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Partial Vertebrae Resection Laterally to Harvest Supplemental Autograft Bone for Anterior Cervical Discectomy and Fusion: A Technical Note and Outcomes
Technical Note
Partial Vertebrae Resection Laterally to Harvest Supplemental Autograft Bone for Anterior Cervical Discectomy and Fusion: A Technical Note and Outcomes Xiaowei Liu, Zhenfang Wu, Gang Liu, Guojing Sun, Zhili Kang, Jianning Zhao, Bin Xu
PURPOSE: To evaluate the safety and effectiveness of partial vertebrae resection laterally through intervertebral space to harvest supplemental autograft bone for anterior cervical discectomy and fusion (ACDF).
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METHODS: Patients who accepted 1-segment (n [ 19, 38.2 months follow-up) or 2-segment (n [ 17, 40.4 months follow-up) ACDF with supplemental autograft bone were included. Cervical lordosis (CL), segmental lordosis (SL), anterior segment height (ASH), and posterior segment height (PSH) on neutrally lateral radiography, and intervertebral fusion rate on computed tomography were measured. The operation time, intraoperative blood loss, Japanese Orthopedic Association score, visual analog scale around the neck or arm, Neck Disability Index, and complications were also recorded.
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RESULTS: Mean operation time was 86.2 and 115.6 minutes, and the intraoperative blood loss was 41.7 and 79.4 mL in cases with 1-segment and 2-segment ACDF, respectively. At the final visit, the visual analog scale score and Neck Disability Index significantly decreased, and the Japanese Orthopedic Association score significantly increased. Significant increases were observed in the ASH, PSH, CL, and SL after 2-segment ACDF. Significant increases were observed in the CL and SL after 1-segment ACDF, but not in the ASH and PSH. All the ASH, PSH, CL, and SL kept unchanged at the final visit. All cases acquired definite intervertebral fusion, and the incidence of cage
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Key words Anterior cervical discectomy and fusion - Partial vertebrae resection - Supplemental autograft bone -
Abbreviations and Acronyms ACDF: Anterior cervical discectomy and fusion ASH: Anterior segment height CL: Cervical lordosis CT: Computed tomography JOA: Japanese Orthopedic Association NDI: Neck Disability Index PEEK: Polyetheretherketone PSH: Posterior segment height
subsidence was 5.3% after 1-segment and 17.6% after 2-segment ACDF at the final visit. CONCLUSIONS: Partial vertebrae resection laterally through the intervertebral space was a safe and effective method to harvest supplemental autograft bone for the ACDF.
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INTRODUCTION
F
or patients with symptomatic spinal cord or nerve root compression, sufficient decompression could be usually achieved after anterior cervical discectomy and fusion (ACDF) if there was not ossification of posterior longitudinal ligament, large osteophyte, or huge disc herniation.1,2 Because intervertebral fusion was the key for maintaining long-term outcomes, autogenous bone being harvested from iliac crest was reported to be the gold standard, but its low supporting intensity and high rate of donor morbidity negatively influence the radiologic and clinical outcomes.3-5 Applications of the intervertebral cage and rigid internal fixation system could provide immediate stability and increase the fusion rate, but how to gain sufficiently autologous cancellous bone graft without autograft-harvest associated complications was still controversial.6 Although both allograft and synthetic biological materials with osteogenic, osteoconductive, and osteoinductive characteristics could avoid donor morbidity, insufficient fusion rate and extra financial cost have turned the focus to autograft again.5,7,8 In keeping with previous studies, granular autograft bone being harvested by resection of osteophytes and vertebral chips was
SL: Segmental lordosis VAS: Visual analog scale Department of Orthopaedics, Jinling Hospital, Medicine College, Nanjing University, Nanjing, Jiangsu, China To whom correspondence should be addressed: Bin Xu, M.D. [E-mail: [email protected]] Xiaowei Liu and Zhenfang Wu contributed equally to this article and should be regarded as co-first authors. Citation: World Neurosurg. (2019) 121:44-50. https://doi.org/10.1016/j.wneu.2018.09.141 Journal homepage: www.WORLDNEUROSURGERY.org Available online: www.sciencedirect.com 1878-8750/$ - see front matter ª 2018 Elsevier Inc. All rights reserved.
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TECHNICAL NOTE
Table 1. General Information of the Included Cases 1-Segment Anterior 2-Segment Anterior Cervical Discectomy Cervical Discectomy and Fusion and Fusion Age (years) Gender (male/female, n)
53.6 11.7
56.5 13.6
11/8
12/5
Smoker (n)
5
7
With diabetes mellitus (n)
4
3
Body mass index (kg/m2)
26.5 5.2
24.3 6.6
Cervical spondylotic myelopathy
13
11
Cervical spondylotic radiculopathy
2
3
Cervical spondylotic myelopathy þ cervical spondylotic radiculopathy
4
3
Osteophyte
3
5
Herniated disc
10
7
Osteophyte and disc
6
5
C2/3
0
1
C3/4
2
7
C4/5
5
12
C5/6
9
10
C6/7
3
4
4
4
Diagnosis (n)
Main compressive cause (n)
Decompression level
With anterior osteophyte (n) High signal in spinal cord (n) Follow-up, months (range)
7
7
38.2 15.1 (24e50)
40.4 12.6 (26e47)
or 2-segment ACDF with vertebral chips and supplemental autograft bone that was harvested by partial vertebrae resection for the treatment of cervical spondylotic myelopathy or cervical spondylotic radiculopathy. The exclusion criteria were 1) history of spinal trauma, spinal surgery, or tumor (n ¼ 3); 2) with validated rheumatoid arthritis, ankylosing spondylitis, or spinal infection (n ¼ 1); and 3) with intact radiologic images (n ¼ 2) or lost to follow-up within 12 months postoperatively (n ¼ 1). A total of 36 patients were included in this study and the general information is shown in Table 1. Surgical Approach A right-side Smith-Robinson approach was carried out to expose cervical vertebral bodies and targeted disc after general anesthesia. If anterior osteophyte was lying before the intervertebral space, it was first resected. After removing the intervertebral disc, f anterior chips of the vertebral bodies were then resected for better vision and operation space in all patients. In patients with osteophyte behind the posterior wall of the vertebral bodies, the osteophyte and posterior chips of the vertebral bodies were then resected for sufficient decompression. The posterior longitudinal ligament was resected in all patients. The size of the polyetheretherketone (PEEK [DePuy, Raynham, Massachusett, USA]) cage was decided by model test and intraoperative fluoroscopy, to acquire appropriate restoration of cervical alignment. A schematic diagram of harvesting the maximum volume of the supplement autograft bone by partial vertebrae resection in the procedure of 2-segment ACDF is shown in Figure 1. The
used to fill the cage in our center.9-12 However, the osteophyte was mostly made of cortical bone and it was not suitable for graft fusion. Furthermore, resection of posterior vertebrae chips might not be necessary in patients with mild cervical degeneration or lone disc herniation. So, in patients with ACDF, achievement of cancellous autograft bone was usually insufficient and might be associated with nonfusion postoperatively.13 Inspired by harvesting autograft bone from adjacent lumbar vertebrae, since 2013, we have resected partial vertebrae laterally through intervertebral space and supplemented them to fill the cage if achievement of cancellous bone was insufficient during the ACDF procedure.14 In this study, we report outcomes of this modified technique, to assess its safety and effectiveness.
