A Finite Element Analysis of the Optimal Longitudinal Screw Trajectory for Sanders II and Sanders III Calcaneal Fractures Fixed with Percutaneous Screws

A Finite Element Analysis of the Optimal Longitudinal Screw Trajectory for Sanders II and Sanders III Calcaneal Fractures Fixed with Percutaneous Screws | 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 A Finite Element Analysis of the Optimal Longitudinal Screw Trajectory for Sanders II and Sanders III Calcaneal Fractures Fixed with Percutaneous Screws Yang Peng, Gang Luo, Weidong Ni This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-5498977/v1 This work is licensed under a CC BY 4.0 License Status: Published Journal Publication published 03 Jul, 2025 Read the published version in BMC Surgery → Version 1 posted 11 You are reading this latest preprint version Abstract Background In recent years, percutaneous screw fixation technology has been extensively utilized in the management of displaced intra-articular calcaneal fractures. However, there remains a lack of consensus regarding the optimal design of screw trajectories to achieve maximal biomechanical strength. The objective of the present study was to identify the optimal screw trajectory for percutaneous screw fixation of calcaneal fractures through the application of finite element analysis. Methods The finite element analysis was used in this study. Six fracture models (Sanders IIA, B, C and IIIAB, AC, BC) were constructed according to the Sanders classification system. Based on the injury mechanism of calcaneal fractures, the anatomical characteristics of the calcaneus, and the results of preliminary experiments, four different screw fixation methods were designed to simulate the internal fixation of calcaneal fractures. Results In the six fracture models, the maximum stress on the calcaneal bone and the maximum displacement between the fracture blocks in the study group 1 and study group 2 were both less than those in control groups 1 and control groups 2. These differences were particularly significant in the II C, III AC, and III BC fracture models. In the II A fracture model, the screw stress in the study group 1 and study group 2 was higher than in control groups 1 and control groups 2. Conversely, in the II B and III AB fracture models, the differences in screw stress among the four fixation methods were minimal. In the II C, III AC, and III BC fracture models, the screw stress in the study group 1 and study group 2 was lower than that in control groups 1 and control groups 2. Notably, none of the screw stresses exceeded the threshold for internal fixation failure (600 mPa). Conclusion In the treatment of Sanders II and Sanders III calcaneal fractures with percutaneous screw fixation technique, the lateral longitudinal screw should be fixed from the calcaneal tubercle to the anterior process of the calcaneus, and the medial longitudinal screw should be fixed from the calcaneal tubercle along the medial wall to the calcaneal sustentaculum tali. This configuration is associated with optimal biomechanical stability. calcaneal fracture longitudinal screw finite element analysis sustentaculum tali Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 Figure 9 Figure 10 Figure 11 Figure 12 Introduction Calcaneal fractures represent one of the most frequent types of foot fractures, typically resulting from high-energy trauma, including traffic accidents and falls from significant heights [1, 2] . The calcaneus is a critical weight-bearing bone in the foot. The optimal treatment approach for calcaneal fractures remains a subject of debate [3−5] . In recent years, there has been a notable increase in the utilization of minimally invasive techniques within the field of orthopedics. Among these techniques, percutaneous screw fixation has gradually become an important method for treating calcaneal fractures due to its advantages of minimal trauma and rapid recovery, as evidenced by the literature [6−12] . Smerek et al., through cadaveric studies, demonstrated no significant difference in strength between screw fixation and plate fixation for Sanders II B calcaneal fractures [13] . Tornetta et al., in a retrospective analysis, found that percutaneous screw fixation was comparable to open reduction and internal fixation for Sanders IIC calcaneal fractures and, in some cases, superior [14] . The results of the latest meta-analysis indicate that screw fixation for calcaneal fractures provides comparable fixation strength and clinical efficacy to plate fixation, while offering shorter operating times and a lower incidence of incision-related complications [15] . Although the efficacy of screw fixation has been widely recognized by scholars, there is no consensus on the optimal screw trajectory to achieve maximum biomechanical strength. Current studies on the design of screw fixation trajectories have not fully taken into account the anatomical structure of the calcaneus and the injury mechanisms of calcaneal fractures. This study aims to explore the optimal longitudinal screw fixation trajectory using finite element analysis (FEA). Methods Software used for research : ( 1 ) Medical imaging software: Mimics 21.0 (Materialise Ltd, Belgium); ( 2 ) three-dimensional optimization software: Geomagic Wrap 2021 (Rainrrop Ltd, USA); ( 3 ) CAD software: SolidWorks 2022 (Dassault Systèmes Ltd, USA); ( 4 ) finite element analysis software: ANSYS Workbench 2022 R1 (ANSYS Ltd, USA). Finite Element Modeling Process : The CT data of a healthy subject (gender: male, age: 54 years old, height: 64 kg, weight: 165 cm, CT layer thickness: 0.6 mm) was processed using Mimics 21.0 software to extract the three-dimensional structure of the calcaneus. The reconstructed calcaneal model was imported into Geomagic Wrap 2021, and the model was smoothed to remove noise and irregularities to ensure the accuracy of the model. The software's function was utilized to define the cortical bone as the outer 2 mm layer, with the remaining internal region designated as cancellous bone (Fig. 1 ). The CAD file obtained in Geomagic Wrap 2021 was imported into Solid Works 2022 to create a model of the calcaneal fracture and simulate percutaneous screw fixation. According to the Sanders classification, we designed six fracture models in SolidWorks 2022, including Sanders IIA, IIB, IIC, and Sanders IIIAB, IIIAC, IIIBC (Fig. 2 ) [16, 17] . Based on the Essex-Lopresti classification, all these fractures were of the joint depression type. Mesh validation Appropriate mesh division helps improve the accuracy of experimental results and reduce computational costs. In the ANSYS Workbench 2022 R1 software, we conducted stress analyses using mesh sizes of 1.75 mm, 1.5 mm, 1.25 mm, and 1 mm, respectively. As the mesh resolution increased, the changes in the results became progressively smaller, indicating that the mesh was sufficiently refined. Ultimately, we determined the optimal mesh size to be 1 mm. Material properties and contact settings Based on previous studies on finite element analysis of the calcaneus, the contact between screws and fracture fragments was defined as bonded, while the friction coefficient between fracture fragments was set to 0.2. The materials in the model were simplified as homogeneous elastic materials, and their properties are listed in Table 2 . Load and boundary conditions During the analysis, the loading conditions of the calcaneus during normal standing were simulated. The cuboid articular surface and the posterior tuberosity of the calcaneus, which are in contact with the ground, were set as fixed supports. Forces of 420 N and 200 N were applied to the posterior talar articular facet and the middle talar articular facet, respectively (Fig. 4 ) [18, 19] . Table 1 The effect of different mesh sizes on the maximum stress of the calcaneus. Mesh sizes(mm) Number of Elements Number of Nodes Maximum Stress of Calcaneus(MPa) Changes in stress(%) 1.75 56573 99673 14.501 - 1.5 78729 137210 15.495 6.85 1.25 109007 191487 16.051 3.59 1 162984 287319 16.324 1.7 Table 2 Material properties in the finite element analysis Materials Young's modulus (MPa) Poisson's ratio Screw 200000 0.28 Cortical bone 7300 0.3 Cancellous bone 100 0.3 Pre-experiment In order to make our screw design more scientific, a pre-experiment was conducted before the start of the experiment to analyze the stress distribution of the calcaneus during standing in normal subjects. As mentioned above, the calcaneocuboid joint surface and the contact points between the posterior calcaneal tubercle and the ground were fixed, and forces of 420N and 200N were applied to the posterior subtalar joint surface and the middle subtalar joint surface, respectively, to simulate the force on the calcaneus during normal walking(Fig. 3 ). The calculation showed that the stress was mainly concentrated on the anterior medial side of the calcaneus (Fig. 4 ). Experimental design Based on the injury mechanism of calcaneal fractures, anatomical structure, and our preliminary experimental results, we believe that a medial longitudinal screw fixed from the calcaneal tuberosity to the sustentaculum tali can provide better stability. Therefore, we designed two different screw trajectories, referred to as the study group and the control group. In both groups, we used two 3.5 mm cannulated screws (transverse screws) and two 5.5 mm cannulated screws (longitudinal screws). The two 3.5 mm cannulated screws were fixed from the calcaneal tuberosity to the sustentaculum tali to stabilize the articular fracture fragments, and the spatial positions of these screws were kept absolutely consistent across all four groups. The main difference between the study group and the control group lies in the fixation paths of the two longitudinal screws. In the study group, the medial longitudinal screw was fixed from the calcaneal tuberosity to the sustentaculum tali, while in the control group, both longitudinal screws were fixed from the calcaneal tuberosity to the anterior process of the calcaneus. To avoid the influence of screw insertion angles on the results, we further refined the design of the study group and the control group. The study group was subdivided into Study Group 1 and Study Group 2, with the difference being that the two longitudinal screws in Study Group 1 were inserted in a non-crossed manner (Fig. 6 a, e), while those in Study Group 2 were inserted in a crossed manner (Fig. 6 b, f). Similarly, the control group was subdivided into Control Group 1 and Control Group 2, where the two longitudinal screws in Control Group 1 were inserted parallelly into the anterior process of the calcaneus (Figs. 6 c ,g), and those in Control Group 2 were inserted in a crossed manner from the calcaneal tuberosity (Figs. 6 d ,h). Results Maximum von Mises equivalent stress on bone Figure 7 illustrates the maximum stress distribution on the bone across the six fracture models. The maximum stress on the bone in the study groups was observed to be lower than that in control groups. This indicates that fixing the medial longitudinal screw from the calcaneal tubercle to the sustentaculum tali