The Scientific World Journal
`Volume 2012, Article ID 246989, 7 pages
`doi:10.1100/2012/246989
`
`The cientificWorldJOURNAL
`
`Clinical Study
`Clinical Outcome and Fusion Rates after the First 30 Extreme
`Lateral Interbody Fusions
`
`Gregory M. Malham,1 Ngaire J. Ellis,2 Rhiannon M. Parker,2 and Kevin A. Seex3
`
`1 Neuroscience Institute, Epworth Hospital, Bridge Road, Melbourne, VIC 3121, Australia
`2 Greg Malham Neurosurgeon, Suite 2, Level 1, 517 St. Kilda Road, Melbourne, VIC 3004, Australia
`3 Department of Neurosurgery, Macquarie University, Sydney, NSW 2109, Australia
`
`Correspondence should be addressed to Gregory M. Malham, gmalham@bigpond.net.au
`
`Received 2 August 2012; Accepted 23 September 2012
`
`Academic Editors: L. Pimenta, W. D. Smith, and W. Taylor
`
`Copyright © 2012 Gregory M. Malham et al. This is an open access article distributed under the Creative Commons Attribution
`License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly
`cited.
`
`Introduction. The lateral transpsoas approach for lumbar interbody fusion (XLIF) is gaining popularity. Studies examining a
`surgeon’s early experience are rare. We aim to report treatment, complication, clinical, and radiographic outcomes in an early
`series of patients. Methods. Prospective data from the first thirty patients treated with XLIF by a single surgeon was reviewed.
`Outcome measures included pain, disability, and quality of life assessment. Radiographic assessment of fusion was performed by
`computed tomography. Results. Average follow-up was 11.5 months, operative time was 60 minutes per level and blood loss was
`50 mL. Complications were observed: clinical subsidence, cage breakage upon insertion, new postoperative motor deficit and bowel
`injury. Approach side-effects were radiographic subsidence and anterior thigh sensory changes. Two patients required reoperation;
`microforaminotomy and pedicle screw fixation respectively. VAS back and leg pain decreased 63% and 56%, respectively. ODI
`improved 41.2% with 51.3% and 8.1% improvements in PCS and MCS. Complete fusion (last follow-up) was observed in 85%.
`Conclusion. The XLIF approach provides superior treatment, clinical outcomes and fusion rates compared to conventional surgical
`approaches with lowered complication rates. Mentor supervision for early cases and strict adherence to the surgical technique
`including neuromonitoring is essential.
`
`1. Introduction
`
`The lateral transpsoas approach for anterior lumbar inter-
`body fusion (extreme lateral interbody fusion (XLIF)) was
`developed as a less-invasive alternative to conventional
`anterior and posterior approaches for interbody fusion [1].
`Similar to anterior exposures for lumbar interbody fusion,
`the lateral approach allows for placement of a wide footprint
`intervertebral cage with wide apertures to provide superior
`anterior column realignment [2, 3] as well as a healthy
`fusion environment [4], without anterior and posterior
`longitudinal ligament (ALL and PLL) resection. In addition,
`the lateral approach mitigates many of the risks more
`common to traditional approaches, namely, vascular and
`visceral risks associated with anterior approaches [5–8] and
`the neural complications and bony resection common to
`posterior approaches [9, 10]. However, safe passage through
`the psoas muscle requires neuromonitoring to identify the
`
`nerves of the lumbar plexus, the injury of which represents a
`significant risk of the approach.
`Since the introduction of the approach in the literature
`in 2006 [1], the procedure has increased in popularity, and
`reports of safety and outcome continue to be needed to fully
`validate the approach, especially during early cases of a new
`approach where a learning curve may be present [11, 12].
`The purpose of this study was to examine clinical and
`radiographic outcomes in the first thirty patients treated with
`the XLIF approach by one surgeon in Melbourne, Australia.
