Evaluation of a Novel Flexible Cage System for C5-C6 Fixation: A Finite Element Study Against Conventional ACDF Implants

Evaluation of a Novel Flexible Cage System for C5-C6 Fixation: A Finite Element Study Against Conventional ACDF Implants | 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 Article Evaluation of a Novel Flexible Cage System for C5-C6 Fixation: A Finite Element Study Against Conventional ACDF Implants Seongho Woo, Won Mo Koo, Kinam Park, Byung Joo Lee, Jong-Moon Hwang, and 1 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-7130831/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 Cervical spondylosis is a common cause of spinal cord dysfunction, and anterior cervical discectomy and fusion (ACDF) is widely employed when conservative treatment fails. Conventional implant systems such as the cervical cage with plate (CCP) and zero-profile stand-alone cage (ZPSC) are commonly used to enhance spinal stability and promote fusion, but they are associated with complications including dysphagia and adjacent segment degeneration 1 – 3 . To address these limitations, a novel flexible plate cage system (FPCS) has been developed to optimize biomechanical performance while minimizing surgical risk 4 . In this study, a finite element model of the C3–T1 cervical spine was constructed to simulate ACDF at the C5–C6 level using CCP, ZPSC, and FPCS implants. Under standardized loading conditions, von Mises stress was analyzed in the bone, intervertebral disc, endplates, cage, and screws, using the mean of the top 5% stress values to ensure accuracy 5 , 6 . All surgical models showed increased stress compared to the intact reference spine 7 – 9 . The ZPSC model exhibited the highest stress in the cage and screws, suggesting a more concentrated load path 10 . The CCP model showed a more evenly distributed stress profile, particularly affecting the inferior adjacent segment 11 , 12 . The FPCS model demonstrated moderate cage stress, reduced screw stress, and the highest plate stress, indicating a design that effectively redirects mechanical load toward the anterior plate while minimizing stress on critical bone structures 13 , 14 . This may be related to the FPCS’s unique structural configuration, which secures screws horizontally into the anterior vertebral body without penetrating the endplates 15 . These findings suggest that the FPCS may offer a biomechanically favorable alternative to existing ACDF implants 16 , 17 . Health sciences/Diseases Physical sciences/Engineering Health sciences/Medical research Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Introduction Cervical spondylosis is a major cause of spinal cord dysfunction. When non-surgical treatments fail, ACDF is widely regarded as the most effective surgical intervention 18 , 19 . CCP and ZPSC implants are commonly used in ACDF to prevent graft dislocation, improve sagittal alignment, and enhance fusion rates and stability 1 – 3 . However, these implants are associated with postoperative complications, such as dysphagia, adjacent segment degeneration, and soft tissue injury 20 , 21 , with most patients recovering within three months, but 3–21% experiencing chronic dysphagia 6 , 22 , 23 . To address these issues, FPCS has been developed 4 , 24 . FPCS aims to combine the advantages of existing implants while minimizing their drawbacks. Unlike CCP, FPCS focuses on enhancing stability and reducing surgical complications through a different structural approach, as well as contributing to reduced surgery time by considering its morphological characteristics 25 . Despite the potential benefits of FPCS, it requires thorough validation as it is newly developed. There are concerns regarding its biomechanical performance, particularly stress distribution on spinal components 26 . High stress concentrations may lead to complications such as subsidence, which can compromise the structural integrity of the spine and increase the need for reoperation 7 , 27 , 28 . Therefore, additional studies and clinical evaluations are needed to fully validate the efficacy of FPCS. In this study, a virtual model was created, and FEM was used to compare CCP, FPCS, and ZPSC, analyzing the von Mises stress applied to the bone, disc, endplate, cage, and screws. By understanding these stress distributions, we aim to identify the biomechanical advantages and potential drawbacks of FPCS, thereby guiding clinical decisions in ACDF surgeries 29 , 30 . Methods Development of the Finite Element Model A three-dimensional finite element method (FEM) analysis was conducted to investigate the effects on the third cervical (C3) to the first thoracic (T1) vertebrae under three conditions: surgery with a cervical pedicle screw (CCP) implant, surgery with a ZPSC implant, surgery with a FPCS implant, and a reference case (without surgery). The model included the C3-T1 vertebrae, encompassing both cortical and cancellous bones, as well as the intervertebral discs, which comprised the annulus fibrosus and nucleus pulposus. Additionally, the model incorporated the endplates, including both the upper and lower endplates, and the posterior elements, such as the pedicles, laminae, and facet joints. The cage system, illustrated in Fig. 1 , consisted of screws, plates, and artificial discs. The spine was modeled using data from previous studies and the finite element model has already been validated in an existing paper 1 , 8 , 31 . The cage system was positioned anteriorly, midway between the fifth (C5) and sixth (C6) cervical vertebrae. No patients were included as subjects in the study. ANSYS SpaceClaim software (SpaceClaim Corporation, Concord, MA, USA) was utilized to modify the three-dimensional (3D) models. Mesh and material properties for the FEM A finite element method (FEM) analysis was conducted using the ANSYS Workbench’s Static Structural module. Due to the anatomical irregularity of the model, a quadratic tetrahedron (10 nodes) was utilized for the mesh. The mesh size of the cage system was set to 0.7mm, while the mesh size of the remainder of the model was adjusted to 1mm prior to performing the structural analysis. In this study, we approximated the load generated when a person lowers their head and set elastic characteristics. Information regarding the mesh and material properties of the FEM analysis were assumed to be homogeneous and isotropic according to the published literature 1 , 4 , 5 , 32 and summarized in Table 1 . The cervical implant system consists of a plate, screws (bolts), and a cage. The plate and screws are made of titanium, while the cage is composed of polyetheretherketone (PEEK). Table 1 Mesh and material properties Component Number of nodes Number of elements Elastic modulus (MPa) Poisson ratio Reference Cortical bone 153,123 84,916 12,000 0.3 [3] Cancellous bone 42,536 23,743 100 0.2 [3] Posterior element 118,941 68,743 3,500 0.25 [3] Endplate 30,419 14,057 1,000 0.3 [4] Nucleus pulposus 10,396 5,356 1 0.499 [4] Annulus fibrosus 18,184 8,797 4.2 0.45 [4] Facet joint 3,286 1,197 11 0.4 [3] CCP Cage 18,471 10,310 3,600 (PEEK) 0.39 Plate 36,496 21,925 113,800 (Titanium) 0.342 [5] Screw 19,633 5,203 113,800 (Ti) 0.342 [5] ZPSC Cage 19,994 11,838 3,600 (PEEK) 0.39 Plate 10,574 6,133 113,800 (Ti) 0.342 [5] Screw 8,138 1,910 113,800 (Ti) 0.342 [5] FPSC Cage 28,833 16,912 3,600 (PEEK) 0.39 Plate 28,735 15,392 113,800 (Ti) 0.342 [5] Screw 14,785 4,900 113,800 (Ti) 0.342 [5] Loading and boundary conditions To investigate the effect of neck bending, a load was applied to the FEM model as illustrated in Fig. 3 . A vertical load of 73.6 N and a moment of 1.0 Nm were applied to the upper surface of the C3 cortical bone, while the lower surface of the T1 cortical bone was fixed in place. The bolt in the cage system made contact with the screw through bolt thread contact. For the normal plate system, an M4 X 0.7 (This indicates that the bolt thread diameter is 4 mm, while the pitch is 0.7 mm) bolt was used, whereas an M3 X 0.5 bolt was utilized for the FSC system. Due to the complexity of modeling variable contact conditions of human body components, it was assumed that the entire application surface was bonded together as a single unit. Results In this study, to ensure reliable evaluation and to avoid overestimation due to localized singularities, the von Mises stress was calculated as the mean of the top 5% highest values among all nodal stresses in the model. The representative von Mises stress on the cortical bone, cancellous bone, upper and lower endplates, intervertebral discs, cage, and screws was evaluated as the mean of the top 5% highest nodal stress values across four models: the reference model (no surgery), the CCP model (surgery with CCP implant), the