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C1 Titanium Cables Combined with C2 Pedicle Screw-Rod Fixation for Atlantoaxial Instability Not Suitable for Placement of C1 Screws
Original Article
C1 Titanium Cables Combined with C2 Pedicle Screw-Rod Fixation for Atlantoaxial Instability Not Suitable for Placement of C1 Screws Jie-Hong Zhang, Zhi-Jing Zhang, Ya Zhu, Jian-Dong Shi, Bin Li, Yi-Sheng Lu
OBJECTIVE: We sought to develop a new posterior fusion technique composed of bilateral C1 titanium cables and C2 pedicle screw-rods for treatment of atlantoaxial instability not suitable for C1 screw placement.
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METHODS: A study was conducted of 18 patients with atlantoaxial instability who had C1 broken screw trajectory or anatomic anomalies. All patients underwent posterior fixation with bilateral C1 titanium cables and C2 pedicle screws. The follow-up period was a minimum 1 year. Clinical outcomes measurements included visual analog scale score for neck pain assessment, the American Spinal Injury Association Impairment Scale and Japanese Orthopaedic Association score for neurologic status and function. According to preoperative computed tomography (CT) reconstruction and CT angiography, the patients selected in this study were not suitable for C1 screw placement. Postoperative plain radiographs and CT reconstruction were performed to evaluate the reduction, bony fusion, and implant position. All outcomes were evaluated at each follow-up.
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RESULTS: The average clinical follow-up period was 24 months (range 12e36 months). All patients had complete neck pain relief at postoperative 6 months. Their neurologic symptoms had improved significantly at 1-year follow-up. Radiologic outcomes indicated good bony fusion and construction stability in all patients without implant failure at the last follow-up. No neural or vascular complications related to this technique were observed.
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Key words Atlantoaxial instability - Screw-rod constructs - Spinal fusion - Titanium cable -
Abbreviations and Acronyms ASIA: American Spinal Injury Association CT: Computed tomography JOA: Japanese Orthopaedic Association VA: Vertebral artery
CONCLUSIONS: Posterior atlantoaxial fixation using C1 titanium cables and C2 pedicle screw-rod construct appears to be an effective and safe technique for treatment of atlantoaxial instability, which could be an alternative method for cases unsuitable for C1 screw placement when using C1-C2 screw fixation.
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INTRODUCTION
A
tlantoaxial instability is often found in patients with upper cervical spine diseases, which can be caused by trauma, tumor, congenital malformation, or inflammation.1 Various posterior fixation methods have been developed including wiring, clamps, and screw techniques.2,3 Among them, C1-C2 pedicle screw fixation has become the most popular fixation technique in recent years because of its high fusion rates near 100%.4 However, it is not suitable for placement of C1 lateral mass screws in some patients when broken screw trajectory and anatomic anomalies are present, like the anomalous vertebral artery (VA) and posterior arch.5,6 To solve this problem, we developed a supplementary technique of C1-C2 stabilization using the modified Brooks technique combined with C2 pedicle screws. We modified the traditional Brooks technique by securing the posterior structural bone graft with the C1 titanium cable and C2 screw-rod construct instead of C1-C2 cable fixation for atlantoaxial fusion. This new technique has been applied in 18 patients since 2014. Herein, the fixation technique was described and the clinical outcome was evaluated.
Spine Center, the Department of Orthopedics, the 117th Hospital of PLA, Hangzhou, Zhejiang, China To whom correspondence should be addressed: Yi-Sheng Lu, M.D. [E-mail: [email protected]] Jie-Hong Zhang and Zhi-Jing Zhang contributed equally to this work and should be considered coefirst authors. Citation: World Neurosurg. (2018). https://doi.org/10.1016/j.wneu.2018.08.103 Journal homepage: www.WORLDNEUROSURGERY.org Available online: www.sciencedirect.com 1878-8750/$ - see front matter ª 2018 Elsevier Inc. All rights reserved.
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ORIGINAL ARTICLE JIE-HONG ZHANG ET AL.