`
`2. Materials and Methods
`
`Data were collected through a prospective registry, with
`retrospective analysis performed of the first 30 (consecu-
`tive) patients treated with extreme lateral interbody fusion
`(XLIF, NuVasive Inc., San Diego, CA, USA) by a single
`
`
`
` 1
`
`NUVASIVE 1049
`NuVasive, Inc. v. Warsaw Orthopedic, Inc.
`IPR2013-00206
`IPR2013-00208
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`surgeon (GM) in Melbourne, Australia from February 2011
`to October 2011. Patients were treated only after failure
`of extended conservative therapy and imaging studies,
`including dynamic (flexion, extension, and lateral bending)
`radiography, computed tomography (CT) coregistered with
`bone scans, magnetic resonance imaging (MRI), and bone
`mineral density (DEXA) scans, as appropriate. Data were
`collected preoperatively and then postoperatively at standard
`follow-up intervals for one year postoperatively.
`Baseline patient
`information included basic demo-
`graphic information as well as the primary indication for
`surgery and baseline medical comorbidities. Treatment
`information included levels treated, biologics and fixation
`used, and the presence of any procedural side effects, compli-
`cations, or reoperations. Patient-reported outcomes included
`minimum, maximum, and average back and leg pain (LBP
`and LP) (visual analogue scale (VAS)), disability (Oswestry
`Disability Index (ODI)) and quality of life (SF-36 physical
`and mental component scores (PCS and MCS)). Fusion
`was assessed using high definition (HD) CT (Somatom
`scanner) taken one to two days postoperatively to assess
`instrumentation placement and then between six and twelve
`months postoperatively to assess fusion status. Fusion was
`defined as the presence of bridging interbody trabecular bone
`[13] and was determined by a third-party radiologist from
`within the treating institution.
`The surgical procedure has previously been described
`◦
`off-midline retroperitoneal approach
`[1] but involves a 90
`to the anterior lumbar spine with blunt dissection through
`the fibres of the psoas muscle to the lateral border of the
`disc space. Passage through the psoas muscle, avoiding the
`nerves of the lumbar plexus, is accomplished using a neu-
`romonitoring system (NV JJB/M5, NuVasive, Inc.) integrated
`into approach and procedural instrumentation. Neuromon-
`itoring with this system provides real-time and surgeon-
`directed discrete-threshold electromyographic responses to
`provide geographic information about the presence of motor
`nerves relative to procedural instrumentation [14, 15]. One
`thoracic level was treated (T6-7), and a similar procedure
`to the lumbar XLIF procedure was followed, though using
`a transpleural lateral approach, as has also been previously
`described [16, 17]. Direct decompressions were performed
`when required.
`All patients were fitted with intervertebral poly-
`etheretherketone (PEEK) cage(s) (CoRoent, NuVasive, Inc.)
`filled with a combination of bone morphogenetic protein
`(rhBMP-2 (BMP), Infuse, Medtronic, Inc., Memphis, TN,
`USA) and Mastergraft β-TCP granules (Medtronic, Inc.).
`BMP has a fixed concentration of 1.5 mg/cc, and the dose
`used per level was volume dependent (i.e., the internal
`volume of cage equalled BMP volume in cc), using (a
`small kit of BMP (2.8 cc providing a 4.2 mg dose), per
`the manufacturers recommendation, following a one-hour
`absorption into the carrier period. No BMP was placed
`outside the cage. Supplemental internal fixation was applied
`as needed.
`Statistical analyses included frequency testing for demo-
`graphic and treatment variables, paired t-tests comparing
`clinical outcomes from preoperative levels, and fisher exact
`
`tests for comparisons of the frequency of events between
`groups. Statistical analysis was carried out using SPSS v. 19.0
`(SPSS IBM, Chicago, IL, USA) with statistical significance
`measured at P < 0.05.
`
`3. Results
`
`The first thirty (30) patients treated with XLIF were included
`in the analysis and had a mean age of 63 years with a mean
`body mass index (BMI) of 26.7, and 20 (67%) were female.
