- Email: [email protected]
C1-C2 Fusion: Promoting Stability, Reducing Morbidity
Perspectives Commentary on: The Use of Allograft and Recombinant Human Bone Morphogenetic Protein for Instrumented Atlantoaxial Fusions by Hood et al. World Neurosurg 2014 http://dx.doi.org/10.1016/j.wneu.2013.01.083
Edward C. Benzel, M.D. Professor of Surgery, Cleveland Clinic Lerner College of Medicine of Case Western Reserve University Chairman, Department of Neurosurgery Co-Director, Spine Surgery Fellowship Program, Cleveland Clinic
C1-C2 Fusion: Promoting Stability, Reducing Morbidity Daniel Lubelski and Edward C. Benzel
T
he surgical treatment of atlantoaxial instability has been evolving for more than 100 years. The first report was a case presentation in 1910, by Mixter and Osgood (30), who described using heavy silk thread to secure the posterior arch of the atlas to the spinous process of the axis. The next few decades were associated with multiple advances, including approaches using dorsal cervical wiring techniques. These included the Gallie technique (13, 16, 27), the Brooks-Jenkins technique (5), and the technique of Dickman and Sonntag (9) and Dickman et al. (10). Nonwiring techniques included interlaminar clamps (21), the Magerl transarticular screw technique (26), plate and screw techniques (17, 18), rod-cantilever techniques (19, 33, 40), translaminar screw techniques (25, 42, 43), and a variety of other strategies (28, 32). Although the approaches and indications vary, the fusion rates for these procedures have been observed to be as high as 90%e100% (2, 9, 12, 28). In recent decades there has been an increasing trend toward C1-C2 fusion for atlantoaxial instability, as opposed to the use of external immobilization alone. High nonunion rates were observed after the application of external immobilization alone (28). Accordingly, there has been a push toward a further improvement in the rate of fusion and the time-to-fusion after these procedures. In addition to the surgical approach or instrumentation type used, a major contributor to successful fusion is the bone graft substrate used. Iliac crest bone graft (ICBG) is considered to be the gold standard substrate for spinal fusion. It is osteoconductive (provides scaffold matrix for bone growth), osteogenic (contains osteoblasts and mesenchymal stem cells that promote new bone formation), and osteoinductive (harbors growth factors, such as bone
Key words Atlantoaxial allograft - Cervical - Fusion - rh-BMP2 -
Abbreviations and Acronyms ICBG: Iliac crest bone graft rhBMP-2: Recombinant human bone morphogenetic protein-2
WORLD NEUROSURGERY 00 (0): ---, MONTH 2014
morphogenetic protein, that recruit and induce osteogenic cell activity). Despite the characteristics that make ICBG biologically ideal as a fusion source, harvesting the autograft is associated with substantial complications and morbidity (1, 6, 11, 24). Studies have shown that 45%e60% of patients complain of pain at the donor site 1e2 years after surgery (23, 31, 34, 35, 39). Robertson and Wray (36) observed that 35% of patients experienced major and minor complications (e.g., infection, arterial and nerve injury) after iliac crest harvest, and Kim et al. (24) found that 16.5% of patients believed that the harvest site pain was worse than the pain from the primary surgical site. Alternatives to ICBG have been suggested, including autograft harvested from other sites such as calvaria and rib. Bone graft harvest from these sites has been shown to be associated with fewer complications, to be a simpler technique, and to be associated with comparable fusion rates (29, 36, 37). All autograft options, however, are associated with harvest-related pain and complications. To obviate the need for a graft harvesting procedure, various allograft bone graft substitutes and/or extenders have been developed. The use of allografts eliminates graft harvest morbidity, shortens hospital stay, shortens operative time, and decreases surgical costs. In contrast to the biological properties of ICBG, however, allograft only provides an osteoconductive matrix without the osteogenic and osteoinductive advantages observed with autograft. Accordingly, various fusion extenders with osteoinductive properties have been investigated to enhance the ability of allograft to achieve fusion. These include demineralized bone matrix, b-tricalcium phosphate, calcium sulfate/hydroxyapatite, and recombinant human bone morphogenetic protein-2 (rhBMP-2) (1).
