Neurosurg Rev DOI 10.1007/s10143-014-0531-0
CASE REPORT
Occipitocervical fusion with relief of odontoid invagination: atlantoaxial distraction method using cylindrical titanium cage for basilar invagination—case report Tetsuya Yoshizumi & Hidetoshi Murata & Yuriko Ikenishi & Mitsuru Sato & Hajime Takase & Kensuke Tateishi & Satoshi Nakanowatari & Jun Suenaga & Nobutaka Kawahara
Received: 15 August 2013 / Revised: 10 December 2013 / Accepted: 19 January 2014 # Springer-Verlag Berlin Heidelberg 2014
Abstract A 65-year-old woman presented with basilar invagination manifesting as neck pain, dysesthesia around the lips, and truncal ataxia. The radiological findings demonstrated invagination of the odontoid process into the medulla oblongata and vertical atlantoaxial subluxation with C1 assimilation. The clivo-axial angle was 88° and the cervicomedullary angle was 115°, indicating severe basilar invagination. We planned occipitocervical fusion with atlantoaxial distraction using a cylindrical titanium cage. C2 pedicle screws were inserted, and the atlantoaxial joint was opened to translocate the odontoid process downward. A cylindrical titanium cage packed with local bone graft was inserted into the opened facet joint space. Occipital-C2 fusion was completed by fastening the occipital bone plates with pedicle screws using titanium rods. Postoperatively, the apex of the odontoid process descended by 7 mm, and the clivoaxial and cervicomedullary angles opened to 112° and 125°, respectively. Invagination of the odontoid process into the medulla oblongata was relieved. The preoperative symptoms improved, and she remained symptom-free without requiring anterior decompression over 2 years. Bone fusion of the atlantoaxial joints was completed with sustained facet distraction 12 months after the surgery, and adequate relief of the basilar invagination was maintained. The atlantoaxial distraction method using a cylindrical titanium cage can be a useful option in posterior fusion surgery for basilar invagination.
T. Yoshizumi : H. Murata (*) : Y. Ikenishi : M. Sato : H. Takase : K. Tateishi : S. Nakanowatari : J. Suenaga : N. Kawahara Department of Neurosurgery, Yokohama City University Graduate School of Medical Sciences, 3-9 Fukuura, Kanazawa-ku, Yokohama 236-0004, Kanawaga, Japan e-mail: [email protected]
Keywords Basilar invagination . Atlantoaxial subluxation . Cylindrical titanium cage
Introduction Basilar invagination (BI) is caused by malalignment or instability at the occipitocervical junction and may cause compression of the spinal cord or medulla oblongata, inducing myelopathy, intractable neck pain, or progressive disability [11, 12, 21]. Posterior occipitocervical or atlantoaxial reconstructive surgery is one major option for the treatment of BI [3, 7, 18, 20, 25]. Various surgical procedures for posterior occipitocervical fusion have been improved with the maintenance of corrected alignment, increased fusion rate, and decreased incidence of complications [1, 11, 23, 24]. Currently, posterior occipitocervical fixation using screw-rod/plate systems has gained mainstream acceptance. C1-2 posterior instrumented fusion with C1 lateral mass and C2 pedicle screw-plate constructs was introduced in 1994 by Goel and Laheri [6] and later modified to use polyaxial cantilever screw-rod constructs by Harms and Melcher [14]. Atlantoaxial fusion using the Goel-Harms technique is currently widely accepted, and high rates of fusion (>98 %) have been achieved regardless of the various techniques of C1-lateral mass screw insertion [4]. However, these fusion procedures may be unsatisfactory for the reduction of malalignment including BI [11]. Direct anterior decompression by transoral odontoidectomy may be required if the invagination to the spinal cord or medulla oblongata caused by the odontoid process is severe. Goel introduced a procedure for treating selected cases of BI by combining atlantoaxial joint
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distraction, reduction of BI, and direct lateral mass and atlantoaxial plate/screw fixation [8]. Atlantoaxial joint distraction was achieved by opening the atlantoaxial joint, inserting metal spacers into the joint, and fixing the atlas and axis with plate and screws. However, the procedure for atlantoaxial joint distraction can be complicated, and whether corrected alignment or reduction of BI can be maintained with solid fusion over the long term remains unclear. We report a case of BI treated by occipitocervical fusion with atlantoaxial distraction, which relieved the odontoid invagination by distracting the atlantoaxial joint and inserting a cylindrical titanium cage packed with pieces of bone graft. This procedure allows safe and easy engagement of the cage and can provide adequate relief of odontoid invagination coupled with posterior decompression and rigid fusion. This technique is a useful option in occipitocervical or atlantoaxial fusion surgery for BI.
Case report A 65-year-old woman suffered from neck pain, dysesthesia around the lips, and truncal ataxia. She had difficulty in raising her legs and showed unstable spastic gait. Magnetic resonance (MR) imaging of the cervical spine demonstrated invagination of the odontoid process into the medulla oblongata, which resulted from vertical atlantoaxial subluxation with C1 assimilation. She was referred to our hospital for treatment. On admission, she had no motor weakness or hyperreflexia. Alternate motion rate, the rate of finger opening and closing for 10 s, was 25 times/10 s in the right hand and 30 Fig. 1 a Preoperative computed tomography scan showing basilar invagination and atlantoaxial dislocation and various morphometric values of the basilar invagination in the lower section. The tip of the odontoid process has invaginated into the foramen magnum to 6.5 mm above the Chamberlain line and above the McRae line. The clivoaxial angle is 88°, which is markedly acute compared to the normal range. The atlanto-dental interval is 7.5 mm, which is abnormally wide. b Preoperative T2-weighted magnetic resonance image showing marked compression of the cervicomedullary junction caused by the odontoid invagination and hyperintense signal in the spinal cord. The cervicomedullary angle is 115°, which is markedly acute compared to the normal range
a
times/10 s in the left hand, which indicated that physiological fine motor coordination of the fingers was maintained because the normal rate is more than 25 times/10 s. She had dysesthesia of the lips. Romberg signs were positive. The Japanese Orthopaedic Association score was 15 of 17 points [5], and the Neurosurgical Cervical Spine Scale score was 12 of 14 points [17]. Computed tomography (CT) of the cervical spine revealed BI and atlantoaxial subluxation (Fig. 1a). The tip of the odontoid process had invaginated into the foramen magnum to 6.5 mm above the Chamberlain line and above the McRae line (Fig. 1a). The clivo-axial angle, between the dorsum clivus and the axis, was 88°, which was markedly acute compared to the normal range of 145° to 160° in the neutral position [19]. The atlanto-dental interval was 7.5 mm, which was abnormally wide, indicating atlantoaxial subluxation. CT and radiography showed that the atlas was fused to the occipital bone, or assimilation of the atlas. MR imaging of the cervical spine demonstrated ventral compression of the cervicomedullary junction caused by the odontoid invagination, and T2-weighted imaging showed hyperintense signal in the spinal cord (Fig. 1b). The cervicomedullary angle, between the medulla and upper cervical cord, was 115°, which was markedly acute compared to the normal range of 135– 175° [2]. Furthermore, lateral radiography of the craniovertebral junction showed that the clivo-axial angle was slightly reduced at 95° in the extension position compared with 88° in the neutral position (Fig. 2). Occipitocervical fusion with atlantoaxial distraction using a cylindrical titanium cage was planned, with intentional widening of the atlantoaxial joint to reduce the compression