C1 CABLES AND C2 SCREW-ROD FIXATION FOR ATLANTOAXIAL INSTABILITY
MATERIAL AND METHODS Patients From February 2014 to December 2016, 18 consecutive patients (13 men, 5 women) with atlantoaxial instability were included in this study: 9 cases with broken C1 lateral mass screw trajectory, 5 cases with anomalous posterior arch, and 4 cases with anomalous VA. Their ages ranged from 35e62 years (average age, 46.5 years). All patients presented with mechanical upper cervical neck pain, and their neurologic deficits were assessed by a neurologic examination with the American Spinal Injury Association (ASIA) impairment scale.7 Preoperative imaging including plain radiographs with flexion and extension views (except for patients with acute cervical fractures), computed tomography (CT) (including sagittal and coronal reconstructions), and magnetic resonance imaging were performed for each patient. A CT angiography with sagittal and coronal reconstructions was used to assess VA anomalies. Skull traction was performed for 1 week in each patient preoperatively (3.0e4.0 kg). Surgical Procedure The fixation system used during the surgery was designed by our research group. All the implants were manufactured in China. The fixation system consists of braided titanium cables, polyaxial screws, and rods. Each surgical procedure was performed by the same senior surgeon. Under general anesthesia, the patient was placed in prone position with the head and cervical spine maintained in the neutral position using the head holder. C1-C2 reduction was confirmed with C-arm fluoroscopy. A midline posterior incision from the occiput to C3 was done to expose the C1 facet posterior arch, C2 lamina, and C3 lamina. C2 pedicle screws (diameter, 3.5 mm; length, 25e35 mm) were inserted using the technique described by Abumi et al.8 Then the connecting rod (diameter, 3.2 mm) was loaded into the C2 pedicle screw heads on both sides. In addition, 2 braided titanium cables (diameter, 1.25 mm) were passed simultaneously under the posterior arch of the atlas and the rod. Next, the caudal rim of the posterior arch of C1, cranial edge of the C2 lamina, and C2 spinous process were decorticated by a high-speed drill. An autogenous cancellous bone graft from the posterior iliac crest was notched to fit on the decorticated elements of the C1 posterior arch and C2 lamina.9 At last, the titanium cables were tightened using the special instrument to fasten the bone graft in a stable position between the C1 posterior arch and C2 spinous process. In this process of tightening the cables, the hyperflexion alignment of the C1-C2 complex caused by the anterior dislocation of the atlas was gradually corrected. When the pressure was suitable, the locks were locked and remaining cables were cut. After C1-C2 reduction was confirmed with C-arm fluoroscopy again, the wound was closed in a standard fashion over a suction drain. Postoperative Management After surgery, the patients were immobilized in cervical collars (Philadelphia) for 3 months. CT reconstruction and plain radiographs were performed immediately after operation to assess the reduction of the atlantoaxial dislocation and position of cables, screws, and bone grafts. All patients were followed up at
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postoperative 3, 6, and 12 months and annually thereafter. At each follow-up, plain radiographs and CT reconstruction were taken to evaluate the fusion and the position of the implants. In addition, the Japanese Orthopaedic Association (JOA) and visual analog scale scores were used to assess the improvement of neurologic status and neck pain. To evaluate the clinical outcome, neurologic status and neck pain were compared between preoperative and the follow-up at postoperative 12 months. The paired Student’s t-test was used in statistical analysis. All P values <0.05 were considered statistically significant. RESULTS All 18 patients received a neurologic examination with the ASIA scale before surgery. Preoperative ASIA grades were C degree in 2 cases, D in 5, and E in 11. The average operation time was 122 minutes (range 102e140 minutes), and the mean blood loss was 273 mL (range 202e316 mL). No neurologic or vascular complications were noted. The mean duration of follow-up was 24 months (range 12e36 months). At the last follow-up, CT reconstruction and plain radiographs revealed bony fusion in all cases without loss of reduction and no implant loosening, breakage, or malposition occurred (Figure 1). Postoperative ASIA grades were E degree in all cases. All patients did not complain of neck pain at postoperative 6 months. For the relief of neck pain, the mean VAS score had reduced significantly from 7.1 preoperatively to 1.6 at 1 year follow-up (P < 0.001). For the improvement of neurologic status, the average JOA score had improved significantly from 10.6 preoperatively to 15.4 at 1-year follow-up (P < 0.001) (Table 1). The average recovery rate of JOA scores of each patient10 was 75% (74.7 9.8). DISCUSSION In this study, we introduced a new technique for posterior atlantoaxial fixation using the modified Brooks technique combined with C2 pedicle screws, which was a supplementary method for some cases not suitable for placement of C1 lateral mass screws. The results suggested that all patients receiving this surgery had good clinical outcomes and bony fusion at the final follow-ups. According to ASIA grades and JOA scores, their neurologic symptoms had improved significantly after surgery. In addition, no VA or spinal cord injuries occurred intraoperatively and postoperatively. At present, a variety of techniques for posterior atlantoaxial fixation have been described, like wiring, transarticular screws, and screw-rod fixation techniques.11-13 In terms of wiring fixation techniques, the traditional Brooks and Gallie techniques are easy to accomplish but sublaminar wire passage under the posterior arch and C2 lamina carries the potential risk of spinal cord injury.11,14 Notably, the C1-C2 stabilization during lateral bending and rotation is significantly inferior, so the bone fusion rate is not high.15,16 Therefore the wiring technique has been rarely used alone for atlantoaxial fixation. On the other hand, C1-C2 pedicle screw fixation has become the most popular technique for atlantoaxial fixation in recent years.17,18 Compared with wiring techniques, C1-C2 pedicle screw fixation is a safer technique because it doesn’t need the passage of sublaminar wires under posterior arch and C2 lamina, which can
WORLD NEUROSURGERY, https://doi.org/10.1016/j.wneu.2018.08.103
ORIGINAL ARTICLE JIE-HONG ZHANG ET AL.