ZPSC model (surgery with ZPSC implant), and the FPCS model (surgery with FPCS implant). Table 2 provides a summary of these values, including percentage variations relative to the reference model. Table 2 von Mises stress results at each structure in three different models. Component von Mises stress on each model (MPa) (% of von Mises stress with reference) Reference CCP ZPSC FPCS C4-5 Endplate upper 1.860 3.683 (198.01%) 3.937 (211.67%) 3.617 (194.46%) C4-5 Endplate lower 1.306 1.982 (151.76%) 2.091 (160.11%) 2.057 (157.53%)) C4-5 Annulus fibrosus 1.152 1.301 (112.89%) 1.370 (118.92%) 1.265 (109.81%) C4-5 Nucleus pulposus 9.321E-03 9.778E-03 (105.00%) 1.098E-02 (117.91%) 9.801E-03 (105.25%) C6-7 Endplate upper 0.864 2.696 (311.98%) 1.647 (190.63%) 2.379 (275.35%) C6-7 Endplate lower 0.755 1.143 (151.36%) 1.820 (241.06%) 1.839 (243.58%) C6-7 Annulus fibrosus 0.605 1.230 (203.34%) 1.207 (199.50%) 1.093 (180.71%) C6-7 Nucleus pulposus 3.807E-03 8.799E-03 (231.13%) 8.651E-03 (227.24%) 7.786E-03 (204.52%) C5 Cortical bone 2.303 3.797 (164.87%) 6.326 (274.69%) 2.585 (112.23%) C6 Cortical bone 2.064 2.515 (121.85%) 3.801 (184.16%) 2.836 (137.40%) C5 Cancellous bone 0.036 0.065 (178.68%) 0.194 (531.65%) 0.070 (192.00%) C6 Cancellous bone 0.051 0.063 (123.53%) 0.081 (158.82%) 0.074 (144.12%) Cage 3.171 5.440 4.745 Plate 10.375 14.880 16.071 Screw 3.276 16.548 5.085 Cortical and Cancellous Bone Stress Analysis at the ACDF on C5-C6 Segment The representative von Mises stress values (top 5% average) in the cortical and cancellous bones at the C5 and C6 levels were analyzed across all models. At C5 cortical bone, the von Mises stress increased from 2.303 MPa in the reference model to 3.797 MPa (164.87%) in the CCP model and 6.326 MPa (274.69%) in the ZPSC model. In contrast, the FPCS model showed a lower stress value of 2.585 MPa (112.23%) compared to the reference. For C6 cortical bone, stress increased from 2.064 MPa in the reference model to 2.515 MPa (121.85%) in the CCP model, 3.801 MPa (184.16%) in the ZPSC model, and 2.836 MPa (137.40%) in the FPCS model. All surgical models exhibited higher stresses than the reference. In the case of C5 cancellous bone, the von Mises stress rose from 0.036 MPa in the reference model to 0.065 MPa (178.68%) in the CCP model and 0.194 MPa (531.65%) in the ZPSC model. The FPCS model showed an intermediate increase to 0.070 MPa (192.00%). At C6 cancellous bone, the stress increased from 0.051 MPa in the reference model to 0.063 MPa (123.53%) in the CCP model, 0.081 MPa (158.82%) in the ZPSC model, and 0.074 MPa (144.12%) in the FPCS model. Stress Distribution in Adjacent Segments (C4-5 and C6-7) Following ACDF at C5-C6 The representative von Mises stress values for the C4–5 intervertebral disc was evaluated across four regions: the upper endplate, lower endplate, annulus fibrosus, and nucleus pulposus. In the reference model, stress values were 1.860, 1.306, 1.152, and 9.312E-03 MPa, respectively. The CCP model showed increased upper and lower endplate stress to 3.683 and 1.982 MPa, and elevated stresses in the annulus fibrosus and nucleus pulposus to 1.301 and 9.778E-03 MPa. The ZPSC model further increased the upper and lower endplate stresses to 3.937 and 2.091 MPa, with the annulus fibrosus and nucleus pulposus stresses measured at 1.370 and 1.098E-02 MPa. The FPCS model exhibited slightly lower upper and lower endplate stresses of 3.617 and 2.057 MPa, and the annulus fibrosus and nucleus pulposus stresses were 1.265 and 9.801E-03 MPa, respectively. At the C4–5 level, all surgical models showed increased stress values in all regions compared to the reference. The ZPSC model showed the highest stress in both the upper and lower endplates, as well as in the annulus fibrosus and nucleus pulposus at the C4–5 level. The CCP and FPCS models also exhibited increased stress in all regions, but to a lesser extent than ZPSC. A similar pattern was observed at the C6–7 level. The reference model stress values were 0.864, 0.755, 0.605, and 3.807E-03 MPa, respectively. The CCP model increased the upper and lower endplate stresses to 2.696 and 1.143 MPa, and the annulus fibrosus and nucleus pulposus stresses to 1.230 and 8.799E-03 MPa. The ZPSC model yielded upper and lower endplate stresses of 1.647 and 1.820 MPa, with annulus fibrosus and nucleus pulposus stresses at 1.207 and 8.651E-03 MPa. The FPCS model presented elevated upper and lower endplate stresses of 2.379 and 1.839 MPa, while annulus fibrosus and nucleus pulposus stresses were slightly lower at 1.093 and 7.786E-03 MPa. At the C6–7 level, all surgical models demonstrated increased stress compared to the reference, particularly in the endplates and annulus fibrosus. The CCP model exhibited the highest stress in the upper endplate, annulus fibrosus, and nucleus pulposus. The FPCS model showed the highest stress in the lower endplate. The ZPSC model presented intermediate stress values in all regions, reflecting a more balanced distribution compared to CCP and FPCS. These findings suggest that all implant models increase stress in adjacent segments compared to the reference, with ZPSC inducing the highest stress concentrations at the superior segment (C4–5), while CCP predominantly affects the inferior segment (C6–7). The FPCS model, although increasing stress overall, tended to produce relatively moderate stress values across most regions. Implant Stress Characteristics of CCP, ZPSC, and FPSC at the C5-C6 ACDF The representative von Mises stress values on the implants were analyzed to assess mechanical loading characteristics and potential stress concentration among the three surgical models. For the cage component, the ZPSC model exhibited the highest stress at 5.440 MPa, followed by the FPSC model at 4.745 MPa. The CCP model showed the lowest cage stress at 3.171 MPa, indicating that in this design, less load is transmitted through the cage. Regarding the screw component, the ZPSC model showed the highest stress at 16.548 MPa, followed by the FPCS model at 5.085 MPa, and the CCP model at 3.276 MPa. These results suggest that the ZPSC model may experience greater mechanical demand at the screw interface, which could influence long-term fatigue performance. For the plate component, the highest stress was observed in the FPCS model at 16.071 MPa, followed by ZPSC at 14.880 MPa, and CCP at 10.375 MPa. This indicates that the FPSC design transfers more load through the anterior plate, potentially providing better stability while reducing stress on the screw. Discussion This study aimed to evaluate the biomechanical performance of a novel FPCS in ACDF at the C5–C6 level, using FEA to compare it with two widely used systems: the CC) and the ZPSC. Von Mises stress distribution was analyzed in the vertebrae, intervertebral discs, endplates, and implant components to assess mechanical load transfer and potential clinical implications. All surgical models resulted in elevated stress levels in both the vertebral structures and adjacent segments compared to the intact reference model, consistent with the biomechanical consequences of fusion procedures. The ZPSC model showed the highest stress concentrations overall, particularly in the C5 vertebra, screw, and cage. This pattern suggests a concentrated load path and potentially increased risk for implant-related complications such as screw loosening or cage subsidence 9 , 10 . The rigid, compact design of ZPSC, which anchors screws obliquely through the vertebral endplate, may contribute to these high localized stresses, especially in adjacent levels where mobility is preserved. The CCP model demonstrated a more evenly distributed stress profile, with relatively lower stress in implant components. However, it induced notable stress increases at the C6–7 level, raising concerns regarding inferior adjacent segment degeneration. While CCP systems benefit from strong fixation and well-established clinical outcomes, their prominent anterior profile has been associated with soft tissue irritation and postoperative dysphagia 11 , 12 . The FPCS model also exhibited lower stress at C5-C6 bone stress, and a favorable balance in stress distribution. Notably, it showed moderate stress within the cage, low screw stress, and the highest stress in the anterior plate among all models 13 , 14 . These findings imply a biomechanical strategy in which the FPCS design intentionally redirects load-bearing from the screw-bone interface toward the anterior plate. This may reduce the risk of screw fatigue and improve long-term implant stability. Importantly, the structural characteristics of FPCS likely contribute to this performance. Unlike ZPSC, which fixes screws through the endplate, the FPSC anchors screws horizontally