less invasive reduction and fusion of fresh a2 and a3 traumatic l1–l4 fractures with a novel...
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ORIGINAL ARTICLE
Less invasive reduction and fusion of fresh A2 and A3 traumaticL1–L4 fractures with a novel vertebral body augmentation implantand short pedicle screw fixation and fusion
Panagiotis Korovessis • Konstantinos Vardakastanis •
Thomas Repantis • Vasilios Vitsas
Received: 1 June 2013 / Accepted: 12 October 2013
� Springer-Verlag France 2013
Abstract The aim of this clinical study was to report on
the efficacy in reduction and safety in PMMA leakage of a
novel vertebral augmentation technique with PEEK and
PMMA, together with pedicle screws in the treatment of
fresh vertebral fractures in young adults. Twenty consec-
utive young adults aged 45 ± 11 years with fresh burst A3/
AO or severely compressed A2/AO fractures underwent via
a less invasive posterior approach one-staged reduction
with a novel augmentation implant and PMMA plus
3-vertebrae pedicle screw fixation and fusion. Radiologic
parameters as segmental kyphosis (SKA), anterior (AV-
BHr) and posterior vertebral body height ratio (PVBHr),
spinal canal encroachment (SCE), cement leakage and
functional parameters as VAS, SF-36 were measured pre-
and post-operatively. Hybrid construct restored AVBHr
(P \ 0.000), PVBHr (P = 0.02), SKA (P = 0.015), SCE
(P = 0.002) without loss of correction at an average fol-
low-up of 17 months. PMMA leakage occurred in 3
patients (3 vertebrae) either anteriorly to the fractured
vertebral body or to the adjacent disc, but in no case to the
spinal canal. Two pedicle screws were malpositioned (one
medially, one laterally to the pedicle at the fracture level)
without neurologic sequelae. Solid posterolateral spinal
fusion occurred 8–10 months post-operatively. Pre-opera-
tive VAS and SF-36 scores improved post-operatively
significantly. This study showed that this novel vertebral
augmentation technique using PEEK implant and PMMA
reduces and stabilizes via less invasive technique A2 and
A3 vertebral fractures without loss of correction and leak-
age to the spinal canal.
Keywords Traumatic lumbar fractures � Minimal
invasively � KIVA � Pedicle screw � PMMA
Introduction
Posterior short-segment spinal instrumentation for trau-
matic causes decreases number of immobilized vertebrae,
surgical time, blood loss and pain, while it preserves
motion segments [1]. These benefits allow quicker reha-
bilitation in young adults and are of major importance for
elderly patients because they decrease complications due to
potential medical co-morbidities.
However, a high prevalence of early instrumentation
failure and subsequent progressive loss of intraoperatively
achieved reduction has been reported [2], particularly in
high vertebral body comminution associated with short-
segment pedicle screw instrumentation. The possible
explanation for this failure is that short posterior instru-
mentation alone is not adequate for sufficient anterior
structural spinal support. The fractured vertebral body
cannot heal due to this anterior column insufficiency, and a
supplemental load sharing through anterior column recon-
struction and support should be added.
Combined anterior plus posterior surgery for lumbar burst
fractures, with short pedicle screw fixation and placement of
mesh cage after anterior corpectomy, was associated with
excellent radiologic results. However, the medium-term
clinical results of combined anteroposterior surgery are not
superior to those achieved with short-segment pedicle screw
fixation alone [3]. Furthermore, traditional anterior surgery
in elderly patients with osteoporosis is fraught with com-
plications due to medical co-morbidities.
A sufficient and safe anterior column reconstruction via
a posterior transpedicular approach has been made possible
P. Korovessis (&) � K. Vardakastanis � T. Repantis � V. Vitsas
Orthopaedic Department, General Hospital ‘‘Agios Andreas’’
Patras, Charalambi Str. 65-67, Patras, Greece
e-mail: korovess@otenet.gr
123
Eur J Orthop Surg Traumatol
DOI 10.1007/s00590-013-1339-2
in the recent few years, thanks to the development of
transpedicular, inflatable balloons, implantable stents or
other reinforcement devices [4] combined with injectable
PMMA and bone substitutes. Thus, risks associated with
anterior surgery have been diminished.
