Treatment of Basilar Invagination by Joint Remodeling and Cage Implantation Combined with Intraoperative Cervical Traction

Treatment of Basilar Invagination by Joint Remodeling and Cage Implantation Combined with Intraoperative Cervical Traction | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Help Center Sign In Submit a Preprint Cite Share Download PDF Research Article Treatment of Basilar Invagination by Joint Remodeling and Cage Implantation Combined with Intraoperative Cervical Traction Zhe Hou, Qiang Jian, Wayne Fan, Cong Liang, Tao Fan This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-2323306/v1 This work is licensed under a CC BY 4.0 License Status: Posted Version 1 posted You are reading this latest preprint version Abstract Objective: This study aimed to explore the clinical and imaging results of lateral atlantoaxial joint remodeling, cage placement, and intraoperative traction in the treatment of basilar invagination. Methods: The clinical data of 11 patients with basilar invagination treated by lateral atlantoaxial joint remodeling, cage placement, and intraoperative traction were analyzed retrospectively. The lateral atlantoaxial joint surface was remodeled to form an inclined surface between the joints, and a cage was then placed. The combined use of these techniques corrects the clivus canal angle and simultaneously moves the dentate process downward, thus reducing the compression on the ventral surface of the brainstem. The Chamberlain line invasion, atlas-dens interval, and clivus-canal angle were measured using a preoperative and postoperative CT scan. In addition, pB-C2 and cervicomedullary angle (CMA) were measured on sagittal magnetic resonance imaging pre- and postoperatively. The clinical outcomes of all patients were assessed using the Japanese Orthopedic Association (JOA) scale. Wilcoxon test was used to compare the pre- and postoperative measurements. Results: Clinical symptoms of all patients significantly improved. The mean JOA score increased from 11.73 ± 2.45 preoperatively to 15.09 ± 1.22 postoperatively (z = –2.956, P = 0.003). No vertebral artery or dura mater injury was observed. The ventral compression of the brainstem was relieved after the operation. The mean pB-C2 decreased from 10.85 ± 2.96 postoperatively to 7.13 ± 1.38 preoperatively (z = –2.936, P = 0.003), and mean clivus-carnal angle and mean CMA increased from 137.25 ± 8.38 and 131.58 ± 9.17 preoperatively to 147.35 ± 7.55 (z = –2.934, P = 0.003) and 146.05 ± 6.36 (z = –2.934, P = 0.003) postoperatively, respectively. There were two cases of collapse of the C1 inferior articular process and one case of avulsion fracture of the C1 anterior arch. All patients achieved interarticular bone fusion. Conclusion: The cases demonstrated a safe and effective method for treating basilar invagination when atlantoaxial joint reduction is difficult during surgery. Atlantoaxial dislocation Basilar invagination Cervical traction Joint remodeling Cage insertion Figures Figure 1 Figure 2 Figure 3 Figure 4 Introduction Basilar invagination (BI) often manifests as the upward movement of the dentate process, which then compresses the brainstem. The condition presents with clinical symptoms requiring surgical treatment. In 2004, Goel divided the disease into group A (BI with atlantoaxial dislocation [AAD]) and group B (BI without AAD) [ 1 ]. The treatment strategy for BI has changed from anterior decompression and posterior fixation to posterior direct reduction and fixation regardless of whether it is group A or group B. In group A, the reduction of the odontoid process can relieve ventral compression; therefore, the reduction and fixation technology has become the most commonly used surgical method [ 2 – 4 ]. It has been proven effective in moving the odontoid process downward in patients with Group B BI via the interarticular distraction technique [ 5 , 6 ]; however, it has not been widely adopted because of the challenges posed by the technique. Therefore, in the posterior approach of BI, the surgical methods of groups A and B are the same. However, after intraoperative traction, the lateral atlantoaxial joints of some group A cases and all group B cases find it difficult to expand, which makes the dentate process descend to a proper position. In addition, the clivus canal angle (CCA) may not be corrected to an ideal degree. In our study, we improved Goel’s technology, and when it was difficult to reduce the odontoid process during the operation, we used cage implantation after joint remodeling to assist in reduction. In addition, we designed a slide rail-type headrest to facilitate accurate adjustment of traction strength during the operation. In this study, 11 cases of BI treated with this technique were retrospectively analyzed to evaluate the effectiveness of the technique, and clinical outcomes were reported. Materials And Methods Patient Population This study included 11 cases of BI treated with articular surface remodeling, cage placement, and intraoperative traction in our department from July 2019 to August 2021. All procedures were performed by the same operator (FT). The hospital ethics committee approved this study, and informed consent was obtained from all patients before surgery. Clinical data are shown in Table 1 . The study included four men and seven women with an average age of 40.5 years. All patients had neurological dysfunction, with symptoms lasting from 3 months to 7 years (average of 3.1 years). The main symptoms were neck pain in three cases (27.3%), limb weakness in five cases (45.5%), paresthesia in six cases (54.5%), and gait disorder in two cases (18.2%). The clinical status before and at least one year after the operation was assessed using the Japanese Orthopedic Association (JOA) scale. Table 1 Clinical date of patients in this group Patient Sex/age Main symptom Radiographic abnormalities JOA score Height of the cage PT LF 1 F/39 Gait disturbance BI AAD AOA KFS CM SM 12 15 10 2 F/46 Limbs weakness BI AAD AOA KFS CM SM 9 14 8 3 M/47 Limbs weakness and numbness BI AAD AOA SM 12 14 9 4 M/39 Limbs weakness and dyspnea BI AAD AOA KFS CM SM 6 13 8 5 F/28 Neck pain and paresthesia BI AAD AOA CM SM 15 17 9 6 M/45 Limbs weakness and dyspnea BI AAD AOA KFS 13 15 10 7 F/35 Gait disturbance BI AOA CM 14 17 7 8 F/25 Limbs weakness and paresthesia BI AOA SM 11 15 6 9 F/52 Paresthesia and neck pain BI AOA KFS SM 13 15 7 10 F/35 Neck pain and paresthesia BI AOA CM SM 12 15 6 11 M/55 Paresthesia BI AOA CM SM 12 16 6 AAD, atlantoaxial dislocation; AOZ, atlas occipitalization; BI, basilar invagination; KF, Klippel-Feil syndrome; M, male; F, female; PT, pretreated; LF, latest follow-up Radiological Evaluation All patients underwent a three-dimensional (3D) CT scan and magnetic resonance imaging (MRI) of the cervical spine pre- and postoperatively. The 3D CT was performed during the follow-up. The Chamberlain line invasion (CLV), atlas-dens interval (ADI), and CCA were measured on median sagittal CT pre- and postoperatively. BI was diagnosed when CLV was more than 5 mm, and AAD was diagnosed when ADI was more than 3 mm. pB-C2 and cervicomedullary angle (CMA) were measured on sagittal MR pre- and postoperatively. The CCA, pB-C2, and CMA were used to assess the degree of compression on the ventral surface of the brainstem. On a follow-up CT scan, we checked whether there was a uniform fusion mass between the C1 and C2 lateral mass joints to determine whether solid fusion was achieved. Cervical Traction and Surgical Techniques Somatosensory evoked potential (SEP), an intraoperative neuroelectrophysiological monitoring (IONM) technique, was used to monitor spinal cord function during cervical traction and operation. All patients were anesthetized by oral tracheal intubation and placed in a prone position with their heads in a neutral position. After anesthesia, we used our self-designed sliding-traction head holder to fix the head, so that both the eyes and forehead were suspended in the air to avoid the pressure on the eyes. Thereafter, we rotated the traction screw to achieve cervical traction. Afterward, we monitored the reduction of the craniocervical junction using the C-arm X-ray machine and gradually increased the traction strength, up to one-fifth of the body weight. All the cases in this group did not achieve complete reduction, and no odontoid process movement was found in five group B cases of BI after cervical traction. Using the suboccipital posterior median approach, we exposed the squamous part of the occipital bone to the C2 spinous process and vertebral lamina, separated the muscles to both sides, exposed the isthmus of the pedicle