Journal of Spinal Disorders & Techniques
`Vol. 16, No. 5, pp. 455–460
`© 2003 Lippincott Williams & Wilkins, Inc., Philadelphia
`
`Posterior Lumbar Interbody Fusion for Degenerative Disc Disease
`Using a Minimally Invasive B-Twin Expandable Spinal Spacer
`
`A Multicenter Study
`
`Yoram Folman, †Sang-Ho Lee, ‡Jose Raul Silvera, and *Reuven Gepstein
`
`Department of Orthopaedic Surgery, Hillel-Yaffe Medical Center, Hadera, and *Spinal Care Unit, Meir Medical
`Center, Kefar-Sava, Israel; †Department of Neurosurgery, Wooridul Spine Hospital, Seoul, Korea; and ‡Department
`of Neurosurgery, Uyapar MC, Puerto Ordaz, Venezuela
`
`Summary: Acquired degenerative disc disease causes gradual disc space collapse, con-
`current discogenic or facet-induced pain, and possible compression radiculopathy. Sur-
`gical treatment aims to re-expand the intervertebral space and stabilize the involved
`segment in balanced alignment until fusion is complete. The prevailing methods make
`use of a twin cage device of predetermined size. Their implantation requires extensive
`exposure, entailing the sacrifice of posterior stabilizing structures. The procedure also
`results in significant traction on the dural sac and the cauda equina and is thereby a
`potential source of neurologic damage. The new expandable spinal spacer (ESS) was
`designed to mitigate all the shortcomings alluded to above. A prospective multicenter
`clinical study was conducted of 87 patients with chronic low back pain due to degen-
`erative disc disease, treated by posterior lumbar interbody fusion (PLIF) using a newly
`designed ESS. The study protocol was approved by the ethics committees of all the
`participating institutions. The objective was to test the safety and efficacy of the device.
`Each participant was followed periodically for >1 postoperative year. The ongoing
`record included intraoperative difficulties and complications, if any, radiologic evidence
`of fusion and clinical outcome as scored by pre- and postoperative questionnaires per-
`taining to pain intensity and degree of disability. No dural lacerations or neurologic
`deficit occurred. There were no mechanical failures of the spacer. Radiologic study
`demonstrated fusion in all but one patient. Disc space height that averaged 7.53 ± 2.42
`mm before surgery increased to 10.03 ± 2.00 mm at the time of surgery and stabilized
`at 9.47 ± 2.10 mm upon final follow-up. Visual Analog Scale and Oswestry Index
`decreased by 60% and 58%, respectively. PLIF using the ESS achieves the same ultimate
`outcome as do other methods currently in use but does not share the handicaps and
`hazards and is more user-friendly to the surgeon. Key Words: degenerative disc disease,
`posterior lumbar interbody fusion, spinal spacer
`
`INTRODUCTION
`
`Acquired degenerative disc disease is manifested by
`progressive collapse and consequent bulging of the redun-
`dant disc surface, the ligamenta flava, and the posterior
`longitudinal ligament. Narrowing of the intervertebral
`
`Received January 13, 2003; accepted May 22, 2003.
`Address correspondence and reprint requests to Dr. Yoram Folman,
`Department of Orthopaedics, Hillel-Yaffe Medical Center, Hadera
`38100, Israel. E-mail: folman@hillel-yaffe.health.gov.il
`
`space causes subluxation and eventual arthrosis of the
`facet joints. The involved unstable segment may also slip
`backward or forward. These mechanical aberrations tend
`to cause discogenic or facet-induced pain and may result
`in compressive radiculopathy.1 Structural solution of the
`problem requires reversal of the process, that is, re-
`expansion of the disc space and immediate stabilization of
`the segment in balanced alignment to ensure gradual in-
`tervertebral welding. Posterior lumbar interbody fusion
`(PLIF) is biomechanically sound as it ablates the degen-
`erated disc, restores the intervertebral height, relieves fo-
`GLOBUS MEDICAL, INC.
`EXHIBIT 1017
`IPR2015-to be assigned
`(Globus v. Flexuspine)
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`raminal stenosis, and positions the bone graft along the
`weight-bearing axis.2 Immediate initial stability is pro-
`vided by recoil of the stretched annulus fibrosus and the
`interspinal ligaments. Application of this promising con-
`cept was pioneered by Briggs et al3 in 1944 and popular-
`ized by Cloward4 shortly thereafter. However, clinical tri-
`als encountered a high rate of graft failure (resorption,
`migration, nonunion) and donor site morbidity.5 In 1988,
`Bagby6 introduced the concept of an implanted twin cage
`support designed to neutralize the compressive forces
`while providing the immediate three-dimensional stability
`that is essential for successful incorporation of the fragile,
`cancellous bone graft housed within. Yet this device has
`some major shortcomings: It has to be large enough to
`cause tension in the annulus, essential for immediate sta-
`bility6; and because of its obligatory size, its implantation
`requires excision of facets. This, paradoxically, subtracts
`from the stability (in extension and axial rotation) that the
`twin cage support is intended to confer.7 Supplementary
`pedicle screw fixation8,9 and restoration of posterior ele-
`
`ments10 have been advocated as compensatory measures.