can facilitate a more uniform dispersion of the stress on the calcaneal cortical bone. Moreover, no significant difference was observed in the maximum stress on the bone between the study group 1 and 2, indicating that the crossing of the two longitudinal screws has a minimal impact on the stress distribution on the bone. Table 3 Maximum stress of the calcaneus (MPa). Sanders classification Study group 1 Study group 2 Control group1 Control group2 ⅡA 29.189 28.93 30.975 31.574 ⅡB 33.485 33.714 38.84 38.599 ⅡC 39.385 38.884 46.429 46.669 ⅢAB 34.212 37.105 39.401 39.396 ⅢAC 39.63 39.676 49.386 48.564 ⅢBC 40.865 40.972 51.265 50.141 Maximum von Mises equivalent stress on the screw The maximum screw stress reflects, to some extent, the degree of stress dispersion. Lower maximum screw stress corresponds to a reduced risk of internal fixation failure. The maximum screw stress for the six fracture models is presented in Fig. 7 . In the Ⅱ A fracture model, the screw stress in the study group was higher than in control groups. For the Ⅱ B and Ⅲ AB fracture models, no significant differences in screw stress were observed across the four groups. However, in the II C, III AC, and III BC fracture models, the screw stress in the study groups was lower than in control groups. This finding suggests that, in these three fracture models, securing the medial longitudinal screw to the sustentaculum tali reduces the maximum screw stress, thereby decreasing the risk of internal fixation failure. Additionally, no significant difference in maximum screw stress was observed between the study group 1 and 2, indicating that whether the two longitudinal screws cross has minimal impact on the maximum screw stress distribution. Across all six fracture models, the maximum stress of the medial longitudinal screw in the study group exceeded that in control groups (Fig. 8 ). This observation indicates that a medial longitudinal screw fixed to the sustentaculum tali bears more stress and achieves better biomechanical performance. According to previous studies, implant stress exceeding 600 MPa may pose a risk of internal fixation failure [20] . In this study, the stress on all screws remained below this threshold, indicating acceptable biomechanical safety. Table 4 Maximum stress of the screws (MPa). Sanders classification Study group 1 Study group 2 Control group1 Control group2 ⅡA 77.147 76.602 48.067 46.327 ⅡB 99.838 100.61 95.01 89.943 ⅡC 129.08 125.48 177.11 158.65 ⅢAB 116.33 119.53 116.27 110.27 ⅢAC 133.35 133.61 174.05 155.44 ⅢBC 157.97 162.95 225.17 210.97 Maximum displacement of the fracture fragment In the fracture model, the optimal internal fixation effect is achieved when the displacement of the fracture block is minimized. Figure 9 illustrates the maximum displacement of the fracture fragment in the six fracture models. The displacement of the fracture fragment in the study groups was found to be smaller than that observed in control groups. This difference was particularly evident in the II C, III AC, and III BC fracture models. Additionally, no significant difference was noted in the maximum displacement of the fracture block between the study group 1 and 2, suggesting that the crossing or non-crossing of the two longitudinal screws had a minimal impact on the maximum displacement of the fracture fragment. Figure 10 shows the displacement cloud map between fracture fragments, with the maximum displacement located near the primary fracture line. Table 5 Maximum displacement between fracture fragments (mm). Sanders classification Study group 1 Study group 2 Control group1 Control group2 ⅡA 0.15162 0.14991 0.16893 0.17622 ⅡB 0.27041 0.28076 0.32645 0.3107 ⅡC 0.31389 0.34582 0.4633 0.46981 ⅢAB 0.28799 0.31582 0.34591 0.33986 ⅢAC 0.35168 0.35695 0.50198 0.48265 ⅢBC 0.40016 0.39689 0.56833 0.54094 Discussion Percutaneous screw fixation has gained prominence as a method of fixation in the treatment of calcaneal fractures, concurrent with the increasing utilization of closed reduction techniques in clinical practice [11, 21−23] . The biomechanical stability of screw fixation has also emerged as a prominent area of investigation in the management of calcaneal fractures. A substantial body of clinical evidence substantiates the assertion that screw-only osteosynthesis can achieve comparable fixation strength and stability to that of plate fixation [6−8, 11, 12, 24] . Previous finite element analysis has also corroborated that the displacement of the fracture block is analogous between simple screw fixation and locking plate fixation. Both fixation methods have been demonstrated to provide sufficient stability in the treatment of calcaneal fractures [24] . It is important to note, however, that while the aforementioned studies confirm the effectiveness of simple screw fixation, the screw paths utilized in each study are distinct. This indicates that there is currently no consensus regarding the optimal method for fixing calcaneal fractures with simple screw fixation. Finite element analysis is used in the biomechanical study of internal fixation of fractures because of its ability to simulate complex shapes, loads and material properties with high accuracy and speed [25] . Studies have shown that the use of finite element analysis for the biomechanical study of fracture internal fixation devices can achieve the same validation effect as in vitro cadaver experiments [24] . We used finite element analysis to study the stability of different screw fixation methods. When designing the screw fixation method, we did not study the fixation stability by increasing or decreasing the number of screws, but by designing different screw fixation paths to study the stability of different screw fixation methods. The theoretical basis for the design of the screw trajectory is the injury mechanism of calcaneal fracture, the anatomical morphology of the calcaneus, and the results of our preliminary experiments, so as to maximize the scientific and rational design of the screw trajectory. In the process of calcaneal fracture formation, the violence is transmitted from the talus to the calcaneus through the middle and posterior subtalar articular surfaces, and the calcaneus forms a primary fracture line under shearing force, dividing the calcaneus into two main fracture blocks: the anterior medial and the posterior lateral. if the fracture involves an anteromedial and a posterolateral fragment, a sagittal fracture line may be observed, further complicating the fracture pattern. The findings of our preliminary experiments align with this hypothesis. In a normal standing position, the majority of the stress is concentrated on the anterior medial side of the calcaneus, specifically the anterior process of the calcaneus, the calcaneal groove, the posterior subtalar articular surfaces, the sustentaculum tali, and the medial wall. Depending on the orientation of the secondary fracture line, two main types of fractures can be distinguished: tongue-type fractures and joint depression-type fractures. In tongue-type fractures, the secondary fracture line extends posteriorly, creating a large posterior superior fragment. In joint depression-type fractures, the secondary fracture line results in a depressed fragment of the posterior facet [26, 27] . Zwipp subdivides the calcaneal fracture block into five distinct regions based on the computed tomography (CT) manifestations observed in calcaneal fractures. These include the calcaneal tubercle fracture block, the calcaneal sustentaculum tali fracture block, the calcaneal posterior subtalar joint fracture block, the calcaneal anterior tubercle fracture block, and the calcaneal anterior subtalar joint fracture block [28] . The calcaneal tubercle fracture block is the key fracture block that causes changes in the shape of the calcaneus, and its displacement largely affects the shape of the calcaneus (height, width, length, and varus/valgus). Therefore, the key to maintaining the shape of the calcaneus using simple screw fixation is how to stabilize the calcaneal tubercle fracture block, that is, how to connect the calcaneal tubercle fracture block with the remaining four main fracture blocks into a whole through a reasonable screw trajectory. In this study, we designed four screw trajectories for fixing the calcaneal tubercle fracture block with the remaining four main fracture blocks. The results showed that the longitudinal screw trajectory in the study group and control group 1 could disperse the stress on the bone and screws more evenly and reduce the displacement of the fracture block. This suggests that the optimal trajectory for the medial longitudinal screw may be from the calcaneal tubercle along the medial wall of the calcaneus to the sustentaculum tali. The screw should be more inclined towards the medial side of the calcaneus rather than the anterior side. In the Sanders II C, Sanders III AC, and Sanders III BC fracture models, the screw trajectories of the study group and control group 1 not only disperse the stress on the implant but also significantly reduce the displacement of the sustentaculum tali fracture block. However, in the Ⅱ A, Ⅱ B, and Ⅲ AB fracture models, although the screw direction of the study group can also reduce the displacement of the fracture block, the difference is not as obvious as in the Sanders II C and Sanders III AC, Ⅲ BC fracture models. We believe that this may be closely related to the difference in the course of the primary fracture line, which also affects the size of the formed sustentaculum tali fracture block. The closer the primary fracture line is to the calcaneal groove, the smaller the formed sustentaculum tali fracture block will be. When the sustentaculum tali fracture block is large, fixing the longitudinal screw to the anterior process of the calcaneus can also play a certain stabilizing role, but when the sustentaculum tali fracture fragment is small, the longitudinal screw needs to be fixed to the sustentaculum tali to fix the sustentaculum tali fracture fragment (Fig. 11 ). For Sanders II C and Sanders III AC, BC fracture models, since the sustentaculum tali fracture block is relatively small, if the longitudinal screw does not directly go to the sustentaculum tali, it will not provide the best fixation strength. Therefore, in the three fracture models, the control group 2 and 3 models show more obvious fracture block displacement. This result shows that for the three calcaneal fractures, when using screw fixation, a longitudinal screw from the calcaneal tubercle to the sustentaculum tali is necessary in order to more securely fix the sustentaculum tali fracture block. Furthermore, the anatomical characteristics of the calcaneus indicate that the medial longitudinal screw provides superior biomechanical strength by traversing from the calcaneal tubercle along the medial wall of the calcaneus to the sustentaculum tali. The calcaneal tubercle, the calcaneal sustentaculum tali and the calcaneal anterior process are the areas where the trabeculae of the calcaneus converge. These areas have denser and stronger bone, which provides an excellent