Study of the Correlation between Adjacent Segment Disease and Segmental Lordosis After Lumbar Facet Joint Fusion Surgery

Study of the Correlation between Adjacent Segment Disease and Segmental Lordosis After Lumbar Facet Joint Fusion Surgery | 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 Study of the Correlation between Adjacent Segment Disease and Segmental Lordosis After Lumbar Facet Joint Fusion Surgery Haibiao Qin, Jinglong Yan, Guangxi Wang, Hui Chi, Xu Zhang, Pengyu Kong, and 1 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-6201144/v1 This work is licensed under a CC BY 4.0 License Status: Posted Version 1 posted You are reading this latest preprint version Abstract Objective Segmental lordosis is an important risk factor for spinal diseases. The purpose of this study was to investigate the relationships between segmental lordosis-related parameters and adjacent segment disease (ASD) after lumbar interarticular fusion. Methods This was a retrospective analysis of 27 patients with ASDs who underwent revision surgery in our hospital after lumbar interarticular fusion from February 2012 to February 2025. We included these 27 patients with ASD and matched them with 27 non-ASD controls on the basis of the initial surgery age, sex, surgical segment, and follow-up duration. Preoperative, postoperative, and final follow-up lumbar spine radiographs (anteroposterior and lateral radiographs) were analyzed. Parameters, including lumbar lordosis (LL), segmental lordosis (SL), sacral slope (SS), and the relative height of the intervertebral space adjacent to the fusion segment, were compared. Preoperative data, radiographic parameters at 3 days postsurgery, and final follow-up data were compared between the two groups. Significant parameters were further analyzed via multivariate logistic regression. The optimal predictive threshold for ASD was determined via receiver operating characteristic (ROC) curve analysis. Results No significant differences in the general demographic data were found between the two groups ( P > 0.05). Compared with the control group, the ASD group presented significantly lower postoperative lumbar LL, SS, and intervertebral space height ( P < 0.05), along with a significantly reduced relative change in segmental lordosis (r△SL) during the early postoperative period ( P < 0.05). Multivariate regression analysis confirmed that r△SL was an independent risk factor for ASD ( AUC = 0.713, 95% CI : 0.577–0.850), with an optimal predictive threshold of 2.8%. Conclusion Insufficient local curvature correction during fusion surgery accelerates degenerative changes in adjacent segments, and segmental lordosis is a critical risk factor for ASD. Adjacent segment disease Segmental lordosis Spine Posterior lumbar fusion Figures Figure 1 Figure 2 Figure 3 INTRODUCTION Adjacent segment disease (ASD) is a degenerative disease that occurs in adjacent mobile segments of the lumbar spine following lumbar fusion. It is primarily diagnosed on the basis of radiographic and clinical findings and is considered a major factor influencing the prognosis of patients undergoing lumbar fusion surgery [ 1 ] . Recent large-scale clinical studies have shown that the 5-year incidence of revision surgery for ASD after lumbar fusion is 13.6%, and the 10-year incidence reaches 22.2% [ 2 ] . This poses a significant challenge to both spine surgeons and patients, making the treatment of adjacent segment disease an urgent issue to address. The exact etiology of ASD after lumbar fusion remains unclear, but biomechanical changes induced by fusion, including increased load on the adjacent facet joints, elevated intradiscal pressure, and compensatory excessive motion in the adjacent segments, are thought to play a key role. Currently, lumbar interbody fusion is the dominant surgical method both in China and internationally. However, our institution has developed a unique posterior lumbar fusion technique—lumbar facet interlaminar fusion. This technique utilizes local bone for facet joint fusion, and a pedicled muscle‒bone flap adjacent to the vertebrae is used to increase the blood supply, accelerate local bone graft healing, and improve the accuracy and stability of bone graft placement, thus improving the fusion rate [ 3 ] . The effectiveness of this technique has been validated through animal experiments, and more than 5,000 patients with lumbar degenerative diseases have been treated with this method at our hospital, achieving satisfactory clinical outcomes and significantly reducing the incidence of pseudarthrosis, surgical costs, and operation time. In recent years, studies have shown that postfusion loss of intervertebral height in the fused segments may lead to changes in segmental lordosis. Since our institution's unique posterior facet interlaminar fusion technique is a type of lumbar fusion surgery, this issue may also exist in our procedure. Therefore, we hypothesize that segmental lordosis-related parameters may play a crucial role in the occurrence of ASD after posterior lumbar facet interlaminar fusion. The evaluation of segmental lordosis involves measuring lumbar lordosis (LL), segmental lordosis (SL), the sacral slope (SS), and the relative intervertebral height of the fused and adjacent segments via lateral radiographs of the lumbar spine to reflect the degree of lumbar lordosis. However, to the best of our knowledge, few studies have investigated the correlation between segmental lordosis-related parameters and ASD. Gong et al [ 4 ] . [4] demonstrated that segmental lordosis-related parameters are important risk factors for postoperative ASD. On the basis of previous studies, this research employs a 1:1 matching case‒control design to investigate whether segmental lordosis-related parameters after fusion are risk factors for ASD. Using professional imaging analysis software, lumbar lordosis (LL), segmental lordosis (SL), the sacral slope (SS), and the relative intervertebral height of the fused and adjacent segments are quantitatively measured to explore their potential role as risk factors for ASD after lumbar fusion. 1. Methods 1.1 Demographic data This study has been approved by the Ethics Committee of the Second Affiliated Hospital of Harbin Medical University (Approval No.: YJSKY2024-234). All patients signed the corresponding informed consent forms, and they were verbally informed before the study and understood the purposes for which their data would be used. A retrospective analysis was conducted on 27 patients who underwent revision surgery for adjacent segment disease (ASD) following lumbar facet interlaminar fusion at our hospital between February 2012 and February 2025. All surgeries were performed by the same surgical team at our institution. The inclusion criteria for the ASD group were as follows: (1) new radiographic findings in the adjacent segments of the fused segment compared with preoperative imaging, including vertebral slippage ≥ 4 mm, segmental mobility > 10°, intervertebral disc height loss > 10%, MRI indicating modification of the Pfirrmann classification to grade IV/V in the adjacent segment, or obvious adjacent segment disc herniation/spinal stenosis; and (2) clinical symptoms consistent with the aforementioned imaging findings. The indications for surgery in the ASD group included low back pain, radiculopathy, and intermittent claudication, all of which significantly impacted quality of life, with no significant improvement after 3 months of conservative treatment. The exclusion criteria for the ASD group included the following: (1) previous lumbar spine surgery; (2) lack of complete and clear preoperative, postoperative, and final follow-up lateral lumbar X-rays; and (3) three or more fused segments in the initial surgery. For the control group, patients who underwent posterior lumbar facet interlaminar fusion at the same time as those in the ASD group and who had not undergone subsequent lumbar surgery were selected. The inclusion criteria for the control group were as follows: (1) underwent lumbar facet interlaminar fusion surgery at the same spinal segment during the same period as the ASD group; and (2) no subsequent lumbar surgery. The exclusion criteria for the control group included the following: (1) previous lumbar spine surgery; (2) lack of complete and clear preoperative, postoperative, and final follow-up lateral lumbar X-rays; (3) significant radiographic degenerative changes in the adjacent segments at follow-up; and (4) clinical symptoms significantly worse than those observed after the previous surgery. 1.2 Imaging analysis We collected the required preoperative, postoperative, and follow-up lumbar spine radiographs (AP and lateral views) from the hospital’s Neusoft system. (Fig. 1 ) Two spine surgeons used Digimizer software to measure the following parameters on the lateral lumbar X-rays taken preoperatively, 3 days postoperatively, and at the final follow-up. The measurement results were averaged as follows: 1. Lumbar lordosis (LL): The angle formed between the tangent to the upper endplate of L1 and the tangent to the upper edge of S1.2. Segmental lordosis (SL): The angle formed between the tangent to the upper endplate of the upper vertebra of the fused segment and the tangent to the lower endplate of the lower vertebra of the fused segment; 3. Sacral slope (SS): The angle formed between the tangent to the upper edge of S1 and the horizontal line. Relative intervertebral height of the fused and adjacent segments: This is expressed as a ratio, with the measurement method shown in Fig. 2 . We compared the above lumbar sagittal parameters between the two groups preoperatively, 3 days postoperatively, and at the final follow-up time points to evaluate the degree of correction after the initial surgery. The results are presented as percentages. The relative difference in LL (r△LL) was calculated as (postoperative LL - preoperative LL)/preoperative LL, the relative difference in SL (r△SL) was calculated as (postoperative SL - preoperative SL)/preoperative SL, and the relative difference in disc height (r△DH) was calculated as (postoperative relative disc height - preoperative relative disc height)/preoperative relative disc height. In addition, two spine surgeons, blinded to group allocation, assessed the degree of intervertebral disc degeneration via the Pfirrmann classification. 