minimally invasive laminectomy for lumbar spinal stenosis in … · m. alimi et al. 340 j neurosurg...
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spine
J Neurosurg Spine Volume 22 • April 2015
cliNical articleJ Neurosurg Spine 22:339–352, 2015
Symptomatic lumbar spinal stenosis (LSS) unrespon-sive to conservative therapy is commonly treated us-ing direct surgical decompression.33 Current guide-
lines recommend additional arthrodesis in patients with LSS and preexisting spondylolisthesis.21,24,31,49,50,52 Various techniques are currently used for direct decompression of LSS. Standard open laminectomy has been shown to be an effective procedure for LSS decompression.36,46,54,60–64,66 However, wide laminectomies violating stabilizing bony and ligamentous structures may exacerbate preexisting spondylolisthesis.19,37 Minimally invasive laminectomy
through tubular or similar retractors is a recently intro-duced alternative procedure for decompression of LSS.47 This technique avoids detachment of the paraspinal mus-cles and may promote preservation of stabilizing ligamen-tous and bony spinal structures.29,30,39,41–45 Biomechanical studies indicate that compared with open laminectomy, minimally invasive laminectomy may result in less post-operative instability.1,6,12,23,34
The current study had two main goals: first, to evalu-ate the efficacy of minimally invasive laminectomy as a decompressive procedure for the treatment of patients with
abbreviatioNS BMI = body mass index; LSS = lumbar spinal stenosis; MCID = minimum clinically important difference; ODI = Oswestry Disability Index; VAS = visual analog scale.accompaNyiNg editorial See pp 337–338. DOI: 10.3171/2014.8.SPINE14687.Submitted June 21, 2013. accepted November 13, 2014. iNclude wheN citiNg Published online January 30, 2015; DOI: 10.3171/2014.11.SPINE13597.diScloSure The authors report no conflict of interest concerning the materials or methods used in this study or the findings specified in this paper. Dr. Härtl is a consul-tant for DePuy-Synthes, Lanx, Spine Wave, Brainlab.
Minimally invasive laminectomy for lumbar spinal stenosis in patients with and without preoperative spondylolisthesis: clinical outcome and reoperation ratesmarjan alimi, md, christoph p. hofstetter, md, phd, Se young pyo, md, phd, danika paulo, bS, and roger härtl, md
Weill Cornell Brain and Spine Center, Department of Neurological Surgery, Weill Cornell Medical College, NewYork-Presbyterian Hospital, New York, New York
obJect Surgical decompression is the intervention of choice for lumbar spinal stenosis (LSS) when nonoperative treatment has failed. Standard open laminectomy is an effective procedure, but minimally invasive laminectomy through tubular retractors is an alternative. The aim of this retrospective case series was to evaluate the clinical and radiographic outcomes of this procedure in patients who underwent LSS and to compare outcomes in patients with and without pre-operative spondylolisthesis.methodS Patients with LSS without spondylolisthesis and with stable Grade I spondylolisthesis who had undergone minimally invasive tubular laminectomy between 2004 and 2011 were included in this analysis. Demographic, periopera-tive, and radiographic data were collected. Clinical outcome was evaluated using the Oswestry Disability Index (ODI) and visual analog scale (VAS) scores, as well as Macnab’s criteria.reSultS Among 110 patients, preoperative spondylolisthesis at the level of spinal stenosis was present in 52.5%. At a mean follow-up of 28.8 months, scoring revealed a median improvement of 16% on the ODI, 2.75 on the VAS back, and 3 on the VAS leg, compared with the preoperative baseline (p < 0.0001). The reoperation rate requiring fusion at the same level was 3.5%. Patients with and without preoperative spondylolisthesis had no significant differences in their clinical outcome or reoperation rate.coNcluSioNS Minimally invasive laminectomy is an effective procedure for the treatment of LSS. Reoperation rates for instability are lower than those reported after open laminectomy. Functional improvement is similar in patients with and without preoperative spondylolisthesis. This procedure can be an alternative to open laminectomy. Routine fusion may not be indicated in all patients with LSS and spondylolisthesis.http://thejns.org/doi/abs/10.3171/2014.11.SPINE13597Key wordS lumbar spinal stenosis; spondylolisthesis; minimally invasive laminectomy; tubular retractors; Oswestry Disability Index; visual analog scale; reoperation
339©AANS, 2015
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LSS. The second aim was to compare the clinical and ra-diographic outcomes of minimally invasive laminectomy in patients with and without preexisting stable spondylo-listhesis.
To better achieve the first goal, outcomes for LSS fol-lowing minimally invasive laminectomies in our retro-spective case series were compared with those achieved via other surgical interventions described in the literature.
methodspatient population
Institutional approval for this study was obtained from Weill Cornell Medical College. Data for this retrospective case series were extracted from the prospectively collect-ed hospital database. We sought all patients who had un-dergone minimally invasive laminectomy for decompres-sion of LSS between 2004 and 2011. Demographic and perioperative data on these patients were collected. For the demographic data, age, sex, body mass index (BMI), smoking status, history of diabetes, and steroid medica-tion use were recorded. Operative and anesthesia reports as well as hospital charts were reviewed to add data on estimated blood loss, number and levels of surgery, com-plications, and length of hospital stay. The presence of preoperative spondylolisthesis was determined on radio-graphic studies. Postoperative radiographs were evaluated to assess changes in the amount and grade of previous spondylolisthesis and/or the development of new slippage. Standardized radiographs were used for assessments, both preoperatively and postoperatively. Patients who had pre-sented with preoperative spondylolisthesis and primarily mechanical back pain and/or instability on flexion/exten-sion films were not included in this study. Comparisons were made between the outcomes of minimally invasive laminectomies in our cohort and the outcomes of other decompressive surgical interventions for LSS, as pub-lished in the literature.