and C2 nerve root, and cauterized the venous plexus around the C2 nerve root under a microscope. Thereafter, the C2 nerve root was pulled upward using a nerve stripping ion to expose the lateral atlantoaxial joint. Afterward, the articular cartilage was excised using an ultrasonic osteotome, and an interarticular distractor was used for distraction, as we have previously described [ 7 ]. Thereafter, we observed the distance between the joint surfaces under continuous cervical traction and performed joint remodeling in cases where the joints could not be separated by a proper distance. The upper and lower articular surfaces of the lateral atlantoaxial joint were osteotomized with an ultrasonic osteotome and a laminectomy rongeur. In addition, as shown in Fig. 1 , a part of the bone at the inferior and superior articular surfaces was removed. Thereafter, a cage of appropriate height was filled with mixed autogenous bone and artificial bone and was placed between the joints of the bilateral lateral mass, and the degree of the dentate process’ downward movement was monitored by a C-arm X-ray machine (Fig. 2 ). After a satisfactory reduction of the dentate process, an occipital bone and a C2 screw were inserted. C2 pedicle screws were routinely placed during screw placement. When combined with a narrow C2 pedicle and high-riding vertebral artery, we used laminar screws or C2 subfacetal screws to replace C2 pedicle screws. Afterward, we stopped cervical traction and tightened the screws to fix the titanium connecting rod. When ADI reduction was not satisfactory, we used cantilever technology to assist in the reduction process. Statistical Analysis All parameters were expressed as mean ± standard deviation. The Wilcoxon signed-rank test was used to compare preoperative and postoperative parameters, and the significant difference was set at P < 0.05 Results Clinical Outcomes All 11 patients included in this study were successfully implanted with screws, underwent occipitocervical fusion, and had no screw invasion and vertebral artery injury. IONM showed that no patient had neurological impairment during cervical traction and surgical procedures. The mean operative time was 201.8 min (150–300 min), and the mean intraoperative bleeding volume was 160 mL (80–250 mL). The mean height of the cage was 7.8 mm (6–10 mm). Immediately after the operation, 10 patients’ neurological function improved, and one patient maintained the original state. At the last follow-up, the symptoms of 11 patients were significantly improved, and the mean JOA score increased from 11.73 ± 2.45 postoperatively to 15.09 ± 1.22 postoperatively (z = − 2.956, P = 0.003). Radiographic Results After cervical traction, the odontoid process of the 11 patients was not sufficiently reduced, six cases of BI with AAD were reduced to a certain extent, and five cases of BI without AAD did not have an obvious odontoid process downward movement. We have presented changes in average parameters pre- and postoperatively in Table 2 . Table 2 Clinical date of patients in this group Variable Preoperative Postoperative P CLV (mm) 9.96 ± 1.41 5.49 ± 2.04 0.003 ADI (mm) 3.90 ± 3.25 0.95 ± 0.54 0.013 CCA° 137.25 ± 8.38 147.35 ± 7.55 0.003 pB-C2 (mm) 10.85 ± 2.96 7.13 ± 1.38 0.003 CMA° 131.58 ± 9.17 146.05 ± 6.36 0.003 Postoperatively, all patients had a descent of dentate process (Fig. 3 , Fig. 4 ). CLV decreased from 9.96 ± 1.41 to 5.49 ± 2.04 (z = − 2.934, P = 0.003) and ADI decreased from 3.90 ± 3.25 to 0.95 ± 0.54 (z = − 2.491, P = 0.013). In all cases, the ventral compression was significantly relieved. In addition, six cases were associated with Chiari malformations and nine cases with syringomyelia; however, the degree of Chiari malformations and syringomyelia reduced after the operation. Postoperative images showed that two patients had a collapse of the C1 inferior articular surface and one patient had an avulsion fracture of the C1 anterior arch (Fig. 4 ); however, none of them had nerve injury symptoms. In addition, there was one case with severe spinal cord compression symptoms accompanied by dyspnea before the operation. A tracheotomy was performed immediately after the operation, and the tracheotomy tube was removed two weeks postoperatively after the condition was stabilized. The follow-up period ranged from 12 to 25 months (mean 19.2 months). At the most recent follow-up, the dentate process was moved downward and remained corrected in all patients, and they all showed interarticular bone fusion. No cases of screw pulling out, screw loosening, or cage displacement occurred. Discussion BI is often associated with AAD, atlantooccipital fusion, C2-3 fusion, Chiari malformations, and syringomyelia. After ventral compression is relieved and the atlantoaxial stability maintained, Chiari malformation is restored, and the syringomyelia is significantly reduced [ 8 , 9 ]. This suggests that the primary lesions of these patients often result from the dentate process pressing the medulla oblongata, while cerebellar tonsillar hernia and syringomyelia are secondary changes. Anterior ventral decompression combined with posterior fixation has been proven effective in treating BI with or without ADD [ 10 , 11 ]. With the development of this treatment strategy and continuous improvement of internal fixation devices, BI treatment has recorded breakthroughs in recent years. In group A, most cases can achieve one-stage reduction and fixation by posterior interarticular distraction combined with internal fixation. The reduction of the odontoid process is known as decompression, and few patients require complex transoral odontoidectomy. Group B had more patients who underwent the posterior fixation technique (the same technique as that of group A) and achieved excellent results. Available evidence shows that posterior surgery is effective in the treatment of BI because the expansion and fixation of the joints relieve the compression of the ventral surface of the brainstem. In summary, the BI treatment strategy gradually changed from the anterior-posterior composite approach to the single posterior approach, and decompression was performed through reduction and fixation technology without additional bone decompression. The posterior lateral atlantoaxial joint distraction and fixation technique is uncomplicated; however, achieving a sufficient reduction of the dentate process in BIs is difficult. In group A cases, horizontal and vertical displacement of the odontoid process is often combined with angular displacement, which manifests as CCA reduction. Cervical traction after general anesthesia cannot correct all vertical dislocations. Cage insertion between joints can help correct vertical dislocations; however, it is not a suitable method for CCA correction because the two surfaces of the lateral atlantoaxial joint in ideal reduction are not parallel but present a wedge shape [ 8 , 12 ]. In group B cases, changing the position of the odontoid process via interarticular distraction proves difficult. Because the central atlantoaxial joint is strong and there is no dislocation, the downward movement of the odontoid process is often not observed after cervical traction under general anesthesia. Separating the lateral atlantoaxial joints by a reasonable distance remains challenging even when using a distraction device. In this group of cases, reduction of the CCA is present and ventral compression is significant. Therefore, it is crucial to relieve ventral compression by correcting the CCA. When vertical dislocation cannot be reduced or the CCA needs to be corrected after cervical traction under general anesthesia, the lateral atlantoaxial joint remodeling technology can be considered and the lateral joint surface can be partially removed during the operation. There are few studies on lateral atlantoaxial joint remodeling technology. Chandra's technology provides us with a new idea. He adopts the joint surface remodeling technology when the lateral atlantoaxial joint is tilted forward and excises the posterior surface of the C2 articular process and the anterior surface of the C1 articular process, which has achieved good results in some complicated cases[ 13 ]. Salunke et al. used the comprehensive drilling technique of the lateral mass joint to perform facet osteotomy and applied it to the irreducible atlantoaxial dislocation [ 14 ]. Their research has allowed more AAD cases to be treated with the one-stage posterior surgery, avoiding the anterior odontoidectomy. However, they did not pay particular attention to the correction of the CCA nor applied this technique in BI without AAD. Our technology is slightly different. We