METHODS Patient Selection Medical records from May 2013 to March 2017 were retrospectively reviewed of 43 patients who accepted 1-segment
WORLD NEUROSURGERY 121: 44-50, JANUARY 2019
Figure 1. Schematic diagram of partial vertebrae resection. On the coronal view of 2-segment anterior cervical discectomy and fusion (A), gray annuluses were entry points of screws and 4 red frames were probable vertebrae resection zones for maximum harvest of autograft. The resection zone was about 2e3 mm both wide and long, and it should not influence the screw implant. The red frame in (B) shows the depth of vertebrae resection on horizontal view, without involvement of the posterior wall of the vertebrae.
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TECHNICAL NOTE
Figure 2. (A, B) Intraoperative observation of partial vertebra resection through intervertebral space. (C) Bone graft harvesting from vertebra (white arrow) and
resection was carried out just along the interior margin of the right musculus longus coli by a 2-mm rongeur in both sagittal and coronal planes, and the bony groove was then covered by bone wax for hemostasis (Figures 1A and 2A and B). Two bony grooves in 1-level ACDF or 4 in 2-level ACDF could be made for maximum harvest of autograft. To reduce iatrogenic damage of the vertebral end plate integrity, both length and width of the bony groove were just 2e3 mm. Depth of the bony groove could be expanded in the sagittal plane for harvesting more autograft, but the posterior wall of targeted vertebral bodies should not be involved to avoid the risk of spinal cord injury (Figure 1B). After eliminating the osteophyte and visual cortical bone from both supplemental autograft bone and vertebral chips, sufficient cancellous bone was filled into the PEEK cage (Figure 2C). After inserting the PEEK cage into the intervertebral space, a semi-constrained plate (Sky-line [DePuy, USA]) was used for bridging the involved vertebrae. The drainage tube was removed within 24 hours postoperatively. Each patient wore a Philadelphia neck collar for 4e6 weeks and then started to do regular neck exercise.
the polyetheretherketone cage filling with bone from osteophyte and vertebral chips.
Radiologic and Clinical Assessments All our patients received neutrally lateral radiographs preoperatively, and 3 days, 3 months, 6 months, 12 months, and then per year postoperatively. All received computed tomography (CT) 12 months postoperatively. Cervical lordosis (CL) was evaluated by the C2-C7 Cobb angle and segmental lordosis (SL) by fused segment Cobb angle preoperatively, 3 days postoperatively, and at final visit. The distance between the anterior or posterior margins located at the upper end plate of the cephalic vertebrae and lower end plate of the caudal vertebrae on neutrally lateral radiography was defined as the anterior segment height (ASH) or posterior segment height (PSH), respectively. Loss of the CL, SL, ASH, or PSH was calculated as final indexepostoperative index. Segmental subsidence was defined if loss of the ASH or PSH was >2 mm and severe subsidence was confirmed when the loss of ASH or PSH was 3 mm. Intervertebral fusion was defined when there were continuous trabeculae across the interspace on sagittal CT at 12 months postoperatively (Figures 3 and 4). Operation time and intraoperative blood loss were recorded. Neurologic function was evaluated by the Japanese
Figure 3. A 41-year-old female patient with mild cervical degeneration (A) and disc herniation at C6/7 (B). She accepted C6/7 anterior cervical discectomy and fusion with partial vertebra resection at the C7 vertebrae. The sagittal bone-window computed tomography showed definite intervertebral fusion (C) at 13 months postoperatively, and the cross-section computed tomography showed the bony groove at the right side of the C7 vertebra cephalad (D, white arrow).
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Figure 4. A 50-year-old female patient with cord compression at C4/5 and C5/6, with mixed type of ossification of posterior longitudinal ligament from C2-C6 (A, B). She accepted C/5 and C5/6 anterior cervical discectomy and fusion, with partial vertebra resection at the right of C5 both cephalad and caudally. The sagittal bone-window computed tomography showed intervertebral fusion 12 months postoperatively (C). Cross-section computed tomography showed a significant bony cavity (D, white arrow).
Orthopedic Association (JOA) scoring system, and its recovery rate was calculated as (final follow-up JOA scoreepreoperative JOA score)/(17epreoperative JOA score) 100%. Visual analog scale (VAS) score around the neck or arm and Neck Disability Index (NDI) were used to assess the influence of pain on patients’ daily lives. Complications including implant failure, infection, neurologic deterioration, dysphagia, and hoarseness were also recorded. Statistical Analysis PASW Statistics 18.0 (SPSS Inc., Chicago, Illinois, USA) was used to analyze clinical and radiologic results. Intragroup comparison of quantitative data was made by the pairedsamples t test. A P value <0.05 was defined to be statistically significant.
All patients acquired intervertebral fusion, which was verified on bone-window CT 12 months postoperatively. As shown in Table 4, there were losses of the ASH, PSH, CL, and SL at the final visit compared with 3 days postoperatively. Cage subsidence (5.3% and 17.6%), dysphagia (15.8% and 41.2%) and hoarseness (5.3% and 17.6%) were the main
Table 2. Clinical Outcomes in Cases With 1-Segment or 2-Segment Anterior Cervical Discectomy and Fusion 1-Segment Anterior Cervical Discectomy and Fusion
2-Segment Anterior Cervical Discectomy and Fusion
Japanese Orthopedic Association score Preoperative
9.6 4.0
9.3 3.8
RESULTS
Final visit
14.5 2.9
14.1 3.2
The mean operation time was 76.2 17.9 and 95.6 23.4 minutes, and intraoperative blood loss was 41.7 16.5 and 79.4 24.8 mL in patients with 1-segment and 2-segment ACDF, respectively. At the final visit, we found significant increase in the JOA score and decreases in both the VAS score and NDI at the final visit (Table 2). The mean neurologic recovery rate was 65.7% and 63.2% in patients with 1-segment and 2-segment ACDF, respectively.
P value
0.019*
0.001#
Recovery rate (%)
65.7 15.3
63.2 18.4
Compared with preoperative data, there were significant increases in the ASH, PSH, CL, and SL in patients with 2-segment ACDF both 3 days postoperatively and at final visit. In patients with 1-segment ACDF, there were significant increases in both the CL and SL, but only increasing trends in the mean ASH and PSH (Table 3). Although decreasing trends could be observed in the ASH, PSH, CL, and SL in patients with 1-segment or 2segment ACDF, there were no significant differences in these indexes both 3 days postoperatively and at the final visit.