operative procedureWith the patient lying prone under general anesthesia,
a small skin incision is made overlying the target level ap-proximately 1.5 cm lateral to the midline. An 18- or 19-mm tubular retractor is placed over a series of tubular di-lators for retraction, and under the microscope, the inferior edge of the lamina and the inferior edge and base of the spinous process are exposed (Fig. 1). The decompression is performed step by step starting with an ipsilateral par-tial laminectomy using a 3-mm curved matchstick drill bit and bayonet-shaped 2- and 3-mm Kerrison punches (Fig. 2). To achieve appropriate visualization of contralateral structures, the operating table is tilted away from the sur-geon and the tubular retractor is angled medially. Next, the spinous process and the contralateral lamina are undercut using the drill and rongeurs (Fig. 3). The ligamentum fla-
Fig. 1. An 18- or 19-mm tubular retractor is placed over a series of tu-bular dilators for retraction, and under the microscope, the inferior edge of the lamina and the inferior edge and base of the spinous process are exposed. Illustration by Thomas Graves. Copyright Roger Härtl. Pub-lished with permission.
Fig. 2. The decompression is performed starting with an ipsilateral par-tial laminectomy using a 3-mm curved matchstick drill bit and bayonet-shaped 2- and 3-mm Kerrison punches. Illustration by Thomas Graves. Copyright Roger Härtl. Published with permission.
Fig. 3. The operating table is tilted away from the surgeon, and the tubular retractor is angled medially to achieve appropriate visualization of contralateral sublaminar structures. Next, the spinous process and the contralateral lamina are undercut using the drill and rongeurs. The ligamentum flavum is completely exposed cranially until its insertion under the lamina. Illustration by Thomas Graves. Copyright Roger Härtl. Published with permission.
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vum is completely exposed bilaterally and cranially until its insertion under the lamina. During the laminectomy, the ligamentum flavum protects the dura. Next, we insert a nerve hook and then a Kerrison rongeur in the midline where the two leaves of the ligamentum flavum meet, an area that is typically identified by the presence of epidural fat (Figs. 4 and 5). These techniques minimize risks of in-jury to the dura. The ligamentum flavum is then removed (Fig. 6). Great care is taken to completely decompress the lateral recess and entirely remove the yellow ligament. This also allows visualization and decompression, if need-ed, of the contralateral exiting and traversing nerve root.
Adequate decompression is always confirmed by iden-tifying certain landmark structures and achieving particu-lar surgical end points, as follows: contralaterally and cau-dally by palpating the pedicle using a ball tip instrument, cranially by confirming complete removal of the yellow ligament and the absence of bony compression of the dura mater, and ipsilaterally by complete removal of the liga-mentum flavum and by clear identification of the lateral aspect of the thecal sac and inspection of the traversing nerve root. As the next and final step, the table and re-tractor are brought back into the initial position, and the ipsilateral decompression is completed.
clinical outcome evaluationThe preoperative and latest available follow-up Os-
westry Disability Index (ODI)14 and visual analog scale (VAS) scores for back, buttock, and leg pain were col-lected and compared. Functional outcome was evaluated using Macnab’s criteria.35 Patients without late follow-up outcome scores recorded in the hospital’s database were contacted by phone, and the ODI and VAS pain scores and Macnab’s level of satisfaction were assessed. These patients were also asked if they had undergone any further lumbar spine surgery at outside medical centers.
A 12-point improvement on the ODI3,20,22 and 3-point improvement on the VAS were regarded as the mini-
mum clinically important difference (MCID).15,16,22 As for functional outcome, 4 levels were defined according to Macnab’s criteria: excellent (no pain; no restriction of activity), good (occasional back or leg pain of sufficient se-verity to interfere with the ability to work), fair (improved functional capacity but handicapped by intermittent pain of sufficient severity to curtail work), or poor (no improve-ment or insufficient improvement to enable increase in ac-tivities; further operative interventions required).35
The patients who required another operation and un-derwent a second surgery at our and other institutions were identified. The indication for the second operation and a description of the procedure were recorded.
radiographic evaluationIn patients with postoperative radiographic studies, the
Fig. 4. A nerve hook is inserted in the midline where the two leaves of the ligamentum flavum meet, an area that is typically identified by the presence of epidural fat. Illustration by Thomas Graves. Copyright Roger Härtl. Published with permission.
Fig. 6. Dural exposure and decompression after complete removal of the ligamentum flavum. The contralateral approach allows visualization and decompression, if needed, of the contralateral exiting and traversing nerve root. Illustration by Thomas Graves. Copyright Roger Härtl. Pub-lished with permission.
Fig. 5. The ligamentum flavum is then carefully removed using Kerrison rongeurs. Illustration by Thomas Graves. Copyright Roger Härtl. Pub-lished with permission.
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J Neurosurg Spine Volume 22 • April 2015342
latest study was used to assess changes in the amount and grade of previous spondylolisthesis and/or development of new slippage.
Statistical analysisPatients with preoperative radiographic studies, who
had been evaluated for the presence or absence of pre-operative spondylolisthesis, were divided into 2 groups: patients with concomitant preoperative spondylolisthesis and those without. We reported results for the entire group of patients as well as for each of the 2 groups separately. Comparisons were made between the 2 different groups and between each group and the entire study group.