b
Neurosurg Rev Fig. 2 Lateral radiographs showing the clivo-axial angle is 88° in the neutral position (a) and 95° in the extension position (b)
of the odontoid process on the brainstem and upper cervical spinal cord. If this procedure was ineffective, we planned subsequent transoral odontoidectomy. She was placed in the prone position with the upper body elevated by 15°, and her head was fixed with a three-point Mayfield clamp, leaving her neck stretched in the neutral position. A midline skin incision, 7 cm long, was made in the posterior neck to expose the occipital bone assimilated with the C1 lamina and the C2 spinous process and lamina. The foramen magnum was decompressed. Then, C2 pedicle screws (3.5 mm diameter, 22 mm length, OASYS® OccipitoCervico-Thoracic System; Stryker Corp., Kalamazoo, MI, USA) were inserted. The capsule and cartilage of the atlantoaxial joint were exenterated using a micro-drill after sectioning of the C2 nerve root. The atlantoaxial joints were then distracted and opened using the osteotome, which was
Fig. 3 Intraoperative photographs showing the atlantoaxial joint (arrows) distracted using the osteotome, which was introduced into the joint and then turned slowly through 90° to open the joint (a), and the cylindrical titanium cage (CTC) inserted into the opened atlantoaxial joint and completed occipito-C2 fixation (b). FM foramen magnum, Oc occipital bone
introduced into the joint in parallel and then turned slowly by 90° to open the atlantoaxial joint (Fig. 3a). This procedure translocated the odontoid process downward. The cylindrical titanium cage (12 mm length and 6 mm diameter, M-cage; Ammtec Inc., Tokyo, Japan), packed with pieces of bone graft harvested from the occipital bone, was inserted into the opened joint space to maintain the position. After that, the occipito-C2 fusion procedure was completed by fastening titanium plates on the occipital bone with C2 pedicle screws through titanium rods (3.5 mm diameter, OASYS® Occipito-Cervico-Thoracic System) (Figs. 3b and 4a, b, d). The distraction of the atlantoaxial joint was monitored under intraoperative radiological control. To promote adequate bone fusion, additional bone graft was placed around the occipital bone edge and C2 lamina.
a
b CTC Oc
Oc
FM
FM
C2 C2 CTC
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Fig. 4 a Postoperative sagittal reconstructed computed tomography (CT) scan showing reduction of the basilar invagination. The tip of the odontoid process has descended to 7 mm below the McRae line. The clivo-axial angle has opened to 112°. b Postoperative coronal reconstructed CT scan showing the cage inserted into the atlantoaxial joint. c Postoperative T2-weighted magnetic resonance image showing relief of
the odontoid invagination into the cervicomedullary junction, and the cervicomedullary angle opened to 125°. d Postoperative lateral radiograph showing occipito-C2 fixation with the cage in the atlantoaxial joint. e CT scan obtained 12 months after the surgery showing bone fusion in the atlantoaxial joint around the inserted cage with sustained facet distraction
After surgery, the apex of the odontoid process had descended by 7 mm, and the clivo-axial and cervicomedullary angles had opened to 112° and 125°, respectively (Fig. 4a, c). MR imaging of the cervical spine showed relief of the invagination of the odontoid process into the medulla oblongata compared with the preoperative state (Fig. 4c). CT of the cervical spine demonstrated that the BI was relieved, and adequate bone fusion of the atlantoaxial joint was achieved with sustained facet distraction 12 months after the surgery (Fig. 4e). The preoperative symptoms improved, and she remained symptom-free for 30 months after the surgery. The occipital numbness related to resection of the C2 nerve root had almost resolved a year after surgery. Clinical observation to assess alignment change including cage subsidence will be continued over the long term.
occipitocervical fixation, but transoral decompression was required in all patients because reduction of the BI was not maintained [7]. However, a combination of this procedure with relief of invagination of the odontoid process would be a useful option in posterior fusion surgery for BI. Various methods of occipitocervical reconstruction for reduction of BI have been reported. Abumi et al. reported occipitocervical reconstruction using pedicle screws and occipitocervical rod systems with the aim of reduction and fixation for atlantoaxial subluxation associated with BI [1]. The flexion deformity of the occipitoatlantoaxial complex was corrected by extensional force, and invagination of the odontoid process reduced by extensional force between the occiput and the cervical pedicle screws. This procedure was aimed at indirect reduction of the odontoid process by changing neck alignment in the extension position. However, whether reduction of BI can be consistently achieved and maintained with solid fusion over the long term remains uncertain. Goel et al. described a technique for treating BI by performing atlantoaxial joint distraction, reduction of the odontoid invagination, and direct lateral mass and atlantoaxial plate/screw fixation [8, 9]. Direct translocation of the odontoid process downward was attempted to relieve odontoid invagination during occipitocervical or atlantoaxial fusion for BI. A specially designed spiked metal spacer was engaged into the distracted atlantoaxial facet joint, and bone graft was
Discussion Surgical treatment for BI consists of decompression and fusion surgery. BI with associated Chiari malformation usually does not involve atlantoaxial dislocation and can usually be treated by only posterior bone decompression of the foramen magnum [7]. Reducible BI can be treated with posterior occipitocervical fusion. However, irreducible BI requires anterior decompression followed by posterior fusion [3, 18, 25]. Goel et al. attempted to treat BI by cervical traction and
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additionally placed within part of the atlantoaxial joint and posterior to the arch of the atlas and lamina of C2. This procedure is intended to achieve relief of the invagination of the odontoid process and posterior fusion at the same time. However, the procedures for atlantoaxial joint distraction including insertion of the metal spacer can be slightly complicated, and whether corrected alignment or reduction of BI can be maintained with solid fusion over the long term remains unclear. Solid fusion of the corrected or distracted atlantoaxial joint is critical for the maintenance of reduction of BI and stability of reconstruction. Our present case of BI was treated by occipitocervical fusion with atlantoaxial distraction using a cylindrical titanium cage packed with pieces of bone graft. The cylindrical cage is easy to insert into the opened atlantoaxial joint and can provide rigid bone fusion of atlantoaxial joint. In fact, the titanium cage is widely used for anterior cervical fusion and demonstrates immediate good stabilization and reliable fusion without donor site-related complication [13, 15]. In the present case, bone fusion of the atlantoaxial joints was completed with sustained facet distraction 12 months