SPINE Volume 39, Number 5, pp E326-E331 ©2014, Lippincott Williams & Wilkins
CLINICAL CASE SERIES
Rate of Revision Surgery After Stand-alone Lateral Lumbar Interbody Fusion for Lumbar Spinal Stenosis Venu M. Nemani, MD, PhD,* Alexander Aichmair, MD,* Fadi Taher, MD,† Darren R. Lebl, MD,* Alexander P. Hughes, MD,* Andrew A. Sama, MD,* Frank P. Cammisa, MD,* and Federico P. Girardi, MD*
Study Design. Retrospective case series. Objective. To examine the reoperation rate, specifically the need for posterior decompression and/or fusion, in a cohort of patients who underwent stand-alone lateral lumbar interbody fusion for symptomatic spinal stenosis with instability or deformity. Summary of Background Data. Lateral lumbar interbody fusion provides a minimally invasive means of achieving interbody arthrodesis and indirect foraminal decompression while avoiding the potential morbidity of traditional anterior or posterior approaches. The revision rate for formal posterior decompression after isolated lateral lumbar interbody fusion for spinal stenosis is unknown. Methods. One hundred seventeen patients who underwent stand-alone lateral lumbar interbody fusion for symptomatic spinal stenosis with an indication for fusion were included in the analysis. Detailed demographic and intraoperative data were collected. Clinical evaluation was done both preoperatively and at the final follow-up, and radiographical evaluation was done preoperatively and with the first postoperative standing radiographs. Results. A total of 10.3% of patients who underwent stand-alone lateral lumbar interbody fusion ultimately required revision surgery, most commonly for persistent radiculopathy and symptomatic implant subsidence. Average time to revision was 10.8 months. There was no difference in radiographical correction between patients who did and did not require revision surgery. From the *Hospital for Special Surgery, Weill Cornell Medical College, New York, NY; and †Department for Vascular and Endovascular Surgery, Wilhelminenspital Vienna, Vienna, Austria. Acknowledgment date: July 19, 2013. First revision date: November 1, 2013. Acceptance date: November 20, 2013. The device(s)/drug(s) is/are FDA-approved or approved by corresponding national agency for this indication. The manuscript includes unlabeled/investigational uses of the products/ devices listed below and the status of these is disclosed in the manuscript: bone morphogenetic protein-2 in lateral lumbar interbody fusion (LLIF); LLIF at more than 2 levels. No funds were received in support of this work. Relevant financial activities outside the submitted work: consultancy, royalties, stock/stock options and payment for development of educational presentations. Address correspondence and reprint requests to Venu M. Nemani, MD, PhD, Hospital for Special Surgery, 535 E 70th St., New York, NY 10021; E-mail: [email protected] DOI: 10.1097/BRS.0000000000000141
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Conclusion. Lateral lumbar interbody fusion provides a minimally invasive means to treat lumbar spinal stenosis with an acceptable revision rate for formal posterior decompression at early follow-up. Key words: transpsoas, XLIF, LLIF, minimally invasive, spinal stenosis, interbody fusion, revision. Level of Evidence: 4 Spine 2014;39:E326–E331
D
egenerative disease of the lumbar spine can cause pain and disability from compression of the underlying neural elements. Stenosis can occur in the central canal, lateral recess, or in the neuroforamina and has multiple etiologies, including intervertebral disc degeneration, facet hypertrophy, spondylolisthesis, or usually a combination of these factors.1 Traditional surgical approaches to spinal decompression have involved either a posterior approach to the spine followed by laminectomy/laminotomy, foraminotomy, and/or facetectomy, or an anterior approach with interbody distraction and arthrodesis.2 These approaches can be associated with significant morbidity to the patient, which have spurred the development of minimally invasive solutions to degenerative spinal disease. Lateral lumbar interbody fusion (LLIF) is an alternative, minimally invasive approach to the lumbar spine for degenerative conditions. It involves approaching the lumbar spine through a psoas-splitting retroperitoneal approach, while taking care to preserve and protect the lumbar plexus with minimal risk to these structures.3 LLIF offers several advantages compared with anterior approaches to interbody fusion including preservation of the anterior longitudinal ligament, the ability to seat the implant on dense apophyseal bone rather than on cancellous bone, and decreased risk of injury to the great vessels. A lateral annulotomy allows preservation of both the anterior longitudinal ligament and the posterior longitudinal ligament, allowing for correction of both sagittal and coronal plane deformities with an interbody device using ligamentotaxis.4 It has been shown recently that LLIF results in an increase in foraminal area via indirect compression.5 In many circumstances, LLIF is combined with formal posterior decompression and/or posterolateral fusion for a circumferential arthrodesis in patients at risk for pseudarthrosis; it March 2014
Copyright © 2014 Lippincott Williams & Wilkins. Unauthorized reproduction of this article is prohibited. SPINE130873.indd E326
01/02/14 11:12 AM
CLINICAL CASE SERIES is not known, however, the efficacy of stand-alone LLIF to treat symptomatic lumbar spinal stenosis in carefully selected patients with degenerative scoliosis or instability who may not be able to tolerate, or may not need, both anterior and posterior procedures. The goal of this study is to determine the rate of revision surgery for formal posterior decompression in patients who underwent stand-alone LLIF for symptomatic lumbar spinal stenosis.
