Radiographic Assessment and Risk Model of Atlantoaxial Instability Induced by Halo-Pelvic Traction in Treating Severe Spinal Deformity

Radiographic Assessment and Risk Model of Atlantoaxial Instability Induced by Halo-Pelvic Traction in Treating Severe Spinal Deformity | 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 Radiographic Assessment and Risk Model of Atlantoaxial Instability Induced by Halo-Pelvic Traction in Treating Severe Spinal Deformity Lijin Zhou, Haoshuang Geng, Jianqiang Wang, Yong Hai This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-6744315/v1 This work is licensed under a CC BY 4.0 License Status: Published Journal Publication published 25 Aug, 2025 Read the published version in European Spine Journal → Version 1 posted 9 You are reading this latest preprint version Abstract PURPOSE: Halo-pelvic traction (HPT) is widely used for managing severe rigid scoliosis by enhancing surgical safety. However, complications such as atlantoaxial instability may occur during traction. This study aimed to identify the risk factors for atlantoaxial instability during HPT and assess whether instability is reversible after traction. Additionally, a radiographic criterion based on the lateral mass interval (LMI) was proposed to define this condition. METHODS: A retrospective study was conducted on patients who underwent HPT followed by posterior spinal fusion between March 2014 and August 2022. Atlantoaxial alignment was assessed pre-traction, post-traction, and postoperatively using LMI. Patients were categorized into stable and unstable groups. Risk factors were identified through univariate and multivariable logistic regression analyses, and a nomogram was constructed based on the final predictive model. RESULTS: Among fifty-nine patients, forty-five developed atlantoaxial instability during traction. All cases were radiographically reversible postoperatively. Multivariable analysis identified younger age (OR = 0.893, P = 0.005) and increased pelvic tilt (PT) (OR = 1.137, P = 0.048) as independent risk factors. The predictive model showed good discrimination (AUC = 0.817). CONCLUSION: Atlantoaxial instability during HPT is transient and reversible. LMI is a reliable radiographic indicator for its assessment. Younger age and increased PT are significant predictors, and the proposed nomogram may aid in pre-traction risk stratification. Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Introduction Severe and rigid spinal deformities were defined as a cobb angle greater than 100 degrees and flexibility less than 30% [ 1 , 2 ]. Treating severe spinal deformities poses significant challenges. Although high-level osteotomy is a treatment option, it is associated with a steep learning curve and substantial blood loss; rapid correction of severe spinal deformities can also lead to spinal cord traction injuries[ 3 , 4 ]. Halo-pelvic traction (HPT), first introduced by O’Brien et al. in 1973 for the treatment of scoliosis, comprises a halo ring, a pelvic ring, and adjustable connecting rods that enable gradual deformity correction over time [ 5 , 6 ]. HPT can achieve 33–45% correction of scoliosis and 49–55% correction of kyphosis before the surgery and significantly enhance surgical safety [ 7 – 9 ]. Additionally, HPT has been proven to safely and effectively improve pulmonary function in patients during traction [ 10 ]. However, HPT has some drawbacks, including neck stiffness, neurological symptoms, pin infections, skin infections, and atlantoaxial instable[ 11 ]. Vertical instability of the atlantoaxial joint is a clinically significant yet understudied spinal condition characterized by misalignment between the atlas (C1) and axis (C2) in the vertical plane. This pathological condition can result in severe complications, including severe neurological complications, and in extreme cases, death[ 12 – 14 ]. During the process, HPT applies vertical forces to the patient. Because the atlantoaxial joint lacks the typical vertebral body structure, making the articular system primarily dependent on ligaments, it is relatively fragile and susceptible to dislocation during traction [ 15 ]. Therefore, this study aims to identify suitable methods for evaluating the atlantoaxial relationship during HPT, investigate the effects of HPT on the vertical distance between C1 and C2, and assess the safety of this procedure. Additionally, we aim to determine the risk factors contributing to atlantoaxial instability, develop a predictive model based on these factors, and provide a clinically applicable tool to assist in identifying patients at high risk of instability during halo-pelvic traction. Materials and Methods Patient cohort This single-center retrospective cohort study was conducted from March 2014 to August 2022 at Beijing Chao-Yang Hospital. Fifty-nine patients with severe scoliosis who underwent preoperative HPT were retrospectively included. The inclusion criteria were as follows: 1) patients with severe kyphoscoliosis (a coronal cobb angle or kyphosis angle of >100º); 2) patients who underwent HPT before the final fusion. The exclusion criteria were prior spinal surgery and inadequate visualization of the atlantoaxial joint structure on CT imaging. This study was approved by the Research Ethics Committee of Beijing Chao-Yang Hospital, and informed consent was obtained from patients. Baseline characteristics and neurological complications Demographic data included the patient’s sex, age, body mass index (BMI), type of scoliosis, duration of traction, and the position of the apex vertebra of the primary curve. The type of scoliosis was categorized as idiopathic scoliosis (IS), congenital scoliosis (CS), and neuromuscular scoliosis (NMS). The apex vertebra was classified in to thoracic group and lumbar group according to its location. In addition, neurological complications occurring during traction were recorded, including dysphagia, dysarthria, muscle weakness, paresthesia, and urinary or bowel dysfunction. Radiographic Parameters Standing full-length coronal and sagittal radiographs were collected before and after the HPT process, and the changes in the spinal parameters were assessed. Coronal plane measurements included: 1) cobb angle of the primary curve; 2) apical vertebral translation (AVT); 3) distance from the C7 plumb line to the sacral vertical line (C7PL-CSVL). Sagittal plane measurements included: 1) focal kyphosis (FK); 2) T5-T12 kyphosis (TK); 3) lumbar lordosis (LL); 4) pelvic tilt (PT); 5) sacral slope (SS); 6) T1 pelvic angle (TPA); 7) sagittal vertical axis (SVA). HPT protocols With the patient under general anesthesia and in the lateral position, a 4.0 mm diameter pin was inserted through the skin at the thickest part of the ilium, midway between the anterior superior iliac spine and the posterior superior iliac spine on one side. The same procedure was then performed on the other side. After placing the patient in the supine position, ten halo pins were inserted at the maximum circumference of the skull anteriorly and laterally and connected to the halo ring. The connecting rods and pelvic ring were assembled three to five days later to allow the patient to adapt to the pins. Once the frame assembly was completed, traction was initiated, increasing gradually by 0.5 cm per day. The traction was discontinued when any of the following occurred: (1) the patient was unable to tolerate the traction, (2) the primary curve Cobb angle was reduced by more than 50%, (3) new neurological symptoms emerged, or (4) lateral cervical radiographs indicated that the patient exhibited atlantoaxial intolerance to traction. The criterion for determining intolerance to traction at the atlantoaxial joint was defined as the tip of the odontoid process contacting the anterior arch of the atlas at or below its lower one-third (Fig. 1 ) (Fig. 2 ). The evaluation of vertical atlantoaxial subluxation Full-length spinal CT scans obtained before traction, after traction, and postoperatively were independently evaluated by two researchers. The shortest distance between the lateral masses of C-1 and C-2 was measured on planes perpendicular to the articular surfaces on the right and left sides, respectively, and defined as the Lateral Mass Interval (LMI). Three measurements were taken for each patient, and the average left and right LMI values were calculated. The normal values for the LMI range from 0.7mm to 2.6 mm, and an LMI greater than 2.6 mm on either side indicates instability in the atlantoaxial area [ 13 ] (Fig. 3 ). Statistical Analysis All statistical analyses were performed using IBM SPSS Statistics, version 29 (IBM Corporation, Armonk, NY, USA). The Shapiro–Wilk test was conducted to assess the normality of continuous variables. Continuous variables with a normal distribution are presented as mean ± standard deviation (SD), whereas non-normally distributed variables are expressed as median and interquartile range (IQR). Categorical variables are summarized as counts and percentages. Patients were divided into two groups based on the presence of atlantoaxial subluxation. For continuous variables, comparisons between groups were performed using independent samples t-tests if normally distributed; otherwise, the Mann–Whitney U test was applied. Categorical variables were compared using the chi-square test. Variables with a P value < 0.1 in the univariate analysis were included in a multivariable logistic regression model to identify independent risk factors, using the backward: Wald method. A nomogram and a receiver operating characteristic (ROC) curve were generated based on the multivariate logistic regression model. In addition, patients were evaluated at three time points (pre-traction, post-traction, and postoperative). Comparisons were conducted using the least significant difference (LSD) test. A two-tailed P value < 0.05 was considered statistically significant. We present this article in accordance with the STROBE reporting checklist Results Baseline characteristics Fifty-nine patients (21 males and 38 females) who underwent HPT were retrospectively recruited in this study. Atlantoaxial instability occurred in 45 patients, while 14 patients remained stable during halo-pelvic traction. The mean age at surgery was 26.15 ± 9.66 years, and the mean BMI was 19.59 ± 3.49. The average traction duration was 19.44 ± 4.39 weeks. The etiological diagnoses were neuromuscular scoliosis (n = 2), idiopathic scoliosis (n = 16), and congenital