Minimally invasive treatment of moderate lumbar spinal stenosis with the superion interspinous spacer.

Abstract

We evaluated the safety and effectiveness of the minimally invasive Superion(®) Interspinous Spacer (VertiFlex, Inc., San Clemente, CA) in patients with moderate LSS.
This single-arm prospective study enrolled 121 patients with moderate LSS between February 2008 and August 2009 and were followed up at 1 (n=111), 3 (n=96), 6 (n=81), and 12 (n=52) months. All patients were treated with the Superion Interspinous Spacer. Main outcomes were back function with the Oswestry Disability Index (ODI), extremity and axial pain severity with an 11-point scale, health-related quality of life with the Physical Component Summary (PCS) and Mental Component Summary (MCS) scores from the SF-36, and adverse events through 12 months.
ODI improved 64% (p<0.001) through 12 months and clinical success was 92%. Extremity and axial pain improved 53% and 49% (both p<0.001), respectively, through 12 months with clinical success of 76% for axial pain and 86% for extremity pain. Health-related quality of life improved 41% for PCS and 22% for MCS (both p<0.001) through 12 months. PCS clinical success was 81% and MCS clinical success was 62% at 12 months. Four (5.9%) explants were performed although 3 were unrelated to the device. Eight procedure-related adverse events, observed in 6 (5.0%) patients, included superficial incision seroma (n=5), minor wound pain (n=2), and infection (n=1).
Preliminary results with the Superion Interspinous Spacer suggest that it is an effective and safe treatment option for patients with moderate LSS who are unresponsive to conservative care.

Full text

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The Open Orthopaedics Journal, 2011, 5, 361-367 361

1874-3250/11 2011 Bentham Open
Open Access
Minimally Invasive Treatment of Moderate Lumbar Spinal Stenosis with
the Superion® Interspinous Spacer
Walter Bini1, Larry E. Miller2,3 and Jon E. Block*,3
1Neurosurgical Division, General Hospital Dubrovnik, Dubrovnik, Croatia
2Miller Scientific Consulting, Inc., 422 Mountain Wasp Drive, Biltmore Lake, NC 28715, USA
3Jon E. Block, Ph.D., Inc., 2210 Jackson Street, Suite 401, San Francisco, CA 94115, USA
Abstract: Purpose: We evaluated the safety and effectiveness of the minimally invasive Superion® Interspinous Spacer
(VertiFlex, Inc., San Clemente, CA) in patients with moderate LSS.
Methods: This single-arm prospective study enrolled 121 patients with moderate LSS between February 2008 and August
2009 and were followed up at 1 (n=111), 3 (n=96), 6 (n=81), and 12 (n=52) months. All patients were treated with the
Superion Interspinous Spacer. Main outcomes were back function with the Oswestry Disability Index (ODI), extremity
and axial pain severity with an 11-point scale, health-related quality of life with the Physical Component Summary (PCS)
and Mental Component Summary (MCS) scores from the SF-36, and adverse events through 12 months.
Results: ODI improved 64% (p<0.001) through 12 months and clinical success was 92%. Extremity and axial pain
improved 53% and 49% (both p<0.001), respectively, through 12 months with clinical success of 76% for axial pain and
86% for extremity pain. Health-related quality of life improved 41% for PCS and 22% for MCS (both p<0.001) through
12 months. PCS clinical success was 81% and MCS clinical success was 62% at 12 months. Four (5.9%) explants were
performed although 3 were unrelated to the device. Eight procedure-related adverse events, observed in 6 (5.0%) patients,
included superficial incision seroma (n=5), minor wound pain (n=2), and infection (n=1).
Conclusions: Preliminary results with the Superion Interspinous Spacer suggest that it is an effective and safe treatment
option for patients with moderate LSS who are unresponsive to conservative care.
Keywords: Interspinous spacer, lumbar spinal stenosis, minimally invasive, Superion.
INTRODUCTION