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Visual analog scale score around neck or arm (score) Preoperative
6.3 3.2
6.8 3.7
Final visit
2.3 1.1
2.7 1.6
0#
0#
Preoperative
30.1 9.5
36.4 10.6
Final visit
12.0 4.2
16.7 5.1
0#
0#
P value Neck Disability Index (%)
P value *P value <0.05. #P value <0.001.
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Table 3. Radiologic Outcomes After 1-Segment or 2-Segment Anterior Cervical Discectomy and Fusion 1-Segment Anterior Cervical Discectomy and Fusion
2-Segment Anterior Cervical Discectomy and Fusion
Mean anterior segment height (mm) Preoperatively
31.3 5.5
51.0 5.7
3 days postoperatively
33.5 4.0
55.3 6.0*
Final visit
32.6 4.3
54.1 6.6*
30.5 4.4
Loss of anterior segment height (mm)
0.8 0.3
1.1 0.6
Loss of posterior segment height (mm)
0.5 0.3
0.8 0.5
1.4 0.8
2.7 1.1
0.6 0.2
1.0 0.6
Loss of cervical lordosis ( )
49.7 5.2
Subsidence (n)
1
3
Dysphagia (n)
3
7
3 days postoperatively
32.5 3.8
53.6 5.5y
Final visit
31.9 3.6
53.2 5.2y
Mean cervical lordosis ( )
Hoarseness (n)
1
2
Severe subsidence (n)
0
0
Neurologic deterioration (n)
0
0
Preoperatively
20.6 9.7
21.0 8.8
Implant failure (n)
0
0
3 days postoperatively
26.5 7.1y
28.7 8.6y
Infection (n)
0
0
25.2 7.2y
26.0 6.7y
Final visit
Mean segmental lordosis ( ) Preoperatively
5.2 3.0
8.6 3.7
3 days postoperatively
7.9 2.0*
11.2 2.4y
Final visit
7.3 1.5*
10.3 1.6y
*P < 0.05. yP < 0.001.
complications in patients with 1-segment and 2-segment ACDF, respectively. No patient experienced severe subsidence, neurologic deterioration, implant failure, and infection.
DISCUSSION Autogenous bone was considered to be the gold standard for intervertebral fusion. Autograft has been commonly harvested from the iliac crest since the ACDF was developed in the 1960s, but donor-site complications including infection, persistent pain or paresthesia, and injuries of nerve root and blood vessel resulted in reports by patients of dissatisfaction.15,16 Although application of allograft or synthetic bone materials such as hydroxyapatite, polymethylmethacrylate, b-tricalcium phosphate, biocompatible osteoconductive polymer, and heterologous artificial graft could avoid donor-site morbidity, medical expenses would increase and 2 main problems still remained to be solved.8 First, the fusion rate after the ACDF was similar or even lower with the application of synthetic biological materials compared that with the autograft.8,17 Second, the incidence of radiologic failures, including graft protrusion or settling, disc space collapse, loss of cervical alignment, and delayed fusion or nonunion, was reported to be higher in patients with the synthetic biological materials than those with autograft.8,18
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1-Segment Anterior 2-Segment Anterior Cervical Discectomy Cervical Discectomy and Fusion and Fusion
Loss of segmental lordosis ( )
Mean posterior segment height (mm) Preoperatively
Table 4. Radiologic Index Changes and Complications at the Final Visit
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Because the superiority of the allograft or synthetic bone materials over the autograft in promoting intervertebral fusion was still controversial and the needed volume of bone graft is small because of the application of PEEK cage, Iwasaki et al.19 reported their outcomes of harvesting cancellous bone from the clavicle for filling the cage in 16 patients.8 Although the fusion rate was satisfactory, a risk of subclavian major vessel or lung injury, undeserved clavicle fracture, or local infection might be unavoidable because of the learning curve and growing sample. Harvest of granular bone from osteophyte and vertebral chips was another safe method, but because the osteophyte was a pathologically hypertrophic osteosclerosis and resection of vertebrae chips was unnecessary in patients with mild degeneration, mixture or lone application of the osteophyte might contribute to postoperative nonunion (range, 3%e 9%).2,9,10,20,21 To acquire sufficient cancellous bone within the local operation region was still the key precondition for popularizing ACDF. Because the vertebral body consisted mainly of cancellous bone, it could be an optional source of ideal autograft.2 Cylinder autograft was harvested ventrally from adjacent lumbar vertebrae and the fusion rate could be 100% 28 months postoperatively, but it was unfeasible in the ACDF because of the smaller size of the cervical vertebrae.14 The Williams method of harvesting autograft from adjacent vertebrae and end plate through the intervertebral space was more like corpectomy, but the fusion rate was low (4/7), which was attributed to insufficient intervertebral support and stability.22 In this study, we resected lateral vertebrae through the intervertebral space for maximum preservation of the integrity of anterior supporting structures. Supplemental cancellous bone harvested from the vertebral body was then mixed with vertebral chips to fill the PEEK cage. At the final visit, all patients acquired CT-confirmed fusion, and this rate seemed to be reliable compared with that after stand-alone cage (83.3%),
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TECHNICAL NOTE
anchored cage (87%), or cage-plate system (range, 0%e100%) with application of bone substitutes.8,23 This situation made us believe that partial vertebrae resection could provide sufficient supplemental autograft and a reliable intervertebral fusion rate, but a further case-control or randomized controlled study is needed to provide more information. The cage subsidence, with a range from 19.3% to 42.5%, was associated with progressive neurologic deterioration or alignment deformity, persistent neck pain, or even implant failure after ACDF.24,25 The integrity of the end plate was important for preventing intervertebral collapse, but our method of harvesting supplemental bone might destroy the end plate.22,26 However, because the resection was carried out unilaterally and most of the end plate was still left and kept integral, the main contact surface between the cage and end plate was preserved and the load-bearing area was sufficient. Moreover, immediate stabilization by the screw-plate system and early fusion by sufficient cancellous bone might also contribute to decreasing the incidence of cage subsidence.27 As shown in Tables 2e4, the total incidence of cage subsidence in the 2 groups was just 11.1%, and losses of the CL and SL and decreases in the VAS score and NDI were also comparable to previous studies reported after ACDF.28 All these results made us believe that harvesting autogenous bone by partial vertebrae resection laterally would be a safe supplementary method for ACDF, especially when we could not obtain enough autograft. It was not difficult for an experienced spinal surgeon to harvest autograft from the vertebral body through the intervertebral
REFERENCES 1. Ma Z, Ma X, Yang H, Guan X, Li X. Anterior cervical discectomy and fusion versus cervical arthroplasty for the management of cervical spondylosis: a meta-analysis. Eur Spine J. 2017;26: 998-1008. 2. Wang T, Wang H, Liu S, An HD, Liu H, Ding WY. Anterior cervical discectomy and fusion versus anterior cervical corpectomy and fusion in multilevel cervical spondylotic myelopathy: a metaanalysis. Medicine (Baltimore). 2016;95:e5437. 3. Armaghani SJ, Even JL, Zern EK, Braly BA, Kang JD, Devin CJ. The evaluation of donor site pain after harvest of tricortical anterior iliac crest bone graft for spinal surgery: a prospective study. Spine (Phila Pa 1976). 2016;41:E191-E196. 4. Young WF, Rosenwasser RH. An early comparative analysis of the use of fibular allograft versus autologous iliac crest graft for interbody fusion after anterior cervical discectomy. Spine (Phila Pa 1976). 1993;18:1123-1124. 5. Chau AM, Mobbs RJ. Bone graft substitutes in anterior cervical discectomy and fusion. Eur Spine J. 2009;18:449-464. 6. Oliver JD, Goncalves S, Kerezoudis P, Alvi MA, Freedman BA, Nassr A, et al. Comparison of outcomes for anterior cervical discectomy and fusion with and without anterior plate fixation: a systematic review and meta-analysis. Spine (Phila Pa 1976). 2018;43:E413-E422.