believe that the joint remodeling technology has a wider application. The range of articular process resection is also concentrated as anteriorly as possible, allowing cage placement to assist in reduction. It can be used in cases where traction alone cannot completely reduce the atlantoaxial joint or in cases where the CCA needs to be corrected. In addition, we also used this technique in BI without AAD. During the operation, an ultrasonic osteotome was used to remove part of the bones on the dorsal side of the C1 and C2 articular processes to form an inclined surface between the joints. After cage placement, the odontoid process could be further moved down and the reduction of angular displacement could be improved. The use of this technique can effectively reduce the compression of the ventral brainstem. In this group, CCA and CMA were significantly increased postoperatively, and pB-C2 was decreased compared with the preoperative value. In addition, AAD was achieved in this group. The odontoid process of BI without AAD was slightly lower than before the operation. The postoperative ADI was within the normal range, and the CLV was lower than its preoperative value. Of course, this technology also has potential risks. Joint remodeling inevitably leads to the loss of cortical bone structure. During cage implantation, there is a possibility of fracture of the articular surface, especially the risk of vertebral artery injury when combined with the high-riding vertebral artery. Therefore, it is important to pay attention to the shape of the vertebral artery before the operation. When the vertebral artery is close to the upper articular surface of C2, excessive resection of the upper articular process of C2 should be avoided to prevent an injury to the vertebral artery. In our study, the C1 inferior articular process collapsed in two cases, and one case had an avulsion fracture of the C1 anterior arch due to downward movement of the dentate process after cage placement in type B skull base depression. Although no nerve and blood vessel injuries occurred, this technique should be carefully applied in patients with osteoporosis. Conclusion The combined application of lateral atlantoaxial joint remodeling, cage placement, and intraoperative cervical traction can effectively correct the vertical and angular displacement of the lateral atlantoaxial joint and effectively relieve the compression of the ventral brainstem. These combined application techniques are safe and feasible in the one-stage posterior surgical treatment of BI when atlantoaxial joint reduction is difficult. Declarations Ethical Approval and Consent to participate: Approval for the retrospective study was obtained from the ethics committee of Sanbo Brain Hospital, and all procedures performed in this study was in accordance with the 1964 Helsinki declaration and its later amendments. Human and Animal Ethics: Not applicable. Consent for publication: Not applicable. Availability of supporting data: Not applicable. Competing interests: The authors declare that they have no conflicts of interest. Funding: This article was supported by the Beijing Municipal Science and Technology Commission (Z191100006619040, T.F.) and the Capital Health Research and Development of Special (2020-2-8011, T.F.). Authors' contributions: "Zhe Hou wrote the main manuscript text and Zhe Hou prepared figures 1-4. Qiang Jian and Wayne Fan finished the statistics of the article. Tao Fan performed the operation and designed the experiment. Cong Liang completed the data collection. All authors reviewed the manuscript." Acknowledgements: none Authors' information: Zhe Hou, MD,1,2 Tao Fan, MD, Ph.D.,1 Wayne Fan,3 Qiang Jian, MD,1 Yinqian Wang, MD1 Affiliations: 1 Spine Center, Sanbo Brain Hospital, Capital Medical University, Beijing, People’s Republic of China; 2 Department of Neurosurgery, Beijing Luhe Hospital, Capital Medica University, Beijing, People’s Republic of China; 3 Faculty of Science, The University of British Columbia, Vancouver, British Columbia, Canada Corresponding Author: Tao Fan [email protected] References Goel A: Treatment of basilar invagination by atlantoaxial joint distraction and direct lateral mass fixation . J Neurosurg Spine 2004, 1 (3):281–286. Chen Z, Duan W, Chou D, Guan J, Liu Z, Jian Q, Zhang B, Bo X, Jian F: A Safe and Effective Posterior Intra-Articular Distraction Technique to Treat Congenital Atlantoaxial Dislocation Associated With Basilar Invagination: Case Series and Technical Nuances . Oper Neurosurg (Hagerstown) 2021, 20 (4):334–342. Goel A, Jain S, Shah A: Radiological Evaluation of 510 Cases of Basilar Invagination with Evidence of Atlantoaxial Instability (Group A Basilar Invagination) . World Neurosurg 2018, 110 :533–543. Salunke P, Sahoo S, Khandelwal NK, Ghuman MS: Technique for direct posterior reduction in irreducible atlantoaxial dislocation: multi-planar realignment of C1-2 . Clin Neurol Neurosurg 2015, 131 :47–53. Goel A, Sathe P, Shah A: Atlantoaxial Fixation for Basilar Invagination without Obvious Atlantoaxial Instability (Group B Basilar Invagination): Outcome Analysis of 63 Surgically Treated Cases . World Neurosurg 2017, 99 :164–170. Salunke P, Karthigeyan M, Malik P, Panchal C: Changing Perception but Unaltered Reality: How Effective Is C1-C2 Fixation for Chiari Malformations without Instability? World Neurosurg 2020, 136 :e234-e244. Shang G, Fan T, Hou Z, Liang C, Wang Y, Zhao X, Fan W: A modified microsurgical interfacet release and direct distraction technique for management of congenital atlantoaxial dislocation: technical note . Neurosurg Rev 2019, 42 (2):583–591. Wang C, Yan M, Zhou HT, Wang SL, Dang GT: Open reduction of irreducible atlantoaxial dislocation by transoral anterior atlantoaxial release and posterior internal fixation . Spine (Phila Pa 1976) 2006, 31 (11):E306-313. Goel A: Basilar invagination, Chiari malformation, syringomyelia: a review . Neurol India 2009, 57 (3):235–246. Zileli M, Cagli S: Combined anterior and posterior approach for managing basilar invagination associated with type I Chiari malformation . J Spinal Disord Tech 2002, 15 (4):284–289. Duan W, Chou D, Jiang B, Liu Z, Zhao X, Xia Z, Jian F, Chen Z: Posterior revision surgery using an intraarticular distraction technique with cage grafting to treat atlantoaxial dislocation associated with basilar invagination . J Neurosurg Spine 2019:1–9. Wang C, Yan M: Letter: Distraction, Compression, Extension, and Reduction Combined With Joint Remodeling and Extra-articular Distraction: Description of 2 New Modifications for Its Application in Basilar Invagination and Atlantoaxial Dislocation: Prospective Study in 79 Cases . Neurosurgery 2017, 80 (4):227–230. Chandra PS, Prabhu M, Goyal N, Garg A, Chauhan A, Sharma BS: Distraction, Compression, Extension, and Reduction Combined With Joint Remodeling and Extra-articular Distraction: Description of 2 New Modifications for Its Application in Basilar Invagination and Atlantoaxial Dislocation: Prospective Study in 79 Cases . Neurosurgery 2015, 77 (1):67–80; discussion 80. Salunke P, Sahoo SK, Deepak AN, Ghuman MS, Khandelwal NK: Comprehensive drilling of the C1-2 facets to achieve direct posterior reduction in irreducible atlantoaxial dislocation . J Neurosurg Spine 2015, 23 (3):294–302. Additional Declarations No competing interests reported. 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Also discoverable on Platform About Our Team In Review Editorial Policies Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-2323306","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":156106136,"identity":"38bcf3be-cf22-4947-a5e6-95b905bcbad7","order_by":0,"name":"Zhe Hou","email":"","orcid":"","institution":"Capital Medica University","correspondingAuthor":false,"submittingAuthor":false,"prefix":"","firstName":"Zhe","middleName":"","lastName":"Hou","suffix":""},{"id":156106137,"identity":"65a5077b-da21-4d6e-b993-0e607dd72c56","order_by":1,"name":"Qiang Jian","email":"","orcid":"","institution":"Capital Medica University","correspondingAuthor":false,"submittingAuthor":false,"prefix":"","firstName":"Qiang","middleName":"","lastName":"Jian","suffix":""},{"id":156106138,"identity":"bb026211-2a54-498a-8e81-b6dd2fc1d8b4","order_by":2,"name":"Wayne Fan","email":"","orcid":"","institution":"The University of British Columbia","correspondingAuthor":false,"submittingAuthor":false,"prefix":"","firstName":"Wayne","middleName":"","lastName":"Fan","suffix":""},{"id":156106139,"identity":"0ef36e2b-d96f-41c5-91f7-bdc3e3c0861d","order_by":3,"name":"Cong Liang","email":"","orcid":"","institution":"Capital Medica