Adding a posterior cervical fusion can increase the rate of successful anterior cervi- cal fusion when a multilevel anterior cervical procedure is performed. The poten- tial advantages of additional posterior fusion include greater construct stability and larger surface area for fusion.
For patients with symptomatic pseudoarthrosis following an anterior cervical fusion, posterior fusion leads to a high rate of success while avoiding the previous surgical site.24 In a retrospective study, a concomitant posterior approach has also been shown to increase fusion rates in multilevel cervical fusion procedures; how- ever, it is technically demanding and leads to longer operating times and increased blood loss.25
Despite the increased rate of fusion success, the addition of posterior cervical fusion is not advocated for most patients undergoing multilevel ACDF. It is recom- mended that posterior cervical fusion be used in patients with traumatic conditions that have resulted in disruption of the posterior ligamentous complex and in patients who have significant dorsal compression requiring additional posterior decompres- sion. The preferred practice is also to treat all symptomatic pseudoarthroses of previ- ous anterior cervical fusions with posterior cervical fusion.
When posterior fusion is added, the use of lateral mass instrumentation with pos- terior iliac crest autograft or allograft bone is recommended. Spinous process wiring can be added at the discretion of the surgeon.
COMMENTARY
There are many bone grafting options for multilevel anterior cervical arthrodesis. In making choices the surgeon should keep in mind a balance among known efficacy, risks, and cost. The choice of bone graft substitutes should be individualized and also based on patient factors (e.g., smoking, steroid or chemotherapy exposure, diabetes) that can impede bone healing. For multilevel fusions in patients with potential impaired healing due to host factors, one must consider the addition of a posterior fusion or use of one of the more potent osteoinductive bone graft substitutes.
REFERENCES
1. Hillard VH, Apfelbaum RI: Surgical management of cervical myelopathy: indications and techniques for multilevel cervical discectomy, Spine J 6:242S–251S, 2006.
2. Bishop RC, Moore KA, Hadley MN: Anterior cervical interbody fusion using autogeneic and alloge- neic bone graft substrate: a prospective comparative analysis, J Neurosurg 85:206–210, 1996.
3. Bohlman H, Emery S, Goodfellow D, et al: Robinson anterior cervical discectomy and arthrodesis for cervical radiculopathy, J Bone Joint Surg Am 75:1298–1307, 1993. This retrospective study evaluated the results of using the Robinson method of ACDF with placement of autogenous iliac crest bone grafts at one to four levels in 122 patients who had cervical radiculopathy. A one-level procedure was per- formed in 62 of the 122 patients; a two-level procedure in 48; a three-level procedure in 11; and a four- level procedure in 1. The average duration of clinical and radiographic follow-up was 6 years (range, 2 to 15 years). The average age was 50 years (range, 25 to 78 years). Lateral radiographs of the cervical spine, made in flexion and extension, showed a pseudoarthrosis at 24 of 195 operatively treated seg- ments. The risk of pseudoarthrosis was significantly greater after a multilevel arthrodesis than after a single-level arthrodesis (P < .01). The results of this study suggest that the Robinson ACDF with an autogenous iliac crest bone graft for cervical radiculopathy is a safe procedure that can relieve pain and lead to resolution of neurologic deficits in a high percentage of patients. However, as the number of fusion levels increases, so does the risk of pseudoarthrosis.
4. Hilibrand AS, Fye MA, Emery SE, et al: Increased rate of arthrodesis with strut grafting after multilevel anterior cervical decompression, Spine 27:146–151, 2002.
5. Wang JC, McDonough PW, Kanim LE, et al: Increased fusion rates with cervical plating for three- level anterior cervical discectomy and fusion, Spine 26:643–647, 2001. This retrospective review looked at patients surgically treated by a single surgeon with a three-level ACDF with and without anterior plate fixation. The primary purpose of this study was to compare the clinical and radiographic success of anterior three-level diskectomy and fusion performed with and without anterior cervical plate fixation. After previous studies of multilevel cervical diskectomies and fusions had shown that
fusion rates decrease as the number of surgical levels increases, this study assessed whether the addi- tion of anterior cervical plate stabilization can provide more stability and potentially increase fusion rates for multilevel fusions. Fifty-nine patients were treated surgically with a three-level ACDF by the senior author over 7 years. Cervical plates were used in 40 patients, whereas 19 underwent fusions with no plates. The fusion rates were improved with the use of a cervical plate. Patients treated with cervical plating had overall better results compared with those treated without cervical plates. Accord- ing to the authors, although the use of cervical plates decreased the pseudoarthrosis rate, a three-level procedure was still associated with a high rate of nonunion, and other strategies to increase fusion rates should be explored.