Continuous variables are shown as the mean ± stan-dard deviation. Percentages were calculated for categori-cal variables. Differences in categorical variables were as-sessed using the chi-square test. Differences in continuous variables were tested using the independent t-test, and dif-ferences for repeatedly measured variables were assessed using the repeated measures t-test. All analyses were per-formed using appropriate statistical software (SPSS, ver-sion 18.0.0.1, SPSS Inc.). A p value of < 0.05 was consid-ered statistically significant.
resultspatient demographics
One hundred ten consecutive patients, 58 males and 52 females, with isolated LSS who had undergone minimally
invasive laminectomy surgery for decompression were in-cluded in our study. The mean age at surgery was 68.5 years (range 32–89 years; Table 1), and the mean BMI was 28.6 kg/m2. A history positive for smoking, diabetes, and steroid medication use was present in 11.8%, 14.8%, and 4.6% of patients, respectively. In 97 patients with available preoperative imaging, spondylolisthesis Grade I was pres-ent in 51 patients (52.6%), whereas 46 patients (47.4%) did not have preoperative spondylolisthesis.
Surgical detailsOne-, 2-, and 3-level surgeries were done in 57 patients
(51.8%), 47 (42.7%), and 6 (5.4%), respectively. A total of 169 levels were operated on in 110 patients, and the most common level of surgery was L4–5 (50.3% of cases). The L3–4 level made up 29% of cases; L5–S1, 11.2%; and L2–3, the remaining 9.5%. The median estimated blood loss for 1-, 2-, and 3-level surgeries was 25, 50, and 150 ml, respectively (Table 2). More than half of the patients (56%) were discharged on either the day of surgery or the first postoperative day, while the mean duration of hospitaliza-tion was 2.2 ± 2.63 days (range 0–13 days).
clinical outcomeThe mean preoperative ODI was 45.3 ± 19.62 (range
0–88; Tables 3 and 4), which decreased to 28.9 ± 21.76 at a mean follow-up of 28.8 months. An MCID (defined as improvement on the ODI by 12 or more points3,20,22)
table 1. Summary of preoperative characteristics in 110 patients with lSS with and without spondylolisthesis
Characteristic All Patients Patients w/ Spondylolisthesis Patients w/o Spondylolisthesis p Value
No. of patients 110 51 46Mean age at surgery in yrs* 68.5 ± 12.77 72.4 ± 12.69 64.4 ± 12.33 0.002†Sex Male 58 (52.7%) 24 (47.1%) 23 (50%) 0.84 Female 52 (47.3%) 27 (52.9%) 23 (50%)Mean BMI in kg/m²* 28.6 ± 4.74 28.5 ± 4.94 29.2 ± 4.68 0.49Diabetes Yes 14.8% 12.2% 19.6% 0.40 No 85.2% 87.8% 80.4%Smoking Yes 11.8% 9.1% 7.9% 0.84 No 88.2% 90.9% 92.1%Steroid medication use Yes 4.6% 2% 6.5% 0.35 No 95.4% 98% 93.5%Preop spondylolisthesis level‡ L2–3 5 (8.1%) 5 (8.1%) — — L3–4 15 (24.2%) 15 (24.2%) — — L4–5 37 (59.6%) 37 (59.6%) — — L5–S1 5 (8.1%) 5 (8.1%) — —
— = not applicable.* Values expressed as the mean ± standard deviation.† Statistically significant.‡ Fifty-one patients, 62 levels.
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was achieved in 54.8% of patients (Table 5). The median preoperative VAS back, buttock, and leg pain scores were 8, 4.5, and 4.6, respectively. At the latest follow-up, the median VAS back, buttock, and leg pain scores decreased to 3.5, 0, and 0, respectively. Three-point improvement on the VAS was regarded as the MCID.15,16,22 The MCID for VAS back, buttock, and leg pain was achieved in 50.0%, 45.2%, and 52.4% of the patients, respectively. All 4 scores indicated statistically significant improvement at the latest follow-up. A comparison of ODI and VAS outcome scores in patients with and without preoperative spondylolisthe-sis showed no significant difference between the 2 groups (Tables 4 and 5).
Functional outcome, as assessed using Macnab’s crite-ria,35 was excellent and good in 71.6% of the patients. A comparison of Macnab’s results in patients with and with-out preoperative spondylolisthesis showed no significant difference (Table 6).
Sixteen cases with dural injuries were not associated with CSF leakage and were intraoperatively repaired us-ing DuraSeal. There were no intraoperative and/or inpa-tient complications. At a mean follow-up of 28 months, the reoperation rate at the same level (with or without sur-gery at a different level) for the entire study group was 12.9%. Among the 11 reoperated patients, 7 (8.2%) un-derwent repeat decompression without fusion at the same level (with or without surgery at a different level), whereas in 3 patients (3.5%) a fusion was performed at the same level. Comparison of total reoperation rates as well as re-operation with fusion in patients with and without preop-erative spondylolisthesis showed no significant difference between the 2 groups (Table 7).
radiographic resultsBecause postoperative imaging was not routinely done
in this retrospective case series, only a limited number of patients (41) had available follow-up imaging. In patients with preoperative spondylolisthesis the mean slippage pri-or to surgery was 5.5 ± 3.04 mm, which increased to 6.4 ± 3.5 at the latest follow-up. This increase did not reach statistical significance. None of the imaged patients with-out preoperative spondylolisthesis demonstrated any slip-page at the latest follow-up. Although we report the radio-graphic follow-up for the study group, we emphasize that radiographic outcome was not used to draw definite con-clusions in this study. Instead, clinical outcome has been mainly used as evidence to draw possible conclusions.