space, and the operation time in 2 groups did not significantly increase compared with previous studies. Intraoperative blood loss was not increased as a result of immediate hemostasis, but only a thin layer of bone wax should be left within the bony groove for maximum reduction of the risk of infection or rejection. To prevent potential injuries of the nerve root and spinal cord, the vertebrae resection should be carried out along the musculus longus coli and without involvement of the posterior wall of the vertebrae. Both satisfactory neurologic recovery and the fact that no patient experienced neurologic deterioration prove the effectiveness of our design (Tables 2 and 4). An increasing trend for occurrence of dysphagia in patients with 2-level ACDF might be attributed to greater involvement of C2/3 and C3/4 and prolonged operation time, but more attention should also be paid to reducing mechanical injury of the musculus longus coli during partial vertebrae resection.29,30 These results prove the safety of this modified method for harvesting supplemental autograft bone. Moreover, the bony groove within the involved vertebrae might provide extra drainage, but the advantage of preventing postoperative hematoma was not evident because of our small sample.
CONCLUSIONS For patients with insufficient autograft bone during ACDF, partial vertebrae resection laterally through the intervertebral space could be an effective and safe method for supplemental bone harvest.
7. Zadegan SA, Abedi A, Jazayeri SB, Vaccaro AR, Rahimi-Movaghar V. Demineralized bone matrix in anterior cervical discectomy and fusion: a systematic review. Eur Spine J. 2017;26:958-974. 8. Buser Z, Brodke DS, Youssef JA, Meisel HJ, Myhre SL, Hashimoto R, et al. Synthetic bone graft versus autograft or allograft for spinal fusion: a systematic review. J Neurosurg Spine. 2016; 25:509-516.
detection on computed tomography. Comput Med Imaging Graph. 2014;38:628-638. 14. Arlet V, Jiang L, Steffen T, Ouellet J, Reindl R, Aebi M. Harvesting local cylinder autograft from adjacent vertebral body for anterior lumbar interbody fusion: surgical technique, operative feasibility and preliminary clinical results. Eur Spine J. 2006;15:1352-1359.
9. Pitzen T, Kiefer R, Munchen D, Barbier D, Reith W, Steudel WI. Filling a cervical spine cage with local autograft: change of bone density and assessment of bony fusion. Zentralbl Neurochir. 2006;67:8-13.
15. Pollock R, Alcelik I, Bhatia C, Chuter G, Lingutla K, Budithi C, et al. Donor site morbidity following iliac crest bone harvesting for cervical fusion: a comparison between minimally invasive and open techniques. Eur Spine J. 2008;17:845-852.
10. Shad A, Leach JC, Teddy PJ, Cadoux-Hudson TA. Use of the Solis cage and local autologous bone graft for anterior cervical discectomy and fusion: early technical experience. J Neurosurg Spine. 2005; 2:116-122.
16. Fowler BL, Dall BE, Rowe DE. Complications associated with harvesting autogenous iliac bone graft. Am J Orthop (Belle Mead NJ). 1995;24:895-903.
11. Dang L, Sun Y, Wang S, Pan S, Li M, Zhang L, et al. A new source of autograft bone for interbody fusion in anterior cervical discectomy and fusion surgery: experience in 893 cases. Br J Neurosurg. 2017;31:33-38. 12. Park JI, Cho DC, Kim KT, Sung JK. Anterior cervical discectomy and fusion using a stand-alone polyetheretherketone cage packed with local autobone: assessment of bone fusion and subsidence. J Korean Neurosurg Soc. 2013;54:189-193. 13. Yao J, Burns JE, Munoz H, Summers RM. Cortical shell unwrapping for vertebral body abnormality
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17. Miller LE, Block JE. Safety and effectiveness of bone allografts in anterior cervical discectomy and fusion surgery. Spine (Phila Pa 1976). 2011;36: 2045-2050. 18. Shriver MF, Lewis DJ, Kshettry VR, Rosenbaum BP, Benzel EC, Mroz TE. Pseudoarthrosis rates in anterior cervical discectomy and fusion: a meta-analysis. Spine J. 2015;15: 2016-2027. 19. Iwasaki K, Ikedo T, Hashikata H, Toda H. Autologous clavicle bone graft for anterior cervical discectomy and fusion with titanium interbody cage. J Neurosurg Spine. 2014;21:761-768.
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20. Liao JC, Niu CC, Chen WJ, Chen LH. Polyetheretherketone (PEEK) cage filled with cancellous allograft in anterior cervical discectomy and fusion. Int Orthop. 2008;32:643-648. 21. Tabaraee E, Ahn J, Bohl DD, Collins MJ, Massel DH, Aboushaala K, et al. Comparison of surgical outcomes, narcotics utilization, and costs after an anterior cervical discectomy and fusion: stand-alone cage versus anterior plating. Clin Spine Surg. 2017;30:E1201-E1205. 22. McGuire RA, St John K. Comparison of anterior cervical fusions using autogenous bone graft obtained from the cervical vertebrae to the modified Smith-Robinson technique. J Spinal Disord. 1994;7: 499-503. 23. Lee YS, Kim YB, Park SW. Does a zero-profile anchored cage offer additional stabilization as anterior cervical plate? Spine (Phila Pa 1976). 2015; 40:E563-E570. 24. Chen Y, Chen D, Guo Y, Wang X, Lu X, He Z, et al. Subsidence of titanium mesh cage: a study
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based on 300 cases. J Spinal Disord Tech. 2008;21: 489-492. 25. Karikari IO, Jain D, Owens TR, Gottfried O, Hodges TR, Nimjee SM, et al. Impact of subsidence on clinical outcomes and radiographic fusion rates in anterior cervical discectomy and fusion: a systematic review. J Spinal Disord Tech. 2014;27:1-10. 26. Cheng CC, Ordway NR, Zhang X, Lu YM, Fang H, Fayyazi AH. Loss of cervical endplate integrity following minimal surface preparation. Spine (Phila Pa 1976). 2007;32:1852-1855. 27. Lee CH, Hyun SJ, Kim MJ, Yeom JS, Kim WH, Kim KJ, et al. Comparative analysis of 3 different construct systems for single-level anterior cervical discectomy and fusion: stand-alone cage, iliac graft plus plate augmentation, and cage plus plating. J Spinal Disord Tech. 2013;26:112-118. 28. Nambiar M, Phan K, Cunningham JE, Yang Y, Turner PL, Mobbs R. Locking stand-alone cages versus anterior plate constructs in single-level
fusion for degenerative cervical disease: a systematic review and meta-analysis. Eur Spine J. 2017; 26:2258-2266. 29. Simoes J, Romao J, Cunha A, Paiva S, Migueis A. Neck pain and acute dysphagia. Dysphagia. 2017; 32:123-125. 30. Joaquim AF, Murar J, Savage JW, Patel AA. Dysphagia after anterior cervical spine surgery: a systematic review of potential preventative measures. Spine J. 2014;14:2246-2260.
