Uneven and Asymmetric Changes in Spinal Canal Length After Correction of Severe Kyphoscoliosis: A 3D CT-Based Study

Uneven and Asymmetric Changes in Spinal Canal Length After Correction of Severe Kyphoscoliosis: A 3D CT-Based Study | 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 Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Research Article Uneven and Asymmetric Changes in Spinal Canal Length After Correction of Severe Kyphoscoliosis: A 3D CT-Based Study Chenhao Zhao, Youping Tao, Qiangqiang Guo, Jiaxu Wang, Jing Sun, and 3 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-7175445/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 Background: Changes in spinal canal length in severe kyphoscoliosis are critical for surgical strategy and preventing neurological complications. However, the specifics of these changes are not fully understood. Objective: This study investigates spinal canal length changes in severe kyphoscoliosis correction. Methods: Severe kyphoscoliosis patients (Cobb angle > 90°) were retrospectively analyzed. 3D models from CT images were constructed using Mimics software to measure spinal canal on cross-sections at the pedicle level. Lengths of the spinal canal were measured across various segments and compared between concave and convex sides. Correlation with Cobb angle correction rates was analyzed. Results: The study finally enrolled 11 patients. After surgery, the main curve Cobb angle improved by 42.5%±7.3%. The concave side of T1-S1 elongated by (5.0±7.0) mm, while the convex side shortened by (4.0±6.0) mm (P>0.05 for center). Within the main curve, the convex side shortened by (16.0±6.5) mm, and the center by (9.0±6.1) mm (P>0.05 for concave side). In compensatory curves, all sides elongated more on the concave side. In the osteotomy segment, each side showed significant shortening except the concave side. No significant correlation between segmental spinal canal length changes and Cobb angle correction rates. Conclusion: Central spinal canal length remained stable post-operation, but uneven changes were found on the main curve and compensatory curves. Asymmetric differences were observed of spinal canal changes between the concave and convex sides. differences were noted between concave and convex sides. There was no correlation between length changes and Cobb angle correction rates, The study provides insights for surgical strategies and neurological complication prevention. Scoliosis Spinal Canal Length Spinal cord injury Three-dimensional Computed Tomography Figures Figure 1 Figure 2 Figure 3 Figure 4 1. Introduction Scoliosis is a three-dimensional spinal deformity, and surgical treatment is an effective option for severe spinal deformities [ 1 ]. Severe kyphoscoliosis, characterized by complexity, rigidity, and large curve angles, presents a significant challenge in spinal surgery because of the difficulty of surgery, low correction rates, and high complication rates [ 2 ]. The risk of neurological damage during scoliosis correction surgery is a serious concern, with severe scoliosis (Cobb angle > 90°) being one of the risk factors [ 3 ]. Cases were reported that permanent neurological injuries happened after correction of severe kyphoscoliosis [ 4 – 6 ]. A review in 2011 of 11,741 cases found a rate of 0.99% of postoperative neurological damage in teenagers under 21 years old with scoliosis, with a rate of 0.73% for adolescent idiopathic scoliosis [ 7 ], while an analysis of 108 patients over a 10-year period treated with lumbar pedicle subtraction osteotomies (PSOs) showed neurological deficits were seen in 12 patients (11.1%) and were permanent in 3 patients (2.8%) [ 8 ]. Neurological injuries in spinal deformity surgery are mainly attributed to surgical technical factors such as hematoma compression and misplaced screws, and also, excessive changes in spinal canal length [ 9 ]. Modi et al. demonstrated on pigs that spinal cord injury can occur with excessive shortening of the spinal canal [ 10 ]. Yang et al. also found on pigs that excessive distraction of the spinal canal can also lead to spinal cord injury [ 9 ]. Therefore, knowing the characteristics of changes in spinal canal length before and after surgery in severe kyphoscoliosis is of clinical importance for surgical strategy and prevention of postoperative neurological complications. However, these changes are not yet fully understood. This study aims to explore the characteristics of spinal canal length changes in the correction of severe kyphoscoliosis. 2. Materials and Methods 2.1 Study Subjects A retrospective analysis was performed on the imaging data of patients aged 18 or above with severe kyphoscoliosis who underwent osteotomy surgery at our center between November 2021 and May 2024. Inclusion Criteria: Presence of only a single structural thoracic or thoracolumbar curve; Coronal Cobb angle of the structural curve ≥ 90° (measured on pre-operative standing radiographs); Patients undergoing primary surgery; Completion of pre-operative and post-operative full-spine CT scans. Exclusion Criteria: Presence of more than one structural curve; Intraspinal pathologies (e.g. tethered cord, syringomyelia); Spinal conditions affecting measurement accuracy (e.g. severe segmentation failure, severe spinal stenosis); History of previous spinal surgery. A total of 11 patients were ultimately enrolled, comprising 2 males and 9 females. The mean age was 36 ± 9 years (range: 23–47 years). The structural curves were located between T5 and L2. Radiological examinations showed no intraspinal neural abnormalities. All patients were undergone with three-column osteotomies (3COs), and all performed by the same surgeon team, as exampled in Fig. 1 . 2.2 Study Methods 2.2.1 Three-Dimensional Model Reconstruction According to previous studies [ 11 , 12 ], all patients' preoperative and postoperative whole-spine computed tomography (CT) images were imported into the 3D modeling software Mimics 21.0 (Materialise NV, Belgium) to reconstruct 3D models of the entire spine. On the level of the pedicle, detailed points were marked on the cross-section of the spinal canal: the midpoint of the right and left pedicle, the posterior edge of the vertebral body (anterior side), the connection point in front of the spinous process (posterior side), and the geometric center point of the spinal canal (center), as shown in Fig. 2 . 2.2.2 Parameter Measurement The lines connecting the respective points of the anterior, posterior, left, right, and center of each vertebra were approximated as the length of that segment of the spinal canal. The lengths of the spinal canal in the T1-S1 range, in the main curve and upper and lower compensatory curve ranges, and in the osteotomy segment range (the range of the top vertebra and its adjacent vertebrae) were measured. The differences of the length changes between the concave and convex sides before and after surgery were compared, and the correlation between the length changes and the Cobb angle correction rate of the corresponding segment was analyzed. 2.2.3 Data Analysis Statistical data analysis was performed using SPSS 26.0 software, with data presented as mean ± SD. Paired t-tests were used to compare the differences of spinal canal length in each segment before and after surgery, as well as the changes between the concave and convex sides (All continuous data passed the Shapiro-Wilk tests). The difference of the spinal canal length and the corresponding segment Cobb angle change value were analyzed for linear correlation. A two-tailed P-value of less than 0.05 was considered statistically significant. 