MATERIALS AND METHODS Patients Institutional review board approval was obtained for this study; a waiver of the need to obtain informed consent for this retrospective analysis was granted by the board. Patients were eligible for inclusion if they had undergone stand-alone LLIF for a preoperative diagnosis that included lumbar spinal stenosis with an indication for interbody fusion such as instability alone or degenerative scoliosis with resultant instability. Stenosis was diagnosed in patients with clinical symptoms of radiculopathy or neurogenic claudication that had evidence on CT myelogram or MRI of either foraminal or lateral recess stenosis that correlated with the clinical findings. Patients were considered to have instability if they had a degenerative spondylolisthesis with evidence of motion on flexion/ extension views or a significant component of mechanical back pain. Scoliosis was defined as a coronal plane deformity measuring more than 10°. Both preoperative and postoperative radiographs had to be available for analysis in the Hospital for Special Surgery picture archiving and communication system. Patients were excluded if they had had any previous anterior or posterior surgery at the affected level, including laminotomy, laminectomy, and/or posterolateral, or interbody fusion. All operations were performed by the 4 senior authors (A.P.H., A.A.S., F.P.C., and F.P.G.), all fellowshiptrained spine surgeons, at a single institution.
Surgical Technique Details of the surgical technique have been described previously.6 In cases of degenerative scoliosis, the operated levels were approached through the side of the concavity to reach multiple levels through a single incision; otherwise, the laterality of the approach was based on the accessibility of the L4–L5 disc space in relation to the iliac crest. The psoas muscle was split under direct visualization carefully3 avoiding the traversing nerves with electromyography probes also used to avoid neural injury. A self-retaining retractor with illumination was placed after fluoroscopic confirmation of the correct disc space. After thorough discectomy, the disc spaces were sized with trial components using preoperative templating and intraoperative fluoroscopy for additional confirmation. Cages were packed with bone graft materials according to surgeon preference. Postoperatively, patients were allowed to ambulate as tolerated under the careful supervision of a physical therapist. All patients had standing radiographs of the lumbar spine performed prior to discharge. Spine
Stand-Alone LLIF for Stenosis • Nemani et al
Evaluation Demographic data were collected, as well as operating time, estimated blood loss, and operation-related complications. Clinical evaluation was done both preoperatively and at the final follow-up, and radiographical evaluation was done preoperatively and with the first postoperative standing radiographs. Radiographical evaluation included measurements of anterior disc height, posterior disc height, interpedicular height, foraminal area, and endplate angle. Office charts were reviewed to record preoperative and postoperative back and leg pain scores as well as neurological symptoms.
Statistical Analysis Analyses were first performed to determine the effects of stand-alone LLIF on visual analogue scale (VAS) pain scores, weakness, paresthesia, and radiographical parameters. Pre- to postoperative changes in leg and back VAS pain scores were assessed with paired t tests. Differences between pre- and postoperative leg weakness and paresthesia were assessed with McNemar tests. Pre- to postoperative changes in radiographical parameters (anterior height, posterior height, foraminal area, interpedicular height, and endplate angle) were assessed independently at each level with paired t tests, or Wilcoxon signed-rank tests if the data were non-normally distributed. Statistical assessment of radiographical parameters at L1–L2 was not possible because the revision group contained only 1 patient with a procedure at this level. Subsequently, differences in these patient parameters were assessed between patients who did and did not ultimately require revision surgery. Age at surgery, body mass index, operating room time, estimated blood loss, and leg and back VAS pain scores (preoperative, postoperative, and pre- to postoperative change) were assessed with independent t tests or with Mann-Whitney U tests. Associations between revision status and weakness, paresthesia, lumbar level, and the number of levels were assessed with the Fisher exact tests. Differences in radiographical parameters between nonrevision and revision groups were assessed independently at each level with independent t tests or with Mann-Whitney U tests. The level of significance for all tests was α = 0.05, and results presented are significant unless stated otherwise.