into the anterior portion of the vertebral body, avoiding direct penetration of the endplate and potentially reducing stress concentrations 15 , 16 . Additionally, by integrating both an anterior plate and a cage within a streamlined profile, FPCS attempts to combine the stability of CCP with the compactness of ZPSC, while minimizing their respective drawbacks 24 , 25 . In summary, the ZPSC model exhibited the highest implant stresses overall, particularly in the screw and cage, suggesting a more concentrated load path. The CCP model showed the most evenly distributed stress, with relatively low values across all components. The FPCS model demonstrated moderate cage stress, low screw stress, and the highest plate stress, suggesting a design optimized to shift loading toward the anterior plate while minimizing screw fatigue risk. The structural orientation and screw trajectory of the FPCS likely play a key role in achieving this biomechanical advantage. Although these results are promising, this study has several limitations. The boundary conditions and load applications were idealized, and material properties were simplified as homogeneous and isotropic. The model did not account for individual variations in anatomy, bone quality, or the biological process of fusion. Additionally, time-dependent factors such as fatigue, micromotion, and bone remodeling were not considered 8 , 31 , 32 . Further biomechanical validation through cadaveric testing and long-term clinical evaluation is necessary to confirm the effectiveness and safety of the FPCS system. Conclusion This finite element study demonstrates that the novel FPCS provides a biomechanically favorable profile for use in ACDF at the C5–C6 level. Compared to the conventional CCP and ZPSC systems, the FPCS offers a balanced stress distribution that potentially reduces the risk of complications such as screw loosening, adjacent segment degeneration, and implant fatigue. Its design—which includes a horizontally anchored screw trajectory and an anterior plate integrated with a cage—appears to effectively shift mechanical loads away from the screws toward the plate, enhancing overall stability while minimizing concentrated stress. These findings suggest that FPCS may represent a viable alternative to traditional ACDF implants, particularly in patients for whom minimizing implant-related complications is a priority. However, further experimental and clinical studies are needed to substantiate its long-term safety and effectiveness in real-world surgical settings. Declarations This work was supported by the National Research Foundation of Korea(NRF) grant funded by the Korea government(MSIT) (No. 2022R1F1A1066508) and a grant of the Korea Health Technology R&D Project through the Korea Health Industry Development Institute (KHIDI), funded by the Ministry of Health & Welfare, Republic of Korea (No. HR22C1832). All data generated or analysed during this study are included in this published article and its supplementary information files. Author Contribution These corresponding authors contributed equally: Sungwook Kang and Jong-Moon Hwang.S.K., J.M. planned the study, and performed processing of model analysis. S.W. wrote original draft preparation. W.K., K.P., and B.L. reviewed and edited the writing. S.K. and J.M. performed the data analysis. All authors have read and agreed to the published version of the manuscript. Acknowledgement This work was supported by the National Research Foundation of Korea(NRF) grant funded by the Korea government(MSIT) (No. 2022R1F1A1066508) and a grant of the Korea Health Technology R&D Project through the Korea Health Industry Development Institute (KHIDI), funded by the Ministry of Health & Welfare, Republic of Korea (No. HR22C1832). Data Availability All data generated or analyzed during this study are included in this published article and its supplementary information files. References Panjabi, M. M. Biomechanics of cervical spine stability and implant fixation. Spine 26 , E528–E535 (2001). Bartels, R. H. Comparison of cervical implants in discectomy and fusion. J. Neurosurg. Spine . 5 , 534–539 (2006). Shen, Y. & Zhang, D. W. Clinical outcomes of cervical fusion implants. World Neurosurg. 115 , e226–e232 (2018). Woo, S. H. & ;. Koo, K. J., W. M. Development of flexible plate cage system for cervical fusion. Biomed Eng Lett 14, 127–136 (2024). Lee, S. H. 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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-7130831","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Article","associatedPublications":[],"authors":[{"id":495428397,"identity":"b970ae2f-97b8-4112-b8e4-48c99acb18b3","order_by":0,"name":"Seongho Woo","email":"","orcid":"","institution":"Daegu Fatima Hospital","correspondingAuthor":false,"prefix":"","firstName":"Seongho","middleName":"","lastName":"Woo","suffix":""},{"id":495428398,"identity":"74b76a49-9ccb-4f60-a770-17e6c5caacf5","order_by":1,"name":"Won Mo Koo","email":"","orcid":"","institution":"Daegu Fatima Hospital","correspondingAuthor":false,"prefix":"","firstName":"Won","middleName":"Mo","lastName":"Koo","suffix":""},{"id":495428399,"identity":"3b045c86-2faa-454b-a1e2-94eb7894ae3a","order_by":2,"name":"Kinam Park","email":"","orcid":"","institution":"Daegu Fatima Hospital","correspondingAuthor":false,"prefix":"","firstName":"Kinam","middleName":"","lastName":"Park","suffix":""},{"id":495428400,"identity":"fbf47031-7c6b-4b9e-9fa7-e10b6bf2758c","order_by":3,"name":"Byung Joo Lee","email":"","orcid":"","institution":"Daegu Fatima Hospital","correspondingAuthor":false,"prefix":"","firstName":"Byung","middleName":"Joo","lastName":"Lee","suffix":""},{"id":495428401,"identity":"d3658c65-bf68-44b2-9957-c842aae2182e","order_by":4,"name":"Jong-Moon Hwang","email":"","orcid":"","institution":"Haengbokhan Rehabilitation Medicine Clinic","correspondingAuthor":false,"prefix":"","firstName":"Jong-Moon","middleName":"","lastName":"Hwang","suffix":""},{"id":495428402,"identity":"4d745e5a-2916-4c4e-a261-dcb481616f05","order_by":5,"name":"Sungwook Kang","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAA7UlEQVRIiWNgGAWjYFACNhBhw2CAJMRMjJY00rUcJkGL/Iy0xM8Fv87Lm7OfPfyap+IOA3/7AWbjCjxaDG6kHZae2XfbcGdPXpo1z5lnDBJnEpgTz+DTIp3eIM3bczvB4ECOmXFu22EGhhsMzAcb8Dlsdnrzb96ecwkG599AtMgT0sJwO+2YNM+PAwkGN3KMH4O0GAC1JOLTYnD/WZo1b0Oy4YYbb8yY/5w5zGN4JrHZEK/Deo4Z3+b5YydvcD7H+OOMisNycscPH5bE6zAQYGwDU2wSQIIHyCWoAQj+gEnmD0QoHQWjYBSMghEIALUBT+cO/dsBAAAAAElFTkSuQmCC","orcid":"","institution":"Changwon National University","correspondingAuthor":true,"prefix":"","firstName":"Sungwook","middleName":"","lastName":"Kang","suffix":""}],"badges":[],"createdAt":"2025-07-15 13:08:06","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-7130831/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-7130831/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":88490603,"identity":"527650bf-a78a-4b3f-8365-cb7dcc1f2272","added_by":"auto","created_at":"2025-08-07 04:12:44","extension":"jpg","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":50104,"visible":true,"origin":"","legend":"\u003cp\u003eAnalysis model; \u003cstrong\u003e(a)\u003c/strong\u003e Reference model, \u003cstrong\u003e(b)\u003c/strong\u003e CCP implant model, \u003cstrong\u003e(c)\u003c/strong\u003e ZPSC implant model, \u003cstrong\u003e(d) \u003c/strong\u003eFPCSimplant model \u003cstrong\u003e(e)\u003c/strong\u003e Section view of the CCP implant model\u003c/p\u003e","description":"","filename":"Picture1.jpg","url":"https://assets-eu.researchsquare.com/files/rs-7130831/v1/31984dd773727ccbb87ed02a.jpg"},{"id":88490602,"identity":"a682dc8f-d673-461d-8402-70285672c3f3","added_by":"auto","created_at":"2025-08-07 04:12:44","extension":"jpg","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":35314,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003e(a)\u003c/strong\u003e 3D models of FPCS implant, \u003cstrong\u003e(b)\u003c/strong\u003eExhibit mockup of FPCS implant\u003c/p\u003e","description":"","filename":"Picture2.jpg","url":"https://assets-eu.researchsquare.com/files/rs-7130831/v1/d86c4d0f029240d6df2c8111.jpg"},{"id":88492007,"identity":"65839b00-db59-43ff-a12c-7dfb19d756ca","added_by":"auto","created_at":"2025-08-07 04:28:44","extension":"jpg","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":54227,"visible":true,"origin":"","legend":"\u003cp\u003eGeometry boundary and loading condition; \u003cstrong\u003e(a)\u003c/strong\u003e Fixed support, \u003cstrong\u003e(b) \u003c/strong\u003eForce condition, \u003cstrong\u003e(c)\u003c/strong\u003e Moment condition\u003c/p\u003e","description":"","filename":"Picture3.jpg","url":"https://assets-eu.researchsquare.com/files/rs-7130831/v1/9e3f512d46a77ad9736a91ba.jpg"},{"id":88490609,"identity":"c287aefd-9a56-4c0e-afd2-3b4f7b18abbb","added_by":"auto","created_at":"2025-08-07 