C1 CABLES AND C2 SCREW-ROD FIXATION FOR ATLANTOAXIAL INSTABILITY
Figure 1. A 40-year-old female with odontoid fracture combined with atlantoaxial instability. (A and B) Preoperative lateral radiograph and 3-dimensional computed tomography (CT) images show odontoid fracture combined with atlantoaxial instability. (C) Roentgenograph after skull traction shows reposition
minimize the risk of injury to spinal cord. In addition, the technique can provide immediate rigid fixation of the C1-C2 complex, offering higher fusion rates and less need for adjunctive postoperative immobilization.19,20 However, this technique also has some drawbacks. It is well known that if the height of C1 pedicle (the vertebral artery groove) is <4 mm, the technique cannot be applied.21,22 According to this limitation, the C1 screw technique is not feasible in approximately 8%e53.8% of patients.22-25
Table 1. Clinical Outcomes of 18 Cases with Atlantoaxial Instability Undergoing Posterior C1eC2 Fixation and Fusion with Bilateral C1 Titanium Cables and C2 Pedicle Screws Preoperative
1-Year Follow-up
P Value
VAS score*
7.1 0.8
1.6 0.6
<0.001
JOA score*
10.6 1.5
15.4 0.7
<0.001
VAS, visual analog scale; JOA, Japanese Orthopaedic Association. *Mean standard deviation.
WORLD NEUROSURGERY -: e1-e4, - 2018
of C1-C2 and odontoid fracture. (D and E) Postoperative plain radiographs show normal C1-C2 alignment. (F) Three-dimensional CT at postoperative 13 months shows good positioning of titanium cables, screw rods, and bone graft with solid fusion after posterior atlantoaxial fixation.
Otherwise, for some cases with broken C1 lateral mass screw trajectory and anomalous VA or posterior arch, it is also not suitable for placement of C1 screws.5,6 Notably, this technique is more technically demanding; for surgeons without sufficient experience of C1 lateral mass screw placement, broken C1 screw trajectory occurs sometimes. Under the situations mentioned earlier, a supplementary technique for atlantoaxial fixation is an urgent need. This paper describes a new method of atlantoaxial fixation that uses a titanium cable-screw system, which relies on the posterior arch-cable-rod interface and the pullout strength of C2 pedicle screws to maintain the stability of the atlantoaxial joint. With the combined application of titanium cables and pedicle screws, its biomechanical stability is significantly superior to that of the traditional Brooks technique fixation for lateral bending and rotation.14 Although it has less immediate stability compared with C1-C2 pedicle screw fixation, this technique makes the C1 posterior arch rigidly secured to the rod connected with bilateral C2 pedicle screws, which can be seen as a pivot point fixation construct. In this environment, bone fusion could be achieved safely for the long-term stability. Our clinical results confirmed
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ORIGINAL ARTICLE JIE-HONG ZHANG ET AL.