scoliosis (n = 41). During traction, one patient experienced dysphagia and dysarthria, three patients experienced upper limb muscle strength reduction; these symptoms resolved after surgery. No patients experienced paresthesia or urinary and bowel dysfunction. A significant age difference was observed between the unstable and stable groups (24.02 years ± 9.11 years vs. 33.00 years ± 8.31 years, P = 0.002). There were no significant differences between sex, BMI, type of scoliosis, duration of traction, and the apex vertebra position (Table 1 ). Table 1 Comparison of baseline data between Stable and Unstable atlantoaxial groups during traction Stable (n = 14) Unstable (n = 45) P Value Age (years) 33.00 ± 8.31 24.02 ± 9.11 0.002 Gender Male Female 6 (42.9%) 8 (57.1%) 15 (33.3%) 30 (66.7%) 0.538 Body mass index (BMI) 20.27 ± 3.25 19.38 ± 3.57 0.407 Type of scoliosis NMS IS CS 1 (7.1%) 2 (14.3%) 11 (78.6%) 1 (2.2%) 14 (31.1%) 30 (66.7%) 0.345 Duration of traction (weeks) 19.79 ± 3.47 19.33 ± 4.67 0.740 Apex vertebra position T L 9 (64.3%) 5 (35.7%) 38 (86.4%) 6 (13.6%) 0.112 NMS indicates neuromuscular scoliosis; AIS, idiopathic scoliosis; CS, congenital scoliosis; T, thoracic; L, lumbar Radiographic parameters The FK (118.44º ± 32.71º vs. 99.94º ± 33.83º, P = 0.077), AVT (106.40mm ± 35.88mm vs. 84.67mm ± 35.82mm, P = 0.050) and C7PL-CSVL (41.33mm ± 35.18mm vs. 22.81mm ± 21.32mm, P = 0.019) in the stable group were significantly higher than in the unstable group. Additionally, the PT (7.19° ± 5.86° vs. 11.75° ± 7.67°, P = 0.046) in the stable group was significantly lower than in the unstable group. The groups had no significant differences in other radiographic parameters (Table 2 ). Table 2 Comparison of radiographic parameters between Stable and Unstable atlantoaxial groups during traction Stable Unstable P Value Main Cobb angle (º) 129.74 ± 22.92 116.44 ± 41.65 0.260 FK (º) 118.44 ± 32.71 99.94 ± 33.83 0.077 TK (º) 93.01 ± 31.21 85.19 ± 32.01 0.425 LL (º) 71.34 ± 23.66 63.70 ± 21.58 0.263 PT (º) 7.19 ± 5.86 11.75 ± 7.67 0.046 SS (º) 28.49 ± 8.75 24.75 ± 9.45 0.194 TPA (º) 5.65 ± 3.89 8.15 ± 5.81 0.138 SVA (mm) 20.22 ± 23.43 15.17 ± 22.20 0.467 AVT (mm) 106.40 ± 35.88 84.67 ± 35.82 0.050 C7PL-CSVL (mm) 41.33 ± 35.18 22.81 ± 21.32 0.019 Cobb correction rate (%) 48.19 ± 19.39 53.19 ± 13.59 0.284 MK correction rate (%) 41.66 ± 18.05 51.23 ± 21.58 0.139 FK indicates focal kyphosis; TK, thoracic kyphosis; LL, lumbar lordosis; PT, pelvic tilt; SS, sacral slope; TPA, T1 pelvic angle; SVA, sagittal vertical axis; AVT, apical vertebral translation; C7PL, C7 plumb line; CSVL, center sacral vertical line Multivariate Logistic regression Multivariate logistic regression found that younger age and increased PT were associated with a higher risk of instability (OR = 0.893, 95% CI: 0.826–0.966, P = 0.005), (OR = 1.137, 95% CI: 1.001–1.292, P = 0.048). The Hosmer–Lemeshow goodness-of-fit test indicated an adequate model fit (P = 0.653). ROC curve analysis demonstrated that the model had good discriminatory ability, with an AUC of 0.817 (95% CI: 0.689–0.946). The optimal cutoff value, determined by Youden’s index (0.633), corresponded to a sensitivity of 0.889 and a specificity of 0.286 (Fig. 4 ). A nomogram was constructed based on the multivariable logistic regression model (Fig. 5 ). Vertical atlantoaxial instable Before traction, none of the patients had atlantoaxial instability. However, it developed in 45 patients during traction. Both right and left LMIs significantly increased from pre-traction to post-traction (right: 1.52 ± 0.46 mm vs. 4.03 ± 2.47 mm, P < 0.001; left: 1.43 ± 0.42 mm vs. 3.94 ± 2.16 mm, P < 0.001). After surgery, both right and left LMIs significantly decreased compared to post-traction values (right: 4.03 ± 2.47 mm vs. 1.41 ± 0.40 mm, P < 0.001; left: 3.94 ± 2.16 mm vs. 1.32 ± 0.50 mm, P < 0.001). There was no significant difference in either right or left LMIs between pre-traction and postoperative measurements (right: 1.52 ± 0.46 mm vs. 1.41 ± 0.40 mm, P = 0.108; left: 1.43 ± 0.42 mm vs. 1.32 ± 0.50 mm, P = 0.069) (Table 3 ). Table 3 Comparison of right LMI and left LMI pre-traction, post-traction, and postoperative P Value Pre-traction Post-traction Postoperative Pre-traction vs. Post-traction Post-traction vs. Postoperative Postoperative vs. Pre-traction Right LMI (mm) 1.52 ± 0.46 4.03 ± 2.47 1.41 ± 0.40 < 0.001 < 0.001 0.108 Left LMI (mm) 1.43 ± 0.42 3.94 ± 2.16 1.32 ± 0.50 < 0.001 < 0.001 0.069 Discussion Atlantoaxial instability is one of the major complications associated with HPT; however, limited studies have specifically addressed this issue [ 11 , 16 , 17 ]. To our knowledge, this is the first study to evaluate atlantoaxial instability during halo-pelvic traction. Based on the exaggerated movements in different directions affecting the C1-C2 joint, atlantoaxial instability can be classified into vertical, anteroposterior, and rotational types [ 13 , 15 ]. Given the structure design of the HPT frame, which exerts a predominantly vertical force relative to the transverse plane of the body, the instability observed during traction is primarily of the vertical type. The clinical manifestations of atlantoaxial instability vary widely; initial symptoms may include mild axial neck pain and paresthesia. Although uncommon, severe spinal cord injury during traction may lead to fatal outcomes [ 18 – 20 ]. According to Gonzalez et al. [ 13 ], an LMI greater than 2.6 mm on either side between C1 and C2 suggests instability of the atlantoaxial joint. Our study found that forty-five patients undergoing HPT in our hospital experienced atlantoaxial instability during the traction period. However, postoperative LMI showed that the patient's atlantoaxial joint had returned to its normal anatomical position, with no significant differences on either side compared to before the traction (1.41mm ± 0.40mm vs. 1.52mm ± 0.46mm, P = 0.108); (1.32mm ± 0.50mm vs. 1.43mm ± 0.42mm, P = 0.069). During the traction process, one patient experienced dysphagia and dysarthria, three patients experienced upper limb muscle strength reduction. The symptoms resolved after the final fusion surgery was performed. Wang et al. [ 16 ], in a study of sixty-two patients undergoing HPT, found that only one patient experienced atlantoaxial instablity, which completely resolved in subsequent follow-ups, and no patients suffered permanent neurological deflect. Similarly, Qi et al. [ 17 ], in treating thirty patients with severe spinal deformities using halo-pelvic rings, found that patients who experienced neck discomfort during the traction process all had their symptoms resolved after surgery. Dove et al. [ 21 ] followed up with eighty-three patients who underwent halo-pelvic traction and found that only one patient developed atlantoaxial instability six years after the procedure. Previous studies on HPT have lacked standardized criteria for defining atlantoaxial instability. As a result, existing literature may have reported only cases of severe dislocation, potentially overlooking subtle or partial forms. Our study is the first to propose a quantitative definition of atlantoaxial subluxation based on lateral mass interval (LMI), thereby providing a more sensitive and objective framework for assessing C1–C2 instability during traction. Our study found that younger age is an independent risk factor associated with atlantoaxial instability (OR = 0.893, 95% CI: 0.826–0.966, P = 0.005), which may be attributed to the higher ligamentous laxity, incomplete skeletal and joint development, and reduced muscular stability in younger individuals. Additionally, patients with atlantoaxial instability during HPT exhibited significantly higher PT compared to the stable group. Multivariable logistic regression confirmed that increased PT was an independent risk factor for atlantoaxial subluxation (OR = 1.137, 95% CI: 1.001–1.292, P = 0.048). An increased PT reflects sagittal imbalance, typically indicating compensatory posterior pelvic rotation to maintain upright posture. During halo-pelvic traction, a higher PT may serve as an indicator of sagittal malalignment. Our findings suggest that such sagittal imbalance is associated with a higher risk of atlantoaxial instability during traction. A predictive model incorporating patients’ PT and age demonstrated good discriminative ability, with an AUC of 0.817. This result indicates that the combination of these two variables provides a reliable and clinically meaningful prediction of atlantoaxial instability, supporting the potential utility of these parameters in pre-traction risk assessment. The key factor in treating vertical atlantoaxial instability is to protect the stability of the cervical spine [ 13 ]. The HPT frame does precisely this, ensuring stability by limiting cervical spine movement—a factor typically seen as a disadvantage. Interestingly, this restriction protects the cervical spine when instability occurs due to traction. Research indicates that using a rigid cervical collar or halo fixation is a reliable method for treating atlantoaxial instability without fractures [ 20 , 22 ]. Moreover, because the HPT pulls vertically by only 0.5 cm per day and the entire traction process lasts for several months, the force and distance of traction on the patient gradually increase, allowing sufficient time to adapt to the traction. Patients who underwent HPT in our hospital had their atlantoaxial joints return to regular anatomical positions after removing the traction frame, proving that HPT does not cause irreversible damage to the critical ligaments and joints that maintain atlantoaxial stability. In our study, no patients experienced permanent neurological damage or death due to atlantoaxial instability. Limitations There are several limitations in this study. First, the small sample size may limit the statistical power of the study, and larger cohorts are needed to validate the findings. Second, as a single-center retrospective study, there is a risk of selection bias and unmeasured confounding factors. Third, the absence of cervical MRI data during traction and after surgery prevents direct evaluation of the atlantoaxial ligamentous structures. Fourth, long-term follow-up is required to assess the stability and progression of the atlantoaxial joint over time. Conclusions This article utilized the method of measuring the LMI on CT scans to assess atlantoaxial instability and found that after removing the halo-pelvic frame, patients' atlantoaxial joint space could return to pre-traction level. Multivariable logistic regression analysis identified younger age and increased PT as independent risk factors for atlantoaxial instability during HPT. Based on these variables, we constructed a nomogram to support clinical decision-making. This tool may help identify high-risk patients before traction, enabling timely preventive strategies and improved safety during preoperative management. Declarations Author Contribution L.Z contributed to the study design and conceptualization.H.G and J.W were responsible for data collection and radiographic assessment.Statistical analysis was conducted by H.G.The first draft of the manuscript was written by H.G, and all authors contributed to reviewing and editing the manuscript.Y.H supervised the project design and overall study process, and approved the final version of the manuscript. References Chang KW (2003) Cantilever bending technique for treatment of large and rigid scoliosis. Spine (Phila Pa 1976) 28(21):2452–2458. http://dx.doi.org/10.1097/01.Brs.0000092063.63315.D5 Kandwal P et al (2017) Severe Rigid Scoliosis: Review of Management Strategies and Role of Spinal Osteotomies. Asian Spine J 11(3):494–503. http://dx.doi.org/10.4184/asj.2017.11.3.494 Xia L et al (2015) Spinal osteotomy techniques in management of severe pediatric spinal deformity and analysis of postoperative complications. Spine (Phila Pa 1976) 40(5):E286. 