after the surgery, and relief of the BI was maintained (Fig. 4e). The patient has remained symptom-free for 30 months after the surgery. Currently, she has no need for anterior decompression by transoral odontoidectomy, which has some disadvantages including the risk of infection, prolonged intubation or tracheostomy, need for nasogastric tube feeding, extended hospitalization, and possible effects on phonation [22]. The key to successfully performing the atlantoaxial distraction method for BI is to ensure adequate space for the procedure by exposing the facets of the atlas and axis. In practice, we sectioned the C2 nerve roots, controlled the developed venous plexus, fully exposed the facets, and then distracted the facets with the osteotome. Ensuring sufficient space around the facets facilitates insertion of the cylindrical titanium cage into the joint space while sustaining the distraction with the retractor. However, full exposure of the facets may not be easy, especially in patients with BI who have bone anomalies and developed venous plexus. Resection of the C2 nerve roots allows control of the venous plexus around the facet and excision of the joint capsule to safely operate between the facets of the atlantoaxial joint. Resection of the C2 nerve root may cause occipital numbness along the distribution of the nerve, but the area of numbness usually reduces over the years [10, 16]. In the present case, the occipital numbness markedly diminished in the year after surgery as previously described. Recently, an atlantoaxial distraction method without fusion of the atlantoaxial joint was reported for the treatment of BI [16]. The vertical subluxation is reduced without exposure of the atlantoaxial joint by distracting between the occiput and the C2 pedicle screw. This procedure without exposure of the atlantoaxial joint decreases the risk of hemorrhage from the
venous plexus and makes sectioning of C2 nerve root unnecessary. However, we are concerned about the shortening of the atlantoaxial joint, instrument failure, and loss of correction of occipitocervical alignment over the long term, because the atlantoaxial joint remains unfixed with free space. Adequate fusion of the corrected or distracted atlantoaxial joint is critical for the maintenance of reduction of the BI and stability of the reconstruction. The atlantoaxial distraction method for BI is intended to relieve odontoid invagination coupled with occipitocervical or atlantoaxial fusion. However, the manipulation to translocate the odontoid process downward might affect the fragile spinal cord or medulla oblongata in patients with severe neurological impairment or marked compression of the brainstem/spinal cord. In the present case, we did not monitor neurological function such as motor-evoked potential and somatosensoryevoked potential because she had mild neurological impairment, but incorporation of such monitoring might have been desirable to increase the safety of the procedure. Therefore, this procedure should be performed under intraoperative radiological control, possibly with neurological monitoring, especially in a patient with severe neurological impairment or marked brainstem compression. This procedure can be safely and easily performed under such intraoperative monitoring, resulting in reduction of the BI with adequate bone fusion of the atlantoaxial joint using the cylindrical titanium cage. Consequently, this technique is a useful option in posterior occipitocervical or atlantoaxial fusion surgery for BI. Long-term assessment by cervical spine radiography, CT, and MR imaging is important to detect alignment change over time. Further experience with selected cases will validate the suitability of this procedure including the long-term stability.
Conclusion Atlantoaxial distraction using a cylindrical titanium cage can relieve odontoid invagination coupled with posterior occipitocervical or atlantoaxial fusion and is a useful option in posterior fusion surgery for BI.
References 1. Abumi K, Takada T, Shono Y, Kaneda K, Fujiya M (1999) Posterior occipitocervical reconstruction using cervical pedicle screws and plate-rod systems. Spine (Phila Pa 1976) 24:1425–1434 2. Bundschuh C, Modic MT, Kearney F, Morris R, Deal C (1988) Rheumatoid arthritis of the cervical spine: surface-coil MR imaging. AJR Am J Roentgenol 151:181–187 3. Dickman CA, Locantro J, Fessler RG (1992) The influence of transoral odontoid resection on stability of the craniovertebral junction. J Neurosurg 77:525–530
Neurosurg Rev 4. Elliott RE, Tanweer O, Smith ML, Frempong-Boadu A (2014) Impact of starting point and bicortical purchase of C1 lateral mass screws on atlantoaxial fusion: meta-analysis and review of the literature. J Spinal Disord Tech. doi:10.1097/BSD.0b013e31828ffc97 5. Fukui K, Kataoka O, Sho T, Sumi M (1990) Pathomechanism, pathogenesis, and results of treatment in cervical spondylotic myelopathy caused by dynamic canal stenosis. Spine (Phila Pa 1976) 15: 1148–1152 6. Goel A, Laheri V (1994) Plate and screw fixation for atlanto-axial subluxation. Acta Neurochir (Wien) 129:47–53 7. Goel A, Bhatjiwale M, Desai K (1998) Basilar invagination: a study based on 190 surgically treated patients. J Neurosurg 88:962–968 8. Goel A (2004) Treatment of basilar invagination by atlantoaxial joint distraction and direct lateral mass fixation. J Neurosurg Spine 1:281– 286 9. Goel A, Shah A (2008) Atlantoaxial joint distraction as a treatment for basilar invagination: a report of an experience with 11 cases. Neurol India 56:144–150 10. Goel A, Shah A (2009) Reversal of longstanding musculoskeletal changes in basilar invagination after surgical decompression and stabilization. J Neurosurg Spine 10:220–227 11. Grob D, Dvorak J, Panjabi MM, Antinnes JA (1994) The role of plate and screw fixation in occipitocervical fusion in rheumatoid arthritis. Spine (Phila Pa 1976) 19:2545–2551 12. Grob D, Schutz U, Plotz G (1999) Occipitocervical fusion in patients with rheumatoid arthritis. Clin Orthop Relat Res 366:46–53 13. Hacker RJ, Cauthen JC, Gilbert TJ, Griffith SL (2000) A prospective randomized multicenter clinical evaluation of an anterior cervical fusion cage. Spine (Phila Pa 1976) Spine (Phila Pa 1976) 25:2646– 2654, discussion 2655 14. Harms J, Melcher RP (2001) Posterior C1-C2 fusion with polyaxial screw and rod fixation. Spine (Phila Pa 1976) 26:2467–2471 15. Hida K, Iwasaki Y, Yano S, Akino M, Seki T (2008) Long-term follow-up results in patients with cervical disk disease treated by cervical anterior fusion using titanium cage implants. Neurol Med Chir (Tokyo) 48:440–446, discussion 446 16. Jian FZ, Chen Z, Wrede KH, Samii M, Ling F (2010) Direct posterior reduction and fixation for the treatment of basilar invagination with atlantoaxial dislocation. Neurosurgery 66:678–687, discussion 687 17. Kadoya S (1992) Grading and scoring system for neurological function in degenerative cervical spine disease—Neurosurgical Cervical Spine Scale. Neurol Med Chir (Tokyo) 32:40–41 18. Menezes AH, VanGilder JC (1988) Transoral-transpharyngeal approach to the anterior craniocervical junction. Ten-year experience with 72 patients. J Neurosurg 69:895–903 19. Nagashima C, Kubota S (1983) Craniocervical abnormalities. Modern diagnosis and a comprehensive surgical approach. Neurosurg Rev 6:187–197 20. Nishikawa M, Ohata K, Baba M, Terakawa Y, Hara M (2004) Chiari I malformation associated with ventral compression and instability: one-stage posterior decompression and fusion with a new instrumentation technique. Neurosurgery 54:1430–1434, discussion 1434– 1435 21. Nockels RP, Shaffrey CI, Kanter AS, Azeem S, York JE (2007) Occipitocervical fusion with rigid internal fixation: long-term follow-up data in 69 patients. J Neurosurg Spine 7:117–123 22. Patel AJ, Boatey J, Muns J, Bollo RJ, Whitehead WE, Giannoni CM, Jea A (2012) Endoscopic endonasal odontoidectomy in a child with chronic type 3 atlantoaxial rotatory fixation: case report and literature review. Childs Nerv Syst 28:1971–1975 23. Sandhu FA, Pait TG, Benzel E, Henderson FC (2003) Occipitocervical fusion for rheumatoid arthritis using the insideoutside stabilization technique. Spine (Phila Pa 1976) 28: 414–419 24. Vale FL, Oliver M, Cahill DW (1999) Rigid occipitocervical fusion. J Neurosurg 91(2 Suppl):144–150