1.3 Data analysis The data were analyzed via Social Sciences 17.0 for Windows (SPSS, Inc., Chicago, IL). Comparisons of initial surgery age, follow-up duration, and various lumbar measurement parameters between the ASD group and the control group were made via the independent samples t test for normally distributed data and the Mann‒Whitney U test for nonnormally distributed data. Comparisons between the two groups for sex, primary preoperative diagnosis, initial surgical segment, preoperative disc degeneration in the adjacent segment, and clinical comorbidities were conducted via the chi-square (χ²) test. Parameters showing significant differences were subjected to multivariate logistic regression analysis. The optimal predictive threshold for ASD was determined via receiver operating characteristic (ROC) curve analysis. A P value of < 0.05 was considered to indicate statistical significance. 2. Results 2.1 Demographic data The basic demographic information is shown in Table 1 . Among the 27 patients who underwent revision surgery due to ASD, the average age at the time of the first surgery was 62.9 ± 8.2 years, whereas the control group had an average age of 59.3 ± 7.0 years. There was no statistically significant difference between the two groups (P > 0.05). Additionally, no significant differences were found between the groups in terms of the sex ratio, initial fusion segment, comorbidities, Pfirrmann score of the adjacent segment, or follow-up duration ( P > 0.05). The patients in the ASD group were treated 3 ± 2 years after the initial surgery. Table 1 Comparison of General Information Variable ASD Group Control Group P value Age at Initial Surgery (M ± S) 62.9 ± 8.2 59.3 ± 7.0 0.090 Gender [n(%)] 0.102 Female 11 (40.7) 17 (63.0) Male 16 (59.3) 10 (37.0) Primary Diagnosis [n(%)] 0.804 Lumbar spinal canal stenosis 19 (70.4) 20 (74.1) Lumbar intervertebral disc herniation 7 (25.9) 5 (18.5) Lumbar spondylolisthesis 1 (3.7) 2 (7.4) Pfirrmann's Grading of the Upper Adjacent Segment Intervertebral Disc before Surgery [n(%)] 0.541 Grade II 3 (11.1) 4 (14.8) Grade III 22 (81.5) 23 (85.2) Grade IV 2 (7.4) 0 (0) Pfirrmann's Grading of the Lower Adjacent Segment Intervertebral Disc before Surgery [n(%)] 1.000 Grade II 4 (14.8) 4 (14.8) Grade III 22 (81.5) 23 (85.2) Grade IV 1 (3.7) 0 (0) Segments of the First Fusion Surgery [n(%)] 1.000 Single segment - L4-5 13 (48.2) 14 (51.9) Single segment - L3-4 3 (11.1) 2 (7.4) Double segments - L3-5 11 (40.7) 11 (40.7) Underlying Diseases [n(%)] Hypertension 0.573 No 16 (59.3) 18 (66.7) Yes 11 (40.7) 9 (33.3) Diabetes 1.000 No 24 (88.9) 24 (88.9) Yes 3 (11.1) 3 (11.1) History of Cerebral Infarction 0.491 No 25 (92.6) 27 (100) Yes 2 (7.4) 0 (0) 2.2 Lumbar Sagittal Parameters As shown in Table 2 , there were no significant differences between the two groups in terms of the preoperative values of LL, SL, and SS; relative intervertebral height; upper intervertebral height; or lower intervertebral height. Postoperatively, the ASD group presented significantly lower LL and SS values than did the control group ( P < 0.05). However, there were no significant differences between the two groups in terms of postoperative SL, relative intervertebral height, or upper and lower intervertebral heights. At the final follow-up, the upper intervertebral height in the ASD group was significantly lower than that in the control group ( P = 0.020). Table 2 Comparison of Lumbar Sagittal Parameters Variable ASD Group Control Group P value Initial Preoperative Parameters LL (°) 33.8 ± 14.1 38.2 ± 16.5 0.306 SL (°) 14.7 ± 11.0 14.8 ± 15.3 0.710 SS (°) 27.5 ± 8.5 29.6 ± 8.9 0.374 Relative Intervertebral Disc Height (%) 31.3 ± 6.4 32.4 ± 8.2 0.570 Relative Intervertebral Disc Height of the Lower Level (%) 29.2 ± 6.0 31.5 ± 8.9 0.273 Relative Intervertebral Disc Height of the Upper Level (%) 30.7 ± 6.5 34.0 ± 8.6 0.117 Initial Postoperative Parameters LL (°) 34.9 ± 12.1 42.9 ± 13.2 0.025 SL (°) 19.2 ± 7.7 23.7 ± 9.0 0.054 SS (°) 28.9 ± 7.4 35.2 ± 8.7 0.006 Relative Intervertebral Disc Height (%) 33.0 ± 4.9 37.1 ± 13.8 0.180 Relative Intervertebral Disc Height of the Lower Level (%) 32.2 ± 7.4 33.5 ± 7.7 0.515 Relative Intervertebral Disc Height of the Upper Level (%) 37.2 ± 6.2 37.8 ± 8.3 0.787 Parameters at the Last Follow-up LL (°) 34.8 ± 11.0 40.0 ± 15.0 0.154 SL (°) 14.8 ± 16.0 20.5 ± 16.9 0.080 SS (°) 27.4 ± 8.0 31.4 ± 13.5 0.188 Relative Intervertebral Disc Height (%) 28.2 ± 6.3 30.9 ± 7.8 0.170 Relative Intervertebral Disc Height of the Lower Level (%) 28.7 ± 8.4 31.8 ± 7.4 0.149 Relative Intervertebral Disc Height of the Upper Level (%) 29.4 ± 5.9 33.7 ± 7.2 0.020 2.3 Postoperative Lumbar Sagittal Parameter Correction As shown in Table 3 , when the postoperative parameters were compared with the preoperative values, the r△SL in the ASD group was significantly lower than that in the control group ( P < 0.01). However, there were no significant differences between the two groups for r△LL, r△SS, relative intervertebral height, or upper and lower intervertebral heights. Table 3 Postoperative Lumbar Sagittal Parameter Correction Variable ASD Group Control Group P value LL (°) 2.7 ± 52.6 16.3 ± 49.9 0.180 SL (°) 24.0 ± 58.1 45.2 ± 120.6 0.007 SS (°) 10.3 ± 28.7 25.1 ± 32.9 0.085 Relative Intervertebral Disc Height (%) Relative Intervertebral Disc Height of the Lower Level (%) Relative Intervertebral Disc Height of the Upper Level (%) 2.6 ± 27.9 13.3 ± 30.4 19.8 ± 28.7 10.9 ± 27.8 12.6 ± 33.2 12.7 ± 23.2 0.264 0.932 0.095 2.4 Multivariate logistic regression analysis Variables with statistically significant differences in the preoperative, postoperative, and relative correction values of the lumbar sagittal parameters were subjected to multivariate logistic regression analysis. As shown in Table 4 , a smaller r△SL was identified as an independent risk factor for the occurrence of ASD ( P = 0.004, OR = 0.973, 95% confidence interval: 0.955–0.991). Receiver operating characteristic (ROC) curve analysis revealed that the area under the curve (AUC) for r△SL was 0.713 (95% confidence interval: 0.577–0.850). The optimal predictive threshold for r△SL was found to be 2.8%, where sensitivity and specificity were maximized (see Fig. 3 ). Table 4 Logistic regression model with ASD as the dependent variable Independent Variable P value OR (95% CI) Postoperative LL 0.316 0.959 (0.883–1.041) Postoperative SS 0.082 0.869 (0.742–1.018) r△SL 0.004 0.973 (0.955–0.991) 3. Discussion In recent years, spinal fusion surgery has become the standard procedure for treating degenerative lumbar spine diseases. Moreover, the incidence of long-term complications such as adjacent segment disease (ASD) has been steadily increasing. The 5-year revision surgery rate for ASD after lumbar fusion is 13.6%, and the 10-year rate reaches 22.2%. Therefore, to reduce the incidence of adjacent segment disease and alleviate the pain of secondary surgeries for patients, scholars worldwide have conducted extensive research on the risk factors for ASD, hoping to develop corresponding interventions to lower its incidence. An increasing number of studies have focused on the relationship between lumbar segmental lordosis (SL) and adjacent segment disease. This is promising because, postfusion, the height of the intervertebral disc of the fused segment is often reduced, and postoperative segmental lordosis may change. This alters the biomechanics of adjacent segments and even the entire lumbar spine, which plays a crucial role in the development of ASD. Currently, the measurement of lumbar segmental lordosis-related parameters is relatively standardized and mainly involves measuring lumbar lordosis (LL), segmental lordosis (SL), sacral slope (SS), and intervertebral disc height. Biomechanical studies have confirmed that a reduction in lumbar lordosis may accelerate the onset of adjacent segment disease [ 5 ] . Tsuang et al. [ 6 ] established finite element models with varying lordotic angles and reported that, in all the fusion models, the overall range of motion in the adjacent cranial segment increased. As the range of motion increased, the maximum von Mises stress on the intervertebral disc and the facet joint contact forces in the cranial adjacent segment also changed, which was similar to the results obtained by Zhao et al. [ 7 ] . This study followed a strict 1:1 matching protocol, matching 27 ASD patients with 27 control patients on the basis of demographic parameters. The results revealed that, after the initial fusion surgery, the ASD group had significantly lower LL, SS, and relative intervertebral disc height than did the control group ( P < 0.05). Furthermore, when the postoperative correction values of the lumbar sagittal parameters were compared, the r△SL in the ASD group was significantly smaller than that in the control group ( P < 0.05), confirming that patients in the ASD group had insufficient local curvature correction. The multivariate logistic regression analysis indicated that r△SL is an independent risk factor for ASD, further emphasizing that inadequate local curvature correction increases the risk of postoperative ASD in patients undergoing spinal fusion. The optimal predictive threshold for r△SL in the occurrence of ASD was 2.8%. Segmental lordosis (SL) reflects the curvature of the fused segment, which is mainly altered intraoperatively through the curvature of the fixation rods, making it a controllable factor for the surgeon. These findings have important clinical value for reducing the incidence of ASD. Numerous studies have shown that SL significantly impacts the efficacy of lumbar fusion surgery. Bae et al. [ 8 ] reported that restoring a normal SL is essential for preventing ASD. Nakashima et al. [ 9 ] conducted a follow-up study on 1,001 patients and reported that pelvic anteversion is a significant risk factor for adjacent segment disease, indicating that achieving proper lumbar lordosis during PLIF (posterior lumbar interbody fusion) is crucial for preventing ASD. Takahashi et al. [ 10 ] found that patients with larger ΔSLs had significantly higher Japanese Orthopedic Association (JOA) scores during