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Clinical outcomes following sublaminar decompression and instrumented fusion for lumbar degenerative spinal pathology
Journal of Clinical Neuroscience xxx (2016) xxx–xxx
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Journal of Clinical Neuroscience journal homepage: www.elsevier.com/locate/jocn
Clinical Study
Clinical outcomes following sublaminar decompression and instrumented fusion for lumbar degenerative spinal pathology Kranti Peddada 1, Benjamin D. Elder ⇑,1, Wataru Ishida, Sheng-Fu L. Lo, C. Rory Goodwin, Akwasi O. Boah, Timothy F. Witham Department of Neurosurgery, The Johns Hopkins University School of Medicine, Baltimore, MD 21287, USA
a r t i c l e
i n f o
Article history: Received 28 January 2016 Accepted 7 February 2016 Available online xxxx Keywords: Foraminal stenosis Lateral recess stenosis Lumbar laminectomy Lumbar stenosis Spinal fusion Sublaminar decompression
a b s t r a c t Traditional treatment for lumbar stenosis with instability is laminectomy and posterolateral arthrodesis, with or without interbody fusion. However, laminectomies remove the posterior elements and decrease the available surface area for fusion. Therefore, a sublaminar decompression may be a preferred approach for adequate decompression while preserving bone surface area for fusion. A retrospective review of 71 patients who underwent sublaminar decompression in conjunction with instrumented fusion for degenerative spinal disorders at a single institution was performed. Data collected included demographics, preoperative symptoms, operative data, and radiographical measurements of the central canal, lateral recesses, and neural foramina, and fusion outcomes. Paired t-tests were used to test significance of the outcomes. Thirty-one males and 40 females with a median age 60 years underwent sublaminar decompression and fusion. A median of two levels were fused. The mean Visual Analog Scale pain score improved from 6.7 preoperatively to 2.9 at last follow-up. The fusion rate was 88%, and the median time to fusion was 11 months. Preoperative and postoperative mean thecal sac cross-sectional area, right lateral recess height, left lateral recess height, right foraminal diameter, and left foraminal diameter were 153 and 209 mm2 (p < 0.001), 5.9 and 5.9 mm (p = 0.43), 5.8 and 6.3 mm (p = 0.027), 4.6 and 5.2 mm (p = 0.008), and 4.2 and 5.2 mm (p < 0.001), respectively. Sublaminar decompression provided adequate decompression, with significant increases in thecal sac cross-sectional area and bilateral foraminal diameter. It may be an effective alternative to laminectomy in treating central and foraminal stenosis in conjunction with instrumented fusion. Published by Elsevier Ltd.
1. Introduction Rates of lumbar fusion surgery are rising rapidly in the USA. Between 1992 and 2003 lumbar fusion rates nearly quadrupled, increasing from 0.3 to 1.1 per 1,000 Medicare enrollees. During that same period, Medicare spending for lumbar fusion rose about 500% from US$75 million to $482 million [1]. As the population ages and the prevalence of degenerative spine conditions increases, the need for lumbar fusions in the future will likely be even greater. Lumbar fusion is indicated for, among other pathologies, deformity correction or instability [2]. In the setting of spinal stenosis, decompression is also necessary. The traditional treatment for lumbar stenosis in conjunction with instability is a laminectomy ⇑ Corresponding author. Tel.: +1 410 955 5000. 1
E-mail address: [email protected] (B.D. Elder). These authors have contributed equally to the manuscript.
and stabilization of the spine with posterolateral arthrodesis and possible interbody fusion. Laminectomies are the most common surgical treatment for stenosis. The procedure involves removal of the entire lamina, spinous process, ligamentum flavum, interspinous ligament, and variable amounts of the facet joints. Although adequate decompression is achieved with a traditional laminectomy, the only remaining bone surfaces for fusion are the transverse processes and any remaining facet joint, depending on the extent of facetectomy performed. As such, pseudoarthrosis rates up to 27–30% have been reported for posterolateral fusion in conjunction with laminectomy [3,4]. Our group recently described a novel decompression technique that preserves the lamina, enabling fusion to occur both posterolaterally as well as dorsally along the lamina (Clinical Spine Surgery, 2016, Under review (unpublished results)). The procedure is an adaptation of the Smith-Petersen osteotomy, which is traditionally performed to correct deformities, but is less commonly used in stabilization procedures for degenerative disorders. The objective of
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Please cite this article in press as: Peddada K et al. Clinical outcomes following sublaminar decompression and instrumented fusion for lumbar degenerative spinal pathology. J Clin Neurosci (2016), http://dx.doi.org/10.1016/j.jocn.2016.02.001
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this manuscript was to evaluate the outcomes of this novel technique for the adequacy of the decompression and fusion outcomes.
readmissions were counted if they occurred within 30 days of the index surgery.
2. Methods
2.3. Status at last follow-up
A retrospective review of the senior author’s patients at a single institution between 2009 and 2014 was performed under an Institutional Review Board approved protocol (NA_00038491). Patients included in this study underwent sublaminar decompression in conjunction with pedicle screw stabilization and fusion of at least one level for degenerative lumbar pathology, for stenosis in combination with instability. Instrumented stabilization was required due to instability in the opinion of the senior author, based on symptoms of mechanical back pain with or without instability on preoperative flexion–extension radiographs. Clinical and imaging data were reviewed. Although the details of the sublaminar decompression are described in detail elsewhere (Clinical Spine Surgery, 2016, Under review (unpublished results)), a brief review is included here for clarity. The interspinous ligament is removed with a Leksell rongeur (Elekta AB, Stockholm, Sweden), and a curved osteotome is directed cranial to caudal to remove the posterior surface of the facet joints. A straight osteotome is then used to create partial ‘‘chevron” osteotomies over the inferior articulating processes bilaterally. A laminar spreader is used to distract the interspace, and the epidural space is accessed in the midline through the ligamentum flavum. The ligamentum flavum is then removed with rongeurs and Kerrison punches, and the remaining inferior articulating process is removed to complete the decompression and osteotomy bilaterally. The superior aspect of the inferior laminar is then removed with any remaining ligamentum flavum.
Neurological symptoms recorded at last follow-up included bowel/bladder dysfunction, radiculopathy, neurogenic claudication, sensory abnormality, motor weakness, and VAS pain score. Additionally, the number of patients requiring adjacent level surgery during the follow-up time period was determined.