6. Samartzis D, Shen F, Matthews D, et al: Comparison of allograft to autograft in multilevel anterior cervical discectomy and fusion with rigid plate fixation, Spine J 3:451–459, 2003. The purpose of this retrospective radiographic and clinical review was to determine the efficacy of allograft versus auto- graft with regard to fusion rate and clinical outcome in patients undergoing two- and three-level ACDF with rigid anterior plate fixation. Fusion rate and postoperative clinical outcome were assessed in 80 patients. Seventy-eight patients (97.5%) achieved solid arthrodesis. Pseudoarthrosis occurred in two patients who received allografts for two-level and three-level fusions. Nonsegmental screws were used in the two-level nonunion case. The authors reported that a high fusion rate of 97.5% was obtained for multilevel ACDF with rigid plating with either autograft or allograft.
7. Emery SE, Fisher JR, Bohlman HH: Three-level anterior cervical discectomy and fusion: radiographic and clinical results, Spine 22:2622–2624, 1997. This study is a retrospective review of 16 patients who underwent the modified Robinson ACDF at three operative levels. The purpose of this study was to pro- vide long-term follow-up data on the surgical success and patient outcome of three-level anterior cervi- cal diskectomies and fusions using autograft bone. The critical finding of this study is that the success of arthrodesis for anterior cervical fusion depends on several factors, including the number of surgical levels.
This was also the first study to provide long-term follow-up on arthrodesis rate and outcomes for patients who specifically underwent three-level diskectomy and fusion procedures In this study, only 9 (56%) of the 16 patients went on to achieve solid arthrodesis at all three levels. Of the seven patients with pseu- doarthrosis, two had severe pain and required revision; two had moderate pain; and three no pain. The conclusion of this study was that a three-level modified Robinson cervical diskectomy and fusion results in an unacceptably high rate of pseudoarthrosis. Although not all pseudoarthroses are painful, the data suggested that those with a successful fusion have a better outcome. The authors recommended that these patients undergo additional or alternative measures to achieve arthrodesis consistently.
8. Nirala AP, Husain M, Vatsal DK: A retrospective study of multiple interbody grafting and long seg- ment strut grafting following multilevel anterior cervical decompression, Br J Neurosurg 18:227–232, 2004.
9. Bolesta MJ, Rechtine GR, Chrin AM: Three- and four-level anterior cervical discectomy and fusion with plate fixation: a prospective study, Spine 25:2040–2044, 2000.
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13. DiAngelo DJ, Foley KT, Vossel KA, et al: Anterior cervical plate reverses load transfer through multi- level strut-grafts, Spine 25:783–795, 2000.
14. Wang JC, McDonough PW, Endow KK, et al: Increased fusion rates with cervical plating for two-level anterior cervical discectomy and fusion, Spine 25:41–45, 2000.
15. Anderson DG, Albert TJ: Bone grafting, implants, and plating options for anterior cervical fusions, Orthop Clin N Am 33:317–328, 2002.
16. Shapiro S: Banked fibula and the locking anterior cervical plate in anterior cervical fusions following cervical discectomy, J Neurosurg 84:161–165, 1996.
17. Wilke HJ, Kettler A, Goetz C, et al: Subsidence resulting from simulated postoperative neck move- ments: an in vitro investigation with a new cervical fusion cage, Spine 25:2762–2770, 2000.
18. Vavruch L, Hedlund R, Javid D: A prospective randomized comparison between the Cloward pro- cedure and a carbon fiber cage in the cervical spine: a clinical and radiologic study, Spine 27:
1694–1701, 2002.
