ORIGINAL RESEARCH
SPINE
Spinal Instrumentation Rescue with Cement Augmentation
X A. Cianfoni, X M. Giamundo, X M. Pileggi, X K. Huscher, X M. Shapiro, X M. Isalberti, X D. Kuhlen, and X P. Scarone
ABSTRACT
BACKGROUND AND PURPOSE: Altered biomechanics or bone fragility or both contribute to spine instrumentation failure. Although
revision surgery is frequently required, minimally invasive alternatives may be feasible. We report the largest to-date series of percutaneous fluoroscopically guided vertebral cement augmentation procedures to address feasibility, safety, results and a variety of
spinal instrumentation failure conditions.
MATERIALS AND METHODS: A consecutive series of 31 fluoroscopically guided vertebral augmentation procedures in 29 patients were
performed to address screw loosening (42 screws), cage subsidence (7 cages), and fracture within (12 cases) or adjacent to (11 cases) the instrumented segment. Instrumentation failure was deemed clinically relevant when resulting in pain or jeopardizing spinal biomechanical stability. The
main study end point was the rate of revision surgery avoidance; feasibility and safety were assessed by prospective recording of periprocedural
technical and clinical complications; and clinical effect was measured at 1 month with the Patient Global Impression of Change score.
RESULTS: All except 1 procedure was technically feasible. No periprocedural complications occurred. Clinical and radiologic follow-up was
available in 28 patients (median, 16 months) and 30 procedures. Revision surgery was avoided in 23/28 (82%) patients, and a global clinical benefit
(Patient Global Impression of Change, 5–7) was reported in 26/30 (87%) cases at 1-month follow-up, while no substantial change (Patient Global
Impression of Change, 4) was reported in 3/30 (10%), and worsening status (Patient Global Impression of Change, 3), in 1/30 (3%).
CONCLUSIONS: Our experience supports the feasibility of percutaneous vertebral augmentation in the treatment of several clinically
relevant spinal instrumentation failure conditions, with excellent safety and efficacy profiles, both in avoidance of revision surgery and for
pain palliation.
ABBREVIATIONS: PGIC ⫽ Patient Global Impression of Change; PMMA ⫽ polymethylmethacrylate
pinal instrumentation is widely used in the treatment of degenerative, traumatic, and neoplastic conditions. Altered biomechanics and/or bone fragility may lead to instrumentation failure, bone resorption, or new fractures with consequent instability
and recurrent or progressive pain.1,2 The most commonly encountered types of instrumentation failure are implant fracture or
S
Received May 21, 2018; accepted after revision July 23.
From the Departments of Neuroradiology (A.C., M.P., M.I.) and Neurosurgery (M.G.,
D.K., P.S.), Neurocenter of Southern Switzerland, Ente Ospedaliero Cantonale, Lugano, Switzerland; Department of Neurosurgery (K.H.), Hôpital du Valais, Sion,
Switzerland; Department of Radiology (M.S.), New York University Langone Medical Center, New York, New York; and Department of Neuroradiology (A.C.),
Inselspital, Bern, Switzerland.
Please address correspondence to Alessandro Cianfoni, PD, MD, Department
of Neuroradiology, Neurocenter of Southern Switzerland, Ospedale Regionale
di Lugano, Via Tesserete 46, 6900 Lugano, Switzerland; Department of Neuroradiology, Inselspital, Freiburgstrasse 18, 3010 Bern, Switzerland; e-mail:
alessandro.cianfoni@eoc.ch
Indicates article with supplemental on-line table.
http://dx.doi.org/10.3174/ajnr.A5795
disassembly, bone resorption around the screws, or impaction
fracture adjacent to an implanted cage.1 In addition, vertebral
insufficiency fractures can occur within the instrumented segment or at adjacent levels (junctional fractures). In many instances described above, revision surgery is performed,3 with the
potential of further morbidity, increased cost, and reduced patient satisfaction. Re-operation is often an unattractive option in
elderly, medically complex, and fragile patients.
Minimally invasive options would be desirable to address instrumentation failure. Vertebral cement augmentation is used in
the treatment of painful osteoporotic and tumor-related compression fractures.4-7 Numerous reports also document the
utility of polymethylmethacrylate (PMMA) to augment pedicular screws at the time of insertion.8-12
To date, several small series have described the use of cement
augmentation in implant failure, including junctional fractures
and screw loosening, both in osteoporotic13-15 and neoplastic
settings.16,17
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the study was approved by the Comitato
Etico Cantonale del Ticino institutional
ethics committee.