`Because of its size, the device also puts traction on the
`dural sac and on nerve roots, risking dural laceration, neu-
`rologic damage,8,11–13 and delayed epidural fibrosis.14
`The purpose of the current study is to report our early
`experience with a newly designed B-twin expandable spi-
`nal spacer (B-twin ESS) that is free of all the drawbacks
`enumerated.
`
`PATIENTS AND METHODS
`
`Patient Selection
`
`Inclusion criteria were disabling low back pain for ⱖ6
`months, nonresponse or inadequate response to conserva-
`tive treatment, firm diagnosis of degenerative disc disease
`on the basis of typical symptoms, plus diagnostic findings
`on magnetic resonance imaging or discogram. Exclusion
`criteria included any disease that could adversely affect
`bone quality (eg, spine infection, tumor, metabolic bone
`
`FIGURE 1. A, The cage in its reduced configuration. The five fins are enclosed within a cylinder 5 mm in diameter. B, The single-use
`delivery system. C, The cage in its expanded configuration. D, The twin cages in their final expanded configuration 25 mm long and 13.5–15
`mm in diameter in situ.
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`disease), drug or alcohol abuse, and behavioral disorders
`that could impair patient cooperation.
`
`Device Description
`
`The device (Disc-O-Tech Medical Technologies Ltd.,
`Herzliya, Israel) is made of titanium. When collapsed, five
`fins are enclosed within a cylinder 5 mm in diameter (Fig.
`1A). Following placement within the disc space by a
`single-use delivery system (see Fig. 1B), the implant is
`expanded fin by fin until it is 25 mm long and up to 15 mm
`in diameter (see Figs. 1C and D). The final configuration
`is trapezoid. There are three available size options: 9.5/11,
`11.5/13, and 13.5/15. One of these is selected on the basis
`of preoperative x-rays and is adjusted intraoperatively as
`necessary. Upon completion of the process, the device
`self-locks.
`
`Operative Procedure
`
`Following a routine bilateral approach (limited to fla-
`vectomy), discectomy and endplate curettage are meticu-
`lously carried out. The intervertebral space is packed with
`cancellous iliac bone autograft delivered through a 5-mm-
`diameter funnel. The b-twin ESS is introduced into the
`intervertebral space bilaterally and is then expanded. Both
`stages are monitored by C-arm fluoroscopy. Since the first
`fin is opened perpendicularly to the endplates, adjustments
`can be made at this stage by turning the delivery system
`90° and repositioning. No drilling, tapping, or hammering
`is necessary. The spacer is installed “stand-alone” or
`supplemented by a posterolateral intertransverse graft.
`Pedicle screw fixation may be necessary in the presence of
`spondylolisthesis or following previous facetectomies
`(Fig. 2).
`
`Postoperative Radiologic Evaluation
`
`Radiologic proof of fusion required fulfillment of the
`following criteria: no radiolucent gap at the device-
`vertebral endplate interface, no evidence of mobility in
`flexion-extension roentgenogram, and presence of bridg-
`ing trabeculae across the area of arthrodesis. In equivocal
`cases, we added a computed tomography (CT) scan (2-
`mm slices) with sagittal reformation, as recommended.15
`
`FIGURE 2. Plain lateral radiograph showing the B-twin ESS
`supplemented with pedicular screw fixation in patient whose sur-
`gical history included destabilizing excision of the facet joints of the
`involved segment.
`
`each follow-up visit (1, 3, 6, 12, and 24 months after
`surgery) included neurologic examination, x-ray studies,
`and repeat VAS and Oswestry Index scores. Upon termi-
`nation of follow-up, the entire protocol on each patient
`was submitted to a clinical monitor for review.
`
`Statistical Methods
`
`Descriptive statistics were applied to determine means
`and standard deviations. The scoring binomial test was
`applied to changes in the VAS score and the Oswestry
`Index.
`
`RESULTS
`
`Data Acquisition
`
`Preoperative information included the patient’s medical
`history, socioeconomic status, physical examination, and
`results of imaging studies. Pain and disability were scored
`by a Visual Analog Scale (VAS) and the Oswestry In-
`dex,16 respectively. The operative notes covered all diffi-
`culties and complications encountered. Data elicited at
`
`Our study was based on 87 patients aged 17–77 years
`(mean 45.2 ± 13.7 years). There were 46 men and 41
`women. Duration of disability was from 5 to 180 months
`(mean 48.6 ± 39.8 months). In 54 cases, the B-twin ESS
`was implanted “stand-alone”; in 10 it was supplemented
`by floating intertransverse fusion and in 23 by pedicle
`screws and rod constructs. The procedure lasted on aver-
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`FIGURE 3. A, Sagittal T2-weighted magnetic resonance image of the lumbar spine, showing degenerated, collapsed, and herniated disc
`at L4–L5 of a 30-year-old woman with low back pain of 12 months’ duration without symptoms of nerve root compression. B, Follow-up
`radiograph 12 months postoperatively showing implanted B-twin ESS. Disc height is partially restored. C, CT scan with sagittal reformation
`showing well-incorporated implant.