C1 CABLES AND C2 SCREW-ROD FIXATION FOR ATLANTOAXIAL INSTABILITY
that this supplementary technique could provide adequate biomechanical stability for posterior atlantoaxial fixation, in cases wherein the placement of C1 lateral mass screws was not feasible. The indications for this new technique include C1eC2 instability due to trauma (like odontoid fractures with type II or III), failure of the transarticular screw or C1 lateral mass screw placement, and broken C1 screw trajectory or anatomic anomalies (anomalous VA, C1 lateral mass, and posterior arch) that are not suitable for C1 screw fixation technique. It also has some contraindications including failure of C1eC2 reduction and fractures of the C1 posterior arch or C2 screw trajectory. To the author’s knowledge, no studies using the similar technique have been reported previously. In this study, all 18 cases treated using this fixation technique achieved excellent clinical outcomes at the last follow-up after surgery, with good bony fusion and significant improvement of neurologic function. No neurologic or vascular injuries happened during surgery.
REFERENCES 1. Huang DG, Hao DJ, He BR, Wu QN, Liu TJ, Wang XD, et al. Posterior atlantoaxial fixation: a review of all techniques. Spine J. 2015;15:2271-2281. 2. Jacobson ME, Khan SN, An HS. C1-C2 posterior fixation: indications, technique, and results. Orthop Clin North Am. 2012;43:11-18. 3. Ni B, Zhou F, Xie N, Guo X, Yang L, Guo Q, et al. Transarticular screw and C1 hook fixation for os odontoideum with atlantoaxial dislocation. World Neurosurg. 2011;75:540-546. 4. Elliott RE, Tanweer O, Boah A, Morsi A, Ma T, Smith ML, et al. Atlantoaxial fusion with screwrod constructs: meta-analysis and review of literature. World Neurosurg. 2014;81:411-421. 5. Tan M, Wang H, Wang Y, Zhang G, Yi P, Li Z, et al. Morphometric evaluation of screw fixation in atlas via posterior arch and lateral mass. Spine. 2003;28:888-895. 6. Ebraheim NA, Xu R, Ahmad M, Heck B. The quantitative anatomy of the vertebral artery groove of the atlas and its relation to the posterior atlantoaxial approach. Spine. 1998;23:320-323.
Otherwise, its good biomechanical stability was also reported in a biomechanical 3-dimensional finite element research performed by us (unpublished data). Therefore the use of modified Brooks technique combined with C2 pedicle screw fixation is effective and safe for posterior atlantoaxial fixation. However, in terms of the limitation of wiring fixation, the biomechanical stability at C1-C2 rotation using this fixation may be inferior to that using C1-C2 pedicle screw fixation or transarticular screw fixation, so further studies with larger sample size and longer follow-up are needed. CONCLUSIONS The modified Brooks technique combined with C2 pedicle screws could be used as a new and supplementary fixation method for atlantoaxial instability, especially for cases not suitable for placement of C1 screws. The preliminary clinical follow-up data suggest that this fixation technique is effective and safe.
10. Hirabayashi K, Miyakawa J, Satomi K, Maruyama T, Wakano K. Operative results and postoperative progression of ossification among patients with ossification of cervical posterior longitudinal ligament. Spine. 1981;6:354-364.
20. Elliott RE, Tanweer O, Smith ML, Frempongboadu A. 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. 2015;28:242-253.
11. Gallie WE. Fractures and dislocations of the cervical spine. Am J Surg. 1939;46:495-499.
21. Lin JM, Hipp JA, Reitman CA. C1 lateral mass screw placement via the posterior arch: a technique comparison and anatomic analysis. Spine J. 2013;13:1549-1555.
12. Jeanneret B, Magerl F. Primary posterior fusion C1/2 in odontoid fractures: indications, technique, and results of transarticular screw fixation. J Spinal Disord. 1992;5:464-475. 13. Harms J, Melcher RP. Posterior C1-C2 fusion with polyaxial screw and rod fixation. Spine. 2001;26: 2467-2471.
22. Ma XY, Yin QS, Wu ZH, Xia H, Liu JF, Zhong SZ. Anatomic considerations for the pedicle screw placement in the first cervical vertebra. Spine. 2005;30:1519-1523.
14. Brooks AL, Jenkins EB. Atlanto-axial arthrodesis by the wedge compression method. J Bone Joint Surg Am. 1978;60:279-284.
23. Gebauer M, Barvencik F, Briem D, Kolb JP, Seitz S, Rueger JM, et al. Evaluation of anatomic landmarks and safe zones for screw placement in the atlas via the posterior arch. Eur Spine J. 2010;19: 85-90.