anatomical basis for screw fixation. In addition, the calcaneal sustentaculum tali, together with the medial wall of the calcaneus, forms a strong medial load-bearing column. The sustentaculum talus is connected to the tibia and talus by the deltoid ligament and the interosseous ligament, respectively. The strength of both bundles of ligaments provides a robust stabilizing effect on the sustentaculum fracture fragment [29, 30] . Therefore, fixing the calcaneal tubercle fracture block to the sustentaculum tali also increases the fixation strength of the calcaneal tubercle fracture block to a certain extent. In this study, we did not investigate the optimal screw configuration and direction of the joint surface screws because the use of screws pointing from the thalamic portion to the tuberosity of the sustentaculum tali (sustentaculum tali screws) to fix the articular surface fracture block has been widely used in clinical practice. A large amount of literature confirms that the use of only the sustentaculum tali screw to fix the articular surface fracture block can achieve satisfactory fixation strength and therapeutic effects [31−33] . When using steel plates for fixation, the additional use of sustentaculum tali screws can disperse the stress of the internal fixation model [18] . Innovation and Deficiency The innovation of our research lies in the fact that the longitudinal screw trajectory was designed taking into account the anatomy of the calcaneus and the injury mechanism of calcaneal fractures. In addition, we conducted a pre-experiment to simulate the stress distribution inside the calcaneus during standing in a normal person, which made our screw design more scientific and reasonable. However, the model we constructed is only a relatively simple calcaneal model, and the internal part of the calcaneus is considered homogeneous for stress analysis, ignoring the uneven distribution of trabeculae within the calcaneus and the biomechanical effects of the tendons around the calcaneus on the calcaneus. Our internal fixation model is an idealized representation. In clinical practice, achieving complete anatomical reduction and addressing bone defects formed during calcaneal fractures are highly challenging, and these real-world factors, which were not considered in this study, can significantly affect the biomechanical performance of internal fixation. Therefore, this study can only provide a theoretical basis for the design of screw trajectories in clinical settings, and further validation through cadaveric experiments or clinical studies is necessary to confirm the effectiveness of the results. Additionally, due to the complexity of calcaneal fractures, we only designed models for joint depression-type fractures. Thus, the screw models proposed in this study may not be applicable to all types of calcaneal fracture patterns. Conclusion When treating Sanders II and Sanders III calcaneal fractures with percutaneous screw fixation, the medial longitudinal screw is fixed from the calcaneal tubercle along the medial wall to the sustentaculum tali, and the lateral longitudinal screw is fixed from the calcaneal tubercle to the anterior process of the calcaneus, providing optimal biomechanical fixation strength. Declarations Ethics approval and consent to participate The healthy subject agreed to participate in this clinical trial by signing an informed consent form. The study was approved by the Ethical Board Review of the First Affiliated Hospital of Chongqing Medical University and was performed in accordance with the ethical standards of the Declaration of Helsinki of 1964. Consent for publication Not applicable. Availability of data and materials Data is provided within the manuscript and related files Competing interests The authors declare no competing interests. Funding None. Author contributions Gang Luo and Yang Peng initiated the study design. Yang Peng is the principal investigator. Yang Peng constructed the finite element model and performed the finite element analysis. Weidong Ni substantially revised the manuscript. All authors read and approved the final manuscript. Acknowledgements We would like to thank everyone who helped us with this study References Potter MQ, Nunley JA. Long-term functional outcomes after operative treatment for intra-articular fractures of the calcaneus. J Bone Joint Surg Am. 2009;91(8):1854–60. Snoap T, Jaykel M, Williams C, et al. Calcaneus Fractures: A Possible Musculoskeletal Emergency. J Emerg Med. 2017;52(1):28–33. Li M, Lian X, Yang W et al. Percutaneous Reduction and Hollow Screw Fixation Versus Open Reduction and Internal Fixation for Treating Displaced Intra-Articular Calcaneal Fractures. Med Sci Monit, 2020. 26: p. e926833.e926833. Radnay CS, Clare MP, Sanders RW. 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Cite Share Download PDF Status: Published Journal Publication published 03 Jul, 2025 Read the published version in BMC Surgery → Version 1 posted Editorial decision: Revision requested 23 Apr, 2025 Editor assigned by journal 23 Apr, 2025 Reviews received at journal 20 Apr, 2025 Reviewers agreed at journal 20 Apr, 2025 Reviews received at journal 18 Apr, 2025 Reviewers agreed at journal 16 Apr, 2025 Reviewers agreed at journal 15 Apr, 2025 Reviewers agreed at journal 15 Apr, 2025 Reviewers invited by journal 15 Apr, 2025 Submission checks completed at journal 25 Mar, 2025 First submitted to journal 23 Mar, 2025 You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. 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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-5498977","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":443356330,"identity":"c51fb19e-61f8-4e28-b6cb-08bf795578c4","order_by":0,"name":"Yang Peng","email":"","orcid":"","institution":"First Affiliated Hospital of Chongqing Medical University","correspondingAuthor":false,"prefix":"","firstName":"Yang","middleName":"","lastName":"Peng","suffix":""},{"id":443356331,"identity":"de0de8e6-d18d-4fe1-94ff-6349cfdb0aa6","order_by":1,"name":"Gang Luo","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAA2ElEQVRIie3QsQrCMBCA4QsHyRLsGqH4DH0CfZWEgpOCk3To0EHaQfRZHN0UCp3qKh0c2qV7QaQgiFXB0cRNMP90gfsICYDN9oP13hMDUsog1BP6nhDQK/PsO0L71QINiPD35ByehhGyY6AiCk6ylBoyluhmtR8hnxdq64LIDxsNmXgoaOoD8nGhcgqemJqQ24vMVIxmhDRxOgRkGZgRXksk61R2t6CQeca1b3FY92PtJR0BS6qmDcKBk6w+ky525QBqt+fe48R1689ICzDqaGm0bbPZbP/XHdnfQNGrfM0AAAAAAElFTkSuQmCC","orcid":"","institution":"First Affiliated Hospital of Chongqing Medical University","correspondingAuthor":true,"prefix":"","firstName":"Gang","middleName":"","lastName":"Luo","suffix":""},{"id":443356332,"identity":"ad8a1e45-650c-48dd-a4ad-da9012b9bd39","order_by":2,"name":"Weidong Ni","email":"","orcid":"","institution":"First Affiliated Hospital of Chongqing Medical University","correspondingAuthor":false,"prefix":"","firstName":"Weidong","middleName":"","lastName":"Ni","suffix":""}],"badges":[],"createdAt":"2024-11-21 15:23:24","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-5498977/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-5498977/v1","draftVersion":[],"editorialEvents":[{"content":"https://doi.org/10.1186/s12893-025-02949-y","type":"published","date":"2025-07-03T15:58:46+00:00"}],"editorialNote":"","failedWorkflow":false,"files":[{"id":80730399,"identity":"0944549f-ad5a-468c-ac5e-080fe3d44d2b","added_by":"auto","created_at":"2025-04-16 12:27:46","extension":"jpg","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":16713,"visible":true,"origin":"","legend":"\u003cp\u003eCortical and cancellous bone of the heel bone: cortical bone at a distance of 2 mm, all cancellous bone internally\u003c/p\u003e","description":"","filename":"Picture1.jpg","url":"https://assets-eu.researchsquare.com/files/rs-5498977/v1/758372954e870edc242e2513.jpg"},{"id":80727705,"identity":"06f05ab6-5192-466a-898c-1ea03f2d7ed2","added_by":"auto","created_at":"2025-04-16 12:03:46","extension":"jpg","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":120251,"visible":true,"origin":"","legend":"\u003cp\u003eFracture models based on the Sanders type. a-f are sanders II A, B, C and sanders III AB, AC, BC fracture models respectively\u003c/p\u003e","description":"","filename":"Picture2.jpg","url":"https://assets-eu.researchsquare.com/files/rs-5498977/v1/f9e259d0d07d88a85290084e.jpg"},{"id":80729369,"identity":"b7ac1e2f-65c8-458f-b5a4-e32f07d23e1a","added_by":"auto","created_at":"2025-04-16 12:19:46","extension":"jpg","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":62287,"visible":true,"origin":"","legend":"\u003cp\u003eMesh view with different mesh sizes.\u003c/p\u003e","description":"","filename":"Picture3.jpg","url":"https://assets-eu.researchsquare.com/files/rs-5498977/v1/435406eb1c8c8b2efec252a9.jpg"},{"id":80728684,"identity":"60678301-e515-41b8-9946-bebbe02249dc","added_by":"auto","created_at":"2025-04-16 12:11:46","extension":"jpg","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":8375,"visible":true,"origin":"","legend":"\u003cp\u003eConstraints and loads of the model.\u003c/p\u003e","description":"","filename":"Picture4.jpg","url":"https://assets-eu.researchsquare.com/files/rs-5498977/v1/ff7c16ca22519eb6fd31b195.jpg"},{"id":80730398,"identity":"64699b6b-a563-46d3-a9c5-c3ebc7af8af9","added_by":"auto","created_at":"2025-04-16 12:27:46","extension":"jpg","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":18135,"visible":true,"origin":"","legend":"\u003cp\u003ePre-experimental stress distribution. Stresses are predominantly distributed on the anteromedial aspect of the heel bone\u003c/p\u003e","description":"","filename":"Picture5.jpg","url":"https://assets-eu.researchsquare.com/files/rs-5498977/v1/f6410c73104c45eaefa76eb0.jpg"},{"id":80727706,"identity":"6ef927d6-3726-47da-93c8-4e968f14cbc8","added_by":"auto","created_at":"2025-04-16 12:03:46","extension":"jpg","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":75069,"visible":true,"origin":"","legend":"\u003cp\u003eFour screw orientation designs. a ,e: Study group 1. b ,f: Study group 2. \u0026nbsp;c ,g: Control group 1. d ,h: Control group 2\u003c/p\u003e","description":"","filename":"Picture6.jpg","url":"https://assets-eu.researchsquare.com/files/rs-5498977/v1/843764bf37ea581e78a6bc4b.jpg"},{"id":80728690,"identity":"df00572c-5b1d-4373-9771-04db146e48ce","added_by":"auto","created_at":"2025-04-16 12:11:46","extension":"jpg","order_by":7,"title":"Figure 7","display":"","copyAsset":false,"role":"figure","size":144207,"visible":true,"origin":"","legend":"\u003cp\u003ePeak stresses on the calcaneus(MPa)\u003c/p\u003e","description":"","filename":"Picture7.jpg","url":"https://assets-eu.researchsquare.com/files/rs-5498977/v1/fc19db36dad96c42f9ffcd47.jpg"},{"id":80728685,"identity":"fedf77c1-4a93-4e89-b25a-0680b2383f24","added_by":"auto","created_at":"2025-04-16 12:11:46","extension":"jpg","order_by":8,"title":"Figure 8","display":"","copyAsset":false,"role":"figure","size":131331,"visible":true,"origin":"","legend":"\u003cp\u003ePeak stresses on the screws(MPa)\u003c/p\u003e","description":"","filename":"Picture8.jpg","url":"https://assets-eu.researchsquare.com/files/rs-5498977/v1/b106a0bd837de4e4916f1641.jpg"},{"id":80729370,"identity":"dbb8341d-d6ad-431b-b5e7-0d59ff81f425","added_by":"auto","created_at":"2025-04-16 12:19:46","extension":"jpg","order_by":9,"title":"Figure 9","display":"","copyAsset":false,"role":"figure","size":337568,"visible":true,"origin":"","legend":"\u003cp\u003eStress distribution of screws for different internal fixation methods in six fracture models. a-d (II A), e-h (II B), i-l (II C), m-p (III AB), q-t (III AC) and u-x (III BC) were fixed using four different screw fixation methods. It can be seen that the colour of the medial longitudinal screws in the study group and control group 1 is darker than that of those in control group 2 and control group 3. This indicates that the medial longitudinal screws in the study group and control group 1 carry a higher load than those in control group 2 and control group 3.