04:12:44","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":149376,"visible":true,"origin":"","legend":"\u003cp\u003eAnalysis result; \u003cstrong\u003e(a)\u003c/strong\u003e C4-C5 upper endplate, \u003cstrong\u003e(b)\u003c/strong\u003e C4-C5 lower endplate, \u003cstrong\u003e(c)\u003c/strong\u003e C4-C5 annulus fibrosus, \u003cstrong\u003e(d)\u003c/strong\u003e C4-C5 nucleus pulposus, \u003cstrong\u003e(e)\u003c/strong\u003e C6-C7 upper endplate, \u003cstrong\u003e(f)\u003c/strong\u003e C6-C7 lower endplate, \u003cstrong\u003e(g)\u003c/strong\u003eC6-C7 annulus fibrosus, \u003cstrong\u003e(h)\u003c/strong\u003e C6-C7 nucleus pulposus, \u003cstrong\u003e(i)\u003c/strong\u003e C5 cortical bone, \u003cstrong\u003e(j)\u003c/strong\u003e C6 cortical bone, \u003cstrong\u003e(k)\u003c/strong\u003e C5 cancellous bone, \u003cstrong\u003e(l)\u003c/strong\u003eC6 cancellous bone\u003c/p\u003e","description":"","filename":"4.png","url":"https://assets-eu.researchsquare.com/files/rs-7130831/v1/d2a7e9fc4de5da7922ddc788.png"},{"id":88491290,"identity":"0f2aab31-3aac-4488-bd06-51eeec17ed8e","added_by":"auto","created_at":"2025-08-07 04:20:44","extension":"jpg","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":29136,"visible":true,"origin":"","legend":"\u003cp\u003eAnalysis Result; \u003cstrong\u003e(a)\u003c/strong\u003e Cage, \u003cstrong\u003e(b)\u003c/strong\u003e Screw, \u003cstrong\u003e(c)\u003c/strong\u003ePlate\u003c/p\u003e","description":"","filename":"Picture5.jpg","url":"https://assets-eu.researchsquare.com/files/rs-7130831/v1/9b484bd2ffcd8f6f325f8866.jpg"},{"id":88490612,"identity":"c0e7670e-096c-44f1-b99f-e0ed5a21819b","added_by":"auto","created_at":"2025-08-07 04:12:44","extension":"jpg","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":216012,"visible":true,"origin":"","legend":"\u003cp\u003evon Mises stress results at each structure in three different models (Unit: MPa), \u003cstrong\u003e(a)\u003c/strong\u003e upper and lower endplate, \u003cstrong\u003e(b)\u003c/strong\u003e intervertebral disc, \u003cstrong\u003e(c)\u003c/strong\u003e cortical and cancellous bone.\u003c/p\u003e","description":"","filename":"6.jpg","url":"https://assets-eu.researchsquare.com/files/rs-7130831/v1/13963ed9c7918173d5be33a7.jpg"},{"id":88490607,"identity":"04f17eba-3cc6-4659-ae3b-b044fd990db2","added_by":"auto","created_at":"2025-08-07 04:12:44","extension":"jpg","order_by":7,"title":"Figure 7","display":"","copyAsset":false,"role":"figure","size":30207,"visible":true,"origin":"","legend":"\u003cp\u003evon Mises stress results at cage and screw in three different models (Unit: MPa).\u003c/p\u003e","description":"","filename":"7.jpg","url":"https://assets-eu.researchsquare.com/files/rs-7130831/v1/69aa0b88c3cd8c96bff80ea9.jpg"},{"id":90432333,"identity":"624ba757-209d-41c3-9d36-45a6d271cabc","added_by":"auto","created_at":"2025-09-02 15:53:52","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":1372498,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-7130831/v1/10a8e533-614a-40d4-bb53-1af90055abe0.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"Evaluation of a Novel Flexible Cage System for C5-C6 Fixation: A Finite Element Study Against Conventional ACDF Implants","fulltext":[{"header":"Introduction","content":"\u003cp\u003eCervical spondylosis is a major cause of spinal cord dysfunction. When non-surgical treatments fail, ACDF is widely regarded as the most effective surgical intervention\u003csup\u003e\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e,\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e\u003c/sup\u003e. CCP and ZPSC implants are commonly used in ACDF to prevent graft dislocation, improve sagittal alignment, and enhance fusion rates and stability\u003csup\u003e\u003cspan additionalcitationids=\"CR2\" citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e\u003c/sup\u003e. However, these implants are associated with postoperative complications, such as dysphagia, adjacent segment degeneration, and soft tissue injury\u003csup\u003e\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e,\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e\u003c/sup\u003e, with most patients recovering within three months, but 3\u0026ndash;21% experiencing chronic dysphagia\u003csup\u003e\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e,\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e,\u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e\u003cp\u003eTo address these issues, FPCS has been developed\u003csup\u003e\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e,\u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e\u003c/sup\u003e. FPCS aims to combine the advantages of existing implants while minimizing their drawbacks. Unlike CCP, FPCS focuses on enhancing stability and reducing surgical complications through a different structural approach, as well as contributing to reduced surgery time by considering its morphological characteristics\u003csup\u003e\u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e\u003cp\u003eDespite the potential benefits of FPCS, it requires thorough validation as it is newly developed. There are concerns regarding its biomechanical performance, particularly stress distribution on spinal components\u003csup\u003e\u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e\u003c/sup\u003e. High stress concentrations may lead to complications such as subsidence, which can compromise the structural integrity of the spine and increase the need for reoperation\u003csup\u003e\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e,\u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e,\u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e\u003c/sup\u003e. Therefore, additional studies and clinical evaluations are needed to fully validate the efficacy of FPCS.\u003c/p\u003e\u003cp\u003eIn this study, a virtual model was created, and FEM was used to compare CCP, FPCS, and ZPSC, analyzing the von Mises stress applied to the bone, disc, endplate, cage, and screws. By understanding these stress distributions, we aim to identify the biomechanical advantages and potential drawbacks of FPCS, thereby guiding clinical decisions in ACDF surgeries\u003csup\u003e\u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e29\u003c/span\u003e,\u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e30\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e"},{"header":"Methods","content":"\u003cp\u003e\u003cb\u003eDevelopment of the Finite Element Model\u003c/b\u003e\u003c/p\u003e\u003cp\u003eA three-dimensional finite element method (FEM) analysis was conducted to investigate the effects on the third cervical (C3) to the first thoracic (T1) vertebrae under three conditions: surgery with a cervical pedicle screw (CCP) implant, surgery with a ZPSC implant, surgery with a FPCS implant, and a reference case (without surgery). The model included the C3-T1 vertebrae, encompassing both cortical and cancellous bones, as well as the intervertebral discs, which comprised the annulus fibrosus and nucleus pulposus. Additionally, the model incorporated the endplates, including both the upper and lower endplates, and the posterior elements, such as the pedicles, laminae, and facet joints. The cage system, illustrated in Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e, consisted of screws, plates, and artificial discs. The spine was modeled using data from previous studies and the finite element model has already been validated in an existing paper\u003csup\u003e\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e,\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e,\u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e31\u003c/span\u003e\u003c/sup\u003e. The cage system was positioned anteriorly, midway between the fifth (C5) and sixth (C6) cervical vertebrae. No patients were included as subjects in the study. ANSYS SpaceClaim software (SpaceClaim Corporation, Concord, MA, USA) was utilized to modify the three-dimensional (3D) models.