However, some serious complication (lung embolism,
cement leakage, etc.) associated with bone cement injec-
tion has been reported in balloon kyphoplasty (BK) and
vertebroplasty (VP). Despite the fact that use of BK has
become more prevalent, the occurrence of cement leakage
remains a small yet significant problem with rates ranging
from 7.0 to 10 % [4, 5].
The hypothesis of this study is that a novel vertebral
body augmentation implant (KIVA) with PMMA, along
with short pedicle screw fixation and posterolateral fusion,
would provide and maintain short-term reduction and sta-
bilization of fresh traumatic lumbar fractures in young
adults, with reduced PMMA leakage.
Patients and methods
A consecutive series of 20 patients (11 women, 9 men),
suffering from one-level lumbar (L1–L4) fresh traumatic
burst (AO/A3 type) or severely compressed (AO/A2 type)
fracture, were included in the study. The average age of the
patients was 45 ± 11 years at surgery (range 25–61). The
exclusion criteria were as follows: osteoporotic fractures,
polytraumatized patients, pre-existed spinal deformity,
malignancy, history of vertebral fracture in the same or
adjacent vertebrae and previous spinal operation. Eligible
patients were required to sign an informed consent form,
and the internal review board approved this study.
All patients were evaluated both clinically and radio-
logically and were treated operatively within 24 h follow-
ing trauma. Non-serious associated injuries were recorded
in 3/20 patients. Neurologic examination was made on
admission in each patient using a rating system based on
the American Spine Injury Association (ASIA) impairment
scale [6] (Table 1). Back pain intensity was recorded on
VAS (10-point scale). Functional outcome was measured
using the SF-36 questionnaire (role physical and bodily
pain domains). On admission, there were 2 patients with
incomplete paraplegia: one with ASIA grade C, and one
with ASIA Grade D, while the remaining patients were
ASIA E [6].
Pre-operative imaging assessment was performed using
plain films, computed tomography (CT) and/or MRI. There
were 15 type A3 with load-sharing score (LSS) [7] C6
(Table 2) and 5 type A2 fractures. All patients were post-
operatively followed, by standing anteroposterior and lat-
eral roentgenograms of the whole spine. Supine oblique
roentgenograms and sitting lateral flexion–extension
roentgenograms as well as CT-scans, including sagittal
reconstruction images and axial views, were made
8 months post-operatively to assess spinal fusion. Two
independent senior orthopaedic radiologists were asked to
evaluate the evolution of the intertransverse bony fusion
after surgery with the Christiansen’s radiologic method [8].
The observers re-evaluated the plain roentgenograms
within 3 weeks to test interobserver reliability.
The well-established radiographic variables which were
evaluated on plain radiographs on admission and post-
operative were as follows: Gardner segmental kyphotic
deformity (SKA = angle formed from the lines drawn on
the lower endplate of the fractured and the upper endplate
of the above adjacent vertebrae), anterior vertebral body
height ratio (AVBHr) and posterior vertebral body height
ratio (PVBHr). Spinal canal encroachment (SCE) was also
measured in axial CT views.
Patients were encouraged to walk wearing a 3-point
fixation brace on the following day after surgery for
4 weeks.
Statistical analysis was performed with Chi-squared test
for non-parametric data comparisons, paired/unpaired t test
Table 1 ASIA (American Spinal Injury Association) classification of
Spinal Cord Injury (SCI) [5]
Category Motor function Sensory
function
Level
A = complete
SCI
No No S4–S5 includeda
B = incomplete
SCI
No Yes Below the
neurologic level
of the damage,
S4–S5 level
included
C = motor
incomplete
SCI
Yes, more than
half of key
musclesb have a
muscle grade
\3/5
Below the
neurologic level
of the damage
D = motor
incomplete
SCI
Yes, at least half
of the key
musclesb have a
muscle grade
[3/5
Below the
neurologic level
of the damage
E = normal Normal Normal
a The anal sphincter is innervated by the S4–S5 cord and is a critical
part of the spinal cord injury examination. If the person has any
voluntary anal contraction, regardless of any other finding, that person
is by definition a motor incomplete injuryb Arm and hand key muscles: elbow flexors (biceps), wrist extensors,
elbow extensors (triceps), finger flexors and little finger abductor
(outward movement of the pinky finger). Leg and foot key muscles:
hip flexors (psoas), knee extensors (quadriceps), ankle dorsiflexors
(anterior tibialis), long toe extensors (hallucis longus) and ankle
plantar flexors (gastrocnemius)
Eur J Orthop Surg Traumatol
123
for changes of each radiographic parameter and correlation
coefficient (R) for comparison changes of different
parameters.