\u003c/p\u003e","description":"","filename":"Picture9.jpg","url":"https://assets-eu.researchsquare.com/files/rs-5498977/v1/9ecdda72bee1a6392c04cd2e.jpg"},{"id":80727708,"identity":"9020ad99-b8b3-4608-89c2-cecbf5c416a1","added_by":"auto","created_at":"2025-04-16 12:03:46","extension":"jpg","order_by":10,"title":"Figure 10","display":"","copyAsset":false,"role":"figure","size":128516,"visible":true,"origin":"","legend":"\u003cp\u003ePeak displacement(mm).\u003c/p\u003e","description":"","filename":"Picture10.jpg","url":"https://assets-eu.researchsquare.com/files/rs-5498977/v1/5465831e28940938a31d2d38.jpg"},{"id":80727717,"identity":"5c56df93-afc2-4d99-9857-40d8d69dee39","added_by":"auto","created_at":"2025-04-16 12:03:46","extension":"jpg","order_by":11,"title":"Figure 11","display":"","copyAsset":false,"role":"figure","size":218846,"visible":true,"origin":"","legend":"\u003cp\u003eDisplacement nephogram between fracture fragments: a-d, e-h, i-l, m-p, q-t, and u-x represent four types of screw fixation methods for Sanders IIA, IIB, IIC, and IIIAB, IIIAC, IIIBC calcaneal fractures, respectively.\u003c/p\u003e","description":"","filename":"Picture11.jpg","url":"https://assets-eu.researchsquare.com/files/rs-5498977/v1/4d7ca3f908cf86edc644ff62.jpg"},{"id":80728696,"identity":"ca1d01ec-952c-4b53-bd6d-d987acba8a9f","added_by":"auto","created_at":"2025-04-16 12:11:46","extension":"jpg","order_by":12,"title":"Figure 12","display":"","copyAsset":false,"role":"figure","size":136748,"visible":true,"origin":"","legend":"\u003cp\u003eSchematic diagram of longitudinal screw fixation of the carrier talonavicular fracture block in sanders II calcaneal fracture. a-d are sanders II A calcaneal fracture. e-h are sanders II B calcaneal fracture. i-l are sanders II C calcaneal fracture. a, e, i are study groups. b, f, j are control groups1. c, g, k are control groups2. d, h, l are control groups3. In sanders II A and sanders II B calcaneal fractures the longitudinal screws in all four groups immobilized to the carrier talonavicular process, whereas in sanders II C calcaneal fractures the longitudinal screws in control group 2 and control group 3 lost immobilization to the carrier talonavicular process.\u003c/p\u003e","description":"","filename":"Picture12.jpg","url":"https://assets-eu.researchsquare.com/files/rs-5498977/v1/85266a741ab48c2ae1fa47bb.jpg"},{"id":86180022,"identity":"444cc36a-7d5a-4835-8623-6ebd07916545","added_by":"auto","created_at":"2025-07-07 16:20:53","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":2253977,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-5498977/v1/1564275e-5319-4417-9e44-7c468958ee4e.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"A Finite Element Analysis of the Optimal Longitudinal Screw Trajectory for Sanders II and Sanders III Calcaneal Fractures Fixed with Percutaneous Screws","fulltext":[{"header":"Introduction","content":"\u003cp\u003eCalcaneal fractures represent one of the most frequent types of foot fractures, typically resulting from high-energy trauma, including traffic accidents and falls from significant heights \u003csub\u003e\u003cspan type=\"SmallCaps\" class=\"SmallCaps\" name=\"Emphasis\"\u003e[1, 2]\u003c/span\u003e\u003c/sub\u003e. The calcaneus is a critical weight-bearing bone in the foot. The optimal treatment approach for calcaneal fractures remains a subject of debate \u003csub\u003e\u003cspan type=\"SmallCaps\" class=\"SmallCaps\" name=\"Emphasis\"\u003e[3\u0026minus;5]\u003c/span\u003e\u003c/sub\u003e. In recent years, there has been a notable increase in the utilization of minimally invasive techniques within the field of orthopedics. Among these techniques, percutaneous screw fixation has gradually become an important method for treating calcaneal fractures due to its advantages of minimal trauma and rapid recovery, as evidenced by the literature \u003csub\u003e\u003cspan type=\"SmallCaps\" class=\"SmallCaps\" name=\"Emphasis\"\u003e[6\u0026minus;12]\u003c/span\u003e\u003c/sub\u003e. Smerek et al., through cadaveric studies, demonstrated no significant difference in strength between screw fixation and plate fixation for Sanders II B calcaneal fractures \u003csub\u003e\u003cspan type=\"SmallCaps\" class=\"SmallCaps\" name=\"Emphasis\"\u003e[13]\u003c/span\u003e\u003c/sub\u003e. Tornetta et al., in a retrospective analysis, found that percutaneous screw fixation was comparable to open reduction and internal fixation for Sanders IIC calcaneal fractures and, in some cases, superior \u003csub\u003e\u003cspan type=\"SmallCaps\" class=\"SmallCaps\" name=\"Emphasis\"\u003e[14]\u003c/span\u003e\u003c/sub\u003e. The results of the latest meta-analysis indicate that screw fixation for calcaneal fractures provides comparable fixation strength and clinical efficacy to plate fixation, while offering shorter operating times and a lower incidence of incision-related complications \u003csub\u003e\u003cspan type=\"SmallCaps\" class=\"SmallCaps\" name=\"Emphasis\"\u003e[15]\u003c/span\u003e\u003c/sub\u003e.\u003c/p\u003e \u003cp\u003eAlthough the efficacy of screw fixation has been widely recognized by scholars, there is no consensus on the optimal screw trajectory to achieve maximum biomechanical strength. Current studies on the design of screw fixation trajectories have not fully taken into account the anatomical structure of the calcaneus and the injury mechanisms of calcaneal fractures. This study aims to explore the optimal longitudinal screw fixation trajectory using finite element analysis (FEA).\u003c/p\u003e"},{"header":"Methods","content":"\u003cp\u003e \u003cb\u003eSoftware used for research\u003c/b\u003e: (\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e) Medical imaging software: Mimics 21.0 (Materialise Ltd, Belgium); (\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e) three-dimensional optimization software: Geomagic Wrap 2021 (Rainrrop Ltd, USA); (\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e) CAD software: SolidWorks 2022 (Dassault Syst\u0026egrave;mes Ltd, USA); (\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e) finite element analysis software: ANSYS Workbench 2022 R1 (ANSYS Ltd, USA).\u003c/p\u003e \u003cp\u003e \u003cb\u003eFinite Element Modeling Process\u003c/b\u003e: The CT data of a healthy subject (gender: male, age: 54 years old, height: 64 kg, weight: 165 cm, CT layer thickness: 0.6 mm) was processed using Mimics 21.0 software to extract the three-dimensional structure of the calcaneus. The reconstructed calcaneal model was imported into Geomagic Wrap 2021, and the model was smoothed to remove noise and irregularities to ensure the accuracy of the model. The software's function was utilized to define the cortical bone as the outer 2 mm layer, with the remaining internal region designated as cancellous bone (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e). The CAD file obtained in Geomagic Wrap 2021 was imported into Solid Works 2022 to create a model of the calcaneal fracture and simulate percutaneous screw fixation. According to the Sanders classification, we designed six fracture models in SolidWorks 2022, including Sanders IIA, IIB, IIC, and Sanders IIIAB, IIIAC, IIIBC (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e) \u003csub\u003e\u003cspan type=\"SmallCaps\" class=\"SmallCaps\" name=\"Emphasis\"\u003e[16, 17]\u003c/span\u003e\u003c/sub\u003e. Based on the Essex-Lopresti classification, all these fractures were of the joint depression type.\u003c/p\u003e \u003cp\u003e \u003cstrong\u003eMesh validation\u003c/strong\u003e \u003cp\u003eAppropriate mesh division helps improve the accuracy of experimental results and reduce computational costs. In the ANSYS Workbench 2022 R1 software, we conducted stress analyses using mesh sizes of 1.75 mm, 1.5 mm, 1.25 mm, and 1 mm, respectively. As the mesh resolution increased, the changes in the results became progressively smaller, indicating that the mesh was sufficiently refined. Ultimately, we determined the optimal mesh size to be 1 mm.\u003c/p\u003e \u003c/p\u003e \u003cp\u003e \u003cstrong\u003eMaterial properties and contact settings\u003c/strong\u003e \u003cp\u003eBased on previous studies on finite element analysis of the calcaneus, the contact between screws and fracture fragments was defined as bonded, while the friction coefficient between fracture fragments was set to 0.2. The materials in the model were simplified as homogeneous elastic materials, and their properties are listed in Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e.\u003c/p\u003e \u003c/p\u003e \u003cp\u003e \u003cstrong\u003eLoad and boundary conditions\u003c/strong\u003e \u003cp\u003eDuring the analysis, the loading conditions of the calcaneus during normal standing were simulated. The cuboid articular surface and the posterior tuberosity of the calcaneus, which are in contact with the ground, were set as fixed supports. Forces of 420 N and 200 N were applied to the posterior talar articular facet and the middle talar articular facet, respectively (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e) \u003csub\u003e\u003cspan type=\"BoldSmallCaps\" class=\"BoldSmallCaps\" name=\"Emphasis\"\u003e[18, 19]\u003c/span\u003e\u003c/sub\u003e.\u003c/p\u003e \u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab1\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eThe effect of different mesh sizes on the maximum stress of the calcaneus.\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=\"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 \u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eMesh sizes(mm)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eNumber of Elements\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\u003eMaximum Stress of Calcaneus(MPa)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003eChanges in stress(%)\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e1.75\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e56573\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e99673\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e14.501\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e-\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e1.