follow-up, and their clinical outcomes were generally more satisfactory. Toivonen et al. [ 11 ] In a 10-year follow-up study, a higher LL outside the fused segment (LL - segmental lordosis) could reduce the risk of revision surgery due to ASD, which is consistent with our study, where the ASD group had significantly lower postoperative LL than did the control group. Every individual is unique, with variations in body function, lumbar spine curvature, and the ability to adapt to curvature. Therefore, preoperative SL or postoperative SL alone may not adequately reflect the relationship with adjacent segment disease. Similarly, the degree of influence of △SL on the original curvature varies among patients. Thus, on the basis of previous studies, we introduced the r△SL parameter in this study, which enhances the scientific credibility of the findings. Gong et al. [ 12 ] studied the occurrence of ASD following single-segment posterior fusion and identified preoperative MF muscle CSA (cross-sectional area) at L3–L4, as well as the FI (facet index) and BMD (bone mineral density) at L4–L5 and L5–S1, as significant risk factors for ASD. Wang et al. [ 13 ] followed up 189 PLF (posterior lumbar fusion) patients for at least 2 years and reported that the incidence of ASD increased with increasing postoperative time, the distance between the pedicle screw tip and the superior endplate decreased, and the sagittal angle between the pedicle screw and the superior endplate increased. Notably, when the distance was 5.5°, the risk of ASD increased. Bagheri et al. [ 14 ] retrospectively analyzed 630 patients who underwent posterior lumbar fusion and reported that preoperative BMI, preoperative disc degeneration, reduced postoperative lumbar lordosis, fusion of more than four segments, and intraoperative facet joint involvement increased the risk of ASD. Wang et al. [ 15 ] observed that patients with LL correction ≥ 10° and PI-LL correction ≥ 20° had a greater incidence of ASD in patients over 60, indicating that the ideal LL correction for older patients differs from that for younger patients because of the changes in lumbar lordosis with age. This study included only patients with adjacent segment disease following short-segment fusion surgeries at our center. Data analysis revealed no statistically significant difference in the incidence of ASD between fusion segments of two or fewer levels. This finding does not contradict the conclusion of Wang et al. [ 16 ] that long-segment fusion is a risk factor for adjacent segment disease. There are several limitations in this study. The sample size was small, and the time span was long, with only 27 cases of ASD. This limitation arose because preoperative, postoperative, and follow-up images could only be collected at our research center, restricting the sample size. There is an optimal range for lumbar curvature correction, but this study only provides the lower limit. Given the personalized characteristics of each patient's lumbar spine, further research with larger sample sizes, more detailed subgroup analyses, and the inclusion of other lumbar parameters is needed. Additionally, since the number of patients with single-segment and dual-segment ASDs in our center was similar, we did not analyze the distinct effects of single- versus dual-segment fusion on ASDs. The relative intervertebral disc height of dual-segment fusion was represented as the average of both segments, which may not be entirely appropriate and warrants further investigation. 4. Conclusion This study compared preoperative, postoperative, and follow-up lumbar sagittal parameters (LL, SL, SS, and relative intervertebral disc height) between the ASD and control groups. It was concluded that segmental lordosis is an important risk factor for ASD after lumbar posterior facet interbody fusion. Surgeons should focus on this issue during surgery and adjust the curvature of the fixation rods to achieve effective local curvature correction. Effective correction of the local curvature can significantly reduce the risk of ASD. Declarations Ethics approval and consent to participate: All patients provided written informed consent prior to the study, which was conducted in accordance with the principles of the Declaration of Helsinki. Ethical approval was obtained from the Institutional Ethics Committee of the Second Affiliated Hospital of Harbin Medical University. Clinical trial registration: Not applicable. Consent for publication: Not applicable Competing interests: The authors declare that they have no competing interests. Author Contribution HBQ performed the analysis and interpretation of patient data, and drafted the manuscript; HBQ and CYX designed the study; CYX performed the surgery; JLY and GXW collected the data; CH, XZ and PYK translated the manuscript. All authors read and approved the final manuscript. Availability of data and materials: The datasets used and/or analyzed during the current study are available from the corresponding author upon reasonable request. References Zongjun M, Xiaoyin L, Jianqun Z, Peng W, Zhen C, Simin L, et al. Comparative Analysis of the Efficacy of Three Lumbar Fixation and Fusion Procedures in the Treatment of Adjacent Segment Disease after Lumbar Surgery. Chinese Journal of Spine and Spinal Cord. 2022;32(12):1102-11. Mobbs RJ, Phan K, Malham G, Seex K, Rao PJ. Lumbar interbody fusion: techniques, indications and comparison of interbody fusion options including PLIF, TLIF, MI-TLIF, OLIF/ATP, LLIF and ALIF. J Spine Surg. 2015;1(1):2-18. 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Wang SJ, Zhang SB, Yi YY, Xu HW, Wu DS. Estimation of the ideal correction of lumbar lordosis to prevent reoperation for symptomatic adjacent segment disease after lumbar fusion in older people. BMC Musculoskelet Disord. 2020;21(1):429. Wang T, Ding W. Risk factors for adjacent segment degeneration after posterior lumbar fusion surgery in treatment for degenerative lumbar disorders: a meta-analysis. J Orthop Surg Res. 2020;15(1):582. Additional Declarations No competing interests reported. Cite Share Download PDF Status: Posted Version 1 posted You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. 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Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-6201144","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":446712822,"identity":"da56ed3b-1eb9-41eb-9cb6-f5b105a7c0af","order_by":0,"name":"Haibiao Qin","email":"","orcid":"","institution":"哈尔滨医科大学附属第二医院","correspondingAuthor":false,"prefix":"","firstName":"Haibiao","middleName":"","lastName":"Qin","suffix":""},{"id":446712824,"identity":"c172dda6-64ff-4128-8c7a-455a634ca5d0","order_by":1,"name":"Jinglong Yan","email":"","orcid":"","institution":"哈尔滨医科大学附属第二医院","correspondingAuthor":false,"prefix":"","firstName":"Jinglong","middleName":"","lastName":"Yan","suffix":""},{"id":446712826,"identity":"07ea624f-ea5d-4647-8a4d-4f839df11cc7","order_by":2,"name":"Guangxi Wang","email":"","orcid":"","institution":"哈尔滨医科大学附属第二医院","correspondingAuthor":false,"prefix":"","firstName":"Guangxi","middleName":"","lastName":"Wang","suffix":""},{"id":446712827,"identity":"37e1b7b4-d40b-4939-98c7-910f11c0933b","order_by":3,"name":"Hui Chi","email":"","orcid":"","institution":"哈尔滨医科大学附属第二医院","correspondingAuthor":false,"prefix":"","firstName":"Hui","middleName":"","lastName":"Chi","suffix":""},{"id":446712828,"identity":"b1c95f76-65de-4652-aa14-5f3aaf278827","order_by":4,"name":"Xu Zhang","email":"","orcid":"","institution":"哈尔滨医科大学附属第二医院","correspondingAuthor":false,"prefix":"","firstName":"Xu","middleName":"","lastName":"Zhang","suffix":""},{"id":446712830,"identity":"f8ab513d-a0f5-4e12-9b03-b7e1f0ea87a8","order_by":5,"name":"Pengyu Kong","email":"","orcid":"","institution":"哈尔滨医科大学附属第二医院","correspondingAuthor":false,"prefix":"","firstName":"Pengyu","middleName":"","lastName":"Kong","suffix":""},{"id":446712831,"identity":"4c87ef0e-6a0d-457f-8668-c09944c02102","order_by":6,"name":"Chunyang Xi","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAABE0lEQVRIiWNgGAWjYDACZgY2GJPxQYKBjRwDO2MD0VqYDT5UpBkzMBPSwoDQwiY548yhxAZmAuoNjjM/e8y747C8Of8CBmnetgPp/c3MbdK8Oxjk+cUOYNUi2cxmbsx75rDhzhkPGIx52+7kzjjMCNRyhsFw5uwErFr4mXnYgIYfZtxw4wBDMm/bs9wGsJY2hgSD29i1sEG12IO0HAYy0uUJaYHZkrjhfANj44wzhxMMCGkB+sVMcm5bevKGG8DwBgay4cbDjM2Wc9skcPrF4PzhZxJv26xtN5w/wP4DGJXycsfbH95422Yjzy+NXQsUNDMwSOR/gPFYJIBcfMpBoA7oqwNwHvMH3CpHwSgYBaNgBAIACVZczdsYqf8AAAAASUVORK5CYII=","orcid":"","institution":"哈尔滨医科大学附属第二医院","correspondingAuthor":true,"prefix":"","firstName":"Chunyang","middleName":"","lastName":"Xi","suffix":""}],"badges":[],"createdAt":"2025-03-11 08:08:19","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-6201144/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-6201144/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":82119441,"identity":"dad60aff-e8e9-4c20-8325-a80f392181db","added_by":"auto","created_at":"2025-05-07 03:09:52","extension":"jpg","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":40369,"visible":true,"origin":"","legend":"\u003cp\u003eshows lateral radiographs of a 60-year-old male patient who underwent L4–L5 posterior lumbar facet joint fusion for lumbar spinal stenosis in 2022. Two years later, the patient underwent revision surgery for adjacent segment disease at L3--L4. Panel A shows the preoperative lateral radiograph, Panel B shows the postoperative radiograph, and Panel C shows the radiograph at the final follow-up.\u003c/p\u003e","description":"","filename":"1.jpg","url":"https://assets-eu.researchsquare.com/files/rs-6201144/v1/b3e8b924fda9086adad825ac.jpg"},{"id":82119443,"identity":"1ecc8a4d-39d4-44b3-82b5-e4976d2fda70","added_by":"auto","created_at":"2025-05-07 03:09:52","extension":"jpg","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":23610,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cem\u003eMeasurement methods for the lumbar lordotic angle, segmental lordotic angle, and relative intervertebral disc height. The relative intervertebral disc height is expressed as (a+b)/2c, where \u003c/em\u003e\u003cem\u003e\u003cstrong\u003ea\u003c/strong\u003e\u003c/em\u003e\u003cem\u003e is thedistance between the posterior edge of the inferior endplate of the upper vertebral body and the posterior edge of the superior endplate of the lower vertebral body; \u003c/em\u003e\u003cem\u003e\u003cstrong\u003eb\u003c/strong\u003e\u003c/em\u003e\u003cem\u003e is thedistance between the anterior edge of the inferior endplate of the upper vertebral body and the anterior edge of the superior endplate of the lower vertebral body; and c is the distance between the anterior edges of the superior and inferior endplates of the upper vertebral body.