Surgical technique
All patients were operated under general endotracheal
anaesthesia, by a senior orthopaedic surgeon (first author)
and continuous intraoperative neuromonitoring and image
intensifier.
Pedicle screws were inserted in the two non-fractured
adjacent vertebrae above and below the fracture. The
fractured vertebra was reduced and augmented with the
KIVA implant and PMMA. Intermediate short screws were
added afterwards in the fractured vertebra to complete the
hybrid construct.
A targeting cannulated needle (Abbot, Austin, TX,
USA) is inserted in each pedicle (Fig. 1a). Then, 2-mm K-
wires are passed through the cannulated needle. A straight
short paramedian skin incision connecting the entry points
of the K-wires on each side is made (Fig. 1b) and followed
by a fascial incision. The plane between multifidus and
longissimus muscles was identified (Fig. 1c) [9]. Blunt
dissection of the intermuscular plane between multifidus
and longissimus with the index fingers down to the facet
joints. Using the K-wires as guide, 4 multiaxial fully
cannulated pedicle screws (5.5–7.5 mm, Pathfinder, Abbot,
Austin, TX, USA) with extender sleeves on are placed
down into the pedicles (Fig. 1).
The vertebra augmentation was subsequently performed
unilaterally with the KIVA device (Benvenue Medical,
Santa Clara, CA, USA) [10] and low-viscosity PMMA. The
KIVA system is a sterile, single-use device in which an
external delivery handle is used to deploy the PEEK implant
over a ninitol coil guidewire. The coil is first advanced
through the deployment cannula into the cancellous portion
of the vertebral body. The KIVA implant, which is
comprised of PEEK–OPTIMA (Invibio Inc., West Cons-
hohocken, PA, USA), is incrementally advanced over the
coil to form a nesting, cylindrical column with an in situ outer
diameter of 20 mm. Up to four loops of the implant may be
inserted into the vertebral body for a maximum coil stack
height of 12 mm. This cylindrically shaped PEEK implant
re-elevates the endplate, thereby providing desired sufficient
vertebral endplate reduction. After the coil is retracted,
radiopaque PMMA cement (usually 1–2 cc, depending on
the number of PEEK loops inserted) is injected through the
lumen of the PEEK implant, thereby interlocking the implant
to the vertebral body cancellous bone. Additionally, the
injected PMMA into the PEEK implant creates a uniform
cylindrical column in the anterior and partially middle ver-
tebral column (Figs. 2d, 3d). PEEK cylinder safeguards
PMMA containment and has been shown to significantly
reduce cement leakage [10].
Immediately, after PMMA injection, a 35-mm-long
cannulated 5.5-mm pedicle screw (Pathfinder, Abbot,
Austin, TX, USA) is inserted into each pedicle of the
augmented vertebra. Two rods, after appropriate rod-length
selection and contouring, are then inserted through the
screw extender sleeves (Fig. 1d). Reduction of the rods into
the screw tulips is finally done using forceps reducer. Facet
joints and transverse processes are exposed out with Cobb
elevator, and bone graft substitute is applied. No drain was
applied in any patient since there was no visible bleeding
during wound closure.
Results
The operative time averaged 40 min (range 30–50 min).
The volume of injected PMMA was 1.5 cc (range
1–2 cc).
The total blood loss was 45 mL (range 30–105 mL).
The hospital stay averaged 2 days (range 1–3 days).
Table 2 Load-sharing classification (LSC) of spine fractures [6]
Factors Points
1 2 3
Communition on sagittal plane
section CT
Little B 30 % Medium = 30–60 % Gross C 60 %
Apposition of fragments on axial
CT cut
Minimal Spread = at least 2 mm displacement of
\50 % cross section of body
Wide = at least 2 mm displacement of
[50 % cross section of body
Reducibility of sagittal
deformation on lateral plain films
Kyphotic
correction B
3�
Kyphotic correction 4�–9� Kyphotic correction C 10�
The load-sharing classification grades the extent of vertebral body comminution, the amount of fracture displacement and the amount of
correction of kyphotic deformity
Total load-sharing score (LSS) is the sum of the points of the three factors
Eur J Orthop Surg Traumatol
123
All patients were followed for 17 months (range
12–22 months).