Department of Neurosurgery, Cleveland Clinic, Cleveland, Ohio, and Lerner College of Medicine, Case Western Reserve University, Cleveland, Ohio, USA To whom correspondence should be addressed: Edward C. Benzel, M.D. [E-mail: [email protected]] Citation: World Neurosurg. (2014). http://dx.doi.org/10.1016/j.wneu.2013.02.077
www.WORLDNEUROSURGERY.org
1
PERSPECTIVES
Recently, substantial controversy regarding the use of rhBMP-2 in spine surgery has emerged. High complication rates, particularly with the off-label use in the cervical spine, have been observed. This includes ectopic bone formation, bone resorption, swelling, seroma formation, hematoma, dysphagia, and breathing difficulties (4, 7, 31, 38). On the other hand, rhBMP-2 has also been shown to effectively stimulate bone growth and reduce nonunion (3). It remains to be proven that rhBMP-2 can be effectively used alongside allograft to provide sufficient osteoinduction to promote bone fusion, without a significant risk of complications. In this issue of WORLD NEUROSURGERY, the study by Hood et al. (22) addresses the latter question by addressing the dose of rhBMP-2 used. In the largest retrospective series on the topic, they present 52 patients who underwent atlantoaxial fusion with low dose (average, 4.5 mg; range, 2.2e12 mg) rhBMP-2 for C1-C2 instability. For the 50 patients that had sufficient follow-up (average, 23.9 months), they found that 100% of patients achieved fusion, and that none had complications directly attributable to the rhBMP-2. These preliminary findings are promising, in that the surgery provides the potential for improved fusion rates with the use of allograft, yet avoiding the morbidity associated with autograft harvest. This strategy also shortens operative time and is associated with less blood loss that was observed with autograft harvest. The optimal graft substrate is yet to be defined. The preliminary results reported by Hood et al. (22) are promising, but the limitations of this approach are well recognized. As they acknowledged, their study is retrospective, involves varying doses of rhBMP-2, and different surgical techniques used by the two participating institutions involved in their study. The study also lacks a control population who did not receive rhBMP-2. Hence, the true contribution of rhBMP-2 to fusion outcome is difficult to ascertain. In a relevant study of atlantoaxial fusion, Hillard et al. (20) compared 47 patients who underwent C1-C2 arthrodesis with allograft and in 42 patients who underwent C1-2 arthrodesis with autograft. They found no significant differences between the two groups, with 97% of patients in the autograft group achieving
REFERENCES 1. Abdullah KG, Steinmetz MP, Benzel EC, Mroz TE: The state of lumbar fusion extenders. Spine 36: E1328-E1334, 2011. 2. Aryan HE, Newman CB, Nottmeier EW, Acosta FL Jr, Wang VY, Ames CP: Stabilization of the atlantoaxial complex via C-1 lateral mass and C-2 pedicle screw fixation in a multicenter clinical experience in 102 patients: modification of the Harms and Goel techniques. J Neurosurg Spine 8: 222-229, 2008. 3. Baskin DS, Ryan P, Sonntag V, Westmark R, Widmayer MA: A prospective, randomized, controlled cervical fusion study using recombinant human bone morphogenetic protein-2 with the CORNERSTONE-SR allograft ring and the ATLANTIS anterior cervical plate. Spine 28: 1219-1224, 2003.