RESULTS Between March 2006 and April 2012, 451 patients underwent LLIF at Hospital for Special Surgery by the senior authors. Of these, 117 patients underwent stand-alone LLIF and met the inclusion and exclusion criteria to be included in the analysis. There were 83 females and 34 males, and average age was 63.6 years (range, 30–87). Average body mass index was 27.4. The average number of levels operated on was 2.0 (range, 1–4): 37 underwent a single-level procedure, 42 underwent a 2-level procedure, 34 underwent a 3-level procedure, and 4 underwent a 4-level procedure. Operating time averaged 146 minutes and estimated blood loss averaged 144 mL. Average follow-up was 15.6 months (range, 1.3–52.9 mo). After LLIF, patients had less leg pain (P < 0.001), back pain (P < 0.001), www.spinejournal.com
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CLINICAL CASE SERIES
Stand-Alone LLIF for Stenosis • Nemani et al
and leg weakness (P = 0.006), whereas leg paresthesia were unchanged (P = 0.20). All radiographical parameters were significantly improved at every lumbar spinal level after LLIF. There were 12 patients (10.3%) who ultimately required revision surgery for persistent symptoms during the followup period. There was no difference in demographic data or perioperative variables of patients who did and did not require revision surgery (Table 1). The average time to revision was 10.8 months (range, 2.6 – 39.6 mo) with 6 revisions being performed within 6 months, and 8 of 12 performed within 1 year. The most common reasons for revision surgery were persistent stenosis and symptomatic implant subsidence (Table 2). All patients except 2 who required revision ultimately had posterior decompression with instrumented fusion using pedicle screw fixation. One patient had laminotomies alone and 1 patient had a laminectomy with noninstrumented in situ fusion. Figure 1 shows images representative of a patient who underwent revision surgery for persistent symptoms of stenosis. Across all levels, LLIF resulted in a 53% increase in foraminal area (P < 0.001). The increase in foraminal area was similar but less at more caudal levels (L1–L2 = 61%, L2–L3 = 61%, L3–L4 = 53%, L4–L5 = 45%), and significant at every level (P < 0.001). Comparison of radiographical parameters when comparing pre- and postoperative radiographs showed essentially no difference between patients who ultimately did or did not require revision surgery, except for a greater increase in posterior disc height in patients ultimately requiring revision surgery (Table 3). Most importantly, there was no difference in the increase in overall foraminal area in patients who did and did not require revision surgery (53% increase in cases not requiring revision, 62% in cases requiring revision, P = 0.46). There was also no difference when this was analyzed at each individual spinal level. Overall lumbar lordosis measured across all patients increased from 43° to 47° after stand-alone LLIF (P = 0.01). There was no significant difference between the change in lumbar lordosis after surgery in patients who did and did not ultimately require revision surgery. Patients who ultimately did not require revision surgery showed significant improvement in their leg pain, back pain,
TABLE 1. Demographics and Perioperative
Variables
Revision
P
30:75
4:12
0.73
Age
64.0 ± 12.0
60.2 ± 14.0
0.31
BMI
27.3 ± 5.4
28.7 ± 4.0
0.42
2.1
1.8
0.59
OR time
148 ± 47 min
134 ± 52 min
0.34
EBL
155 ± 111 mL
106 ± 62 mL
0.32
Number of levels
BMI indicates body mass index; EBL, estimated blood loss; OR, operating room.
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LLIF
Patient No.
Reason for Revision
Time to Revision (mo)
1
Pseudarthrosis
39.6
2
Residual radiculopathy
2.7
3
Residual back pain, radiculopathy, subsidence
5.3
4
Residual back pain, radiculopathy, subsidence
3.0
5
Persistent claudication
21.0
6
Residual back pain, radiculopathy, subsidence
9.9
7
Residual radiculopathy
6.0
8
Sagittal decompensation
8.1
9
Residual back pain and radiculopathy, junctional degeneration
14.5
10
Weakness and radiculopathy
12.4
11
Recurrent radiculopathy and subsidence
3.3
12
Coronal and sagittal imbalance, fracture at proximal junctional level
3.5
LLIF indicates lateral lumbar interbody fusion.
and leg weakness, but no significant change in leg paresthesia after LLIF at the latest follow-up compared with their preoperative measures (Table 4). Interestingly, at the latest follow-up, patients who required revision surgery only showed improvement in their leg pain, but did not have improvement in their back pain, leg weakness, or leg paresthesia (Table 4). Furthermore, patients requiring revision had significantly greater postoperative leg (VAS = 5.1 vs. 2.2, P = 0.02) and back pain (VAS = 5.5 vs. 2.8, P = 0.02), and were more likely to have postoperative leg weakness (38% vs. 9%, P = 0.05) than those who did not require additional surgery.