Radiologic results (Table 3)
Pre-operative SKA and AVBHr were correlated signifi-
cantly (r = -0.77, P \ 0.001).
Hybrid fixation reduced pre-operative SKA value at
5� ± 4� (P \ 0.000).
Spinal canal encroachment (SCE) was reduced follow-
ing surgery at an average 78 % (P = 0.02).
No measurable loss of correction in SKA, AVBHr,
PVBHr and SCE was identified at the latest observation
after surgery.
Oblique/bending radiographs and CT-scans taken
8–10 months post-operatively showed solid posterolateral
fusion, bone healing within the fractured vertebral body,
and bridging bone trabeculae around the PMMA–PEEK–
PMMA cylinder (Fig. 2d). The average radiographic score
Fig. 1 Pathfinder technique: a targeting cannulated needles. b Short paramedian skin incision connecting the entry points of the K-wires.
c Splitting of the fascia and identification of the plane between the multifidus and the longissimus muscles. d Schematic representation of the
pathfinder device in situ with the precontoured longitudinal rod being implanted
Fig. 2 a Lateral CT-scan image of a 46-year-old man with a burst A3
fracture of L2 vertebra and neurologic impairment. b Axial CT-scan
showing spinal canal encroachment. c Lateral-standing roentgeno-
gram 8 months post-operatively showing excellent restoration of the
anterior and posterior vertebral height with well-positioned PEEK
implant and PMMA containment. d Post-operative axial CT-scan
image showing excellent PMMA containment, spinal canal clearance
and fusion of the posterior elements
Eur J Orthop Surg Traumatol
123
regarding dorsolateral and intertransverse fusion according
to the Christiansen’s radiologic method [5] was 2.7 (range
2–3).
Additionally, the axial CT-scan images revealed a
remarkable containment of PMMA within the constructed
PEEK-cement cylinder.
Functional results
Pre-operative low back pain VAS score of 7.2 ± 3
improved post-operatively to 2.6 ± 2 (P \ 0.002). No
further significant changes in VAS score were reported
thereafter.
Role physical (SF-36) improved from 38 ± 17 (aver-
age ± SD) before surgery to 77 ± 18 after surgery
(P \ 0.001), and the domain bodily pain (SF-36) from
22 ± 10 (average ± SD) before surgery to 81 ± 13 after
surgery (P \ 0.001), at the 6 months follow-up. No further
changes in both SF-36 domains scores were reported in
both groups.
Both patients with incomplete neurologic impairment on
admission improved after surgery from ASIA C & D to
ASIA D & E, respectively. They both had a severely
comminuted fracture (LSS score 8 and 7, respectively) with
great canal encroachment ([30 %) in which post-operative
had a spinal canal clearance of 80 % (Fig. 2).
Complications
No intraoperative hypotension, cardiogenic side-effects, or
pulmonary embolism were clinically recorded.
In 3 patients, bone cement leakage was documented on
CT-scan after surgery, anteriorly to the augmented verte-
bral body and into the adjacent disc (Fig. 3b), without any
sequelae. All these fractures were A3/AO type with severe
comminution (LSS score [7] 7,8) (Fig. 3).
In two obese patients, 2 pedicle screws were misplaced;
one medially and one laterally without, however, clinical
sequelae (Fig. 3d).
No patient deteriorated neurologically after surgery. No
implant failure was observed in any case.
In the short-term follow-up evaluation, no adjacent new
vertebral fractures were observed.