the lumbar spinal canal and/or the intervertebral foramina
resulting from disc degeneration, bulging of the annulus,
facet joint hypertrophy, and/or thickening of the ligamentum
flavum [1-3], ultimately leading to compression of the neural
and vascular elements in the lumbar spine [4]. Neurogenic
claudication symptoms such as leg pain and/or weakness
during walking result in lower quality of life and impaired
functional capacity [5]. With the aging of the population and
continuing advances in diagnostic imaging capabilities,
lumbar spinal stenosis is becoming more frequently
diagnosed with an estimated prevalence of 2 to 13% [6, 7].
Lumbar spinal stenosis is characterized by narrowing of

pain-relieving and anti-inflammatory medications, physical
therapy, and spinal injections are the first-line treatments for
patients with mild symptoms although long-term success is
marginal, partly because these therapies have no impact on
disease progression [8-10]. Consequently, patients are often
confronted with the dilemma of living with persistent pain
and functional impairment or undergoing invasive surgery,
most commonly laminectomy with or without fusion [11-

Nonsurgical management such as activity modification,

*Address correspondence to this author at Jon E. Block, Ph.D., Inc., 2210
Jackson Street, Suite 401, San Francisco, CA 94115, USA; Tel: (415) 775-
7947; Fax: (415) 928-0765; E-mail: jonblock@jonblockphd.com
13], a procedure associated with substantial cost and
morbidity [14-17]. However, there is no clear treatment
algorithm for patients with moderate lumbar spinal stenosis
who may obtain only partial relief from conservative
measures, but where the severity of symptoms may not
justify undergoing invasive surgery such as laminectomy.

increasingly popular over the past two decades [18] and
represent a viable alternative that addresses this therapeutic
gap. In particular, interspinous process decompression is a
novel procedure that limits back extension at the
symptomatic level by implantation of a spacer between
contiguous spinous processes. This implant offers the
potential to minimize neural injury risk versus alternative
procedures and to preserve anatomical structures, thereby
affording the option of more invasive surgery in the future
should severe symptoms recur. Mid-term results suggest that
interspinous spacers improve patient symptoms [19, 20],
although long-term safety and effectiveness are currently
unknown [21]. The purpose of this study was to evaluate 12-
month clinical outcomes in patients with lumbar spinous
stenosis who were treated with a new, minimally invasive,
interspinous spacer.
Minimally invasive lumbar procedures have become

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362 The Open Orthopaedics Journal, 2011, Volume 5 Bini et al.
MATERIALS AND METHODS
Patients

with lumbar spinal stenosis from Asklepios Krankenhaus
(Seligenstadt, Germany) between February 2008 and August
2009. All patients were treated with the Superion®
Interspinous Spacer (VertiFlex, Inc., San Clemente, CA).
Inclusion criteria for this study included (a) diagnosis of
moderate lumbar spinal stenosis, defined as 25% to 50%
reduction in lateral/central foramen diameter compared to
adjacent levels and radiographic evidence of thecal sac
and/or cauda equine compression, nerve root impingement
by either osseous or non-osseous elements, and/or
hypertrophic facets with canal encroachment, (b) persistent
leg, buttock, or groin pain, with or without back pain, that
was relieved by lumbar flexion, and (c) unsuccessful
conservative treatment for at least 3 months. Exclusion
criteria included (a) axial back pain only, (b) grade II to V
spondylolisthesis, (c) unremitting back pain in any spinal
position, (d) active systemic disease that may affect the
welfare of the patient, (e) vertebral osteoporosis or history of
vertebral fracture, and (f) pregnant or lactating female. The
procedures used in this clinical study were in accordance
with the recommendations of the Helsinki Declaration and
each patient gave written, informed consent before surgery.
This single-arm prospective study enrolled 121 patients
Intervention

that is delivered percutaneously and deployed between the
spinous processes of the symptomatic vertebral levels (Fig.
1a, b). This novel interspinous spacer limits extension at the
symptomatic level while preserving mobility, structural
elements, and alignment.
The Superion device is a single-piece titanium implant

Fig. (1). Superion Interspinous Spacer in situ. (a) A/P view, (b)
lateral view.