3. Results 3.1 Preoperative and Postoperative Cobb Angle Improvement There was a significant improvement of the structural curve Cobb angles in the 11 patients before and after the operation (P < 0.05). The main curve correction rate was (42.5%±7.3%), and the correction rates for the upper and lower compensatory curves were (50.2%±3.1%) and (57.5%±4.6%), as shown in Table 1 . Table 1 Preoperative and Postoperative Cobb Angle Correction (°) Preoperative Postoperative Difference Correction Rate (%) t P Upper Curve 60.3 ± 16.4 34.6 ± 16.6 25.6 ± 15.1 50.2 ± 3.1 5.616 < 0.001 Main Curve 112.6 ± 13.2 56.3 ± 14.5 56.4 ± 12.5 42.5 ± 7.3 15.005 < 0.001 Lower Curve 48.0 ± 19.9 21.5 ± 11.1 26.5 ± 12.6 57.5 ± 4.6 6.975 < 0.001 t: The value of paired-t test. P: two-tailed P-value with a significance level of 0.05. 3.2 T1-S1 Spinal Canal Length Changes For the changes of T1-S1 spinal canal length, the concave side were significantly elongated at (5.0 ± 7.0)mm (P<0.05), while the convex side were significantly shortened at (4.0 ± 6.0)mm (P 0.05), as presented in Fig. 3 ( A ). 3.3 Segmental Spinal Canal Length Changes For each segment, the structural curve that underwent osteotomy was significantly shortened (P 0.05), while the upper and lower compensatory curves were significantly elongated (P<0.05), as shown in Fig. 3 ( B ). Within the main curve range, the convex side averaged a shortening of (16.0 ± 6.5) mm, the center averaged a shortening of (9.0 ± 6.1) mm, and the concave side showed no significant change. Within the osteotomy segment range, the convex side averaged a shortening of (15.4 ± 6.4) mm, the center averaged a shortening of (10.1 ± 5.9) mm, and the concave side showed no significant change, as shown in Fig. 3 ( C ). In the upper curve range, the convex side averaged an elongation of (2.6 ± 2.9) mm, the concave side averaged an elongation of (5.3 ± 2.7) mm, and the center averaged an elongation of (3.8 ± 2.7) mm. In the lower curve range, the convex side averaged an elongation of (2.6 ± 3.8) mm, the concave side averaged an elongation of (6.3 ± 2.5) mm, and the center averaged an elongation of (6.2 ± 2.9) mm. 3.4 Differences in Spinal Canal Length Changes Between Concave and Convex Sides There were significant differences of spinal canal changes between the concave and convex sides (P < 0.05). In the upper and lower curve segments, the concave side elongated more than the convex side, while in the main curve segment and osteotomy region, the concave side shortened less than the convex side, as shown in Fig. 3 ( D ). In the upper curve segment, the concave side elongated more than the convex side by (2.6 ± 1.3) mm; in the lower curve segment, the concave side elongated more than the convex side by (3.7 ± 3.8) mm. And in the main curve segment, the concave side shortened less than the convex side by (15.3 ± 4.8) mm; in the osteotomy region, the concave side shortened less than the convex side by (13.6 ± 7.1) mm. 3.5 Correlation Between Spinal Canal Length Changes and Cobb Angle Improvement The correlation analysis between the changes in spinal canal length in each segment and the corresponding Cobb angle improvement rate showed no significant correlation (all R 0.05), as shown in Table 2 and Fig. 4 . Table 2 The correlation between spinal canal length changes and Cobb angle correction rates in each segment. Convex Concave Center Upper Curve R = 0.131 R = 0.020 R = 0.016 P = 0.700 P = 0.954 P = 0.964 Main Curve R = 0.240 R = 0.387 R = 0.299 P = 0.477 P = 0.240 P = 0.372 Lower Curve R = 0.272 R = 0.255 R = 0.104 P = 0.418 P = 0.450 P = 0.761 R: correlation coefficient. P: two-tailed P-value with a significance level of 0.05. 4. Discussion This study used three-dimensional reconstruction technology to detail the changes in spinal canal length in severe kyphoscoliosis patients before and after 3CO surgery. Previous studies have reported varying ranges of spinal canal length changes in different types of scoliosis. Ni et al. measured approximate spinal canal length changes using X-rays, the range of spinal canal changes was − 1.23 to 2.82 cm in the center [ 13 ]. Yahara et al. used three-dimensional CT data to measure spinal canal length changes from T2 to L2 in adolescent idiopathic scoliosis (AIS) patients, reporting an average increase of 10.1 mm in the center [ 11 ]. Our findings indicate that the spinal canal after 3CO surgery tends to elongate on the concave side and shorten on the convex side, with the central length of the spinal canal remaining relatively stable from T1 to S1. Similarly, Han et al. retrospectively analyzed the changes in spinal canal length between the upper and lower end vertebrae and from T2 to L2 in 27 patients with idiopathic scoliosis. After the operation, the concave side of the spinal canal length increased, and the convex side of the spinal canal length significantly decreased [ 12 ]. However, our detailed segmental analysis firstly found that this pattern is attributed to the shortening effects of structural curve osteotomies and the elongation of upper and lower compensatory curves. Li et al. measured that three-column osteotomy could shorten the central spinal canal by 17 mm, and after the osteotomy, the convex side of the spinal canal in severe scoliosis patients shortened by 27.8 mm [ 14 ], showing similar conclusion with our study on the main curve range. But our measurements of the upper and lower compensatory curves found that while spinal canal shortening occurred in the structural curve segment, canal elongation was observed in compensatory curves. Although the central spinal canal length remained stable overall, uneven deformation patterns were demonstrated along the spinal canal. Moreover, our study observed that the concave side elongates more than the convex side or shortens less, indicating a significant relative elongation effect on the concave side during spinal correction—a pattern consistently seen in both structural curves and the main curve regions. Chu et al. and Yossi et al. respectively observed through magnetic resonance imaging (MRI) that the spinal cord runs along the concave side of the spinal canal in scoliosis [ 15 , 16 ], suggesting a possible risk of neurological complication because of this uneven elongation of concave side. Han et al. measured the changes in spinal canal length from the upper and lower end vertebrae and from T2 to L2 in 10 severe scoliosis patients. They found that after correction, the Ponte osteotomy resulted in more elongation of the concave side than the convex side, while the vertebral column resection (VCR) osteotomy resulted in greater shortening of the convex side than the concave side [ 17 ], with similar conclusions with our study. And our study additionally found that this pattern remains consistent in each segment as well as across the entire spinal canal. Cusick et al. found in primate studies that acute traction of spinal cord fibers can cause spinal cord injury [ 18 ]. Yang et al. found in a goat model study that the safe limit for shortening of the spinal cord in thoracolumbar bivertebral column resections was (35.2 ± 2.6) mm [ 19 ]. Qiu et al. also found in a goat model study that the safe limit for traction of the spinal column in spinal deformity surgery was (11.8 ± 3.65) mm, and spinal cord injury in spinal