19. Hee HT, Kudnani V: Rationale for use of polyetheretherketone polymer interbody cage device in cervical spine surgery, Spine J 10:66–69, 2010.
20. Baskin DS, Ryan P, Sonntag V, et al: A prospective, randomized, controlled cervical fusion study using recombinant human bone morphogenetic protein-2 with the CORNERSTONE-SR allograft ring and ATLANTIS anterior cervical plate, Spine 28:1219–1225, 2003.
21. Shen H, Buchowski J, Yeom J, et al: Pseudoarthrosis in multilevel anterior cervical fusion with rhBMP-2 and allograft: analysis of one hundred twenty-seven cases with minimum two-year follow-up, Spine 35:747–753, 2010. This consecutive case series analyzed the pseudoarthrosis rate after rhBMP-2–augmented multilevel (three or more levels) anterior cervical fusion. Data for a large number of patients with cervical spondylosis and/or disk herniation who underwent anterior cervical fusion with rhBMP-2, structural allograft, and plate fixation and had a minimum of 2 years of follow- up were examined by experienced, independent spine surgeons. A total of 127 patients, 54 men and 73 women with a mean age of 54 ± 10 years (range, 32 to 79 years), were included. Seventy-five patients (59.1%) underwent a three-level fusion, 34 (26.7%) underwent a four-level fusion, and 18 (14.2%)
underwent a five-level fusion. Of the 451 fusion segments, 14 segments (3.1%) in 13 of 127 patients (10.2%) had evidence of pseudoarthrosis 6 months after surgery. The only statistically significant risk factor for developing a pseudoarthrosis was the number of fusion levels. In this large series of rhBMP- 2–augmented multilevel fusions, the pseudoarthrosis rate was 10.2% at 6 months after surgery. The authors concluded that since the risk of pseudoarthrosis increases with the number of fusion levels, a long fusion lever arm may biomechanically overwhelm the biologic advantage of rhBMP-2 treatment.
Although rhBMP-2 is known to enhance fusion rates, it does not guarantee fusion in all situations.
22. Shields LB, Raque GH, Glassman SD, et al: Adverse effects associated with high-dose recombinant human bone morphogenetic protein-2 use in anterior cervical spine fusion, Spine 31:542–547, 2006.
23. Smucker JD, Rhee JM, Singh K, et al: Increased swelling complications associated with off-label usage of rhBMP-2 in the anterior cervical spine, Spine 31:2813–2819, 2006.
24. Brodsky AE, Khalil MA, Sassard WR, et al: Repair of symptomatic pseudoarthrosis of anterior cervical fusion: posterior versus anterior repair, Spine 17:1137–1143, 1992.
25. Sembrano J, Mehbod A, Garvey T, et al: A concomitant posterior approach improves fusion rates but not overall reoperation rates in multilevel cervical fusion for spondylosis, J Spin Disord 22:162–169, 2009.
This retrospective comparative study of two approaches to multilevel fusion for cervical spondylosis in patients treated at a single institution was carried out to provide justification for a concomitant poste- rior approach in multilevel cervical fusion for spondylosis by demonstrating decreased pseudoarthrosis and reoperation rates. Seventy-eight consecutively treated patients who underwent multilevel cervical fusion at a single institution and for whom a minimum of 2 years of follow-up data were available were divided into an anterior-only group (n = 55) and an anteroposterior (AP) group (n = 23). Results showed a significant difference between the two groups in pseudoarthrosis rates (anterior, 38% vs. AP, 0%; P < .001) and rates of reoperation for pseudoarthrosis (anterior, 22% vs. AP, 0%; P = .01). There were no differ- ences in overall reoperation rates (anterior, 36% vs. AP, 30%; P = .62) and in early reoperation rates (ante- rior, 15% vs. AP, 26%; P = .13), but the rate of late reoperations was increased in the anterior-only group (anterior, 24% vs. AP, 4%; P = .043). A concomitant posterior fusion significantly reduced the incidence of pseudoarthrosis (0% vs. 38%) and pseudoarthrosis-related reoperations (0% vs. 22%) compared with traditional anterior-only fusion. However, this did not translate into a difference in overall reoperation rates.
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