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003e\u003cb\u003eMesh and material properties for the FEM\u003c/b\u003e\u003c/p\u003e\u003cp\u003eA finite element method (FEM) analysis was conducted using the ANSYS Workbench\u0026rsquo;s Static Structural module. Due to the anatomical irregularity of the model, a quadratic tetrahedron (10 nodes) was utilized for the mesh. The mesh size of the cage system was set to 0.7mm, while the mesh size of the remainder of the model was adjusted to 1mm prior to performing the structural analysis. In this study, we approximated the load generated when a person lowers their head and set elastic characteristics. Information regarding the mesh and material properties of the FEM analysis were assumed to be homogeneous and isotropic according to the published literature\u003csup\u003e\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e,\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e,\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e,\u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e32\u003c/span\u003e\u003c/sup\u003e and summarized in Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e. The cervical implant system consists of a plate, screws (bolts), and a cage. The plate and screws are made of titanium, while the cage is composed of polyetheretherketone (PEEK).\u003c/p\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab1\" border=\"1\"\u003e\u003ccaption language=\"En\"\u003e\u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e\u003cdiv class=\"CaptionContent\"\u003e\u003cp\u003eMesh and material properties\u003c/p\u003e\u003c/div\u003e\u003c/caption\u003e\u003ccolgroup cols=\"7\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e\u003cdiv align=\"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\u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c7\" colnum=\"7\"\u003e\u003c/div\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colspan=\"2\" nameend=\"c2\" namest=\"c1\"\u003e\u003cp\u003eComponent\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c3\"\u003e\u003cp\u003eNumber of nodes\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c4\"\u003e\u003cp\u003eNumber of elements\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c5\"\u003e\u003cp\u003eElastic modulus (MPa)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c6\"\u003e\u003cp\u003ePoisson ratio\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c7\"\u003e\u003cp\u003eReference\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colspan=\"2\" nameend=\"c2\" namest=\"c1\"\u003e\u003cp\u003eCortical bone\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e153,123\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e84,916\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e12,000\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e0.3\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e[3]\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colspan=\"2\" nameend=\"c2\" namest=\"c1\"\u003e\u003cp\u003eCancellous bone\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e42,536\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e23,743\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e100\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e0.2\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e[3]\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colspan=\"2\" nameend=\"c2\" namest=\"c1\"\u003e\u003cp\u003ePosterior element\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e118,941\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e68,743\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e3,500\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e0.25\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e[3]\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colspan=\"2\" nameend=\"c2\" namest=\"c1\"\u003e\u003cp\u003eEndplate\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e30,419\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e14,057\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e1,000\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e0.3\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e[4]\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colspan=\"2\" nameend=\"c2\" namest=\"c1\"\u003e\u003cp\u003eNucleus pulposus\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e10,396\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e5,356\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e1\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e0.499\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e[4]\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colspan=\"2\" nameend=\"c2\" namest=\"c1\"\u003e\u003cp\u003eAnnulus fibrosus\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e18,184\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e8,797\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e4.2\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e0.45\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e[4]\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colspan=\"2\" nameend=\"c2\" namest=\"c1\"\u003e\u003cp\u003eFacet joint\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e3,286\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e1,197\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e11\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e0.4\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e[3]\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\" morerows=\"2\" rowspan=\"3\"\u003e\u003cp\u003eCCP\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eCage\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e18,471\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e10,310\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e3,600 (PEEK)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e0.39\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u0026nbsp;\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003ePlate\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e36,496\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e21,925\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e113,800 (Titanium)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e0.342\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e[5]\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eScrew\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e19,633\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e5,203\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e113,800 (Ti)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e0.342\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e[5]\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\" morerows=\"2\" rowspan=\"3\"\u003e\u003cp\u003eZPSC\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eCage\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e19,994\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e11,838\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e3,600 (PEEK)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e0.39\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u0026nbsp;\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003ePlate\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e10,574\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e6,133\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e113,800 (Ti)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e0.342\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e[5]\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eScrew\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e8,138\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e1,910\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e113,800 (Ti)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e0.342\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e[5]\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\" morerows=\"2\" rowspan=\"3\"\u003e\u003cp\u003eFPSC\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eCage\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e28,833\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e16,912\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e3,600 (PEEK)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e0.39\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u0026nbsp;\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003ePlate\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e28,735\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e15,392\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e113,800 (Ti)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e0.342\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e[5]\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eScrew\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e14,785\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e4,900\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e113,800 (Ti)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e0.342\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e[5]\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003cp\u003e\u003cb\u003eLoading and boundary conditions\u003c/b\u003e\u003c/p\u003e\u003cp\u003eTo investigate the effect of neck bending, a load was applied to the FEM model as illustrated in Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e. A vertical load of 73.6 N and a moment of 1.0 Nm were applied to the upper surface of the C3 cortical bone, while the lower surface of the T1 cortical bone was fixed in place. The bolt in the cage system made contact with the screw through bolt thread contact. For the normal plate system, an M4 X 0.7 (This indicates that the bolt thread diameter is 4 mm, while the pitch is 0.7 mm) bolt was used, whereas an M3 X 0.5 bolt was utilized for the FSC system. Due to the complexity of modeling variable contact conditions of human body components, it was assumed that the entire application surface was bonded together as a single unit.