the placement of the needle tip
with-in a major vascular channel A venous
blush within the vertebral body
in-dicates proper needle placement
be-cause the injected dye must remain
and pass through the vertebral
mar-row before exiting through the
ve-nous sinusoids Lack of a veve-nous
blush indicates rapid release of the
dye directly out of the vertebra on
in-jection, so the trocar tip should be
re-positioned Once proper trocar
posi-tion is confirmed, the cement is mixed
and injected into the vertebral body
in a low viscosity state under
contin-uous fluoroscopic visualization
Injec-tion is continued until hemivertebral
or holovertebral filling is achieved
and no more cement can be delivered
into the body It is stopped
immedi-ately if any extravasation is noted into
the surrounding veins, the spinal
ca-nal posterior to the vertebral body, or
the disk space Clinical improvement
has not been shown to correlate with
the amount of cement injected After
completing the injection, the trocar is
removed, and hemostasis is obtained
by pressure The contralateral
hemi-vertebra is treated in the same
man-ner when a bilateral injection is to be
used
Kyphoplasty also can be
per-formed percutaneously through
ei-ther a transpedicular or lateral
extra-pedicular approach Bilateral 3.5 mm–
diameter working cannulas inserted over the 11-gauge positioning trocars are used to create the working chan-nels within the vertebra using a hand drill A hollow trocar often is used in place of one of the drills to remove a bone biopsy core of tissue The cre-ated channels allow passage of the de-flated bone tamps, which are
inflat-ed with a pressurizinflat-ed radio-opaque liquid after being properly positioned
In theory, inflation of the balloons in-creases the vertical height of the ver-tebral body, thereby reducing kypho-sis As the bone tamp is inflated, the surrounding cancellous fracture frag-ments are compacted along the mar-gin of a central void that is created
In one clinical series, the average amount of balloon inflation volume was 2.6 mL (range, 0.5 to 5.0 mL), and the average balloon inflation pressure was 130 psi (range, 70 to 250 psi).12 The balloons are removed, and the defects are simultaneously filled with PMMA inserted manually through the trocars in a relatively high viscos-ity state using a low injection pres-sure By using low injection pressure and a higher viscosity cement while injecting into a bony void
surround-ed by compactsurround-ed cancellous bone, this technique theoretically reduces the risk of intravascular injection as well as leakage into either the sur-rounding tissues or the spinal canal
An in vivo study of contrast injection leakage before and after balloon in-flation and fracture reduction sup-ports this theory The authors noted significantly less vascular and trans-cortical extravasation of contrast af-ter use of the inflatable bone tamps
(P = 0.001 for each).13
Postoperative Management
Patients are mobilized as soon as the sedation or general anesthetic has worn off No period of bed rest is needed Many patients have
restrict-ed activity for weeks or longer
be-cause of their painful fractures and may be relatively debilitated both be-fore and immediately after the injec-tion procedure Progressive return to full activities is recommended, with-out specific restrictions Physical ther-apy for gait training, aerobic condi-tioning, and back-specific stretching and strengthening may benefit many
of these patients Most patients do not require assistive devices for ambula-tion, but such devices may be useful for patients who have been nonam-bulatory because of their fractures Postoperative bracing is not used rou-tinely because the fractures are ren-dered mechanically stable by the ce-ment injection
Results
The outcome of vertebral injection procedures is highly dependent on the clinical indication for the proce-dure and, to a lesser extent, the tech-nique used Most published series of vertebroplasty have reported on its use to treat patients with neoplastic lesions and/or osteoporotic compres-sion fractures.6,11,14-17More recent ky-phoplasty series have reported only
on patients with osteoporotic com-pression fractures.18,19
Patients with painful metastatic vertebral lesions have had good clin-ical results with vertebroplasty.16,17,20
In one series of 37 patients with ver-tebral metastases, 73% had marked clinical improvement after percutane-ous vertebroplasty.17 Improvement was defined as a decrease in pain re-sulting in the dose of analgesia being reduced by 50% or as a change from
a narcotic to a nonnarcotic medica-tion The decrease in pain after ver-tebroplasty was maintained at
follow-up, with 76% of patients reporting persistent pain relief at 6 months and 65% at 1 year Another series
report-ed excellent pain relief in 11 of 18 met-astatic lesions.16