DISCUSSION
No Revision Male:female
TABLE 2. Revision Surgery After Stand-alone
www.spinejournal.com
In this study, we analyzed 117 patients who underwent stand-alone LLIF for spinal stenosis with instability. For the majority of patients, a stand-alone procedure was sufficient to restore disc height and indirectly decompress the neural elements resulting in improvement in symptoms. The revision rate for a formal posterior decompression or posterolateral fusion after a stand-alone procedure was 10.3% at an average follow-up of 1.3 years, making stand-alone LLIF a reasonable option for patients with stenosis and an indication for fusion at the affected levels. The traditional treatment for patients with spinal stenosis that have failed conservative management is open March 2014
Copyright © 2014 Lippincott Williams & Wilkins. Unauthorized reproduction of this article is prohibited. SPINE130873.indd E328
01/02/14 11:12 AM
CLINICAL CASE SERIES
Stand-Alone LLIF for Stenosis • Nemani et al
Figure 1. Preoperative (A), postoperative (B), and postrevision surgery (C) radiographs of a patient who underwent a 2-level LLIF initially. She had persistent symptoms of stenosis, and 6 months after her initial procedure underwent formal posterior decompression and fusion using pedicle screw instrumentation. She ultimately underwent fusion and had a good clinical result with improvement of her radiculopathy. LLIF indicates lateral lumbar interbody fusion.
laminectomy with a wide decompression of the central canal, lateral recesses, and neuroforamina via a midline posterior approach. In cases of instability or deformity, this is usually done in conjunction with a fusion with or without instrumentation. There have been numerous reports on the outcomes of posterior decompression with or without fusion for stenosis and degenerative spondylolisthesis, which generally show improved outcomes compared with nonsurgical management.7–9 A posterior spinal approach with laminectomy, however, can be complicated by significant blood loss, epidural hematoma, incidental durotomy, deep infection, or postlaminectomy instability. One study reported a deep infection rate of 2% after laminectomy, requiring irrigation and debridement.10 In a series of 389 patients who underwent laminectomy for lumbar degenerative spondylolisthesis incidental durotomies occurred in 10.5% of patients, although there were no significant differences in outcomes in patients who did or did not have a durotomy.11 Epidural hematoma, although rare, is a known complication of posterior spinal surgery.12 Furthermore, iatrogenic instability can be caused by overly aggressive decompression and removal of the facet joints. In a study of 27 patients treated with posterior spinal decompression, 3.7% of patients experienced postlaminectomy instability.13 Minimally invasive approaches such as open laminotomy, microendoscopic laminotomy, or the placement of interspinous process devices have also been described to treat stenosis. Laminotomy techniques are limited by the difficulty in accessing stenosis in the lateral recess and neuroforamina due to the limited exposure. Interspinous process devices are designed to block extension at the involved spinal motion segment, and thereby prevent dynamic canal compression due to extension. Although early results were promising,14 other studies have shown no improvement at 3.5 years follow-up with a relatively high revision rate around 30%.15 Furthermore, there are data that these devices may in fact worsen neural compression in those patients with severe stenosis.16,17 Presently, these minimally invasive techniques do not offer a satisfying solution to those patients with severe symptomatic Spine
spinal stenosis, and have no role in those patients with concurrent instability. LLIF has been used with increasing frequency for the surgical management of many degenerative conditions of the lumbar spine. Especially in cases of stenosis with instability or in adult degenerative scoliosis, LLIF can be used to restore disc height and thus effect indirect foraminal decompression, achieve arthrodesis, and regain appropriate coronal and sagittal alignment.5,18,19 The additional benefit when compared with anterior lumbar interbody fusion, posterior lumbar interbody fusion, or transforaminal lumbar interbody fusion is that the anterior longitudinal ligament and posterior longitudinal ligament are preserved during the approach, thus maintaining segmental stability and using ligamentotaxis to assist in achieving deformity correction.20 There have been recent reports that support the use of LLIF in the treatment of adult degenerative scoliosis. Dakwar et al21 reported that patients with degenerative scoliosis treated with LLIF had significant improvement in 5.7 points on the VAS and a 23.7% improvement on the Oswestry Disability Index (ODI) at a mean follow-up of 11 months. Another study looked at 30 patients treated with LLIF with 14.3 months of follow-up, and found significant improvement in VAS for back pain, leg pain, and in the ODI.22 Acosta et al23 also showed a decrease in VAS and ODI, as well as significant improvement in postoperative coronal alignment in a mixed population of patients with degenerative lumbar disease. In all of these studies, however, LLIF was supplemented with a posterior approach and posterolateral fusion in the majority of patients. There is a paucity of studies that have examined the results of stand-alone LLIF. Oliveira et al24 showed radiographically that LLIF can indirectly decompress the neural elements via interbody distraction in patients with stenosis. They showed a 24.7% increase in foraminal area and a 33.1% increase in central canal diameter after stand-alone LLIF. They did not, however, report on the clinical outcomes of patients undergoing a stand-alone procedure. A more recent study also www.spinejournal.com
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Stand-Alone LLIF for Stenosis • Nemani et al
TABLE 3. Preoperative to Postoperative