\u003c/p\u003e"},{"header":"Results","content":"\u003cp\u003eIn this study, to ensure reliable evaluation and to avoid overestimation due to localized singularities, the von Mises stress was calculated as the mean of the top 5% highest values among all nodal stresses in the model. The representative von Mises stress on the cortical bone, cancellous bone, upper and lower endplates, intervertebral discs, cage, and screws was evaluated as the mean of the top 5% highest nodal stress values across four models: the reference model (no surgery), the CCP model (surgery with CCP implant), the ZPSC model (surgery with ZPSC implant), and the FPCS model (surgery with FPCS implant). Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e provides a summary of these values, including percentage variations relative to the reference model.\u003c/p\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab2\" border=\"1\"\u003e\u003ccaption language=\"En\"\u003e\u003cdiv class=\"CaptionNumber\"\u003eTable 2\u003c/div\u003e\u003cdiv class=\"CaptionContent\"\u003e\u003cp\u003evon Mises stress results at each structure in three different models.\u003c/p\u003e\u003c/div\u003e\u003c/caption\u003e\u003ccolgroup cols=\"5\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\" morerows=\"1\" rowspan=\"2\"\u003e\u003cp\u003eComponent\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colspan=\"4\" nameend=\"c5\" namest=\"c2\"\u003e\u003cp\u003evon Mises stress on each model (MPa)\u003c/p\u003e\u003cp\u003e(% of von Mises stress with reference)\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u003cp\u003eReference\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c3\"\u003e\u003cp\u003eCCP\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c4\"\u003e\u003cp\u003eZPSC\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c5\"\u003e\u003cp\u003eFPCS\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eC4-5 Endplate upper\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e1.860\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e3.683 (198.01%)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e3.937 (211.67%)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e3.617 (194.46%)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eC4-5 Endplate lower\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e1.306\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e1.982 (151.76%)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e2.091 (160.11%)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e2.057 (157.53%))\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eC4-5 Annulus fibrosus\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e1.152\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e1.301 (112.89%)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e1.370 (118.92%)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e1.265 (109.81%)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eC4-5 Nucleus pulposus\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e9.321E-03\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e9.778E-03 (105.00%)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e1.098E-02 (117.91%)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e9.801E-03 (105.25%)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eC6-7 Endplate upper\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e0.864\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e2.696 (311.98%)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e1.647 (190.63%)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e2.379 (275.35%)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eC6-7 Endplate lower\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e0.755\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e1.143 (151.36%)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e1.820 (241.06%)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e1.839 (243.58%)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eC6-7 Annulus fibrosus\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e0.605\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e1.230 (203.34%)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e1.207 (199.50%)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e1.093 (180.71%)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eC6-7 Nucleus pulposus\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e3.807E-03\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e8.799E-03 (231.13%)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e8.651E-03 (227.24%)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e7.786E-03 (204.52%)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eC5 Cortical bone\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e2.303\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e3.797 (164.87%)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e6.326 (274.69%)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e2.585 (112.23%)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eC6 Cortical bone\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e2.064\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e2.515 (121.85%)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e3.801 (184.16%)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e2.836 (137.40%)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eC5 Cancellous bone\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e0.036\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e0.065 (178.68%)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e0.194 (531.65%)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e0.070 (192.00%)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eC6 Cancellous bone\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e0.051\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e0.063 (123.53%)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e0.081 (158.82%)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e0.074 (144.12%)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eCage\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e3.171\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e5.440\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e4.745\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003ePlate\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e10.375\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e14.880\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e16.071\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eScrew\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e3.276\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e16.548\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e5.085\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003cp\u003e\u003cb\u003eCortical and Cancellous Bone Stress Analysis at the ACDF on C5-C6 Segment\u003c/b\u003e\u003c/p\u003e\u003cp\u003eThe representative von Mises stress values (top 5% average) in the cortical and cancellous bones at the C5 and C6 levels were analyzed across all models.\u003c/p\u003e\u003cp\u003eAt C5 cortical bone, the von Mises stress increased from 2.303 MPa in the reference model to 3.797 MPa (164.87%) in the CCP model and 6.326 MPa (274.69%) in the ZPSC model. In contrast, the FPCS model showed a lower stress value of 2.585 MPa (112.23%) compared to the reference.\u003c/p\u003e\u003cp\u003eFor C6 cortical bone, stress increased from 2.064 MPa in the reference model to 2.515 MPa (121.85%) in the CCP model, 3.801 MPa (184.16%) in the ZPSC model, and 2.836 MPa (137.40%) in the FPCS model. All surgical models exhibited higher stresses than the reference.\u003c/p\u003e\u003cp\u003eIn the case of C5 cancellous bone, the von Mises stress rose from 0.036 MPa in the reference model to 0.065 MPa (178.68%) in the CCP model and 0.194 MPa (531.65%) in the ZPSC model. The FPCS model showed an intermediate increase to 0.070 MPa (192.00%).\u003c/p\u003e\u003cp\u003eAt C6 cancellous bone, the stress increased from 0.051 MPa in the reference model to 0.063 MPa (123.53%) in the CCP model, 0.081 MPa (158.82%) in the ZPSC model, and 0.074 MPa (144.12%) in the FPCS model.