University","correspondingAuthor":false,"submittingAuthor":false,"prefix":"","firstName":"Cong","middleName":"","lastName":"Liang","suffix":""},{"id":156106140,"identity":"6b8aa40d-46e0-4515-8b9e-ba99bcc0b4e2","order_by":4,"name":"Tao Fan","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAArElEQVRIiWNgGAWjYBAC9gYg8QHKkSBKC88BBsbGGSRraeYhTQv72eOPbWrsog0OMB+8zcNgl0dYC09eYnPOseTcDQfYkq15GJKLCWqxZ8gxbM5tOADUwmMmzcNwILGBoC38bwybLcFa+L8RqUUCaAsjxBY2YrW8MZzZA/TLzMNsxpZzDJKJcViOwYcfNXa5fcebH954U2FHWAsCMIMIA+LVj4JRMApGwSjAAwB2Ezl6y+eCzgAAAABJRU5ErkJggg==","orcid":"","institution":"Capital Medica University","correspondingAuthor":true,"submittingAuthor":false,"prefix":"","firstName":"Tao","middleName":"","lastName":"Fan","suffix":""}],"badges":[],"createdAt":"2022-11-29 04:14:18","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-2323306/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-2323306/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":29780839,"identity":"bfa8cec0-cb15-41c9-a7b6-f194b76f2a4d","added_by":"auto","created_at":"2022-12-01 16:13:54","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":214619,"visible":true,"origin":"","legend":"\u003cp\u003eSchematic diagram of lateral atlantoaxial joint remodeling and cage placement. (A) The lateral atlantoaxial joint surface of patients with basilar invagination is often horizontal or inclined forward. (B) After cervical traction, the articular cartilage and part of the bone behind the articular process are excised to form an inclined surface between the joints. (C, D) In the process of placing cage, C1 rotates upward and backward relative to C2, so that the clivus canal angle decreases.\u003c/p\u003e","description":"","filename":"fig1.png","url":"https://assets-eu.researchsquare.com/files/rs-2323306/v1/0b8e1d5a7862ae254455e58a.png"},{"id":29780841,"identity":"8bffab7d-1580-4902-8137-bc8b7bda4c3a","added_by":"auto","created_at":"2022-12-01 16:13:54","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":4123391,"visible":true,"origin":"","legend":"\u003cp\u003e(A) Under the protection of gelatin sponge, the C2 nerve root was pulled upward using nerve dissector to expose the lateral atlantoaxial joint. (B) Under the microscope, the articular cartilage was excised with an ultrasonic osteotome, and the interfacet distractor was used for distraction.(C) Ultrasonic osteotomy and laminectomy rongeur were used to remove the upper articular process of C2 and part of the lower articular process of C1. At this time, soft tissues on the ventral side of the joint could be observed under the microscope (D). (E, F) The cage filled with autogenous bone debris was placed between the joints.\u003c/p\u003e","description":"","filename":"fig2.png","url":"https://assets-eu.researchsquare.com/files/rs-2323306/v1/6e93ee1beeb05399ac27c579.png"},{"id":29780838,"identity":"502b48f4-83ef-4d16-ac2b-7bfe15937966","added_by":"auto","created_at":"2022-12-01 16:13:54","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":1930385,"visible":true,"origin":"","legend":"\u003cp\u003eA 47 year old male presented with clinical symptoms of limb weakness. (A, B) After general anesthesia, the patient was in prone position. After cervical traction, the X-ray image showed that the odontoid process moved downward, but it did not drop to the level of the anterior tubercle of atlas. (C) The preoperative sagittal CT images showed atlantoaxial dislocation, basilar invagination, atlas occipitalization, clivus canal angle of 138.9 °, and ossification and fusion of lateral atlantoaxial joint on the right side (D), and left joint surface slightly inclined forward (E). (F) Sagittal T2 MRI showed that the dentate process pressed the brainstem ventrally and accompanied with syringomyelia. (G) After operation, the odontoid process moved down to the level of the anterior tubercle of atlas, and the clivus canal angle increased to 151.5 ° (H, I) Cage was placed between the atlantoaxial joints on both sides, but the articular surface of the right C1 superior articular process collapsed after joint remodeling and cage placement. (J) One week after the operation, T2 sagittal MRI showed that the ventral compression of the spinal cord was relieved, the syringomyelia was significantly reduced, and the cerebellar tonsils were moved upward. (K, L) Six months after operation, CT showed that the lateral atlantoaxial joints had achieved bone fusion.\u003c/p\u003e","description":"","filename":"fig3.png","url":"https://assets-eu.researchsquare.com/files/rs-2323306/v1/46d43ed57a80580f7e59fd5b.png"},{"id":29780840,"identity":"6edbc37a-efd7-46bc-801d-fc51fc847a51","added_by":"auto","created_at":"2022-12-01 16:13:54","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":2882619,"visible":true,"origin":"","legend":"\u003cp\u003eA 35 year old female presented with neck pain and walking instability. (A) The patient is prone and the head is fixed on the sliding-traction head holder. Compared with the X-ray before (B) and after cervical traction (C), there was no obvious downward movement of the odontoid process. The X-ray image after cage was placed between the joints showed that the odontoid process was significantly downward (D). (E, F, G) Preoperative sagittal CT showed a clear basilar invagination, atlas occipitalization, bilateral lateral articular surfaces slightly inclined forward, and the clivus canal angle was 128.1 ° (H) Coronal CT showed that the joint space between the odontoid process and the lateral mass of atlas was asymmetric, and C1 was inclined to the right relative to C2. (I) Preoperative T2 sagittal MR showed ventral compression of the brainstem with chiari malformation. (J) After operation, the odontoid process moved downward, and the clivus canal angle increased to 142.4 °, but avulsion fracture occurred in the anterior arch of atlantoaxial axis. (K, L) Cage was placed between joints after bilateral joint remodeling. After operation, T2 sagittal MR showed that the ventral compression of brainstem was significantly reduced and the descending degree of cerebellar tonsil hereniation was significantly reduced. (N) The bone fusion between joints was found by CT scan 6 months after operation.\u003c/p\u003e","description":"","filename":"fig4.png","url":"https://assets-eu.researchsquare.com/files/rs-2323306/v1/db794babf7d5050224723d8b.png"},{"id":30611218,"identity":"6ff9f91e-e415-4de9-b1af-87cae0bfec8a","added_by":"auto","created_at":"2022-12-21 08:29:30","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":5456345,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-2323306/v1/c726f0af-954c-42a1-ba3f-1b4fa6f2d7a4.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"Treatment of Basilar Invagination by Joint Remodeling and Cage Implantation Combined with Intraoperative Cervical Traction","fulltext":[{"header":"Introduction","content":"\u003cp\u003eBasilar invagination (BI) often manifests as the upward movement of the dentate process, which then compresses the brainstem. The condition presents with clinical symptoms requiring surgical treatment. In 2004, Goel divided the disease into group A (BI with atlantoaxial dislocation [AAD]) and group B (BI without AAD) [\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e]. The treatment strategy for BI has changed from anterior decompression and posterior fixation to posterior direct reduction and fixation regardless of whether it is group A or group B. In group A, the reduction of the odontoid process can relieve ventral compression; therefore, the reduction and fixation technology has become the most commonly used surgical method [\u003cspan additionalcitationids=\"CR3\" citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e]. It has been proven effective in moving the odontoid process downward in patients with Group B BI via the interarticular distraction technique [\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e, \u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e]; however, it has not been widely adopted because of the challenges posed by the technique. Therefore, in the posterior approach of BI, the surgical methods of groups A and B are the same. However, after intraoperative traction, the lateral atlantoaxial joints of some group A cases and all group B cases find it difficult to expand, which makes the dentate process descend to a proper position. In addition, the clivus canal angle (CCA) may not be corrected to an ideal degree.\u003c/p\u003e \u003cp\u003eIn our study, we improved Goel\u0026rsquo;s technology, and when it was difficult to reduce the odontoid process during the operation, we used cage implantation after joint remodeling to assist in reduction. In addition, we designed a slide rail-type headrest to facilitate accurate adjustment of traction strength during the operation. In this study, 11 cases of BI treated with this technique were retrospectively analyzed to evaluate the effectiveness of the technique, and clinical outcomes were reported.