2
www.SCIENCEDIRECT.com
fusion at 24 months postoperatively, compared with 89% with allograft. At the final follow-up, this nonsignificant difference was even smaller with 97% in the autograft group and 92% in the allograft group showing solid fusion. Similar results were found by Elliott et al. (12) in their systematic review of the literature. They identified 13 studies reporting on 652 patients who underwent C1-C2 dorsal instrumented arthrodesis with iliac crest autograft, and 7 studies with 60 patients who underwent C1-C2 dorsal instrumented arthrodesis with cadaveric allograft. They found no significant differences between the two groups regarding complications, mortality, or fusion rates—with a 99.7% fusion rate in the autograft group and a 100% fusion rate in the allograft group. The studies by Hillard et al. (20), Elliott et al. (12), and Hood et al. (22) emphasized their observation regarding the importance of surgical technique in promoting fusion. Specifically, packing the C1-2 joint with allograft material and incorporating the graft under compression, promotes fusion. Although some surgeons prefer to use on-lay allograft, this may be a relative disadvantage and deter fusion. In contrast, by taking advantage of load sharing and compressive forces, as originally described by Wolff’s law (8, 14, 15, 41), packing the C1-2 joint with allograft can lead to high fusion rates and superior outcomes. The study by Hood et al. (22) is the largest series reporting dorsal C1-C2 surgery with allograft and identifies the fusion rate, dose of rhBMP-2 needed for fusion, and the postoperative outcomes. These data provide the foundation for future well-designed prospective clinical trials that will most certainly include validated outcome measures to assess complications, fusion rates, and quality of life, as well as cost. The comparative effectiveness of allograft versus autograft, the relative advantages and disadvantages of the various available surgical techniques, and the impact of packing versus on-lay of the graft material for atlantoaxial fusion must all be addressed. Furthermore, it will become increasingly important for us all to understand the comparative and cost effectiveness of the various bone graft extenders including rhBMP-2. By reporting their institutional experience, Hood et al. (22) have contributed to, and advanced, the understanding of rhBMP-2, unique allograft applications, and atlantoaxial fusion techniques.
4. Benglis D, Wang MY, Levi AD: A comprehensive review of the safety profile of bone morphogenetic protein in spine surgery. Neurosurgery 62: ONS423-ONS431, 2008. 5. Brooks AL, Jenkins EB: Atlanto-axial arthrodesis by the wedge compression method. Am J Bone Joint Surg 60:279-284, 1978. 6. Carragee EJ, Bono CM, Scuderi GJ: Pseudomorbidity in iliac crest bone graft harvesting: the rise of rhBMP-2 in short-segment posterior lumbar fusion. Spine 9:873-879, 2009. 7. Center for Devices and Radiological Health. Public Health Notifications (Medical Devices)—FDA Public Health Notification: Life-threatening Complications Associated with Recombinant Human Bone Morphogenetic Protein in Cervical Spine Fusion. Silver Spring, MD: US Department of Health and Human Services, US Food and Drug Administration; 2008.
8. Chen J-H, Liu C, You L, Simmons CA: Boning up on Wolff’s law: mechanical regulation of the cells that make and maintain bone. J Biomech 43: 108-118, 2010. 9. Dickman CA, Sonntag VK: Posterior C1-C2 transarticular screw fixation for atlantoaxial arthrodesis. Neurosurgery 43:275-280, 1998. 10. Dickman CA, Sonntag VK, Papadopoulos SM, Hadley MN: The interspinous method of posterior atlantoaxial arthrodesis. J Neurosurg 74:190-198, 1991. 11. Dimar JR 2nd, Glassman SD, Burkus JK, Pryor PW, Hardacker JW, Carreon LY: Two-year fusion and clinical outcomes in 224 patients treated with a single-level instrumented posterolateral fusion with iliac crest bone graft. Spine 9: 880-885, 2009.