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e78729\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e137210\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e15.495\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e6.85\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e1.25\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e109007\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e191487\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e16.051\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e3.59\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e162984\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e287319\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e16.324\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e1.7\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 \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\u003eMaterial properties in the finite element analysis\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"3\"\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 \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eMaterials\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eYoung's modulus (MPa)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003ePoisson's ratio\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eScrew\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e200000\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0.28\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eCortical bone\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e7300\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0.3\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eCancellous bone\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e100\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0.3\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 \u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003cstrong\u003ePre-experiment\u003c/strong\u003e \u003cp\u003eIn order to make our screw design more scientific, a pre-experiment was conducted before the start of the experiment to analyze the stress distribution of the calcaneus during standing in normal subjects. As mentioned above, the calcaneocuboid joint surface and the contact points between the posterior calcaneal tubercle and the ground were fixed, and forces of 420N and 200N were applied to the posterior subtalar joint surface and the middle subtalar joint surface, respectively, to simulate the force on the calcaneus during normal walking(Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e). The calculation showed that the stress was mainly concentrated on the anterior medial side of the calcaneus (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e).\u003c/p\u003e \u003c/p\u003e \u003cp\u003e \u003cstrong\u003eExperimental design\u003c/strong\u003e \u003cp\u003eBased on the injury mechanism of calcaneal fractures, anatomical structure, and our preliminary experimental results, we believe that a medial longitudinal screw fixed from the calcaneal tuberosity to the sustentaculum tali can provide better stability. Therefore, we designed two different screw trajectories, referred to as the study group and the control group. In both groups, we used two 3.5 mm cannulated screws (transverse screws) and two 5.5 mm cannulated screws (longitudinal screws). The two 3.5 mm cannulated screws were fixed from the calcaneal tuberosity to the sustentaculum tali to stabilize the articular fracture fragments, and the spatial positions of these screws were kept absolutely consistent across all four groups. The main difference between the study group and the control group lies in the fixation paths of the two longitudinal screws. In the study group, the medial longitudinal screw was fixed from the calcaneal tuberosity to the sustentaculum tali, while in the control group, both longitudinal screws were fixed from the calcaneal tuberosity to the anterior process of the calcaneus. To avoid the influence of screw insertion angles on the results, we further refined the design of the study group and the control group. The study group was subdivided into Study Group 1 and Study Group 2, with the difference being that the two longitudinal screws in Study Group 1 were inserted in a non-crossed manner (Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003ea, e), while those in Study Group 2 were inserted in a crossed manner (Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003eb, f). Similarly, the control group was subdivided into Control Group 1 and Control Group 2, where the two longitudinal screws in Control Group 1 were inserted parallelly into the anterior process of the calcaneus (Figs.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003ec ,g), and those in Control Group 2 were inserted in a crossed manner from the calcaneal tuberosity (Figs.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003ed ,h).\u003c/p\u003e \u003c/p\u003e "},{"header":"Results","content":"\u003cp\u003e \u003cstrong\u003eMaximum von Mises equivalent stress on bone\u003c/strong\u003e \u003cp\u003eFigure\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e7\u003c/span\u003e illustrates the maximum stress distribution on the bone across the six fracture models. The maximum stress on the bone in the study groups was observed to be lower than that in control groups. This indicates that fixing the medial longitudinal screw from the calcaneal tubercle to the sustentaculum tali can facilitate a more uniform dispersion of the stress on the calcaneal cortical bone. Moreover, no significant difference was observed in the maximum stress on the bone between the study group 1 and 2, indicating that the crossing of the two longitudinal screws has a minimal impact on the stress distribution on the bone.\u003c/p\u003e \u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\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\u003eMaximum stress of the calcaneus (MPa).\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=\"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 \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eSanders classification\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eStudy group 1\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eStudy group 2\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eControl group1\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003eControl group2\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eⅡA\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e29.189\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e28.93\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e30.975\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e31.574\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eⅡB\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e33.485\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e33.714\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e38.84\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e38.599\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eⅡC\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e39.385\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e38.884\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e46.429\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e46.669\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eⅢAB\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e34.212\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e37.105\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e39.401\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e39.396\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eⅢAC\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e39.63\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e39.676\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e49.386\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e48.564\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eⅢBC\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e40.865\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e40.972\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e51.265\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e50.141\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 \u003c/p\u003e \u003cp\u003e \u003cstrong\u003eMaximum von Mises equivalent stress on the screw\u003c/strong\u003e \u003cp\u003eThe maximum screw stress reflects, to some extent, the degree of stress dispersion. Lower maximum screw stress corresponds to a reduced risk of internal fixation failure. The maximum screw stress for the six fracture models is presented in Fig.\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e7\u003c/span\u003e. In the Ⅱ A fracture model, the screw stress in the study group was higher than in control groups. For the Ⅱ B and Ⅲ AB fracture models, no significant differences in screw stress were observed across the four groups. However, in the II C, III AC, and III BC fracture models, the screw stress in the study groups was lower than in control groups. This finding suggests that, in these three fracture models, securing the medial longitudinal screw to the sustentaculum tali reduces the maximum screw stress, thereby decreasing the risk of internal fixation failure. Additionally, no significant difference in maximum screw stress was observed between the study group 1 and 2, indicating that whether the two longitudinal screws cross has minimal impact on the maximum screw stress distribution. Across all six fracture models, the maximum stress of the medial longitudinal screw in the study group exceeded that in control groups (Fig.\u0026nbsp;\u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e8\u003c/span\u003e). This observation indicates that a medial longitudinal screw fixed to the sustentaculum tali bears more stress and achieves better biomechanical performance. According to previous studies, implant stress exceeding 600 MPa may pose a risk of internal fixation failure \u003csub\u003e\u003cspan type=\"SmallCaps\" class=\"SmallCaps\" name=\"Emphasis\"\u003e[20]\u003c/span\u003e\u003c/sub\u003e. In this study, the stress on all screws remained below this threshold, indicating acceptable biomechanical safety.\u003c/p\u003e \u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\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\u003eMaximum stress of the screws (MPa).