2.1. Demographics and baseline characteristics Demographical data collected included age, sex, body mass index and smoking history. Baseline characteristics consisted of presence/absence of co-morbidities and neurological symptoms. Co-morbidities included diabetes, hypertension, depression, osteoporosis/osteopenia, and osteoarthritis. Neurological symptoms included radiculopathy, neurogenic claudication, motor weakness, bowel/bladder dysfunction, sensory abnormality, and preoperative Visual Analog Scale (VAS) pain score overall for back and leg pain. 2.2. Operative data and characteristics Preoperative diagnoses of spinal conditions and operative details were recorded. Operative details reviewed were spinal levels involved in decompression, discectomy, foraminotomy, and spondylolisthesis reduction; interbody fusion levels through a posterior, transforaminal, or direct lateral approach; and number of instrumented fusion levels in posterior lateral arthrodesis. Fusion constructs used in posterolateral arthrodesis were documented and included one or more of the following: local autograft, iliac crest autograft, iliac crest bone marrow aspirate, demineralized bone matrix (Optium Demineralized Bone Matrix Putty; LifeNet Health, Virginia Beach, VA, USA), Vitoss Bone Graft Substitute (Stryker, Kalamazoo, MI, USA), bone morphogenetic protein-2, calcium phosphate crystals, and cancellous and/or corticocancellous allograft bone. Perioperative measures documented were operative time, estimated blood loss, length of hospital stay, and need for inpatient rehabilitation. Intraoperative complications recorded included incidental durotomy, and postoperative complications included postoperative neurological deficits, deep venous thrombosis, pulmonary embolism, and wound infection. The readmission rate was also recorded. Postoperative complications and
2.4. Imaging data Imaging data from T2-weighted MRI and three-dimensional reconstructions of CT scans was reviewed. Measurements were made from these images according to the methodology described previously by Steurer et al. [5] Assessments included the anterior–posterior (AP) diameter of the thecal sac (mm), lateral diameter of the thecal sac (mm), thecal sac cross-sectional area (mm2), bilateral lateral recess height (mm), and bilateral foraminal diameter (mm). Measurements were made at a lumbar level that was included in the sublaminar decompression. AP and lateral thecal sac diameters, thecal sac cross-sectional area, and lateral recess heights were measured at the plane with the greatest central stenosis. The foraminal diameter was measured at the plane in the foraminal space with the greatest foraminal stenosis. As the study was retrospective, preoperative and postoperative imaging was not available for all patients. Both preoperative and postoperative T2-weighted MRI and/or CT scans were available for a total of 31 patients. If a single patient had more than one of these combinations, priority was given to both pre- and postoperative MRI and then both pre- and postoperative CT scan. A total of 16 patients had a preoperative MRI and postoperative CT scan, eight patients had pre- and postoperative CT scan, and seven patients had pre- and postoperative MRI. Fusion was assessed radiographically using static radiographs to assess for bridging bone. If there was concern for pseudoarthrosis, CT scans and/or flexion-extension radiographs were obtained. Only those patients who had a sufficient length of follow-up to have documented fusion and those who were diagnosed with pseudoarthrosis were included. Patients who were lost to followup prior to fusion assessment at 12 months were excluded. Median time to fusion and fusion rate were calculated. 2.5. Statistical analysis Continuous data were calculated as median (range) or mean and categorical data as frequency (percentage). Statistical tests were used to determine significance of changes in outcome variables preoperatively and at last follow-up. McNemar’s test was used to evaluate changes in prevalence of neurologic symptoms and a paired two-sample t-test was used to assess for change in VAS pain score. A paired two-sample t-test was used to test changes in radiographical measurements of stenosis when the sample size was greater than or equal to 30, and a Wilcoxon signed-rank test was used otherwise. p < 0.05 was considered significant. 3. Results 3.1. Demographics and baseline characteristics A total of 71 patients who underwent sublaminar decompression and fusion were included in this study. All cases involved degenerative pathology, and some patients had concurrent spinal
Please cite this article in press as: Peddada K et al. Clinical outcomes following sublaminar decompression and instrumented fusion for lumbar degenerative spinal pathology. J Clin Neurosci (2016), http://dx.doi.org/10.1016/j.jocn.2016.02.001
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K. Peddada et al. / Journal of Clinical Neuroscience xxx (2016) xxx–xxx Table 1 Baseline demographics of patients undergoing sublaminar decompression and instrumented fusion for lumbar degenerative spinal pathology Patient characteristics Age, years, median (range) Sex, female, n (%) BMI, kg/m2, median (range) Smoking history, n (%)
Sublaminar decompression Number of levels decompressed, median (range) Fusion procedures, n (%) Interbody fusion PLIF TLIF Direct lateral interbody fusion Number of levels with interbody fusion, median (range) Structural allograft in interbody fusion Posterior lateral arthrodesis
60 (19–78) 40 (56) 28.4 (19.7–39.2) 23 (32)
Co-morbidities, n (%) Diabetes Hypertension Depression Osteoporosis/osteopenia Osteoarthritis Prior lumbar surgery
15 (21) 39 (55) 19 (27) 8 (11) 16 (23) 14 (20)
Preoperative diagnosis, n (%) Degenerative disc disease Disc herniation Synovial cysts Spondylolisthesis Spinal deformity
42 (59) 21 (30) 2 (3) 43 (61) 9 (13)
Symptoms at presentation, n (%) Radiculopathy Neurogenic claudication Weakness Bowel/bladder dysfunction Sensory abnormality VAS pain score, mean (range)
Table 2 Operative characteristics of patients undergoing sublaminar decompression and instrumented fusion for lumbar degenerative spinal pathology
Bone grafts used in posterior lateral arthrodesis Local autograft Iliac crest autograft Allograft DBM Optium DBM Puttya Vitoss bone graft substituteb BMP-2 Calcium phosphate crystals Number of levels with posterior lateral arthrodesis, median (range) Additional procedures performed Discectomy, n (%) Number of levels with discectomy, median (range) Spondylolisthesis reduction, n (%) Number of spondylolisthesis reduction levels, median (range)
64 (90) 17 (24) 27 (38) 12 (17) 46 (65) 6.9 (0–10)
BMI = body mass index, VAS = Visual Analog Scale.
1 (1–4) 60 (85) 24 (40) 40 (67) 1 (2) 1 (1–2) 60 (100) 71 (100) 68 (96) 30 (42) 6 (8) 4 (6) 43 (61) 19 (27) 15 (21) 16 (23) 2 (1–6)
63 (89) 1 (1–3) 32 (45) 1 (1–2)
a
LifeNet Health, Virginia Beach, VA, USA. Stryker, Kalamazoo, MI, USA. BMP = bone morphogenetic protein, DBM = demineralized bone matrix, PLIF = posterior lateral interbody fusion, TLIF = transforaminal lateral interbody fusion. b
deformity, but the goal of the primary operation was not deformity correction. The majority were female (n = 40, 56%), and the median age and body mass index at time of surgery was 60 years (range 19–78 years) and 28.4 kg/m2 (range 19.7–39.2 kg/m2), respectively (Table 1). Twenty-three (32%) patients had a smoking history, eight (11%) had osteoporosis/osteopenia, 16 (23%) had osteoarthritis, and 14 (20%) had a prior lumbar surgery. In addition to lumbar stenosis with a concern for instability, patients had the following spinal pathologies: degenerative disc disease (n = 42, 59%), disc herniation (n = 21, 30%), synovial cysts (n = 2, 3%), spondylolisthesis (n = 43, 61%), and spinal deformity (n = 9, 13%) (Table 1). The major presenting symptoms prior to surgery were radiculopathy (n = 64, 90%) and sensory abnormalities (n = 46, 65%). Other symptoms included lower extremity weakness (n = 27, 38%), neurogenic claudication (n = 17, 24%), and bowel/bladder dysfunction (n = 12, 17%). The mean preoperative VAS pain score combined for the lower back and/or legs was 6.7 (range 0–10). 3.2. Operative characteristics The median number of lumbar levels decompressed was one (range one to four) and dorsal fusion along the lamina was performed in all patients at the same levels that were decompressed (Table 2). All patients additionally underwent posterolateral fixation and fusion with pedicle screw instrumentation. The median number of posterior levels fused was two (range one to six). Bone grafts most commonly used in posterior fusions were local autograft (n = 68, 96%), Optium DBM Putty (n = 43, 61%), and iliac crest autograft (n = 30, 42%). In addition to posterior fusion, the majority of patients underwent interbody fusion (n = 60, 85%). Most interbody fusions were performed through either a transforaminal (n = 40, 67%) or posterior (n = 24, 40%) approach, with some patients having a combination of both procedures. The median number of interbody levels fused was one (range one to two), and all interbody fusions utilized a structural allograft. Other procedures performed were discectomy (n = 63, 89%) and spondylolisthesis reduction (n = 32, 45%). The median number of lumbar levels in which a discectomy or spondylolisthesis reduction were
performed were one (range one to three) and one (range one to two), respectively. 3.3. Perioperative data and outcomes The median operative time and estimated blood loss were 322 minutes (range 200–492 minutes) and 600 mL (range 15– 2250 mL), respectively (Table 3). Seven (10%) patients had intraoperative complications, with durotomy (n = 5, 7%) being the most common complication. The median length of hospitalization was five days (range 2–11 days) and the readmission rate was 6% (n = 4). Inpatient rehabilitation was required for eight (11%) patients (Table 4). The median length of follow-up was 12 months (range 1– 60 months). At last follow-up, the mean VAS pain score was 2.9 (range 0–10) and two (3%) patients eventually required adjacent level surgery. Three patients (4%) had a postoperative neurological deficit at final follow-up. One patient had a mild foot drop starting 1 month postoperatively. Another patient had a foot drop and L5 radicular pain following hardware failure of the lower instrumented level with osteopenia 2 weeks postoperatively. The third patient had persistent L4 and L5 distribution dysesthesias postoperatively. With regard to other complications, one patient developed a pulmonary embolism, two patients had a postoperative ileus, one patient had a seroma requiring drainage, one patient had a myocardial infarction, one patient had mild rhabdomyolysis, and one patient had urethral trauma from foley catheter insertion. 3.4. Comparison of preoperative and postoperative symptoms The prevalence of all symptoms, except weakness, showed statistically significant reductions postoperatively (Table 5). The largest relative percent change from before surgery was seen for neurogenic claudication (92%, p = 0.00005). Radiculopathy,
Please cite this article in press as: Peddada K et al. Clinical outcomes following sublaminar decompression and instrumented fusion for lumbar degenerative spinal pathology. J Clin Neurosci (2016), http://dx.doi.org/10.1016/j.jocn.2016.02.001
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Table 3 Perioperative data of patients undergoing sublaminar decompression and instrumented fusion for lumbar degenerative spinal pathology Perioperative variables OR time, minutes, median (range) EBL, ml, median (range) Intraoperative complications, n (%) Durotomy Postoperative complications, n (%) Postoperative neurological deficit at final follow-up DVT PE Wound infection Inpatient rehabilitation required, n (%) Length of hospitalization, days, median (range) Readmission within 30 days, n (%)
322 (200–492) 600 (15–2250) 7 (10) 5 (7) 3 0 1 0 8 5 4
(4) (0) (1) (0) (11) (2–11) (6)
DVT = deep vein thrombosis, EBL = estimated blood loss, OR = operating room, PE = pulmonary embolism.