Indications for primary spinal instrumentation included a variety of traumatic,
degenerative, and neoplastic conditions.
Indications for cement rescue treatment
were the following: clinically relevant
screw loosening with bone resorption,
cage subsidence, and vertebral fracture
within or adjacent to the instrumented
segment. Instrumentation failure was
deemed clinically relevant if accompanied by new or recurrent pain correlated
with imaging findings or deemed to be a
threat to spinal biomechanical stability.
Determination of implant failure, the
decision to offer treatment, and the
treatment approach were based on case
review by the Spine Unit staff of our institution, composed of neurosurgeons,
neurologists, neuroradiologists, pain
physicians, and physical medicine and
rehabilitation physicians. All patients
underwent preprocedural noncontrast
CT in addition to pre-existing imaging
studies. Patients with uncorrectable
coagulopathy and local or systemic infection were excluded.
Cement-Augmentation Procedure
Procedures were performed with the patient under moderate sedation and local
anesthesia. A single dose of prophylactic
intravenous antibiotic (cefazolin, 2 g)
FIG 1. Schematic representation of different access approaches to the instrumented vertebra. A, was administered 1 hour before the proAxial CT image of a vertebra instrumented with bilateral pedicular screws. Yellow arrows represent transpedicular access, with a thin, flexible, beveled needle contacting the proximal screw cedure. All procedures were performed
shaft, then bending and sliding along the screw shaft. The red arrow represents transpedicular under fluoroscopic guidance in a monoaccess targeting the tip of the screw, with a slightly more oblique course than the screw path. The or bi-plane angiosuite. A variety of apdashed blue arrow represents extrapedicular access targeting the anterior third of the vertebral
proaches to the target vertebral body
body along the midline, crossing the course of the screw at the level of posterior wall with an
obliquity from lateral to medial. B and C, Volume-rendered CT lateral and posteroanterior views were used (Fig 1) to overcome access
of an instrumented spine segment. Red arrows in B and C show transpedicular access parallel to constraints posed by the presence of imthe screw used to augment loose screws, while dashed arrows represent extrapedicular accesses
plants. Vertebroplasty 15-ga bevel-tip
to the vertebral body used to augment vertebral body fractures, coursing lateral to medial to the
screw, traversing the screw course from cranial to caudal (blue dashed arrows) or from caudal to trocars were inserted via a transpedicucranial (green dashed arrow), respectively, passing cranial or caudal to the transverse process.
lar or extrapedicular approach to reach
the desired target location, and high-visWe report the largest and most encompassing series to date of
cosity PMMA cement (VertaPlex HV; Stryker, Kalamazoo, Michpercutaneous fluoroscopically guided vertebral cement augmenigan) was injected under real-time fluoroscopic control. Postprotation in a variety of clinically significant instrumentation failure
cedural target-level CT was performed. Patients were mobilized
conditions, including screw loosening, cage subsidence, and verimmediately following recovery from moderate sedation. Most
tebral fractures within or adjacent to the instrumented segment.
patients were discharged the same day.
MATERIALS AND METHODS
A retrospective analysis of 31 consecutive procedures in 29 patients (male/female, 10:19; mean age, 71.6 years; range, 50 – 82
years) with instrumentation failure treated by percutaneous cement augmentation between May 2013 and October 2016 was
performed. Informed consent was obtained from all patients, and
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Vertebral Body Access
Transpedicular Approach. An access trajectory parallel to the
screw was used for treatment of screw loosening. An en face view
of the screw was obtained as a “bull’s eye” projection, the fluoroscopic camera was then angled slightly toward the side of the
dle position was targeted as discussed
in the transpedicular section above. For
instrumented-level fractures, the approach was to cross the path of the screw at
the junction between the pedicle and vertebral body, from lateral to medial, and
cranial or caudal to the screw, depending on target fracture location (Fig 3).19
In case of access to the vertebral body
without pedicular screws, a standard approach was used, with only necessary
adjustments to avoid the vertical rods.
Injection of high-viscosity PMMA
cement was performed under real-time
high-resolution fluoroscopic control,
predominantly in the lateral view, with
intermittent anteroposterior or oblique
control views.