\u003c/p\u003e"},{"header":"Materials And Methods","content":"\u003cp\u003ePatient Population\u003c/p\u003e \u003cp\u003eThis study included 11 cases of BI treated with articular surface remodeling, cage placement, and intraoperative traction in our department from July 2019 to August 2021. All procedures were performed by the same operator (FT). The hospital ethics committee approved this study, and informed consent was obtained from all patients before surgery. Clinical data are shown in Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e. The study included four men and seven women with an average age of 40.5 years. All patients had neurological dysfunction, with symptoms lasting from 3 months to 7 years (average of 3.1 years). The main symptoms were neck pain in three cases (27.3%), limb weakness in five cases (45.5%), paresthesia in six cases (54.5%), and gait disorder in two cases (18.2%). The clinical status before and at least one year after the operation was assessed using the Japanese Orthopedic Association (JOA) scale.\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab1\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eClinical date of patients in this group\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"7\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c7\" colnum=\"7\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003ePatient\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003eSex/age\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003eMain symptom\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003eRadiographic abnormalities\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colspan=\"2\" nameend=\"c6\" namest=\"c5\"\u003e \u003cp\u003eJOA score\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c7\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003eHeight of the cage\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003ePT\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c6\"\u003e \u003cp\u003eLF\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eF/39\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eGait disturbance\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eBI AAD AOA KFS CM SM\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e12\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e15\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e10\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eF/46\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eLimbs weakness\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eBI AAD AOA KFS CM SM\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e9\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e14\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e8\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eM/47\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eLimbs weakness and numbness\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eBI AAD AOA SM\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e12\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e14\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e9\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eM/39\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eLimbs weakness and dyspnea\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eBI AAD AOA KFS CM SM\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e13\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e8\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eF/28\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eNeck pain and paresthesia\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eBI AAD AOA CM SM\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e15\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e17\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e9\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eM/45\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eLimbs weakness and dyspnea\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eBI AAD AOA KFS\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e13\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e15\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e10\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e7\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eF/35\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eGait disturbance\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eBI AOA CM\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e14\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e17\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e7\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e8\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eF/25\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eLimbs weakness and paresthesia\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eBI AOA SM\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e11\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e15\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e6\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e9\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eF/52\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eParesthesia and neck pain\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eBI AOA KFS SM\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e13\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e15\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e7\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e10\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eF/35\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eNeck pain and paresthesia\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eBI AOA CM SM\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e12\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e15\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e6\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e11\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eM/55\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eParesthesia\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eBI AOA CM SM\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e12\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e16\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e6\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003ctfoot\u003e \u003ctr\u003e\u003ctd colspan=\"7\"\u003eAAD, atlantoaxial dislocation; AOZ, atlas occipitalization; BI, basilar invagination; KF, Klippel-Feil syndrome; M, male; F, female; PT, pretreated; LF, latest follow-up\u003c/td\u003e\u003c/tr\u003e \u003c/tfoot\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003eRadiological Evaluation\u003c/p\u003e \u003cp\u003eAll patients underwent a three-dimensional (3D) CT scan and magnetic resonance imaging (MRI) of the cervical spine pre- and postoperatively. The 3D CT was performed during the follow-up. The Chamberlain line invasion (CLV), atlas-dens interval (ADI), and CCA were measured on median sagittal CT pre- and postoperatively. BI was diagnosed when CLV was more than 5 mm, and AAD was diagnosed when ADI was more than 3 mm. pB-C2 and cervicomedullary angle (CMA) were measured on sagittal MR pre- and postoperatively. The CCA, pB-C2, and CMA were used to assess the degree of compression on the ventral surface of the brainstem. On a follow-up CT scan, we checked whether there was a uniform fusion mass between the C1 and C2 lateral mass joints to determine whether solid fusion was achieved.