Change in Radiographical Parameters Segregated by Lumbar Spinal Level and Revision Status
Level
Radiographical Parameter
Preoperative
Postoperative (Last F/u)
P
6.8 ± 2.6
2.2 ± 2.8
CLINICAL CASE SERIES
Rate of Revision Surgery After Stand-alone Lateral Lumbar Interbody Fusion for Lumbar Spinal Stenosis Venu M. Nemani, MD, PhD,* Alexander Aichmair, MD,* Fadi Taher, MD,† Darren R. Lebl, MD,* Alexander P. Hughes, MD,* Andrew A. Sama, MD,* Frank P. Cammisa, MD,* and Federico P. Girardi, MD*
Study Design. Retrospective case series. Objective. To examine the reoperation rate, specifically the need for posterior decompression and/or fusion, in a cohort of patients who underwent stand-alone lateral lumbar interbody fusion for symptomatic spinal stenosis with instability or deformity. Summary of Background Data. Lateral lumbar interbody fusion provides a minimally invasive means of achieving interbody arthrodesis and indirect foraminal decompression while avoiding the potential morbidity of traditional anterior or posterior approaches. The revision rate for formal posterior decompression after isolated lateral lumbar interbody fusion for spinal stenosis is unknown. Methods. One hundred seventeen patients who underwent stand-alone lateral lumbar interbody fusion for symptomatic spinal stenosis with an indication for fusion were included in the analysis. Detailed demographic and intraoperative data were collected. Clinical evaluation was done both preoperatively and at the final follow-up, and radiographical evaluation was done preoperatively and with the first postoperative standing radiographs. Results. A total of 10.3% of patients who underwent stand-alone lateral lumbar interbody fusion ultimately required revision surgery, most commonly for persistent radiculopathy and symptomatic implant subsidence. Average time to revision was 10.8 months. There was no difference in radiographical correction between patients who did and did not require revision surgery. From the *Hospital for Special Surgery, Weill Cornell Medical College, New York, NY; and †Department for Vascular and Endovascular Surgery, Wilhelminenspital Vienna, Vienna, Austria. Acknowledgment date: July 19, 2013. First revision date: November 1, 2013. Acceptance date: November 20, 2013. The device(s)/drug(s) is/are FDA-approved or approved by corresponding national agency for this indication. The manuscript includes unlabeled/investigational uses of the products/ devices listed below and the status of these is disclosed in the manuscript: bone morphogenetic protein-2 in lateral lumbar interbody fusion (LLIF); LLIF at more than 2 levels. No funds were received in support of this work. Relevant financial activities outside the submitted work: consultancy, royalties, stock/stock options and payment for development of educational presentations. Address correspondence and reprint requests to Venu M. Nemani, MD, PhD, Hospital for Special Surgery, 535 E 70th St., New York, NY 10021; E-mail: [email protected] DOI: 10.1097/BRS.0000000000000141
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www.spinejournal.com
Conclusion. Lateral lumbar interbody fusion provides a minimally invasive means to treat lumbar spinal stenosis with an acceptable revision rate for formal posterior decompression at early follow-up. Key words: transpsoas, XLIF, LLIF, minimally invasive, spinal stenosis, interbody fusion, revision. Level of Evidence: 4 Spine 2014;39:E326–E331
D
egenerative disease of the lumbar spine can cause pain and disability from compression of the underlying neural elements. Stenosis can occur in the central canal, lateral recess, or in the neuroforamina and has multiple etiologies, including intervertebral disc degeneration, facet hypertrophy, spondylolisthesis, or usually a combination of these factors.1 Traditional surgical approaches to spinal decompression have involved either a posterior approach to the spine followed by laminectomy/laminotomy, foraminotomy, and/or facetectomy, or an anterior approach with interbody distraction and arthrodesis.2 These approaches can be associated with significant morbidity to the patient, which have spurred the development of minimally invasive solutions to degenerative spinal disease. Lateral lumbar interbody fusion (LLIF) is an alternative, minimally invasive approach to the lumbar spine for degenerative conditions. It involves approaching the lumbar spine through a psoas-splitting retroperitoneal approach, while taking care to preserve and protect the lumbar plexus with minimal risk to these structures.3 LLIF offers several advantages compared with anterior approaches to interbody fusion including preservation of the anterior longitudinal ligament, the ability to seat the implant on dense apophyseal bone rather than on cancellous bone, and decreased risk of injury to the great vessels. A lateral annulotomy allows preservation of both the anterior longitudinal ligament and the posterior longitudinal ligament, allowing for correction of both sagittal and coronal plane deformities with an interbody device using ligamentotaxis.4 It has been shown recently that LLIF results in an increase in foraminal area via indirect compression.5 In many circumstances, LLIF is combined with formal posterior decompression and/or posterolateral fusion for a circumferential arthrodesis in patients at risk for pseudarthrosis; it March 2014
Copyright © 2014 Lippincott Williams & Wilkins. Unauthorized reproduction of this article is prohibited. SPINE130873.indd E326
01/02/14 11:12 AM
CLINICAL CASE SERIES is not known, however, the efficacy of stand-alone LLIF to treat symptomatic lumbar spinal stenosis in carefully selected patients with degenerative scoliosis or instability who may not be able to tolerate, or may not need, both anterior and posterior procedures. The goal of this study is to determine the rate of revision surgery for formal posterior decompression in patients who underwent stand-alone LLIF for symptomatic lumbar spinal stenosis.