learning curveThe first 55 patients were grouped into an early experi-
ence group and the second 55 cases into a late experience group. Operative time, estimated blood loss, dural injury rates, clinical outcome, Macnab’s criteria, and reoperation rate were compared between these 2 groups. Comparisons showed no statistically significant difference in operative time, estimated blood loss, clinical outcome, and Macnab
table 2. Summary of surgical details in 110 patients who underwent laminectomy
Characteristic All Patients Patients w/ Spondylolisthesis Patients w/o Spondylolisthesis p Value
No. of patients 110 51 46No. of operated levels 169 78 71No. of levels/patient 1 57 (51.8%) 28 (54.9%) 23 (50%) 2 47 (42.7%) 19 (37.3%) 21 (45.7%) 0.60 3 6 (5.5%) 4 (7.8%) 2 (4.3%)Level of surgery L2–3 16 (9.5%) 9 (11.5%) 5 (7%) 0.39 L3–4 49 (29.0%) 19 (24.4%) 23 (32.4%) 0.22 L4–5 85 (50.3%) 42 (53.8%) 36 (50.7%) 0.62 L5–S1 19 (11.2%) 8 (10.3%) 7 (9.9%) 0.94Estimated blood loss (ml)* 1-level op 25 (0;550) 20 (0;150) 50 (0;550) 0.04† 2-level op 50 (0;400) 75 (0;200) 50 (0;400) 0.61 3-level op 150 (100;300) 125 (100;300) 250‡ 0.80Hospital stay (days)* 1 (0;13) 1 (0;12) 1 (0;13) 0.28
* Values expressed as the median (min;max). † Statistically significant.‡ Single case.
table 3. Summary of clinical outcome measures in 84 patients with available preoperative and postoperative data*
Measure Preop Last FU p Value
Mean preop ODI (out of 100)
45.3 ± 19.62 28.9 ± 21.76 <0.0001†
VAS back 8 (0;10) 3.5 (0;10) <0.0001†VAS buttock 4.5 (0;10) 0 (0;10) <0.0001†VAS leg 4.6 (0;10) 0 (0;8) <0.0001†
FU = follow-up.* The mean follow-up duration was 28.8 ± 19.39 months.† Statistically significant.
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results in the 2 groups. Dural injuries occurred in 15 cases (27.3%) in the early experience group and in only 1 case (1.8%) in the late experience group (p < 0.0001). Moreover, 9 patients (23.7%) in the early experience group needed reoperation, whereas only 2 patients (4.2%) in the late ex-perience group underwent a second operation (p = 0.008). The follow-up duration for clinical outcome and Macnab’s criteria estimation was 45.7 ± 17.03 months in the early group and 15.5 ± 7.03 months in the late experience group. Similarly, the follow-up duration for reoperation was 44.5 ± 18.34 months in the early group and 15.5 ± 7.03 months in the late experience group. Nonetheless, the period be-tween the first and second operation was found to be simi-lar and not statistically different between the early and late experience groups. The median interval between the first surgery and the reoperation was 16.9 months (minimum 0.2; maximum 39.7).
discussionbackground
Several less-invasive surgical techniques have been in-
troduced for direct decompression of the lumbar spine. The introduction of a less-invasive retractor system dates back to 1991 when Caspar and colleagues proposed the use of less-invasive specular retractors for discectomies.7,17 Independently, Foley and Smith, in 1997, described the tubular microendoscopic discectomy in the lumbar spine, in which endoscopes were used through tubular retrac-tors to perform a discectomy.18 They had worked on this approach in the laboratory since 1994, and the first clini-cal case was performed in early 1996 (K. Foley, personal communication, 2004). The METRx tubular retractor system was introduced in 2003 and permitted the use of the microscope, which allows excellent illumination and visualization of pathology. The use of tubular retractors to access spinal pathology has been associated with sev-eral biomechanical and clinical advantages: First, the ap-proach through a minimally invasive retractor can spare attachments of paraspinal ligaments and muscles, which stabilize the spine. Minimizing injury to paraspinal liga-ments and muscles allows for postoperative strengthening of back muscles and maintains stabilization of the motion
table 4. Summary of clinical improvement in patients with and without spondylolisthesis
Parameter All Patients Patients w/ Spondylolisthesis Patients w/o Spondylolisthesis p Value
No. of patients* 84 37 38FU duration in mos 0.81 Mean ± SD 28.5 ± 19.63 26.7 ± 18.60 27.7 ± 19.43 Median (min;max) 22.8 (6.2;74.3) 20.7 (8.5;74.3) 20.5 (6.2;74.3)% ODI improvement 16.00 (−48.8;62.2) 11.00 (−37.8;62.2) 19.45 (−48.8;53.0) 0.55VAS back improvement (points) 2.75 (−10;10) 3.00 (−6;10) 2.00 (−10;9) 0.26VAS buttock improvement (points) 2.25 (−10;9) 3.50 (−10;8) 2.50 (−5;9) 0.54VAS leg improvement (points) 3.00 (−5;10) 3.00 (−1;9) 3.50 (−5;10) 0.88
* Preoperative and follow-up outcome scores were available in 84 patients; 9 of these patients had no preoperative imaging data.
table 5. Summary of improvements on odi and vaS
Parameter All Patients Patients w/ Spondylolisthesis Patients w/o Spondylolisthesis p Value
Total 84 37 38w/ ODI improvement 59 (70.2%) 24 (64.9%) 26 (68.4%) 0.80w/ MCID in ODI 46 (54.8%) 18 (48.6%) 23 (60.5%) 0.35w/ VAS back pain improvement 56 (66.7%) 25 (67.6%) 24 (63.2%) 0.80w/ MCID in VAS back pain 42 (50.0%) 21 (56.8%) 17 (44.7%) 0.35w/ VAS buttock pain improvement 55 (65.5%) 26 (70.3%) 24 (63.2%) 0.62w/ MCID in VAS buttock pain 38 (45.2%) 19 (51.4%) 17 (44.7%) 0.64w/ VAS leg pain improvement 62 (73.8%) 30 (81.1%) 24 (63.2%) 0.12w/ MCID in VAS leg pain 44 (52.4%) 19 (51.4%) 20 (52.6%) 0.91
table 6. Summary of macnab results
Parameter All Patients Patients w/ Spondylolisthesis Patients w/o Spondylolisthesis p Value of Difference
No. of patients* 74 32 34 Outcome Excellent & good 53 (71.6%) 23 (71.9%) 26 (76.5%) 0.67 Fair & poor 21 (28.4%) 9 (28.1%) 8 (23.5%)
* Data were only available in the listed number of patients.