92.http://dx.doi.org/10.1097/brs.0000000000000728 Aydinli U et al (2018) Results of Posterior Vertebral Column Resection: Surgical Modification of Suk Technique. Global Spine J 8(5):478–482. http://dx.doi.org/10.1177/2192568217739854 Yang C et al (2017) Halo-gravity traction in the treatment of severe spinal deformity: a systematic review and meta-analysis. Eur Spine J 26(7):1810–1816. http://dx.doi.org/10.1007/s00586-016-4848-y O'Brien JP, Yau AC, Hodgson AR (1973) Halo pelvic traction: a technic for severe spinal deformities. Clin Orthop Relat Res 93179–190. http://dx.doi.org/10.1097/00003086-197306000-00018 Chen J et al (2021) The radiographic, pulmonary, and clinical outcomes of patients with severe rigid spinal deformities treated via halo-pelvic traction. BMC Musculoskelet Disord 22(1):106. http://dx.doi.org/10.1186/s12891-021-03953-y Wang LH et al (2021) [Study on the safety and clinical efficacy of osteotomy after halo pelvic traction in severe scoliosis accompanied with split cord malformation]. Zhonghua Wai Ke Za Zhi, 59(5): pp. 370–377. http://dx.doi.org/10.3760/cma.j.cn112139-20200904-00686 Hsu LC (2014) Halo-pelvic traction: a means of correcting severe spinal deformities. Hong Kong Med J 20(4):358–359 Zhou L et al (2023) Evaluation of Pulmonary Function After Halo-Pelvic Traction for Severe and Rigid Kyphoscoliosis Utilizing CT with 3D Reconstruction. J Bone Joint Surg Am 105(22):1793–1800. http://dx.doi.org/10.2106/jbjs.23.00035 Sun Y et al (2023) Halo-pelvic traction in the treatment of severe scoliosis: a meta-analysis. Eur Spine J 32(3):874–882. http://dx.doi.org/10.1007/s00586-023-07525-7 Botelho RV et al (2000) Traumatic vertical atlantoaxial instability: the risk associated with skull traction. Case report and literature review. Eur Spine J 9(5):430–433. http://dx.doi.org/10.1007/s005860000166 Gonzalez LF et al (2004) Vertical atlantoaxial distraction injuries: radiological criteria and clinical implications. J Neurosurg Spine 1(3):273–280. http://dx.doi.org/10.3171/spi.2004.1.3.0273 Wang S et al (2013) Novel surgical classification and treatment strategy for atlantoaxial dislocations. Spine (Phila Pa 1976) 38(21). p. E1348-56.http://dx.doi.org/10.1097/BRS.0b013e3182a1e5e4 Greenberg AD (1968) Atlanto-axial dislocations. Brain 91(4):655–684. http://dx.doi.org/10.1093/brain/91.4.655 Wang Y et al (2021) Presurgical Short-Term Halo-Pelvic Traction for Severe Rigid Scoliosis (Cobb Angle > 120°): A 2-Year Follow-up Review of 62 Patients. Spine (Phila Pa 1976) 46(2):E95–e104. http://dx.doi.org/10.1097/brs.0000000000003740 Qi L et al (2020) Clinical efficacy of short-term pre-operative halo-pelvic traction in the treatment of severe spinal deformities complicated with respiratory dysfunction. BMC Musculoskelet Disord 21(1):665. http://dx.doi.org/10.1186/s12891-020-03700-9 Passias PG et al (2013) Relationship between the alignment of the occipitoaxial and subaxial cervical spine in patients with congenital atlantoxial dislocations. J Spinal Disord Tech 26(1):15–21. http://dx.doi.org/10.1097/BSD.0b013e31823097f9 Matsunaga S, Onishi T, Sakou T (2001) Significance of occipitoaxial angle in subaxial lesion after occipitocervical fusion. Spine (Phila Pa 1976) 26(2):161–165. http://dx.doi.org/10.1097/00007632-200101150-00010 Lacy J, Bajaj J, Gillis CC (2025) Atlantoaxial Instability , in StatPearls . StatPearls Publishing Copyright © 2025, StatPearls Publishing LLC.: Treasure Island (FL) ineligible companies. Disclosure: Jitin Bajaj declares no relevant financial relationships with ineligible companies. Disclosure: Christopher Gillis declares no relevant financial relationships with ineligible companies Dove J, Hsu LC, Yau AC (1980) The cervical spine after halo-pelvic traction. An analysis of the complications of 83 patients. J Bone Joint Surg Br 262–b. http://dx.doi.org/10.1302/0301-620x.62b2.7364826 Rahimi SY et al (2003) Treatment of atlantoaxial instability in pediatric patients. Neurosurg Focus 15(6). p. Ecp1.http://dx.doi.org/10.3171/foc.2003.15.6.7 Additional Declarations No competing interests reported. Cite Share Download PDF Status: Published Journal Publication published 25 Aug, 2025 Read the published version in European Spine Journal → Version 1 posted Editorial decision: Revision requested 31 Jul, 2025 Reviews received at journal 28 Jul, 2025 Reviews received at journal 27 Jul, 2025 Reviewers agreed at journal 15 Jul, 2025 Reviewers agreed at journal 13 Jul, 2025 Reviewers invited by journal 29 May, 2025 Editor assigned by journal 26 May, 2025 Submission checks completed at journal 26 May, 2025 First submitted to journal 25 May, 2025 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. Our growing team is made up of researchers and industry professionals working together to solve the most critical problems facing scientific publishing. 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-6744315","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":464682034,"identity":"1e16e531-8de0-4fb1-874e-c885b7ffc525","order_by":0,"name":"Lijin Zhou","email":"","orcid":"","institution":"Beijing Chao-Yang Hospital","correspondingAuthor":false,"prefix":"","firstName":"Lijin","middleName":"","lastName":"Zhou","suffix":""},{"id":464682035,"identity":"966070bd-9bb3-4678-9cde-3e5de7de67aa","order_by":1,"name":"Haoshuang Geng","email":"","orcid":"","institution":"Beijing Chao-Yang Hospital","correspondingAuthor":false,"prefix":"","firstName":"Haoshuang","middleName":"","lastName":"Geng","suffix":""},{"id":464682036,"identity":"2107f9d1-fdaf-4db0-8577-5fab6ed21963","order_by":2,"name":"Jianqiang Wang","email":"","orcid":"","institution":"Beijing Chao-Yang Hospital","correspondingAuthor":false,"prefix":"","firstName":"Jianqiang","middleName":"","lastName":"Wang","suffix":""},{"id":464682037,"identity":"bc1a9527-ae5e-4486-b0d4-7fb9167ee4cb","order_by":3,"name":"Yong Hai","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAA3klEQVRIiWNgGAWjYFACxgYE+4OBjR1pWhhnFKQlk2YhM8+HQ8iWYgfys5vbHnz4czhf3r352GMbgwPMDOyHj27Ap8XgzsF2w5lthy03njmWbpxjcIePgSct7QZeLRKJbdK8DYcNDGfkmEnnGDxjZpDgMcOrRX4GUMufP0At89+YSVsYHGZsIKSF4QZQCwPbYQN5oEppBmK0AP3SJtnblm5gAPSCZI9BWjIbIb/Iz25/JvHjj7WBfPvhY0CGjR0/++Fj+B0mAbPuAJTBhlc5shb5BoJKR8EoGAWjYKQCAEUJScmJdRnKAAAAAElFTkSuQmCC","orcid":"","institution":"Beijing Chao-Yang Hospital","correspondingAuthor":true,"prefix":"","firstName":"Yong","middleName":"","lastName":"Hai","suffix":""}],"badges":[],"createdAt":"2025-05-25 14:38:04","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-6744315/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-6744315/v1","draftVersion":[],"editorialEvents":[{"content":"https://doi.org/10.1007/s00586-025-09283-0","type":"published","date":"2025-08-25T15:57:44+00:00"}],"editorialNote":"","failedWorkflow":false,"files":[{"id":83839048,"identity":"30b3e9c7-c122-4183-9d9b-79518c5f6bbe","added_by":"auto","created_at":"2025-06-03 13:42:00","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":456515,"visible":true,"origin":"","legend":"\u003cp\u003eThis is a twenty-three-year-old female who underwent posterior spinal fusion after five months of halo-pelvic traction. a, b) Pre-traction clinical picture. c, d) Clinical picture after 5 months of traction. e, f) Clinical picture after posterior spinal surgery. g, h) Pre-traction X-ray. i, j) Post-traction X-ray. k, l) Postoperative X-ray.\u003c/p\u003e","description":"","filename":"Fig3.png","url":"https://assets-eu.researchsquare.com/files/rs-6744315/v1/75a264fc20099c725474b3c9.png"},{"id":83837717,"identity":"8cde4e6e-6e10-43bc-b516-354d6a2e4d7a","added_by":"auto","created_at":"2025-06-03 13:26:00","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":1433796,"visible":true,"origin":"","legend":"\u003cp\u003eRadiographic criterion for atlantoaxial traction intolerance\u003c/p\u003e","description":"","filename":"Figure.2.png","url":"https://assets-eu.researchsquare.com/files/rs-6744315/v1/99ae1e2e218765dae566cd0f.png"},{"id":83837725,"identity":"3115c13b-a46b-4eef-8731-4262729ef018","added_by":"auto","created_at":"2025-06-03 13:26:01","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":13699081,"visible":true,"origin":"","legend":"\u003cp\u003eCoronal CT image of the atlantoaxial region in a twenty-three-year-old female. The shortest perpendicular distance between the articular surfaces of the C1 and C2 lateral masses is defined as the LMI. a) Pre-traction coronal CT image. b) Post-traction coronal CT image. c) Postoperative coronal CT image.