\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=\"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 \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eSanders classification\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eStudy group 1\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eStudy group 2\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eControl group1\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003eControl group2\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eⅡA\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e77.147\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e76.602\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e48.067\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e46.327\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eⅡB\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e99.838\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e100.61\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e95.01\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e89.943\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eⅡC\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e129.08\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e125.48\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e177.11\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e158.65\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eⅢAB\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e116.33\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e119.53\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e116.27\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e110.27\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eⅢAC\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e133.35\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e133.61\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e174.05\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e155.44\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eⅢBC\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e157.97\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e162.95\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e225.17\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e210.97\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 \u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003cstrong\u003eMaximum displacement of the fracture fragment\u003c/strong\u003e \u003cp\u003eIn the fracture model, the optimal internal fixation effect is achieved when the displacement of the fracture block is minimized. Figure\u0026nbsp;\u003cspan refid=\"Fig9\" class=\"InternalRef\"\u003e9\u003c/span\u003e illustrates the maximum displacement of the fracture fragment in the six fracture models. The displacement of the fracture fragment in the study groups was found to be smaller than that observed in control groups. This difference was particularly evident in the II C, III AC, and III BC fracture models. Additionally, no significant difference was noted in the maximum displacement of the fracture block between the study group 1 and 2, suggesting that the crossing or non-crossing of the two longitudinal screws had a minimal impact on the maximum displacement of the fracture fragment. Figure\u0026nbsp;\u003cspan refid=\"Fig10\" class=\"InternalRef\"\u003e10\u003c/span\u003e shows the displacement cloud map between fracture fragments, with the maximum displacement located near the primary fracture line.\u003c/p\u003e \u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab5\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 5\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eMaximum displacement between fracture fragments (mm).\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=\"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 \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eSanders classification\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eStudy group 1\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eStudy group 2\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eControl group1\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003eControl group2\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eⅡA\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e0.15162\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0.14991\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.16893\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.17622\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eⅡB\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e0.27041\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0.28076\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.32645\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.3107\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eⅡC\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e0.31389\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0.34582\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.4633\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.46981\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eⅢAB\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e0.28799\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0.31582\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.34591\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.33986\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eⅢAC\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e0.35168\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0.35695\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.50198\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.48265\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eⅢBC\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e0.40016\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0.39689\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.56833\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.54094\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 \u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003c/p\u003e"},{"header":"Discussion","content":"\u003cp\u003ePercutaneous screw fixation has gained prominence as a method of fixation in the treatment of calcaneal fractures, concurrent with the increasing utilization of closed reduction techniques in clinical practice \u003csub\u003e\u003cspan type=\"SmallCaps\" class=\"SmallCaps\" name=\"Emphasis\"\u003e[11, 21\u0026minus;23]\u003c/span\u003e\u003c/sub\u003e. The biomechanical stability of screw fixation has also emerged as a prominent area of investigation in the management of calcaneal fractures. A substantial body of clinical evidence substantiates the assertion that screw-only osteosynthesis can achieve comparable fixation strength and stability to that of plate fixation \u003csub\u003e\u003cspan type=\"SmallCaps\" class=\"SmallCaps\" name=\"Emphasis\"\u003e[6\u0026minus;8, 11, 12, 24]\u003c/span\u003e\u003c/sub\u003e. Previous finite element analysis has also corroborated that the displacement of the fracture block is analogous between simple screw fixation and locking plate fixation. Both fixation methods have been demonstrated to provide sufficient stability in the treatment of calcaneal fractures \u003csub\u003e\u003cspan type=\"SmallCaps\" class=\"SmallCaps\" name=\"Emphasis\"\u003e[24]\u003c/span\u003e\u003c/sub\u003e. It is important to note, however, that while the aforementioned studies confirm the effectiveness of simple screw fixation, the screw paths utilized in each study are distinct. This indicates that there is currently no consensus regarding the optimal method for fixing calcaneal fractures with simple screw fixation.\u003c/p\u003e \u003cp\u003eFinite element analysis is used in the biomechanical study of internal fixation of fractures because of its ability to simulate complex shapes, loads and material properties with high accuracy and speed \u003csub\u003e\u003cspan type=\"SmallCaps\" class=\"SmallCaps\" name=\"Emphasis\"\u003e[25]\u003c/span\u003e\u003c/sub\u003e. Studies have shown that the use of finite element analysis for the biomechanical study of fracture internal fixation devices can achieve the same validation effect as in vitro cadaver experiments\u003csub\u003e\u003cspan type=\"SmallCaps\" class=\"SmallCaps\" name=\"Emphasis\"\u003e[24]\u003c/span\u003e\u003c/sub\u003e. We used finite element analysis to study the stability of different screw fixation methods. When designing the screw fixation method, we did not study the fixation stability by increasing or decreasing the number of screws, but by designing different screw fixation paths to study the stability of different screw fixation methods. The theoretical basis for the design of the screw trajectory is the injury mechanism of calcaneal fracture, the anatomical morphology of the calcaneus, and the results of our preliminary experiments, so as to maximize the scientific and rational design of the screw trajectory.\u003c/p\u003e \u003cp\u003eIn the process of calcaneal fracture formation, the violence is transmitted from the talus to the calcaneus through the middle and posterior subtalar articular surfaces, and the calcaneus forms a primary fracture line under shearing force, dividing the calcaneus into two main fracture blocks: the anterior medial and the posterior lateral. if the fracture involves an anteromedial and a posterolateral fragment, a sagittal fracture line may be observed, further complicating the fracture pattern. The findings of our preliminary experiments align with this hypothesis. In a normal standing position, the majority of the stress is concentrated on the anterior medial side of the calcaneus, specifically the anterior process of the calcaneus, the calcaneal groove, the posterior subtalar articular surfaces, the sustentaculum tali, and the medial wall. Depending on the orientation of the secondary fracture line, two main types of fractures can be distinguished: tongue-type fractures and joint depression-type fractures. In tongue-type fractures, the secondary fracture line extends posteriorly, creating a large posterior superior fragment. In joint depression-type fractures, the secondary fracture line results in a depressed fragment of the posterior facet \u003csub\u003e\u003cspan type=\"SmallCaps\" class=\"SmallCaps\" name=\"Emphasis\"\u003e[26, 27]\u003c/span\u003e\u003c/sub\u003e. Zwipp subdivides the calcaneal fracture block into five distinct regions based on the computed tomography (CT) manifestations observed in calcaneal fractures. These include the calcaneal tubercle fracture block, the calcaneal sustentaculum tali fracture block, the calcaneal posterior subtalar joint fracture block, the calcaneal anterior tubercle fracture block, and the calcaneal anterior subtalar joint fracture block \u003csub\u003e\u003cspan type=\"SmallCaps\" class=\"SmallCaps\" name=\"Emphasis\"\u003e[28]\u003c/span\u003e\u003c/sub\u003e. The calcaneal tubercle fracture block is the key fracture block that causes changes in the shape of the calcaneus, and its displacement largely affects the shape of the calcaneus (height, width, length, and varus/valgus). Therefore, the key to maintaining the shape of the calcaneus using simple screw fixation is how to stabilize the calcaneal tubercle fracture block, that is, how to connect the calcaneal tubercle fracture block with the remaining four main fracture blocks into a whole through a reasonable screw trajectory. In this study, we designed four screw trajectories for fixing the calcaneal tubercle fracture block with the remaining four main fracture blocks. The results showed that the longitudinal screw trajectory in the study group and control group 1 could disperse the stress on the bone and screws more evenly and reduce the displacement of the fracture block. This suggests that the optimal trajectory for the medial longitudinal screw may be from the calcaneal tubercle along the medial wall of the calcaneus to the sustentaculum tali. The screw should be more inclined towards the medial side of the calcaneus rather than the anterior side.