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segment. Second, the minimally invasive approach allows contralateral decompression of the spinal canal, lateral recess, and foramen without another incision while also sparing part of the lamina, spinous process, and interspi-nous ligaments.2,67
The anatomical description and clinical results of a uni-lateral laminotomy for contralateral decompression were first reported by Spetzger in 1997.55,56 Similar observations were also described by McCulloch in 1999.38,59 Adopting tubular retractors for this approach led to excellent de-compression of the contralateral lateral recess and even foraminal disc herniations and contralateral foraminal stenosis.2,67 For example, we reported that synovial cysts can be resected safely and without compromising the facet joint by approaching them from the contralateral side and from “normal” dura and anatomy via tubular retractors.28 Biomechanical and laboratory results indicate that lami-nectomy via tubular retractors or bilateral laminotomies are associated with less destabilization than an open bilat-eral laminectomy.1,5,6,12,23,34,57 In their biomechanical study, Lee et al. demonstrated that bilateral laminotomy was as-sociated with significantly less hypermobility and stiff-ness reduction than a full laminectomy, and they proposed that this could be attributed to preservation of the central posterior osteoligamentous structures in laminotomy.34 In summary, minimally invasive laminectomy via tubular and similar retractors achieves effective neural decom-pression with simultaneous preservation of the stability of motion segments. Figure 7 features a case of LSS in which was achieved complete decompression and a favorable outcome after treatment via this technique.
minimally invasive decompression of lSSMinimally invasive laminectomy through tubular re-
tractors has been shown in previous studies to be a feasible and effective technique for treating LSS.8,30,39,41–45 In the present study we evaluated the outcome of this procedure in a larger group of patients with a longer duration of fol-low-up. The results were compared with those of other de-compressive procedures published in the literature (Table 8). Our study produced results corroborating the findings in previous studies on the same technique. Parikh et al. and Pao et al. reported higher ODI and pain score improve-
ments than we did in the present study;44,45 this may be explained to some extent by the shorter follow-up duration in those studies (9 and 15 months, respectively) compared with ours (28 months).
There is wide variability in the clinical outcome of dif-ferent decompressive procedures in the literature, which makes it difficult to draw definite conclusions (Table 8). Nonetheless, comparisons between the minimally inva-sive laminectomy through tubular retractors and open laminectomy suggest that the former can have clinical out-comes comparable to those for the open procedures, while also having the benefits of minimally invasive surgery.36,46,
54,60–64,66 Moreover, previous studies reporting reopera-tion rates for minimally invasive laminectomy suggest that there is an overall lower reoperation rate associated with this technique compared with that for open laminec-tomy.30,36,39,45,60–63
lumbar Spinal Stenosis and SpondylolisthesisLittle research has been done to compare the outcome
of different decompressive procedures in patients with and without preoperative spondylolisthesis. Clinical re-sults of the current investigation showed no significant difference in outcome for patients with and without pre-operative spondylolisthesis. However, it must be remem-
table 7. reoperation rate
Parameter All Patients Patients w/ Spondylolisthesis Patients w/o Spondylolisthesis p Value
No. of patients* 85 38 38FU duration in mos 0.81 Mean ± SD 28.5 ± 19.63 26.7 ± 18.60 27.7 ± 19.43 Median (min;max) 22.8 (6.2;74.3) 20.7 (8.5;74.3) 20.5 (6.2;74.3)Total reop rate 11 (12.9%) 5 (13.2%) 6 (15.8%) 0.74Isolated decompression of the same (w/ or
w/o different) level(s) 7 (8.2%) 3 (7.8%) 4 (10.5%) 0.55
Fusion w/ or w/o decompression of same (w/ or w/o different) level(s)
3 (3.5%) 2 (5.2%) 1 (2.6%)
Time btwn 1st & 2nd op in mos (min;max) 16.9 (0.2;39.7) 23.1 (6.5;38.1) 10.5 (0.2;39.7) 0.25
* Data were available in the listed number of patients. The type of reoperation procedure performed was unknown in 1 patient.
Fig. 7. Images obtained in a patient with severe LSS at L4–5 treated using minimally invasive laminectomy through tubular retractors. left: Preoperative axial T2-weighted MR image of the lumbar spine at the L4–5 level showing severe stenosis. right: Postoperative MR image at the same level showing marked and effective decompression of the neural elements.