In case of screw loosening (Fig 2), cement injection was aimed at filling the
halo of bone resorption around the screw,
to simulate screw oversizing, and reducing
or nulling screw micromobility. Whenever possible, the adjacent trabecular network was also filled with cement in an effort to achieve a more stable anchoring
cast between the screw and the vertebral
FIG 2. Cement augmentation of bilateral S1 screw loosening. A–C, Multiplanar preprocedural CT body. In case of vertebral fracture, cement
shows circumferential osteolysis around the screws in S1. Frontal (D) and lateral oblique views (E)
of S1 screws, with bilateral placement of needles along the screws and the needle tip in bone injection was aimed at filling, with a traosteolysis around the screw. F–H, Fluoroscopic and CT MIP images post-cement augmentation, becular interdigitation pattern, the antedemonstrating optimal filling of the osteolytic area (arrows), acting as screw oversizing, and rior two-thirds of the vertebral body, from
potentially reducing hypermobility. I, Follow-up CT 3 months postaugmentation shows stable
superior to inferior endplates on both
results in this patient reporting clinical amelioration.
sides of the midline. In case of cage subsidesired modified access, and the proximal or midportion of the
dence, cement injection was aimed at augmenting the bone-metal
screw was set as the target. With use of a 15-cm 15-ga beveled-tip
interface and arresting bone compaction (Fig 3).
vertebroplasty needle, contact with the midshaft of the screw was
obtained and the flexible needle was pushed to slide with the bevel
Follow-Up
along the distal shaft of the screw, maintaining the needle tip
Patients were followed 1 month after the procedure with a clinical
position inside the bone resorption halo. Alternatively, the tip of
visit and standing plain films; when deemed necessary, CT or MR
the screw was set as the fluoroscopic target on the en face view and
imaging was performed. Clinical and imaging follow-up was conaligned with a transpedicular access route a few millimeters away
tinued at variable intervals, depending on the clinical situation
from the screw.
and the referring physician’s preference.
For access to instrumented level fractures (rather than loosening), a trajectory crossing from lateral to medial and from cranial
Study End Points
to caudal relative to pedicle screw was usually chosen. In this case,
Study end points were feasibility, safety, and efficacy. Feasibility
the fluoroscope was angled from the bull’s eye view of the screw
and safety were assessed by review of chart records and periproslightly laterally and cranially. Whenever the needle contacted a
cedural complications; efficacy was based on the rate of revision
screw, appropriately turning the bevel would allow the needle to
surgery, while the clinical effect on pain was measured at 1-month
slide past the screw and continue forward progress to reach the
follow-up. The Patient Global Impression of Change (PGIC)
desired target in the vertebral body.
7-point response was scored as follows: 1, extremely worse; 2,
much worse; 3, a little worse; 4, no change; 5, a little better; 6,
Extrapedicular Access. In general, we thought that small-caliber,
much better; and 7, extremely better.20
straight anteroposterior, and steep craniocaudal orientation of
mid and upper thoracic pedicles favored an extrapedicular approach between the pedicle and the rib head.18 The access trajectory could be slightly lateral and cranial to the screw and then
parallel to the screw, exploiting the bevel design and flexibility of
the access needle. For loose screw indications, a similar final nee-
RESULTS
The On-line Table summarizes the results.
In 31 procedures, performed in 29 patients (2 patients underwent 2 procedures), 42 loose screws, 7 levels with cage subsidence,
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FIG 3. Cage subsidence/fracture and multiple targets. A and B, CT images of an L1 fracture
treated with corpectomy, cage grafting, and T11–L3 posterior stabilization in a patient with osteoporosis. Due to bone compaction/fracture cranial and caudal to the cage, there is cage
subsidence and focal kyphosis (arrows in B). Another fracture is noted at T11 (arrowhead in B), and
there is bone resorption and screw loosening at L3 (not shown), with initial screw pullout. C and
D, Anteroposterior and lateral fluoroscopy views after placement of multiple needles to perform
cement augmentation at the cranial and caudal bone-metal cage interface in T12 and L2 (arrowheads), in the T11 fracture (arrow), in L3 (arrow) to augment the screw osseous purchase, and in T10
to perform prophylactic augmentation (arrow). E, Postprocedural sagittal MIP CT image demonstrates satisfactory cement filling of the target levels. F, Standing plain film at 12-month follow-up,
with stable results.
12 vertebral body fractures at levels within the instrumented segment, and 11 fractures at levels adjacent to the instrumented segment (junctional fractures) were treated. In addition, prophylactic cement augmentation was performed at nonfractured adjacent
levels in 9 cases with the intent of preventing subsequent junctional fractures in patients with osteoporosis when focal kyphosis
was noted at the junctional level. In some patients, during the
same procedure, distant vertebral or sacral fractures were also
treated with cement augmentation. Prophylactic and distant site
augmentation was not included in analysis.