deformity surgery may be related to excessive traction of the spinal cord during the surgical correction process [ 20 ]. Based on those data above, our elongation or shortening of spinal canal was remain safe during the surgeries. However, during correction, excessive distraction or compression of the spinal canal should still be avoided, and comprehensive intraoperative neuromonitoring remains crucial. Moreover, the applicability of these animal model findings to human spinal cord injury thresholds remains uncertain, necessitating further research to establish surgical reference values. This study has certain limitations. Firstly, as a single-center retrospective study, our conclusions may be influenced by the surgical team's practices, and different centers may have different results. Secondly, our study population was limited to patients with a single structural curve of severe scoliosis, with a small sample size, precluding further analysis of spinal canal length changes in patients with different types of scoliosis. Additionally, manual selection of data points may introduce minor errors, although these do not affect the overall trends observed in our study. Future work should expand the sample size and adopt multi-center studies to analyze and compare spinal canal length changes in patients with different curve types. Research directions should include exploring the biomechanical changes of spinal cord tension and the spinal canal. 5. Conclusion In summary, significant changes of spinal canal length were observed in patients with severe kyphoscoliosis after corrective osteotomy surgery. The central length of the entire spinal canal did not significantly change after the operation, but uneven changes were found on the main curve and compensatory curves. Asymmetric differences were observed of spinal canal changes between the concave and convex sides. No significant correlation was observed between segmental spinal canal length changes and corresponding Cobb angle correction rates. This study provides insights for the surgical strategies of severe kyphoscoliosis and the prevention of postoperative neurological complications. Abbreviations 3CO: Three-Column Osteotomy AIS: Adolescent Idiopathic Scoliosis CT: Computed Tomography MRI: Magnetic Resonance Imaging PSO: Pedicle Subtraction Osteotomy VCR: Vertebral Column Resection Declarations Ethics approval This study was approved by the Ethics Committee of the Ninth Medical Center, Chinese PLA General Hospital (Approval No. LL-LSCY-2024-15) and conducted in accordance with the Declaration of Helsinki. Consent to participate Individual consent was waived for the retrospective analysis of anonymized data. Consent for publication Written informed consent was obtained from the patient in Figure 1 for publication of radiographic images. Availability of data and materials The datasets used and/or analyzed during the current study are available from the corresponding author on reasonable request. Competing interests The authors declare no competing interests. Funding This study did not receive any specific funding. Author contributions C.Z.: writing of the main manuscript text, measurement and analysis of data, figure preparation. Y.T.: interpretation of data, review and editing. Q.G.: identification and optimism of the measurement methodology. Jiaxu W, J.S, R.L&X.M: interpretation and acquisition of data. Jigong W.: design of the work, review and editing, supervision. All authors have read and approved the final submitted manuscript. Clinical trial number Not Applicable. 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Spine Deform.2022; 10(4):883-892. Zhang B, Zhang T, Tao H, Wu T, Duan C, Yang W, et al. Neurological complications of thoracic posterior vertebral column resection for severe congenital spinal deformities. Eur Spine J.2017; 26(7):1871-1877. Hamilton DK, Smith JS, Sansur CA, Glassman SD, Ames CP, Berven SH, et al. Rates of new neurological deficit associated with spine surgery based on 108,419 procedures: a report of the scoliosis research society morbidity and mortality committee. Spine (Phila Pa 1976).2011; 36(15):1218-1228. Buchowski JM, Bridwell KH, Lenke LG, Kuhns CA, Lehman RJ, Kim YJ, et al. Neurologic complications of lumbar pedicle subtraction osteotomy: a 10-year assessment. Spine (Phila Pa 1976).2007; 32(20):2245-2252. Yang JH, Suh SW, Modi HN, Ramani ET, Hong JY, Hwang JH, et al. Effects of vertebral column distraction on transcranial electrical stimulation-motor evoked potential and histology of the spinal cord in a porcine model. J Bone Joint Surg Am.2013; 95(9):835-842, S1- S2. Modi HN, Suh SW, Hong JY, Yang JH. The effects of spinal cord injury induced by shortening on motor evoked potentials and spinal cord blood flow: an experimental study in swine. J Bone Joint Surg Am.2011; 93(19):1781-1789. Yahara Y, Seki S, Makino H, Watanabe K, Uehara M, Takahashi J, et al. Three-dimensional computed tomography analysis of spinal canal length increase after surgery for adolescent idiopathic scoliosis: a multicenter study. J Bone Joint Surg Am.2019; 101(1):48-55. Han C, Hai Y, Zhou C, Yin P, Guo R, Wang H, et al. Investigation of in vivo three‐dimensional changes of the spinal canal after corrective surgeries of the idiopathic scoliosis. JOR Spine.2021; 4(3). Ni C, Hou T, Li M. [Study on the Length of Spinal Canal of Idiopathic Scoliosis Patients before and after Correction Operation]. Orthopedic Journal of China.2003; 11(15):1056-1058. Li X, Huang Z, Deng Y, Fan H, Sui W, Wang C, et al. Computed tomography based three-dimensional measurements of spine shortening distance after posterior three-column osteotomies for the treatment of severe and stiff scoliosis. Spine (Philadelphia, Pa. 1976).2017; 42(14):1050-1057. Chu WC, Man GC, Lam WW, Yeung BH, Chau WW, Ng BK, et al. Morphological and functional electrophysiological evidence of relative spinal cord tethering in adolescent idiopathic scoliosis. Spine (Phila Pa 1976).2008; 33(6):673-680. Smorgick Y, Settecerri J J, Baker K C, et al. Spinal Cord Position in Adolescent Idiopathic Scoliosis[J]. Journal of pediatric orthopaedics,2012,32(5):500-503. Han CF, Hai Y, Yin P, Cha T, Li GA. [In-vivo change of the spine canal after surgical corrections of severe and rigid kyphoscoliosis]. National Medical Journal of China.2019; 99(41):3243-3248. Cusick JF, Myklebust J, Zyvoloski M, Sances JA, Houterman C, Larson SJ. Effects of vertebral column distraction in the monkey. J Neurosurg.1982; 57(5):651. Yang H, Wang B, Zou X, Ge S, Chen Y, Zhang S, et al. Safe limit of shortening of the spinal cord in thoracolumbar bivertebral column resections: an experimental study in goats. World Neurosurg.2020; 134: e589-e595. Qiu F, Yang J, Ma X, Xu J, Yang Q, Zhou X, et al. Influence of vertebral column distraction on spinal cord volume: an experimental study in a goat model. Arch Orthop Trauma Surg.2015; 135(9):1201-1210. Additional Declarations No competing interests reported. Cite Share Download PDF Status: Posted Version 1 posted You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. 