\u003c/p\u003e","description":"","filename":"Figure1.png","url":"https://assets-eu.researchsquare.com/files/rs-6744315/v1/1bf4941fc50c9f6366b6937e.png"},{"id":83837711,"identity":"f8a946ed-d749-4abf-8cc1-7eb116313d7f","added_by":"auto","created_at":"2025-06-03 13:26:00","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":16136,"visible":true,"origin":"","legend":"\u003cp\u003eROC curve for the predictive model of atlantoaxial subluxation during halo-pelvic traction\u003c/p\u003e","description":"","filename":"Figure4.png","url":"https://assets-eu.researchsquare.com/files/rs-6744315/v1/4791ee125af6e23c3fb4121f.png"},{"id":83838232,"identity":"c9d4915d-dbf0-4c2a-98c5-f0de61d39fc7","added_by":"auto","created_at":"2025-06-03 13:34:00","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":119922,"visible":true,"origin":"","legend":"\u003cp\u003eNomogram for predicting the risk of atlantoaxial subluxation during halo-pelvic traction\u003c/p\u003e","description":"","filename":"Figure5.png","url":"https://assets-eu.researchsquare.com/files/rs-6744315/v1/56b19362cd2f4ab89d56cab1.png"},{"id":90344879,"identity":"d518447c-76e5-4b5e-abbd-a9048c30ef2c","added_by":"auto","created_at":"2025-09-01 16:07:07","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":17012883,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-6744315/v1/6ecc3eb6-af26-44d0-8ab6-261db0cd05c2.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"Radiographic Assessment and Risk Model of Atlantoaxial Instability Induced by Halo-Pelvic Traction in Treating Severe Spinal Deformity","fulltext":[{"header":"Introduction","content":"\u003cp\u003eSevere and rigid spinal deformities were defined as a cobb angle greater than 100 degrees and flexibility less than 30% [\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e, \u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e]. Treating severe spinal deformities poses significant challenges. Although high-level osteotomy is a treatment option, it is associated with a steep learning curve and substantial blood loss; rapid correction of severe spinal deformities can also lead to spinal cord traction injuries[\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e, \u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e]. Halo-pelvic traction (HPT), first introduced by O\u0026rsquo;Brien et al. in 1973 for the treatment of scoliosis, comprises a halo ring, a pelvic ring, and adjustable connecting rods that enable gradual deformity correction over time [\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e, \u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e]. HPT can achieve 33\u0026ndash;45% correction of scoliosis and 49\u0026ndash;55% correction of kyphosis before the surgery and significantly enhance surgical safety [\u003cspan additionalcitationids=\"CR8\" citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e]. Additionally, HPT has been proven to safely and effectively improve pulmonary function in patients during traction [\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eHowever, HPT has some drawbacks, including neck stiffness, neurological symptoms, pin infections, skin infections, and atlantoaxial instable[\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e]. Vertical instability of the atlantoaxial joint is a clinically significant yet understudied spinal condition characterized by misalignment between the atlas (C1) and axis (C2) in the vertical plane. This pathological condition can result in severe complications, including severe neurological complications, and in extreme cases, death[\u003cspan additionalcitationids=\"CR13\" citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e]. During the process, HPT applies vertical forces to the patient. Because the atlantoaxial joint lacks the typical vertebral body structure, making the articular system primarily dependent on ligaments, it is relatively fragile and susceptible to dislocation during traction [\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eTherefore, this study aims to identify suitable methods for evaluating the atlantoaxial relationship during HPT, investigate the effects of HPT on the vertical distance between C1 and C2, and assess the safety of this procedure. Additionally, we aim to determine the risk factors contributing to atlantoaxial instability, develop a predictive model based on these factors, and provide a clinically applicable tool to assist in identifying patients at high risk of instability during halo-pelvic traction.\u003c/p\u003e"},{"header":"Materials and Methods","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e \u003ch2\u003ePatient cohort\u003c/h2\u003e \u003cp\u003eThis single-center retrospective cohort study was conducted from March 2014 to August 2022 at Beijing Chao-Yang Hospital. Fifty-nine patients with severe scoliosis who underwent preoperative HPT were retrospectively included. The inclusion criteria were as follows: 1) patients with severe kyphoscoliosis (a coronal cobb angle or kyphosis angle of \u0026gt;100\u0026ordm;); 2) patients who underwent HPT before the final fusion. The exclusion criteria were prior spinal surgery and inadequate visualization of the atlantoaxial joint structure on CT imaging. This study was approved by the Research Ethics Committee of Beijing Chao-Yang Hospital, and informed consent was obtained from patients.\u003c/p\u003e\n \u003c/div\u003e\n\u003ch3\u003eBaseline characteristics and neurological complications\u003c/h3\u003e\n\u003cp\u003eDemographic data included the patient\u0026rsquo;s sex, age, body mass index (BMI), type of scoliosis, duration of traction, and the position of the apex vertebra of the primary curve. The type of scoliosis was categorized as idiopathic scoliosis (IS), congenital scoliosis (CS), and neuromuscular scoliosis (NMS). The apex vertebra was classified in to thoracic group and lumbar group according to its location. In addition, neurological complications occurring during traction were recorded, including dysphagia, dysarthria, muscle weakness, paresthesia, and urinary or bowel dysfunction.\u003c/p\u003e\n\u003ch3\u003eRadiographic Parameters\u003c/h3\u003e\n\u003cp\u003eStanding full-length coronal and sagittal radiographs were collected before and after the HPT process, and the changes in the spinal parameters were assessed. Coronal plane measurements included: 1) cobb angle of the primary curve; 2) apical vertebral translation (AVT); 3) distance from the C7 plumb line to the sacral vertical line (C7PL-CSVL). Sagittal plane measurements included: 1) focal kyphosis (FK); 2) T5-T12 kyphosis (TK); 3) lumbar lordosis (LL); 4) pelvic tilt (PT); 5) sacral slope (SS); 6) T1 pelvic angle (TPA); 7) sagittal vertical axis (SVA).\u003c/p\u003e\n\u003ch3\u003eHPT protocols\u003c/h3\u003e\n\u003cp\u003eWith the patient under general anesthesia and in the lateral position, a 4.0 mm diameter pin was inserted through the skin at the thickest part of the ilium, midway between the anterior superior iliac spine and the posterior superior iliac spine on one side. The same procedure was then performed on the other side. After placing the patient in the supine position, ten halo pins were inserted at the maximum circumference of the skull anteriorly and laterally and connected to the halo ring. The connecting rods and pelvic ring were assembled three to five days later to allow the patient to adapt to the pins. Once the frame assembly was completed, traction was initiated, increasing gradually by 0.5 cm per day. The traction was discontinued when any of the following occurred: (1) the patient was unable to tolerate the traction, (2) the primary curve Cobb angle was reduced by more than 50%, (3) new neurological symptoms emerged, or (4) lateral cervical radiographs indicated that the patient exhibited atlantoaxial intolerance to traction. The criterion for determining intolerance to traction at the atlantoaxial joint was defined as the tip of the odontoid process contacting the anterior arch of the atlas at or below its lower one-third (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e) (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003c/p\u003e\n\u003ch3\u003eThe evaluation of vertical atlantoaxial subluxation\u003c/h3\u003e\n\u003cp\u003eFull-length spinal CT scans obtained before traction, after traction, and postoperatively were independently evaluated by two researchers. The shortest distance between the lateral masses of C-1 and C-2 was measured on planes perpendicular to the articular surfaces on the right and left sides, respectively, and defined as the Lateral Mass Interval (LMI). Three measurements were taken for each patient, and the average left and right LMI values were calculated. The normal values for the LMI range from 0.7mm to 2.6 mm, and an LMI greater than 2.6 mm on either side indicates instability in the atlantoaxial area [\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e] (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cdiv id=\"Sec8\" class=\"Section2\"\u003e \u003ch2\u003eStatistical Analysis\u003c/h2\u003e \u003cp\u003eAll statistical analyses were performed using IBM SPSS Statistics, version 29 (IBM Corporation, Armonk, NY, USA). The Shapiro\u0026ndash;Wilk test was conducted to assess the normality of continuous variables. Continuous variables with a normal distribution are presented as mean\u0026thinsp;\u0026plusmn;\u0026thinsp;standard deviation (SD), whereas non-normally distributed variables are expressed as median and interquartile range (IQR). Categorical variables are summarized as counts and percentages.\u003c/p\u003e \u003cp\u003ePatients were divided into two groups based on the presence of atlantoaxial subluxation. For continuous variables, comparisons between groups were performed using independent samples t-tests if normally distributed; otherwise, the Mann\u0026ndash;Whitney U test was applied. Categorical variables were compared using the chi-square test. Variables with a P value\u0026thinsp;\u0026lt;\u0026thinsp;0.1 in the univariate analysis were included in a multivariable logistic regression model to identify independent risk factors, using the backward: Wald method. A nomogram and a receiver operating characteristic (ROC) curve were generated based on the multivariate logistic regression model. In addition, patients were evaluated at three time points (pre-traction, post-traction, and postoperative). Comparisons were conducted using the least significant difference (LSD) test. A two-tailed P value\u0026thinsp;\u0026lt;\u0026thinsp;0.05 was considered statistically significant. We present this article in accordance with the STROBE reporting checklist\u003c/p\u003e \u003c/div\u003e"},{"header":"Results","content":"\u003cdiv id=\"Sec10\" class=\"Section2\"\u003e\n \u003ch2\u003eBaseline characteristics\u003c/h2\u003e\n \u003cp\u003eFifty-nine patients (21 males and 38 females) who underwent HPT were retrospectively recruited in this study. Atlantoaxial instability occurred in 45 patients, while 14 patients remained stable during halo-pelvic traction. The mean age at surgery was 26.15\u0026thinsp;\u0026plusmn;\u0026thinsp;9.66 years, and the mean BMI was 19.59\u0026thinsp;\u0026plusmn;\u0026thinsp;3.49. The average traction duration was 19.44\u0026thinsp;\u0026plusmn;\u0026thinsp;4.39 weeks. The etiological diagnoses were neuromuscular scoliosis (n\u0026thinsp;=\u0026thinsp;2), idiopathic scoliosis (n\u0026thinsp;=\u0026thinsp;16), and congenital scoliosis (n\u0026thinsp;=\u0026thinsp;41). During traction, one patient experienced dysphagia and dysarthria, three patients experienced upper limb muscle strength reduction; these symptoms resolved after surgery. No patients experienced paresthesia or urinary and bowel dysfunction. A significant age difference was observed between the unstable and stable groups (24.02 years\u0026thinsp;\u0026plusmn;\u0026thinsp;9.11 years vs. 33.00 years\u0026thinsp;\u0026plusmn;\u0026thinsp;8.31 years, P\u0026thinsp;=\u0026thinsp;0.002). There were no significant differences between sex, BMI, type of scoliosis, duration of traction, and the apex vertebra position (Table \u003cspan class=\"InternalRef\"\u003e1\u003c/span\u003e).