WORLD NEUROSURGERY, http://dx.doi.org/10.1016/j.wneu.2013.02.077
PERSPECTIVES
12. Elliott RE, Morsi A, Frempong-Boadu A, Smith ML: Is allograft sufficient for posterior atlantoaxial instrumented fusions with screw and rod constructs? A structured review of literature. World Neurosurg 78:326-338, 2012. 13. Fielding JW, Hawkins RJ, Ratzan SA: Spine fusion for atlanto-axial instability. Am J Bone Joint Surg 58:400-407, 1976. 14. Frost HM: Wolff’s law and bone’s structural adaptations to mechanical usage: an overview for clinicians. Angle Orthodont 64:175-188, 1994. 15. Frost HM A: 2003 update of bone physiology and Wolff’s law for clinicians. Angle Orthodont 74: 3-15, 2004. 16. Gallie W: Fractures and dislocations of the cervical spine. Am J Surg 16:495-499, 1939. 17. Goel A, Desai KI, Muzumdar DP: Atlantoaxial fixation using plate and screw method: a report of 160 treated patients. Neurosurgery 51:1351-1356, 2002. 18. Goel A, Laheri V: Plate and screw fixation for atlanto-axial subluxation. Acta Neurochirurg 129: 47-53, 1994. 19. Harms J, Melcher RP: Posterior C1-C2 fusion with polyaxial screw and rod fixation. Spine 26: 2467-2471, 2001. 20. Hillard VH, Fassett DR, Finn MA, Apfelbaum RI: Use of allograft bone for posterior C1-2 fusion. J Neurosurg Spine 11:396-401, 2009. 21. Holness RO, Huestis WS, Howes WJ, Langille RA: Posterior stabilization with an interlaminar clamp in cervical injuries: technical note and review of the long term experience with the method. Neurosurgery 14:318-322, 1984. 22. Hood B, Hamilton DK, Smith JS, Dididze M, Shaffrey C, Levi AD: The use of allograft and recombinant human bone morphogenetic protein for instrumented atlantoaxial fusions. World Neurosurg 2013 Jan 19 [Epub ahead of print]. 23. Hsu WK, Wang JC: The use of bone morphogenetic protein in spine fusion. Spine J 8:419-425, 2008.
24. Kim DH, Rhim R, Li L, Martha J, Swaim BH, Banco RJ, Jenis LG, Tromanhauser SG: Prospective study of iliac crest bone graft harvest site pain and morbidity. Spine J 9:886-892, 2009.
36. Robertson PA, Wray AC: Natural history of posterior iliac crest bone graft donation for spinal surgery: a prospective analysis of morbidity. Spine 26:1473-1476, 2001.
25. Leonard JR, Wright NM: Pediatric atlantoaxial fixation with bilateral, crossing C-2 translaminar screws. Technical note. J Neurosurg 104:59-63, 2006.
37. Sawin PD, Traynelis VC, Menezes AH: A comparative analysis of fusion rates and donorsite morbidity for autogeneic rib and iliac crest bone grafts in posterior cervical fusions. J Neurosurg 88:255-265, 1998.
26. Magerl F, Seemann P: Stable posterior fusion of the atlas and axis by transarticular screw fixation. In: Kehr P, Wiedner A, eds. Cervical spine. New York: Springer-Verlag; 1986:322-327. 27. McGraw RW, Rusch RM: Atlanto-axial arthrodesis. Br J Bone Joint Surgery 55:482-489, 1973. 28. Menendez JA, Wright NM: Techniques of posterior C1-C2 stabilization. Neurosurgery 60: S103-S111, 2007. 29. Menezes AH: Atlantoaxial arthrodesis with autograft versus allograft. World Neurosurg 78: 239-240, 2012. 30. Mixter SJ, Osgood RB: IV. Traumatic lesions of the atlas and axis. Ann Surg 51:193-207, 1910. 31. Mroz TE, Wang JC, Hashimoto R, Norvell DC: Complications related to osteobiologics use in spine surgery: a systematic review. Spine 35: S86-S104, 2010. 32. Mummaneni PV, Haid RW: Atlantoaxial fixation: overview of all techniques. Neurology India 53: 408-415, 2005. 33. Resnick DK, Benzel EC: C1-C2 pedicle screw fixation with rigid cantilever beam construct: case report and technical note. Neurosurgery 50: 426-428, 2002. 34. Rihn JA, Kirkpatrick K, Albert TJ: Graft options in posterolateral and posterior interbody lumbar fusion. Spine 35:1629-1639, 2010.