\u003c/em\u003e\u003c/p\u003e","description":"","filename":"2.jpg","url":"https://assets-eu.researchsquare.com/files/rs-6201144/v1/836bf3ce7079826b17e0ada9.jpg"},{"id":82120653,"identity":"8e289d06-bae5-4738-a4e6-b199c8d44b98","added_by":"auto","created_at":"2025-05-07 03:17:52","extension":"jpg","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":25600,"visible":true,"origin":"","legend":"\u003cp\u003eLegend not included with this version\u003c/p\u003e","description":"","filename":"3.jpg","url":"https://assets-eu.researchsquare.com/files/rs-6201144/v1/e287fb35e08c3ae82e43b2e8.jpg"},{"id":83663316,"identity":"e05d55d1-8b06-4231-b40d-d1a0280ce8c3","added_by":"auto","created_at":"2025-05-30 10:39:03","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":831185,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-6201144/v1/573987b8-7910-40db-8f5c-6ce49dcb5f8e.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"Study of the Correlation between Adjacent Segment Disease and Segmental Lordosis After Lumbar Facet Joint Fusion Surgery","fulltext":[{"header":"INTRODUCTION","content":"\u003cp\u003eAdjacent segment disease (ASD) is a degenerative disease that occurs in adjacent mobile segments of the lumbar spine following lumbar fusion. It is primarily diagnosed on the basis of radiographic and clinical findings and is considered a major factor influencing the prognosis of patients undergoing lumbar fusion surgery\u003csup\u003e[\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e]\u003c/sup\u003e. Recent large-scale clinical studies have shown that the 5-year incidence of revision surgery for ASD after lumbar fusion is 13.6%, and the 10-year incidence reaches 22.2%\u003csup\u003e[\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e]\u003c/sup\u003e. This poses a significant challenge to both spine surgeons and patients, making the treatment of adjacent segment disease an urgent issue to address. The exact etiology of ASD after lumbar fusion remains unclear, but biomechanical changes induced by fusion, including increased load on the adjacent facet joints, elevated intradiscal pressure, and compensatory excessive motion in the adjacent segments, are thought to play a key role.\u003c/p\u003e \u003cp\u003eCurrently, lumbar interbody fusion is the dominant surgical method both in China and internationally. However, our institution has developed a unique posterior lumbar fusion technique\u0026mdash;lumbar facet interlaminar fusion. This technique utilizes local bone for facet joint fusion, and a pedicled muscle‒bone flap adjacent to the vertebrae is used to increase the blood supply, accelerate local bone graft healing, and improve the accuracy and stability of bone graft placement, thus improving the fusion rate\u003csup\u003e[\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e]\u003c/sup\u003e. The effectiveness of this technique has been validated through animal experiments, and more than 5,000 patients with lumbar degenerative diseases have been treated with this method at our hospital, achieving satisfactory clinical outcomes and significantly reducing the incidence of pseudarthrosis, surgical costs, and operation time.\u003c/p\u003e \u003cp\u003eIn recent years, studies have shown that postfusion loss of intervertebral height in the fused segments may lead to changes in segmental lordosis. Since our institution's unique posterior facet interlaminar fusion technique is a type of lumbar fusion surgery, this issue may also exist in our procedure. Therefore, we hypothesize that segmental lordosis-related parameters may play a crucial role in the occurrence of ASD after posterior lumbar facet interlaminar fusion. The evaluation of segmental lordosis involves measuring lumbar lordosis (LL), segmental lordosis (SL), the sacral slope (SS), and the relative intervertebral height of the fused and adjacent segments via lateral radiographs of the lumbar spine to reflect the degree of lumbar lordosis. However, to the best of our knowledge, few studies have investigated the correlation between segmental lordosis-related parameters and ASD. Gong et al\u003csup\u003e[\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e]\u003c/sup\u003e. [4] demonstrated that segmental lordosis-related parameters are important risk factors for postoperative ASD.\u003c/p\u003e \u003cp\u003eOn the basis of previous studies, this research employs a 1:1 matching case‒control design to investigate whether segmental lordosis-related parameters after fusion are risk factors for ASD. Using professional imaging analysis software, lumbar lordosis (LL), segmental lordosis (SL), the sacral slope (SS), and the relative intervertebral height of the fused and adjacent segments are quantitatively measured to explore their potential role as risk factors for ASD after lumbar fusion.\u003c/p\u003e"},{"header":"1. Methods","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e \u003ch2\u003e1.1 Demographic data\u003c/h2\u003e \u003cp\u003e This study has been approved by the Ethics Committee of the Second Affiliated Hospital of Harbin Medical University (Approval No.: YJSKY2024-234). All patients signed the corresponding informed consent forms, and they were verbally informed before the study and understood the purposes for which their data would be used. A retrospective analysis was conducted on 27 patients who underwent revision surgery for adjacent segment disease (ASD) following lumbar facet interlaminar fusion at our hospital between February 2012 and February 2025. All surgeries were performed by the same surgical team at our institution.\u003c/p\u003e \u003cp\u003eThe inclusion criteria for the ASD group were as follows: (1) new radiographic findings in the adjacent segments of the fused segment compared with preoperative imaging, including vertebral slippage\u0026thinsp;\u0026ge;\u0026thinsp;4 mm, segmental mobility\u0026thinsp;\u0026gt;\u0026thinsp;10\u0026deg;, intervertebral disc height loss\u0026thinsp;\u0026gt;\u0026thinsp;10%, MRI indicating modification of the Pfirrmann classification to grade IV/V in the adjacent segment, or obvious adjacent segment disc herniation/spinal stenosis; and (2) clinical symptoms consistent with the aforementioned imaging findings. The indications for surgery in the ASD group included low back pain, radiculopathy, and intermittent claudication, all of which significantly impacted quality of life, with no significant improvement after 3 months of conservative treatment.\u003c/p\u003e \u003cp\u003eThe exclusion criteria for the ASD group included the following: (1) previous lumbar spine surgery; (2) lack of complete and clear preoperative, postoperative, and final follow-up lateral lumbar X-rays; and (3) three or more fused segments in the initial surgery.\u003c/p\u003e \u003cp\u003eFor the control group, patients who underwent posterior lumbar facet interlaminar fusion at the same time as those in the ASD group and who had not undergone subsequent lumbar surgery were selected. The inclusion criteria for the control group were as follows: (1) underwent lumbar facet interlaminar fusion surgery at the same spinal segment during the same period as the ASD group; and (2) no subsequent lumbar surgery. The exclusion criteria for the control group included the following: (1) previous lumbar spine surgery; (2) lack of complete and clear preoperative, postoperative, and final follow-up lateral lumbar X-rays; (3) significant radiographic degenerative changes in the adjacent segments at follow-up; and (4) clinical symptoms significantly worse than those observed after the previous surgery.\u003c/p\u003e \u003c/div\u003e\n\u003ch3\u003e1.2 Imaging analysis\u003c/h3\u003e\n\u003cp\u003eWe collected the required preoperative, postoperative, and follow-up lumbar spine radiographs (AP and lateral views) from the hospital\u0026rsquo;s Neusoft system. (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e) Two spine surgeons used Digimizer software to measure the following parameters on the lateral lumbar X-rays taken preoperatively, 3 days postoperatively, and at the final follow-up. The measurement results were averaged as follows: 1. Lumbar lordosis (LL): The angle formed between the tangent to the upper endplate of L1 and the tangent to the upper edge of S1.2. Segmental lordosis (SL): The angle formed between the tangent to the upper endplate of the upper vertebra of the fused segment and the tangent to the lower endplate of the lower vertebra of the fused segment; 3. Sacral slope (SS): The angle formed between the tangent to the upper edge of S1 and the horizontal line. Relative intervertebral height of the fused and adjacent segments: This is expressed as a ratio, with the measurement method shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eWe compared the above lumbar sagittal parameters between the two groups preoperatively, 3 days postoperatively, and at the final follow-up time points to evaluate the degree of correction after the initial surgery. The results are presented as percentages. The relative difference in LL (r△LL) was calculated as (postoperative LL - preoperative LL)/preoperative LL, the relative difference in SL (r△SL) was calculated as (postoperative SL - preoperative SL)/preoperative SL, and the relative difference in disc height (r△DH) was calculated as (postoperative relative disc height - preoperative relative disc height)/preoperative relative disc height.\u003c/p\u003e \u003cp\u003eIn addition, two spine surgeons, blinded to group allocation, assessed the degree of intervertebral disc degeneration via the Pfirrmann classification.