The pain relief experienced by pa-tients undergoing vertebroplasty is
Trang 7similar to that with radiation
thera-py for painful metastatic lesions of
bone.21,22However, vertebroplasty is
associated with a more rapid
im-provement in pain, with 80% of
pa-tients noting improvement within the
first 24 hours and being able to stand
the day after the procedure.23Pain
re-lief normally is seen 2 to 10 days
af-ter nonfractionated radiation therapy
and 1 to 2 weeks after conventional
radiation therapy.21,22Vertebroplasty
is not an alternative to radiation
ther-apy; rather, it can be used as a
com-plementary adjunct procedure
Ce-ment injection provides a mechanical
pain treatment by stabilizing the
spi-nal segment; radiation therapy
pro-vides a biologic treatment modality
The mechanism by which
verte-broplasty with injection of PMMA
re-lieves pain is not clear Neoplasms are
not directly innervated; rather, the
pain is thought to be caused by
frac-ture or impending fracfrac-ture stressing
of the remaining bone Nerve endings
in the remaining normal bone may be
stimulated by the mass effect of the
neoplastic tissue Paraneoplastic
pro-duction of humoral mediators also
may play a role in pain production
The analgesic effect of vertebral
injec-tion is thought to be the result of
im-mobilization of the bone and
struc-tural support and possibly of the
destruction of the terminal nerve
end-ings by the cytotoxic or thermal
ef-fects of PMMA
The relationship between amount
of vertebral fill from percutaneous
ver-tebroplasty using PMMA and pain
re-duction has been examined in a
se-ries of 40 cases (37 patients) of
metastatic disease and myeloma
us-ing postinjection CT scans.15Lesion
filling was >75% in only 5 of the 40
cases, 50% to 74% in 14, 25% to 49%
in 13, and <25% in 8 No statistically
significant relationship was found
be-tween the cause of the osteolytic
le-sion, the percentage of vertebral body
filling by PMMA, and pain reduction
Several clinical series have
report-ed results of vertebroplasty for
pain-ful osteoporotic vertebral compression fractures, with the percentage of good and excellent results ranging from 75%
to 100%.11,14,16,19,20,24-26In general, how-ever, these series are retrospective, with limited duration of follow-up Jensen
et al11reported on 29 patients who un-derwent percutaneous vertebroplasty
to manage osteoporotic vertebral body compression fractures Two patients had complete resolution of back pain immediately after vertebroplasty
Twenty-six patients (90%) described pain relief and improved mobility within 24 hours of treatment All pa-tients who had required parenteral narcotics tolerated reduction to oral medications Three patients had no significant pain relief and were con-tinued on pretreatment medical reg-imens.11Another prospective series of
16 patients undergoing vertebroplasty for painful osteoporotic compression
fractures showed a significant (P <
0.005) decrease in pain by day 3 post-procedure, which was maintained at
6 months.14Asingle series of long-term (mean, 48 months) results after ver-tebroplasty for osteoporotic fractures showed maintenance of pain relief at long-term follow-up similar to that achieved 1 month after the proce-dure.27
A preliminary report of a multi-center study of kyphoplasty for osteo-porotic compression fractures in 340 patients (603 fracture levels) found a 90% initial symptomatic and
function-al improvement rate and significant
(P < 0.05) restoration of the anterior,
middle, and posterior vertebral body height when performed within 3 months of the onset of the fracture.18
In a prospective study of 70 consec-utive kyphoplasty levels in 30 pa-tients,12the indication for kyphoplasty was a painful osteoporotic compres-sion fracture (mean duration of symp-toms, 5.9 months) Clinical assessment, using preoperative and latest postop-erative data from the Medical Out-comes Study 36-Item Short Form,
showed significant (P < 0.01)
improve-ment in scores for bodily pain,
phys-ical function, vitality, mental health, and social functioning at a mean follow-up of 6.7 months Only gen-eral health and role emotional scores did not show significant improvement Radiographic evaluation before and after kyphoplasty indicated varying amounts of height restoration in 70%
of the levels injected and no height restoration in 30% Overall height loss
by the fracture averaged 8.7 mm (range, 2 to 17 mm) Overall height loss restoration among all injected lev-els was 2.9 mm (an average of 35%) However, in the levels showing any height restoration (70% of total lev-els), the average height restoration was 4.1 mm (47% of lost height) Ce-ment leakage was seen at six levels (8.6%): twice into the disk space, three times into the soft tissues, and once into the epidural space None of these incidents was clinically significant.12
Complications