25. Zileli M, Cagli S (2002) Combined anterior and posterior approach for managing basilar invagination associated with type I Chiari malformation. J Spinal Disord Tech 15:284–289
Comments Atul Goel, Mumbai, India Basilar invagination is a manifestation of ‘vertical’ atlantoaxial instability [12]. Incompetence of the muscles of the nape of the neck secondary to trauma or poor muscle nutrition may be the pathogenetic cause. Listhesis of the facet of atlas over the facet of axis results in superior and posterior migration of the odontoid process in relationship to the arch of atlas resulting in basilar invagination and atlantoxial dislocation [14]. The atlantoaxial dislocation in such cases is not freely mobile and reducible and was earlier referred to as ‘fixed’ atlantoaxial dislocation [7]. The most defining feature that probably revolutionised the treatment of ‘basilar invagination’ was the identification of the fact that atlantoaxial joints in such cases are not fixed but are functional and mobile and, more importantly, are reducible [1, 5, 9]. Instability of the atlantoaxial joint and microtrauma inflicted to critical neural structures by repeated abnormal movements of the odontoid process are the cause of neurological deficits and are more important than structural malformation or deformation that it results [9]. The subtleness and long-standing nature of process of listhesis result in remarkable natural readjustments that lead to a host of musculoskeletal and neural alterations, all aimed at reducing the impact of instability and in reducing the neural compromise. Torticollis, short neck, platybasia, bone fusions and several similar morphological alterations that are frequently observed in cases with basilar invagination are all potentially reversible following surgical procedure that stabilizes the atlantoaxial joint [9]. Opening of the atlantoaxial joint, denuding of the articular cartilage, stuffing of bone graft within the confines of the atlantoaxial joint and subsequent plate/rod and screw fixation of C1 and C2 pars/pedicle/facets form the basis of our fixation technique [6, 8]. The description of feasibility and safety of sectioning of the C2 ganglion, whenever necessary, to obtain wide exposure of the region to complete all the steps of the fixation technique is another crucial step in the advancement of surgery in the craniovertebral region [4]. The exposure of the atlantoaxial joint in cases with basilar invagination is significantly more difficult when compared to normally located joints. The joints are rostrally located and dissection in the region amidst large venous complexes can be tedious. Sectioning of C2 ganglion, particularly in such cases, can assist in providing a panoramic view to the joint and facets so that the entire surgical procedure can be done under direct surgical vision. Distraction of facets of the spine by employing metal spacers is emerging to be a robust technique for provision of stability and realignment [10, 11]. Impaction of metal spacer within the atlantoaxial joint provides significant stability to the region [2]. Distraction of the facets by the spacers, at the site of fulcrum of craniovertebral movements, results in reduction of basilar invagination and restoration of craniovertebral and spinal alignment [4, 13]. However, as our experience in the treatment of basilar invagination in increasing, we have realised that it is more important to obtain stability of the atlantoaxial region than to aim at morphological reduction in basilar invagination. With that aim in mind, introduction of bone graft within the confines of the joint and in the appropriately prepared suboccipital region is crucially important. The authors in the present manuscript have resorted to inclusion of the occipital bone in the fusion construct. The use of short plates/rods and segmental fixation at the point of fulcrum of movements as is done for atlantoaxial fixation is biomechanically far superior when compared to the use of long plates/rods necessary for occipitocervical fixation. The use of long length screws as is possible in the strong and largely cortical bone facets of atlas and axis is much more robust
Neurosurg Rev when compared to the use of multiple short screws in the suboccipital squama. Inclusion of the occipital bone and sub-axial spinal segment not only is unnecessary, but can significantly reduce the strength of the implant and adversely affect the neck movements and neck growth [3]. Manipulation of the facets that is the point of pathogenesis of basilar invagination is far more effective than remote manipulation of the occipital bone. Although the technique of exposure of the atlantoaxial joint is relatively difficult and tedious, if learnt appropriately and performed adequately, it can lead to gratifying surgical results in this relatively complex and daunting clinical situation. References 1. Goel A (2004) Treatment of basilar invagination by atlantoaxial joint distraction and direct lateral mass fixation. J Neurosurg Spine.1(3):281–6. 2. Goel A (2007) Atlantoaxial joint jamming as a treatment for atlantoaxial dislocation: a preliminary report. Technical note. J Neurosurg Spine.7(1):90–4. 3. Goel A (2010) Occipitocervical fixation—is it necessary? Editorial, J Neurosurg Spine. 13(1):1–2. 4. Goel A (2012) Cervical ganglion 2 (CG2) neurectomy: a window to the atlantoaxial joint. World Neurosurg.78(1–2):78–9 5. Goel A, Bhatjiwale M, Desai K (1988) Basilar invagination: a study based on 190 surgically treated cases. J Neurosurg 88:962–968.
6. Goel A, Desai K, Muzumdar D (2002) Atlantoaxial fixation using plate and screw method: a report of 160 treated patients. Neurosurgery 51; 1351–1357. 7. Goel A, Kulkarni AG, Sharma P (2005) Reduction of fixed atlantoaxial dislocation in 24 cases: technical note. J Neurosurg Spine 2(4):505–9. 8. Goel A, Laheri VK (1994) Plate and screw fixation for atlanto-axial dislocation. (technical report). Acta Neurochir (Wien) 129:47–53. 9. Goel A, Shah A (2009) Reversal of longstanding musculoskeletal changes in basilar invagination after surgical decompression and stabilization. J Neurosurg Spine.10(3):220–7. 10. Goel A, Shah A (2011) Facetal distraction as treatment for singleand multilevel cervical spondylotic radiculopathy and myelopathy: a preliminary report. J Neurosurg Spine 14(6):689–96. 11. Goel A, Shah A, Jadhav M, Nama S (2013) Distraction of facets with intraarticular spacers as treatment for lumbar canal stenosis: report on a preliminary experience with 21 cases. J Neurosurg Spine 19(6):672–7. 12. Goel A, Shah A, Rajan S (2009) Vertical mobile and reducible atlantoaxial dislocation. Clinical article. J Neurosurg Spine 11(1):9–14. 13. Goel A, Sharma P. (2005) Craniovertebral junction realignment for the treatment of basilar invagination with syringomyelia: preliminary report of 12 cases. Neurol Med Chir (Tokyo) 45(10):512–8. 14. Kothari M, Goel A (2007) Transatlantic odonto-occipital listhesis: the so-called basilar invagination. Neurol India 55(1):6–7.