Received 28 June 2018; accepted 18 September 2018 Citation: World Neurosurg. (2019) 121:44-50. https://doi.org/10.1016/j.wneu.2018.09.141 Journal homepage: www.WORLDNEUROSURGERY.org Available online: www.sciencedirect.com 1878-8750/$ - see front matter ª 2018 Elsevier Inc. All rights reserved.
WORLD NEUROSURGERY, https://doi.org/10.1016/j.wneu.2018.09.141
Partial Vertebrae Resection Laterally to Harvest Supplemental Autograft Bone for Anterior Cervical Discectomy and Fusion: A Technical Note and Outcomes Xiaowei Liu, Zhenfang Wu, Gang Liu, Guojing Sun, Zhili Kang, Jianning Zhao, Bin Xu
PURPOSE: To evaluate the safety and effectiveness of partial vertebrae resection laterally through intervertebral space to harvest supplemental autograft bone for anterior cervical discectomy and fusion (ACDF).
-
METHODS: Patients who accepted 1-segment (n [ 19, 38.2 months follow-up) or 2-segment (n [ 17, 40.4 months follow-up) ACDF with supplemental autograft bone were included. Cervical lordosis (CL), segmental lordosis (SL), anterior segment height (ASH), and posterior segment height (PSH) on neutrally lateral radiography, and intervertebral fusion rate on computed tomography were measured. The operation time, intraoperative blood loss, Japanese Orthopedic Association score, visual analog scale around the neck or arm, Neck Disability Index, and complications were also recorded.
-
RESULTS: Mean operation time was 86.2 and 115.6 minutes, and the intraoperative blood loss was 41.7 and 79.4 mL in cases with 1-segment and 2-segment ACDF, respectively. At the final visit, the visual analog scale score and Neck Disability Index significantly decreased, and the Japanese Orthopedic Association score significantly increased. Significant increases were observed in the ASH, PSH, CL, and SL after 2-segment ACDF. Significant increases were observed in the CL and SL after 1-segment ACDF, but not in the ASH and PSH. All the ASH, PSH, CL, and SL kept unchanged at the final visit. All cases acquired definite intervertebral fusion, and the incidence of cage
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Key words Anterior cervical discectomy and fusion - Partial vertebrae resection - Supplemental autograft bone -
Abbreviations and Acronyms ACDF: Anterior cervical discectomy and fusion ASH: Anterior segment height CL: Cervical lordosis CT: Computed tomography JOA: Japanese Orthopedic Association NDI: Neck Disability Index PEEK: Polyetheretherketone PSH: Posterior segment height
subsidence was 5.3% after 1-segment and 17.6% after 2-segment ACDF at the final visit. CONCLUSIONS: Partial vertebrae resection laterally through the intervertebral space was a safe and effective method to harvest supplemental autograft bone for the ACDF.
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INTRODUCTION
F
or patients with symptomatic spinal cord or nerve root compression, sufficient decompression could be usually achieved after anterior cervical discectomy and fusion (ACDF) if there was not ossification of posterior longitudinal ligament, large osteophyte, or huge disc herniation.1,2 Because intervertebral fusion was the key for maintaining long-term outcomes, autogenous bone being harvested from iliac crest was reported to be the gold standard, but its low supporting intensity and high rate of donor morbidity negatively influence the radiologic and clinical outcomes.3-5 Applications of the intervertebral cage and rigid internal fixation system could provide immediate stability and increase the fusion rate, but how to gain sufficiently autologous cancellous bone graft without autograft-harvest associated complications was still controversial.6 Although both allograft and synthetic biological materials with osteogenic, osteoconductive, and osteoinductive characteristics could avoid donor morbidity, insufficient fusion rate and extra financial cost have turned the focus to autograft again.5,7,8 In keeping with previous studies, granular autograft bone being harvested by resection of osteophytes and vertebral chips was
SL: Segmental lordosis VAS: Visual analog scale Department of Orthopaedics, Jinling Hospital, Medicine College, Nanjing University, Nanjing, Jiangsu, China To whom correspondence should be addressed: Bin Xu, M.D. [E-mail: [email protected]] Xiaowei Liu and Zhenfang Wu contributed equally to this article and should be regarded as co-first authors. Citation: World Neurosurg. (2019) 121:44-50. https://doi.org/10.1016/j.wneu.2018.09.141 Journal homepage: www.WORLDNEUROSURGERY.org Available online: www.sciencedirect.com 1878-8750/$ - see front matter ª 2018 Elsevier Inc. All rights reserved.
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Table 1. General Information of the Included Cases 1-Segment Anterior 2-Segment Anterior Cervical Discectomy Cervical Discectomy and Fusion and Fusion Age (years) Gender (male/female, n)
53.6 11.7
56.5 13.6
11/8
12/5
Smoker (n)
5
7
With diabetes mellitus (n)
4
3
Body mass index (kg/m2)
26.5 5.2
24.3 6.6
Cervical spondylotic myelopathy
13
11
Cervical spondylotic radiculopathy
2
3
Cervical spondylotic myelopathy þ cervical spondylotic radiculopathy
4
3
Osteophyte
3
5
Herniated disc
10
7
Osteophyte and disc
6
5
C2/3
0
1
C3/4
2
7
C4/5
5
12
C5/6
9
10
C6/7
3
4
4
4
Diagnosis (n)
Main compressive cause (n)
Decompression level
With anterior osteophyte (n) High signal in spinal cord (n) Follow-up, months (range)
7
7
38.2 15.1 (24e50)
40.4 12.6 (26e47)
or 2-segment ACDF with vertebral chips and supplemental autograft bone that was harvested by partial vertebrae resection for the treatment of cervical spondylotic myelopathy or cervical spondylotic radiculopathy. The exclusion criteria were 1) history of spinal trauma, spinal surgery, or tumor (n ¼ 3); 2) with validated rheumatoid arthritis, ankylosing spondylitis, or spinal infection (n ¼ 1); and 3) with intact radiologic images (n ¼ 2) or lost to follow-up within 12 months postoperatively (n ¼ 1). A total of 36 patients were included in this study and the general information is shown in Table 1. Surgical Approach A right-side Smith-Robinson approach was carried out to expose cervical vertebral bodies and targeted disc after general anesthesia. If anterior osteophyte was lying before the intervertebral space, it was first resected. After removing the intervertebral disc, f anterior chips of the vertebral bodies were then resected for better vision and operation space in all patients. In patients with osteophyte behind the posterior wall of the vertebral bodies, the osteophyte and posterior chips of the vertebral bodies were then resected for sufficient decompression. The posterior longitudinal ligament was resected in all patients. The size of the polyetheretherketone (PEEK [DePuy, Raynham, Massachusett, USA]) cage was decided by model test and intraoperative fluoroscopy, to acquire appropriate restoration of cervical alignment. A schematic diagram of harvesting the maximum volume of the supplement autograft bone by partial vertebrae resection in the procedure of 2-segment ACDF is shown in Figure 1. The
used to fill the cage in our center.9-12 However, the osteophyte was mostly made of cortical bone and it was not suitable for graft fusion. Furthermore, resection of posterior vertebrae chips might not be necessary in patients with mild cervical degeneration or lone disc herniation. So, in patients with ACDF, achievement of cancellous autograft bone was usually insufficient and might be associated with nonfusion postoperatively.13 Inspired by harvesting autograft bone from adjacent lumbar vertebrae, since 2013, we have resected partial vertebrae laterally through intervertebral space and supplemented them to fill the cage if achievement of cancellous bone was insufficient during the ACDF procedure.14 In this study, we report outcomes of this modified technique, to assess its safety and effectiveness.