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Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board 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-7175445","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":498174839,"identity":"e44642e8-cd5a-45d5-b8ca-546dc3db8739","order_by":0,"name":"Chenhao Zhao","email":"","orcid":"","institution":"The Second Affiliated Hospital of Anhui Medical University","correspondingAuthor":false,"prefix":"","firstName":"Chenhao","middleName":"","lastName":"Zhao","suffix":""},{"id":498174841,"identity":"f9531b9a-d1c7-4783-883a-369af17dc856","order_by":1,"name":"Youping Tao","email":"","orcid":"","institution":"the Ninth Medical Center, Chinese PLA General Hospital","correspondingAuthor":false,"prefix":"","firstName":"Youping","middleName":"","lastName":"Tao","suffix":""},{"id":498174843,"identity":"151b1d0d-5fde-45cc-9809-c4accdaaba18","order_by":2,"name":"Qiangqiang Guo","email":"","orcid":"","institution":"PLA 306 Clinical College, Anhui Medical University","correspondingAuthor":false,"prefix":"","firstName":"Qiangqiang","middleName":"","lastName":"Guo","suffix":""},{"id":498174846,"identity":"f89765fe-441d-42be-8899-8d0fbd30b47a","order_by":3,"name":"Jiaxu Wang","email":"","orcid":"","institution":"the Ninth Medical Center, Chinese PLA General Hospital","correspondingAuthor":false,"prefix":"","firstName":"Jiaxu","middleName":"","lastName":"Wang","suffix":""},{"id":498174849,"identity":"9a952c84-797e-4f03-96ab-feff96d6dea6","order_by":4,"name":"Jing Sun","email":"","orcid":"","institution":"the Ninth Medical Center, Chinese PLA General Hospital","correspondingAuthor":false,"prefix":"","firstName":"Jing","middleName":"","lastName":"Sun","suffix":""},{"id":498174851,"identity":"269bad95-79c7-4a2d-a2e6-9c245c7ac5ef","order_by":5,"name":"Ruyue Li","email":"","orcid":"","institution":"PLA 306 Clinical College, Anhui Medical University","correspondingAuthor":false,"prefix":"","firstName":"Ruyue","middleName":"","lastName":"Li","suffix":""},{"id":498174852,"identity":"db24fcdf-0ca7-49bb-8a74-b57dd425295f","order_by":6,"name":"Xiaoming Ma","email":"","orcid":"","institution":"PLA 306 Clinical College, Anhui Medical University","correspondingAuthor":false,"prefix":"","firstName":"Xiaoming","middleName":"","lastName":"Ma","suffix":""},{"id":498174853,"identity":"f13b058a-ee72-49dc-bd8f-86f5447500b0","order_by":7,"name":"Jigong Wu","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAArklEQVRIiWNgGAWjYDCCA0AswWDDw8/eQJqWNBnJngOkaGFgOGxjcMOBSB18x5ufSVj8Os/DcIOB8cPHHCK0SJ45ZiYh2Xebh3F2A7PkzG1EaDG4kcN2Q7LnNg+zzAE2Zl4StJzjYZNIIEWLxI8DPDxEawH6xfyHZEMyjwTPwWbi/AIMscfGEn/s7O2PNx/88JEYLSDALNkGohgbiFQPUvvhD/GKR8EoGAWjYAQCAEmEN9j3a6rFAAAAAElFTkSuQmCC","orcid":"","institution":"The Second Affiliated Hospital of Anhui Medical University","correspondingAuthor":true,"prefix":"","firstName":"Jigong","middleName":"","lastName":"Wu","suffix":""}],"badges":[],"createdAt":"2025-07-21 09:08:40","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-7175445/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-7175445/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":88893785,"identity":"f90c2839-074e-44da-a74e-2664a6f8b130","added_by":"auto","created_at":"2025-08-12 12:58:18","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":13709464,"visible":true,"origin":"","legend":"\u003cp\u003eA 40-year-old female patient with severe kyphoscoliosis, with a main curve of 114°(\u003cstrong\u003eA\u003c/strong\u003e)and a kyphosis of 100° (\u003cstrong\u003eB\u003c/strong\u003e), After the osteotomy at T9 and correction, the main curve was corrected to 58° (\u003cstrong\u003eC\u003c/strong\u003e) and the kyphosis to 49° (\u003cstrong\u003eD\u003c/strong\u003e), with a good recovery.\u003c/p\u003e","description":"","filename":"Figure1AD.png","url":"https://assets-eu.researchsquare.com/files/rs-7175445/v1/5bd199448a96429f71de6c08.png"},{"id":88891429,"identity":"d9d78cf9-65b6-4356-a925-e9d14dde5ed7","added_by":"auto","created_at":"2025-08-12 12:50:19","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":40058335,"visible":true,"origin":"","legend":"\u003cp\u003e(\u003cstrong\u003eA\u003c/strong\u003e)Marking and measuring process of the spinal canal at the level of the pedicle on each vertebra. (\u003cstrong\u003eB\u003c/strong\u003e \u0026amp; \u003cstrong\u003eC\u003c/strong\u003e) The import of the patient's CT imaging data into the Mimics software for three-dimensional reconstruction. (\u003cstrong\u003eD\u003c/strong\u003e \u0026amp; \u003cstrong\u003eE\u003c/strong\u003e) The connection of corresponding points as the length of that segment of the spinal canal for measurement.\u003c/p\u003e","description":"","filename":"Figure2AE.png","url":"https://assets-eu.researchsquare.com/files/rs-7175445/v1/4c618892fac3efbcfb83a702.png"},{"id":88891416,"identity":"f9739249-20d1-4674-8af1-356ed46aec9a","added_by":"auto","created_at":"2025-08-12 12:50:18","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":7912959,"visible":true,"origin":"","legend":"\u003cp\u003eThe changes of spinal canal length (\u003cstrong\u003eA\u003c/strong\u003e)in the T1-S1 segment. (\u003cstrong\u003eB\u003c/strong\u003e)in each segment. (\u003cstrong\u003eC\u003c/strong\u003e)in the osteotomy segment. (\u003cstrong\u003eD\u003c/strong\u003e)The differences of spinal canal length between the concave and convex sides.\u003c/p\u003e","description":"","filename":"Figure3AD.png","url":"https://assets-eu.researchsquare.com/files/rs-7175445/v1/013ef4aab5b90b892e86163a.png"},{"id":88891414,"identity":"202eba2a-58db-4aad-b058-b160f5f82688","added_by":"auto","created_at":"2025-08-12 12:50:18","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":3290762,"visible":true,"origin":"","legend":"\u003cp\u003eThe linear correlation between spinal canal length changes and Cobb angle correction rates in each segment. (\u003cstrong\u003eA\u003c/strong\u003e) The upper complementary curve. (\u003cstrong\u003eB\u003c/strong\u003e) The main curve. (\u003cstrong\u003eC\u003c/strong\u003e) The lower complementary curve.\u003c/p\u003e","description":"","filename":"Figure4AC.png","url":"https://assets-eu.researchsquare.com/files/rs-7175445/v1/d4fe95af03d5594d35f856d0.png"},{"id":90875198,"identity":"de20c1f0-78f2-4906-88a0-3113e73bd407","added_by":"auto","created_at":"2025-09-09 08:47:26","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":59343890,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-7175445/v1/b12bfd13-3309-4808-b27b-e33b57ae0674.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"Uneven and Asymmetric Changes in Spinal Canal Length After Correction of Severe Kyphoscoliosis: A 3D CT-Based Study","fulltext":[{"header":"1. Introduction","content":"\u003cp\u003eScoliosis is a three-dimensional spinal deformity, and surgical treatment is an effective option for severe spinal deformities [\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e]. Severe kyphoscoliosis, characterized by complexity, rigidity, and large curve angles, presents a significant challenge in spinal surgery because of the difficulty of surgery, low correction rates, and high complication rates [\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e].\u003c/p\u003e\u003cp\u003eThe risk of neurological damage during scoliosis correction surgery is a serious concern, with severe scoliosis (Cobb angle\u0026thinsp;\u0026gt;\u0026thinsp;90\u0026deg;) being one of the risk factors [\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e]. Cases were reported that permanent neurological injuries happened after correction of severe kyphoscoliosis [\u003cspan additionalcitationids=\"CR5\" citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e]. A review in 2011 of 11,741 cases found a rate of 0.99% of postoperative neurological damage in teenagers under 21 years old with scoliosis, with a rate of 0.73% for adolescent idiopathic scoliosis [\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e], while an analysis of 108 patients over a 10-year period treated with lumbar pedicle subtraction osteotomies (PSOs) showed neurological deficits were seen in 12 patients (11.1%) and were permanent in 3 patients (2.8%) [\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e].