CASE REPORT
Occipitocervical fusion with relief of odontoid invagination: atlantoaxial distraction method using cylindrical titanium cage for basilar invagination—case report Tetsuya Yoshizumi & Hidetoshi Murata & Yuriko Ikenishi & Mitsuru Sato & Hajime Takase & Kensuke Tateishi & Satoshi Nakanowatari & Jun Suenaga & Nobutaka Kawahara
Received: 15 August 2013 / Revised: 10 December 2013 / Accepted: 19 January 2014 # Springer-Verlag Berlin Heidelberg 2014
Abstract A 65-year-old woman presented with basilar invagination manifesting as neck pain, dysesthesia around the lips, and truncal ataxia. The radiological findings demonstrated invagination of the odontoid process into the medulla oblongata and vertical atlantoaxial subluxation with C1 assimilation. The clivo-axial angle was 88° and the cervicomedullary angle was 115°, indicating severe basilar invagination. We planned occipitocervical fusion with atlantoaxial distraction using a cylindrical titanium cage. C2 pedicle screws were inserted, and the atlantoaxial joint was opened to translocate the odontoid process downward. A cylindrical titanium cage packed with local bone graft was inserted into the opened facet joint space. Occipital-C2 fusion was completed by fastening the occipital bone plates with pedicle screws using titanium rods. Postoperatively, the apex of the odontoid process descended by 7 mm, and the clivoaxial and cervicomedullary angles opened to 112° and 125°, respectively. Invagination of the odontoid process into the medulla oblongata was relieved. The preoperative symptoms improved, and she remained symptom-free without requiring anterior decompression over 2 years. Bone fusion of the atlantoaxial joints was completed with sustained facet distraction 12 months after the surgery, and adequate relief of the basilar invagination was maintained. The atlantoaxial distraction method using a cylindrical titanium cage can be a useful option in posterior fusion surgery for basilar invagination.
T. Yoshizumi : H. Murata (*) : Y. Ikenishi : M. Sato : H. Takase : K. Tateishi : S. Nakanowatari : J. Suenaga : N. Kawahara Department of Neurosurgery, Yokohama City University Graduate School of Medical Sciences, 3-9 Fukuura, Kanazawa-ku, Yokohama 236-0004, Kanawaga, Japan e-mail: [email protected]
Keywords Basilar invagination . Atlantoaxial subluxation . Cylindrical titanium cage
Introduction Basilar invagination (BI) is caused by malalignment or instability at the occipitocervical junction and may cause compression of the spinal cord or medulla oblongata, inducing myelopathy, intractable neck pain, or progressive disability [11, 12, 21]. Posterior occipitocervical or atlantoaxial reconstructive surgery is one major option for the treatment of BI [3, 7, 18, 20, 25]. Various surgical procedures for posterior occipitocervical fusion have been improved with the maintenance of corrected alignment, increased fusion rate, and decreased incidence of complications [1, 11, 23, 24]. Currently, posterior occipitocervical fixation using screw-rod/plate systems has gained mainstream acceptance. C1-2 posterior instrumented fusion with C1 lateral mass and C2 pedicle screw-plate constructs was introduced in 1994 by Goel and Laheri [6] and later modified to use polyaxial cantilever screw-rod constructs by Harms and Melcher [14]. Atlantoaxial fusion using the Goel-Harms technique is currently widely accepted, and high rates of fusion (>98 %) have been achieved regardless of the various techniques of C1-lateral mass screw insertion [4]. However, these fusion procedures may be unsatisfactory for the reduction of malalignment including BI [11]. Direct anterior decompression by transoral odontoidectomy may be required if the invagination to the spinal cord or medulla oblongata caused by the odontoid process is severe. Goel introduced a procedure for treating selected cases of BI by combining atlantoaxial joint
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distraction, reduction of BI, and direct lateral mass and atlantoaxial plate/screw fixation [8]. Atlantoaxial joint distraction was achieved by opening the atlantoaxial joint, inserting metal spacers into the joint, and fixing the atlas and axis with plate and screws. However, the procedure for atlantoaxial joint distraction can be complicated, and whether corrected alignment or reduction of BI can be maintained with solid fusion over the long term remains unclear. We report a case of BI treated by occipitocervical fusion with atlantoaxial distraction, which relieved the odontoid invagination by distracting the atlantoaxial joint and inserting a cylindrical titanium cage packed with pieces of bone graft. This procedure allows safe and easy engagement of the cage and can provide adequate relief of odontoid invagination coupled with posterior decompression and rigid fusion. This technique is a useful option in occipitocervical or atlantoaxial fusion surgery for BI.
Case report A 65-year-old woman suffered from neck pain, dysesthesia around the lips, and truncal ataxia. She had difficulty in raising her legs and showed unstable spastic gait. Magnetic resonance (MR) imaging of the cervical spine demonstrated invagination of the odontoid process into the medulla oblongata, which resulted from vertical atlantoaxial subluxation with C1 assimilation. She was referred to our hospital for treatment. On admission, she had no motor weakness or hyperreflexia. Alternate motion rate, the rate of finger opening and closing for 10 s, was 25 times/10 s in the right hand and 30 Fig. 1 a Preoperative computed tomography scan showing basilar invagination and atlantoaxial dislocation and various morphometric values of the basilar invagination in the lower section. The tip of the odontoid process has invaginated into the foramen magnum to 6.5 mm above the Chamberlain line and above the McRae line. The clivoaxial angle is 88°, which is markedly acute compared to the normal range. The atlanto-dental interval is 7.5 mm, which is abnormally wide. b Preoperative T2-weighted magnetic resonance image showing marked compression of the cervicomedullary junction caused by the odontoid invagination and hyperintense signal in the spinal cord. The cervicomedullary angle is 115°, which is markedly acute compared to the normal range
a
times/10 s in the left hand, which indicated that physiological fine motor coordination of the fingers was maintained because the normal rate is more than 25 times/10 s. She had dysesthesia of the lips. Romberg signs were positive. The Japanese Orthopaedic Association score was 15 of 17 points [5], and the Neurosurgical Cervical Spine Scale score was 12 of 14 points [17]. Computed tomography (CT) of the cervical spine revealed BI and atlantoaxial subluxation (Fig. 1a). The tip of the odontoid process had invaginated into the foramen magnum to 6.5 mm above the Chamberlain line and above the McRae line (Fig. 1a). The clivo-axial angle, between the dorsum clivus and the axis, was 88°, which was markedly acute compared to the normal range of 145° to 160° in the neutral position [19]. The atlanto-dental interval was 7.5 mm, which was abnormally wide, indicating atlantoaxial subluxation. CT and radiography showed that the atlas was fused to the occipital bone, or assimilation of the atlas. MR imaging of the cervical spine demonstrated ventral compression of the cervicomedullary junction caused by the odontoid invagination, and T2-weighted imaging showed hyperintense signal in the spinal cord (Fig. 1b). The cervicomedullary angle, between the medulla and upper cervical cord, was 115°, which was markedly acute compared to the normal range of 135– 175° [2]. Furthermore, lateral radiography of the craniovertebral junction showed that the clivo-axial angle was slightly reduced at 95° in the extension position compared with 88° in the neutral position (Fig. 2). Occipitocervical fusion with atlantoaxial distraction using a cylindrical titanium cage was planned, with intentional widening of the atlantoaxial joint to reduce the compression