`Baseline comorbidities included tobacco use (20%), diabetes
`mellitus (13%), and prior lumbar spine surgery (20%). The
`most common primary diagnoses included degenerative disc
`disease (41%), spondylolisthesis (31%), and degenerative
`scoliosis (24%). In 30 patients, 43 levels (1.4 per patient,
`range 1–3) were treated with the most common levels being
`L3-4 and L4-5 (in 57% of patients, each). Supplemental
`internal fixation was used in 15 (50%) patients and included
`pedicle screw fixation in 13 and interspinous plating in two
`patients. Staging of secondary procedures (decompressions
`and/or fixation) occurred in 47% of cases. A summary
`of baseline and treatment
`information is included in
`Table 1.
`Average operating time per level was 60 minutes with a
`mean blood loss of 50 mL per level (range 10–150 mL).
`Four (13%) complications were observed. One large
`bowel injury occurred in a thin 53-year-old female patient
`who underwent a left-sided approach for a L3-5 XLIF
`with posterior instrumentation for disabling low back pain
`above a previous L5-S1 fusion. The patient had a past
`history of midline laparotomy for bowel obstruction per-
`formed 20 years previously. On day three postoperatively
`the patient developed left lower quadrant abdominal pain
`with tenderness and tachypnoea. Chest and abdominal plain
`radiographs were indeterminate for free air, but abdominal
`CT demonstrated intraperitoneal air (Figure 1). Urgent
`laparotomy found that the descending colon had been
`perforated adjacent to the L4-5 level on the side ipsilateral
`to the approach. One patient developed a new motor
`deficit immediately evident postoperatively with 4/5 power
`quadriceps due to a posteriorly placed cage which resulted
`in a L2 radiculopathy that partially resolved with persistent
`4+/5 weakness at 12 months. One instance of symptomatic
`subsidence was observed in the form of unilateral disc space
`collapse with a 22 mm-wide cage inferior to a prior fusion,
`and while a reoperation was not required, fusion was not
`evident at 12 months. Finally, there was one instance of cage
`breakage following an attempted forceful impaction of an
`8 mm cage into a collapsed L3-4 disc space. In addition, three
`cases of asymptomatic (radiographic) subsidence (<25%
`height loss) were observed without sequelae. Of the four
`instances of cage subsidence, three included 18 mm cages
`(two standalone, one bilateral pedicle fixation) and one with
`22 mm (standalone).
`Side effects of the approach were observed, with five
`cases of anterior thigh sensory changes (dysesthesias), four
`of which had resolved by six weeks postoperative and one of
`which was persistent at last followup (12 months). Of these,
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`Table 1: Listing of patient demographic and treatment informa-
`tion.
`
`Statistic n = 30
`62.7 (10.5) (30–81)
`20 (66.7)
`
`26.7 (5.4) (17.6–37.9)
`
`Figure 1: Abdominal axial computed tomography (CT) showing
`intraperitoneal free air following unrecognized bowel perforation.
`
`second underwent bilateral pedicle fixation for symptomatic
`facet arthropathy.
`Four patients were lost to followup. All patients or their
`representatives were contacted by phone for followup, and
`reasons for noncompliance included one who is a workers
`compensation case and refused followup, another is an
`elderly women who was satisfied with her outcome but was
`unable to travel to the office, and another whose son reported
`that the patient had become morbidly obese (130 kg) and was
`now agoraphobic and unable to leave the house. One patient
`was unable to be contacted.