15. Coyne TJ, Fehlings MG, Wallace MC, Bernstein M, Tator CH. C1-C2 posterior cervical fusion: longterm evaluation of results and efficacy. Neurosurgery. 1995;37:688-692.
24. Christensen DM, Eastlack RK, Lynch JJ, Yaszemski MJ, Currier BL. C1 anatomy and dimensions relative to lateral mass screw placement. Spine. 2007;32:844-848.
16. Richter M, Schmidt R, Claes L, Puhl W, Wilke HJ. Posterior atlantoaxial fixation: biomechanical in vitro comparison of six different techniques. Spine. 2002;27:1724-1732.
25. Blagg SE, Don AS, Robertson PA. Anatomic determination of optimal entry point and direction for C1 lateral mass screw placement. J Spinal Disord Tech. 2009;22:233-239.
7. Roberts TT, Leonard GR, Cepela DJ. Classifications in brief: American Spinal Injury Association (ASIA) Impairment Scale. Clin Orthop Relat Res. 2017;475:1499-1504.
17. Resnick D, Benzel E. C1-C2 pedicle screw fixation with rigid cantilever beam construct: case report and technical note. Neurosurgery. 2002;50:426-428.
8. Abumi K, Takada T, Shono Y, Kaneda K, Fujiya M. Posterior occipitocervical reconstruction using cervical pedicle screws and plate-rod systems. Spine. 1999;24:1425-1434.
18. Yeom JS, Kafle D, Nguyen NQ, Noh W, Park KW, Chang BS, et al. Routine insertion of the lateral mass screw via the posterior arch for C1 fixation: feasibility and related complications. Spine J. 2012; 12:476-483.
9. Dickman CA, Sonntag VK, Papadopoulos SM, Hadley MN. The interspinous method of posterior atlantoaxial arthrodesis. J Neurosurg. 1991;74: 190-198.
19. Ma C, Wu J, Zhao M, Dai W, Wu D, Wang Z, et al. Treatment of upper cervical spine instability with posterior fusion plus atlantoaxial pedicle screw. Cell Biochem Biophys. 2014;69:693-697.
Conflict of interest statement: This work was supported by Health and Family Planning Commission of Hangzhou Municipality (grant 2017Z11). Received 6 May 2018; accepted 13 August 2018 Citation: World Neurosurg. (2018). https://doi.org/10.1016/j.wneu.2018.08.103 Journal homepage: www.WORLDNEUROSURGERY.org
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Available online: www.sciencedirect.com 1878-8750/$ - see front matter ª 2018 Elsevier Inc. All rights reserved.
WORLD NEUROSURGERY, https://doi.org/10.1016/j.wneu.2018.08.103
C1 Titanium Cables Combined with C2 Pedicle Screw-Rod Fixation for Atlantoaxial Instability Not Suitable for Placement of C1 Screws Jie-Hong Zhang, Zhi-Jing Zhang, Ya Zhu, Jian-Dong Shi, Bin Li, Yi-Sheng Lu
OBJECTIVE: We sought to develop a new posterior fusion technique composed of bilateral C1 titanium cables and C2 pedicle screw-rods for treatment of atlantoaxial instability not suitable for C1 screw placement.
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METHODS: A study was conducted of 18 patients with atlantoaxial instability who had C1 broken screw trajectory or anatomic anomalies. All patients underwent posterior fixation with bilateral C1 titanium cables and C2 pedicle screws. The follow-up period was a minimum 1 year. Clinical outcomes measurements included visual analog scale score for neck pain assessment, the American Spinal Injury Association Impairment Scale and Japanese Orthopaedic Association score for neurologic status and function. According to preoperative computed tomography (CT) reconstruction and CT angiography, the patients selected in this study were not suitable for C1 screw placement. Postoperative plain radiographs and CT reconstruction were performed to evaluate the reduction, bony fusion, and implant position. All outcomes were evaluated at each follow-up.
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RESULTS: The average clinical follow-up period was 24 months (range 12e36 months). All patients had complete neck pain relief at postoperative 6 months. Their neurologic symptoms had improved significantly at 1-year follow-up. Radiologic outcomes indicated good bony fusion and construction stability in all patients without implant failure at the last follow-up. No neural or vascular complications related to this technique were observed.