b
Neurosurg Rev Fig. 2 Lateral radiographs showing the clivo-axial angle is 88° in the neutral position (a) and 95° in the extension position (b)
of the odontoid process on the brainstem and upper cervical spinal cord. If this procedure was ineffective, we planned subsequent transoral odontoidectomy. She was placed in the prone position with the upper body elevated by 15°, and her head was fixed with a three-point Mayfield clamp, leaving her neck stretched in the neutral position. A midline skin incision, 7 cm long, was made in the posterior neck to expose the occipital bone assimilated with the C1 lamina and the C2 spinous process and lamina. The foramen magnum was decompressed. Then, C2 pedicle screws (3.5 mm diameter, 22 mm length, OASYS® OccipitoCervico-Thoracic System; Stryker Corp., Kalamazoo, MI, USA) were inserted. The capsule and cartilage of the atlantoaxial joint were exenterated using a micro-drill after sectioning of the C2 nerve root. The atlantoaxial joints were then distracted and opened using the osteotome, which was
Fig. 3 Intraoperative photographs showing the atlantoaxial joint (arrows) distracted using the osteotome, which was introduced into the joint and then turned slowly through 90° to open the joint (a), and the cylindrical titanium cage (CTC) inserted into the opened atlantoaxial joint and completed occipito-C2 fixation (b). FM foramen magnum, Oc occipital bone
introduced into the joint in parallel and then turned slowly by 90° to open the atlantoaxial joint (Fig. 3a). This procedure translocated the odontoid process downward. The cylindrical titanium cage (12 mm length and 6 mm diameter, M-cage; Ammtec Inc., Tokyo, Japan), packed with pieces of bone graft harvested from the occipital bone, was inserted into the opened joint space to maintain the position. After that, the occipito-C2 fusion procedure was completed by fastening titanium plates on the occipital bone with C2 pedicle screws through titanium rods (3.5 mm diameter, OASYS® Occipito-Cervico-Thoracic System) (Figs. 3b and 4a, b, d). The distraction of the atlantoaxial joint was monitored under intraoperative radiological control. To promote adequate bone fusion, additional bone graft was placed around the occipital bone edge and C2 lamina.
a
b CTC Oc
Oc
FM
FM
C2 C2 CTC
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Fig. 4 a Postoperative sagittal reconstructed computed tomography (CT) scan showing reduction of the basilar invagination. The tip of the odontoid process has descended to 7 mm below the McRae line. The clivo-axial angle has opened to 112°. b Postoperative coronal reconstructed CT scan showing the cage inserted into the atlantoaxial joint. c Postoperative T2-weighted magnetic resonance image showing relief of
the odontoid invagination into the cervicomedullary junction, and the cervicomedullary angle opened to 125°. d Postoperative lateral radiograph showing occipito-C2 fixation with the cage in the atlantoaxial joint. e CT scan obtained 12 months after the surgery showing bone fusion in the atlantoaxial joint around the inserted cage with sustained facet distraction
After surgery, the apex of the odontoid process had descended by 7 mm, and the clivo-axial and cervicomedullary angles had opened to 112° and 125°, respectively (Fig. 4a, c). MR imaging of the cervical spine showed relief of the invagination of the odontoid process into the medulla oblongata compared with the preoperative state (Fig. 4c). CT of the cervical spine demonstrated that the BI was relieved, and adequate bone fusion of the atlantoaxial joint was achieved with sustained facet distraction 12 months after the surgery (Fig. 4e). The preoperative symptoms improved, and she remained symptom-free for 30 months after the surgery. The occipital numbness related to resection of the C2 nerve root had almost resolved a year after surgery. Clinical observation to assess alignment change including cage subsidence will be continued over the long term.
occipitocervical fixation, but transoral decompression was required in all patients because reduction of the BI was not maintained [7]. However, a combination of this procedure with relief of invagination of the odontoid process would be a useful option in posterior fusion surgery for BI. Various methods of occipitocervical reconstruction for reduction of BI have been reported. Abumi et al. reported occipitocervical reconstruction using pedicle screws and occipitocervical rod systems with the aim of reduction and fixation for atlantoaxial subluxation associated with BI [1]. The flexion deformity of the occipitoatlantoaxial complex was corrected by extensional force, and invagination of the odontoid process reduced by extensional force between the occiput and the cervical pedicle screws. This procedure was aimed at indirect reduction of the odontoid process by changing neck alignment in the extension position. However, whether reduction of BI can be consistently achieved and maintained with solid fusion over the long term remains uncertain. Goel et al. described a technique for treating BI by performing atlantoaxial joint distraction, reduction of the odontoid invagination, and direct lateral mass and atlantoaxial plate/screw fixation [8, 9]. Direct translocation of the odontoid process downward was attempted to relieve odontoid invagination during occipitocervical or atlantoaxial fusion for BI. A specially designed spiked metal spacer was engaged into the distracted atlantoaxial facet joint, and bone graft was
Discussion Surgical treatment for BI consists of decompression and fusion surgery. BI with associated Chiari malformation usually does not involve atlantoaxial dislocation and can usually be treated by only posterior bone decompression of the foramen magnum [7]. Reducible BI can be treated with posterior occipitocervical fusion. However, irreducible BI requires anterior decompression followed by posterior fusion [3, 18, 25]. Goel et al. attempted to treat BI by cervical traction and
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additionally placed within part of the atlantoaxial joint and posterior to the arch of the atlas and lamina of C2. This procedure is intended to achieve relief of the invagination of the odontoid process and posterior fusion at the same time. However, the procedures for atlantoaxial joint distraction including insertion of the metal spacer can be slightly complicated, and whether corrected alignment or reduction of BI can be maintained with solid fusion over the long term remains unclear. Solid fusion of the corrected or distracted atlantoaxial joint is critical for the maintenance of reduction of BI and stability of reconstruction. Our present case of BI was treated by occipitocervical fusion with atlantoaxial distraction using a cylindrical titanium cage packed with pieces of bone graft. The cylindrical cage is easy to insert into the opened atlantoaxial joint and can provide rigid bone fusion of atlantoaxial joint. In fact, the titanium cage is widely used for anterior cervical fusion and demonstrates immediate good stabilization and reliable fusion without donor site-related complication [13, 15]. In the present case, bone fusion of the atlantoaxial joints was completed with sustained facet distraction 12 months after the surgery, and