`Of those able to be followed (26), average followup
`was 11.5 months (range 9–12). Average back and leg pain
`(in those with leg pain) improved 6.9 and 6.6 to 2.9 and
`2.9, representing a 63% and 56% improvement, respectively
`(Figures 2 and 3). Disability (ODI) improved from 56.9
`preoperatively to 33.5 at last followup (41.2%) with PCS
`and MCS improving 51.3% (27.0 to 40.8) and 8.1% (46.9
`to 50.7), respectively (Figure 4). All clinical results were
`statistically significantly improved from baseline (P < 0.001)
`except for MCS (P = 0.200). Fusion rate confirmed on HD
`CT coronal views (Figure 5) progressed from 46% (12/26)
`at 6 months to 58% (15/26) at 9 months and 85% (22/26)
`at 12 months postoperatively (Table 2). In patients with
`supplemental internal fixation, a 92% (12/13) fusion rate
`was observed, while without fixation only 77% (10/13) of
`patients exhibited complete fusion at 12 months, a difference
`which was not statistically significant (P = 0.593).
`
`4. Discussion
`
`The primary indications for the XLIF procedure are tho-
`racolumbar pathology from approximately T4 through L5
`(limited superiorly by the axilla and interiorly by the iliac
`crest) and include symptomatic disc degeneration [18],
`degenerative scoliosis [19, 20], spondylolisthesis, adjacent
`segment disease [21], as well as traumatic, tumor, and infec-
`tion pathologies [22–24]. Relative contraindications for XLIF
`included L5-S1 pathology, retroperitoneal adhesions, and
`early bifurcation of the iliac vessels. Preoperative assessment
`
`Characteristic
`Mean age in years (stdev) (range)
`Female (%)
`Mean body mass index (BMI), (stdev)
`(range)
`Comorbidities
`Comorbidity type
`Tobacco use (%)
`Diabetes (%)
`Any prior lumbar spine surgery (%)
`Lami/MLD (%)
`Fusion (%)
`Primary diagnosis
`Degenerative disc disease (%)
`Herniated nucleus pulposus (%)
`Spondylolisthesis (%)
`Scoliosis (%)
`Levels treated (mean per patient) (range)
`T6-7 (% of levels) (% of patients)
`L1-L2 (% of levels) (% of patients)
`L2-L3 (% of levels) (% of patients)
`L3-L4 (% of levels) (% of patients)
`L4-L5 (% of levels) (% of patients)
`Biologics used
`rhBMP-2 (%)
`Fixation type (%)
`Interspinous plating (%)
`Transpedicular fixation (%)
`Unilateral (%)
`Bilateral (%)
`Standalone (%)
`Staged fixation?
`14 (47)
`Yes (%)
`16 (53)
`No (%)
`n: number of patients; stdev: standard deviation; Lami: laminectomy; MLD:
`microlumbar discectomy.
`
`6 (20)
`4 (13)
`6 (20)
`4 (67)
`2 (33)
`n = 29 (1 missing)
`12 (41)
`1 (3)
`9 (31)
`7 (24)
`43 (1.4) (1–3)
`1 (2) (3)
`1 (2) (3)
`6 (14) (20)
`17 (40) (57)
`17 (40) (57)
`
`30 (100)
`
`2 (7)
`13 (40)
`2 (15)
`11 (85)
`15 (50)
`
`Table 2: XLIF fusion rates.
`
`Time postoperatively
`6 months
`9 months
`12 months
`
`Fusion rate
`46% (12/26)
`58% (15/26)
`85% (22/26)
`
`three occurred within the first 10, and none occurred in the
`last 10, patients of the series. Complications and side effects
`are included in Table 3.
`Two patients required reoperation: one underwent a
`microforaminotomy for a posteriorly placed cage and a
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`ODI and SF-36 outcomes
`
`Preoperative
`
`Last followup
`
`ODI
`PCS
`MCS
`
`70
`
`60
`
`50
`
`40
`
`30
`
`20
`
`Low back pain (VAS) outcomes
`
`Preoperative
`
`Last followup
`
`LBP min.
`LBP max.
`LBP ave.
`
`10
`
`0123456789
`
`4
`
`Figure 2: Change in minimum, maximum, and average low back
`pain (LBP) from preoperative to last followup (mean 11.5 months).
`
`Figure 4: Change in average disability (ODI), and physical and
`mental quality of life (PCS and MCS) from preoperative to last
`followup (mean 11.5 months).