METHODS Patient Selection Medical records from May 2013 to March 2017 were retrospectively reviewed of 43 patients who accepted 1-segment
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Figure 1. Schematic diagram of partial vertebrae resection. On the coronal view of 2-segment anterior cervical discectomy and fusion (A), gray annuluses were entry points of screws and 4 red frames were probable vertebrae resection zones for maximum harvest of autograft. The resection zone was about 2e3 mm both wide and long, and it should not influence the screw implant. The red frame in (B) shows the depth of vertebrae resection on horizontal view, without involvement of the posterior wall of the vertebrae.
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TECHNICAL NOTE
Figure 2. (A, B) Intraoperative observation of partial vertebra resection through intervertebral space. (C) Bone graft harvesting from vertebra (white arrow) and
resection was carried out just along the interior margin of the right musculus longus coli by a 2-mm rongeur in both sagittal and coronal planes, and the bony groove was then covered by bone wax for hemostasis (Figures 1A and 2A and B). Two bony grooves in 1-level ACDF or 4 in 2-level ACDF could be made for maximum harvest of autograft. To reduce iatrogenic damage of the vertebral end plate integrity, both length and width of the bony groove were just 2e3 mm. Depth of the bony groove could be expanded in the sagittal plane for harvesting more autograft, but the posterior wall of targeted vertebral bodies should not be involved to avoid the risk of spinal cord injury (Figure 1B). After eliminating the osteophyte and visual cortical bone from both supplemental autograft bone and vertebral chips, sufficient cancellous bone was filled into the PEEK cage (Figure 2C). After inserting the PEEK cage into the intervertebral space, a semi-constrained plate (Sky-line [DePuy, USA]) was used for bridging the involved vertebrae. The drainage tube was removed within 24 hours postoperatively. Each patient wore a Philadelphia neck collar for 4e6 weeks and then started to do regular neck exercise.
the polyetheretherketone cage filling with bone from osteophyte and vertebral chips.
Radiologic and Clinical Assessments All our patients received neutrally lateral radiographs preoperatively, and 3 days, 3 months, 6 months, 12 months, and then per year postoperatively. All received computed tomography (CT) 12 months postoperatively. Cervical lordosis (CL) was evaluated by the C2-C7 Cobb angle and segmental lordosis (SL) by fused segment Cobb angle preoperatively, 3 days postoperatively, and at final visit. The distance between the anterior or posterior margins located at the upper end plate of the cephalic vertebrae and lower end plate of the caudal vertebrae on neutrally lateral radiography was defined as the anterior segment height (ASH) or posterior segment height (PSH), respectively. Loss of the CL, SL, ASH, or PSH was calculated as final indexepostoperative index. Segmental subsidence was defined if loss of the ASH or PSH was >2 mm and severe subsidence was confirmed when the loss of ASH or PSH was 3 mm. Intervertebral fusion was defined when there were continuous trabeculae across the interspace on sagittal CT at 12 months postoperatively (Figures 3 and 4). Operation time and intraoperative blood loss were recorded. Neurologic function was evaluated by the Japanese
Figure 3. A 41-year-old female patient with mild cervical degeneration (A) and disc herniation at C6/7 (B). She accepted C6/7 anterior cervical discectomy and fusion with partial vertebra resection at the C7 vertebrae. The sagittal bone-window computed tomography showed definite intervertebral fusion (C) at 13 months postoperatively, and the cross-section computed tomography showed the bony groove at the right side of the C7 vertebra cephalad (D, white arrow).
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Figure 4. A 50-year-old female patient with cord compression at C4/5 and C5/6, with mixed type of ossification of posterior longitudinal ligament from C2-C6 (A, B). She accepted C/5 and C5/6 anterior cervical discectomy and fusion, with partial vertebra resection at the right of C5 both cephalad and caudally. The sagittal bone-window computed tomography showed intervertebral fusion 12 months postoperatively (C). Cross-section computed tomography showed a significant bony cavity (D, white arrow).
Orthopedic Association (JOA) scoring system, and its recovery rate was calculated as (final follow-up JOA scoreepreoperative JOA score)/(17epreoperative JOA score) 100%. Visual analog scale (VAS) score around the neck or arm and Neck Disability Index (NDI) were used to assess the influence of pain on patients’ daily lives. Complications including implant failure, infection, neurologic deterioration, dysphagia, and hoarseness were also recorded. Statistical Analysis PASW Statistics 18.0 (SPSS Inc., Chicago, Illinois, USA) was used to analyze clinical and radiologic results. Intragroup comparison of quantitative data was made by the pairedsamples t test. A P value <0.05 was defined to be statistically significant.
All patients acquired intervertebral fusion, which was verified on bone-window CT 12 months postoperatively. As shown in Table 4, there were losses of the ASH, PSH, CL, and SL at the final visit compared with 3 days postoperatively. Cage subsidence (5.3% and 17.6%), dysphagia (15.8% and 41.2%) and hoarseness (5.3% and 17.6%) were the main
Table 2. Clinical Outcomes in Cases With 1-Segment or 2-Segment Anterior Cervical Discectomy and Fusion 1-Segment Anterior Cervical Discectomy and Fusion
2-Segment Anterior Cervical Discectomy and Fusion
Japanese Orthopedic Association score Preoperative
9.6 4.0
9.3 3.8
RESULTS
Final visit
14.5 2.9
14.1 3.2
The mean operation time was 76.2 17.9 and 95.6 23.4 minutes, and intraoperative blood loss was 41.7 16.5 and 79.4 24.8 mL in patients with 1-segment and 2-segment ACDF, respectively. At the final visit, we found significant increase in the JOA score and decreases in both the VAS score and NDI at the final visit (Table 2). The mean neurologic recovery rate was 65.7% and 63.2% in patients with 1-segment and 2-segment ACDF, respectively.