38. Shields LBE, Raque GH, Glassman SD, Campbell M, Vitaz T, Harpring J, Shields CB: Adverse effects associated with high-dose recombinant human bone morphogenetic protein-2 use in anterior cervical spine fusion. Spine 31:542-547, 2006. 39. Silber JS, Anderson DG, Daffner SD, Brislin BT, Leland JM, Hilibrand AS, Vaccaro AR, Albert TJ: Donor site morbidity after anterior iliac crest bone harvest for single-level anterior cervical discectomy and fusion. Spine 28:134-139, 2003. 40. Stokes JK, Villavicencio AT, Liu PC, Bray RS, Johnson JP: Posterior atlantoaxial stabilization: new alternative to C1-2 transarticular screws. Neurosurg Focus 12:E6, 2002. 41. Wolff J: Das Gesetz der Transformation der Knochen. Berlin: A Hirschwald; 1982. 42. Wright NM: Posterior C2 fixation using bilateral, crossing C2 laminar screws: case series and technical note. J Spinal Dis Techn 17:158-162, 2004. 43. Wright NM: Translaminar rigid screw fixation of the axis. Technical note. J Neurosurg Spine 3: 409-414, 2005.
Citation: World Neurosurg. (2014). http://dx.doi.org/10.1016/j.wneu.2013.02.077 Journal homepage: www.WORLDNEUROSURGERY.org Available online: www.sciencedirect.com
35. Robertson SC, Menezes AH: Occipital calvarial bone graft in posterior occipitocervical fusion. Spine 23:249-254, 1998.
WORLD NEUROSURGERY 00 (0): ---, MONTH 2014
1878-8750/$ - see front matter ª 2014 Elsevier Inc. All rights reserved.
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3
Edward C. Benzel, M.D. Professor of Surgery, Cleveland Clinic Lerner College of Medicine of Case Western Reserve University Chairman, Department of Neurosurgery Co-Director, Spine Surgery Fellowship Program, Cleveland Clinic
C1-C2 Fusion: Promoting Stability, Reducing Morbidity Daniel Lubelski and Edward C. Benzel
T
he surgical treatment of atlantoaxial instability has been evolving for more than 100 years. The first report was a case presentation in 1910, by Mixter and Osgood (30), who described using heavy silk thread to secure the posterior arch of the atlas to the spinous process of the axis. The next few decades were associated with multiple advances, including approaches using dorsal cervical wiring techniques. These included the Gallie technique (13, 16, 27), the Brooks-Jenkins technique (5), and the technique of Dickman and Sonntag (9) and Dickman et al. (10). Nonwiring techniques included interlaminar clamps (21), the Magerl transarticular screw technique (26), plate and screw techniques (17, 18), rod-cantilever techniques (19, 33, 40), translaminar screw techniques (25, 42, 43), and a variety of other strategies (28, 32). Although the approaches and indications vary, the fusion rates for these procedures have been observed to be as high as 90%e100% (2, 9, 12, 28). In recent decades there has been an increasing trend toward C1-C2 fusion for atlantoaxial instability, as opposed to the use of external immobilization alone. High nonunion rates were observed after the application of external immobilization alone (28). Accordingly, there has been a push toward a further improvement in the rate of fusion and the time-to-fusion after these procedures. In addition to the surgical approach or instrumentation type used, a major contributor to successful fusion is the bone graft substrate used. Iliac crest bone graft (ICBG) is considered to be the gold standard substrate for spinal fusion. It is osteoconductive (provides scaffold matrix for bone growth), osteogenic (contains osteoblasts and mesenchymal stem cells that promote new bone formation), and osteoinductive (harbors growth factors, such as bone
Key words Atlantoaxial allograft - Cervical - Fusion - rh-BMP2 -
Abbreviations and Acronyms ICBG: Iliac crest bone graft rhBMP-2: Recombinant human bone morphogenetic protein-2
WORLD NEUROSURGERY 00 (0): ---, MONTH 2014
morphogenetic protein, that recruit and induce osteogenic cell activity). Despite the characteristics that make ICBG biologically ideal as a fusion source, harvesting the autograft is associated with substantial complications and morbidity (1, 6, 11, 24). Studies have shown that 45%e60% of patients complain of pain at the donor site 1e2 years after surgery (23, 31, 34, 35, 39). Robertson and Wray (36) observed that 35% of patients experienced major and minor complications (e.g., infection, arterial and nerve injury) after iliac crest harvest, and Kim et al. (24) found that 16.5% of patients believed that the harvest site pain was worse than the pain from the primary surgical site. Alternatives to ICBG