relief of the BI was maintained (Fig. 4e). The patient has remained symptom-free for 30 months after the surgery. Currently, she has no need for anterior decompression by transoral odontoidectomy, which has some disadvantages including the risk of infection, prolonged intubation or tracheostomy, need for nasogastric tube feeding, extended hospitalization, and possible effects on phonation [22]. The key to successfully performing the atlantoaxial distraction method for BI is to ensure adequate space for the procedure by exposing the facets of the atlas and axis. In practice, we sectioned the C2 nerve roots, controlled the developed venous plexus, fully exposed the facets, and then distracted the facets with the osteotome. Ensuring sufficient space around the facets facilitates insertion of the cylindrical titanium cage into the joint space while sustaining the distraction with the retractor. However, full exposure of the facets may not be easy, especially in patients with BI who have bone anomalies and developed venous plexus. Resection of the C2 nerve roots allows control of the venous plexus around the facet and excision of the joint capsule to safely operate between the facets of the atlantoaxial joint. Resection of the C2 nerve root may cause occipital numbness along the distribution of the nerve, but the area of numbness usually reduces over the years [10, 16]. In the present case, the occipital numbness markedly diminished in the year after surgery as previously described. Recently, an atlantoaxial distraction method without fusion of the atlantoaxial joint was reported for the treatment of BI [16]. The vertical subluxation is reduced without exposure of the atlantoaxial joint by distracting between the occiput and the C2 pedicle screw. This procedure without exposure of the atlantoaxial joint decreases the risk of hemorrhage from the
venous plexus and makes sectioning of C2 nerve root unnecessary. However, we are concerned about the shortening of the atlantoaxial joint, instrument failure, and loss of correction of occipitocervical alignment over the long term, because the atlantoaxial joint remains unfixed with free space. Adequate fusion of the corrected or distracted atlantoaxial joint is critical for the maintenance of reduction of the BI and stability of the reconstruction. The atlantoaxial distraction method for BI is intended to relieve odontoid invagination coupled with occipitocervical or atlantoaxial fusion. However, the manipulation to translocate the odontoid process downward might affect the fragile spinal cord or medulla oblongata in patients with severe neurological impairment or marked compression of the brainstem/spinal cord. In the present case, we did not monitor neurological function such as motor-evoked potential and somatosensoryevoked potential because she had mild neurological impairment, but incorporation of such monitoring might have been desirable to increase the safety of the procedure. Therefore, this procedure should be performed under intraoperative radiological control, possibly with neurological monitoring, especially in a patient with severe neurological impairment or marked brainstem compression. This procedure can be safely and easily performed under such intraoperative monitoring, resulting in reduction of the BI with adequate bone fusion of the atlantoaxial joint using the cylindrical titanium cage. Consequently, this technique is a useful option in posterior occipitocervical or atlantoaxial fusion surgery for BI. Long-term assessment by cervical spine radiography, CT, and MR imaging is important to detect alignment change over time. Further experience with selected cases will validate the suitability of this procedure including the long-term stability.
Conclusion Atlantoaxial distraction using a cylindrical titanium cage can relieve odontoid invagination coupled with posterior occipitocervical or atlantoaxial fusion and is a useful option in posterior fusion surgery for BI.
References 1. Abumi K, Takada T, Shono Y, Kaneda K, Fujiya M (1999) Posterior occipitocervical reconstruction using cervical pedicle screws and plate-rod systems. Spine (Phila Pa 1976) 24:1425–1434 2. Bundschuh C, Modic MT, Kearney F, Morris R, Deal C (1988) Rheumatoid arthritis of the cervical spine: surface-coil MR imaging. AJR Am J Roentgenol 151:181–187 3. Dickman CA, Locantro J, Fessler RG (1992) The influence of transoral odontoid resection on stability of the craniovertebral junction. J Neurosurg 77:525–530
Neurosurg Rev 4. Elliott RE, Tanweer O, Smith ML, Frempong-Boadu A (2014) Impact of starting point and bicortical purchase of C1 lateral mass screws on atlantoaxial fusion: meta-analysis and review of the literature. J Spinal Disord Tech. doi:10.1097/BSD.0b013e31828ffc97 5. Fukui K, Kataoka O, Sho T, Sumi M (1990) Pathomechanism, pathogenesis, and results of treatment in cervical spondylotic myelopathy caused by dynamic canal stenosis. Spine (Phila Pa 1976) 15: 1148–1152 6. Goel A, Laheri V (1994) Plate and screw fixation for atlanto-axial subluxation. Acta Neurochir (Wien) 129:47–53 7. Goel A, Bhatjiwale M, Desai K (1998) Basilar invagination: a study based on 190 surgically treated patients. J Neurosurg 88:962–968 8. Goel A (2004) Treatment of basilar invagination by atlantoaxial joint distraction and direct lateral mass fixation. J Neurosurg Spine 1:281– 286 9. Goel A, Shah A (2008) Atlantoaxial joint distraction as a treatment for basilar invagination: a report of an experience with 11 cases. Neurol India 56:144–150 10. Goel A, Shah A (2009) Reversal of longstanding musculoskeletal changes in basilar invagination after surgical decompression and stabilization. J Neurosurg Spine 10:220–227 11. Grob D, Dvorak J, Panjabi MM, Antinnes JA (1994) The role of plate and screw fixation in occipitocervical fusion in rheumatoid arthritis. Spine (Phila Pa 1976) 19:2545–2551 12. Grob D, Schutz U, Plotz G (1999) Occipitocervical fusion in patients with rheumatoid arthritis. Clin Orthop Relat Res 366:46–53 13. Hacker RJ, Cauthen JC, Gilbert TJ, Griffith SL (2000) A prospective randomized multicenter clinical evaluation of an anterior cervical fusion cage. Spine (Phila Pa 1976) Spine (Phila Pa 1976) 25:2646– 2654, discussion 2655 14. Harms J, Melcher RP (2001) Posterior C1-C2 fusion with polyaxial screw and rod fixation. Spine (Phila Pa 1976) 26:2467–2471 15. Hida K, Iwasaki Y, Yano S, Akino M, Seki T (2008) Long-term follow-up results in patients with cervical disk disease treated by cervical anterior fusion using titanium cage implants. Neurol Med Chir (Tokyo) 48:440–446, discussion 446 16. Jian FZ, Chen Z, Wrede KH, Samii M, Ling F (2010) Direct posterior reduction and fixation for the treatment of basilar invagination with atlantoaxial dislocation. Neurosurgery 66:678–687, discussion 687 17. Kadoya S (1992) Grading and scoring system for neurological function in degenerative cervical spine disease—Neurosurgical Cervical Spine Scale. Neurol Med Chir (Tokyo) 32:40–41 18. Menezes AH, VanGilder JC (1988) Transoral-transpharyngeal approach to the anterior craniocervical junction. Ten-year experience with 72 patients. J Neurosurg 69:895–903 19. Nagashima C, Kubota S (1983) Craniocervical abnormalities. Modern diagnosis and a comprehensive surgical approach. Neurosurg Rev 6:187–197 20. Nishikawa M, Ohata K, Baba M, Terakawa Y, Hara M (2004) Chiari I malformation associated with ventral compression and instability: one-stage posterior decompression and fusion with a new instrumentation technique. Neurosurgery 54:1430–1434, discussion 1434– 1435 21. Nockels RP, Shaffrey CI, Kanter AS, Azeem S, York JE (2007) Occipitocervical fusion with rigid internal fixation: long-term follow-up data in 69 patients. J Neurosurg Spine 7:117–123 22. Patel AJ, Boatey J, Muns J, Bollo RJ, Whitehead WE, Giannoni CM, Jea A (2012) Endoscopic endonasal odontoidectomy in a child with chronic type 3 atlantoaxial rotatory fixation: case report and literature review. Childs Nerv Syst 28:1971–1975 23. Sandhu FA, Pait TG, Benzel E, Henderson FC (2003) Occipitocervical fusion for rheumatoid arthritis using the insideoutside stabilization technique. Spine (Phila Pa 1976) 28: 414–419 24. Vale FL, Oliver M, Cahill DW (1999) Rigid occipitocervical fusion. J Neurosurg 91(2 Suppl):144–150