\u003c/p\u003e \u003cp\u003eIn the Sanders II C, Sanders III AC, and Sanders III BC fracture models, the screw trajectories of the study group and control group 1 not only disperse the stress on the implant but also significantly reduce the displacement of the sustentaculum tali fracture block. However, in the Ⅱ A, Ⅱ B, and Ⅲ AB fracture models, although the screw direction of the study group can also reduce the displacement of the fracture block, the difference is not as obvious as in the Sanders II C and Sanders III AC, Ⅲ BC fracture models. We believe that this may be closely related to the difference in the course of the primary fracture line, which also affects the size of the formed sustentaculum tali fracture block. The closer the primary fracture line is to the calcaneal groove, the smaller the formed sustentaculum tali fracture block will be. When the sustentaculum tali fracture block is large, fixing the longitudinal screw to the anterior process of the calcaneus can also play a certain stabilizing role, but when the sustentaculum tali fracture fragment is small, the longitudinal screw needs to be fixed to the sustentaculum tali to fix the sustentaculum tali fracture fragment (Fig.\u0026nbsp;\u003cspan refid=\"Fig11\" class=\"InternalRef\"\u003e11\u003c/span\u003e). For Sanders II C and Sanders III AC, BC fracture models, since the sustentaculum tali fracture block is relatively small, if the longitudinal screw does not directly go to the sustentaculum tali, it will not provide the best fixation strength. Therefore, in the three fracture models, the control group 2 and 3 models show more obvious fracture block displacement. This result shows that for the three calcaneal fractures, when using screw fixation, a longitudinal screw from the calcaneal tubercle to the sustentaculum tali is necessary in order to more securely fix the sustentaculum tali fracture block.\u003c/p\u003e \u003cp\u003eFurthermore, the anatomical characteristics of the calcaneus indicate that the medial longitudinal screw provides superior biomechanical strength by traversing from the calcaneal tubercle along the medial wall of the calcaneus to the sustentaculum tali. The calcaneal tubercle, the calcaneal sustentaculum tali and the calcaneal anterior process are the areas where the trabeculae of the calcaneus converge. These areas have denser and stronger bone, which provides an excellent anatomical basis for screw fixation. In addition, the calcaneal sustentaculum tali, together with the medial wall of the calcaneus, forms a strong medial load-bearing column. The sustentaculum talus is connected to the tibia and talus by the deltoid ligament and the interosseous ligament, respectively. The strength of both bundles of ligaments provides a robust stabilizing effect on the sustentaculum fracture fragment \u003csub\u003e\u003cspan type=\"SmallCaps\" class=\"SmallCaps\" name=\"Emphasis\"\u003e[29, 30]\u003c/span\u003e\u003c/sub\u003e. Therefore, fixing the calcaneal tubercle fracture block to the sustentaculum tali also increases the fixation strength of the calcaneal tubercle fracture block to a certain extent.\u003c/p\u003e \u003cp\u003eIn this study, we did not investigate the optimal screw configuration and direction of the joint surface screws because the use of screws pointing from the thalamic portion to the tuberosity of the sustentaculum tali (sustentaculum tali screws) to fix the articular surface fracture block has been widely used in clinical practice. A large amount of literature confirms that the use of only the sustentaculum tali screw to fix the articular surface fracture block can achieve satisfactory fixation strength and therapeutic effects \u003csub\u003e\u003cspan type=\"SmallCaps\" class=\"SmallCaps\" name=\"Emphasis\"\u003e[31\u0026minus;33]\u003c/span\u003e\u003c/sub\u003e. When using steel plates for fixation, the additional use of sustentaculum tali screws can disperse the stress of the internal fixation model \u003csub\u003e\u003cspan type=\"SmallCaps\" class=\"SmallCaps\" name=\"Emphasis\"\u003e[18]\u003c/span\u003e\u003c/sub\u003e.\u003c/p\u003e\n\u003ch3\u003eInnovation and Deficiency\u003c/h3\u003e\n\u003cp\u003eThe innovation of our research lies in the fact that the longitudinal screw trajectory was designed taking into account the anatomy of the calcaneus and the injury mechanism of calcaneal fractures. In addition, we conducted a pre-experiment to simulate the stress distribution inside the calcaneus during standing in a normal person, which made our screw design more scientific and reasonable. However, the model we constructed is only a relatively simple calcaneal model, and the internal part of the calcaneus is considered homogeneous for stress analysis, ignoring the uneven distribution of trabeculae within the calcaneus and the biomechanical effects of the tendons around the calcaneus on the calcaneus. Our internal fixation model is an idealized representation. In clinical practice, achieving complete anatomical reduction and addressing bone defects formed during calcaneal fractures are highly challenging, and these real-world factors, which were not considered in this study, can significantly affect the biomechanical performance of internal fixation. Therefore, this study can only provide a theoretical basis for the design of screw trajectories in clinical settings, and further validation through cadaveric experiments or clinical studies is necessary to confirm the effectiveness of the results. Additionally, due to the complexity of calcaneal fractures, we only designed models for joint depression-type fractures. Thus, the screw models proposed in this study may not be applicable to all types of calcaneal fracture patterns.\u003c/p\u003e"},{"header":"Conclusion","content":"\u003cp\u003eWhen treating Sanders II and Sanders III calcaneal fractures with percutaneous screw fixation, the medial longitudinal screw is fixed from the calcaneal tubercle along the medial wall to the sustentaculum tali, and the lateral longitudinal screw is fixed from the calcaneal tubercle to the anterior process of the calcaneus, providing optimal biomechanical fixation strength.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eEthics approval and consent to participate\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe healthy subject agreed to participate in this clinical trial by signing an informed consent form. The study was approved by the Ethical Board Review of the First Affiliated Hospital of Chongqing Medical University and was performed in accordance with the ethical standards of the Declaration of Helsinki of 1964.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConsent\u003c/strong\u003e \u003cstrong\u003efor\u003c/strong\u003e \u003cstrong\u003epublication\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eNot\u0026nbsp;applicable.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAvailability of data and materials\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eData is provided within the manuscript and related files\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eCompeting\u003c/strong\u003e \u003cstrong\u003einterests\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe\u0026nbsp;authors\u0026nbsp;declare\u0026nbsp;no\u0026nbsp;competing\u0026nbsp;interests.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFunding\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eNone.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAuthor contributions\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eGang Luo and Yang Peng initiated the study design. Yang Peng is the principal investigator. Yang Peng constructed the finite element model and performed the finite element analysis. Weidong Ni substantially revised the manuscript. All authors read and approved the final manuscript.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAcknowledgements\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eWe would like to thank everyone who helped us with this study\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003ePotter MQ, Nunley JA. Long-term functional outcomes after operative treatment for intra-articular fractures of the calcaneus. J Bone Joint Surg Am. 2009;91(8):1854\u0026ndash;60.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eSnoap T, Jaykel M, Williams C, et al. Calcaneus Fractures: A Possible Musculoskeletal Emergency. J Emerg Med. 2017;52(1):28\u0026ndash;33.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eLi M, Lian X, Yang W et al. Percutaneous Reduction and Hollow Screw Fixation Versus Open Reduction and Internal Fixation for Treating Displaced Intra-Articular Calcaneal Fractures. Med Sci Monit, 2020. 26: p. e926833.e926833.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eRadnay CS, Clare MP, Sanders RW. Subtalar fusion after displaced intra-articular calcaneal fractures: does initial operative treatment matter? J Bone Joint Surg Am, 2009. 91(3): p. 541-6.541-6.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eReddy V, Fukuda T, Ptaszek AJ. Calcaneus malunion and nonunion. Foot Ankle Clin. 2007;12(1):125\u0026ndash;35.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003ede Vroome SW, van der Linden FM. Cohort study on the percutaneous treatment of displaced intra-articular fractures of the calcaneus. Foot Ankle Int. 2014;35(2):156\u0026ndash;62.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eJin C, Weng D, Yang W, et al. Minimally invasive percutaneous osteosynthesis versus ORIF for Sanders type II and III calcaneal fractures: a prospective, randomized intervention trial. J Orthop Surg Res. 2017;12(1). p. 10.10.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eNosewicz T, Knupp M, Barg A et al. Mini-open sinus tarsi approach with percutaneous screw fixation of displaced calcaneal fractures: a prospective computed tomography-based study. Foot Ankle Int, 2012. 33(11): p. 925-33.925-33.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eLong C, Li K, Zhu J et al. \u003cem\u003eThree-step closed reduction and percutaneous screw fixation: A reliable and reproducible protocol in managing displaced intra-articular calcaneal fractures.\u003c/em\u003e Injury, 2023. 54 Suppl 2: pp. S49-s55.S49-s55.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eNelson JD, McIff TE, Moodie PG et al. Biomechanical stability of intramedullary technique for fixation of joint depressed calcaneus fracture. Foot Ankle Int, 2010. 31(3): p. 229-35.229-35.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eLuo G, Fan C, Gao P et al. An evaluation of the efficacy of percutaneous reduction and screw fixation without bone grafting in Sanders Type-II and Type-III displaced intra-articular calcaneal fractures. BMC Musculoskelet Disord, 2022. 23(1): p. 562.562.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eChen Z, Fan C, Zhang J, et al. A novel minimally invasive percutaneous treatment for Essex-Lopresti joint depression-type DIACFs by ligamentotaxis. BMC Surg. 2022;22(1):431431.