\u003c/p\u003e\u003cp\u003e\u003cb\u003eStress Distribution in Adjacent Segments (C4-5 and C6-7) Following ACDF at C5-C6\u003c/b\u003e\u003c/p\u003e\u003cp\u003eThe representative von Mises stress values for the C4\u0026ndash;5 intervertebral disc was evaluated across four regions: the upper endplate, lower endplate, annulus fibrosus, and nucleus pulposus. In the reference model, stress values were 1.860, 1.306, 1.152, and 9.312E-03 MPa, respectively. The CCP model showed increased upper and lower endplate stress to 3.683 and 1.982 MPa, and elevated stresses in the annulus fibrosus and nucleus pulposus to 1.301 and 9.778E-03 MPa. The ZPSC model further increased the upper and lower endplate stresses to 3.937 and 2.091 MPa, with the annulus fibrosus and nucleus pulposus stresses measured at 1.370 and 1.098E-02 MPa. The FPCS model exhibited slightly lower upper and lower endplate stresses of 3.617 and 2.057 MPa, and the annulus fibrosus and nucleus pulposus stresses were 1.265 and 9.801E-03 MPa, respectively. At the C4\u0026ndash;5 level, all surgical models showed increased stress values in all regions compared to the reference. The ZPSC model showed the highest stress in both the upper and lower endplates, as well as in the annulus fibrosus and nucleus pulposus at the C4\u0026ndash;5 level. The CCP and FPCS models also exhibited increased stress in all regions, but to a lesser extent than ZPSC.\u003c/p\u003e\u003cp\u003eA similar pattern was observed at the C6\u0026ndash;7 level. The reference model stress values were 0.864, 0.755, 0.605, and 3.807E-03 MPa, respectively. The CCP model increased the upper and lower endplate stresses to 2.696 and 1.143 MPa, and the annulus fibrosus and nucleus pulposus stresses to 1.230 and 8.799E-03 MPa. The ZPSC model yielded upper and lower endplate stresses of 1.647 and 1.820 MPa, with annulus fibrosus and nucleus pulposus stresses at 1.207 and 8.651E-03 MPa. The FPCS model presented elevated upper and lower endplate stresses of 2.379 and 1.839 MPa, while annulus fibrosus and nucleus pulposus stresses were slightly lower at 1.093 and 7.786E-03 MPa. At the C6\u0026ndash;7 level, all surgical models demonstrated increased stress compared to the reference, particularly in the endplates and annulus fibrosus. The CCP model exhibited the highest stress in the upper endplate, annulus fibrosus, and nucleus pulposus. The FPCS model showed the highest stress in the lower endplate. The ZPSC model presented intermediate stress values in all regions, reflecting a more balanced distribution compared to CCP and FPCS.\u003c/p\u003e\u003cp\u003eThese findings suggest that all implant models increase stress in adjacent segments compared to the reference, with ZPSC inducing the highest stress concentrations at the superior segment (C4\u0026ndash;5), while CCP predominantly affects the inferior segment (C6\u0026ndash;7). The FPCS model, although increasing stress overall, tended to produce relatively moderate stress values across most regions.\u003c/p\u003e\u003cp\u003e\u003cb\u003eImplant Stress Characteristics of CCP, ZPSC, and FPSC at the C5-C6 ACDF\u003c/b\u003e\u003c/p\u003e\u003cp\u003eThe representative von Mises stress values on the implants were analyzed to assess mechanical loading characteristics and potential stress concentration among the three surgical models. For the cage component, the ZPSC model exhibited the highest stress at 5.440 MPa, followed by the FPSC model at 4.745 MPa. The CCP model showed the lowest cage stress at 3.171 MPa, indicating that in this design, less load is transmitted through the cage.\u003c/p\u003e\u003cp\u003eRegarding the screw component, the ZPSC model showed the highest stress at 16.548 MPa, followed by the FPCS model at 5.085 MPa, and the CCP model at 3.276 MPa. These results suggest that the ZPSC model may experience greater mechanical demand at the screw interface, which could influence long-term fatigue performance.\u003c/p\u003e\u003cp\u003eFor the plate component, the highest stress was observed in the FPCS model at 16.071 MPa, followed by ZPSC at 14.880 MPa, and CCP at 10.375 MPa. This indicates that the FPSC design transfers more load through the anterior plate, potentially providing better stability while reducing stress on the screw.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003e\u003c/p\u003e"},{"header":"Discussion","content":"\u003cp\u003eThis study aimed to evaluate the biomechanical performance of a novel FPCS in ACDF at the C5\u0026ndash;C6 level, using FEA to compare it with two widely used systems: the CC) and the ZPSC. Von Mises stress distribution was analyzed in the vertebrae, intervertebral discs, endplates, and implant components to assess mechanical load transfer and potential clinical implications.\u003c/p\u003e\u003cp\u003eAll surgical models resulted in elevated stress levels in both the vertebral structures and adjacent segments compared to the intact reference model, consistent with the biomechanical consequences of fusion procedures. The ZPSC model showed the highest stress concentrations overall, particularly in the C5 vertebra, screw, and cage. This pattern suggests a concentrated load path and potentially increased risk for implant-related complications such as screw loosening or cage subsidence\u003csup\u003e\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e,\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e\u003c/sup\u003e. The rigid, compact design of ZPSC, which anchors screws obliquely through the vertebral endplate, may contribute to these high localized stresses, especially in adjacent levels where mobility is preserved.\u003c/p\u003e\u003cp\u003eThe CCP model demonstrated a more evenly distributed stress profile, with relatively lower stress in implant components. However, it induced notable stress increases at the C6\u0026ndash;7 level, raising concerns regarding inferior adjacent segment degeneration. While CCP systems benefit from strong fixation and well-established clinical outcomes, their prominent anterior profile has been associated with soft tissue irritation and postoperative dysphagia\u003csup\u003e\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e,\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e\u003cp\u003eThe FPCS model also exhibited lower stress at C5-C6 bone stress, and a favorable balance in stress distribution. Notably, it showed moderate stress within the cage, low screw stress, and the highest stress in the anterior plate among all models\u003csup\u003e\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e,\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e\u003c/sup\u003e. These findings imply a biomechanical strategy in which the FPCS design intentionally redirects load-bearing from the screw-bone interface toward the anterior plate. This may reduce the risk of screw fatigue and improve long-term implant stability. Importantly, the structural characteristics of FPCS likely contribute to this performance. Unlike ZPSC, which fixes screws through the endplate, the FPSC anchors screws horizontally into the anterior portion of the vertebral body, avoiding direct penetration of the endplate and potentially reducing stress concentrations\u003csup\u003e\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e,\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e\u003c/sup\u003e. Additionally, by integrating both an anterior plate and a cage within a streamlined profile, FPCS attempts to combine the stability of CCP with the compactness of ZPSC, while minimizing their respective drawbacks\u003csup\u003e\u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e,\u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e\u003cp\u003eIn summary, the ZPSC model exhibited the highest implant stresses overall, particularly in the screw and cage, suggesting a more concentrated load path. The CCP model showed the most evenly distributed stress, with relatively low values across all components. The FPCS model demonstrated moderate cage stress, low screw stress, and the highest plate stress, suggesting a design optimized to shift loading toward the anterior plate while minimizing screw fatigue risk. The structural orientation and screw trajectory of the FPCS likely play a key role in achieving this biomechanical advantage.\u003c/p\u003e\u003cp\u003eAlthough these results are promising, this study has several limitations. The boundary conditions and load applications were idealized, and material properties were simplified as homogeneous and isotropic. The model did not account for individual variations in anatomy, bone quality, or the biological process of fusion. Additionally, time-dependent factors such as fatigue, micromotion, and bone remodeling were not considered\u003csup\u003e\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e,\u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e31\u003c/span\u003e,\u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e32\u003c/span\u003e\u003c/sup\u003e. Further biomechanical validation through cadaveric testing and long-term clinical evaluation is necessary to confirm the effectiveness and safety of the FPCS system.