In all 32 thoracic, 24 lumbar, 13 sacral, and 3 pelvic (iliac
screws) targets, a total of 72 targets, were treated.
The mean interval between the last spinal instrumentation and
the procedure was 14 months (range, 1 week to 11 years; median,
4.5 months).
All except 1 procedure was technically feasible and successfully
accomplished (ie, satisfactory fluoroscopic target visibility, needle
placement, and cement injection). One procedure was aborted
due to access failure caused by implant-related inability to
visualize fluoroscopic landmarks. No periprocedural minor or
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major complications21 occurred; specifically, there were no neurologic complications or clinically significant PMMA
leaks. Clinical and radiologic follow-up
at 1 month was available in 28 patients;
extended follow-up ranged from 2 to 54
months (median, 16 months; interquartile range, 14.7 months). Specifically, follow-up was available at 1 month in 28
patients, at 3 months in 26, at 6 months
in 24, and beyond 12 months in 18. One
patient was lost to follow-up.
During the follow-up period, 5/28
(18%) patients required revision surgery: The patient whose procedure was
aborted due to access failure underwent
revision surgery with replacement of a
loose screw; another patient developed
re-fracture and kyphosis despite cement
augmentation of a junctional fracture
requiring extension of instrumentation.
Three patients underwent implant removal. In 1 of these 3 patients, instrumentation failure was ultimately due to
a low-grade chronic infection.
In the 28 patients (30 procedures)
with available follow-up, global clinical
benefit (PGIC 5–7) was reported in
26/30 (87%) cases at 1 month after the
procedure (PGIC 7 in 10/26, PGIC 6 in
9/26, PGIC 5 in 7/26), while no significant changes in status (PGIC 4) were
reported in 3/30 (10%) and worsening
status (PGIC 3) occurred in 1/30 (3%)
in the absence of obvious procedural
complications.
DISCUSSION
In this series, minimally invasive fluoroscopically guided percutaneous cement augmentation was associated with successful
avoidance of revision surgery in 82% of patients with screw loosening, cage subsidence, or vertebral fractures within or adjacent to
the instrumented segment. Although limited by the retrospective
study design, we believe that implant failure would have otherwise
led to revision surgery, as discussed in the Spine Unit multidisciplinary review. Technical feasibility was highly satisfactory, with
30/31 procedures executed with the desired technical results.
Safety was excellent, with no periprocedural complications, and
the procedure resulted in significant pain amelioration in 87% of
cases.
Spinal instrumentation performed for degenerative, traumatic, or oncologic diseases that may cause deformity or instability aims at providing stability while osseous fusion develops. Adequate bone quality is of primary importance in this success.
Inadequate fixation and subsequent segmental microinstability
may put the implant at risk of ultimate failure.22 A combination of
factors such as initial or subsequent poor bone density/quality,
instrumentation-induced stress shielding and subsequent disuse
osteopenia, plastic deformation at the bone-metal interface, or
high static stress combined with cyclic loading also contribute to
instrumentation failure.2 These processes are often accompanied
by new or recurrent pain, altered biomechanics, and deformity.
Implant failure can occur at variable time intervals after instrumentation from weeks to years. To interrupt this vicious spiral
and palliate pain, in most cases, revision surgery with screw replacement, cage replacement with the addition of allograft or
other bony substitutes, or instrumentation extension are usually
necessary. All these options carry perioperative risks and morbidity and are sometimes contraindicated by patients’ clinical conditions, posing a therapeutic dilemma; in addition, revision surgery
has an important cost burden.23 While in cases of major instrumentation failure, such as implant fracture or disassembly, open
surgery seems absolutely necessary, in other conditions, there
may be room for a minimally invasive treatment option such as
cement augmentation. This technique, established for the
treatment of vertebral body compression fractures4-7 and used
to reinforce pedicular screws at the time of insertion,8-12 has
been reported in small series and case reports as a potential
solution in case of implant-related vertebral fractures and
screw loosening.13-17
Technical Feasibility and Safety
Despite widespread use of vertebral augmentation, there is a paucity of reports on this technique applied to conditions of instrumentation failure. This might be, in part, related to technical hurdles posed by the presence of implants, skepticism regarding
procedure efficacy, and lack of awareness. The presence of dense
metallic structures sometimes obscures the visibility of known
fluoroscopic landmarks or creates artifacts when CT is used for
guidance. Commonly used access routes to the vertebral body,
namely the transpedicular approach, are often occupied by implants, and the operator is therefore forced to seek other trajectories within narrow anatomic windows. Finally, after the operation, spinal anatomy can be altered by laminectomies and bony
fusion masses.