Discussion
The hypothesis of this study was justified by the achieved
clinical and radiologic results associated with the hybrid
fixation of fresh lumbar vertebral fractures: the novel
KIVA implant with PMMA reduced and simultaneously
reinforced the fractured vertebral body immediately after
PMMA hardening thus restoring both anterior and posterior
vertebral body height and simultaneously reduced post-
Fig. 3 a Supine lateral roentgenogram of 67-year-old male patient
who sustained a L3 type A3 fracture after fall from a height. There is
loss of segmental lordosis; b Lateral-standing roentgenogram
6 months following KIVA plus short fixation. The segmental lordosis
is well restored following KIVA implantation; c Pre-operative axial
CT showing a comminution of the vertebral body associated with
spinal canal encroachment; d Axial CT-scan 6 months following
hybrid surgery showing spinal canal clearance and sufficient PMMA
containment. Note the spinal canal clearance
Table 3 Radiologic data pre-to post-operatively in 20 patients with
lumbar fractures
Pre-
operative
Post-
operative
P value Change %
AVBHr 0.66 ± 0.17 0.85 ± 0.13 0.000027 37.3 ± 35.5
PVBHr 0.88 ± 0.1 0.94 ± 0.05 0.02 10.1 ± 13.8
SKA 11.2 ± 7.2 6 ± 4.7 0.015 51.4 ± 24
(5.38� ± 4.2�)
SCE 30.7 ± 28.5 11.8 ± 17 0.02 78 ± 23 spinal
canal clearance
All values are shown as average ± standard deviation
AVBHr anterior vertebra body height ratio, PVBHr posterior vertebra
body height ratio, SKA segmental kyphosis angle, SCE spinal canal
encroachment
Eur J Orthop Surg Traumatol
123
traumatic kyphosis. The segmental short pedicle screw
construct finally safeguarded the long-term stability and
maintained the intraoperatively obtained correction.
Similar results with us were reported in comparable
historical series with open and percutaneous approach [10–
15]. The immediate spinal stability, particularly in A3-type
fractures, provided by the hybrid KIVA construct, allowed
for early and safe mobilization of our patients, thus
reducing any immobilization-related complications.
Balloon kyphoplasty (BK) and VP procedures may be
associated with PMMA extravasation [16, 17] that could
result in pulmonary embolism, deep-seated infection, post-
procedure acute respiratory distress syndrome, palsy and
death [18–21]. None of these complications occurred in our
patients.
Our explanation regarding the efficacy of the PEEK
implant in vertebral body reduction and maintenance of
achieved reduction and the role of the PMMA in support-
ing the vertebral body, without significant cement leakage,
speculated the following: the controlled PMMA injection
into the PEEK cylinder reduced cement leakage [22]. In
Kyphoplasty, after balloon deflation, some void collapse
may occur, and PMMA leakage may occur since there are
no bony boundaries to create a safe nest for PMMA within
this void [23]. In contrary, the PEEK–PMMMA construct
holds the achieved correction immediately after its
implantation. This PEEK column limits the rate of cement
leakage. Extracanal PMMA leakage was reported as high
as 25 %, following short pedicle screw fixation combined
with BK for thoracolumbar burst fractures [8]. In our ser-
ies, extracanal cement leakage was evident just in 3 of 20
cases (15 %) without any clinical sequelae.
There is some controversy as if a posterolateral fusion is
necessary additionally to short pedicle screw fixation and
vertebral augmentation for thoracolumbar A3 fractures [10,
11, 13, 22–24]. A recent study [24] compared on a pro-
spective basis two series of patients operated with posterior
short-segment fixation with/without addition of iliac bone
graft and postulated that fusion is not necessary. In con-
trary, another study [11] compared short-segment pedicle
screw fixation with/without fusion for A3 burst fractures
with LSS \6 and reported equally good results. In all 20
patients included in our study, the addition of posterolateral
fusion to short instrumentation was justified because there
were 15 type A3 with LSS C6 and 5 type A2 fractures with
severe compression. The lack of instrumentation failure
until the final short-term observation justified our decision
for additional posterolateral fusion in these fractures.
The reported kyphosis correction with transpedicular
augmentation (bone, bone graft substitute, PMMA, tita-
nium spacer, hydroxyapatite sticks) and short pedicle fix-
ation techniques ranged from 64 to 105 % [10–13, 25]. In
our study, the post-operatively achieved Gardner kyphosis
correction of 51 % was less than that of previously
reported because in those studies, either solid grafts (tita-
nium block, HA stick) or BK was used. Furthermore, the
method used for kyphosis measurement was not clearly
described in those articles.
Following transpedicular vertebral body grafting, spinal
canal clearance averaged 65 % [10–13, 25] and this was
mostly due to bone remodelling with the time lapsed from
index surgery. In our series, the spinal canal clearance
following vertebral fracture reduction and vertebral aug-
mentation was 78 %, and this depicts the stable fixation
achieved by the hybrid construct.