\u003c/p\u003e"},{"header":"Conclusion","content":"\u003cp\u003eThis finite element study demonstrates that the novel FPCS provides a biomechanically favorable profile for use in ACDF at the C5\u0026ndash;C6 level. Compared to the conventional CCP and ZPSC systems, the FPCS offers a balanced stress distribution that potentially reduces the risk of complications such as screw loosening, adjacent segment degeneration, and implant fatigue. Its design\u0026mdash;which includes a horizontally anchored screw trajectory and an anterior plate integrated with a cage\u0026mdash;appears to effectively shift mechanical loads away from the screws toward the plate, enhancing overall stability while minimizing concentrated stress. These findings suggest that FPCS may represent a viable alternative to traditional ACDF implants, particularly in patients for whom minimizing implant-related complications is a priority. However, further experimental and clinical studies are needed to substantiate its long-term safety and effectiveness in real-world surgical settings.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003eThis work was supported by the National Research Foundation of Korea(NRF) grant funded by the Korea government(MSIT) (No. 2022R1F1A1066508) and a grant of the Korea Health Technology R\u0026amp;D Project through the Korea Health Industry Development Institute (KHIDI), funded by the Ministry of Health \u0026amp; Welfare, Republic of Korea (No. HR22C1832).\u003c/p\u003e\n\u003cp\u003eAll data generated or analysed during this study are included in this published article and its supplementary information files.\u003c/p\u003e\n\u003ch2\u003eAuthor Contribution\u003c/h2\u003e\n\u003cp\u003eThese corresponding authors contributed equally: Sungwook Kang and Jong-Moon Hwang.S.K., J.M. planned the study, and performed processing of model analysis. S.W. wrote original draft preparation. W.K., K.P., and B.L. reviewed and edited the writing. S.K. and J.M. performed the data analysis. All authors have read and agreed to the published version of the manuscript.\u003c/p\u003e\n\u003ch2\u003eAcknowledgement\u003c/h2\u003e\n\u003cp\u003eThis work was supported by the National Research Foundation of Korea(NRF) grant funded by the Korea government(MSIT) (No. 2022R1F1A1066508) and a grant of the Korea Health Technology R\u0026amp;D Project through the Korea Health Industry Development Institute (KHIDI), funded by the Ministry of Health \u0026amp; Welfare, Republic of Korea (No. HR22C1832).\u003c/p\u003e\n\u003ch2\u003eData Availability\u003c/h2\u003e\n\u003cp\u003eAll data generated or analyzed during this study are included in this published article and its supplementary information files.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003ePanjabi, M. M. Biomechanics of cervical spine stability and implant fixation. \u003cem\u003eSpine\u003c/em\u003e \u003cb\u003e26\u003c/b\u003e, E528\u0026ndash;E535 (2001).\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eBartels, R. H. Comparison of cervical implants in discectomy and fusion. \u003cem\u003eJ. Neurosurg. Spine\u003c/em\u003e. \u003cb\u003e5\u003c/b\u003e, 534\u0026ndash;539 (2006).\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eShen, Y. \u0026amp; Zhang, D. W. Clinical outcomes of cervical fusion implants. \u003cem\u003eWorld Neurosurg.\u003c/em\u003e \u003cb\u003e115\u003c/b\u003e, e226\u0026ndash;e232 (2018).\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eWoo, S. H. \u0026amp; ;. Koo, K. J., W. M. Development of flexible plate cage system for cervical fusion. Biomed Eng Lett 14, 127\u0026ndash;136 (2024).\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eLee, S. H. 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Spine J.\u003c/em\u003e \u003cb\u003e15\u003c/b\u003e, S338\u0026ndash;S347 (2006).\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003ePanjabi, M. M. Biomechanics of spinal segments. \u003cem\u003eJ. Biomech.\u003c/em\u003e \u003cb\u003e28\u003c/b\u003e, 1151\u0026ndash;1161 (1995).\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eLiu, Y. Recent advances in cervical implant biomechanics. \u003cem\u003eBMC Musculoskelet. Disord\u003c/em\u003e. \u003cb\u003e26\u003c/b\u003e, 112 (2025).\u003c/span\u003e\u003c/li\u003e\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":true,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true},"keywords":"","lastPublishedDoi":"10.21203/rs.3.rs-7130831/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-7130831/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eCervical spondylosis is a common cause of spinal cord dysfunction, and anterior cervical discectomy and fusion (ACDF) is widely employed when conservative treatment fails. Conventional implant systems such as the cervical cage with plate (CCP) and zero-profile stand-alone cage (ZPSC) are commonly used to enhance spinal stability and promote fusion, but they are associated with complications including dysphagia and adjacent segment degeneration\u003csup\u003e\u003cspan additionalcitationids=\"CR2\" citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e\u003c/sup\u003e. To address these limitations, a novel flexible plate cage system (FPCS) has been developed to optimize biomechanical performance while minimizing surgical risk\u003csup\u003e\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e\u003c/sup\u003e. In this study, a finite element model of the C3\u0026ndash;T1 cervical spine was constructed to simulate ACDF at the C5\u0026ndash;C6 level using CCP, ZPSC, and FPCS implants. Under standardized loading conditions, von Mises stress was analyzed in the bone, intervertebral disc, endplates, cage, and screws, using the mean of the top 5% stress values to ensure accuracy\u003csup\u003e\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e,\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e\u003c/sup\u003e. All surgical models showed increased stress compared to the intact reference spine\u003csup\u003e\u003cspan additionalcitationids=\"CR8\" citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e\u003c/sup\u003e. The ZPSC model exhibited the highest stress in the cage and screws, suggesting a more concentrated load path\u003csup\u003e\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e\u003c/sup\u003e. The CCP model showed a more evenly distributed stress profile, particularly affecting the inferior adjacent segment\u003csup\u003e\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e,\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e\u003c/sup\u003e. The FPCS model demonstrated moderate cage stress, reduced screw stress, and the highest plate stress, indicating a design that effectively redirects mechanical load toward the anterior plate while minimizing stress on critical bone structures\u003csup\u003e\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e,\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e\u003c/sup\u003e. This may be related to the FPCS\u0026rsquo;s unique structural configuration, which secures screws horizontally into the anterior vertebral body without penetrating the endplates\u003csup\u003e\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e\u003c/sup\u003e. These findings suggest that the FPCS may offer a biomechanically favorable alternative to existing ACDF implants\u003csup\u003e\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e,\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e","manuscriptTitle":"Evaluation of a Novel Flexible Cage System for C5-C6 Fixation: A Finite Element Study Against Conventional ACDF Implants","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-08-07 04:12:39","doi":"10.21203/rs.3.rs-7130831/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":"c0233df6-9b2a-43b8-9af4-3f3563da92c6","owner":[],"postedDate":"August 7th, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[{"id":52614658,"name":"Health sciences/Diseases"},{"id":52614659,"name":"Physical sciences/Engineering"},{"id":52614660,"name":"Health sciences/Medical research"}],"tags":[],"updatedAt":"2025-09-02T15:53:35+00:00","versionOfRecord":[],"versionCreatedAt":"2025-08-07 04:12:39","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-7130831","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-7130831","identity":"rs-7130831","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}