MATERIALS AND METHODS Patients Institutional review board approval was obtained for this study; a waiver of the need to obtain informed consent for this retrospective analysis was granted by the board. Patients were eligible for inclusion if they had undergone stand-alone LLIF for a preoperative diagnosis that included lumbar spinal stenosis with an indication for interbody fusion such as instability alone or degenerative scoliosis with resultant instability. Stenosis was diagnosed in patients with clinical symptoms of radiculopathy or neurogenic claudication that had evidence on CT myelogram or MRI of either foraminal or lateral recess stenosis that correlated with the clinical findings. Patients were considered to have instability if they had a degenerative spondylolisthesis with evidence of motion on flexion/ extension views or a significant component of mechanical back pain. Scoliosis was defined as a coronal plane deformity measuring more than 10°. Both preoperative and postoperative radiographs had to be available for analysis in the Hospital for Special Surgery picture archiving and communication system. Patients were excluded if they had had any previous anterior or posterior surgery at the affected level, including laminotomy, laminectomy, and/or posterolateral, or interbody fusion. All operations were performed by the 4 senior authors (A.P.H., A.A.S., F.P.C., and F.P.G.), all fellowshiptrained spine surgeons, at a single institution.
Surgical Technique Details of the surgical technique have been described previously.6 In cases of degenerative scoliosis, the operated levels were approached through the side of the concavity to reach multiple levels through a single incision; otherwise, the laterality of the approach was based on the accessibility of the L4–L5 disc space in relation to the iliac crest. The psoas muscle was split under direct visualization carefully3 avoiding the traversing nerves with electromyography probes also used to avoid neural injury. A self-retaining retractor with illumination was placed after fluoroscopic confirmation of the correct disc space. After thorough discectomy, the disc spaces were sized with trial components using preoperative templating and intraoperative fluoroscopy for additional confirmation. Cages were packed with bone graft materials according to surgeon preference. Postoperatively, patients were allowed to ambulate as tolerated under the careful supervision of a physical therapist. All patients had standing radiographs of the lumbar spine performed prior to discharge. Spine
Stand-Alone LLIF for Stenosis • Nemani et al
Evaluation Demographic data were collected, as well as operating time, estimated blood loss, and operation-related complications. Clinical evaluation was done both preoperatively and at the final follow-up, and radiographical evaluation was done preoperatively and with the first postoperative standing radiographs. Radiographical evaluation included measurements of anterior disc height, posterior disc height, interpedicular height, foraminal area, and endplate angle. Office charts were reviewed to record preoperative and postoperative back and leg pain scores as well as neurological symptoms.
Statistical Analysis Analyses were first performed to determine the effects of stand-alone LLIF on visual analogue scale (VAS) pain scores, weakness, paresthesia, and radiographical parameters. Pre- to postoperative changes in leg and back VAS pain scores were assessed with paired t tests. Differences between pre- and postoperative leg weakness and paresthesia were assessed with McNemar tests. Pre- to postoperative changes in radiographical parameters (anterior height, posterior height, foraminal area, interpedicular height, and endplate angle) were assessed independently at each level with paired t tests, or Wilcoxon signed-rank tests if the data were non-normally distributed. Statistical assessment of radiographical parameters at L1–L2 was not possible because the revision group contained only 1 patient with a procedure at this level. Subsequently, differences in these patient parameters were assessed between patients who did and did not ultimately require revision surgery. Age at surgery, body mass index, operating room time, estimated blood loss, and leg and back VAS pain scores (preoperative, postoperative, and pre- to postoperative change) were assessed with independent t tests or with Mann-Whitney U tests. Associations between revision status and weakness, paresthesia, lumbar level, and the number of levels were assessed with the Fisher exact tests. Differences in radiographical parameters between nonrevision and revision groups were assessed independently at each level with independent t tests or with Mann-Whitney U tests. The level of significance for all tests was α = 0.05, and results presented are significant unless stated otherwise.