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Key words Atlantoaxial instability - Screw-rod constructs - Spinal fusion - Titanium cable -
Abbreviations and Acronyms ASIA: American Spinal Injury Association CT: Computed tomography JOA: Japanese Orthopaedic Association VA: Vertebral artery
CONCLUSIONS: Posterior atlantoaxial fixation using C1 titanium cables and C2 pedicle screw-rod construct appears to be an effective and safe technique for treatment of atlantoaxial instability, which could be an alternative method for cases unsuitable for C1 screw placement when using C1-C2 screw fixation.
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INTRODUCTION
A
tlantoaxial instability is often found in patients with upper cervical spine diseases, which can be caused by trauma, tumor, congenital malformation, or inflammation.1 Various posterior fixation methods have been developed including wiring, clamps, and screw techniques.2,3 Among them, C1-C2 pedicle screw fixation has become the most popular fixation technique in recent years because of its high fusion rates near 100%.4 However, it is not suitable for placement of C1 lateral mass screws in some patients when broken screw trajectory and anatomic anomalies are present, like the anomalous vertebral artery (VA) and posterior arch.5,6 To solve this problem, we developed a supplementary technique of C1-C2 stabilization using the modified Brooks technique combined with C2 pedicle screws. We modified the traditional Brooks technique by securing the posterior structural bone graft with the C1 titanium cable and C2 screw-rod construct instead of C1-C2 cable fixation for atlantoaxial fusion. This new technique has been applied in 18 patients since 2014. Herein, the fixation technique was described and the clinical outcome was evaluated.
Spine Center, the Department of Orthopedics, the 117th Hospital of PLA, Hangzhou, Zhejiang, China To whom correspondence should be addressed: Yi-Sheng Lu, M.D. [E-mail: [email protected]] Jie-Hong Zhang and Zhi-Jing Zhang contributed equally to this work and should be considered coefirst authors. Citation: World Neurosurg. (2018). https://doi.org/10.1016/j.wneu.2018.08.103 Journal homepage: www.WORLDNEUROSURGERY.org Available online: www.sciencedirect.com 1878-8750/$ - see front matter ª 2018 Elsevier Inc. All rights reserved.
WORLD NEUROSURGERY -: e1-e4, - 2018
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ORIGINAL ARTICLE JIE-HONG ZHANG ET AL.
C1 CABLES AND C2 SCREW-ROD FIXATION FOR ATLANTOAXIAL INSTABILITY
MATERIAL AND METHODS Patients From February 2014 to December 2016, 18 consecutive patients (13 men, 5 women) with atlantoaxial instability were included in this study: 9 cases with broken C1 lateral mass screw trajectory, 5 cases with anomalous posterior arch, and 4 cases with anomalous VA. Their ages ranged from 35e62 years (average age, 46.5 years). All patients presented with mechanical upper cervical neck pain, and their neurologic deficits were assessed by a neurologic examination with the American Spinal Injury Association (ASIA) impairment scale.7 Preoperative imaging including plain radiographs with flexion and extension views (except for patients with acute cervical fractures), computed tomography (CT) (including sagittal and coronal reconstructions), and magnetic resonance imaging were performed for each patient. A CT angiography with sagittal and coronal reconstructions was used to assess VA anomalies. Skull traction was performed for 1 week in each patient preoperatively (3.0e4.0 kg). Surgical Procedure The fixation system used during the surgery was designed by our research group. All the implants were manufactured in China. The fixation system consists of braided titanium cables, polyaxial screws, and rods. Each surgical procedure was performed by the same senior surgeon. Under general anesthesia, the patient was placed in prone position with the head and cervical spine maintained in the neutral position using the head holder. C1-C2 reduction was confirmed with C-arm fluoroscopy. A midline posterior incision from the occiput to C3 was done to expose the C1 facet posterior arch, C2 lamina, and C3 lamina. C2 pedicle screws (diameter, 3.5 mm; length, 25e35 mm) were inserted using the technique described by Abumi et al.8 Then the connecting rod (diameter, 3.2 mm) was loaded into the C2 pedicle screw heads on both sides. In addition, 2 braided titanium cables (diameter, 1.25 mm) were passed simultaneously under the posterior arch of the atlas and the rod. Next, the caudal rim of the posterior