have been suggested, including autograft harvested from other sites such as calvaria and rib. Bone graft harvest from these sites has been shown to be associated with fewer complications, to be a simpler technique, and to be associated with comparable fusion rates (29, 36, 37). All autograft options, however, are associated with harvest-related pain and complications. To obviate the need for a graft harvesting procedure, various allograft bone graft substitutes and/or extenders have been developed. The use of allografts eliminates graft harvest morbidity, shortens hospital stay, shortens operative time, and decreases surgical costs. In contrast to the biological properties of ICBG, however, allograft only provides an osteoconductive matrix without the osteogenic and osteoinductive advantages observed with autograft. Accordingly, various fusion extenders with osteoinductive properties have been investigated to enhance the ability of allograft to achieve fusion. These include demineralized bone matrix, b-tricalcium phosphate, calcium sulfate/hydroxyapatite, and recombinant human bone morphogenetic protein-2 (rhBMP-2) (1).
Department of Neurosurgery, Cleveland Clinic, Cleveland, Ohio, and Lerner College of Medicine, Case Western Reserve University, Cleveland, Ohio, USA To whom correspondence should be addressed: Edward C. Benzel, M.D. [E-mail: [email protected]] Citation: World Neurosurg. (2014). http://dx.doi.org/10.1016/j.wneu.2013.02.077
www.WORLDNEUROSURGERY.org
1
PERSPECTIVES
Recently, substantial controversy regarding the use of rhBMP-2 in spine surgery has emerged. High complication rates, particularly with the off-label use in the cervical spine, have been observed. This includes ectopic bone formation, bone resorption, swelling, seroma formation, hematoma, dysphagia, and breathing difficulties (4, 7, 31, 38). On the other hand, rhBMP-2 has also been shown to effectively stimulate bone growth and reduce nonunion (3). It remains to be proven that rhBMP-2 can be effectively used alongside allograft to provide sufficient osteoinduction to promote bone fusion, without a significant risk of complications. In this issue of WORLD NEUROSURGERY, the study by Hood et al. (22) addresses the latter question by addressing the dose of rhBMP-2 used. In the largest retrospective series on the topic, they present 52 patients who underwent atlantoaxial fusion with low dose (average, 4.5 mg; range, 2.2e12 mg) rhBMP-2 for C1-C2 instability. For the 50 patients that had sufficient follow-up (average, 23.9 months), they found that 100% of patients achieved fusion, and that none had complications directly attributable to the rhBMP-2. These preliminary findings are promising, in that the surgery provides the potential for improved fusion rates with the use of allograft, yet avoiding the morbidity associated with autograft harvest. This strategy also shortens operative time and is associated with less blood loss that was observed with autograft harvest. The optimal graft substrate is yet to be defined. The preliminary results reported by Hood et al. (22) are promising, but the limitations of this approach are well recognized. As they acknowledged, their study is retrospective, involves varying doses of rhBMP-2, and different surgical techniques used by the two participating institutions involved in their study. The study also lacks a control population who did not receive rhBMP-2. Hence, the true contribution of rhBMP-2 to fusion outcome is difficult to ascertain. In a relevant study of atlantoaxial fusion, Hillard et al. (20) compared 47 patients who underwent C1-C2 arthrodesis with allograft and in 42 patients who underwent C1-2 arthrodesis with autograft. They found no significant differences between the two groups, with 97% of patients in the autograft group achieving
REFERENCES 1. Abdullah KG, Steinmetz MP, Benzel EC, Mroz TE: The state of lumbar fusion extenders. Spine 36: E1328-E1334, 2011. 2. Aryan HE, Newman CB, Nottmeier EW, Acosta FL Jr, Wang VY, Ames CP: Stabilization of the atlantoaxial complex via C-1 lateral mass and C-2 pedicle screw fixation in a multicenter clinical experience in 102 patients: modification of the Harms and Goel techniques. J Neurosurg Spine 8: 222-229, 2008. 3. Baskin DS, Ryan P, Sonntag V, Westmark R, Widmayer MA: A prospective, randomized, controlled cervical fusion study using recombinant human bone morphogenetic protein-2 with the CORNERSTONE-SR allograft ring and the ATLANTIS anterior cervical plate. Spine 28: 1219-1224, 2003.