RESULTS Between March 2006 and April 2012, 451 patients underwent LLIF at Hospital for Special Surgery by the senior authors. Of these, 117 patients underwent stand-alone LLIF and met the inclusion and exclusion criteria to be included in the analysis. There were 83 females and 34 males, and average age was 63.6 years (range, 30–87). Average body mass index was 27.4. The average number of levels operated on was 2.0 (range, 1–4): 37 underwent a single-level procedure, 42 underwent a 2-level procedure, 34 underwent a 3-level procedure, and 4 underwent a 4-level procedure. Operating time averaged 146 minutes and estimated blood loss averaged 144 mL. Average follow-up was 15.6 months (range, 1.3–52.9 mo). After LLIF, patients had less leg pain (P < 0.001), back pain (P < 0.001), www.spinejournal.com
E327
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01/02/14 11:12 AM
CLINICAL CASE SERIES
Stand-Alone LLIF for Stenosis • Nemani et al
and leg weakness (P = 0.006), whereas leg paresthesia were unchanged (P = 0.20). All radiographical parameters were significantly improved at every lumbar spinal level after LLIF. There were 12 patients (10.3%) who ultimately required revision surgery for persistent symptoms during the followup period. There was no difference in demographic data or perioperative variables of patients who did and did not require revision surgery (Table 1). The average time to revision was 10.8 months (range, 2.6 – 39.6 mo) with 6 revisions being performed within 6 months, and 8 of 12 performed within 1 year. The most common reasons for revision surgery were persistent stenosis and symptomatic implant subsidence (Table 2). All patients except 2 who required revision ultimately had posterior decompression with instrumented fusion using pedicle screw fixation. One patient had laminotomies alone and 1 patient had a laminectomy with noninstrumented in situ fusion. Figure 1 shows images representative of a patient who underwent revision surgery for persistent symptoms of stenosis. Across all levels, LLIF resulted in a 53% increase in foraminal area (P < 0.001). The increase in foraminal area was similar but less at more caudal levels (L1–L2 = 61%, L2–L3 = 61%, L3–L4 = 53%, L4–L5 = 45%), and significant at every level (P < 0.001). Comparison of radiographical parameters when comparing pre- and postoperative radiographs showed essentially no difference between patients who ultimately did or did not require revision surgery, except for a greater increase in posterior disc height in patients ultimately requiring revision surgery (Table 3). Most importantly, there was no difference in the increase in overall foraminal area in patients who did and did not require revision surgery (53% increase in cases not requiring revision, 62% in cases requiring revision, P = 0.46). There was also no difference when this was analyzed at each individual spinal level. Overall lumbar lordosis measured across all patients increased from 43° to 47° after stand-alone LLIF (P = 0.01). There was no significant difference between the change in lumbar lordosis after surgery in patients who did and did not ultimately require revision surgery. Patients who ultimately did not require revision surgery showed significant improvement in their leg pain, back pain,
TABLE 1. Demographics and Perioperative
Variables
Revision
P
30:75
4:12
0.73
Age
64.0 ± 12.0
60.2 ± 14.0
0.31
BMI
27.3 ± 5.4
28.7 ± 4.0
0.42
2.1
1.8
0.59
OR time
148 ± 47 min
134 ± 52 min
0.34
EBL
155 ± 111 mL
106 ± 62 mL
0.32
Number of levels
BMI indicates body mass index; EBL, estimated blood loss; OR, operating room.
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LLIF
Patient No.
Reason for Revision
Time to Revision (mo)
1
Pseudarthrosis
39.6
2
Residual radiculopathy
2.7
3
Residual back pain, radiculopathy, subsidence
5.3
4
Residual back pain, radiculopathy, subsidence
3.0
5
Persistent claudication
21.0
6
Residual back pain, radiculopathy, subsidence
9.9
7
Residual radiculopathy
6.0
8
Sagittal decompensation
8.1
9
Residual back pain and radiculopathy, junctional degeneration
14.5
10
Weakness and radiculopathy
12.4
11
Recurrent radiculopathy and subsidence
3.3
12
Coronal and sagittal imbalance, fracture at proximal junctional level
3.5
LLIF indicates lateral lumbar interbody fusion.
and leg weakness, but no significant change in leg paresthesia after LLIF at the latest follow-up compared with their preoperative measures (Table 4). Interestingly, at the latest follow-up, patients who required revision surgery only showed improvement in their leg pain, but did not have improvement in their back pain, leg weakness, or leg paresthesia (Table 4). Furthermore, patients requiring revision had significantly greater postoperative leg (VAS = 5.1 vs. 2.2, P = 0.02) and back pain (VAS = 5.5 vs. 2.8, P = 0.02), and were more likely to have postoperative leg weakness (38% vs. 9%, P = 0.05) than those who did not require additional surgery.