`
`Figure 5: Coronal computed tomography (CT) showing solid
`arthrodesis at 12 months postoperative following L4-5 XLIF.
`
`Leg pain (VAS) outcomes
`
`10
`
`0123456789
`
`Preoperative
`
`Last followup
`
`LP min.
`LP max.
`LP ave.
`
`Figure 3: Change in minimum, maximum, and average leg pain
`(LP) from preoperative to last followup (mean 11.5 months).
`
`of the neurovascular complex at each level to be treated on
`axial MRI is essential to have a preoperative understanding
`of regional anatomy as it relates to the lateral approach [25].
`In the first 30 cases of XLIF at one institution, the authors
`observed a 13% complication rate in 30 patients with two
`reoperations occurring. Mean followup was 11.5 months
`and low back and leg pain decreased by 63% and 56%,
`respectively, with similar improvements in disability (41.2%)
`and physical and mental quality of life (51.3% & 8.1%, resp.).
`In comparison with alternative approaches for lumbar
`interbody fusion, complications rates with transforaminal
`and posterior lumbar interbody fusion (T/PLIF) have gener-
`ally been reported in elevated ranges compared to the current
`series. In 2009, Rihn et al. [9] reported on a series of 119 TLIF
`cases performed at Thomas Jefferson University Hospital.
`An overall complication rate of 46% (55) was observed in
`
`35% (40) of patients. While 10 complications were attributed
`to iliac crest bone graft harvesting, there was a 10.9% rate
`of new postoperative radiculitis, a 5% infection rate, and a
`10.1% reoperation rate. Similarly, Okuda et al. [26] in 2006
`reported the surgical complications of 251 PLIF patients
`treated at a single institution. In this series, the authors found
`an intraoperative complication rate of 10.3% with a new
`postoperative neurologic deficit rate of 8.3% (21; 19 motor,
`2 sensory), with 32% of those classified as slight, 47% severe,
`and 21% permanent. Results in the current series, having
`observed a 13% complication rate, is favorable to these
`similar study-design historical results, even when factoring
`in that cases in the current series represented the adoption of
`a new procedure [11, 12]. In total, six (20%) neural adverse
`events occurred, one motor complication and 5 sensory
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`5
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`Table 3: Complications and side effects.
`
`Patient number
`1–10
`11–20
`21–30
`Totals
`
`Levels (mean)
`1.1
`1.3
`1.5
`42
`
`Dysaesthesia
`3
`2
`0
`5
`
`Motor deficit
`1
`0
`0
`1
`
`Reoperation
`1
`0
`1
`2
`
`Subsidence
`0
`2
`2
`4
`
`Cage breakage
`0
`0
`1
`1
`
`Bowel injury
`0
`0
`1
`1
`
`side-effects, rates which are consistent with high-quality
`prospective multicenter studies of XLIF performed using
`surgeons already familiar with the procedure [14]. Tohmeh
`et al. [14] observed a 17.5% rate of transient anterior thigh
`sensory changes postoperatively with a 2.9% new motor
`deficit rate in 102 XLIF patients treated at L3-4 and/or L4-5.
`In addition, the single incidence of motor injury occurred as
`a result of a misplaced cage (case 6) rather than during direct
`injury by procedural instrumentation during the approach
`for procedure. When considering the generally transient
`nature of the expected sensory nerve irritation, the inci-
`dence of neural events (the most apparent anatomical risk
`during the procedure) also compares favorably to posterior
`approaches.