P value
0.019*
0.001#
Recovery rate (%)
65.7 15.3
63.2 18.4
Compared with preoperative data, there were significant increases in the ASH, PSH, CL, and SL in patients with 2-segment ACDF both 3 days postoperatively and at final visit. In patients with 1-segment ACDF, there were significant increases in both the CL and SL, but only increasing trends in the mean ASH and PSH (Table 3). Although decreasing trends could be observed in the ASH, PSH, CL, and SL in patients with 1-segment or 2segment ACDF, there were no significant differences in these indexes both 3 days postoperatively and at the final visit.
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Visual analog scale score around neck or arm (score) Preoperative
6.3 3.2
6.8 3.7
Final visit
2.3 1.1
2.7 1.6
0#
0#
Preoperative
30.1 9.5
36.4 10.6
Final visit
12.0 4.2
16.7 5.1
0#
0#
P value Neck Disability Index (%)
P value *P value <0.05. #P value <0.001.
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TECHNICAL NOTE
Table 3. Radiologic Outcomes After 1-Segment or 2-Segment Anterior Cervical Discectomy and Fusion 1-Segment Anterior Cervical Discectomy and Fusion
2-Segment Anterior Cervical Discectomy and Fusion
Mean anterior segment height (mm) Preoperatively
31.3 5.5
51.0 5.7
3 days postoperatively
33.5 4.0
55.3 6.0*
Final visit
32.6 4.3
54.1 6.6*
30.5 4.4
Loss of anterior segment height (mm)
0.8 0.3
1.1 0.6
Loss of posterior segment height (mm)
0.5 0.3
0.8 0.5
1.4 0.8
2.7 1.1
0.6 0.2
1.0 0.6
Loss of cervical lordosis ( )
49.7 5.2
Subsidence (n)
1
3
Dysphagia (n)
3
7
3 days postoperatively
32.5 3.8
53.6 5.5y
Final visit
31.9 3.6
53.2 5.2y
Mean cervical lordosis ( )
Hoarseness (n)
1
2
Severe subsidence (n)
0
0
Neurologic deterioration (n)
0
0
Preoperatively
20.6 9.7
21.0 8.8
Implant failure (n)
0
0
3 days postoperatively
26.5 7.1y
28.7 8.6y
Infection (n)
0
0
25.2 7.2y
26.0 6.7y
Final visit
Mean segmental lordosis ( ) Preoperatively
5.2 3.0
8.6 3.7
3 days postoperatively
7.9 2.0*
11.2 2.4y
Final visit
7.3 1.5*
10.3 1.6y
*P < 0.05. yP < 0.001.
complications in patients with 1-segment and 2-segment ACDF, respectively. No patient experienced severe subsidence, neurologic deterioration, implant failure, and infection.
DISCUSSION Autogenous bone was considered to be the gold standard for intervertebral fusion. Autograft has been commonly harvested from the iliac crest since the ACDF was developed in the 1960s, but donor-site complications including infection, persistent pain or paresthesia, and injuries of nerve root and blood vessel resulted in reports by patients of dissatisfaction.15,16 Although application of allograft or synthetic bone materials such as hydroxyapatite, polymethylmethacrylate, b-tricalcium phosphate, biocompatible osteoconductive polymer, and heterologous artificial graft could avoid donor-site morbidity, medical expenses would increase and 2 main problems still remained to be solved.8 First, the fusion rate after the ACDF was similar or even lower with the application of synthetic biological materials compared that with the autograft.8,17 Second, the incidence of radiologic failures, including graft protrusion or settling, disc space collapse, loss of cervical alignment, and delayed fusion or nonunion, was reported to be higher in patients with the synthetic biological materials than those with autograft.8,18
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1-Segment Anterior 2-Segment Anterior Cervical Discectomy Cervical Discectomy and Fusion and Fusion
Loss of segmental lordosis ( )
Mean posterior segment height (mm) Preoperatively
Table 4. Radiologic Index Changes and Complications at the Final Visit
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Because the superiority of the allograft or synthetic bone materials over the autograft in promoting intervertebral fusion was still controversial and the needed volume of bone graft is small because of the application of PEEK cage, Iwasaki et al.19 reported their outcomes of harvesting cancellous bone from the clavicle for filling the cage in 16 patients.8 Although the fusion rate was satisfactory, a risk of subclavian major vessel or lung injury, undeserved clavicle fracture, or local infection might be unavoidable because of the learning curve and growing sample. Harvest of granular bone from osteophyte and vertebral chips was another safe method, but because the osteophyte was a pathologically hypertrophic osteosclerosis and resection of vertebrae chips was unnecessary in patients with mild degeneration, mixture or lone application of the osteophyte might contribute to postoperative nonunion (range, 3%e 9%).2,9,10,20,21 To acquire sufficient cancellous bone within the local operation region was still the key precondition for popularizing ACDF. Because the vertebral body consisted mainly of cancellous bone, it could be an optional source of ideal autograft.2 Cylinder autograft was harvested ventrally from adjacent lumbar vertebrae and the fusion rate could be 100% 28 months postoperatively, but it was unfeasible in the ACDF because of the smaller size of the cervical vertebrae.14 The Williams method of harvesting autograft from adjacent vertebrae and end plate through the intervertebral space was more like corpectomy, but the fusion rate was low (4/7), which was attributed to insufficient intervertebral support and stability.22 In this study, we resected lateral vertebrae through the intervertebral space for maximum preservation of the integrity of anterior supporting structures. Supplemental cancellous bone harvested from the vertebral body was then mixed with vertebral chips to fill the PEEK cage. At the final visit, all patients acquired CT-confirmed fusion, and this rate seemed to be reliable compared with that after stand-alone cage (83.3%),
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TECHNICAL NOTE
anchored cage (87%), or cage-plate system (range, 0%e100%) with application of bone substitutes.8,23 This situation made us believe that partial vertebrae resection could provide sufficient supplemental autograft and a reliable intervertebral fusion rate, but a further case-control or randomized controlled study is needed to provide more information. The cage subsidence, with a range from 19.3% to 42.5%, was associated with progressive neurologic deterioration or alignment deformity, persistent neck pain, or even implant failure after ACDF.24,25 The integrity of the end plate was important for preventing intervertebral collapse, but our method of harvesting supplemental bone might destroy the end plate.22,26 However, because the resection was carried out unilaterally and most of the end plate was still left and kept integral, the main contact surface between the cage and end plate was preserved and the load-bearing area was sufficient. Moreover, immediate stabilization by the screw-plate system and early fusion by sufficient cancellous bone might also contribute to decreasing the incidence of cage subsidence.27 As shown in Tables 2e4, the total incidence of cage subsidence in the 2 groups was just 11.1%, and losses of the CL and SL and decreases in the VAS score and NDI were also comparable to previous studies reported after ACDF.28 All these results made us believe that harvesting autogenous bone by partial vertebrae resection laterally would be a safe supplementary method for ACDF, especially when we could not obtain enough autograft. It was not difficult for an experienced spinal surgeon to harvest autograft from the vertebral body through the intervertebral
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space, and the operation time in 2 groups did not significantly increase compared with previous studies. Intraoperative blood loss was not increased as a result of immediate hemostasis, but only a thin layer of bone wax should be left within the bony groove for maximum reduction of the risk of infection or rejection. To prevent potential injuries of the nerve root and spinal cord, the vertebrae resection should be carried out along the musculus longus coli and without involvement of the posterior wall of the vertebrae. Both satisfactory neurologic recovery and the fact that no patient experienced neurologic deterioration prove the effectiveness of our design (Tables 2 and 4). An increasing trend for occurrence of dysphagia in patients with 2-level ACDF might be attributed to greater involvement of C2/3 and C3/4 and prolonged operation time, but more attention should also be paid to reducing mechanical injury of the musculus longus coli during partial vertebrae resection.29,30 These results prove the safety of this modified method for harvesting supplemental autograft bone. Moreover, the bony groove within the involved vertebrae might provide extra drainage, but the advantage of preventing postoperative hematoma was not evident because of our small sample.