25. Zileli M, Cagli S (2002) Combined anterior and posterior approach for managing basilar invagination associated with type I Chiari malformation. J Spinal Disord Tech 15:284–289
Comments Atul Goel, Mumbai, India Basilar invagination is a manifestation of ‘vertical’ atlantoaxial instability [12]. Incompetence of the muscles of the nape of the neck secondary to trauma or poor muscle nutrition may be the pathogenetic cause. Listhesis of the facet of atlas over the facet of axis results in superior and posterior migration of the odontoid process in relationship to the arch of atlas resulting in basilar invagination and atlantoxial dislocation [14]. The atlantoaxial dislocation in such cases is not freely mobile and reducible and was earlier referred to as ‘fixed’ atlantoaxial dislocation [7]. The most defining feature that probably revolutionised the treatment of ‘basilar invagination’ was the identification of the fact that atlantoaxial joints in such cases are not fixed but are functional and mobile and, more importantly, are reducible [1, 5, 9]. Instability of the atlantoaxial joint and microtrauma inflicted to critical neural structures by repeated abnormal movements of the odontoid process are the cause of neurological deficits and are more important than structural malformation or deformation that it results [9]. The subtleness and long-standing nature of process of listhesis result in remarkable natural readjustments that lead to a host of musculoskeletal and neural alterations, all aimed at reducing the impact of instability and in reducing the neural compromise. Torticollis, short neck, platybasia, bone fusions and several similar morphological alterations that are frequently observed in cases with basilar invagination are all potentially reversible following surgical procedure that stabilizes the atlantoaxial joint [9]. Opening of the atlantoaxial joint, denuding of the articular cartilage, stuffing of bone graft within the confines of the atlantoaxial joint and subsequent plate/rod and screw fixation of C1 and C2 pars/pedicle/facets form the basis of our fixation technique [6, 8]. The description of feasibility and safety of sectioning of the C2 ganglion, whenever necessary, to obtain wide exposure of the region to complete all the steps of the fixation technique is another crucial step in the advancement of surgery in the craniovertebral region [4]. The exposure of the atlantoaxial joint in cases with basilar invagination is significantly more difficult when compared to normally located joints. The joints are rostrally located and dissection in the region amidst large venous complexes can be tedious. Sectioning of C2 ganglion, particularly in such cases, can assist in providing a panoramic view to the joint and facets so that the entire surgical procedure can be done under direct surgical vision. Distraction of facets of the spine by employing metal spacers is emerging to be a robust technique for provision of stability and realignment [10, 11]. Impaction of metal spacer within the atlantoaxial joint provides significant stability to the region [2]. Distraction of the facets by the spacers, at the site of fulcrum of craniovertebral movements, results in reduction of basilar invagination and restoration of craniovertebral and spinal alignment [4, 13]. However, as our experience in the treatment of basilar invagination in increasing, we have realised that it is more important to obtain stability of the atlantoaxial region than to aim at morphological reduction in basilar invagination. With that aim in mind, introduction of bone graft within the confines of the joint and in the appropriately prepared suboccipital region is crucially important. The authors in the present manuscript have resorted to inclusion of the occipital bone in the fusion construct. The use of short plates/rods and segmental fixation at the point of fulcrum of movements as is done for atlantoaxial fixation is biomechanically far superior when compared to the use of long plates/rods necessary for occipitocervical fixation. The use of long length screws as is possible in the strong and largely cortical bone facets of atlas and axis is much more robust
Neurosurg Rev when compared to the use of multiple short screws in the suboccipital squama. Inclusion of the occipital bone and sub-axial spinal segment not only is unnecessary, but can significantly reduce the strength of the implant and adversely affect the neck movements and neck growth [3]. Manipulation of the facets that is the point of pathogenesis of basilar invagination is far more effective than remote manipulation of the occipital bone. Although the technique of exposure of the atlantoaxial joint is relatively difficult and tedious, if learnt appropriately and performed adequately, it can lead to gratifying surgical results in this relatively complex and daunting clinical situation. References 1. Goel A (2004) Treatment of basilar invagination by atlantoaxial joint distraction and direct lateral mass fixation. J Neurosurg Spine.1(3):281–6. 2. Goel A (2007) Atlantoaxial joint jamming as a treatment for atlantoaxial dislocation: a preliminary report. Technical note. J Neurosurg Spine.7(1):90–4. 3. Goel A (2010) Occipitocervical fixation—is it necessary? Editorial, J Neurosurg Spine. 13(1):1–2. 4. Goel A (2012) Cervical ganglion 2 (CG2) neurectomy: a window to the atlantoaxial joint. World Neurosurg.78(1–2):78–9 5. Goel A, Bhatjiwale M, Desai K (1988) Basilar invagination: a study based on 190 surgically treated cases. J Neurosurg 88:962–968.
6. Goel A, Desai K, Muzumdar D (2002) Atlantoaxial fixation using plate and screw method: a report of 160 treated patients. Neurosurgery 51; 1351–1357. 7. Goel A, Kulkarni AG, Sharma P (2005) Reduction of fixed atlantoaxial dislocation in 24 cases: technical note. J Neurosurg Spine 2(4):505–9. 8. Goel A, Laheri VK (1994) Plate and screw fixation for atlanto-axial dislocation. (technical report). Acta Neurochir (Wien) 129:47–53. 9. Goel A, Shah A (2009) Reversal of longstanding musculoskeletal changes in basilar invagination after surgical decompression and stabilization. J Neurosurg Spine.10(3):220–7. 10. Goel A, Shah A (2011) Facetal distraction as treatment for singleand multilevel cervical spondylotic radiculopathy and myelopathy: a preliminary report. J Neurosurg Spine 14(6):689–96. 11. Goel A, Shah A, Jadhav M, Nama S (2013) Distraction of facets with intraarticular spacers as treatment for lumbar canal stenosis: report on a preliminary experience with 21 cases. J Neurosurg Spine 19(6):672–7. 12. Goel A, Shah A, Rajan S (2009) Vertical mobile and reducible atlantoaxial dislocation. Clinical article. J Neurosurg Spine 11(1):9–14. 13. Goel A, Sharma P. (2005) Craniovertebral junction realignment for the treatment of basilar invagination with syringomyelia: preliminary report of 12 cases. Neurol Med Chir (Tokyo) 45(10):512–8. 14. Kothari M, Goel A (2007) Transatlantic odonto-occipital listhesis: the so-called basilar invagination. Neurol India 55(1):6–7.