Reported complication rates for ver-tebroplasty have been very low in nu-merous series.1,15,17,25,28,29In decreas-ing incidence, reported complications include cement leakage, which can range from asymptomatic to causing neurologic compromise; cerebrospi-nal fluid leak; cement embolization causing pulmonary embolism; and infection (Fig 5)
PMMA leakage was documented
in 29 of 40 cases by CT scan evalu-ation after percutaneous vertebro-plasty for metastatic lesions and my-eloma.15Fifteen of the leaks were into the spinal canal, 8 into the neural fo-ramina, 8 into the adjacent disk space,
21 into the paravertebral tissue, and
2 into the lumbar venous plexus Ce-ment leakage into the epidural space was strongly associated with poste-rior vertebral cortical destruction by fracture and tumor Leakage of PMMA into the neural foramina was associ-ated with posterior cortical destruc-tion in six of the eight cases Intradis-kal PMMA leakage was associated
Trang 8with cortical fracture or osteolysis of
the vertebral end plates in all cases
None of the documented leaks
com-promised axial pain relief One leak
into the psoas muscle produced a
tran-sient femoral neuropathy that resolved
in 3 days One of the foraminal leaks
produced nerve root compression
re-quiring decompressive surgery 1
month after the procedure
In another clinical series of 53
in-jected levels in 35 patients, the
over-all complication rate was 6% per level
treated, with two cases of cement
leak-age requiring delayed surgical
inter-vention.29Three other asymptomatic
cement leakages were noted, and one
additional patient had a suspected
ce-rebrospinal fluid leak requiring 1
week of hospitalization and
hydra-tion Proper needle placement, PMMA
opacification, and real-time
fluoro-scopic injection visualization help
min-imize these technical complications
Technique-related vertebroplasty
complications can be minimized by
strict adherence to specific patient
in-clusion and exin-clusion criteria Weill
et al17required preservation of at least
one third of the vertebral body height
before performing vertebroplasty Al-though these authors did not
consid-er postconsid-erior vconsid-ertebral wall destruction
to be an absolute contraindication (even though there is a documented increased risk of extrusion of the ce-ment or soft tissue into the spinal ca-nal), others would disagree The risk
of cord compression in the cervical and thoracic levels is relatively high, and the decision to perform vertebroplasty should be made only after careful con-sideration of the potential for alter-native treatments In their series of 37 patients with spinal metastases, 40%
of whom had varying degrees of pos-terior vertebral body wall destruction, Weill et al17reported no cases of sig-nificant cord compression There was only one case of postprocedure radicu-lopathy caused by nerve root compres-sion that required surgery There was
a 38% incidence of cement leakage to-ward the disk, epidural fat, periver-tebral soft tissue, epidural veins, and perivertebral veins The leaks were symptomatic in five cases Two leaks into the vena cava were reported; how-ever, no clinically significant compli-cations resulted.17
Complications reported with ky-phoplasty include cement extravasa-tion as well as rib fractures, which in one study occurred in 2 of 30 patients secondary to patient positioning.12 One case of pulmonary edema and myocardial infarction was attributed
to intraoperative fluid overload
Oth-er reported complications include transient fever, hypoxia, and postop-erative epidural hematoma
(associat-ed with a heparin bolus 8 hours post-operatively) Garfin et al18reported two cases of neurologic injury sec-ondary to problems with needle in-sertion and positioning of the cement filling tube with epidural cement ex-travasation Intraoperative balloon rupture occurred 14 times, chiefly at the end of inflation All broken bone tamps were easily removed, and three cases required reinsertion of a new balloon to complete the inflation No direct patient complications resulted from balloon failure
Postinjection pulmonary embolism
is rare; it may be related to low vis-cosity cement on injection or to leak-age of the methacrylate monomer.29-31 Acute hypotension and increased Pco2
Figure 5 Images after vertebroplasty done for a pathologic metastatic vertebral fracture of L1 in a 73-year-old woman Lateral (A) and anteroposterior (B) radiographs demonstrating cement extravasation into the disk spaces laterally and along the needle tract C, Axial CT
image demonstrating cement leakage into the left pedicle tract (straight arrow) and the right epidural space (curved arrow) The patient became paraplegic within 2 weeks of the vertebroplasty because of the cement extravasation and tumor growth and required emergent posterior decompression and stabilization.