\u003c/p\u003e\u003cp\u003eNeurological injuries in spinal deformity surgery are mainly attributed to surgical technical factors such as hematoma compression and misplaced screws, and also, excessive changes in spinal canal length [\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e]. Modi et al. demonstrated on pigs that spinal cord injury can occur with excessive shortening of the spinal canal [\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e]. Yang et al. also found on pigs that excessive distraction of the spinal canal can also lead to spinal cord injury [\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e].\u003c/p\u003e\u003cp\u003eTherefore, knowing the characteristics of changes in spinal canal length before and after surgery in severe kyphoscoliosis is of clinical importance for surgical strategy and prevention of postoperative neurological complications. However, these changes are not yet fully understood. This study aims to explore the characteristics of spinal canal length changes in the correction of severe kyphoscoliosis.\u003c/p\u003e"},{"header":"2. Materials and Methods","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e\u003ch2\u003e2.1 Study Subjects\u003c/h2\u003e\u003cp\u003eA retrospective analysis was performed on the imaging data of patients aged 18 or above with severe kyphoscoliosis who underwent osteotomy surgery at our center between November 2021 and May 2024. Inclusion Criteria: Presence of only a single structural thoracic or thoracolumbar curve; Coronal Cobb angle of the structural curve\u0026thinsp;\u0026ge;\u0026thinsp;90\u0026deg; (measured on pre-operative standing radiographs); Patients undergoing primary surgery; Completion of pre-operative and post-operative full-spine CT scans. Exclusion Criteria: Presence of more than one structural curve; Intraspinal pathologies (e.g. tethered cord, syringomyelia); Spinal conditions affecting measurement accuracy (e.g. severe segmentation failure, severe spinal stenosis); History of previous spinal surgery.\u003c/p\u003e\u003cp\u003eA total of 11 patients were ultimately enrolled, comprising 2 males and 9 females. The mean age was 36\u0026thinsp;\u0026plusmn;\u0026thinsp;9 years (range: 23\u0026ndash;47 years). The structural curves were located between T5 and L2. Radiological examinations showed no intraspinal neural abnormalities. All patients were undergone with three-column osteotomies (3COs), and all performed by the same surgeon team, as exampled in Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec4\" class=\"Section2\"\u003e\u003ch2\u003e2.2 Study Methods\u003c/h2\u003e\u003cdiv id=\"Sec5\" class=\"Section3\"\u003e\u003ch2\u003e2.2.1 Three-Dimensional Model Reconstruction\u003c/h2\u003e\u003cp\u003eAccording to previous studies [\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e, \u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e], all patients' preoperative and postoperative whole-spine computed tomography (CT) images were imported into the 3D modeling software Mimics 21.0 (Materialise NV, Belgium) to reconstruct 3D models of the entire spine. On the level of the pedicle, detailed points were marked on the cross-section of the spinal canal: the midpoint of the right and left pedicle, the posterior edge of the vertebral body (anterior side), the connection point in front of the spinous process (posterior side), and the geometric center point of the spinal canal (center), as shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec6\" class=\"Section3\"\u003e\u003ch2\u003e2.2.2 Parameter Measurement\u003c/h2\u003e\u003cp\u003eThe lines connecting the respective points of the anterior, posterior, left, right, and center of each vertebra were approximated as the length of that segment of the spinal canal. The lengths of the spinal canal in the T1-S1 range, in the main curve and upper and lower compensatory curve ranges, and in the osteotomy segment range (the range of the top vertebra and its adjacent vertebrae) were measured. The differences of the length changes between the concave and convex sides before and after surgery were compared, and the correlation between the length changes and the Cobb angle correction rate of the corresponding segment was analyzed.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec7\" class=\"Section3\"\u003e\u003ch2\u003e2.2.3 Data Analysis\u003c/h2\u003e\u003cp\u003eStatistical data analysis was performed using SPSS 26.0 software, with data presented as mean\u0026thinsp;\u0026plusmn;\u0026thinsp;SD. Paired t-tests were used to compare the differences of spinal canal length in each segment before and after surgery, as well as the changes between the concave and convex sides (All continuous data passed the Shapiro-Wilk tests). The difference of the spinal canal length and the corresponding segment Cobb angle change value were analyzed for linear correlation. A two-tailed P-value of less than 0.05 was considered statistically significant.\u003c/p\u003e\u003c/div\u003e\u003c/div\u003e"},{"header":"3. Results","content":"\u003cdiv id=\"Sec9\" class=\"Section2\"\u003e\u003ch2\u003e3.1 Preoperative and Postoperative Cobb Angle Improvement\u003c/h2\u003e\u003cp\u003eThere was a significant improvement of the structural curve Cobb angles in the 11 patients before and after the operation (P\u0026thinsp;\u0026lt;\u0026thinsp;0.05). The main curve correction rate was (42.5%\u0026plusmn;7.3%), and the correction rates for the upper and lower compensatory curves were (50.2%\u0026plusmn;3.1%) and (57.5%\u0026plusmn;4.6%), as shown in Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e.\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\u003ePreoperative and Postoperative Cobb Angle Correction (\u0026deg;)\u003c/p\u003e\u003c/div\u003e\u003c/caption\u003e\u003ccolgroup cols=\"9\"\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=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c7\" colnum=\"7\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c8\" colnum=\"8\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c9\" colnum=\"9\"\u003e\u003c/div\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\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\u003eDifference\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c5\"\u003e\u003cp\u003eCorrection Rate (%)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c6\"\u003e\u003cp\u003et\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colspan=\"3\" nameend=\"c9\" namest=\"c7\"\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\u003eUpper Curve\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e60.3\u0026thinsp;\u0026plusmn;\u0026thinsp;16.4\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e34.6\u0026thinsp;\u0026plusmn;\u0026thinsp;16.6\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e25.6\u0026thinsp;\u0026plusmn;\u0026thinsp;15.1\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e50.2\u0026thinsp;\u0026plusmn;\u0026thinsp;3.1\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e5.616\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colspan=\"3\" nameend=\"c9\" namest=\"c7\"\u003e\u003cp\u003e\u0026lt;\u0026thinsp;0.001\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eMain