`Anatomically, the sensory nerves at risk with this oper-
`ation are the ilioinguinal, iliohypogastric, lateral femoral
`cutaneous, and genitofemoral nerve [27]. The first three
`nerves are at risk of injury in the approach to the psoas. The
`genitofemoral nerve arises from the L1 and L2 nerve roots,
`traverses the psoas, and descends along the anteromedial
`border of the psoas deep to its fascia [28]. The nerve crosses
`the L2-3 disc space and may be injured anywhere along its
`course [28, 29] though the risk is somewhat mitigated by
`more posterior docking on the lateral aspect of the disc space,
`enabled by neuromonitoring of the more-posterior motor
`nerves of the lumbar plexus [15]. The patients in this series
`that experienced the side effect of genitofemoral irritation,
`which are relatively common with this procedure, usually
`resolve within 6 weeks, but persistence has been reported
`[14, 30] as in one of the five cases in this series. In the
`current series, we observed a reduction in the incidence of
`sensory side effects from early cases (20% rate in the first
`20 cases) compared to later (0% in last 10 cases) though
`the difference in rate was not statistically significant (P =
`0.140). Potential reasons for the decrease in these events may
`include decreased duration of time and the psoas muscle
`was under retraction (procedural efficiency) and increased
`comfort with more posterior docking (avoiding the more
`anterior genitofemoral nerve) with incremental adherence to
`neuromonitoring.
`Radiographic subsidence was observed in three cases,
`with one instance of both radiographic and clinical subsi-
`dence. Factors thought to contribute to cage subsidence are
`the narrower 18 mm cages, osteoporosis, the use of BMP-2,
`the use of standalone cages, and iatrogenic endplate violation
`[31, 32]. Three of the four cage subsidence in this series
`occurred with 18 mm standalone cages. The symptomatic
`subsidence occurred six weeks postoperatively after the inser-
`tion of a 22 mm standalone cage packed with BMP-2 inferior
`
`to a previous fusion in a patient with normal bone density.
`This may reflect increased biomechanical stress at the L4-5
`level as well as the osteolytic, inflammatory phase of BMP-2
`[32].
`In the patient who experienced the unrecognized bowel
`injury, the injury likely occurred during placement of the
`initial dilator, which was delivered at an angle from the
`plane perpendicular to the floor,
`in a deviation from
`the prescribed surgical technique. The patient required
`a Hartmann’s colostomy that was reversed two months
`later. She recovered without infection and reported signif-
`icant improvement in low back pain and mobility. Bowel
`injury following XLIF has previously been reported as
`a complication of the approach, both acute and delayed
`[33].
`Clinical and radiographic outcomes were consistent
`with previously-reported results which showed fusion rate
`ranges between 91% and 100% (though generally with more
`extended followup), 37% to 80% reduction in low back pain,
`and a 39% to 82.1% reduction in disability (ODI) [34].
`These results are similar or superior to conventional surgical
`approaches. Blumenthal et al. [35], as a part of the Charit´e
`artificial lumbar disc Food and Drug Administration (FDA)
`investigation, reported a 47.6% improvement in low back
`pain at 24 months postoperative in the ALIF fusion control
`group with a 41.5% improvement in ODI. Similar results
`were seen in ALIF by Kuslich et al. [36] in 1998, showing an
`improvement of 42% in pain and 31.5% in disability at 24
`months postoperatively.
`In the current series, the relatively lower early fusion
`rate seen in standalone cases may suggest an extended
`healing period due to the less-rigid segmental environment
`to promote fusion [37]. While this has yet to be formally
`studied, several studies of standalone XLIF show that some
`consistency with this notion though, also of note, is that
`progression to complete fusion does generally occur [38–41].
`
`5. Conclusion
`
`In summary, these data represent generally superior treat-
`ment (blood loss and operative time), clinical (pain, dis-
`ability, and quality of life), and fusion rates using the XLIF
`approach compared to conventional surgical approaches
`with substantially lowered complication rates. With specific
`training, mentor supervision for early cases, and strict
`adherence to surgical technique including neuromonitoring,
`surgeons can anticipate low perioperative morbidity even in
`the early period following the adoption of the approach.
`
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`Acknowledgments
`
`The authors would like to acknowledge Kyle Malone, MS for
`his editorial and statistical assistance in the preparation of
`this manuscript. No funds were received in support of this
`work, and no conflict of interests with any commercial party
`related to this manuscript exist with any of the authors.
`
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