the patient lying prone on a radiolucent table with the lumbar
spine in a neutral or slightly flexed position. Under
fluoroscopic guidance or direct visualization, the surgical
level was identified and a 12-15 mm midline incision was
made. The supraspinous ligament was longitudinally
dissected at the symptomatic level and then dilated to ensure
adequate room to maneuver within the interspinous space. A
cannula was inserted over the dilator and proper alignment
and depth were ensured before dilator removal. Next, an
interspinous gauge was inserted through the cannula to
determine proper implant size selection and final midline
positioning was confirmed under fluoroscopy.
The minimally invasive procedure was undertaken with

cannula using a device inserter that loaded, inserted into the
interspinous space via the cannula, and deployed the implant.
Proper device placement was confirmed with fluoroscopy.
Finally, the inserter and cannula were removed and the
incision was sutured in a standard fashion. Proper placement
of the implant is illustrated radiographically in Fig. (2).
The appropriately sized spacer was delivered through the

Fig. (2). (a) A/P and (b) lateral radiographic image showing a
properly placed Superion Interspinous Spacer.
Outcomes

for follow-up visits at 1, 3, 6, and 12 months post-treatment.
Degree of back-specific functional disability was measured
with the Oswestry Disability Index (ODI) (version 2) on a 0
to 100% scale [22]. Extremity and axial pain severity was
Patients were assessed pre-treatment and then returned

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Superion for Lumbar Stenosis The Open Orthopaedics Journal, 2011, Volume 5 363
measured with an 11-point numeric pain scale (0 to 10).
Health-related quality of life was assessed with the SF-36
(version 2) and Physical Component Summary (PCS) and
Mental Component Summary (MCS) scores were recorded
[23]. Safety was assessed by incidence of reported adverse
events (AEs) through the 12-month follow-up period.
Device-related AEs were defined as implant dislodgement,
migration, fracture, or deformation that resulted in clinical
sequelae or revision or explant for any reason.
Data Analysis

(v. 18, SPSS, Inc., Chicago, IL). Continuous data were
reported as mean ± SD and categorical data were reported as
frequencies and percentages. Longitudinal changes in
clinical outcomes were assessed with repeated measures
analysis of variance. The revision rate over the 12-month
follow-up period was estimated with Kaplan-Meier methods.
Clinical success was defined as a ?30% improvement in ODI
[24, 25], ?30% improvement in pain scores [24, 26], ?5.7-
point improvement in PCS [27], and ?6.3-point improvement
in MCS [27], respectively.
Data were analyzed using Predictive Analytics Software
RESULTS

overweight-to-obese, presented with single level disease
(most commonly at L4-L5), and suffered moderate-to-severe
back and/or extremity pain and functional disability at
baseline. Twenty-two (18%) patients presented with
concomitant grade I spondylolisthesis. Mean procedure time
was 1 hour and hospital stay averaged 3 days. Implant size
ranged from 8 to 16 mm with the 12 and 14 mm devices
accounting for 80% of implants (Table 1). At the time of this
analysis, 52 patients had passed the 12-month follow-up visit
window. ODI and pain data were available for 50 of 52
(96%) patients and SF-36 data were available for all patients
(52 of 52).
The typical patient was aged in the upper 50s,
Table 1.

Patient Baseline Characteristics
Characteristic Value
(n=121)
Age, mean ± SD, y 57.9 ± 13.5
Female*, n (%) 60 (52.2)
Body Mass Index†, mean ± SD, kg/m2 29.8 ± 5.0
Treated Level, n (%)
L2 — L3 4 (3.3)
L3 — L4 12 (9.9)
L4 — L5 105 (86.8)
Procedure Duration‡, mean ± SD, h 1.0 ± 0.2
Length of Hospital Stay§, mean ± SD, d 3.4 ± 1.1
Axial Pain Severity Score||, mean ± SD 6.9 ± 1.1
Extremity Pain Severity Score||, mean ± SD 6.6 ± 1.4
Oswestry Disability Index (ODI), mean ± SD, %
*, n=115; †, n=62; ‡, n=110; §, n=102; ||, 11-pt. numeric scale.
60.2 ± 7.9

Back-Specific Functional Impairment

month following treatment (60±8% at pre-treatment to
34±10% at 1 month). Between months 1 and 12, continued
improvements in back function were noted with a 12-month
mean value of 21±14%, representing a 64% (p<0.001)
improvement from pre-treatment levels (Fig. 3). ODI clinical
success at 12 months was 92% (46 of 50) (Fig. 4).
Rapid improvements in ODI were noted in the first

Fig. (3). Improvement in back function through 12 months post-
treatment.