\u003c/p\u003e\n\u003ch3\u003e1.3 Data analysis\u003c/h3\u003e\n\u003cp\u003eThe data were analyzed via Social Sciences 17.0 for Windows (SPSS, Inc., Chicago, IL). Comparisons of initial surgery age, follow-up duration, and various lumbar measurement parameters between the ASD group and the control group were made via the independent samples t test for normally distributed data and the Mann‒Whitney U test for nonnormally distributed data. Comparisons between the two groups for sex, primary preoperative diagnosis, initial surgical segment, preoperative disc degeneration in the adjacent segment, and clinical comorbidities were conducted via the chi-square (χ\u0026sup2;) test. Parameters showing significant differences were subjected to multivariate logistic regression analysis. The optimal predictive threshold for ASD was determined via receiver operating characteristic (ROC) curve analysis. A P value of \u0026lt;\u0026thinsp;0.05 was considered to indicate statistical significance.\u003c/p\u003e"},{"header":"2. Results","content":"\u003cdiv id=\"Sec7\" class=\"Section2\"\u003e \u003ch2\u003e2.1 Demographic data\u003c/h2\u003e \u003cp\u003eThe basic demographic information is shown in Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e. Among the 27 patients who underwent revision surgery due to ASD, the average age at the time of the first surgery was 62.9 ± 8.2 years, whereas the control group had an average age of 59.3 ± 7.0 years. There was no statistically significant difference between the two groups \u003cem\u003e(P\u003c/em\u003e \u0026gt; 0.05). Additionally, no significant differences were found between the groups in terms of the sex ratio, initial fusion segment, comorbidities, Pfirrmann score of the adjacent segment, or follow-up duration (\u003cem\u003eP\u003c/em\u003e \u0026gt; 0.05). The patients in the ASD group were treated 3 ± 2 years after the initial surgery.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e\u003cdiv class=\"gridtable\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e\u003ctable float=\"Yes\" id=\"Tab1\" border=\"1\"\u003e\u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eComparison of General Information\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e\u003ccolgroup cols=\"4\"\u003e\u003c/colgroup\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eVariable\u003c/p\u003e \u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eASD Group\u003c/p\u003e \u003c/th\u003e\u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eControl Group\u003c/p\u003e \u003c/th\u003e\u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eP value\u003c/p\u003e \u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eAge at Initial Surgery (M ± S)\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e62.9 ± 8.2\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e59.3 ± 7.0\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.090\u003c/p\u003e \u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eGender [n(%)]\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.102\u003c/p\u003e \u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eFemale\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e11 (40.7)\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e17 (63.0)\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eMale\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e16 (59.3)\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e10 (37.0)\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003ePrimary Diagnosis [n(%)]\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.804\u003c/p\u003e \u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eLumbar spinal canal stenosis\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e19 (70.4)\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e20 (74.1)\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eLumbar intervertebral disc herniation\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e7 (25.9)\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e5 (18.5)\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eLumbar spondylolisthesis\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e1 (3.7)\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e2 (7.4)\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003ePfirrmann's Grading of the Upper Adjacent Segment Intervertebral Disc before Surgery [n(%)]\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.541\u003c/p\u003e \u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eGrade II\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e3 (11.1)\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e4 (14.8)\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eGrade III\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e22 (81.5)\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e23 (85.2)\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eGrade IV\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e2 (7.4)\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0 (0)\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003ePfirrmann's Grading of the Lower Adjacent Segment Intervertebral Disc before Surgery [n(%)]\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e1.000\u003c/p\u003e \u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eGrade II\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e4 (14.8)\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e4 (14.8)\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eGrade III\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e22 (81.5)\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e23 (85.2)\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eGrade IV\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e1 (3.7)\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0 (0)\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eSegments of the First Fusion Surgery [n(%)]\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e1.000\u003c/p\u003e \u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eSingle segment - L4-5\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e13 (48.2)\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e14 (51.9)\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eSingle segment - L3-4\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e3 (11.1)\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e2 (7.4)\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eDouble segments - L3-5\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e11 (40.7)\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e11 (40.7)\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eUnderlying Diseases [n(%)]\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eHypertension\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.573\u003c/p\u003e \u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eNo\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e16 (59.3)\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e18 (66.7)\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eYes\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e11 (40.7)\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e9 (33.3)\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eDiabetes\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e1.000\u003c/p\u003e \u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eNo\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e24 (88.9)\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e24 (88.9)\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eYes\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e3 (11.1)\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e3 (11.1)\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eHistory of Cerebral Infarction\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.491\u003c/p\u003e \u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eNo\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e25 (92.6)\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e27 (100)\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eYes\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e2 (7.4)\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0 (0)\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/table\u003e\u003c/div\u003e \u003cp\u003e\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec8\" class=\"Section2\"\u003e \u003ch2\u003e2.2 Lumbar Sagittal Parameters\u003c/h2\u003e \u003cp\u003eAs shown in Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e, there were no significant differences between the two groups in terms of the preoperative values of LL, SL, and SS; relative intervertebral height; upper intervertebral height; or lower intervertebral height. Postoperatively, the ASD group presented significantly lower LL and SS values than did the control group (\u003cem\u003eP\u003c/em\u003e \u0026lt; 0.05). However, there were no significant differences between the two groups in terms of postoperative SL, relative intervertebral height, or upper and lower intervertebral heights. At the final follow-up, the upper intervertebral height in the ASD group was significantly lower than that in the control group (\u003cem\u003eP\u003c/em\u003e = 0.020).