Trang 9measurements because of fat and
mar-row element embolism have been
re-ported after cement vertebroplasty
in-jection into intact sheep vertebrae in
vivo.32No specific direct, major
neu-rotoxic or thermal-related
complica-tions of PMMA have been reported
Only one case of infection (in an
im-munocompromised patient) has been
reported in all published clinical
se-ries to date In an attempt to decrease
the potential for infection, some
sur-geons add tobramycin to the PMMA
when treating immunocompromised
patients.11
An important theoretical concern
after the procedure is the possibility
of increased force on the vertebrae
ad-jacent to a cement-injected level, with
an increase in adjacent segment
frac-ture rate (Fig 6) Recent series have
examined the incidence of adjacent
and remote vertebral fractures after
percutaneous cement injection for
os-teoporotic compression fracture.27,33
In a series of 25 patients with a mean
follow-up of 48 months after
verte-broplasty, 13 patients (52%)
devel-oped at least one new fracture
dur-ing the follow-up period, with a total
of 34 new fractures.27The authors
re-ported a small but significantly
in-creased risk of vertebral fracture in
vertebrae adjacent to the cement
in-jection with an odds ratio (OR) of 2.27,
compared with an OR of 1.44 for
ver-tebrae adjacent to a fractured,
nonce-mented vertebra
Another retrospective review
re-ported that 22 of 177 patients (12.4%)
developed a total of 36 new fractures
after vertebroplasty.34Twenty-four of
the 36 new fractures (67%) occurred
in adjacent vertebral levels Another
finding of concern was that 24 of the
36 new fractures (67%) occurred
with-in 30 days of the vertebroplasty.34A
recent retrospective review of 115
pa-tients (225 treated levels) treated by
kyphoplasty (average follow-up, 10
months) reported a new fracture
in-cidence of 19% (22/115 patients).33
Sev-enteen of the 22 patients with new
frac-tures had adjacent segment fracfrac-tures
Fifteen of the 22 refracture patients had
an initial diagnosis of secondary os-teoporosis caused by chronic cortico-steroid use, making this a patient population at high risk of refracture
Refracture was seen in 7 of 81 primary osteoporosis patients, for an incidence
of 8.6% (yearly incidence, 10.3%).33 These reported refracture rates may not differ significantly from the natural history of the disease for os-teoporotic compression fractures In
a series of 2,725 postmenopausal women (mean age, 74 years) followed
for 3 years, the incidence of new ver-tebral fractures in the first year was 6.6%.35Of the 381 participants who developed a fracture (a group simi-lar to the simi-large series), the incidence
of a new vertebral fracture within the next year increased to 19.2% Although overall reported compli-cation rates are low in published se-ries for both vertebroplasty and ky-phoplasty, with the increasingly widespread use of these procedures, the true complication rates may be significantly higher Larger reported
Figure 6 An 83-year-old man underwent percutaneous vertebroplasty for a painful L3 frac-ture He had initial relief of pain, followed by new acute back pain caused by an L2 fracture
with kyphotic collapse A, Lateral radiograph 6 months after percutaneous vertebroplasty
showing the newly fractured L2 level with previous vertebroplasty of L3 The small amount
of cement extravasation anterior to L3 and into the L2-3 disk space was of no clinical
sig-nificance B, T2-weighted sagittal MRI scan Because of progressive pain and kyphotic
col-lapse, the patient underwent percutaneous kyphoplasty with excellent restoration of
verte-bral height, correction of kyphosis, and relief of back pain C, Intraoperative lateral radiograph demonstrating inflated bone tamps D, Lateral radiograph with cement injected The patient
had marked and sustained pain improvement over 1 year postoperatively without refrac-ture (Courtesy of Frank Schwab, MD, New York, NY.)