Fig. (4). Back function clinical success rates through 12 months
post-treatment.
Extremity and Axial Pain Severity

to 3.3±1.4 at 1 month and 2.8±1.5 at 12 months, reflecting a
53% overall improvement (p<0.001) (Fig. 5). Extremity pain
clinical success at 12 months post-treatment was 86% (43 of
50) (Fig. 6). Similar improvements were realized in axial
pain with values of 6.9±1.1 at pre-treatment, 3.9±1.2 at 1
month, and 3.4±1.5 at 12 months, which represented a 49%
improvement compared to pre-treatment values (p<0.001)
(Fig. 5). At 12 months post-treatment, 76% (38 of 50) of
patients achieved axial pain clinical success (Fig. 6).
Extremity pain decreased from 6.6±1.4 at pre-treatment

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364 The Open Orthopaedics Journal, 2011, Volume 5 Bini et al.

Fig. (5). Improvement in pain severity through 12 months post-
treatment.

Fig. (6). Pain severity clinical success rates through 12 months
post-treatment.
Health-related Quality of Life

improved as early as 1 month post-treatment with all
domains showing a significant (all p<0.001) improvement
through 12 months post-treatment (Fig. 7). Similar to the
trends observed with ODI and axial and extremity pain
scores, PCS and MCS each significantly improved from pre-
treatment to 1 month with continued improvements observed
through the 12-month follow-up visit (p<0.001) (Fig. 8).
Through 12 months, MCS clinical success was achieved in
62% (32 of 52) of patients while PCS clinical success,
arguably a more clinically important and relevant measure,
was achieved in 81% (42 of 52) of patients (Fig. 9).
Six of eight SF-36 domains (PF, RP, RE, SF, BP, VT)
Adverse Events

patient) through the 12-month follow-up period. Most AEs
were of minor clinical importance and were unrelated to the
procedure or the Superion device. Eight procedure-related
AEs (5 wound complications, 2 reports of pain, and 1
A total of 205 AEs were reported in 121 patients (1.7 per
infection requiring explant on post-treatment day (PTD) 10)
were reported in 6 (5.0%) patients. Four patients (5.9%)
underwent device explant during the 12-month follow-up
period including: (a) an infection-related revision on PTD
10, (b) explant at 2 months due to bulging disk at L3-L4, (c)
explant at 8 months due to osteochondrosis, and (d) explant
at 11 months due to persistent pain. Postoperative
radiographic review noted an incidental case of a slightly
angled, albeit correctly placed, Superion device. The patient
reported no clinical symptoms and received no treatment
associated with this finding.

Fig. (7). SF-36 assessment of quality of life through 12 months
post-treatment.

Fig. (8). Physical Component Summary and Mental Component
Summary score improvement through 12 months post-treatment.

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Superion for Lumbar Stenosis The Open Orthopaedics Journal, 2011, Volume 5 365