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e\u003cdiv class=\"gridtable\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\"±\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\"±\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e\u003ctable float=\"Yes\" id=\"Tab2\" border=\"1\"\u003e\u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 2\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eComparison of Lumbar Sagittal Parameters\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e\u003ccolgroup cols=\"4\"\u003e\u003c/colgroup\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eVariable\u003c/p\u003e \u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eASD\u003c/p\u003e \u003cp\u003eGroup\u003c/p\u003e \u003c/th\u003e\u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eControl Group\u003c/p\u003e \u003c/th\u003e\u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eP value\u003c/p\u003e \u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eInitial Preoperative Parameters\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eLL (°)\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\"±\" colname=\"c2\"\u003e \u003cp\u003e33.8 ± 14.1\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\"±\" colname=\"c3\"\u003e \u003cp\u003e38.2 ± 16.5\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.306\u003c/p\u003e \u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eSL (°)\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\"±\" colname=\"c2\"\u003e \u003cp\u003e14.7 ± 11.0\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\"±\" colname=\"c3\"\u003e \u003cp\u003e14.8 ± 15.3\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.710\u003c/p\u003e \u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eSS (°)\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\"±\" colname=\"c2\"\u003e \u003cp\u003e27.5 ± 8.5\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\"±\" colname=\"c3\"\u003e \u003cp\u003e29.6 ± 8.9\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.374\u003c/p\u003e \u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eRelative Intervertebral Disc Height (%)\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\"±\" colname=\"c2\"\u003e \u003cp\u003e31.3 ± 6.4\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\"±\" colname=\"c3\"\u003e \u003cp\u003e32.4 ± 8.2\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.570\u003c/p\u003e \u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eRelative Intervertebral Disc Height of the Lower Level (%)\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\"±\" colname=\"c2\"\u003e \u003cp\u003e29.2 ± 6.0\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\"±\" colname=\"c3\"\u003e \u003cp\u003e31.5 ± 8.9\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.273\u003c/p\u003e \u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eRelative Intervertebral Disc Height of the Upper Level (%)\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\"±\" colname=\"c2\"\u003e \u003cp\u003e30.7 ± 6.5\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\"±\" colname=\"c3\"\u003e \u003cp\u003e34.0 ± 8.6\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.117\u003c/p\u003e \u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eInitial Postoperative Parameters\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eLL (°)\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\"±\" colname=\"c2\"\u003e \u003cp\u003e34.9 ± 12.1\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\"±\" colname=\"c3\"\u003e \u003cp\u003e42.9 ± 13.2\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.025\u003c/p\u003e \u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eSL (°)\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\"±\" colname=\"c2\"\u003e \u003cp\u003e19.2 ± 7.7\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\"±\" colname=\"c3\"\u003e \u003cp\u003e23.7 ± 9.0\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.054\u003c/p\u003e \u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eSS (°)\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\"±\" colname=\"c2\"\u003e \u003cp\u003e28.9 ± 7.4\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\"±\" colname=\"c3\"\u003e \u003cp\u003e35.2 ± 8.7\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.006\u003c/p\u003e \u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eRelative Intervertebral Disc Height (%)\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\"±\" colname=\"c2\"\u003e \u003cp\u003e33.0 ± 4.9\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\"±\" colname=\"c3\"\u003e \u003cp\u003e37.1 ± 13.8\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.180\u003c/p\u003e \u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eRelative Intervertebral Disc Height of the Lower Level (%)\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\"±\" colname=\"c2\"\u003e \u003cp\u003e32.2 ± 7.4\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\"±\" colname=\"c3\"\u003e \u003cp\u003e33.5 ± 7.7\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.515\u003c/p\u003e \u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eRelative Intervertebral Disc Height of the Upper Level (%)\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\"±\" colname=\"c2\"\u003e \u003cp\u003e37.2 ± 6.2\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\"±\" colname=\"c3\"\u003e \u003cp\u003e37.8 ± 8.3\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.787\u003c/p\u003e \u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eParameters at the Last Follow-up\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eLL (°)\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\"±\" colname=\"c2\"\u003e \u003cp\u003e34.8 ± 11.0\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\"±\" colname=\"c3\"\u003e \u003cp\u003e40.0 ± 15.0\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.154\u003c/p\u003e \u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eSL (°)\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\"±\" colname=\"c2\"\u003e \u003cp\u003e14.8 ± 16.0\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\"±\" colname=\"c3\"\u003e \u003cp\u003e20.5 ± 16.9\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.080\u003c/p\u003e \u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eSS (°)\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\"±\" colname=\"c2\"\u003e \u003cp\u003e27.4 ± 8.0\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\"±\" colname=\"c3\"\u003e \u003cp\u003e31.4 ± 13.5\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.188\u003c/p\u003e \u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eRelative Intervertebral Disc Height (%)\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\"±\" colname=\"c2\"\u003e \u003cp\u003e28.2 ± 6.3\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\"±\" colname=\"c3\"\u003e \u003cp\u003e30.9 ± 7.8\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.170\u003c/p\u003e \u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eRelative Intervertebral Disc Height of the Lower Level (%)\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\"±\" colname=\"c2\"\u003e \u003cp\u003e28.7 ± 8.4\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\"±\" colname=\"c3\"\u003e \u003cp\u003e31.8 ± 7.4\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.149\u003c/p\u003e \u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eRelative Intervertebral Disc Height of the Upper Level (%)\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\"±\" colname=\"c2\"\u003e \u003cp\u003e29.4 ± 5.9\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\"±\" colname=\"c3\"\u003e \u003cp\u003e33.7 ± 7.2\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.020\u003c/p\u003e \u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/table\u003e\u003c/div\u003e \u003cp\u003e\u003c/p\u003e \u003c/div\u003e\n\u003ch3\u003e2.3 Postoperative Lumbar Sagittal Parameter Correction\u003c/h3\u003e\n\u003cp\u003eAs shown in Table\u0026nbsp;\u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\u003e, when the postoperative parameters were compared with the preoperative values, the r△SL in the ASD group was significantly lower than that in the control group (\u003cem\u003eP\u003c/em\u003e \u0026lt; 0.01). However, there were no significant differences between the two groups for r△LL, r△SS, relative intervertebral height, or upper and lower intervertebral heights.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e\u003cdiv class=\"gridtable\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\"±\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\"±\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e\u003ctable float=\"Yes\" id=\"Tab3\" border=\"1\"\u003e\u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 3\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003ePostoperative Lumbar Sagittal Parameter Correction\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e\u003ccolgroup cols=\"4\"\u003e\u003c/colgroup\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eVariable\u003c/p\u003e \u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eASD\u003c/p\u003e \u003cp\u003eGroup\u003c/p\u003e \u003c/th\u003e\u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eControl\u003c/p\u003e \u003cp\u003eGroup\u003c/p\u003e \u003c/th\u003e\u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eP value\u003c/p\u003e \u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eLL (°)\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\"±\" colname=\"c2\"\u003e \u003cp\u003e2.7 ± 52.6\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\"±\" colname=\"c3\"\u003e \u003cp\u003e16.3 ± 49.9\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.180\u003c/p\u003e \u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eSL (°)\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\"±\" colname=\"c2\"\u003e \u003cp\u003e24.0 ± 58.1\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\"±\" colname=\"c3\"\u003e \u003cp\u003e45.2 ± 120.6\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.007\u003c/p\u003e \u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eSS (°)\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\"±\" colname=\"c2\"\u003e \u003cp\u003e10.3 ± 28.7\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\"±\" colname=\"c3\"\u003e \u003cp\u003e25.1 ± 32.9\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.085\u003c/p\u003e \u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eRelative Intervertebral Disc Height (%)\u003c/p\u003e \u003cp\u003eRelative Intervertebral Disc Height of the Lower Level (%)\u003c/p\u003e \u003cp\u003eRelative Intervertebral Disc Height of the Upper Level (%)\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\"±\" colname=\"c2\"\u003e \u003cp\u003e2.6 ± 27.9\u003c/p\u003e \u003cp\u003e13.3 ± 30.4\u003c/p\u003e \u003cp\u003e19.8 ± 28.7\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\"±\" colname=\"c3\"\u003e \u003cp\u003e10.9 ± 27.8\u003c/p\u003e \u003cp\u003e12.6 ± 33.2\u003c/p\u003e \u003cp\u003e12.7 ± 23.2\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.264\u003c/p\u003e \u003cp\u003e0.932\u003c/p\u003e \u003cp\u003e0.095\u003c/p\u003e \u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/table\u003e\u003c/div\u003e \u003cp\u003e\u003c/p\u003e\n\u003ch3\u003e2.4 Multivariate logistic regression analysis\u003c/h3\u003e\n\u003cp\u003eVariables with statistically significant differences in the preoperative, postoperative, and relative correction values of the lumbar sagittal