\u003c/p\u003e \u003cp\u003eCervical Traction and Surgical Techniques\u003c/p\u003e \u003cp\u003eSomatosensory evoked potential (SEP), an intraoperative neuroelectrophysiological monitoring (IONM) technique, was used to monitor spinal cord function during cervical traction and operation. All patients were anesthetized by oral tracheal intubation and placed in a prone position with their heads in a neutral position. After anesthesia, we used our self-designed sliding-traction head holder to fix the head, so that both the eyes and forehead were suspended in the air to avoid the pressure on the eyes. Thereafter, we rotated the traction screw to achieve cervical traction. Afterward, we monitored the reduction of the craniocervical junction using the C-arm X-ray machine and gradually increased the traction strength, up to one-fifth of the body weight. All the cases in this group did not achieve complete reduction, and no odontoid process movement was found in five group B cases of BI after cervical traction. Using the suboccipital posterior median approach, we exposed the squamous part of the occipital bone to the C2 spinous process and vertebral lamina, separated the muscles to both sides, exposed the isthmus of the pedicle and C2 nerve root, and cauterized the venous plexus around the C2 nerve root under a microscope. Thereafter, the C2 nerve root was pulled upward using a nerve stripping ion to expose the lateral atlantoaxial joint. Afterward, the articular cartilage was excised using an ultrasonic osteotome, and an interarticular distractor was used for distraction, as we have previously described [\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e]. Thereafter, we observed the distance between the joint surfaces under continuous cervical traction and performed joint remodeling in cases where the joints could not be separated by a proper distance. The upper and lower articular surfaces of the lateral atlantoaxial joint were osteotomized with an ultrasonic osteotome and a laminectomy rongeur. In addition, as shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e, a part of the bone at the inferior and superior articular surfaces was removed. Thereafter, a cage of appropriate height was filled with mixed autogenous bone and artificial bone and was placed between the joints of the bilateral lateral mass, and the degree of the dentate process\u0026rsquo; downward movement was monitored by a C-arm X-ray machine (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e). After a satisfactory reduction of the dentate process, an occipital bone and a C2 screw were inserted. C2 pedicle screws were routinely placed during screw placement. When combined with a narrow C2 pedicle and high-riding vertebral artery, we used laminar screws or C2 subfacetal screws to replace C2 pedicle screws. Afterward, we stopped cervical traction and tightened the screws to fix the titanium connecting rod. When ADI reduction was not satisfactory, we used cantilever technology to assist in the reduction process.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cdiv id=\"Sec3\" class=\"Section2\"\u003e \u003ch2\u003eStatistical Analysis\u003c/h2\u003e \u003cp\u003eAll parameters were expressed as mean\u0026thinsp;\u0026plusmn;\u0026thinsp;standard deviation. The Wilcoxon signed-rank test was used to compare preoperative and postoperative parameters, and the significant difference was set at P\u0026thinsp;\u0026lt;\u0026thinsp;0.05\u003c/p\u003e \u003c/div\u003e"},{"header":"Results","content":"\u003cp\u003eClinical Outcomes\u003c/p\u003e \u003cp\u003eAll 11 patients included in this study were successfully implanted with screws, underwent occipitocervical fusion, and had no screw invasion and vertebral artery injury. IONM showed that no patient had neurological impairment during cervical traction and surgical procedures. The mean operative time was 201.8 min (150\u0026ndash;300 min), and the mean intraoperative bleeding volume was 160 mL (80\u0026ndash;250 mL). The mean height of the cage was 7.8 mm (6\u0026ndash;10 mm). Immediately after the operation, 10 patients\u0026rsquo; neurological function improved, and one patient maintained the original state. At the last follow-up, the symptoms of 11 patients were significantly improved, and the mean JOA score increased from 11.73\u0026thinsp;\u0026plusmn;\u0026thinsp;2.45 postoperatively to 15.09\u0026thinsp;\u0026plusmn;\u0026thinsp;1.22 postoperatively (z = \u0026minus;\u0026thinsp;2.956, P\u0026thinsp;=\u0026thinsp;0.003).\u003c/p\u003e \u003cp\u003eRadiographic Results\u003c/p\u003e \u003cp\u003eAfter cervical traction, the odontoid process of the 11 patients was not sufficiently reduced, six cases of BI with AAD were reduced to a certain extent, and five cases of BI without AAD did not have an obvious odontoid process downward movement. We have presented changes in average parameters pre- and postoperatively in Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e.\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab2\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 2\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eClinical date of patients in this group\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"4\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\"\u0026plusmn;\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\"\u0026plusmn;\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eVariable\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003ePreoperative\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003ePostoperative\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eP\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eCLV (mm)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c2\"\u003e \u003cp\u003e9.96\u0026thinsp;\u0026plusmn;\u0026thinsp;1.41\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c3\"\u003e \u003cp\u003e5.49\u0026thinsp;\u0026plusmn;\u0026thinsp;2.04\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.003\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eADI (mm)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c2\"\u003e \u003cp\u003e3.90\u0026thinsp;\u0026plusmn;\u0026thinsp;3.25\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c3\"\u003e \u003cp\u003e0.95\u0026thinsp;\u0026plusmn;\u0026thinsp;0.54\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.013\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eCCA\u0026deg;\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c2\"\u003e \u003cp\u003e137.25\u0026thinsp;\u0026plusmn;\u0026thinsp;8.38\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c3\"\u003e \u003cp\u003e147.35\u0026thinsp;\u0026plusmn;\u0026thinsp;7.55\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.003\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003epB-C2 (mm)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c2\"\u003e \u003cp\u003e10.85\u0026thinsp;\u0026plusmn;\u0026thinsp;2.96\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c3\"\u003e \u003cp\u003e7.13\u0026thinsp;\u0026plusmn;\u0026thinsp;1.38\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.003\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eCMA\u0026deg;\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c2\"\u003e \u003cp\u003e131.58\u0026thinsp;\u0026plusmn;\u0026thinsp;9.17\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c3\"\u003e \u003cp\u003e146.05\u0026thinsp;\u0026plusmn;\u0026thinsp;6.36\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.003\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003ePostoperatively, all patients had a descent of dentate process (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e, Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e). CLV decreased from 9.96\u0026thinsp;\u0026plusmn;\u0026thinsp;1.41 to 5.49\u0026thinsp;\u0026plusmn;\u0026thinsp;2.04 (z = \u0026minus;\u0026thinsp;2.934, P\u0026thinsp;=\u0026thinsp;0.003) and ADI decreased from 3.90\u0026thinsp;\u0026plusmn;\u0026thinsp;3.25 to 0.95\u0026thinsp;\u0026plusmn;\u0026thinsp;0.54 (z = \u0026minus;\u0026thinsp;2.491, P\u0026thinsp;=\u0026thinsp;0.013). In all cases, the ventral compression was significantly relieved. In addition, six cases were associated with Chiari malformations and nine cases with syringomyelia; however, the degree of Chiari malformations and syringomyelia reduced after the operation. Postoperative images showed that two patients had a collapse of the C1 inferior articular surface and one patient had an avulsion fracture of the C1 anterior arch (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e); however, none of them had nerve injury symptoms. In addition, there was one case with severe spinal cord compression symptoms accompanied by dyspnea before the operation. A tracheotomy was performed immediately after the operation, and the tracheotomy tube was removed two weeks postoperatively after the condition was stabilized. The follow-up period ranged from 12 to 25 months (mean 19.2 months). At the most recent follow-up, the dentate process was moved downward and remained corrected in all patients, and they all showed interarticular bone fusion. No cases of screw pulling out, screw loosening, or cage displacement occurred.