Trang 10series are needed to determine the
true safety of these procedures
Experimental Data
Several studies have explored the
bio-mechanical effects of cement injection
into intact and fractured vertebrae In
one study of bipedicular injections
into compression-fractured lumbar
vertebrae, three different
commer-cially available bone cements restored
vertebral body stiffness to greater than
prefracture values.36However, only
Simplex P (Howmedica, Rutherford,
NJ) and Osteobond (Zimmer, Warsaw,
IN) restored vertebral stiffness to
ini-tial values Cranioplastic (Johnson &
Johnson, Raynham, MA) did not In
another study of bipedicular
injec-tions,α-BSM (bone substitute
mate-rial; ETEX, Cambridge, MA), a
bio-degradable calcium phosphate bone
cement, compared favorably with
PMMA in strengthening intact and
fractured osteoporotic cadaveric
ver-tebral bodies.37 With either calcium
phosphate bone substitute or PMMA
augmentation, fracture strength was
significantly (P < 0.05) stronger than
in the intact control group Vertebral
stiffness after both calcium phosphate
bone cement and PMMA
augmenta-tion also was significantly (P < 0.05)
higher than in the intact control
group Similar studies have reported
the efficacy of other bioactive
ce-ments.38,39
Tohmeh et al40conducted a
biome-chanical study comparing
unipedic-ular and bipedicunipedic-ular direct PMMA
needle injection Bipedicular injection
of 10 mL (5 mL per side) improved
vertebral strength significantly (P≤
0.05) more than a unipedicular
injec-tion of 6 mL; however, the
unipedic-ular PMMA injection improved
ver-tebral strength to a significantly (P≤
0.05) greater degree than that of the
unfractured osteoporotic vertebrae
Both injection techniques restored the
stiffness of fractured vertebrae to
pre-fracture values equally well
The change in temperature within and surrounding the vertebral body injected with PMMA has been
report-ed in cadaveric vertebrae maintainreport-ed
in a 37°C water bath.41Temperature recording was done at the anterior cortex, in the center of the vertebral body, and in the spinal canal The two cements tested were Simplex P,
a PMMA cement, and Orthocomp (Orthovita, Malvern, PA), an exper-imental non-PMMA cement Both ce-ments rose to a 41°C peak tempera-ture in the spinal canal; within the vertebral body, Simplex P injection
re-sulted in both a significantly (P≤ 0.05) higher peak temperature and dura-tion of heating >50°C compared with Orthocomp The cooling effect of con-tinuous body fluid circulation, as would occur in vivo, has not yet been studied
Future Considerations
Percutaneous injection of vertebral body pathology as a therapeutic tech-nique is still in the investigation pe-riod, and appropriate indications for use need to be refined Although mul-tiple clinical series have
document-ed the efficacy of both vertebroplasty and kyphoplasty in relieving pain from both vertebral metastases and osteoporotic fractures, no controlled clinical trials have documented their efficacy compared with other treat-ment modalities.42 Current indica-tions in patients with osteoporotic fractures include progressive kypho-sis, multiple fractures with collapse, incapacitating pain with either acute
or subacute fractures requiring nar-cotic use, and chronic pain from ver-tebral fracture nonunion The use of vertebral injection in unfractured ver-tebrae surrounding fractures remains controversial; a prospective random-ized series of patients with and with-out prophylactic adjacent injections
is needed to determine the efficacy of this indication Prophylactic use to prevent fracture in severely
osteopen-ic patients currently has no clinosteopen-ical or scientific basis and thus is not indi-cated
In patients with metastatic disease with or without definite pathologic fracture, vertebral injection may pro-vide pain relief and stability and may
be an excellent adjuvant to radiation and chemotherapy Prospective long-term series are needed to better un-derstand the biologic consequences of injection at the incident vertebral
lev-el and the effect on adjacent levlev-els, which may become more prone to fracture.43Concurrent use with tech-niques such as radiofrequency abla-tion or stereotactic radiosurgery has yet to be investigated
The optimal technique for verte-bral body augmentation is yet to
be determined Factors such as ease
of use, efficacy, risks, complications, ability to correct deformity, and cost all must be considered when decid-ing whether vertebroplasty or kypho-plasty is optimal in a particular clin-ical situation Reported theoretclin-ical benefits of kyphoplasty, such as di-rect cordi-rection of collapse and defor-mity and fewer complications from the high-viscosity, low-pressure injec-tion, have yet to be demonstrated clinically in a direct comparison with postural correction obtained with ver-tebroplasty The theoretical clinical benefits of restoration of vertebral height and kyphosis correction affect-ing future fractures, respiratory com-promise, and pain have yet to be shown in long-term prospective clin-ical series Cost factors include the vertebroplasty injection system or the inflatable bone tamp system, as well
as costs associated with the use of in-terventional radiology or an operat-ing room and hospitalization In pa-tients with unremitting pain and minimal or no deformity, vertebro-plasty may provide equally excellent clinical results with less cost than ky-phoplasty and may obviate the need for general anesthesia Kyphoplasty, however, may provide greater im-provement of kyphotic collapse and