CONCLUSIONS For patients with insufficient autograft bone during ACDF, partial vertebrae resection laterally through the intervertebral space could be an effective and safe method for supplemental bone harvest.
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9. Pitzen T, Kiefer R, Munchen D, Barbier D, Reith W, Steudel WI. Filling a cervical spine cage with local autograft: change of bone density and assessment of bony fusion. Zentralbl Neurochir. 2006;67:8-13.
15. Pollock R, Alcelik I, Bhatia C, Chuter G, Lingutla K, Budithi C, et al. Donor site morbidity following iliac crest bone harvesting for cervical fusion: a comparison between minimally invasive and open techniques. Eur Spine J. 2008;17:845-852.
10. Shad A, Leach JC, Teddy PJ, Cadoux-Hudson TA. Use of the Solis cage and local autologous bone graft for anterior cervical discectomy and fusion: early technical experience. J Neurosurg Spine. 2005; 2:116-122.
16. Fowler BL, Dall BE, Rowe DE. Complications associated with harvesting autogenous iliac bone graft. Am J Orthop (Belle Mead NJ). 1995;24:895-903.
11. Dang L, Sun Y, Wang S, Pan S, Li M, Zhang L, et al. A new source of autograft bone for interbody fusion in anterior cervical discectomy and fusion surgery: experience in 893 cases. Br J Neurosurg. 2017;31:33-38. 12. Park JI, Cho DC, Kim KT, Sung JK. Anterior cervical discectomy and fusion using a stand-alone polyetheretherketone cage packed with local autobone: assessment of bone fusion and subsidence. J Korean Neurosurg Soc. 2013;54:189-193. 13. Yao J, Burns JE, Munoz H, Summers RM. Cortical shell unwrapping for vertebral body abnormality
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17. Miller LE, Block JE. Safety and effectiveness of bone allografts in anterior cervical discectomy and fusion surgery. Spine (Phila Pa 1976). 2011;36: 2045-2050. 18. Shriver MF, Lewis DJ, Kshettry VR, Rosenbaum BP, Benzel EC, Mroz TE. Pseudoarthrosis rates in anterior cervical discectomy and fusion: a meta-analysis. Spine J. 2015;15: 2016-2027. 19. Iwasaki K, Ikedo T, Hashikata H, Toda H. Autologous clavicle bone graft for anterior cervical discectomy and fusion with titanium interbody cage. J Neurosurg Spine. 2014;21:761-768.
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20. Liao JC, Niu CC, Chen WJ, Chen LH. Polyetheretherketone (PEEK) cage filled with cancellous allograft in anterior cervical discectomy and fusion. Int Orthop. 2008;32:643-648. 21. Tabaraee E, Ahn J, Bohl DD, Collins MJ, Massel DH, Aboushaala K, et al. Comparison of surgical outcomes, narcotics utilization, and costs after an anterior cervical discectomy and fusion: stand-alone cage versus anterior plating. Clin Spine Surg. 2017;30:E1201-E1205. 22. McGuire RA, St John K. Comparison of anterior cervical fusions using autogenous bone graft obtained from the cervical vertebrae to the modified Smith-Robinson technique. J Spinal Disord. 1994;7: 499-503. 23. Lee YS, Kim YB, Park SW. Does a zero-profile anchored cage offer additional stabilization as anterior cervical plate? Spine (Phila Pa 1976). 2015; 40:E563-E570. 24. Chen Y, Chen D, Guo Y, Wang X, Lu X, He Z, et al. Subsidence of titanium mesh cage: a study
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based on 300 cases. J Spinal Disord Tech. 2008;21: 489-492. 25. Karikari IO, Jain D, Owens TR, Gottfried O, Hodges TR, Nimjee SM, et al. Impact of subsidence on clinical outcomes and radiographic fusion rates in anterior cervical discectomy and fusion: a systematic review. J Spinal Disord Tech. 2014;27:1-10. 26. Cheng CC, Ordway NR, Zhang X, Lu YM, Fang H, Fayyazi AH. Loss of cervical endplate integrity following minimal surface preparation. Spine (Phila Pa 1976). 2007;32:1852-1855. 27. Lee CH, Hyun SJ, Kim MJ, Yeom JS, Kim WH, Kim KJ, et al. Comparative analysis of 3 different construct systems for single-level anterior cervical discectomy and fusion: stand-alone cage, iliac graft plus plate augmentation, and cage plus plating. J Spinal Disord Tech. 2013;26:112-118. 28. Nambiar M, Phan K, Cunningham JE, Yang Y, Turner PL, Mobbs R. Locking stand-alone cages versus anterior plate constructs in single-level
fusion for degenerative cervical disease: a systematic review and meta-analysis. Eur Spine J. 2017; 26:2258-2266. 29. Simoes J, Romao J, Cunha A, Paiva S, Migueis A. Neck pain and acute dysphagia. Dysphagia. 2017; 32:123-125. 30. Joaquim AF, Murar J, Savage JW, Patel AA. Dysphagia after anterior cervical spine surgery: a systematic review of potential preventative measures. Spine J. 2014;14:2246-2260.
Received 28 June 2018; accepted 18 September 2018 Citation: World Neurosurg. (2019) 121:44-50. https://doi.org/10.1016/j.wneu.2018.09.141 Journal homepage: www.WORLDNEUROSURGERY.org Available online: www.sciencedirect.com 1878-8750/$ - see front matter ª 2018 Elsevier Inc. All rights reserved.
WORLD NEUROSURGERY, https://doi.org/10.1016/j.wneu.2018.09.141