Table 4 Clinical outcomes of patients undergoing sublaminar decompression and instrumented fusion for lumbar degenerative spinal pathology Outcome variable Length of follow-up, months, median (range) Successful fusion, n (%) Time to fusion, months, median (range) Incidence of new symptoms at last follow-up, n (%) Radiculopathy Sensory abnormality Bowel/bladder dysfunction Neurogenic claudication Weakness VAS pain score, mean (range) Adjacent level surgery needed, n (%)
12 (1–60) 37 (88) 11 (3–17) 0 (0) 2 (3) 0 (0) 0 (0) 7 (10) 2.9 (0–10) 2 (3)
VAS = Visual Analog Scale.
bowel/bladder dysfunction, sensory abnormality, and weakness showed relative percent changes from before surgery of 87% (p < 0.00001), 82% (p = 0.0039), 69% (p < 0.00001), and 34% (p = 0.19), respectively. The relative reduction in mean VAS pain score was 57% from before surgery (6.7) to last follow-up (2.9) and was statistically significant (p < 0.00001).
Fig. 1. Representative T2-weighted MRI before and after the sublaminar decompression. (a) Preoperative sagittal and (b) axial images demonstrating central and lateral recess stenosis from ligamentum hypertrophy, facet hypertrophy, and disc protrusion. (c) Postoperative sagittal and (d) axial images demonstrating treatment of central and lateral recess stenosis following sublaminar decompression with resection of ligamentum flavum and facet osteotomies (performed in conjunction with discectomy and transforaminal interbody cage placement), with remaining laminar bone.
available for fusion assessment: 37 (88%) patients achieved successful fusion with a median time to fusion of 11 (range 3–17) months (Table 4).
3.5. Radiographical measurements 4. Discussion Representative MRI and CT images demonstrating the results of the sublaminar decompression are presented in Fig. 1, 2, respectively. Radiographical measurements of central and foraminal stenosis, but not lateral recess stenosis, showed statistically significant increases following sublaminar decompression (Table 6). Mean AP thecal sac diameter, lateral thecal sac diameter, and thecal sac cross-sectional area increased by 25% (p = 0.00013), 8% (p = 0.0052), and 37% (p = 0.000012), respectively, and mean right and left foraminal diameter increased 13% (p = 0.0084) and 24% (p = 0.00012), respectively. Imaging data for 42 patients was
The clinical outcomes of a novel sublaminar decompression technique for the treatment of lumbar stenosis in conjunction with instability are presented. These results suggest that sublaminar decompression may be a favorable alternative to laminectomy because sufficient decompression can be achieved with high fusion success. Adequate decompression was achieved clinically, as evidenced by a statistically significant reduction in the VAS pain score and rates of radiculopathy, bowel/bladder dysfunction, neurogenic
Table 5 Comparison of symptoms preoperatively and postoperatively after sublaminar decompression and instrumented fusion for lumbar degenerative spinal pathology Symptoms Radiculopathy, n (%) Neurogenic claudication, n (%) Sensory abnormality, n (%) Bowel/bladder dysfunction, n (%) Weakness, n (%) VAS pain score, mean
Preoperative
Last follow-up
Relative percent change
p value
64 (90) 17 (24) 46 (65) 12 (17) 27 (38) 6.7
8 (12) 1 (2) 13 (20) 2 (3) 16 (25) 2.9
87 92 69 82 34 57
<0.00001 0.00005 <0.00001 0.0039 0.19 <0.00001
Bold type indicates statistical significance. VAS = Visual Analog Scale.
Please cite this article in press as: Peddada K et al. Clinical outcomes following sublaminar decompression and instrumented fusion for lumbar degenerative spinal pathology. J Clin Neurosci (2016), http://dx.doi.org/10.1016/j.jocn.2016.02.001
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Fig. 2. Representative CT images before and after sublaminar decompression. (a) Preoperative sagittal CT scan demonstrating central stenosis at L3–L4 from grade 1 spondylolisthesis and calcified ligamentum flavum, and central stenosis at L5–S1 from ligamentum hypertrophy and calcified disc protrusion. (b) Preoperative axial CT image at L3–L4 demonstrating central and lateral recess stenosis and (c) axial CT image at L5–S1 demonstrating central, lateral recess, and foraminal stenosis. (d) Postoperative sagittal CT image demonstrating decompression of central canal at L3–L4 and L5–S1 (with transforaminal interbody graft only at L3–L4). (e) Axial CT image at L3–L4 following sublaminar decompression with resolution of central and lateral recess stenosis, with preservation of dorsal bone with dorsal bone graft placement (in conjunction with discectomy for interbody graft placement). (f) Axial CT image at L5–S1 following sublaminar decompression showing decompression of central and lateral recess stenosis, while calcified disc protrusion remains.
Table 6 Analysis of radiographical changes after sublaminar decompression and instrumented fusion for lumbar degenerative spinal pathology Radiographical measurements
Preoperative
Last follow-up
Percent change
p value
10.4 17.2 153
13.0 18.6 209
25 8 37
0.00013 0.0052 0.000012
Lateral recess stenosis measurements Right lateral recess height, mm, mean Left lateral recess height, mm, mean
5.9 5.8
5.9 6.3
0 9
0.43 0.027
Foraminal stenosis measurements Right foraminal diameter, mm, mean Left foraminal diameter, mm, mean
4.6 4.2
5.2 5.2
13 24
0.0084 0.00012
Central stenosis measurements AP thecal sac diameter, mm, mean Lateral thecal sac diameter, mm, mean Thecal sac cross-sectional area, mm2, mean
Bold type indicates statistical significance. AP = anteroposterior.
claudication, and sensory abnormality at last follow-up. Decompression was also achieved radiographically in the central spinal canal and neural foramina, with an 88% fusion rate. The pseudoarthrosis rate of 12% is lower than some previously reported rates of pseudoarthrosis following laminectomy, which can be as high as 27–30% [3,4]. Although Nayak and Sannegowda recently showed a pseudoarthrosis rate of 5.4% following laminectomy [6], fewer lumbar levels per patient were fused in their study and the types and extent of degenerative spinal pathology in their patient population were different to those seen in this study.