arch of C1, cranial edge of the C2 lamina, and C2 spinous process were decorticated by a high-speed drill. An autogenous cancellous bone graft from the posterior iliac crest was notched to fit on the decorticated elements of the C1 posterior arch and C2 lamina.9 At last, the titanium cables were tightened using the special instrument to fasten the bone graft in a stable position between the C1 posterior arch and C2 spinous process. In this process of tightening the cables, the hyperflexion alignment of the C1-C2 complex caused by the anterior dislocation of the atlas was gradually corrected. When the pressure was suitable, the locks were locked and remaining cables were cut. After C1-C2 reduction was confirmed with C-arm fluoroscopy again, the wound was closed in a standard fashion over a suction drain. Postoperative Management After surgery, the patients were immobilized in cervical collars (Philadelphia) for 3 months. CT reconstruction and plain radiographs were performed immediately after operation to assess the reduction of the atlantoaxial dislocation and position of cables, screws, and bone grafts. All patients were followed up at
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postoperative 3, 6, and 12 months and annually thereafter. At each follow-up, plain radiographs and CT reconstruction were taken to evaluate the fusion and the position of the implants. In addition, the Japanese Orthopaedic Association (JOA) and visual analog scale scores were used to assess the improvement of neurologic status and neck pain. To evaluate the clinical outcome, neurologic status and neck pain were compared between preoperative and the follow-up at postoperative 12 months. The paired Student’s t-test was used in statistical analysis. All P values <0.05 were considered statistically significant. RESULTS All 18 patients received a neurologic examination with the ASIA scale before surgery. Preoperative ASIA grades were C degree in 2 cases, D in 5, and E in 11. The average operation time was 122 minutes (range 102e140 minutes), and the mean blood loss was 273 mL (range 202e316 mL). No neurologic or vascular complications were noted. The mean duration of follow-up was 24 months (range 12e36 months). At the last follow-up, CT reconstruction and plain radiographs revealed bony fusion in all cases without loss of reduction and no implant loosening, breakage, or malposition occurred (Figure 1). Postoperative ASIA grades were E degree in all cases. All patients did not complain of neck pain at postoperative 6 months. For the relief of neck pain, the mean VAS score had reduced significantly from 7.1 preoperatively to 1.6 at 1 year follow-up (P < 0.001). For the improvement of neurologic status, the average JOA score had improved significantly from 10.6 preoperatively to 15.4 at 1-year follow-up (P < 0.001) (Table 1). The average recovery rate of JOA scores of each patient10 was 75% (74.7 9.8). DISCUSSION In this study, we introduced a new technique for posterior atlantoaxial fixation using the modified Brooks technique combined with C2 pedicle screws, which was a supplementary method for some cases not suitable for placement of C1 lateral mass screws. The results suggested that all patients receiving this surgery had good clinical outcomes and bony fusion at the final follow-ups. According to ASIA grades and JOA scores, their neurologic symptoms had improved significantly after surgery. In addition, no VA or spinal cord injuries occurred intraoperatively and postoperatively. At present, a variety of techniques for posterior atlantoaxial fixation have been described, like wiring, transarticular screws, and screw-rod fixation techniques.11-13 In terms of wiring fixation techniques, the traditional Brooks and Gallie techniques are easy to accomplish but sublaminar wire passage under the posterior arch and C2 lamina carries the potential risk of spinal cord injury.11,14 Notably, the C1-C2 stabilization during lateral bending and rotation is significantly inferior, so the bone fusion rate is not high.15,16 Therefore the wiring technique has been rarely used alone for atlantoaxial fixation. On the other hand, C1-C2 pedicle screw fixation has become the most popular technique for atlantoaxial fixation in recent years.17,18 Compared with wiring techniques, C1-C2 pedicle screw fixation is a safer technique because it doesn’t need the passage of sublaminar wires under posterior arch and C2 lamina, which can
WORLD NEUROSURGERY, https://doi.org/10.1016/j.wneu.2018.08.103
ORIGINAL ARTICLE JIE-HONG ZHANG ET AL.