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tabl
e 8.
com
paris
on o
f out
com
e am
ong
diffe
rent
dec
ompr
essiv
e pro
cedu
res,
as re
porte
d in
the l
itera
ture
Authors &
Year
Type of Study
No. of C
ases
FU
Duration
ODI
Improvem
ent
(out of 100)
VAS Ba
ck Pain
Improvem
ent
VAS Leg P
ain
Improvem
ent
Satisfac
tion
Total R
eop
Rate
Reop w/
Fusio
n Rate
Open su
rgery
Wilby e
t al., 2006
Prospective co
hort
100
2 yrs
NA76% of pts
improved
87% of pts
improved
NANA
NA
Wein
stein et al., 2007
Random
ized (& observa-
tional) c
ohort
324
2 yrs
24.2
NANA
NA11%
2.6%
Malm
ivaara e
t al., 2007
Random
ized c
linica
l trial
502 y
rs12.8
NANA
NA6%
NA
Wein
stein et al., 200
8Ra
ndom
ized (& observa-
tional) c
ohort
335
2 yrs
20.5
NANA
NA8%
NA
Yaşar et al., 2009
Prospective ca
se se
ries
125
2 yrs
16NA
NANA
NANA
Wein
stein et al., 200
9Ra
ndom
ized (& observa-
tional) c
ohort
264
4 yrs
23NA
NANA
15%
NA
Wein
stein et al., 2010
Random
ized (& observa-
tional) c
ohort
924 y
rs18.7
NANA
NA13%
NA
Pa
rker et al., 2011
Prospective co
hort
542 y
rs18.1
NA4.1
5 poin
tsNA
NANA
Slätis e
t al., 2011
Random
ized c
linica
l trial
472 y
rs13.4
4.2 p
oints
3.7 po
ints
NA2.1
%NA
Less-invasiv
e open s
urgery (open d
ecom
pressio
n w/ le
ss-exte
nsive
remo
val of pst sta
bilizing elem
ents of spine
)
Thom
é et al., 2005
Random
ized c
ohort
40 (in
each of
2 groups)
1 yr
NARe
sidual
pain: 2.3
points (bilat
lamino
t), 3.6
points (unilat
lamino
t)
NAOv
erall
satisfac
tion:
97% (b
ilat
lamino
t),
74% (unilat
lamino
t)
2.5%
(bilat
lamino
t),
5% (unilat
lamino
t)
NA
Yama
shita et al., 2
006
Prospective ob
serva-
tional
705 y
rsNA
2.5 p
oints
4.5 po
ints
NA4.2%
NA
Ca
vuşoğlu
et al., 2
0071
0Prospective
5022
mos
17.1
4.7 po
ints
4.7 po
ints
NA0%
0%
Ca
vuşoğlu
et al., 2
0079
Prospective random
ized
cohort
50 (in
each of
2 groups)
5.4 yrs
17 (unilat
lamino
t)17 (unilat
lamine
c)
NANA
NA2%
(unilat
lamine
c),
0% (unilat
lamino
t)
0% (unilat
lamine
c),
0% (unilat
lamino
t)
Costa
et al., 2
007
Retrospective
374
5 yrs
NA5 p
oints
NANA
0%0%
Orpen e
t al., 2010
Prospective
100
3.5 y
rs32
5 poin
ts6 p
oints
NANA
4% re
quired,
(2% re
fused)
Ho
ng et al., 2
011
Retrospective c
ohort
24 (unilat
lamino
t),
29 (b
ilat
lamino
t)
4 yrs
12.2 (unilat
lamino
t),
15 (b
ilat
lamino
t)
2.3 p
oints (uni-
lat laminot),
4.1 po
ints
(bilat la
minot)
4.7 po
ints (unilat
lamino
t), 5.1
points (bilat
lamino
t)
NANA
0% (unilat
lamino
t),
3.4%
(bilat
lamino
t)
(con
tinue
d)
minimally invasive laminectomy for lumbar spinal stenosis
J Neurosurg Spine Volume 22 • April 2015 347
tabl
e 8.
com
paris
on o
f out
com
e am
ong
diffe
rent
dec
ompr
essiv
e pro
cedu
res,
as re
porte
d in
the l
itera
ture
(con
tinue
d)
Authors &
Year
Type of Study
No. of C
ases
FU
Duration
ODI
Improvem
ent
(out of 100)
VAS Ba
ck Pain
Improvem
ent
VAS Leg P
ain
Improvem
ent
Satisfac
tion
Total R
eop
Rate
Reop w/
Fusio
n Rate
Other M
I procedures (MS
&/or FE)
Ru
etten
et al., 2
009
Random
ized c
linica
l trial
80 (M
S), 81
(FE)
2 yrs
55 (M
S), 56
(FE)
−1.1 points
(MS), 0.4
points (FE
)
7.2 po
ints (MS),
6.7 po
ints
(FE)
NA6.2%
NA
Ca
stro-Menéndez e
t al., 2009
Prospective
50*
4 yrs
30.2
0.84 po
ints
6.02 p
oints
72% ex
cellent
to good
10%
4%
Ko
mp et al., 2
011
Prospective
72†
2 yrs
540.6
points
6.5 p
oints
NA9.5
%NA
MI tubular re
tracto
r laminecto
my
Palmer et al., 2
0024
2Prospective
173 m
osNA
NANA
NANA
NA
Parikh e
t al., 2008
Prospective & retrospec
-tive
609 m
os29.6
4.53 p
oints
5.43 p
oints
NA3.4%
NA
Pa
o et al., 2009
Prospective
5015 mos
47.6
NANA
NANA
NA
Kim et al., 2012
Retrospective o
bserva
-tional cohort
5742 mos
NANA
NANA
15%
7%
Müslüm
an et al., 2
012
Prospective ob
serva-
tional
8424 mos
161.6
3 poin
tsNA
80% ex
cellent
to good
1.2%
0%
Pa
lmer et al., 2
012
Prospective
5427 mos
NA3 p
oints
6 poin
ts80% ov
erall
satisfac
tion
NA2%
Present case
Retrospective
8428 mos
16 (7
0% of pts
improved)
2.75 p
oints
(67%
of pts
improved)
3.0 p
oints
(74% of pts
improved)
72% ex
cellent
to good
12.9%
3.5%
FE = full e
ndoscopy; la
minec =
laminecto
my; la
minot = laminotomy
; MI = minima
lly invasiv
e; MS = microsurgery; N
A = not applicable; ps
t = posterio
r; pts =
patients.