DISCUSSION
No Revision Male:female
TABLE 2. Revision Surgery After Stand-alone
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In this study, we analyzed 117 patients who underwent stand-alone LLIF for spinal stenosis with instability. For the majority of patients, a stand-alone procedure was sufficient to restore disc height and indirectly decompress the neural elements resulting in improvement in symptoms. The revision rate for a formal posterior decompression or posterolateral fusion after a stand-alone procedure was 10.3% at an average follow-up of 1.3 years, making stand-alone LLIF a reasonable option for patients with stenosis and an indication for fusion at the affected levels. The traditional treatment for patients with spinal stenosis that have failed conservative management is open March 2014
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Stand-Alone LLIF for Stenosis • Nemani et al
Figure 1. Preoperative (A), postoperative (B), and postrevision surgery (C) radiographs of a patient who underwent a 2-level LLIF initially. She had persistent symptoms of stenosis, and 6 months after her initial procedure underwent formal posterior decompression and fusion using pedicle screw instrumentation. She ultimately underwent fusion and had a good clinical result with improvement of her radiculopathy. LLIF indicates lateral lumbar interbody fusion.
laminectomy with a wide decompression of the central canal, lateral recesses, and neuroforamina via a midline posterior approach. In cases of instability or deformity, this is usually done in conjunction with a fusion with or without instrumentation. There have been numerous reports on the outcomes of posterior decompression with or without fusion for stenosis and degenerative spondylolisthesis, which generally show improved outcomes compared with nonsurgical management.7–9 A posterior spinal approach with laminectomy, however, can be complicated by significant blood loss, epidural hematoma, incidental durotomy, deep infection, or postlaminectomy instability. One study reported a deep infection rate of 2% after laminectomy, requiring irrigation and debridement.10 In a series of 389 patients who underwent laminectomy for lumbar degenerative spondylolisthesis incidental durotomies occurred in 10.5% of patients, although there were no significant differences in outcomes in patients who did or did not have a durotomy.11 Epidural hematoma, although rare, is a known complication of posterior spinal surgery.12 Furthermore, iatrogenic instability can be caused by overly aggressive decompression and removal of the facet joints. In a study of 27 patients treated with posterior spinal decompression, 3.7% of patients experienced postlaminectomy instability.13 Minimally invasive approaches such as open laminotomy, microendoscopic laminotomy, or the placement of interspinous process devices have also been described to treat stenosis. Laminotomy techniques are limited by the difficulty in accessing stenosis in the lateral recess and neuroforamina due to the limited exposure. Interspinous process devices are designed to block extension at the involved spinal motion segment, and thereby prevent dynamic canal compression due to extension. Although early results were promising,14 other studies have shown no improvement at 3.5 years follow-up with a relatively high revision rate around 30%.15 Furthermore, there are data that these devices may in fact worsen neural compression in those patients with severe stenosis.16,17 Presently, these minimally invasive techniques do not offer a satisfying solution to those patients with severe symptomatic Spine
spinal stenosis, and have no role in those patients with concurrent instability. LLIF has been used with increasing frequency for the surgical management of many degenerative conditions of the lumbar spine. Especially in cases of stenosis with instability or in adult degenerative scoliosis, LLIF can be used to restore disc height and thus effect indirect foraminal decompression, achieve arthrodesis, and regain appropriate coronal and sagittal alignment.5,18,19 The additional benefit when compared with anterior lumbar interbody fusion, posterior lumbar interbody fusion, or transforaminal lumbar interbody fusion is that the anterior longitudinal ligament and posterior longitudinal ligament are preserved during the approach, thus maintaining segmental stability and using ligamentotaxis to assist in achieving deformity correction.20 There have been recent reports that support the use of LLIF in the treatment of adult degenerative scoliosis. Dakwar et al21 reported that patients with degenerative scoliosis treated with LLIF had significant improvement in 5.7 points on the VAS and a 23.7% improvement on the Oswestry Disability Index (ODI) at a mean follow-up of 11 months. Another study looked at 30 patients treated with LLIF with 14.3 months of follow-up, and found significant improvement in VAS for back pain, leg pain, and in the ODI.22 Acosta et al23 also showed a decrease in VAS and ODI, as well as significant improvement in postoperative coronal alignment in a mixed population of patients with degenerative lumbar disease. In all of these studies, however, LLIF was supplemented with a posterior approach and posterolateral fusion in the majority of patients. There is a paucity of studies that have examined the results of stand-alone LLIF. Oliveira et al24 showed radiographically that LLIF can indirectly decompress the neural elements via interbody distraction in patients with stenosis. They showed a 24.7% increase in foraminal area and a 33.1% increase in central canal diameter after stand-alone LLIF. They did not, however, report on the clinical outcomes of patients undergoing a stand-alone procedure. A more recent study also www.spinejournal.com
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TABLE 3. Preoperative to Postoperative
Change in Radiographical Parameters Segregated by Lumbar Spinal Level and Revision Status
Level
Radiographical Parameter
Preoperative
Postoperative (Last F/u)
P
6.8 ± 2.6
2.2 ± 2.8