Curve\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e112.6\u0026thinsp;\u0026plusmn;\u0026thinsp;13.2\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e56.3\u0026thinsp;\u0026plusmn;\u0026thinsp;14.5\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e56.4\u0026thinsp;\u0026plusmn;\u0026thinsp;12.5\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e42.5\u0026thinsp;\u0026plusmn;\u0026thinsp;7.3\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e15.005\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colspan=\"3\" nameend=\"c9\" namest=\"c7\"\u003e\u003cp\u003e\u0026lt;\u0026thinsp;0.001\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eLower Curve\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e48.0\u0026thinsp;\u0026plusmn;\u0026thinsp;19.9\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e21.5\u0026thinsp;\u0026plusmn;\u0026thinsp;11.1\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e26.5\u0026thinsp;\u0026plusmn;\u0026thinsp;12.6\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e57.5\u0026thinsp;\u0026plusmn;\u0026thinsp;4.6\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colspan=\"2\" nameend=\"c7\" namest=\"c6\"\u003e\u003cp\u003e6.975\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u003cp\u003e\u0026lt;\u0026thinsp;0.001\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colspan=\"1\" nameend=\"c9\" namest=\"c9\"\u003e\u0026nbsp;\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003ctfoot\u003e\u003ctr\u003e\u003ctd colspan=\"9\"\u003et: The value of paired-t test. P: two-tailed P-value with a significance level of 0.05.\u003c/td\u003e\u003c/tr\u003e\u003c/tfoot\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec10\" class=\"Section2\"\u003e\u003ch2\u003e3.2 T1-S1 Spinal Canal Length Changes\u003c/h2\u003e\u003cp\u003eFor the changes of T1-S1 spinal canal length, the concave side were significantly elongated at (5.0\u0026thinsp;\u0026plusmn;\u0026thinsp;7.0)mm (P\u0026lt;0.05), while the convex side were significantly shortened at (4.0\u0026thinsp;\u0026plusmn;\u0026thinsp;6.0)mm (P\u0026lt;0.05), with no significant change observed in the center (P\u0026thinsp;\u0026gt;\u0026thinsp;0.05), as presented in Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e(\u003cb\u003eA\u003c/b\u003e).\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec11\" class=\"Section2\"\u003e\u003ch2\u003e3.3 Segmental Spinal Canal Length Changes\u003c/h2\u003e\u003cp\u003eFor each segment, the structural curve that underwent osteotomy was significantly shortened (P\u0026lt;0.05) with the exception of concave side (P\u0026thinsp;\u0026gt;\u0026thinsp;0.05), while the upper and lower compensatory curves were significantly elongated (P\u0026lt;0.05), as shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e(\u003cb\u003eB\u003c/b\u003e).\u003c/p\u003e\u003cp\u003eWithin the main curve range, the convex side averaged a shortening of (16.0\u0026thinsp;\u0026plusmn;\u0026thinsp;6.5) mm, the center averaged a shortening of (9.0\u0026thinsp;\u0026plusmn;\u0026thinsp;6.1) mm, and the concave side showed no significant change.\u003c/p\u003e\u003cp\u003eWithin the osteotomy segment range, the convex side averaged a shortening of (15.4\u0026thinsp;\u0026plusmn;\u0026thinsp;6.4) mm, the center averaged a shortening of (10.1\u0026thinsp;\u0026plusmn;\u0026thinsp;5.9) mm, and the concave side showed no significant change, as shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e(\u003cb\u003eC\u003c/b\u003e).\u003c/p\u003e\u003cp\u003eIn the upper curve range, the convex side averaged an elongation of (2.6\u0026thinsp;\u0026plusmn;\u0026thinsp;2.9) mm, the concave side averaged an elongation of (5.3\u0026thinsp;\u0026plusmn;\u0026thinsp;2.7) mm, and the center averaged an elongation of (3.8\u0026thinsp;\u0026plusmn;\u0026thinsp;2.7) mm.\u003c/p\u003e\u003cp\u003eIn the lower curve range, the convex side averaged an elongation of (2.6\u0026thinsp;\u0026plusmn;\u0026thinsp;3.8) mm, the concave side averaged an elongation of (6.3\u0026thinsp;\u0026plusmn;\u0026thinsp;2.5) mm, and the center averaged an elongation of (6.2\u0026thinsp;\u0026plusmn;\u0026thinsp;2.9) mm.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec12\" class=\"Section2\"\u003e\u003ch2\u003e3.4 Differences in Spinal Canal Length Changes Between Concave and Convex Sides\u003c/h2\u003e\u003cp\u003eThere were significant differences of spinal canal changes between the concave and convex sides (P\u0026thinsp;\u0026lt;\u0026thinsp;0.05). In the upper and lower curve segments, the concave side elongated more than the convex side, while in the main curve segment and osteotomy region, the concave side shortened less than the convex side, as shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e(\u003cb\u003eD\u003c/b\u003e).\u003c/p\u003e\u003cp\u003eIn the upper curve segment, the concave side elongated more than the convex side by (2.6\u0026thinsp;\u0026plusmn;\u0026thinsp;1.3) mm; in the lower curve segment, the concave side elongated more than the convex side by (3.7\u0026thinsp;\u0026plusmn;\u0026thinsp;3.8) mm. And in the main curve segment, the concave side shortened less than the convex side by (15.3\u0026thinsp;\u0026plusmn;\u0026thinsp;4.8) mm; in the osteotomy region, the concave side shortened less than the convex side by (13.6\u0026thinsp;\u0026plusmn;\u0026thinsp;7.1) mm.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec13\" class=\"Section2\"\u003e\u003ch2\u003e3.5 Correlation Between Spinal Canal Length Changes and Cobb Angle Improvement\u003c/h2\u003e\u003cp\u003eThe correlation analysis between the changes in spinal canal length in each segment and the corresponding Cobb angle improvement rate showed no significant correlation (all R\u0026thinsp;\u0026lt;\u0026thinsp;0.4, P\u0026thinsp;\u0026gt;\u0026thinsp;0.05), as shown in Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e and Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\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\u003eThe correlation between spinal canal length changes and Cobb angle correction rates in each segment.\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=\"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\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u003cp\u003eConvex\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c3\"\u003e\u003cp\u003eConcave\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c4\"\u003e\u003cp\u003eCenter\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\" morerows=\"1\" rowspan=\"2\"\u003e\u003cp\u003eUpper Curve\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eR\u0026thinsp;=\u0026thinsp;0.131\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003eR\u0026thinsp;=\u0026thinsp;0.020\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003eR\u0026thinsp;=\u0026thinsp;0.016\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eP\u0026thinsp;=\u0026thinsp;0.700\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003eP\u0026thinsp;=\u0026thinsp;0.954\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003eP\u0026thinsp;=\u0026thinsp;0.964\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\" morerows=\"1\" rowspan=\"2\"\u003e\u003cp\u003eMain