\u003c/p\u003e\n \u003cp\u003e\u003cbr\u003e\u003c/p\u003e\u0026nbsp;\u003ctable id=\"Tab1\" border=\"1\"\u003e\n \u003ccaption language=\"En\"\u003e\n \u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e\n \u003cdiv class=\"CaptionContent\"\u003e\n \u003cp\u003eComparison of baseline data between Stable and Unstable atlantoaxial groups during traction\u003c/p\u003e\n \u003c/div\u003e\n \u003c/caption\u003e\n \u003cthead\u003e\n \u003ctr\u003e\n \u003cth align=\"left\"\u003e\u0026nbsp;\u003c/th\u003e\n \u003cth align=\"left\" colspan=\"6\"\u003e\n \u003cp\u003eStable (n\u0026thinsp;=\u0026thinsp;14)\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\" colspan=\"4\"\u003e\n \u003cp\u003eUnstable (n\u0026thinsp;=\u0026thinsp;45)\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eP Value\u003c/p\u003e\n \u003c/th\u003e\n \u003c/tr\u003e\n \u003c/thead\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eAge (years)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e33.00\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colspan=\"3\"\u003e\n \u003cp\u003e\u0026plusmn;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colspan=\"2\"\u003e\n \u003cp\u003e8.31\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colspan=\"2\"\u003e\n \u003cp\u003e24.02\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u0026plusmn;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e9.11\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003e0.002\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eGender\u003c/p\u003e\n \u003cp\u003eMale\u003c/p\u003e\n \u003cp\u003eFemale\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colspan=\"6\"\u003e\n \u003cp\u003e\u003cbr\u003e\u003c/p\u003e\n \u003cp\u003e6 (42.9%)\u003c/p\u003e\n \u003cp\u003e8 (57.1%)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colspan=\"4\"\u003e\n \u003cp\u003e\u003cbr\u003e\u003c/p\u003e\n \u003cp\u003e15 (33.3%)\u003c/p\u003e\n \u003cp\u003e30 (66.7%)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cbr\u003e\u003c/p\u003e\n \u003cp\u003e0.538\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eBody mass index (BMI)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colspan=\"2\"\u003e\n \u003cp\u003e20.27\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u0026plusmn;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colspan=\"3\"\u003e\n \u003cp\u003e3.25\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colspan=\"2\"\u003e\n \u003cp\u003e19.38\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u0026plusmn;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e3.57\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.407\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eType of scoliosis\u003c/p\u003e\n \u003cp\u003eNMS\u003c/p\u003e\n \u003cp\u003eIS\u003c/p\u003e\n \u003cp\u003eCS\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colspan=\"6\"\u003e\n \u003cp\u003e\u003cbr\u003e\u003c/p\u003e\n \u003cp\u003e1 (7.1%)\u003c/p\u003e\n \u003cp\u003e2 (14.3%)\u003c/p\u003e\n \u003cp\u003e11 (78.6%)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colspan=\"4\"\u003e\n \u003cp\u003e\u003cbr\u003e\u003c/p\u003e\n \u003cp\u003e1 (2.2%)\u003c/p\u003e\n \u003cp\u003e14 (31.1%)\u003c/p\u003e\n \u003cp\u003e30 (66.7%)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cbr\u003e\u003c/p\u003e\n \u003cp\u003e\u003cbr\u003e\u003c/p\u003e\n \u003cp\u003e0.345\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eDuration of traction (weeks)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colspan=\"2\"\u003e\n \u003cp\u003e19.79\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colspan=\"3\"\u003e\n \u003cp\u003e\u0026plusmn;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e3.47\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e19.33\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colspan=\"2\"\u003e\n \u003cp\u003e\u0026plusmn;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e4.67\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.740\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eApex vertebra position\u003c/p\u003e\n \u003cp\u003eT\u003c/p\u003e\n \u003cp\u003eL\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colspan=\"6\"\u003e\n \u003cp\u003e\u003cbr\u003e\u003c/p\u003e\n \u003cp\u003e9 (64.3%)\u003c/p\u003e\n \u003cp\u003e5 (35.7%)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colspan=\"4\"\u003e\n \u003cp\u003e\u003cbr\u003e\u003c/p\u003e\n \u003cp\u003e38 (86.4%)\u003c/p\u003e\n \u003cp\u003e6 (13.6%)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cbr\u003e\u003c/p\u003e\n \u003cp\u003e0.112\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\" colspan=\"12\"\u003e\n \u003cp\u003e\u003cem\u003eNMS indicates neuromuscular scoliosis; AIS, idiopathic scoliosis; CS, congenital scoliosis; T, thoracic; L, lumbar\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n \u003c/table\u003e\n \u003cp\u003e\u003cbr\u003e\u003c/p\u003e\n \u003cp\u003e\u003cbr\u003e\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec11\" class=\"Section2\"\u003e\n \u003ch2\u003eRadiographic parameters\u003c/h2\u003e\n \u003cp\u003eThe FK (118.44\u0026ordm; \u0026plusmn; 32.71\u0026ordm; vs. 99.94\u0026ordm; \u0026plusmn; 33.83\u0026ordm;, P\u0026thinsp;=\u0026thinsp;0.077), AVT (106.40mm\u0026thinsp;\u0026plusmn;\u0026thinsp;35.88mm vs. 84.67mm\u0026thinsp;\u0026plusmn;\u0026thinsp;35.82mm, P\u0026thinsp;=\u0026thinsp;0.050) and C7PL-CSVL (41.33mm\u0026thinsp;\u0026plusmn;\u0026thinsp;35.18mm vs. 22.81mm\u0026thinsp;\u0026plusmn;\u0026thinsp;21.32mm, P\u0026thinsp;=\u0026thinsp;0.019) in the stable group were significantly higher than in the unstable group. Additionally, the PT (7.19\u0026deg; \u0026plusmn; 5.86\u0026deg; vs. 11.75\u0026deg; \u0026plusmn; 7.67\u0026deg;, P\u0026thinsp;=\u0026thinsp;0.046) in the stable group was significantly lower than in the unstable group. The groups had no significant differences in other radiographic parameters (Table \u003cspan class=\"InternalRef\"\u003e2\u003c/span\u003e).\u003c/p\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003ctable id=\"Tab2\" border=\"1\"\u003e\n \u003ccaption language=\"En\"\u003e\n \u003cdiv class=\"CaptionNumber\"\u003eTable 2\u003c/div\u003e\n \u003cdiv class=\"CaptionContent\"\u003e\n \u003cp\u003eComparison of radiographic parameters between Stable and Unstable atlantoaxial groups during traction\u003c/p\u003e\n \u003c/div\u003e\n \u003c/caption\u003e\n \u003cthead\u003e\n \u003ctr\u003e\n \u003cth align=\"left\"\u003e\u0026nbsp;\u003c/th\u003e\n \u003cth align=\"left\" colspan=\"3\"\u003e\n \u003cp\u003eStable\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\" colspan=\"3\"\u003e\n \u003cp\u003eUnstable\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eP Value\u003c/p\u003e\n \u003c/th\u003e\n \u003c/tr\u003e\n \u003c/thead\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eMain Cobb angle (\u0026ordm;)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e129.74\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u0026plusmn;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e22.92\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e116.44\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u0026plusmn;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e41.65\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.260\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eFK (\u0026ordm;)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e118.44\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u0026plusmn;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e32.71\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e99.94\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u0026plusmn;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e33.83\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003e0.077\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eTK (\u0026ordm;)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e93.01\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u0026plusmn;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e31.21\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e85.19\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u0026plusmn;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e32.01\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.425\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eLL (\u0026ordm;)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e71.34\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u0026plusmn;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e23.66\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e63.70\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u0026plusmn;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e21.58\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.263\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003ePT (\u0026ordm;)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e7.19\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u0026plusmn;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e5.86\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e11.75\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u0026plusmn;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e7.67\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003e0.046\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eSS (\u0026ordm;)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e28.49\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u0026plusmn;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e8.75\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e24.75\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u0026plusmn;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e9.45\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.194\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eTPA (\u0026ordm;)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e5.65\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u0026plusmn;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e3.89\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e8.15\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u0026plusmn;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e5.81\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.138\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eSVA (mm)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e20.22\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u0026plusmn;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e23.43\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e15.17\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u0026plusmn;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e22.20\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.467\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eAVT (mm)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e106.40\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u0026plusmn;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e35.88\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e84.67\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u0026plusmn;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e35.82\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003e0.050\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eC7PL-CSVL (mm)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e41.33\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u0026plusmn;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e35.18\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e22.81\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u0026plusmn;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e21.32\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003e0.019\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eCobb correction rate (%)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e48.19\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u0026plusmn;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e19.39\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e53.19\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u0026plusmn;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e13.59\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.284\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eMK correction rate (%)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e41.66\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u0026plusmn;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e18.05\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e51.23\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u0026plusmn;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e21.58\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.139\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\" colspan=\"8\"\u003e\n \u003cp\u003e\u003cem\u003eFK indicates focal kyphosis; TK, thoracic kyphosis; LL, lumbar lordosis; PT, pelvic tilt; SS, sacral slope; TPA, T1 pelvic angle; SVA, sagittal vertical axis; AVT, apical vertebral translation; C7PL, C7 plumb line; CSVL, center sacral vertical line\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n \u003c/table\u003e\n \u003cp\u003e\u003c/p\u003e\n \u003cp\u003e\u003cbr\u003e\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec12\" class=\"Section2\"\u003e\n \u003ch2\u003eMultivariate Logistic regression\u003c/h2\u003e\n \u003cp\u003eMultivariate logistic regression found that younger age and increased PT were associated with a higher risk of instability (OR\u0026thinsp;=\u0026thinsp;0.893, 95% CI: 0.826\u0026ndash;0.966, P\u0026thinsp;=\u0026thinsp;0.005), (OR\u0026thinsp;=\u0026thinsp;1.137, 95% CI: 1.001\u0026ndash;1.292, P\u0026thinsp;=\u0026thinsp;0.048). The Hosmer\u0026ndash;Lemeshow goodness-of-fit test indicated an adequate model fit (P\u0026thinsp;=\u0026thinsp;0.653). ROC curve analysis demonstrated that the model had good discriminatory ability, with an AUC of 0.817 (95% CI: 0.689\u0026ndash;0.946). The optimal cutoff value, determined by Youden\u0026rsquo;s index (0.633), corresponded to a sensitivity of 0.889 and a specificity of 0.286 (Fig. \u003cspan class=\"InternalRef\"\u003e4\u003c/span\u003e). A nomogram was constructed based on the multivariable logistic regression model (Fig. \u003cspan class=\"InternalRef\"\u003e5\u003c/span\u003e).\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec13\" class=\"Section2\"\u003e\n \u003ch2\u003eVertical atlantoaxial instable\u003c/h2\u003e\n \u003cp\u003eBefore traction, none of the patients had atlantoaxial instability. However, it developed in 45 patients during traction. Both right and left LMIs significantly increased from pre-traction to post-traction (right: 1.52\u0026thinsp;\u0026plusmn;\u0026thinsp;0.46 mm vs. 4.03\u0026thinsp;\u0026plusmn;\u0026thinsp;2.47 mm, P\u0026thinsp;\u0026lt;\u0026thinsp;0.001; left: 1.43\u0026thinsp;\u0026plusmn;\u0026thinsp;0.42 mm vs. 3.94\u0026thinsp;\u0026plusmn;\u0026thinsp;2.16 mm, P\u0026thinsp;\u0026lt;\u0026thinsp;0.001). After surgery, both right and left LMIs significantly decreased compared to post-traction values (right: 4.03\u0026thinsp;\u0026plusmn;\u0026thinsp;2.47 mm vs. 1.41\u0026thinsp;\u0026plusmn;\u0026thinsp;0.40 mm, P\u0026thinsp;\u0026lt;\u0026thinsp;0.001; left: 3.94\u0026thinsp;\u0026plusmn;\u0026thinsp;2.16 mm vs. 1.32\u0026thinsp;\u0026plusmn;\u0026thinsp;0.50 mm, P\u0026thinsp;\u0026lt;\u0026thinsp;0.001). There was no significant difference in either right or left LMIs between pre-traction and postoperative measurements (right: 1.52\u0026thinsp;\u0026plusmn;\u0026thinsp;0.46 mm vs. 1.41\u0026thinsp;\u0026plusmn;\u0026thinsp;0.40 mm, P\u0026thinsp;=\u0026thinsp;0.108; left: 1.43\u0026thinsp;\u0026plusmn;\u0026thinsp;0.42 mm vs. 1.32\u0026thinsp;\u0026plusmn;\u0026thinsp;0.50 mm, P\u0026thinsp;=\u0026thinsp;0.069) (Table \u003cspan class=\"InternalRef\"\u003e3\u003c/span\u003e).\u0026nbsp;\u003c/p\u003e\n \u003cdiv class=\"gridtable\"\u003e\n \u003ctable id=\"Tab3\" border=\"1\"\u003e\n \u003ccaption language=\"En\"\u003e\n \u003cdiv class=\"CaptionNumber\"\u003eTable 3\u003c/div\u003e\n \u003cdiv class=\"CaptionContent\"\u003e\n \u003cp\u003eComparison of right LMI and left LMI pre-traction, post-traction, and postoperative\u003c/p\u003e\n \u003c/div\u003e\n \u003c/caption\u003e\n \u003cthead\u003e\n \u003ctr\u003e\n \u003cth align=\"left\"\u003e\u0026nbsp;\u003c/th\u003e\n \u003cth align=\"left\" colspan=\"3\"\u003e\u0026nbsp;\u003c/th\u003e\n \u003cth align=\"left\" colspan=\"3\"\u003e\u0026nbsp;\u003c/th\u003e\n \u003cth align=\"left\" colspan=\"3\"\u003e\u0026nbsp;\u003c/th\u003e\n \u003cth align=\"left\" colspan=\"3\"\u003e\n \u003cp\u003eP Value\u003c/p\u003e\n \u003c/th\u003e\n \u003c/tr\u003e\n \u003c/thead\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003ctd align=\"left\" colspan=\"3\"\u003e\n \u003cp\u003ePre-traction\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colspan=\"3\"\u003e\n \u003cp\u003ePost-traction\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colspan=\"3\"\u003e\n \u003cp\u003ePostoperative\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003ePre-traction vs. Post-traction\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003ePost-traction vs. Postoperative\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003ePostoperative vs. Pre-traction\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eRight LMI (mm)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e1.52\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u0026plusmn;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.46\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e4.03\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u0026plusmn;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e2.47\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e1.41\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u0026plusmn;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.40\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u0026lt;\u0026thinsp;0.001\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u0026lt;\u0026thinsp;0.001\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.108\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eLeft LMI (mm)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e1.43\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u0026plusmn;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.42\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e3.94\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u0026plusmn;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e2.16\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e1.32\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u0026plusmn;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.50\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u0026lt;\u0026thinsp;0.001\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u0026lt;\u0026thinsp;0.001\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.069\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n \u003c/table\u003e\n \u003c/div\u003e\n \u003cp\u003e\u003cbr\u003e\u003c/p\u003e\n\u003c/div\u003e"},{"header":"Discussion","content":"\u003cp\u003eAtlantoaxial instability is one of the major complications associated with HPT; however, limited studies have specifically addressed this issue [\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e, \u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e, \u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e]. To our knowledge, this is the first study to evaluate atlantoaxial instability during halo-pelvic traction. Based on the exaggerated movements in different directions affecting the C1-C2 joint, atlantoaxial instability can be classified into vertical, anteroposterior, and rotational types [\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e, \u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e]. Given the structure design of the HPT frame, which exerts a predominantly vertical force relative to the transverse plane of the body, the instability observed during traction is primarily of the vertical type.