C1 CABLES AND C2 SCREW-ROD FIXATION FOR ATLANTOAXIAL INSTABILITY
Figure 1. A 40-year-old female with odontoid fracture combined with atlantoaxial instability. (A and B) Preoperative lateral radiograph and 3-dimensional computed tomography (CT) images show odontoid fracture combined with atlantoaxial instability. (C) Roentgenograph after skull traction shows reposition
minimize the risk of injury to spinal cord. In addition, the technique can provide immediate rigid fixation of the C1-C2 complex, offering higher fusion rates and less need for adjunctive postoperative immobilization.19,20 However, this technique also has some drawbacks. It is well known that if the height of C1 pedicle (the vertebral artery groove) is <4 mm, the technique cannot be applied.21,22 According to this limitation, the C1 screw technique is not feasible in approximately 8%e53.8% of patients.22-25
Table 1. Clinical Outcomes of 18 Cases with Atlantoaxial Instability Undergoing Posterior C1eC2 Fixation and Fusion with Bilateral C1 Titanium Cables and C2 Pedicle Screws Preoperative
1-Year Follow-up
P Value
VAS score*
7.1 0.8
1.6 0.6
<0.001
JOA score*
10.6 1.5
15.4 0.7
<0.001
VAS, visual analog scale; JOA, Japanese Orthopaedic Association. *Mean standard deviation.
WORLD NEUROSURGERY -: e1-e4, - 2018
of C1-C2 and odontoid fracture. (D and E) Postoperative plain radiographs show normal C1-C2 alignment. (F) Three-dimensional CT at postoperative 13 months shows good positioning of titanium cables, screw rods, and bone graft with solid fusion after posterior atlantoaxial fixation.
Otherwise, for some cases with broken C1 lateral mass screw trajectory and anomalous VA or posterior arch, it is also not suitable for placement of C1 screws.5,6 Notably, this technique is more technically demanding; for surgeons without sufficient experience of C1 lateral mass screw placement, broken C1 screw trajectory occurs sometimes. Under the situations mentioned earlier, a supplementary technique for atlantoaxial fixation is an urgent need. This paper describes a new method of atlantoaxial fixation that uses a titanium cable-screw system, which relies on the posterior arch-cable-rod interface and the pullout strength of C2 pedicle screws to maintain the stability of the atlantoaxial joint. With the combined application of titanium cables and pedicle screws, its biomechanical stability is significantly superior to that of the traditional Brooks technique fixation for lateral bending and rotation.14 Although it has less immediate stability compared with C1-C2 pedicle screw fixation, this technique makes the C1 posterior arch rigidly secured to the rod connected with bilateral C2 pedicle screws, which can be seen as a pivot point fixation construct. In this environment, bone fusion could be achieved safely for the long-term stability. Our clinical results confirmed
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ORIGINAL ARTICLE JIE-HONG ZHANG ET AL.
C1 CABLES AND C2 SCREW-ROD FIXATION FOR ATLANTOAXIAL INSTABILITY
that this supplementary technique could provide adequate biomechanical stability for posterior atlantoaxial fixation, in cases wherein the placement of C1 lateral mass screws was not feasible. The indications for this new technique include C1eC2 instability due to trauma (like odontoid fractures with type II or III), failure of the transarticular screw or C1 lateral mass screw placement, and broken C1 screw trajectory or anatomic anomalies (anomalous VA, C1 lateral mass, and posterior arch) that are not suitable for C1 screw fixation technique. It also has some contraindications including failure of C1eC2 reduction and fractures of the C1 posterior arch or C2 screw trajectory. To the author’s knowledge, no studies using the similar technique have been reported previously. In this study, all 18 cases treated using this fixation technique achieved excellent clinical outcomes at the last follow-up after surgery, with good bony fusion and significant improvement of neurologic function. No neurologic or vascular injuries happened during surgery.
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Otherwise, its good biomechanical stability was also reported in a biomechanical 3-dimensional finite element research performed by us (unpublished data). Therefore the use of modified Brooks technique combined with C2 pedicle screw fixation is effective and safe for posterior atlantoaxial fixation. However, in terms of the limitation of wiring fixation, the biomechanical stability at C1-C2 rotation using this fixation may be inferior to that using C1-C2 pedicle screw fixation or transarticular screw fixation, so further studies with larger sample size and longer follow-up are needed. CONCLUSIONS The modified Brooks technique combined with C2 pedicle screws could be used as a new and supplementary fixation method for atlantoaxial instability, especially for cases not suitable for placement of C1 screws. The preliminary clinical follow-up data suggest that this fixation technique is effective and safe.
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Conflict of interest statement: This work was supported by Health and Family Planning Commission of Hangzhou Municipality (grant 2017Z11). Received 6 May 2018; accepted 13 August 2018 Citation: World Neurosurg. (2018). https://doi.org/10.1016/j.wneu.2018.08.103 Journal homepage: www.WORLDNEUROSURGERY.org
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