Curve\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eR\u0026thinsp;=\u0026thinsp;0.240\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003eR\u0026thinsp;=\u0026thinsp;0.387\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003eR\u0026thinsp;=\u0026thinsp;0.299\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eP\u0026thinsp;=\u0026thinsp;0.477\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003eP\u0026thinsp;=\u0026thinsp;0.240\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003eP\u0026thinsp;=\u0026thinsp;0.372\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\" morerows=\"1\" rowspan=\"2\"\u003e\u003cp\u003eLower Curve\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eR\u0026thinsp;=\u0026thinsp;0.272\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003eR\u0026thinsp;=\u0026thinsp;0.255\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003eR\u0026thinsp;=\u0026thinsp;0.104\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eP\u0026thinsp;=\u0026thinsp;0.418\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003eP\u0026thinsp;=\u0026thinsp;0.450\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003eP\u0026thinsp;=\u0026thinsp;0.761\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003ctfoot\u003e\u003ctr\u003e\u003ctd colspan=\"4\"\u003eR: correlation coefficient. P: two-tailed P-value with a significance level of 0.05.\u003c/td\u003e\u003c/tr\u003e\u003c/tfoot\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003c/div\u003e"},{"header":"4. Discussion","content":"\u003cp\u003eThis study used three-dimensional reconstruction technology to detail the changes in spinal canal length in severe kyphoscoliosis patients before and after 3CO surgery. Previous studies have reported varying ranges of spinal canal length changes in different types of scoliosis. Ni et al. measured approximate spinal canal length changes using X-rays, the range of spinal canal changes was \u0026minus;\u0026thinsp;1.23 to 2.82 cm in the center [\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e]. Yahara et al. used three-dimensional CT data to measure spinal canal length changes from T2 to L2 in adolescent idiopathic scoliosis (AIS) patients, reporting an average increase of 10.1 mm in the center [\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e].\u003c/p\u003e\u003cp\u003eOur findings indicate that the spinal canal after 3CO surgery tends to elongate on the concave side and shorten on the convex side, with the central length of the spinal canal remaining relatively stable from T1 to S1. Similarly, Han et al. retrospectively analyzed the changes in spinal canal length between the upper and lower end vertebrae and from T2 to L2 in 27 patients with idiopathic scoliosis. After the operation, the concave side of the spinal canal length increased, and the convex side of the spinal canal length significantly decreased [\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e].\u003c/p\u003e\u003cp\u003eHowever, our detailed segmental analysis firstly found that this pattern is attributed to the shortening effects of structural curve osteotomies and the elongation of upper and lower compensatory curves. Li et al. measured that three-column osteotomy could shorten the central spinal canal by 17 mm, and after the osteotomy, the convex side of the spinal canal in severe scoliosis patients shortened by 27.8 mm [\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e], showing similar conclusion with our study on the main curve range. But our measurements of the upper and lower compensatory curves found that while spinal canal shortening occurred in the structural curve segment, canal elongation was observed in compensatory curves. Although the central spinal canal length remained stable overall, uneven deformation patterns were demonstrated along the spinal canal.\u003c/p\u003e\u003cp\u003eMoreover, our study observed that the concave side elongates more than the convex side or shortens less, indicating a significant relative elongation effect on the concave side during spinal correction\u0026mdash;a pattern consistently seen in both structural curves and the main curve regions. Chu et al. and Yossi et al. respectively observed through magnetic resonance imaging (MRI) that the spinal cord runs along the concave side of the spinal canal in scoliosis [\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e, \u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e], suggesting a possible risk of neurological complication because of this uneven elongation of concave side. Han et al. measured the changes in spinal canal length from the upper and lower end vertebrae and from T2 to L2 in 10 severe scoliosis patients. They found that after correction, the Ponte osteotomy resulted in more elongation of the concave side than the convex side, while the vertebral column resection (VCR) osteotomy resulted in greater shortening of the convex side than the concave side [\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e], with similar conclusions with our study. And our study additionally found that this pattern remains consistent in each segment as well as across the entire spinal canal.\u003c/p\u003e\u003cp\u003eCusick et al. found in primate studies that acute traction of spinal cord fibers can cause spinal cord injury [\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e]. Yang et al. found in a goat model study that the safe limit for shortening of the spinal cord in thoracolumbar bivertebral column resections was (35.2\u0026thinsp;\u0026plusmn;\u0026thinsp;2.6) mm [\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e]. Qiu et al. also found in a goat model study that the safe limit for traction of the spinal column in spinal deformity surgery was (11.8\u0026thinsp;\u0026plusmn;\u0026thinsp;3.65) mm, and spinal cord injury in spinal deformity surgery may be related to excessive traction of the spinal cord during the surgical correction process [\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e]. Based on those data above, our elongation or shortening of spinal canal was remain safe during the surgeries. However, during correction, excessive distraction or compression of the spinal canal should still be avoided, and comprehensive intraoperative neuromonitoring remains crucial. Moreover, the applicability of these animal model findings to human spinal cord injury thresholds remains uncertain, necessitating further research to establish surgical reference values.\u003c/p\u003e\u003cp\u003eThis study has certain limitations. Firstly, as a single-center retrospective study, our conclusions may be influenced by the surgical team's practices, and different centers may have different results. Secondly, our study population was limited to patients with a single structural curve of severe scoliosis, with a small sample size, precluding further analysis of spinal canal length changes in patients with different types of scoliosis. Additionally, manual selection of data points may introduce minor errors, although these do not affect the overall trends observed in our study. Future work should expand the sample size and adopt multi-center studies to analyze and compare spinal canal length changes in patients with different curve types. Research directions should include exploring the biomechanical changes of spinal cord tension and the spinal canal.