A number of decompressive procedures that preserve the posterior spinal elements and provide greater bone surface area than a laminectomy for fusion have been described. However, this sublaminar decompression offers advantages that can result in better fusion outcomes and may more effectively treat lumbar stenosis compared to these other procedures. One such procedure is a unilateral/bilateral laminotomy, which involves removal of the lower and upper part of the superior and inferior vertebral arch, respectively, while leaving the interspinous and supraspinous ligaments intact [7]. Although the extent of decompression a laminotomy
Please cite this article in press as: Peddada K et al. Clinical outcomes following sublaminar decompression and instrumented fusion for lumbar degenerative spinal pathology. J Clin Neurosci (2016), http://dx.doi.org/10.1016/j.jocn.2016.02.001
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can achieve is comparable to a laminectomy, a key advantage of sublaminar decompression is the ability to fuse dorsally along the intact lamina in addition to posterolaterally and in the interbody space, leading to potentially higher rates of fusion [8,9]. Dorsal fusion following a laminotomy can be challenging depending on the extent of bone that is removed. Furthermore, compared to sublaminar decompression, a lamintotomy provides less access to the lateral recess and neural foramen, potentially limiting decompression in these regions [10]. The microsurgical bilateral decompression via a unilateral approach is a minimally invasive adaptation of a laminotomy that is beneficial because it reduces damage to the paraspinal musculature [11]. However, unlike sublaminar decompression, the utility of this approach generally is limited to treatment of central stenosis, specifically when the spinal canal is round or oval shaped and not trefoil-shaped [12]. The wide fenestration technique described by Nakai et al. [13] and the chimney sublaminar decompression by Lin et al. [14] also primarily address central stenosis. Alternatively, Nemani et al. [10] described the use of the stand-alone direct lateral lumbar interbody approach for lumbar stenosis with instability. This minimally invasive procedure avoids traditional anterior or posterior decompression methods by indirectly achieving decompression during fusion. However, it may only adequately address foraminal stenosis and the study showed about 10% of patients ultimately required a separate posterior decompression [10]. Interspinous dynamic stabilization has also been proposed as an alternative to decompression and fusion in treating lumbar stenosis with instability. In this technique, devices are inserted into the interspinous process to restrict movement of spinal segments in directions that cause instability or pain and increase the dimensions of and limit dynamic compression of the spinal canal, thereby emulating the functions of spinal fusion and decompression, respectively, through a less invasive procedure [15,16]. Despite this theoretical advantage, comparative studies with decompression and fusion have failed to demonstrate superior improvements from this technique in functional status and pain severity [15,17]. Furthermore, complication and revision surgery rates around 30% have been reported, suggesting decompression and fusion are currently still safer and more effective than interspinous dynamic stabilization [17,18]. Interestingly, in this study, sublaminar decompression did not substantially change the lateral recess dimensions or lead to improvement in strength postoperatively. As discussed in the prior technical manuscript (Clinical Spine Surgery, 2016, Under review (unpublished results)), sublaminar decompression allows sufficient access to and enables decompression of the lateral recess. However, a potential reason for the discrepancy is that following decompression, the osteotomy is closed to increase lordosis, and this may eliminate some of the lateral recess decompression. Therefore, we have found that there is a balance between aggressively closing the osteotomy and bone removal for decompression. Additionally, there may not have been enough patients with available imaging in this study with severe lateral recess stenosis to demonstrate a significant improvement. Another notable finding was that all neurologic symptoms improved by last follow-up except for weakness. One potential reason could be that the preoperative weakness was more longstanding and thus there was not a substantial improvement even following adequate decompression. The study has several important limitations. First, the retrospective study design has inherent limitations. Additionally, there was a lack of a control group of patients undergoing laminectomy and/or other decompressive procedures in conjunction with instrumented fusion, which limits any ability to conclusively determine if sublaminar decompression is superior or inferior to other forms of decompression and fusion. Furthermore, the use
of different imaging modalities and the limited number of patients with available preoperative and postoperative imaging (T2weighted MRI and CT scans) when evaluating stenosis radiographically may introduce heterogeneity in the results. Finally, static radiographs were used to assess fusion status, while the ideal assessment would have involved assessment of both bridging bone as well as motion criteria. However, most of these limitations were consequences of the retrospective nature of this study. In the future, it would be ideal to conduct a prospective randomized trial to directly compare the clinical and radiographical outcomes between laminectomy and posterolateral fusion sublaminar decompression and posterolateral fusion to conclusively determine the better procedure. Additional future studies will examine the improvement in alignment that can be achieved with this technique because of the osteotomy and whether or not this improved alignment affects outcomes.
5. Conclusions To our knowledge, this is the first study to evaluate sublaminar decompression with fusion as a treatment for lumbar stenosis and instability in degenerative pathology of the lumbar spine. It was demonstrated that sublaminar decompression can achieve adequate decompression, particularly in the central spinal canal and neural foramen, with substantial improvements in neurological symptoms. Furthermore, the fusion rate was high and compares favorably to fusion rates following a laminectomy. Hence, sublaminar decompression may be an effective alternative to laminectomy and other decompressive procedures in the treatment of lumbar stenosis with instability.
Conflicts of Interest/Disclosures The authors declare that they have no financial or other conflicts of interest in relation to this research and its publication. Acknowledgements The Gordon and Marilyn Macklin Foundation supported this study. References [1] Weinstein JN, Lurie JD, Olson PR, et al. United States’ trends and regional variations in lumbar spine surgery: 1992–2003. Spine (Phila Pa 1976) 2006;31:2707–14. [2] Omidi-Kashani F, Hasankhani EG, Ashjazadeh A. Lumbar spinal stenosis: who should be fused? An updated review. Asian Spine J 2014;8:521–30. [3] Aebi M. The adult scoliosis. Eur Spine J 2005;14:925–48. [4] Lee CK. Lumbar spinal instability (olisthesis) after extensive posterior spinal decompression. Spine (Phila Pa 1976) 1983;8:429–33. [5] Steurer J, Roner S, Gnannt R, et al. Quantitative radiologic criteria for the diagnosis of lumbar spinal stenosis: a systematic literature review. BMC Musculoskelet Disord 2011;12:175. [6] Nayak MT, Sannegowda RB. Clinical and radiological outcome in cases of posterolateral fusion with instrumentation for lumbar spondylolisthesis. J Clin Diagn Res 2015;9:PC17–21. [7] Overdevest G, Vleggeert-Lankamp C, Jacobs W, et al. Effectiveness of posterior decompression techniques compared with conventional laminectomy for lumbar stenosis. Eur Spine J 2015;24:2244–63. [8] Guiot BH, Khoo LT, Fessler RG. A minimally invasive technique for decompression of the lumbar spine. Spine (Phila Pa 1976) 2002;27:432–8. [9] Spetzger U, Bertalanffy H, Naujokat C, et al. Unilateral laminotomy for bilateral decompression of lumbar spinal stenosis. Part I: anatomical and surgical considerations. Acta Neurochir (Wien) 1997;139:392–6. [10] Nemani VM, Aichmair A, Taher F, et al. Rate of revision surgery after standalone lateral lumbar interbody fusion for lumbar spinal stenosis. Spine (Phila Pa 1976) 2014;39:326–31. [11] Weiner BK, Walker M, Brower RS, et al. Microdecompression for lumbar spinal canal stenosis. Spine (Phila Pa 1976) 1999;24:2268–72.
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K. Peddada et al. / Journal of Clinical Neuroscience xxx (2016) xxx–xxx [12] Choi WS, Oh CH, Ji GY, et al. Spinal canal morphology and clinical outcomes of microsurgical bilateral decompression via a unilateral approach for lumbar spinal canal stenosis. Eur Spine J 2014;23:991–8. [13] Nakai O, Ookawa A, Yamaura I. Long-term roentgenographic and functional changes in patients who were treated with wide fenestration for central lumbar stenosis. J Bone Joint Surg Am 1991;73:1184–91. [14] Lin SM, Tseng SH, Yang JC, et al. Chimney sublaminar decompression for degenerative lumbar spinal stenosis. J Neurosurg Spine 2006;4:359–64. [15] Kong DS, Kim ES, Eoh W. One-year outcome evaluation after interspinous implantation for degenerative spinal stenosis with segmental instability. J Korean Med Sci 2007;22:330–5.