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eSmerek JP, Kadakia A, Belkoff SM et al. Percutaneous screw configuration versus perimeter plating of calcaneus fractures: a cadaver study. Foot Ankle Int, 2008. 29(9): p. 931-5.931-5.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eTornetta P 3. rd, Percutaneous treatment of calcaneal fractures. Clin Orthop Relat Res, 2000(375): p. 91-6.91-6.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eWang Q, Zhang N, Guo W et al. Cannulated screw fixation versus plate fixation in treating displaced intra-articular calcaneus fractures: a systematic review and meta-analysis. Int Orthop, 2021. 45(9): p. 2411-2421.2411-2421.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eSanders R. Intra-articular fractures of the calcaneus: present state of the art. J Orthop Trauma. 1992;6(2):252\u0026ndash;65.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eSanders R, Fortin P, DiPasquale T et al. Operative treatment in 120 displaced intraarticular calcaneal fractures. Results using a prognostic computed tomography scan classification. Clin Orthop Relat Res, 1993(290): p. 87-95.87-95.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003ePang QJ, Yu X, Guo ZH. The sustentaculum tali screw fixation for the treatment of Sanders type II calcaneal fracture: A finite element analysis. Pak J Med Sci. 2014;30(5):1099\u0026ndash;103.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eYu B, Chen WC, Lee PY, et al. Biomechanical comparison of conventional and anatomical calcaneal plates for the treatment of intraarticular calcaneal fractures - a finite element study. Comput Methods Biomech Biomed Engin. 2016;19(13):1363\u0026ndash;70.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eHe K, Fu S, Liu S et al. \u003cem\u003eComparisons in finite element analysis of minimally invasive, locking, and non-locking plates systems used in treating calcaneal fractures of Sanders type II and type III.\u003c/em\u003e Chin Med J (Engl), 2014. 127(22): pp. 3894-901.3894-901.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eMarsh JL, Boyer JS, Sullivan J et al. A Percutaneous Technique for Reduction and Internal Fixation of Displaced Intra-Articular Calcaneal Fractures. JBJS Essent Surg Tech, 2011. 1(2): p. e9.e9.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eDeWall M, Henderson CE, McKinley TO, et al. Percutaneous reduction and fixation of displaced intra-articular calcaneus fractures. J Orthop Trauma. 2010;24(8):466\u0026ndash;72.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eKline AJ, Anderson RB, Davis WH et al. Minimally invasive technique versus an extensile lateral approach for intra-articular calcaneal fractures. Foot Ankle Int, 2013. 34(6): p. 773-80.773-80.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eNi M, Wong DW, Mei J, et al. Biomechanical comparison of locking plate and crossing metallic and absorbable screws fixations for intra-articular calcaneal fractures. Sci China Life Sci. 2016;59(9):958\u0026ndash;64.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eBevill G, Keaveny TM. Trabecular bone strength predictions using finite element analysis of micro-scale images at limited spatial resolution. Bone. 2009;44(4):579\u0026ndash;84.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eRazik A, Harris M, Trompeter A. Calcaneal fractures: Where are we now? Strategies Trauma Limb Reconstr. 2018;13(1):1\u0026ndash;11.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eEssex-Lopresti P. The mechanism, reduction technique, and results in fractures of the os calcis, 1951-52. Clin Orthop Relat Res, 1993(290): pp. 3\u0026ndash;16.3\u0026ndash;16.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eZwipp H, Tscherne H, W\u0026uuml;lker N, et al. [Intra-articular fracture of the calcaneus. Classification, assessment and surgical procedures]. Unfallchirurg. 1989;92(3):117\u0026ndash;29.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eCarr JB. Mechanism and pathoanatomy of the intraarticular calcaneal fracture. Clin Orthop Relat Res, 1993(290): pp. 36\u0026ndash;40.36\u0026ndash;40.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eCain JD, Dalmau-Pastor M. Anatomy of the Deltoid-Spring Ligament Complex. Foot Ankle Clin. 2021;26(2):237\u0026ndash;47.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eGuo ZH, Yan YQ, Tang Y et al. \u003cem\u003e[Finite element optimization analysis of minimally invasive screw treatment for Sanders typeⅡcalcaneal fracture].\u003c/em\u003e Zhongguo Gu Shang, 2021. 34(2): pp. 137-42.137-42.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eGil Monz\u0026oacute; ER, Liew I, Tadikonda P et al. Optimal posterior screw placement configuration in Sanders 2B calcaneal fractures: A biomechanical study. Rev Esp Cir Ortop Traumatol, 2023. 67(2): p. T144-t152.T144-t152.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eZhang H, Lv ML, Liu Y et al. \u003cem\u003eBiomechanical analysis of minimally invasive crossing screw fixation for calcaneal fractures: Implications to early weight-bearing rehabilitation.\u003c/em\u003e Clin Biomech (Bristol, Avon), 2020. 80: p. 105143.105143.\u003c/span\u003e\u003c/li\u003e\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":true,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"bmc-surgery","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"bsur","sideBox":"Learn more about [BMC Surgery](http://bmcsurg.biomedcentral.com/)","snPcode":"","submissionUrl":"https://www.editorialmanager.com/bsur/default.aspx","title":"BMC Surgery","twitterHandle":"@BMC_series","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"em","reportingPortfolio":"BMC Series","inReviewEnabled":true,"inReviewRevisionsEnabled":true},"keywords":"calcaneal fracture, longitudinal screw, finite element analysis, sustentaculum tali","lastPublishedDoi":"10.21203/rs.3.rs-5498977/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-5498977/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003ch2\u003eBackground\u003c/h2\u003e \u003cp\u003eIn recent years, percutaneous screw fixation technology has been extensively utilized in the management of displaced intra-articular calcaneal fractures. However, there remains a lack of consensus regarding the optimal design of screw trajectories to achieve maximal biomechanical strength. The objective of the present study was to identify the optimal screw trajectory for percutaneous screw fixation of calcaneal fractures through the application of finite element analysis.\u003c/p\u003e\u003ch2\u003eMethods\u003c/h2\u003e \u003cp\u003eThe finite element analysis was used in this study. Six fracture models (Sanders IIA, B, C and IIIAB, AC, BC) were constructed according to the Sanders classification system. Based on the injury mechanism of calcaneal fractures, the anatomical characteristics of the calcaneus, and the results of preliminary experiments, four different screw fixation methods were designed to simulate the internal fixation of calcaneal fractures.\u003c/p\u003e\u003ch2\u003eResults\u003c/h2\u003e \u003cp\u003eIn the six fracture models, the maximum stress on the calcaneal bone and the maximum displacement between the fracture blocks in the study group 1 and study group 2 were both less than those in control groups 1 and control groups 2. These differences were particularly significant in the II C, III AC, and III BC fracture models. In the II A fracture model, the screw stress in the study group 1 and study group 2 was higher than in control groups 1 and control groups 2. Conversely, in the II B and III AB fracture models, the differences in screw stress among the four fixation methods were minimal. In the II C, III AC, and III BC fracture models, the screw stress in the study group 1 and study group 2 was lower than that in control groups 1 and control groups 2. Notably, none of the screw stresses exceeded the threshold for internal fixation failure (600 mPa).\u003c/p\u003e\u003ch2\u003eConclusion\u003c/h2\u003e \u003cp\u003eIn the treatment of Sanders II and Sanders III calcaneal fractures with percutaneous screw fixation technique, the lateral longitudinal screw should be fixed from the calcaneal tubercle to the anterior process of the calcaneus, and the medial longitudinal screw should be fixed from the calcaneal tubercle along the medial wall to the calcaneal sustentaculum tali. This configuration is associated with optimal biomechanical stability.\u003c/p\u003e","manuscriptTitle":"A Finite Element Analysis of the Optimal Longitudinal Screw Trajectory for Sanders II and Sanders III Calcaneal Fractures Fixed with Percutaneous Screws","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-04-16 12:03:41","doi":"10.21203/rs.3.rs-5498977/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"decision","content":"Revision requested","date":"2025-04-23T09:40:50+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2025-04-23T09:39:06+00:00","index":"","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-04-20T10:05:49+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"20643476245678370254890985799069056707","date":"2025-04-20T09:55:57+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-04-18T08:16:09+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"86944284613934258917804818140541327459","date":"2025-04-16T09:59:40+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"60804444983447063898239465404828772862","date":"2025-04-15T14:41:22+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"317932338970254624564374465985697229554","date":"2025-04-15T11:01:38+00:00","index":"hide","fulltext":""},{"type":"reviewersInvited","content":"","date":"2025-04-15T09:51:36+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2025-03-25T14:55:01+00:00","index":"","fulltext":""},{"type":"submitted","content":"BMC Surgery","date":"2025-03-23T18:29:52+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"bmc-surgery","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"bsur","sideBox":"Learn more about [BMC Surgery](http://bmcsurg.biomedcentral.com/)","snPcode":"","submissionUrl":"https://www.editorialmanager.com/bsur/default.aspx","title":"BMC Surgery","twitterHandle":"@BMC_series","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"em","reportingPortfolio":"BMC Series","inReviewEnabled":true,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"bc1d37d3-d219-414a-b0c2-13f2b5c1f9dc","owner":[],"postedDate":"April 16th, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"published-in-journal","subjectAreas":[],"tags":[],"updatedAt":"2025-07-07T16:13:24+00:00","versionOfRecord":{"articleIdentity":"rs-5498977","link":"https://doi.org/10.1186/s12893-025-02949-y","journal":{"identity":"bmc-surgery","isVorOnly":false,"title":"BMC Surgery"},"publishedOn":"2025-07-03 15:58:46","publishedOnDateReadable":"July 3rd, 2025"},"versionCreatedAt":"2025-04-16 12:03:41","video":"","vorDoi":"10.1186/s12893-025-02949-y","vorDoiUrl":"https://doi.org/10.1186/s12893-025-02949-y","workflowStages":[]},"version":"v1","identity":"rs-5498977","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-5498977","identity":"rs-5498977","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}