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003c/p\u003e"},{"header":"Discussion","content":"\u003cp\u003eBI is often associated with AAD, atlantooccipital fusion, C2-3 fusion, Chiari malformations, and syringomyelia. After ventral compression is relieved and the atlantoaxial stability maintained, Chiari malformation is restored, and the syringomyelia is significantly reduced [\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e, \u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e]. This suggests that the primary lesions of these patients often result from the dentate process pressing the medulla oblongata, while cerebellar tonsillar hernia and syringomyelia are secondary changes. Anterior ventral decompression combined with posterior fixation has been proven effective in treating BI with or without ADD [\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e, \u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e]. With the development of this treatment strategy and continuous improvement of internal fixation devices, BI treatment has recorded breakthroughs in recent years. In group A, most cases can achieve one-stage reduction and fixation by posterior interarticular distraction combined with internal fixation. The reduction of the odontoid process is known as decompression, and few patients require complex transoral odontoidectomy. Group B had more patients who underwent the posterior fixation technique (the same technique as that of group A) and achieved excellent results. Available evidence shows that posterior surgery is effective in the treatment of BI because the expansion and fixation of the joints relieve the compression of the ventral surface of the brainstem. In summary, the BI treatment strategy gradually changed from the anterior-posterior composite approach to the single posterior approach, and decompression was performed through reduction and fixation technology without additional bone decompression.\u003c/p\u003e \u003cp\u003eThe posterior lateral atlantoaxial joint distraction and fixation technique is uncomplicated; however, achieving a sufficient reduction of the dentate process in BIs is difficult. In group A cases, horizontal and vertical displacement of the odontoid process is often combined with angular displacement, which manifests as CCA reduction. Cervical traction after general anesthesia cannot correct all vertical dislocations. Cage insertion between joints can help correct vertical dislocations; however, it is not a suitable method for CCA correction because the two surfaces of the lateral atlantoaxial joint in ideal reduction are not parallel but present a wedge shape [\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e, \u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e]. In group B cases, changing the position of the odontoid process via interarticular distraction proves difficult. Because the central atlantoaxial joint is strong and there is no dislocation, the downward movement of the odontoid process is often not observed after cervical traction under general anesthesia. Separating the lateral atlantoaxial joints by a reasonable distance remains challenging even when using a distraction device. In this group of cases, reduction of the CCA is present and ventral compression is significant. Therefore, it is crucial to relieve ventral compression by correcting the CCA.\u003c/p\u003e \u003cp\u003eWhen vertical dislocation cannot be reduced or the CCA needs to be corrected after cervical traction under general anesthesia, the lateral atlantoaxial joint remodeling technology can be considered and the lateral joint surface can be partially removed during the operation. There are few studies on lateral atlantoaxial joint remodeling technology. Chandra's technology provides us with a new idea. He adopts the joint surface remodeling technology when the lateral atlantoaxial joint is tilted forward and excises the posterior surface of the C2 articular process and the anterior surface of the C1 articular process, which has achieved good results in some complicated cases[\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e]. Salunke et al. used the comprehensive drilling technique of the lateral mass joint to perform facet osteotomy and applied it to the irreducible atlantoaxial dislocation [\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e]. Their research has allowed more AAD cases to be treated with the one-stage posterior surgery, avoiding the anterior odontoidectomy. However, they did not pay particular attention to the correction of the CCA nor applied this technique in BI without AAD. Our technology is slightly different. We believe that the joint remodeling technology has a wider application. The range of articular process resection is also concentrated as anteriorly as possible, allowing cage placement to assist in reduction. It can be used in cases where traction alone cannot completely reduce the atlantoaxial joint or in cases where the CCA needs to be corrected. In addition, we also used this technique in BI without AAD. During the operation, an ultrasonic osteotome was used to remove part of the bones on the dorsal side of the C1 and C2 articular processes to form an inclined surface between the joints. After cage placement, the odontoid process could be further moved down and the reduction of angular displacement could be improved. The use of this technique can effectively reduce the compression of the ventral brainstem. In this group, CCA and CMA were significantly increased postoperatively, and pB-C2 was decreased compared with the preoperative value. In addition, AAD was achieved in this group. The odontoid process of BI without AAD was slightly lower than before the operation. The postoperative ADI was within the normal range, and the CLV was lower than its preoperative value.\u003c/p\u003e \u003cp\u003eOf course, this technology also has potential risks. Joint remodeling inevitably leads to the loss of cortical bone structure. During cage implantation, there is a possibility of fracture of the articular surface, especially the risk of vertebral artery injury when combined with the high-riding vertebral artery. Therefore, it is important to pay attention to the shape of the vertebral artery before the operation. When the vertebral artery is close to the upper articular surface of C2, excessive resection of the upper articular process of C2 should be avoided to prevent an injury to the vertebral artery. In our study, the C1 inferior articular process collapsed in two cases, and one case had an avulsion fracture of the C1 anterior arch due to downward movement of the dentate process after cage placement in type B skull base depression. Although no nerve and blood vessel injuries occurred, this technique should be carefully applied in patients with osteoporosis.\u003c/p\u003e"},{"header":"Conclusion","content":"\u003cp\u003eThe combined application of lateral atlantoaxial joint remodeling, cage placement, and intraoperative cervical traction can effectively correct the vertical and angular displacement of the lateral atlantoaxial joint and effectively relieve the compression of the ventral brainstem. These combined application techniques are safe and feasible in the one-stage posterior surgical treatment of BI when atlantoaxial joint reduction is difficult.\u003c/p\u003e "},{"header":"Declarations","content":"\u003cp\u003e Ethical Approval and Consent to participate: Approval for the retrospective study was obtained from the ethics committee of Sanbo Brain Hospital, and all procedures performed in this study was in accordance with the 1964 Helsinki declaration and its later amendments.\u003c/p\u003e \u003c/p\u003e \u003cp\u003eHuman and Animal Ethics: Not applicable.\u003c/p\u003e\u003cp\u003eConsent for publication: Not applicable.\u003c/p\u003e\n\u003cp\u003eAvailability of supporting data: Not applicable.\u003c/p\u003e\n\u003cp\u003eCompeting interests: The authors declare that they have no conflicts of interest.\u003c/p\u003e\n\u003cp\u003eFunding: This article was supported by the Beijing Municipal Science and Technology Commission (Z191100006619040, T.F.) and the Capital Health Research and Development of Special (2020-2-8011, T.F.).\u003c/p\u003e\n\u003cp\u003eAuthors\u0026apos; contributions: \u0026quot;Zhe Hou wrote the main manuscript text and Zhe Hou prepared figures 1-4. Qiang Jian and Wayne Fan finished the statistics of the article. Tao Fan performed the operation and designed the experiment. Cong Liang completed the data collection. All authors reviewed the manuscript.