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[16] Lee SH, Seol A, Cho TY, et al. A systematic review of interspinous dynamic stabilization. Clin Orthop Surg 2015;7:323–9. [17] Kim KA, McDonald M, Pik JH, et al. Dynamic intraspinous spacer technology for posterior stabilization: case-control study on the safety, sagittal angulation, and pain outcome at 1-year follow-up evaluation. Neurosurg Focus 2007;22: E7. [18] Tuschel A, Chavanne A, Eder C, et al. Implant survival analysis and failure modes of the X-Stop interspinous distraction device. Spine (Phila Pa 1976) 2013;38:1826–31.
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Clinical Study
Clinical outcomes following sublaminar decompression and instrumented fusion for lumbar degenerative spinal pathology Kranti Peddada 1, Benjamin D. Elder ⇑,1, Wataru Ishida, Sheng-Fu L. Lo, C. Rory Goodwin, Akwasi O. Boah, Timothy F. Witham Department of Neurosurgery, The Johns Hopkins University School of Medicine, Baltimore, MD 21287, USA
a r t i c l e
i n f o
Article history: Received 28 January 2016 Accepted 7 February 2016 Available online xxxx Keywords: Foraminal stenosis Lateral recess stenosis Lumbar laminectomy Lumbar stenosis Spinal fusion Sublaminar decompression
a b s t r a c t Traditional treatment for lumbar stenosis with instability is laminectomy and posterolateral arthrodesis, with or without interbody fusion. However, laminectomies remove the posterior elements and decrease the available surface area for fusion. Therefore, a sublaminar decompression may be a preferred approach for adequate decompression while preserving bone surface area for fusion. A retrospective review of 71 patients who underwent sublaminar decompression in conjunction with instrumented fusion for degenerative spinal disorders at a single institution was performed. Data collected included demographics, preoperative symptoms, operative data, and radiographical measurements of the central canal, lateral recesses, and neural foramina, and fusion outcomes. Paired t-tests were used to test significance of the outcomes. Thirty-one males and 40 females with a median age 60 years underwent sublaminar decompression and fusion. A median of two levels were fused. The mean Visual Analog Scale pain score improved from 6.7 preoperatively to 2.9 at last follow-up. The fusion rate was 88%, and the median time to fusion was 11 months. Preoperative and postoperative mean thecal sac cross-sectional area, right lateral recess height, left lateral recess height, right foraminal diameter, and left foraminal diameter were 153 and 209 mm2 (p < 0.001), 5.9 and 5.9 mm (p = 0.43), 5.8 and 6.3 mm (p = 0.027), 4.6 and 5.2 mm (p = 0.008), and 4.2 and 5.2 mm (p < 0.001), respectively. Sublaminar decompression provided adequate decompression, with significant increases in thecal sac cross-sectional area and bilateral foraminal diameter. It may be an effective alternative to laminectomy in treating central and foraminal stenosis in conjunction with instrumented fusion. Published by Elsevier Ltd.
1. Introduction Rates of lumbar fusion surgery are rising rapidly in the USA. Between 1992 and 2003 lumbar fusion rates nearly quadrupled, increasing from 0.3 to 1.1 per 1,000 Medicare enrollees. During that same period, Medicare spending for lumbar fusion rose about 500% from US$75 million to $482 million [1]. As the population ages and the prevalence of degenerative spine conditions increases, the need for lumbar fusions in the future will likely be even greater. Lumbar fusion is indicated for, among other pathologies, deformity correction or instability [2]. In the setting of spinal stenosis, decompression is also necessary. The traditional treatment for lumbar stenosis in conjunction with instability is a laminectomy ⇑ Corresponding author. Tel.: +1 410 955 5000. 1
E-mail address: [email protected] (B.D. Elder). These authors have contributed equally to the manuscript.
and stabilization of the spine with posterolateral arthrodesis and possible interbody fusion. Laminectomies are the most common surgical treatment for stenosis. The procedure involves removal of the entire lamina, spinous process, ligamentum flavum, interspinous ligament, and variable amounts of the facet joints. Although adequate decompression is achieved with a traditional laminectomy, the only remaining bone surfaces for fusion are the transverse processes and any remaining facet joint, depending on the extent of facetectomy performed. As such, pseudoarthrosis rates up to 27–30% have been reported for posterolateral fusion in conjunction with laminectomy [3,4]. Our group recently described a novel decompression technique that preserves the lamina, enabling fusion to occur both posterolaterally as well as dorsally along the lamina (Clinical Spine Surgery, 2016, Under review (unpublished results)). The procedure is an adaptation of the Smith-Petersen osteotomy, which is traditionally performed to correct deformities, but is less commonly used in stabilization procedures for degenerative disorders. The objective of
http://dx.doi.org/10.1016/j.jocn.2016.02.001 0967-5868/Published by Elsevier Ltd.
Please cite this article in press as: Peddada K et al. Clinical outcomes following sublaminar decompression and instrumented fusion for lumbar degenerative spinal pathology. J Clin Neurosci (2016), http://dx.doi.org/10.1016/j.jocn.2016.02.001
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this manuscript was to evaluate the outcomes of this novel technique for the adequacy of the decompression and fusion outcomes.
readmissions were counted if they occurred within 30 days of the index surgery.
2. Methods
2.3. Status at last follow-up
A retrospective review of the senior author’s patients at a single institution between 2009 and 2014 was performed under an Institutional Review Board approved protocol (NA_00038491). Patients included in this study underwent sublaminar decompression in conjunction with pedicle screw stabilization and fusion of at least one level for degenerative lumbar pathology, for stenosis in combination with instability. Instrumented stabilization was required due to instability in the opinion of the senior author, based on symptoms of mechanical back pain with or without instability on preoperative flexion–extension radiographs. Clinical and imaging data were reviewed. Although the details of the sublaminar decompression are described in detail elsewhere (Clinical Spine Surgery, 2016, Under review (unpublished results)), a brief review is included here for clarity. The interspinous ligament is removed with a Leksell rongeur (Elekta AB, Stockholm, Sweden), and a curved osteotome is directed cranial to caudal to remove the posterior surface of the facet joints. A straight osteotome is then used to create partial ‘‘chevron” osteotomies over the inferior articulating processes bilaterally. A laminar spreader is used to distract the interspace, and the epidural space is accessed in the midline through the ligamentum flavum. The ligamentum flavum is then removed with rongeurs and Kerrison punches, and the remaining inferior articulating process is removed to complete the decompression and osteotomy bilaterally. The superior aspect of the inferior laminar is then removed with any remaining ligamentum flavum.
Neurological symptoms recorded at last follow-up included bowel/bladder dysfunction, radiculopathy, neurogenic claudication, sensory abnormality, motor weakness, and VAS pain score. Additionally, the number of patients requiring adjacent level surgery during the follow-up time period was determined.