* All patien
ts underwent m
icroendoscopic
decomp
ression
.† All patien
ts underwent full en
doscopic decomp
ression
.
m. alimi et al.
J Neurosurg Spine Volume 22 • April 2015348
bered that our cohort included only patients with “stable” spondylolisthesis, without movement on flexion/extension films, and with neurogenic claudication in the absence of mechanical back pain. The radiographic results corrobo-rated the clinical outcomes. They showed no significant progression of the slippage after surgery in patients with preoperative spondylolisthesis. Similarly, in patients with-out preoperative spondylolisthesis, no slippage developed after surgery. However, we reemphasize that although we have reported on the radiographic presence and extent of slippage in patients with available follow-up imaging, no direct conclusions have been made based on the ra-diographic results per se given the limited availability of these studies. The radiographic findings have been report-ed to provide a more comprehensive picture of the study group and have been discussed and interpreted with cau-tion. On the contrary, in the current study we have mainly focused on clinical outcome and have used it to provide possible evidence and draw careful conclusions. The clini-cal outcome included pain and functional outcome scores, satisfaction level, as well as the reoperation rate. Palmer et al., who studied the feasibility of minimally invasive lami-nectomy via tubular retractors in 2002, also reported no radiographic progression of the slippage at 3 months’ fol-low-up in 8 patients with preoperative slippage.42,43 Given the small sample size and the short follow-up, conclusions for that study were limited. Findings in the current study are consistent with those of Pao et al. and Müslüman et al., who reported no progression of spondylolisthesis fol-lowing a microsurgical unilateral approach for tubular bi-lateral decompression after 2 years’ follow-up.39,44 The re-operation rates in our study compare favorably with those of Kim et al., who reported a 15% total reoperation rate and 7.1% reoperation rate with fusion following bilateral tubular decompressive surgery via a unilateral approach using tubular retractors.30 Those authors concluded that decompression without fusion is more cost-effective than instrumented fusion for a selected group of patients whom they defined as those with leg-dominant pain and stable Grade I spondylolisthesis.
A small number of studies have looked at the outcome in patients with preoperative spondylolisthesis treated us-ing other minimally invasive decompressive techniques such as the full-endoscopic interlaminar approach. These studies all reported very low reoperation rates and/or min-imal progressive spondylolisthesis postoperatively.
Standard open laminectomy, with or without fusion, is currently the most common procedure to treat LSS. However, conventional open laminectomy in the presence of preexisting spondylolisthesis can be associated with a high rate of subsequent instability requiring delayed fu-sion surgery. Radiographic results in Iguchi et al.’s study demonstrated the development of new spondylolisthesis in 6% of the patients without preoperative slippage at 10 years’ follow-up, and the average progression of slippage was 2.3 mm.26 In Epstein’s study, progression from Grade I to Grade II spondylolisthesis at the 2-year follow-up was seen in 31.4% of cases.13 In a well-designed prospective study on open laminectomy in 58 patents with preopera-tive slippage, Blumenthal et al. found that the reoperation rate with fusion was 37.5% at 3 years’ follow-up.4 Current
surgical guidelines state that the “best medical evidence available in the literature confirms the utility of fusion for improving patient outcomes following decompression for stenosis associated with spondylolisthesis.”51
Despite all the variations in outcome among the dif-ferent decompressive procedures, minimally invasive laminectomy through tubular retractors seems to result in clinical outcome and reoperation rates comparable to those for other decompressive procedures.8–11,25,32,36,40,46,53,54,58,60–66 However, the radiographic results suggest that this tech-nique is associated with a lower instability rate than the full-open procedures, probably because of the preserva-tion of posterior elements of the lumbar spine. Results from a cost-utility study showed that tubular retractor–guided decompression without fusion in this setting is more cost-effective than conventional decompression and fusion (Table 9).30
We divided the patients into early and late groups, and no significant differences in operative time, estimated blood loss, and clinical outcome were observed between the two. In contrast, the CSF leakage rate and reoperation rates were higher in the early group. These differences are probably attributable to the learning curve associated with this technique.
Study limitationsFinally, several limitations of the current study should
be noted. It is a retrospective case series based on a pro-spectively collected database. The most important limita-tion lies in the fact that it was not designed to compare the outcome of different decompressive procedures. Thus, we attempted to compare the results of this study with those in the published literature. The wide variety of outcome mea-sures used in these studies complicated the interpretation. In addition, because a number of between-group analyses may have been underpowered given the available sample size, the lack of observed statistical differences between the groups should be interpreted with caution. The cur-rent study provides preliminary estimates of differences between groups that can be used to power larger studies. The p values for between-group comparisons in the range of 0.06–0.20 should be considered as potential evidence for underpowered evaluations, and readers may wish to consider these differences as suggestive of nonsignificant trends. Another limitation of the study lies in the fact that comparison between preoperative and follow-up imaging was possible in only a small group of patients. For a small number of patients, neither pre- nor postoperative imaging was available in the hospital database; therefore, the pres-ence or absence of spondylolisthesis was not determined in this group. Consequently, the small sample size for the radiographic comparison necessitates interpretation with caution.
conclusionsMinimally invasive laminectomy through retractors
is an effective procedure to treat LSS and shows similar results in patients with and without preoperative spondy-lolisthesis with low reoperation rates. This procedure is associated with a lower postoperative instability rate than
minimally invasive laminectomy for lumbar spinal stenosis
J Neurosurg Spine Volume 22 • April 2015 349
tabl
e 9.