Our study, in accordance with a previous similar [9] one,
clearly showed the unique advantage of KIVA to safely
reduce not only severely compression fractures but also
burst fractures with moderate SCE and LSS C6.
There is some controversy regarding bone displacement
following vertebral body augmentation. Some anterior bone
displacement (at both thoracic and lumbar level) and pos-
terior bone displacement (at thoracic level) can occur after
inflation of balloons in burst fractures treated with balloon
VP and pedicle screw instrumentation [26]. The absolute
amount of posterior bone displacement is probably not of
clinical relevance [26]. In contrary, a cadaveric study [26]
showed that BK after pedicle screw instrumentation may
safely be used, in terms of bone displacement and cement
leakage, even in fracture types where damage to longitudinal
ligaments is to be expected. In our study, KIVA PEEK [10]
implant was introduced via a coil within the crushed can-
cellous bone of the vertebral body elevating the endplate
without simultaneously pushing bone fragments posteriorly
to the spinal canal [10]. Anterior or most importantly pos-
terior to the spinal canal vertebral body displacement was not
measured even in A3 fractures in our series.
Furthermore, the use of two intermediate screws at the
level of KIVA implantation was proved in this series to be
safe without retropulsion of the fragments into the canal.
The latter is in accordance with the previous relative lit-
erature [9, 27].
No instrumented released distraction was necessary to
reduce post-traumatic kyphosis because as it was previ-
ously shown the local post-traumatic kyphosis in fresh
lumbar fractures is corrected combined by positioning of
the patient on the frame and the action of KIVA [10].
Although serious drawbacks associated with the long-
term results after use of PMMA in cemented total joint
arthroplasties have been reported, the complications with
the use of PMMA in kyphoplasty and VP focus solely on
cement leakage. Self-hardening calcium phosphate bone
cements have been developed as an alternative to overcome
the short-term and possible long-term side-effects of
PMMA [9]. Marco et al. used PMMA in patients with age
ranged from 15 to 73 years and reported no side-effects up
Eur J Orthop Surg Traumatol
123
to 55 months after index surgery [28]. However, the long-
term side-effects of the use of PMMA in spines of young
adults, to our knowledge, have not yet been studied.
Although minimal invasive techniques reserve back
muscles, they may be associated with disastrous neurologic
complications. A CT study disclosed on axial post-opera-
tive CT views a 23 % pedicle penetration rate with 3.3 %
severe frank screw penetration. Others recently showed
that percutaneous placement of pedicle screws was asso-
ciated with 14 % misplacement in normal weight versus
22.6 % in overweight patients [29]. In our series, 3 of 120
screws were medially misplaced on post-operative CTs
without, however, any clinical complaints. In accordance
with the published literature [29], all malpositioned screws
in our series occurred in overweighed patients.
The rate of new adjacent and remote vertebral fractures
following BK and pedicle screw fixation is reported up to
18.8 %, depending on the duration and nature of the follow-
up [25]. No short-term adjacent fractures were observed in
our series. We speculate that the reason of lack of new
fractures was the reduction in mechanical stresses through
the sufficient restoration of vertebral body height and local
kyphosis and the supplementary use of instrumentation.
Following restoration of collapsed vertebral body, mainte-
nance of as many as possible free motion segments could be
the ideal surgical goal. However, loss of correction has been
reported after hardware removal because the correction loss
often occurs primarily through disc space collapse. [30–32]
Furthermore, degeneration of the facet joints within the
immobilization area may occur [30–32].
The limitations of this study were as follows: its retro-
spective nature and the lack of studies regarding the long-
term effects of PMMA in spine of young patients. Since
extracanal PMMA leakage in our series occurred solely in
A3 fractures, this kind of fractures may be a potential
theoretical limitation for KIVA augmentation [4, 5].
Although the short-term clinical and radiologic results
of this comparative study are promising, clinical and
radiologic studies with longer observation periods and
comparisons with conservatively treated patient series are
required to support the longevity of this novel method of
hybrid fixation.
Conflict of interest The authors of the present study received no
external funding resources, either directly or indirectly, in order to
complete the present work. No other relationships/conditions/cir-
cumstances that present a potential conflict of interest exist.
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