parameters were subjected to multivariate logistic regression analysis. As shown in Table\u0026nbsp;\u003cspan refid=\"Tab4\" class=\"InternalRef\"\u003e4\u003c/span\u003e, a smaller r△SL was identified as an independent risk factor for the occurrence of ASD (\u003cem\u003eP\u003c/em\u003e = 0.004, OR = 0.973, 95% confidence interval: 0.955–0.991). Receiver operating characteristic (ROC) curve analysis revealed that the area under the curve (AUC) for r△SL was 0.713 (95% confidence interval: 0.577–0.850). The optimal predictive threshold for r△SL was found to be 2.8%, where sensitivity and specificity were maximized (see Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e\u003cdiv class=\"gridtable\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e\u003ctable float=\"Yes\" id=\"Tab4\" border=\"1\"\u003e\u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 4\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eLogistic regression model with ASD as the dependent variable\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e\u003ccolgroup cols=\"3\"\u003e\u003c/colgroup\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eIndependent Variable\u003c/p\u003e \u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eP value\u003c/p\u003e \u003c/th\u003e\u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eOR (95% CI)\u003c/p\u003e \u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003ePostoperative LL\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e0.316\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0.959 (0.883–1.041)\u003c/p\u003e \u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003ePostoperative SS\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e0.082\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0.869 (0.742–1.018)\u003c/p\u003e \u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003er△SL\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e0.004\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0.973 (0.955–0.991)\u003c/p\u003e \u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/table\u003e\u003c/div\u003e"},{"header":"3. Discussion","content":"\u003cp\u003eIn recent years, spinal fusion surgery has become the standard procedure for treating degenerative lumbar spine diseases. Moreover, the incidence of long-term complications such as adjacent segment disease (ASD) has been steadily increasing. The 5-year revision surgery rate for ASD after lumbar fusion is 13.6%, and the 10-year rate reaches 22.2%. Therefore, to reduce the incidence of adjacent segment disease and alleviate the pain of secondary surgeries for patients, scholars worldwide have conducted extensive research on the risk factors for ASD, hoping to develop corresponding interventions to lower its incidence.\u003c/p\u003e\u003cp\u003eAn increasing number of studies have focused on the relationship between lumbar segmental lordosis (SL) and adjacent segment disease. This is promising because, postfusion, the height of the intervertebral disc of the fused segment is often reduced, and postoperative segmental lordosis may change. This alters the biomechanics of adjacent segments and even the entire lumbar spine, which plays a crucial role in the development of ASD. Currently, the measurement of lumbar segmental lordosis-related parameters is relatively standardized and mainly involves measuring lumbar lordosis (LL), segmental lordosis (SL), sacral slope (SS), and intervertebral disc height. Biomechanical studies have confirmed that a reduction in lumbar lordosis may accelerate the onset of adjacent segment disease \u003csup\u003e[\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e]\u003c/sup\u003e. Tsuang et al.\u003csup\u003e[\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e]\u003c/sup\u003e established finite element models with varying lordotic angles and reported that, in all the fusion models, the overall range of motion in the adjacent cranial segment increased. As the range of motion increased, the maximum von Mises stress on the intervertebral disc and the facet joint contact forces in the cranial adjacent segment also changed, which was similar to the results obtained by Zhao et al.\u003csup\u003e[\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e]\u003c/sup\u003e.\u003c/p\u003e\u003cp\u003e This study followed a strict 1:1 matching protocol, matching 27 ASD patients with 27 control patients on the basis of demographic parameters. The results revealed that, after the initial fusion surgery, the ASD group had significantly lower LL, SS, and relative intervertebral disc height than did the control group (\u003cem\u003eP\u003c/em\u003e \u0026lt; 0.05). Furthermore, when the postoperative correction values of the lumbar sagittal parameters were compared, the r△SL in the ASD group was significantly smaller than that in the control group (\u003cem\u003eP\u003c/em\u003e \u0026lt; 0.05), confirming that patients in the ASD group had insufficient local curvature correction. The multivariate logistic regression analysis indicated that r△SL is an independent risk factor for ASD, further emphasizing that inadequate local curvature correction increases the risk of postoperative ASD in patients undergoing spinal fusion. The optimal predictive threshold for r△SL in the occurrence of ASD was 2.8%.\u003c/p\u003e\u003cp\u003eSegmental lordosis (SL) reflects the curvature of the fused segment, which is mainly altered intraoperatively through the curvature of the fixation rods, making it a controllable factor for the surgeon. These findings have important clinical value for reducing the incidence of ASD. Numerous studies have shown that SL significantly impacts the efficacy of lumbar fusion surgery. Bae et al.\u003csup\u003e[\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e]\u003c/sup\u003e reported that restoring a normal SL is essential for preventing ASD. Nakashima et al.\u003csup\u003e[\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e]\u003c/sup\u003e conducted a follow-up study on 1,001 patients and reported that pelvic anteversion is a significant risk factor for adjacent segment disease, indicating that achieving proper lumbar lordosis during PLIF (posterior lumbar interbody fusion) is crucial for preventing ASD. Takahashi et al.\u003csup\u003e[\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e]\u003c/sup\u003e found that patients with larger ΔSLs had significantly higher Japanese Orthopedic Association (JOA) scores during follow-up, and their clinical outcomes were generally more satisfactory. Toivonen et al.\u003csup\u003e[\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e]\u003c/sup\u003e In a 10-year follow-up study, a higher LL outside the fused segment (LL - segmental lordosis) could reduce the risk of revision surgery due to ASD, which is consistent with our study, where the ASD group had significantly lower postoperative LL than did the control group.\u003c/p\u003e\u003cp\u003eEvery individual is unique, with variations in body function, lumbar spine curvature, and the ability to adapt to curvature. Therefore, preoperative SL or postoperative SL alone may not adequately reflect the relationship with adjacent segment disease. Similarly, the degree of influence of △SL on the original curvature varies among patients. Thus, on the basis of previous studies, we introduced the r△SL parameter in this study, which enhances the scientific credibility of the findings.\u003c/p\u003e\u003cp\u003eGong et al.\u003csup\u003e[\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e]\u003c/sup\u003e studied the occurrence of ASD following single-segment posterior fusion and identified preoperative MF muscle CSA (cross-sectional area) at L3–L4, as well as the FI (facet index) and BMD (bone mineral density) at L4–L5 and L5–S1, as significant risk factors for ASD. Wang et al. \u003csup\u003e[\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e]\u003c/sup\u003e followed up 189 PLF (posterior lumbar fusion) patients for at least 2 years and reported that the incidence of ASD increased with increasing postoperative time, the distance between the pedicle screw tip and the superior endplate decreased, and the sagittal angle between the pedicle screw and the superior endplate increased. Notably, when the distance was \u0026lt; 6.25 mm or the sagittal angle was \u0026gt; 5.5°, the risk of ASD increased. Bagheri et al. \u003csup\u003e[\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e]\u003c/sup\u003e retrospectively analyzed 630 patients who underwent posterior lumbar fusion and reported that preoperative BMI, preoperative disc degeneration, reduced postoperative lumbar lordosis, fusion of more than four segments, and intraoperative facet joint involvement increased the risk of ASD. Wang et al.\u003csup\u003e[\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e]\u003c/sup\u003e observed that patients with LL correction ≥ 10° and PI-LL correction ≥ 20° had a greater incidence of ASD in patients over 60, indicating that the ideal LL correction for older patients differs from that for younger patients because of the changes in lumbar lordosis with age.\u003c/p\u003e\u003cp\u003eThis study included only patients with adjacent segment disease following short-segment fusion surgeries at our center. Data analysis revealed no statistically significant difference in the incidence of ASD between fusion segments of two or fewer levels. This finding does not contradict the conclusion of Wang et al. \u003csup\u003e[\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e]\u003c/sup\u003e that long-segment fusion is a risk factor for adjacent segment disease.\u003c/p\u003e\u003cp\u003eThere are several limitations in this study. The sample size was small, and the time span was long, with only 27 cases of ASD. This limitation arose because preoperative, postoperative, and follow-up images could only be collected at our research center, restricting the sample size. There is an optimal range for lumbar curvature correction, but this study only provides the lower limit. Given the personalized characteristics of each patient's lumbar spine, further research with larger sample sizes, more detailed subgroup analyses, and the inclusion of other lumbar parameters is needed. Additionally, since the number of patients with single-segment and dual-segment ASDs in our center was similar, we did not analyze the distinct effects of single- versus dual-segment fusion on ASDs. The relative intervertebral disc height of dual-segment fusion was represented as the average of both segments, which may not be entirely appropriate and warrants further investigation.