2
www.SCIENCEDIRECT.com
fusion at 24 months postoperatively, compared with 89% with allograft. At the final follow-up, this nonsignificant difference was even smaller with 97% in the autograft group and 92% in the allograft group showing solid fusion. Similar results were found by Elliott et al. (12) in their systematic review of the literature. They identified 13 studies reporting on 652 patients who underwent C1-C2 dorsal instrumented arthrodesis with iliac crest autograft, and 7 studies with 60 patients who underwent C1-C2 dorsal instrumented arthrodesis with cadaveric allograft. They found no significant differences between the two groups regarding complications, mortality, or fusion rates—with a 99.7% fusion rate in the autograft group and a 100% fusion rate in the allograft group. The studies by Hillard et al. (20), Elliott et al. (12), and Hood et al. (22) emphasized their observation regarding the importance of surgical technique in promoting fusion. Specifically, packing the C1-2 joint with allograft material and incorporating the graft under compression, promotes fusion. Although some surgeons prefer to use on-lay allograft, this may be a relative disadvantage and deter fusion. In contrast, by taking advantage of load sharing and compressive forces, as originally described by Wolff’s law (8, 14, 15, 41), packing the C1-2 joint with allograft can lead to high fusion rates and superior outcomes. The study by Hood et al. (22) is the largest series reporting dorsal C1-C2 surgery with allograft and identifies the fusion rate, dose of rhBMP-2 needed for fusion, and the postoperative outcomes. These data provide the foundation for future well-designed prospective clinical trials that will most certainly include validated outcome measures to assess complications, fusion rates, and quality of life, as well as cost. The comparative effectiveness of allograft versus autograft, the relative advantages and disadvantages of the various available surgical techniques, and the impact of packing versus on-lay of the graft material for atlantoaxial fusion must all be addressed. Furthermore, it will become increasingly important for us all to understand the comparative and cost effectiveness of the various bone graft extenders including rhBMP-2. By reporting their institutional experience, Hood et al. (22) have contributed to, and advanced, the understanding of rhBMP-2, unique allograft applications, and atlantoaxial fusion techniques.
4. Benglis D, Wang MY, Levi AD: A comprehensive review of the safety profile of bone morphogenetic protein in spine surgery. Neurosurgery 62: ONS423-ONS431, 2008. 5. Brooks AL, Jenkins EB: Atlanto-axial arthrodesis by the wedge compression method. Am J Bone Joint Surg 60:279-284, 1978. 6. Carragee EJ, Bono CM, Scuderi GJ: Pseudomorbidity in iliac crest bone graft harvesting: the rise of rhBMP-2 in short-segment posterior lumbar fusion. Spine 9:873-879, 2009. 7. Center for Devices and Radiological Health. Public Health Notifications (Medical Devices)—FDA Public Health Notification: Life-threatening Complications Associated with Recombinant Human Bone Morphogenetic Protein in Cervical Spine Fusion. Silver Spring, MD: US Department of Health and Human Services, US Food and Drug Administration; 2008.