\u003c/p\u003e \u003cp\u003eThe clinical manifestations of atlantoaxial instability vary widely; initial symptoms may include mild axial neck pain and paresthesia. Although uncommon, severe spinal cord injury during traction may lead to fatal outcomes [\u003cspan additionalcitationids=\"CR19\" citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e–\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e]. According to Gonzalez et al. [\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e], an LMI greater than 2.6 mm on either side between C1 and C2 suggests instability of the atlantoaxial joint. Our study found that forty-five patients undergoing HPT in our hospital experienced atlantoaxial instability during the traction period. However, postoperative LMI showed that the patient's atlantoaxial joint had returned to its normal anatomical position, with no significant differences on either side compared to before the traction (1.41mm ± 0.40mm vs. 1.52mm ± 0.46mm, P = 0.108); (1.32mm ± 0.50mm vs. 1.43mm ± 0.42mm, P = 0.069). During the traction process, one patient experienced dysphagia and dysarthria, three patients experienced upper limb muscle strength reduction. The symptoms resolved after the final fusion surgery was performed. Wang et al. [\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e], in a study of sixty-two patients undergoing HPT, found that only one patient experienced atlantoaxial instablity, which completely resolved in subsequent follow-ups, and no patients suffered permanent neurological deflect. Similarly, Qi et al. [\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e], in treating thirty patients with severe spinal deformities using halo-pelvic rings, found that patients who experienced neck discomfort during the traction process all had their symptoms resolved after surgery. Dove et al. [\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e] followed up with eighty-three patients who underwent halo-pelvic traction and found that only one patient developed atlantoaxial instability six years after the procedure. Previous studies on HPT have lacked standardized criteria for defining atlantoaxial instability. As a result, existing literature may have reported only cases of severe dislocation, potentially overlooking subtle or partial forms. Our study is the first to propose a quantitative definition of atlantoaxial subluxation based on lateral mass interval (LMI), thereby providing a more sensitive and objective framework for assessing C1–C2 instability during traction.\u003c/p\u003e \u003cp\u003eOur study found that younger age is an independent risk factor associated with atlantoaxial instability (OR = 0.893, 95% CI: 0.826–0.966, P = 0.005), which may be attributed to the higher ligamentous laxity, incomplete skeletal and joint development, and reduced muscular stability in younger individuals. Additionally, patients with atlantoaxial instability during HPT exhibited significantly higher PT compared to the stable group. Multivariable logistic regression confirmed that increased PT was an independent risk factor for atlantoaxial subluxation (OR = 1.137, 95% CI: 1.001–1.292, P = 0.048). An increased PT reflects sagittal imbalance, typically indicating compensatory posterior pelvic rotation to maintain upright posture. During halo-pelvic traction, a higher PT may serve as an indicator of sagittal malalignment. Our findings suggest that such sagittal imbalance is associated with a higher risk of atlantoaxial instability during traction. A predictive model incorporating patients’ PT and age demonstrated good discriminative ability, with an AUC of 0.817. This result indicates that the combination of these two variables provides a reliable and clinically meaningful prediction of atlantoaxial instability, supporting the potential utility of these parameters in pre-traction risk assessment.\u003c/p\u003e \u003cp\u003eThe key factor in treating vertical atlantoaxial instability is to protect the stability of the cervical spine [\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e]. The HPT frame does precisely this, ensuring stability by limiting cervical spine movement—a factor typically seen as a disadvantage. Interestingly, this restriction protects the cervical spine when instability occurs due to traction. Research indicates that using a rigid cervical collar or halo fixation is a reliable method for treating atlantoaxial instability without fractures [\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e, \u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e]. Moreover, because the HPT pulls vertically by only 0.5 cm per day and the entire traction process lasts for several months, the force and distance of traction on the patient gradually increase, allowing sufficient time to adapt to the traction. Patients who underwent HPT in our hospital had their atlantoaxial joints return to regular anatomical positions after removing the traction frame, proving that HPT does not cause irreversible damage to the critical ligaments and joints that maintain atlantoaxial stability. In our study, no patients experienced permanent neurological damage or death due to atlantoaxial instability.\u003c/p\u003e "},{"header":"Limitations","content":"\u003cp\u003eThere are several limitations in this study. First, the small sample size may limit the statistical power of the study, and larger cohorts are needed to validate the findings. Second, as a single-center retrospective study, there is a risk of selection bias and unmeasured confounding factors.\u003c/p\u003e\u003cp\u003eThird, the absence of cervical MRI data during traction and after surgery prevents direct evaluation of the atlantoaxial ligamentous structures. Fourth, long-term follow-up is required to assess the stability and progression of the atlantoaxial joint over time.\u003c/p\u003e"},{"header":"Conclusions","content":"\u003cp\u003eThis article utilized the method of measuring the LMI on CT scans to assess atlantoaxial instability and found that after removing the halo-pelvic frame, patients' atlantoaxial joint space could return to pre-traction level. Multivariable logistic regression analysis identified younger age and increased PT as independent risk factors for atlantoaxial instability during HPT. Based on these variables, we constructed a nomogram to support clinical decision-making. This tool may help identify high-risk patients before traction, enabling timely preventive strategies and improved safety during preoperative management.\u003c/p\u003e"},{"header":"Declarations","content":"\u003ch2\u003eAuthor Contribution\u003c/h2\u003e\u003cp\u003eL.Z contributed to the study design and conceptualization.H.G and J.W were responsible for data collection and radiographic assessment.Statistical analysis was conducted by H.G.The first draft of the manuscript was written by H.G, and all authors contributed to reviewing and editing the manuscript.Y.H supervised the project design and overall study process, and approved the final version of the manuscript.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eChang KW (2003) Cantilever bending technique for treatment of large and rigid scoliosis. Spine (Phila Pa 1976) 28(21):2452\u0026ndash;2458. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttp://dx.doi.org/10.1097/01.Brs.0000092063.63315.D5\u003c/span\u003e\u003cspan address=\"10.1097/01.Brs.0000092063.63315.D5\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eKandwal P et al (2017) Severe Rigid Scoliosis: Review of Management Strategies and Role of Spinal Osteotomies. Asian Spine J 11(3):494\u0026ndash;503. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttp://dx.doi.org/10.4184/asj.2017.11.3.494\u003c/span\u003e\u003cspan address=\"10.4184/asj.2017.11.3.494\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eXia L et al (2015) Spinal osteotomy techniques in management of severe pediatric spinal deformity and analysis of postoperative complications. Spine (Phila Pa 1976) 40(5):E286. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003e92.http://dx.doi.org/10.1097/brs.0000000000000728\u003c/span\u003e\u003cspan address=\"92.10.1097/brs.0000000000000728\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eAydinli U et al (2018) Results of Posterior Vertebral Column Resection: Surgical Modification of Suk Technique. Global Spine J 8(5):478\u0026ndash;482. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttp://dx.doi.org/10.1177/2192568217739854\u003c/span\u003e\u003cspan address=\"10.1177/2192568217739854\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eYang C et al (2017) Halo-gravity traction in the treatment of severe spinal deformity: a systematic review and meta-analysis. Eur Spine J 26(7):1810\u0026ndash;1816. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttp://dx.doi.org/10.1007/s00586-016-4848-y\u003c/span\u003e\u003cspan address=\"10.1007/s00586-016-4848-y\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eO'Brien JP, Yau AC, Hodgson AR (1973) Halo pelvic traction: a technic for severe spinal deformities. Clin Orthop Relat Res 93179\u0026ndash;190. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttp://dx.doi.org/10.1097/00003086-197306000-00018\u003c/span\u003e\u003cspan address=\"10.1097/00003086-197306000-00018\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eChen J et al (2021) The radiographic, pulmonary, and clinical outcomes of patients with severe rigid spinal deformities treated via halo-pelvic traction. BMC Musculoskelet Disord 22(1):106. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttp://dx.doi.org/10.1186/s12891-021-03953-y\u003c/span\u003e\u003cspan address=\"10.1186/s12891-021-03953-y\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eWang LH et al (2021) \u003cem\u003e[Study on the safety and clinical efficacy of osteotomy after halo pelvic traction in severe scoliosis accompanied with split cord malformation].\u003c/em\u003e Zhonghua Wai Ke Za Zhi, 59(5): pp. 370\u0026ndash;377.