\u003c/p\u003e"},{"header":"4. Conclusion","content":"\u003cp\u003eThis study compared preoperative, postoperative, and follow-up lumbar sagittal parameters (LL, SL, SS, and relative intervertebral disc height) between the ASD and control groups. It was concluded that segmental lordosis is an important risk factor for ASD after lumbar posterior facet interbody fusion. Surgeons should focus on this issue during surgery and adjust the curvature of the fixation rods to achieve effective local curvature correction. Effective correction of the local curvature can significantly reduce the risk of ASD.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e \u003ch2\u003eEthics approval and consent to participate:\u003c/h2\u003e \u003cp\u003e All patients provided written informed consent prior to the study, which was conducted in accordance with the principles of the Declaration of Helsinki. Ethical approval was obtained from the Institutional Ethics Committee of the Second Affiliated Hospital of Harbin Medical University. Clinical trial registration: Not applicable.\u003c/p\u003e \u003c/p\u003e \u003cp\u003e \u003cstrong\u003eConsent for publication:\u003c/strong\u003e \u003cp\u003eNot applicable\u003c/p\u003e \u003c/p\u003e\u003cp\u003e \u003ch2\u003eCompeting interests:\u003c/h2\u003e \u003cp\u003eThe authors declare that they have no competing interests.\u003c/p\u003e \u003c/p\u003e\u003ch2\u003eAuthor Contribution\u003c/h2\u003e\u003cp\u003eHBQ performed the analysis and interpretation of patient data, and drafted the manuscript; HBQ and CYX designed the study; CYX performed the surgery; JLY and GXW collected the data; CH, XZ and PYK translated the manuscript. All authors read and approved the final manuscript.\u003c/p\u003e\u003ch2\u003eAvailability of data and materials:\u003c/h2\u003e \u003cp\u003eThe datasets used and/or analyzed during the current study are available from the corresponding author upon reasonable request.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003eZongjun M, Xiaoyin L, Jianqun Z, Peng W, Zhen C, Simin L, et al. Comparative Analysis of the Efficacy of Three Lumbar Fixation and Fusion Procedures in the Treatment of Adjacent Segment Disease after Lumbar Surgery. Chinese Journal of Spine and Spinal Cord. 2022;32(12):1102-11.\u003c/li\u003e\n\u003cli\u003eMobbs RJ, Phan K, Malham G, Seex K, Rao PJ. Lumbar interbody fusion: techniques, indications and comparison of interbody fusion options including PLIF, TLIF, MI-TLIF, OLIF/ATP, LLIF and ALIF. J Spine Surg. 2015;1(1):2-18.\u003c/li\u003e\n\u003cli\u003eXi C, Li Y, Chi Z, Pei L, Ji Y, Wang X, et al. The influence of orthotopic paraspinal muscle-pediculated bone flaps on posterior spinal fusion in a canine model. Spine (Phila Pa 1976). 2011;36(1):E20-6.\u003c/li\u003e\n\u003cli\u003eZhaoyang G, Hongli W, Xiaosheng M. Risk factors for adjacent segment disease after posterior L4/5 fusion surgery. Chinese Journal of Spine and Spinal Cord. 2023;33(04):337-43.\u003c/li\u003e\n\u003cli\u003eUmehara S, Zindrick MR, Patwardhan AG, Havey RM, Vrbos LA, Knight GW, et al. The biomechanical effect of postoperative hypolordosis in instrumented lumbar fusion on instrumented and adjacent spinal segments. Spine (Phila Pa 1976). 2000;25(13):1617-24.\u003c/li\u003e\n\u003cli\u003eTsuang FY, Tsai JC, Lai DM. Effect of lordosis on adjacent levels after lumbar interbody fusion, before and after removal of the spinal fixator: a finite element analysis. BMC Musculoskelet Disord. 2019;20(1):470.\u003c/li\u003e\n\u003cli\u003eZhao X, Du L, Xie Y, Zhao J. Effect of Lumbar Lordosis on the Adjacent Segment in Transforaminal Lumbar Interbody Fusion: A Finite Element Analysis. World Neurosurg. 2018;114:e114-e20.\u003c/li\u003e\n\u003cli\u003eBae JS, Lee SH, Kim JS, Jung B, Choi G. Adjacent segment degeneration after lumbar interbody fusion with percutaneous pedicle screw fixation for adult low-grade isthmic spondylolisthesis: minimum 3 years of follow-up. Neurosurgery. 2010;67(6):1600-7; discussion 7-8.\u003c/li\u003e\n\u003cli\u003eNakashima H, Kawakami N, Tsuji T, Ohara T, Suzuki Y, Saito T, et al. Adjacent Segment Disease After Posterior Lumbar Interbody Fusion: Based on Cases With a Minimum of 10 Years of Follow-up. Spine (Phila Pa 1976). 2015;40(14):E831-41.\u003c/li\u003e\n\u003cli\u003eTakahashi Y, Okuda S, Nagamoto Y, Matsumoto T, Sugiura T, Iwasaki M. Effect of segmental lordosis on the clinical outcomes of 2-level posterior lumbar interbody fusion for 2-level degenerative lumbar spondylolisthesis. J Neurosurg Spine. 2019;31(5):670-5.\u003c/li\u003e\n\u003cli\u003eToivonen LA, M\u0026auml;ntym\u0026auml;ki H, H\u0026auml;kkinen A, Kautiainen H, Neva MH. Postoperative Sagittal Balance Has Only a Limited Role in the Development of Adjacent Segment Disease After Lumbar Spine Fusion for Degenerative Lumbar Spine Disorders: A Subanalysis of the 10-year Follow-up Study. Spine (Phila Pa 1976). 2022;47(19):1357-61.\u003c/li\u003e\n\u003cli\u003eGong Z, Li D, Zou F, Liu S, Wang H, Ma X. Low lumbar multifidus muscle status and bone mineral density are important risk factors for adjacent segment disease after lumbar fusion: a case‒control study. J Orthop Surg Res. 2022;17(1):490.\u003c/li\u003e\n\u003cli\u003eWang Q, Gao Z, Guo K, Wang F, Wu D. Effect of sagittal screw angle and distance of screw apex to superior endplate on adjacent segment disease after posterolateral lumbar fusion: a retrospective study. J Orthop Surg Res. 2022;17(1):486.\u003c/li\u003e\n\u003cli\u003eBagheri SR, Alimohammadi E, Zamani Froushani A, Abdi A. Adjacent segment disease after posterior lumbar instrumentation surgery for degenerative disease: Incidence and risk factors. J Orthop Surg (Hong Kong). 2019;27(2):2309499019842378.\u003c/li\u003e\n\u003cli\u003eWang SJ, Zhang SB, Yi YY, Xu HW, Wu DS. Estimation of the ideal correction of lumbar lordosis to prevent reoperation for symptomatic adjacent segment disease after lumbar fusion in older people. BMC Musculoskelet Disord. 2020;21(1):429.\u003c/li\u003e\n\u003cli\u003eWang T, Ding W. Risk factors for adjacent segment degeneration after posterior lumbar fusion surgery in treatment for degenerative lumbar disorders: a meta-analysis. J Orthop Surg Res. 2020;15(1):582.\u003c/li\u003e\n\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":true,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true},"keywords":"Adjacent segment disease, Segmental lordosis, Spine, Posterior lumbar fusion","lastPublishedDoi":"10.21203/rs.3.rs-6201144/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-6201144/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003ch2\u003eObjective\u003c/h2\u003e \u003cp\u003eSegmental lordosis is an important risk factor for spinal diseases. The purpose of this study was to investigate the relationships between segmental lordosis-related parameters and adjacent segment disease (ASD) after lumbar interarticular fusion.\u003c/p\u003e\u003ch2\u003eMethods\u003c/h2\u003e \u003cp\u003eThis was a retrospective analysis of 27 patients with ASDs who underwent revision surgery in our hospital after lumbar interarticular fusion from February 2012 to February 2025. We included these 27 patients with ASD and matched them with 27 non-ASD controls on the basis of the initial surgery age, sex, surgical segment, and follow-up duration. Preoperative, postoperative, and final follow-up lumbar spine radiographs (anteroposterior and lateral radiographs) were analyzed. Parameters, including lumbar lordosis (LL), segmental lordosis (SL), sacral slope (SS), and the relative height of the intervertebral space adjacent to the fusion segment, were compared. Preoperative data, radiographic parameters at 3 days postsurgery, and final follow-up data were compared between the two groups. Significant parameters were further analyzed via multivariate logistic regression. The optimal predictive threshold for ASD was determined via receiver operating characteristic (ROC) curve analysis.\u003c/p\u003e\u003ch2\u003eResults\u003c/h2\u003e \u003cp\u003eNo significant differences in the general demographic data were found between the two groups (\u003cem\u003eP\u003c/em\u003e\u0026thinsp;\u0026gt;\u0026thinsp;0.05). Compared with the control group, the ASD group presented significantly lower postoperative lumbar LL, SS, and intervertebral space height (\u003cem\u003eP\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.05), along with a significantly reduced relative change in segmental lordosis (r△SL) during the early postoperative period (\u003cem\u003eP\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.05). Multivariate regression analysis confirmed that r△SL was an independent risk factor for ASD (\u003cem\u003eAUC\u003c/em\u003e\u0026thinsp;=\u0026thinsp;0.713, 95% \u003cem\u003eCI\u003c/em\u003e: 0.577\u0026ndash;0.850), with an optimal predictive threshold of 2.8%.\u003c/p\u003e\u003ch2\u003eConclusion\u003c/h2\u003e \u003cp\u003eInsufficient local curvature correction during fusion surgery accelerates degenerative changes in adjacent segments, and segmental lordosis is a critical risk factor for ASD.\u003c/p\u003e","manuscriptTitle":"Study of the Correlation between Adjacent Segment Disease and Segmental Lordosis After Lumbar Facet Joint Fusion Surgery","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-05-07 03:09:47","doi":"10.21203/rs.3.rs-6201144/v1","editorialEvents":[{"type":"communityComments","content":0}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"5fa6226d-59ab-407b-ae7a-97ad0e8fba4c","owner":[],"postedDate":"May 7th, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[],"tags":[],"updatedAt":"2025-05-30T10:38:30+00:00","versionOfRecord":[],"versionCreatedAt":"2025-05-07 03:09:47","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-6201144","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-6201144","identity":"rs-6201144","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}