com
paris
on o
f out
com
e am
ong
diffe
rent
type
s of d
ecom
pres
sive p
roce
dure
s in
patie
nts w
ith g
rade
i spo
ndylo
listh
esis
Authors &
Year
Type of Study
No. of P
ts w/
GIS*
FU
Duration
(yrs)
ODI
Improvem
ent
(out of 100)
Points
Improvem
ent
on VAS
Back
Points
Improvem
ent
on VAS
Leg
Satisfac
tion
% Pts w/
Spondylolisthesis
Am
ong A
ll Pts
Posto
perative
Progression
of
Spondylolisthesis
Total R
eop
Rate
Reop w/
Fusio
n Rate
Open laminecto
my
Iguchi et al., 200
0Re
trospective
study
10/15
110
JOA improve-
ment:
55.8%
NANA
NA6%
6% ne
w spon
-dylolisthesis
; average
progression
of
slippage: 2.3
mm
NANA
Ep
stein, 20
04No
t specifi
ed35 pts w
/ GIS, 45
w/o a
ny
spondylo-
listhesis
2 NA
NANA
58% to 63%
excellent
to good
surgeon-
base
d outco
me
43%
31.4%
of pts w
/ GIS pro-
gressed to
GIIS
14.2% in pts
w/ GIS,
6.6%
in pts
w/o a
ny
spondylo-
listhesis
8.5%
in pts
w/ GIS,
4.4%
in pts
w/o a
ny
spondylo-
listhesis
Wein
stein et al.,
2009
Random
ized
(& ob
ser-
vational)
cohort
264
4 23
NANA
NA100%
NA15%
NA
Blum
enthal et al.,
2013
Prospective
study
403.6
15NA
NANA
100%
NA37.5%
NA
MI laminecto
my
Podic
hetty et al.,
2006 (m
icrode-
comp
ression
& microendo-
scopic decom
-pressio
n)
Retro
spective
case se
ries
69/220
0.25
NANA
NANA
31%
NANA
1.4%
Iwats
uki et al.,
2007 (m
i-croscopic
decomp
ression
using
Caspar
retra
ctor)
Not specifi
ed7/4
7 2
NANA
NANA
15%
No pr
ogression
NA0%
MI tubular re
tracto
r laminecto
my
Palmer et al.,
2002
43Re
trospective
case se
ries
8/17
0.25
NANA
NANA
47%
No pr
ogression
NANA
Pa
o et al., 2009
Prospective
study
12/60
1.25
47.6
NANA
NA20%
No pr
ogression
NANA
(con
tinue
d)
m. alimi et al.
J Neurosurg Spine Volume 22 • April 2015350
the conventional open decompressive procedures but has a comparable clinical outcome. Moreover, it has the ben-efits of minimally invasive surgery such as less blood loss and shorter hospital stay. In light of this and other studies demonstrating the potential benefit of tubular and other minimally invasive retractors in decompression surgery, the need for routine fusion surgery in LSS patients with preexisting spondylolisthesis and multilevel LSS should be critically reevaluated.
acknowledgmentsWe acknowledge Dr. Paul Christos for helping in the statistical
analysis of the current study. We also thank AOSpine and Baxter for supporting Marjan Alimi’s fellowship.
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9. co
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utco
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g di
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pes o
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ompr
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s with
gra
de i s
pond
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thes
is (c
ontin
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Authors &
Year
Type of Study
No. of P
ts w/
GIS*
FU
Duration
(yrs)
ODI
Improvem
ent
(out of 100)
Points
Improvem
ent
on VAS
Back
Points
Improvem
ent
on VAS
Leg
Satisfac
tion
% Pts w/
Spondylolisthesis
Am
ong A
ll Pts
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Progression
of
Spondylolisthesis
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eop
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n Rate
MI tubular re
tracto
r laminecto
my (c
ontin
ued)
Müslüm
an et al.,
2012
Prospective
observa-
tional study
25/84
2 16
1.63
NA80% ex
cel-
lent to
good
30%
No pr
ogression
1.2%
0%
Kim et al., 2012
Retro
spective
obser-
vational
cohort
573.5
NANA
NANA
100%
NA15%
7.1%
Present case
Retro
spective
study
51 pts w
/ GIS, 46
w/o a
ny
spondylo-
listhesis
2.4
16 (7
0% of
pts im
-proved)
2.75 (67%
of pts
improved)
3.0 (
74%
of pts
improved)
72% ex
cel-
lent to
good
52%
No pr
ogression
13.2% in pts
w/ GIS,
15.8%
in
pts w/o any
spondylo-
listhesis
5.2%
in pts
w/ GIS,
2.6%
in pts
w/o a
ny
spondylo-
listhesis
GIS = Grade I sp
ondylolisthesis
; JOA
= Ja
panese Orth
opaedic
Association
.* Lis
ted a
lone, per the total num
ber o
f patien
ts in the s
tudy, or a
long w
ith the n
umber o
f patien
ts without any sp
ondylolisthesis
.
minimally invasive laminectomy for lumbar spinal stenosis
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author contributionsConception and design: Härtl, Alimi, Hofstetter, Pyo. Acquisition of data: Alimi, Paulo. Analysis and interpretation of data: Härtl, Alimi, Hofstetter. Drafting the article: Alimi. Critically revising the article: all authors. Reviewed submitted version of manu-script: all authors. Statistical analysis: Alimi, Hofstetter. Study supervision: Härtl.
Supplemental informationPrevious PresentationPortions of this work were presented in abstract/poster form at the 29th Annual Meeting of the AANS/CNS Section on Disorders of the Spine and Peripheral Nerves held in Phoenix, Arizona, on March 6–9, 2013.
correspondenceRoger Härtl, MD, Department of Neurological Surgery, Weill Cornell Brain and Spine Institute, 525 E. 68th St., Box 99, New York, NY 10065. email: [email protected].