\u003c/p\u003e"},{"header":"5. Conclusion","content":"\u003cp\u003eIn summary, significant changes of spinal canal length were observed in patients with severe kyphoscoliosis after corrective osteotomy surgery. The central length of the entire spinal canal did not significantly change after the operation, but uneven changes were found on the main curve and compensatory curves. Asymmetric differences were observed of spinal canal changes between the concave and convex sides. No significant correlation was observed between segmental spinal canal length changes and corresponding Cobb angle correction rates. This study provides insights for the surgical strategies of severe kyphoscoliosis and the prevention of postoperative neurological complications.\u003c/p\u003e"},{"header":"Abbreviations","content":"\u003cp\u003e3CO: Three-Column Osteotomy\u003c/p\u003e\n\u003cp\u003eAIS: Adolescent Idiopathic Scoliosis\u003c/p\u003e\n\u003cp\u003eCT: Computed Tomography\u003c/p\u003e\n\u003cp\u003eMRI: Magnetic Resonance Imaging\u003c/p\u003e\n\u003cp\u003ePSO: Pedicle Subtraction Osteotomy\u003c/p\u003e\n\u003cp\u003eVCR: Vertebral Column Resection\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eEthics approval\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThis study was approved by the Ethics Committee of the Ninth Medical Center, Chinese PLA General Hospital (Approval No. LL-LSCY-2024-15) and conducted in accordance with the Declaration of Helsinki. \u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConsent\u0026nbsp;\u003c/strong\u003e\u003cstrong\u003eto participate\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eIndividual consent was waived for the retrospective analysis of anonymized data.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConsent for publication\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eWritten informed consent was obtained from the patient in Figure 1 for publication of radiographic images.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAvailability of data and materials\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe datasets used and/or analyzed during the current study are available from the corresponding author on reasonable request.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eCompeting interests\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors declare no competing interests.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFunding\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThis study did not receive any specific funding.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAuthor contributions\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eC.Z.: writing of the main manuscript text, measurement and analysis of data, figure preparation. Y.T.:\u0026nbsp;interpretation of data, review and editing. Q.G.: identification and optimism of the measurement methodology. Jiaxu W, J.S, R.L\u0026amp;X.M: interpretation and acquisition of data. Jigong W.: design of the work, review and editing, supervision.\u003c/p\u003e\n\u003cp\u003eAll authors have read and approved the final submitted manuscript.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eClinical trial number\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eNot Applicable.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003eQiu G, Li Q, Wang Y, Zhang J, Shen, J, Weng Y, et al. [The operation treatment for severe and rigid idiopathic scoliosis]. National Medical Journal of China.2005; 85(12):807-810.\u003c/li\u003e\n\u003cli\u003eHai Y, Chen Z, Ma H, Wu J, Chen X, Zou D, et al. [Surgical treatment of severe kyphoscoliosis]. 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National Medical Journal of China.2019; 99(41):3243-3248.\u003c/li\u003e\n\u003cli\u003eCusick JF, Myklebust J, Zyvoloski M, Sances JA, Houterman C, Larson SJ. Effects of vertebral column distraction in the monkey. J Neurosurg.1982; 57(5):651.\u003c/li\u003e\n\u003cli\u003eYang H, Wang B, Zou X, Ge S, Chen Y, Zhang S, et al. Safe limit of shortening of the spinal cord in thoracolumbar bivertebral column resections: an experimental study in goats. World Neurosurg.2020; 134: e589-e595.\u003c/li\u003e\n\u003cli\u003eQiu F, Yang J, Ma X, Xu J, Yang Q, Zhou X, et al. Influence of vertebral column distraction on spinal cord volume: an experimental study in a goat model. Arch Orthop Trauma Surg.2015; 135(9):1201-1210.\u003c/li\u003e\n\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":"Scoliosis, Spinal Canal Length, Spinal cord injury, Three-dimensional Computed Tomography","lastPublishedDoi":"10.21203/rs.3.rs-7175445/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-7175445/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003e\u003cstrong\u003eBackground: \u003c/strong\u003eChanges in spinal canal length in severe kyphoscoliosis are critical for surgical strategy and preventing neurological complications. However, the specifics of these changes are not fully understood.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eObjective: \u003c/strong\u003eThis study investigates spinal canal length changes in severe kyphoscoliosis correction.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eMethods: \u003c/strong\u003eSevere kyphoscoliosis patients (Cobb angle \u0026gt; 90°) were retrospectively analyzed. 3D models from CT images were constructed using Mimics software to measure spinal canal on cross-sections at the pedicle level. Lengths of the spinal canal were measured across various segments and compared between concave and convex sides. Correlation with Cobb angle correction rates was analyzed.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eResults: \u003c/strong\u003eThe study finally enrolled 11 patients.\u003cstrong\u003e \u003c/strong\u003eAfter surgery, the main curve Cobb angle improved by 42.5%±7.3%. The concave side of T1-S1 elongated by (5.0±7.0) mm, while the convex side shortened by (4.0±6.0) mm (P\u0026gt;0.05 for center). Within the main curve, the convex side shortened by (16.0±6.5) mm, and the center by (9.0±6.1) mm (P\u0026gt;0.05 for concave side). In compensatory curves, all sides elongated more on the concave side. In the osteotomy segment, each side showed significant shortening except the concave side. No significant correlation between segmental spinal canal length changes and Cobb angle correction rates.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConclusion: \u003c/strong\u003eCentral spinal canal length remained stable post-operation, but uneven changes were found on the main curve and compensatory curves. Asymmetric differences were observed of spinal canal changes between the concave and convex sides. differences were noted between concave and convex sides. There was no correlation between length changes and Cobb angle correction rates, The study provides insights for surgical strategies and neurological complication prevention.\u003c/p\u003e","manuscriptTitle":"Uneven and Asymmetric Changes in Spinal Canal Length After Correction of Severe Kyphoscoliosis: A 3D CT-Based Study","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-08-12 12:50:13","doi":"10.21203/rs.3.rs-7175445/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":"8735245a-a2b9-459d-8192-fe236ad68a4b","owner":[],"postedDate":"August 12th, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[],"tags":[],"updatedAt":"2025-09-09T08:38:18+00:00","versionOfRecord":[],"versionCreatedAt":"2025-08-12 12:50:13","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-7175445","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-7175445","identity":"rs-7175445","version":["v1"]},"buildId":"XKTyCvWXoU3ODBz1xrDgd","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}