\u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttp://dx.doi.org/10.3760/cma.j.cn112139-20200904-00686\u003c/span\u003e\u003cspan address=\"10.3760/cma.j.cn112139-20200904-00686\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eHsu LC (2014) Halo-pelvic traction: a means of correcting severe spinal deformities. Hong Kong Med J 20(4):358\u0026ndash;359\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eZhou L et al (2023) Evaluation of Pulmonary Function After Halo-Pelvic Traction for Severe and Rigid Kyphoscoliosis Utilizing CT with 3D Reconstruction. J Bone Joint Surg Am 105(22):1793\u0026ndash;1800. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttp://dx.doi.org/10.2106/jbjs.23.00035\u003c/span\u003e\u003cspan address=\"10.2106/jbjs.23.00035\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eSun Y et al (2023) Halo-pelvic traction in the treatment of severe scoliosis: a meta-analysis. Eur Spine J 32(3):874\u0026ndash;882. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttp://dx.doi.org/10.1007/s00586-023-07525-7\u003c/span\u003e\u003cspan address=\"10.1007/s00586-023-07525-7\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eBotelho RV et al (2000) Traumatic vertical atlantoaxial instability: the risk associated with skull traction. Case report and literature review. Eur Spine J 9(5):430\u0026ndash;433. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttp://dx.doi.org/10.1007/s005860000166\u003c/span\u003e\u003cspan address=\"10.1007/s005860000166\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eGonzalez LF et al (2004) Vertical atlantoaxial distraction injuries: radiological criteria and clinical implications. J Neurosurg Spine 1(3):273\u0026ndash;280. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttp://dx.doi.org/10.3171/spi.2004.1.3.0273\u003c/span\u003e\u003cspan address=\"10.3171/spi.2004.1.3.0273\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eWang S et al (2013) Novel surgical classification and treatment strategy for atlantoaxial dislocations. Spine (Phila Pa 1976) 38(21). \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ep. E1348-56.http://dx.doi.org/10.1097/BRS.0b013e3182a1e5e4\u003c/span\u003e\u003cspan address=\"p. E1348-56.10.1097/BRS.0b013e3182a1e5e4\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eGreenberg AD (1968) Atlanto-axial dislocations. Brain 91(4):655\u0026ndash;684. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttp://dx.doi.org/10.1093/brain/91.4.655\u003c/span\u003e\u003cspan address=\"10.1093/brain/91.4.655\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eWang Y et al (2021) Presurgical Short-Term Halo-Pelvic Traction for Severe Rigid Scoliosis (Cobb Angle\u0026thinsp;\u0026gt;\u0026thinsp;120\u0026deg;): A 2-Year Follow-up Review of 62 Patients. Spine (Phila Pa 1976) 46(2):E95\u0026ndash;e104. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttp://dx.doi.org/10.1097/brs.0000000000003740\u003c/span\u003e\u003cspan address=\"10.1097/brs.0000000000003740\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eQi L et al (2020) Clinical efficacy of short-term pre-operative halo-pelvic traction in the treatment of severe spinal deformities complicated with respiratory dysfunction. BMC Musculoskelet Disord 21(1):665. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttp://dx.doi.org/10.1186/s12891-020-03700-9\u003c/span\u003e\u003cspan address=\"10.1186/s12891-020-03700-9\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003ePassias PG et al (2013) Relationship between the alignment of the occipitoaxial and subaxial cervical spine in patients with congenital atlantoxial dislocations. J Spinal Disord Tech 26(1):15\u0026ndash;21. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttp://dx.doi.org/10.1097/BSD.0b013e31823097f9\u003c/span\u003e\u003cspan address=\"10.1097/BSD.0b013e31823097f9\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eMatsunaga S, Onishi T, Sakou T (2001) Significance of occipitoaxial angle in subaxial lesion after occipitocervical fusion. Spine (Phila Pa 1976) 26(2):161\u0026ndash;165. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttp://dx.doi.org/10.1097/00007632-200101150-00010\u003c/span\u003e\u003cspan address=\"10.1097/00007632-200101150-00010\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eLacy J, Bajaj J, Gillis CC (2025) \u003cem\u003eAtlantoaxial Instability\u003c/em\u003e, in \u003cem\u003eStatPearls\u003c/em\u003e. StatPearls Publishing Copyright \u0026copy; 2025, StatPearls Publishing LLC.: Treasure Island (FL) ineligible companies. Disclosure: Jitin Bajaj declares no relevant financial relationships with ineligible companies. Disclosure: Christopher Gillis declares no relevant financial relationships with ineligible companies\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eDove J, Hsu LC, Yau AC (1980) The cervical spine after halo-pelvic traction. An analysis of the complications of 83 patients. J Bone Joint Surg Br 262\u0026ndash;b. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttp://dx.doi.org/10.1302/0301-620x.62b2.7364826\u003c/span\u003e\u003cspan address=\"10.1302/0301-620x.62b2.7364826\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eRahimi SY et al (2003) Treatment of atlantoaxial instability in pediatric patients. Neurosurg Focus 15(6). \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ep. Ecp1.http://dx.doi.org/10.3171/foc.2003.15.6.7\u003c/span\u003e\u003cspan address=\"p. Ecp1.10.3171/foc.2003.15.6.7\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":true,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"european-spine-journal","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"esjo","sideBox":"Learn more about [European Spine Journal](http://link.springer.com/journal/586)","snPcode":"586","submissionUrl":"https://submission.springernature.com/new-submission/586/3","title":"European Spine Journal","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"stoa","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false},"keywords":"","lastPublishedDoi":"10.21203/rs.3.rs-6744315/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-6744315/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003e\u003cstrong\u003ePURPOSE:\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eHalo-pelvic traction (HPT) is widely used for managing severe rigid scoliosis by enhancing surgical safety. However, complications such as atlantoaxial instability may occur during traction. This study aimed to identify the risk factors for atlantoaxial instability during HPT and assess whether instability is reversible after traction. Additionally, a radiographic criterion based on the lateral mass interval (LMI) was proposed to define this condition.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eMETHODS:\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eA retrospective study was conducted on patients who underwent HPT followed by posterior spinal fusion between March 2014 and August 2022. Atlantoaxial alignment was assessed pre-traction, post-traction, and postoperatively using LMI. Patients were categorized into stable and unstable groups. Risk factors were identified through univariate and multivariable logistic regression analyses, and a nomogram was constructed based on the final predictive model.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eRESULTS:\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eAmong fifty-nine patients, forty-five developed atlantoaxial instability during traction. All cases were radiographically reversible postoperatively. Multivariable analysis identified younger age (OR = 0.893, P = 0.005) and increased pelvic tilt (PT) (OR = 1.137, P = 0.048) as independent risk factors. The predictive model showed good discrimination (AUC = 0.817).\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eCONCLUSION:\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eAtlantoaxial instability during HPT is transient and reversible. LMI is a reliable radiographic indicator for its assessment. Younger age and increased PT are significant predictors, and the proposed nomogram may aid in pre-traction risk stratification.\u003c/p\u003e","manuscriptTitle":"Radiographic Assessment and Risk Model of Atlantoaxial Instability Induced by Halo-Pelvic Traction in Treating Severe Spinal Deformity","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-06-03 13:25:56","doi":"10.21203/rs.3.rs-6744315/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"decision","content":"Revision requested","date":"2025-07-31T13:57:18+00:00","index":"","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-07-28T19:43:52+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-07-27T21:58:28+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"214267509953380833652254077571154387910","date":"2025-07-15T17:07:17+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"236820624604056817933127555094442835556","date":"2025-07-13T22:39:26+00:00","index":"hide","fulltext":""},{"type":"reviewersInvited","content":"","date":"2025-05-30T02:06:07+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2025-05-26T11:06:04+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2025-05-26T11:01:59+00:00","index":"","fulltext":""},{"type":"submitted","content":"European Spine Journal","date":"2025-05-25T14:23:00+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"european-spine-journal","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"esjo","sideBox":"Learn more about [European Spine Journal](http://link.springer.com/journal/586)","snPcode":"586","submissionUrl":"https://submission.springernature.com/new-submission/586/3","title":"European Spine Journal","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"stoa","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false}}],"origin":"","ownerIdentity":"ed3bde61-f6a0-4f13-bd8e-4fc9d9b328f4","owner":[],"postedDate":"June 3rd, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"published-in-journal","subjectAreas":[],"tags":[],"updatedAt":"2025-09-01T16:01:39+00:00","versionOfRecord":{"articleIdentity":"rs-6744315","link":"https://doi.org/10.1007/s00586-025-09283-0","journal":{"identity":"european-spine-journal","isVorOnly":false,"title":"European Spine Journal"},"publishedOn":"2025-08-25 15:57:44","publishedOnDateReadable":"August 25th, 2025"},"versionCreatedAt":"2025-06-03 13:25:56","video":"","vorDoi":"10.1007/s00586-025-09283-0","vorDoiUrl":"https://doi.org/10.1007/s00586-025-09283-0","workflowStages":[]},"version":"v1","identity":"rs-6744315","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-6744315","identity":"rs-6744315","version":["v1"]},"buildId":"XKTyCvWXoU3ODBz1xrDgd","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}