Both CT and fluoroscopic guidance were described in prior
reports.13-17 We invariably used fluoroscopic guidance based on
careful planning and mandatory preoperative CT. Transpedicular
access was favored in the lumbar and lower thoracic spine, while
an extrapedicular approach was preferably adopted in the mid
and upper thoracic spine. A small-caliber 15-ga beveled-tip vertebroplasty needle was used, allowing steerability and flexibility to
precisely reach targets.
Precise needle positioning, use of high-viscosity cement, and
use of high-quality fluoroscopic imaging equipment might have
contributed to the excellent safety profile of the procedures in our
series. Although not used in this series, intraoperative CT, O-arm
Multidimensional Surgical Imaging System (Medtronic, Minneapolis, Minnesota), or conebeam CT guidance could be implemented to aid needle insertion.13,17 Moreover, when necessary,
injection of cement can be directed by the use of a coaxial curved
cannula.15
Clinical Results
The main clinical objective of this study was to assess the rate of
revision surgery avoidance. In a retrospective study, it is not possible to rule out that in some circumstances, a conservative approach would have been sufficient. Pain palliation was also assessed; however, back pain in this kind of complex patient cohort
is an elusive target: It is indeed rather difficult to definitively attribute new or recurrent symptoms to imaging findings of implant failure. We preferred to use the PGIC scale rather than a
Visual Analog Scale for pain assessment because, in our opinion,
it yields a more global and general assessment of the patient’s
perception of treatment effectiveness. Among patients with available follow-up, the clinical benefit of the procedure was reported
in 26/30 cases. The 1 patient in whom the procedure was aborted
due to access failure reported unchanged clinical status and ultimately underwent revision surgery. Two more patients reporting
a PGIC 4 and 1 patient with PGIC 3 required revision surgery,
while 1 patient reporting initial clinical benefit (PGIC 6) after
augmentation of 2 loose screws and a junctional fracture had a
delayed recurrent collapse of the junctional level and underwent
instrumentation extension. Finally, 1 patient was lost to follow-up
and remained unreachable; this patient might have undergone
revision surgery at another institution.
In our series of 29 patients with implant failure, it was necessary to treat a total of 72 targets, including loose screws, cage
subsidence, and vertebral fractures within or adjacent to the instrumented segment. Our data suggest that an important cause of
implant failure is poor bone quality, a systemic problem leading
to multilevel breakdown (Fig. 3). We therefore stress the extreme
importance of aggressive osteoporosis management in this patient population.24
Infrequently, bone resorption around implants can be caused
by an infectious process. In case of clinical-radiologic suspicion,
biopsies and cultures are recommended before proceeding to cement augmentation. Despite these measures, 1 patient in this series, following revision surgery with implant removal, was diagnosed with a low-grade infection, despite biopsy performed 2
weeks before cement augmentation resulting in cultures negative
for infection. This infection was likely present before cement augmentation. Suboptimal sensitivity of spine biopsies for low-grade
infections remains a challenge in such cases.25,26
Limitations
Major limitations include the retrospective study design and an
intrinsically subjective definition of clinically relevant instrumentation failure. Also recognized is the subjective nature of patient
self-assessment. Although this is by far the largest series of its kind
to date, some conditions such as cage subsidence are infrequent and
considerably more experience is necessary. Given the frequency of
spinal instrumentation surgery, it is likely that percutaneous salvage
options are currently underused; therefore, greater awareness and
prospective investigations are necessary.
CONCLUSIONS
This series supports the feasibility of safe, efficacious, minimally
invasive percutaneous vertebral cement augmentation in the
treatment of clinically relevant instrumentation failure, with an
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excellent safety profile and efficacious clinical results in terms of
pain palliation and avoidance of revision surgery. A larger prospective cohort will be necessary to determine optimal candidates
for this treatment and to provide more generalizable outcome
data.
12.
13.
Disclosures: Dominique Kuhlen—UNRELATED: Board Membership: DePuy Synthes
Advisory Board.* Pietro Scarone—RELATED: Consulting Fee or Honorarium: Depuy
Synthes, Comments: I am a consultant spine surgeon for this company, from which
my institution receives fees*. *Money paid to the institution.
14.
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