2.1. Demographics and baseline characteristics Demographical data collected included age, sex, body mass index and smoking history. Baseline characteristics consisted of presence/absence of co-morbidities and neurological symptoms. Co-morbidities included diabetes, hypertension, depression, osteoporosis/osteopenia, and osteoarthritis. Neurological symptoms included radiculopathy, neurogenic claudication, motor weakness, bowel/bladder dysfunction, sensory abnormality, and preoperative Visual Analog Scale (VAS) pain score overall for back and leg pain. 2.2. Operative data and characteristics Preoperative diagnoses of spinal conditions and operative details were recorded. Operative details reviewed were spinal levels involved in decompression, discectomy, foraminotomy, and spondylolisthesis reduction; interbody fusion levels through a posterior, transforaminal, or direct lateral approach; and number of instrumented fusion levels in posterior lateral arthrodesis. Fusion constructs used in posterolateral arthrodesis were documented and included one or more of the following: local autograft, iliac crest autograft, iliac crest bone marrow aspirate, demineralized bone matrix (Optium Demineralized Bone Matrix Putty; LifeNet Health, Virginia Beach, VA, USA), Vitoss Bone Graft Substitute (Stryker, Kalamazoo, MI, USA), bone morphogenetic protein-2, calcium phosphate crystals, and cancellous and/or corticocancellous allograft bone. Perioperative measures documented were operative time, estimated blood loss, length of hospital stay, and need for inpatient rehabilitation. Intraoperative complications recorded included incidental durotomy, and postoperative complications included postoperative neurological deficits, deep venous thrombosis, pulmonary embolism, and wound infection. The readmission rate was also recorded. Postoperative complications and
2.4. Imaging data Imaging data from T2-weighted MRI and three-dimensional reconstructions of CT scans was reviewed. Measurements were made from these images according to the methodology described previously by Steurer et al. [5] Assessments included the anterior–posterior (AP) diameter of the thecal sac (mm), lateral diameter of the thecal sac (mm), thecal sac cross-sectional area (mm2), bilateral lateral recess height (mm), and bilateral foraminal diameter (mm). Measurements were made at a lumbar level that was included in the sublaminar decompression. AP and lateral thecal sac diameters, thecal sac cross-sectional area, and lateral recess heights were measured at the plane with the greatest central stenosis. The foraminal diameter was measured at the plane in the foraminal space with the greatest foraminal stenosis. As the study was retrospective, preoperative and postoperative imaging was not available for all patients. Both preoperative and postoperative T2-weighted MRI and/or CT scans were available for a total of 31 patients. If a single patient had more than one of these combinations, priority was given to both pre- and postoperative MRI and then both pre- and postoperative CT scan. A total of 16 patients had a preoperative MRI and postoperative CT scan, eight patients had pre- and postoperative CT scan, and seven patients had pre- and postoperative MRI. Fusion was assessed radiographically using static radiographs to assess for bridging bone. If there was concern for pseudoarthrosis, CT scans and/or flexion-extension radiographs were obtained. Only those patients who had a sufficient length of follow-up to have documented fusion and those who were diagnosed with pseudoarthrosis were included. Patients who were lost to followup prior to fusion assessment at 12 months were excluded. Median time to fusion and fusion rate were calculated. 2.5. Statistical analysis Continuous data were calculated as median (range) or mean and categorical data as frequency (percentage). Statistical tests were used to determine significance of changes in outcome variables preoperatively and at last follow-up. McNemar’s test was used to evaluate changes in prevalence of neurologic symptoms and a paired two-sample t-test was used to assess for change in VAS pain score. A paired two-sample t-test was used to test changes in radiographical measurements of stenosis when the sample size was greater than or equal to 30, and a Wilcoxon signed-rank test was used otherwise. p < 0.05 was considered significant. 3. Results 3.1. Demographics and baseline characteristics A total of 71 patients who underwent sublaminar decompression and fusion were included in this study. All cases involved degenerative pathology, and some patients had concurrent spinal
Please cite this article in press as: Peddada K et al. Clinical outcomes following sublaminar decompression and instrumented fusion for lumbar degenerative spinal pathology. J Clin Neurosci (2016), http://dx.doi.org/10.1016/j.jocn.2016.02.001
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K. Peddada et al. / Journal of Clinical Neuroscience xxx (2016) xxx–xxx Table 1 Baseline demographics of patients undergoing sublaminar decompression and instrumented fusion for lumbar degenerative spinal pathology Patient characteristics Age, years, median (range) Sex, female, n (%) BMI, kg/m2, median (range) Smoking history, n (%)
Sublaminar decompression Number of levels decompressed, median (range) Fusion procedures, n (%) Interbody fusion PLIF TLIF Direct lateral interbody fusion Number of levels with interbody fusion, median (range) Structural allograft in interbody fusion Posterior lateral arthrodesis
60 (19–78) 40 (56) 28.4 (19.7–39.2) 23 (32)
Co-morbidities, n (%) Diabetes Hypertension Depression Osteoporosis/osteopenia Osteoarthritis Prior lumbar surgery
15 (21) 39 (55) 19 (27) 8 (11) 16 (23) 14 (20)
Preoperative diagnosis, n (%) Degenerative disc disease Disc herniation Synovial cysts Spondylolisthesis Spinal deformity
42 (59) 21 (30) 2 (3) 43 (61) 9 (13)
Symptoms at presentation, n (%) Radiculopathy Neurogenic claudication Weakness Bowel/bladder dysfunction Sensory abnormality VAS pain score, mean (range)
Table 2 Operative characteristics of patients undergoing sublaminar decompression and instrumented fusion for lumbar degenerative spinal pathology
Bone grafts used in posterior lateral arthrodesis Local autograft Iliac crest autograft Allograft DBM Optium DBM Puttya Vitoss bone graft substituteb BMP-2 Calcium phosphate crystals Number of levels with posterior lateral arthrodesis, median (range) Additional procedures performed Discectomy, n (%) Number of levels with discectomy, median (range) Spondylolisthesis reduction, n (%) Number of spondylolisthesis reduction levels, median (range)
64 (90) 17 (24) 27 (38) 12 (17) 46 (65) 6.9 (0–10)
BMI = body mass index, VAS = Visual Analog Scale.
1 (1–4) 60 (85) 24 (40) 40 (67) 1 (2) 1 (1–2) 60 (100) 71 (100) 68 (96) 30 (42) 6 (8) 4 (6) 43 (61) 19 (27) 15 (21) 16 (23) 2 (1–6)
63 (89) 1 (1–3) 32 (45) 1 (1–2)
a
LifeNet Health, Virginia Beach, VA, USA. Stryker, Kalamazoo, MI, USA. BMP = bone morphogenetic protein, DBM = demineralized bone matrix, PLIF = posterior lateral interbody fusion, TLIF = transforaminal lateral interbody fusion. b
deformity, but the goal of the primary operation was not deformity correction. The majority were female (n = 40, 56%), and the median age and body mass index at time of surgery was 60 years (range 19–78 years) and 28.4 kg/m2 (range 19.7–39.2 kg/m2), respectively (Table 1). Twenty-three (32%) patients had a smoking history, eight (11%) had osteoporosis/osteopenia, 16 (23%) had osteoarthritis, and 14 (20%) had a prior lumbar surgery. In addition to lumbar stenosis with a concern for instability, patients had the following spinal pathologies: degenerative disc disease (n = 42, 59%), disc herniation (n = 21, 30%), synovial cysts (n = 2, 3%), spondylolisthesis (n = 43, 61%), and spinal deformity (n = 9, 13%) (Table 1). The major presenting symptoms prior to surgery were radiculopathy (n = 64, 90%) and sensory abnormalities (n = 46, 65%). Other symptoms included lower extremity weakness (n = 27, 38%), neurogenic claudication (n = 17, 24%), and bowel/bladder dysfunction (n = 12, 17%). The mean preoperative VAS pain score combined for the lower back and/or legs was 6.7 (range 0–10). 3.2. Operative characteristics The median number of lumbar levels decompressed was one (range one to four) and dorsal fusion along the lamina was performed in all patients at the same levels that were decompressed (Table 2). All patients additionally underwent posterolateral fixation and fusion with pedicle screw instrumentation. The median number of posterior levels fused was two (range one to six). Bone grafts most commonly used in posterior fusions were local autograft (n = 68, 96%), Optium DBM Putty (n = 43, 61%), and iliac crest autograft (n = 30, 42%). In addition to posterior fusion, the majority of patients underwent interbody fusion (n = 60, 85%). Most interbody fusions were performed through either a transforaminal (n = 40, 67%) or posterior (n = 24, 40%) approach, with some patients having a combination of both procedures. The median number of interbody levels fused was one (range one to two), and all interbody fusions utilized a structural allograft. Other procedures performed were discectomy (n = 63, 89%) and spondylolisthesis reduction (n = 32, 45%). The median number of lumbar levels in which a discectomy or spondylolisthesis reduction were
performed were one (range one to three) and one (range one to two), respectively. 3.3. Perioperative data and outcomes The median operative time and estimated blood loss were 322 minutes (range 200–492 minutes) and 600 mL (range 15– 2250 mL), respectively (Table 3). Seven (10%) patients had intraoperative complications, with durotomy (n = 5, 7%) being the most common complication. The median length of hospitalization was five days (range 2–11 days) and the readmission rate was 6% (n = 4). Inpatient rehabilitation was required for eight (11%) patients (Table 4). The median length of follow-up was 12 months (range 1– 60 months). At last follow-up, the mean VAS pain score was 2.9 (range 0–10) and two (3%) patients eventually required adjacent level surgery. Three patients (4%) had a postoperative neurological deficit at final follow-up. One patient had a mild foot drop starting 1 month postoperatively. Another patient had a foot drop and L5 radicular pain following hardware failure of the lower instrumented level with osteopenia 2 weeks postoperatively. The third patient had persistent L4 and L5 distribution dysesthesias postoperatively. With regard to other complications, one patient developed a pulmonary embolism, two patients had a postoperative ileus, one patient had a seroma requiring drainage, one patient had a myocardial infarction, one patient had mild rhabdomyolysis, and one patient had urethral trauma from foley catheter insertion. 3.4. Comparison of preoperative and postoperative symptoms The prevalence of all symptoms, except weakness, showed statistically significant reductions postoperatively (Table 5). The largest relative percent change from before surgery was seen for neurogenic claudication (92%, p = 0.00005). Radiculopathy,
Please cite this article in press as: Peddada K et al. Clinical outcomes following sublaminar decompression and instrumented fusion for lumbar degenerative spinal pathology. J Clin Neurosci (2016), http://dx.doi.org/10.1016/j.jocn.2016.02.001
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Table 3 Perioperative data of patients undergoing sublaminar decompression and instrumented fusion for lumbar degenerative spinal pathology Perioperative variables OR time, minutes, median (range) EBL, ml, median (range) Intraoperative complications, n (%) Durotomy Postoperative complications, n (%) Postoperative neurological deficit at final follow-up DVT PE Wound infection Inpatient rehabilitation required, n (%) Length of hospitalization, days, median (range) Readmission within 30 days, n (%)
322 (200–492) 600 (15–2250) 7 (10) 5 (7) 3 0 1 0 8 5 4
(4) (0) (1) (0) (11) (2–11) (6)
DVT = deep vein thrombosis, EBL = estimated blood loss, OR = operating room, PE = pulmonary embolism.