8. Chen J-H, Liu C, You L, Simmons CA: Boning up on Wolff’s law: mechanical regulation of the cells that make and maintain bone. J Biomech 43: 108-118, 2010. 9. Dickman CA, Sonntag VK: Posterior C1-C2 transarticular screw fixation for atlantoaxial arthrodesis. Neurosurgery 43:275-280, 1998. 10. Dickman CA, Sonntag VK, Papadopoulos SM, Hadley MN: The interspinous method of posterior atlantoaxial arthrodesis. J Neurosurg 74:190-198, 1991. 11. Dimar JR 2nd, Glassman SD, Burkus JK, Pryor PW, Hardacker JW, Carreon LY: Two-year fusion and clinical outcomes in 224 patients treated with a single-level instrumented posterolateral fusion with iliac crest bone graft. Spine 9: 880-885, 2009.
WORLD NEUROSURGERY, http://dx.doi.org/10.1016/j.wneu.2013.02.077
PERSPECTIVES
12. Elliott RE, Morsi A, Frempong-Boadu A, Smith ML: Is allograft sufficient for posterior atlantoaxial instrumented fusions with screw and rod constructs? A structured review of literature. World Neurosurg 78:326-338, 2012. 13. Fielding JW, Hawkins RJ, Ratzan SA: Spine fusion for atlanto-axial instability. Am J Bone Joint Surg 58:400-407, 1976. 14. Frost HM: Wolff’s law and bone’s structural adaptations to mechanical usage: an overview for clinicians. Angle Orthodont 64:175-188, 1994. 15. Frost HM A: 2003 update of bone physiology and Wolff’s law for clinicians. Angle Orthodont 74: 3-15, 2004. 16. Gallie W: Fractures and dislocations of the cervical spine. Am J Surg 16:495-499, 1939. 17. Goel A, Desai KI, Muzumdar DP: Atlantoaxial fixation using plate and screw method: a report of 160 treated patients. Neurosurgery 51:1351-1356, 2002. 18. Goel A, Laheri V: Plate and screw fixation for atlanto-axial subluxation. Acta Neurochirurg 129: 47-53, 1994. 19. Harms J, Melcher RP: Posterior C1-C2 fusion with polyaxial screw and rod fixation. Spine 26: 2467-2471, 2001. 20. Hillard VH, Fassett DR, Finn MA, Apfelbaum RI: Use of allograft bone for posterior C1-2 fusion. J Neurosurg Spine 11:396-401, 2009. 21. Holness RO, Huestis WS, Howes WJ, Langille RA: Posterior stabilization with an interlaminar clamp in cervical injuries: technical note and review of the long term experience with the method. Neurosurgery 14:318-322, 1984. 22. Hood B, Hamilton DK, Smith JS, Dididze M, Shaffrey C, Levi AD: The use of allograft and recombinant human bone morphogenetic protein for instrumented atlantoaxial fusions. World Neurosurg 2013 Jan 19 [Epub ahead of print]. 23. Hsu WK, Wang JC: The use of bone morphogenetic protein in spine fusion. Spine J 8:419-425, 2008.
24. Kim DH, Rhim R, Li L, Martha J, Swaim BH, Banco RJ, Jenis LG, Tromanhauser SG: Prospective study of iliac crest bone graft harvest site pain and morbidity. Spine J 9:886-892, 2009.
36. Robertson PA, Wray AC: Natural history of posterior iliac crest bone graft donation for spinal surgery: a prospective analysis of morbidity. Spine 26:1473-1476, 2001.
25. Leonard JR, Wright NM: Pediatric atlantoaxial fixation with bilateral, crossing C-2 translaminar screws. Technical note. J Neurosurg 104:59-63, 2006.
37. Sawin PD, Traynelis VC, Menezes AH: A comparative analysis of fusion rates and donorsite morbidity for autogeneic rib and iliac crest bone grafts in posterior cervical fusions. J Neurosurg 88:255-265, 1998.
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Citation: World Neurosurg. (2014). http://dx.doi.org/10.1016/j.wneu.2013.02.077 Journal homepage: www.WORLDNEUROSURGERY.org Available online: www.sciencedirect.com
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