Fig. (9). Physical Component Summary and Mental Component
Summary success rates through 12 months post-treatment.
DISCUSSION

novel, low profile device that results in excellent safety and
effectiveness based on the 12-month outcomes reported in
the current study including improvements of 64% in ODI,
53% for extremity pain, 49% for axial pain, 41% for PCS,
and 22% for MCS. This study represents the first clinical
account of patient outcomes with the Superion device.
The minimally invasive Superion Interspinous Spacer is a

device are comparable to those reported with laminectomy,
which is the standard of care for surgical LSS treatment.
Thomé and colleagues [28] treated 40 patients who presented
with symptomatic lumbar spinal stenosis with wide
laminectomy. Through 12 to 18 months following
laminectomy, pain decreased 45%, PCS improved 38% and
MCS improved 24%. However, perioperative complications
were reported in 23% of patients and 12% required fusion or
adjacent level decompression. These data were corroborated
by a meta-analysis that reported a 13% overall complication
rate for laminectomy including 0.3% perioperative mortality,
6% dural tear, 3% infection, and 3% deep vein thrombosis
[13]. Furthermore, overall success rates with laminectomy
are highly variable, ranging from 26% to 100% [3, 13, 29,
30]. Despite similar mid-term patient outcomes, the safety
profile of the Superion device suggests fewer potential risks
compared to laminectomy.
Patient outcomes following treatment with the Superion

better, outcomes as the X-STOP Interspinous Process
Decompression System, which is the only FDA-approved
interspinous spacer. We reported a 53% improvement in leg
pain and a 64% decrease in ODI. For comparison, a study of
175 patients treated with the X-STOP device reported a 36%
improvement in leg pain and a 55% ODI improvement
through 12 months [19]. Complication rates of 9-12% [31,
32] and a 58% secondary decompression surgery rate within
2 years of implant [33] have been reported with the X-STOP
device. The follow-up period in the current study extends
only through 12 months so no direct comparison of
complication and revision rates can be made with certainty.
However, the smaller profile of the Superion device in
addition to the less invasive percutaneous delivery of the
The Superion device also yields similar, if not slightly
implant versus the open procedure required for the X-STOP
device may yield patient safety advantages (Fig. 10a, b).

Fig. (10). A/P (a) and lateral (b) radiographs comparing the profile
of the X-STOP versus the Superion interspinous spacers.

treatment of lumbar spinal stenosis is likely because, unlike
laminectomy, implant of this interspinous spacer avoids
resection of the posterior spinal elements and thus does not
compromise spinal stability and affords a reversible
percutaneous device explant if required in the future. A finite
element model of a lumbar spine that underwent
laminectomy revealed that removal of the posterior elements
resulted in increased flexion-extension and axial rotation at
the surgical site and the authors concluded that minimization
of bone and ligament removal, such as with the Superion
procedure, results in greater lumbar stability [34] and
potentially lowers risk for fusion surgery. In fact, a cadaver
study demonstrated that implantation of the Superion device
The excellent safety profile of the Superion device for

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366 The Open Orthopaedics Journal, 2011, Volume 5 Bini et al.
prevents supraphysiological motion at the symptomatic level
and has no adverse impact on the local anatomy [35].

spacer implantation, the average hospital stay in the current
study was 3 days. However, this was mainly to support
adequate reimbursement under local regulations and did not
accurately reflect the convalescence required following the
procedure. In fact, an ongoing randomized clinical trial with
the Superion device clarifies that implantation should be on
an outpatient basis in most cases given the minimally
invasive nature of the procedure [36].
Despite the minimally invasive procedure of interspinous

concurrent control group. Thus, the degree of clinical
improvement realized by patients may be biased by non-
specific study effects, such as placebo. Regardless, the
magnitude of positive clinical outcomes implies a strong
beneficial treatment effect of the Superion device. Also,
variability in patient follow-up length precludes a definitive
assessment of 12-month clinical outcomes. Additional
studies of this device are warranted to determine long-term
safety and effectiveness outcomes.
The main limitation of this study was the lack of a
CONCLUSION

treatment option for carefully selected patients with
moderate LSS who are unresponsive to conservative care.
The Superion Interspinous Spacer is a safe and effective
CONFLICT OF INTEREST

financial support for development of this manuscript.
Vertiflex, Inc. (San Clemente, CA, USA) provided
ACKNOWLEDGEMENTS

illustrations.
We thank Mr. Randy Asher for assistance with graphical
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Received: May 27, 2011

Revised: September 3, 2011 Accepted: September 4, 2011
© Bini et al.; Licensee Bentham Open.

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