Table 4 Clinical outcomes of patients undergoing sublaminar decompression and instrumented fusion for lumbar degenerative spinal pathology Outcome variable Length of follow-up, months, median (range) Successful fusion, n (%) Time to fusion, months, median (range) Incidence of new symptoms at last follow-up, n (%) Radiculopathy Sensory abnormality Bowel/bladder dysfunction Neurogenic claudication Weakness VAS pain score, mean (range) Adjacent level surgery needed, n (%)
12 (1–60) 37 (88) 11 (3–17) 0 (0) 2 (3) 0 (0) 0 (0) 7 (10) 2.9 (0–10) 2 (3)
VAS = Visual Analog Scale.
bowel/bladder dysfunction, sensory abnormality, and weakness showed relative percent changes from before surgery of 87% (p < 0.00001), 82% (p = 0.0039), 69% (p < 0.00001), and 34% (p = 0.19), respectively. The relative reduction in mean VAS pain score was 57% from before surgery (6.7) to last follow-up (2.9) and was statistically significant (p < 0.00001).
Fig. 1. Representative T2-weighted MRI before and after the sublaminar decompression. (a) Preoperative sagittal and (b) axial images demonstrating central and lateral recess stenosis from ligamentum hypertrophy, facet hypertrophy, and disc protrusion. (c) Postoperative sagittal and (d) axial images demonstrating treatment of central and lateral recess stenosis following sublaminar decompression with resection of ligamentum flavum and facet osteotomies (performed in conjunction with discectomy and transforaminal interbody cage placement), with remaining laminar bone.
available for fusion assessment: 37 (88%) patients achieved successful fusion with a median time to fusion of 11 (range 3–17) months (Table 4).
3.5. Radiographical measurements 4. Discussion Representative MRI and CT images demonstrating the results of the sublaminar decompression are presented in Fig. 1, 2, respectively. Radiographical measurements of central and foraminal stenosis, but not lateral recess stenosis, showed statistically significant increases following sublaminar decompression (Table 6). Mean AP thecal sac diameter, lateral thecal sac diameter, and thecal sac cross-sectional area increased by 25% (p = 0.00013), 8% (p = 0.0052), and 37% (p = 0.000012), respectively, and mean right and left foraminal diameter increased 13% (p = 0.0084) and 24% (p = 0.00012), respectively. Imaging data for 42 patients was
The clinical outcomes of a novel sublaminar decompression technique for the treatment of lumbar stenosis in conjunction with instability are presented. These results suggest that sublaminar decompression may be a favorable alternative to laminectomy because sufficient decompression can be achieved with high fusion success. Adequate decompression was achieved clinically, as evidenced by a statistically significant reduction in the VAS pain score and rates of radiculopathy, bowel/bladder dysfunction, neurogenic
Table 5 Comparison of symptoms preoperatively and postoperatively after sublaminar decompression and instrumented fusion for lumbar degenerative spinal pathology Symptoms Radiculopathy, n (%) Neurogenic claudication, n (%) Sensory abnormality, n (%) Bowel/bladder dysfunction, n (%) Weakness, n (%) VAS pain score, mean
Preoperative
Last follow-up
Relative percent change
p value
64 (90) 17 (24) 46 (65) 12 (17) 27 (38) 6.7
8 (12) 1 (2) 13 (20) 2 (3) 16 (25) 2.9
87 92 69 82 34 57
<0.00001 0.00005 <0.00001 0.0039 0.19 <0.00001
Bold type indicates statistical significance. VAS = Visual Analog Scale.
Please cite this article in press as: Peddada K et al. Clinical outcomes following sublaminar decompression and instrumented fusion for lumbar degenerative spinal pathology. J Clin Neurosci (2016), http://dx.doi.org/10.1016/j.jocn.2016.02.001
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Fig. 2. Representative CT images before and after sublaminar decompression. (a) Preoperative sagittal CT scan demonstrating central stenosis at L3–L4 from grade 1 spondylolisthesis and calcified ligamentum flavum, and central stenosis at L5–S1 from ligamentum hypertrophy and calcified disc protrusion. (b) Preoperative axial CT image at L3–L4 demonstrating central and lateral recess stenosis and (c) axial CT image at L5–S1 demonstrating central, lateral recess, and foraminal stenosis. (d) Postoperative sagittal CT image demonstrating decompression of central canal at L3–L4 and L5–S1 (with transforaminal interbody graft only at L3–L4). (e) Axial CT image at L3–L4 following sublaminar decompression with resolution of central and lateral recess stenosis, with preservation of dorsal bone with dorsal bone graft placement (in conjunction with discectomy for interbody graft placement). (f) Axial CT image at L5–S1 following sublaminar decompression showing decompression of central and lateral recess stenosis, while calcified disc protrusion remains.
Table 6 Analysis of radiographical changes after sublaminar decompression and instrumented fusion for lumbar degenerative spinal pathology Radiographical measurements
Preoperative
Last follow-up
Percent change
p value
10.4 17.2 153
13.0 18.6 209
25 8 37
0.00013 0.0052 0.000012
Lateral recess stenosis measurements Right lateral recess height, mm, mean Left lateral recess height, mm, mean
5.9 5.8
5.9 6.3
0 9
0.43 0.027
Foraminal stenosis measurements Right foraminal diameter, mm, mean Left foraminal diameter, mm, mean
4.6 4.2
5.2 5.2
13 24
0.0084 0.00012
Central stenosis measurements AP thecal sac diameter, mm, mean Lateral thecal sac diameter, mm, mean Thecal sac cross-sectional area, mm2, mean
Bold type indicates statistical significance. AP = anteroposterior.
claudication, and sensory abnormality at last follow-up. Decompression was also achieved radiographically in the central spinal canal and neural foramina, with an 88% fusion rate. The pseudoarthrosis rate of 12% is lower than some previously reported rates of pseudoarthrosis following laminectomy, which can be as high as 27–30% [3,4]. Although Nayak and Sannegowda recently showed a pseudoarthrosis rate of 5.4% following laminectomy [6], fewer lumbar levels per patient were fused in their study and the types and extent of degenerative spinal pathology in their patient population were different to those seen in this study.