\u0026quot;\u003c/p\u003e\n\u003cp\u003eAcknowledgements: none\u003c/p\u003e\n\u003cp\u003eAuthors\u0026apos; information: Zhe Hou, MD,1,2 Tao Fan, MD, Ph.D.,1 Wayne Fan,3 Qiang Jian, MD,1 Yinqian Wang, MD1 Affiliations: 1 Spine Center, Sanbo Brain Hospital, Capital Medical University, Beijing, People\u0026rsquo;s Republic of China; 2 Department of Neurosurgery, Beijing Luhe Hospital, Capital Medica University, Beijing, People\u0026rsquo;s Republic of China; 3 Faculty of Science, The University of British Columbia, Vancouver, British Columbia, Canada\u003c/p\u003e\n\u003cp\u003eCorresponding Author: Tao Fan\u0026nbsp;\u003c/p\u003e\n\u003cp\[email protected]\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eGoel A: \u003cb\u003eTreatment of basilar invagination by atlantoaxial joint distraction and direct lateral mass fixation\u003c/b\u003e. J Neurosurg Spine 2004, \u003cb\u003e1\u003c/b\u003e(3):281\u0026ndash;286.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eChen Z, Duan W, Chou D, Guan J, Liu Z, Jian Q, Zhang B, Bo X, Jian F: \u003cb\u003eA Safe and Effective Posterior Intra-Articular Distraction Technique to Treat Congenital Atlantoaxial Dislocation Associated With Basilar Invagination: Case Series and Technical Nuances\u003c/b\u003e. Oper Neurosurg (Hagerstown) 2021, \u003cb\u003e20\u003c/b\u003e(4):334\u0026ndash;342.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eGoel A, Jain S, Shah A: \u003cb\u003eRadiological Evaluation of 510 Cases of Basilar Invagination with Evidence of Atlantoaxial Instability (Group A Basilar Invagination)\u003c/b\u003e. World Neurosurg 2018, \u003cb\u003e110\u003c/b\u003e:533\u0026ndash;543.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eSalunke P, Sahoo S, Khandelwal NK, Ghuman MS: \u003cb\u003eTechnique for direct posterior reduction in irreducible atlantoaxial dislocation: multi-planar realignment of C1-2\u003c/b\u003e. Clin Neurol Neurosurg 2015, \u003cb\u003e131\u003c/b\u003e:47\u0026ndash;53.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eGoel A, Sathe P, Shah A: \u003cb\u003eAtlantoaxial Fixation for Basilar Invagination without Obvious Atlantoaxial Instability (Group B Basilar Invagination): Outcome Analysis of 63 Surgically Treated Cases\u003c/b\u003e. World Neurosurg 2017, \u003cb\u003e99\u003c/b\u003e:164\u0026ndash;170.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eSalunke P, Karthigeyan M, Malik P, Panchal C: \u003cb\u003eChanging Perception but Unaltered Reality: How Effective Is C1-C2 Fixation for Chiari Malformations without Instability?\u003c/b\u003e World Neurosurg 2020, \u003cb\u003e136\u003c/b\u003e:e234-e244.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eShang G, Fan T, Hou Z, Liang C, Wang Y, Zhao X, Fan W: \u003cb\u003eA modified microsurgical interfacet release and direct distraction technique for management of congenital atlantoaxial dislocation: technical note\u003c/b\u003e. Neurosurg Rev 2019, \u003cb\u003e42\u003c/b\u003e(2):583\u0026ndash;591.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eWang C, Yan M, Zhou HT, Wang SL, Dang GT: \u003cb\u003eOpen reduction of irreducible atlantoaxial dislocation by transoral anterior atlantoaxial release and posterior internal fixation\u003c/b\u003e. Spine (Phila Pa 1976) 2006, \u003cb\u003e31\u003c/b\u003e(11):E306-313.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eGoel A: \u003cb\u003eBasilar invagination, Chiari malformation, syringomyelia: a review\u003c/b\u003e. Neurol India 2009, \u003cb\u003e57\u003c/b\u003e(3):235\u0026ndash;246.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eZileli M, Cagli S: \u003cb\u003eCombined anterior and posterior approach for managing basilar invagination associated with type I Chiari malformation\u003c/b\u003e. J Spinal Disord Tech 2002, \u003cb\u003e15\u003c/b\u003e(4):284\u0026ndash;289.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eDuan W, Chou D, Jiang B, Liu Z, Zhao X, Xia Z, Jian F, Chen Z: \u003cb\u003ePosterior revision surgery using an intraarticular distraction technique with cage grafting to treat atlantoaxial dislocation associated with basilar invagination\u003c/b\u003e. J Neurosurg Spine 2019:1\u0026ndash;9.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eWang C, Yan M: \u003cb\u003eLetter: Distraction, Compression, Extension, and Reduction Combined With Joint Remodeling and Extra-articular Distraction: Description of 2 New Modifications for Its Application in Basilar Invagination and Atlantoaxial Dislocation: Prospective Study in 79 Cases\u003c/b\u003e. Neurosurgery 2017, \u003cb\u003e80\u003c/b\u003e(4):227\u0026ndash;230.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eChandra PS, Prabhu M, Goyal N, Garg A, Chauhan A, Sharma BS: \u003cb\u003eDistraction, Compression, Extension, and Reduction Combined With Joint Remodeling and Extra-articular Distraction: Description of 2 New Modifications for Its Application in Basilar Invagination and Atlantoaxial Dislocation: Prospective Study in 79 Cases\u003c/b\u003e. Neurosurgery 2015, \u003cb\u003e77\u003c/b\u003e(1):67\u0026ndash;80; discussion 80.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eSalunke P, Sahoo SK, Deepak AN, Ghuman MS, Khandelwal NK: \u003cb\u003eComprehensive drilling of the C1-2 facets to achieve direct posterior reduction in irreducible atlantoaxial dislocation\u003c/b\u003e. J Neurosurg Spine 2015, \u003cb\u003e23\u003c/b\u003e(3):294\u0026ndash;302.\u003c/span\u003e\u003c/li\u003e\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":true,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true},"keywords":"Atlantoaxial dislocation, Basilar invagination, Cervical traction, Joint remodeling, Cage insertion","lastPublishedDoi":"10.21203/rs.3.rs-2323306/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-2323306/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003e\u003cstrong\u003eObjective:\u003c/strong\u003eThis study aimed to explore the clinical and imaging results of lateral atlantoaxial joint remodeling, cage placement, and intraoperative traction in the treatment of basilar invagination.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eMethods:\u003c/strong\u003e The clinical data of 11 patients with basilar invagination treated by lateral atlantoaxial joint remodeling, cage placement, and intraoperative traction were analyzed retrospectively. The lateral atlantoaxial joint surface was remodeled to form an inclined surface between the joints, and a cage was then placed. The combined use of these techniques corrects the clivus canal angle and simultaneously moves the dentate process downward, thus reducing the compression on the ventral surface of the brainstem. The Chamberlain line invasion, atlas-dens interval, and clivus-canal angle were measured using a preoperative and postoperative CT scan. In addition, pB-C2 and cervicomedullary angle (CMA) were measured on sagittal magnetic resonance imaging pre- and postoperatively. The clinical outcomes of all patients were assessed using the Japanese Orthopedic Association (JOA) scale. Wilcoxon test was used to compare the pre- and postoperative measurements.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eResults:\u003c/strong\u003eClinical symptoms of all patients significantly improved. The mean JOA score increased from 11.73 ± 2.45 preoperatively to 15.09 ± 1.22 postoperatively (z = –2.956, P = 0.003). No vertebral artery or dura mater injury was observed. The ventral compression of the brainstem was relieved after the operation. The mean pB-C2 decreased from 10.85 ± 2.96 postoperatively to 7.13 ± 1.38 preoperatively (z = –2.936, P = 0.003), and mean clivus-carnal angle and mean CMA increased from 137.25 ± 8.38 and 131.58 ± 9.17 preoperatively to 147.35 ± 7.55 (z = –2.934, P = 0.003) and 146.05 ± 6.36 (z = –2.934, P = 0.003) postoperatively, respectively. There were two cases of collapse of the C1 inferior articular process and one case of avulsion fracture of the C1 anterior arch. All patients achieved interarticular bone fusion.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConclusion:\u003c/strong\u003e The cases demonstrated a safe and effective method for treating basilar invagination when atlantoaxial joint reduction is difficult during surgery.\u003c/p\u003e","manuscriptTitle":"Treatment of Basilar Invagination by Joint Remodeling and Cage Implantation Combined with Intraoperative Cervical Traction","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2022-12-01 16:13:49","doi":"10.21203/rs.3.rs-2323306/v1","editorialEvents":[{"type":"communityComments","content":0}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"3750175b-d6c0-4a4f-ac7a-ee45e475f035","owner":[],"postedDate":"December 1st, 2022","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[],"tags":[],"updatedAt":"2022-12-21T08:29:14+00:00","versionOfRecord":[],"versionCreatedAt":"2022-12-01 16:13:49","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-2323306","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-2323306","identity":"rs-2323306","version":["v1"]},"buildId":"omnImTCwR2MFx8CMYfrG7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}