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`age 148 ± 64 minutes (range 60–330 minutes), and mean
`blood loss was 410 ± 330 mL (range 300–1,500 mL). Disc
`space height averaged 7.53 ± 2.42 mm before surgery. It
`increased to 10.03 ± 2.00 mm at surgery and was 9.47 ±
`2.10 mm at final follow-up. Procedure-related complica-
`tions included two malpositioned implants, which neces-
`sitated intraoperative repositioning, and one postoperative
`migration of an implant that had to be removed. There
`were no dural lacerations, no deep wound infections, and
`no neurologic damage. The shortest follow-up period was
`12 months (average 15 months, range 12–26 months). To
`date, no participant has been lost to follow-up. Union of
`the bone graft has been established radiologically in all but
`one patient. The mean disability score decreased from 8.5
`to 3.3, a 60% improvement (P < 0.01). The disability score
`decreased from 31.0 to 12.7, a 58% improvement (P <
`0.01). At the last follow-up visit to date, 75 patients (86%)
`considered the operation to have been worthwhile.
`
`DISCUSSION
`
`PLIF is increasingly advocated as the treatment of
`choice for disabling low back pain due to degenerative
`disc disease. Fusion rates exceeding 90% have been re-
`ported. Seventy percent to 90% of the patients were sat-
`isfied with the results,8,11,17,18 and 75–95% returned to
`work.17,19 Similar results were achieved in the current
`series. They are comparable with those of 360° fusion,
`which entails a far larger operation.19 Interseries differ-
`ences in the correlation between fusion rates and clinical
`outcome may be attributable to the unreliability of plain
`x-ray evaluation of fusion15,20 and/or the influence of
`varying socioeconomic conditions11 and litigation is-
`sues8,11 on the way the patients describe their postopera-
`tive status. The biomechanical properties of the B-twin
`ESS were designed to provide immediate mechanical con-
`straint in all planes. Our clinical results were consistent
`with those of the pilot tests on artificial models and on
`cadaver spines. The constraint of flexion and lateral bend-
`ing is mediated by tension in the annulus. This is engen-
`dered by distraction of the disc space by the spacer. The
`latter is accomplished by a “jacking-up” mechanism rather
`than by techniques that involve drilling, tapering, or ham-
`mering. Stability in axial rotation is credited to the limited
`invasiveness of the surgical procedure, which makes it
`possible to preserve the main stabilizers in the axial plane,
`namely, the facets and the annulus fibrosus.7,21 At the
`outset, our main concerns were in regard to the possibility
`and extent of implant subsidence (penetration of the end-
`plates) and the possibility of implant migration. In prac-
`tice, subsidence averaged only 0.28 mm per fin (0.56 mm
`per implant). This did not jeopardize stability of the con-
`struct. Moreover, engagement of the fins in the endplates
`
`added an element of resistance to migration. It is logical to
`expect that this optimal situation is critically dependent
`upon the quality of vertebral bone. This consideration may
`be of crucial importance when selecting candidates for
`spacer-assisted PLIF. As indicated above, the current
`study excluded patients with bone disorders (eg, osteopo-
`rosis). In the final analysis, any stabilizing construct is
`bound to fail if fusion does not occur. In this study, x-rays
`established that fusion was accomplished in all but one
`patient. This favorable result may be ascribed to the rela-
`tively small implant-endplate contact area. This left a large
`area for the bone graft and enabled bone-to-bone contigu-
`ity, without having to rely on bone growth into and
`through the implant, as in the case of most of the other
`cage spacers that prevail. Moreover, meticulous curettage
`of the nucleus, rather than installation of the device within
`a reamed channel, was suggested to promote fusion.22 We
`could rule out radiographic signs of nonunion, that is,
`radiolucency at the implant–endplate interface and/or evi-
`dence of mobility on dynamic fluoroscopy. However, the
`length of the device and its double contour precluded an
`unequivocal display of bridging trabeculae.
`We would emphasize that the cardinal merit of the B-
`twin ESS is the relative freedom from complications as
`recounted above. Although PLIF per se has established
`itself as the surgical approach of choice, its record of
`complications has been puzzling. A recent review reported
`major complications in 45% of the cases and repeated
`operations in 25–40%.8,22 PLIF using the B-twin ESS has
`thus far achieved as good a clinical outcome as the pre-
`ceding variants of the method; and, in sharp contrast to the
`latter, virtually no complications have occurred.
`
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