A number of decompressive procedures that preserve the posterior spinal elements and provide greater bone surface area than a laminectomy for fusion have been described. However, this sublaminar decompression offers advantages that can result in better fusion outcomes and may more effectively treat lumbar stenosis compared to these other procedures. One such procedure is a unilateral/bilateral laminotomy, which involves removal of the lower and upper part of the superior and inferior vertebral arch, respectively, while leaving the interspinous and supraspinous ligaments intact [7]. Although the extent of decompression a laminotomy
Please cite this article in press as: Peddada K et al. Clinical outcomes following sublaminar decompression and instrumented fusion for lumbar degenerative spinal pathology. J Clin Neurosci (2016), http://dx.doi.org/10.1016/j.jocn.2016.02.001
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can achieve is comparable to a laminectomy, a key advantage of sublaminar decompression is the ability to fuse dorsally along the intact lamina in addition to posterolaterally and in the interbody space, leading to potentially higher rates of fusion [8,9]. Dorsal fusion following a laminotomy can be challenging depending on the extent of bone that is removed. Furthermore, compared to sublaminar decompression, a lamintotomy provides less access to the lateral recess and neural foramen, potentially limiting decompression in these regions [10]. The microsurgical bilateral decompression via a unilateral approach is a minimally invasive adaptation of a laminotomy that is beneficial because it reduces damage to the paraspinal musculature [11]. However, unlike sublaminar decompression, the utility of this approach generally is limited to treatment of central stenosis, specifically when the spinal canal is round or oval shaped and not trefoil-shaped [12]. The wide fenestration technique described by Nakai et al. [13] and the chimney sublaminar decompression by Lin et al. [14] also primarily address central stenosis. Alternatively, Nemani et al. [10] described the use of the stand-alone direct lateral lumbar interbody approach for lumbar stenosis with instability. This minimally invasive procedure avoids traditional anterior or posterior decompression methods by indirectly achieving decompression during fusion. However, it may only adequately address foraminal stenosis and the study showed about 10% of patients ultimately required a separate posterior decompression [10]. Interspinous dynamic stabilization has also been proposed as an alternative to decompression and fusion in treating lumbar stenosis with instability. In this technique, devices are inserted into the interspinous process to restrict movement of spinal segments in directions that cause instability or pain and increase the dimensions of and limit dynamic compression of the spinal canal, thereby emulating the functions of spinal fusion and decompression, respectively, through a less invasive procedure [15,16]. Despite this theoretical advantage, comparative studies with decompression and fusion have failed to demonstrate superior improvements from this technique in functional status and pain severity [15,17]. Furthermore, complication and revision surgery rates around 30% have been reported, suggesting decompression and fusion are currently still safer and more effective than interspinous dynamic stabilization [17,18]. Interestingly, in this study, sublaminar decompression did not substantially change the lateral recess dimensions or lead to improvement in strength postoperatively. As discussed in the prior technical manuscript (Clinical Spine Surgery, 2016, Under review (unpublished results)), sublaminar decompression allows sufficient access to and enables decompression of the lateral recess. However, a potential reason for the discrepancy is that following decompression, the osteotomy is closed to increase lordosis, and this may eliminate some of the lateral recess decompression. Therefore, we have found that there is a balance between aggressively closing the osteotomy and bone removal for decompression. Additionally, there may not have been enough patients with available imaging in this study with severe lateral recess stenosis to demonstrate a significant improvement. Another notable finding was that all neurologic symptoms improved by last follow-up except for weakness. One potential reason could be that the preoperative weakness was more longstanding and thus there was not a substantial improvement even following adequate decompression. The study has several important limitations. First, the retrospective study design has inherent limitations. Additionally, there was a lack of a control group of patients undergoing laminectomy and/or other decompressive procedures in conjunction with instrumented fusion, which limits any ability to conclusively determine if sublaminar decompression is superior or inferior to other forms of decompression and fusion. Furthermore, the use
of different imaging modalities and the limited number of patients with available preoperative and postoperative imaging (T2weighted MRI and CT scans) when evaluating stenosis radiographically may introduce heterogeneity in the results. Finally, static radiographs were used to assess fusion status, while the ideal assessment would have involved assessment of both bridging bone as well as motion criteria. However, most of these limitations were consequences of the retrospective nature of this study. In the future, it would be ideal to conduct a prospective randomized trial to directly compare the clinical and radiographical outcomes between laminectomy and posterolateral fusion sublaminar decompression and posterolateral fusion to conclusively determine the better procedure. Additional future studies will examine the improvement in alignment that can be achieved with this technique because of the osteotomy and whether or not this improved alignment affects outcomes.
5. Conclusions To our knowledge, this is the first study to evaluate sublaminar decompression with fusion as a treatment for lumbar stenosis and instability in degenerative pathology of the lumbar spine. It was demonstrated that sublaminar decompression can achieve adequate decompression, particularly in the central spinal canal and neural foramen, with substantial improvements in neurological symptoms. Furthermore, the fusion rate was high and compares favorably to fusion rates following a laminectomy. Hence, sublaminar decompression may be an effective alternative to laminectomy and other decompressive procedures in the treatment of lumbar stenosis with instability.
Conflicts of Interest/Disclosures The authors declare that they have no financial or other conflicts of interest in relation to this research and its publication. Acknowledgements The Gordon and Marilyn Macklin Foundation supported this study. References [1] Weinstein JN, Lurie JD, Olson PR, et al. United States’ trends and regional variations in lumbar spine surgery: 1992–2003. Spine (Phila Pa 1976) 2006;31:2707–14. [2] Omidi-Kashani F, Hasankhani EG, Ashjazadeh A. Lumbar spinal stenosis: who should be fused? An updated review. Asian Spine J 2014;8:521–30. [3] Aebi M. The adult scoliosis. Eur Spine J 2005;14:925–48. [4] Lee CK. Lumbar spinal instability (olisthesis) after extensive posterior spinal decompression. Spine (Phila Pa 1976) 1983;8:429–33. [5] Steurer J, Roner S, Gnannt R, et al. Quantitative radiologic criteria for the diagnosis of lumbar spinal stenosis: a systematic literature review. BMC Musculoskelet Disord 2011;12:175. [6] Nayak MT, Sannegowda RB. Clinical and radiological outcome in cases of posterolateral fusion with instrumentation for lumbar spondylolisthesis. J Clin Diagn Res 2015;9:PC17–21. [7] Overdevest G, Vleggeert-Lankamp C, Jacobs W, et al. Effectiveness of posterior decompression techniques compared with conventional laminectomy for lumbar stenosis. Eur Spine J 2015;24:2244–63. [8] Guiot BH, Khoo LT, Fessler RG. A minimally invasive technique for decompression of the lumbar spine. Spine (Phila Pa 1976) 2002;27:432–8. [9] Spetzger U, Bertalanffy H, Naujokat C, et al. Unilateral laminotomy for bilateral decompression of lumbar spinal stenosis. Part I: anatomical and surgical considerations. Acta Neurochir (Wien) 1997;139:392–6. [10] Nemani VM, Aichmair A, Taher F, et al. Rate of revision surgery after standalone lateral lumbar interbody fusion for lumbar spinal stenosis. Spine (Phila Pa 1976) 2014;39:326–31. [11] Weiner BK, Walker M, Brower RS, et al. Microdecompression for lumbar spinal canal stenosis. Spine (Phila Pa 1976) 1999;24:2268–72.
Please cite this article in press as: Peddada K et al. Clinical outcomes following sublaminar decompression and instrumented fusion for lumbar degenerative spinal pathology. J Clin Neurosci (2016), http://dx.doi.org/10.1016/j.jocn.2016.02.001
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Please cite this article in press as: Peddada K et al. Clinical outcomes following sublaminar decompression and instrumented fusion for lumbar degenerative spinal pathology. J Clin Neurosci (2016), http://dx.doi.org/10.1016/j.jocn.2016.02.001