Structure Design and Performance Analysis of a Stem for Tumor-type Knee Prosthesis

Structure Design and Performance Analysis of a Stem for Tumor-type Knee Prosthesis | 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 Structure Design and Performance Analysis of a Stem for Tumor-type Knee Prosthesis Peng Shang, Bolong Chen, Fengbin Jin, Jianjun Zhang, Yancheng Liu, and 1 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-6931418/v1 This work is licensed under a CC BY 4.0 License Status: Under Review Version 1 posted 8 You are reading this latest preprint version Abstract Background: After undergoing tumor-type knee prosthesis replacement, patients with bone tumor in the distal femur may experience aseptic loosening on the femoral side, potentially resulting in implant failure. Compared with the traditional bone cement fixation method, the biological fixation can ensure the long-term stability of the prosthesis. To reduce stress shielding of the biologically fixed femoral stem and enhance its initial stability, this study focuses on the structural design and performance analysis of porous femoral stem. Method: The three-dimensional model of the knee joint was constructed using inverse modeling, and the finite element models were established for prosthetic replacements featuring various femoral stem lengths and fixation methods. The fretting of the femoral stem was designed based on a triply periodic minimal surface (TPMS) structure. To determine the most suitable TPMS structure, quasi-static compression and friction test were performed. Additionally, gait experiments were conducted to collect patient-specific data, using for the loading of the finite element analysis. Result: Both fixation methods exhibited stress shielding, and it increased with greater stem length. Constraining the top of the femoral stem at the femoral isthmus was found to reduce the fretting of the femoral stem. Experimental results showed that the Gyroid structure with 60% porosity demonstrated higher yield strength and friction coefficient, furthermore it maintained an elastic modulus comparable to that of natural bone tissue. Based on data collected from gait experiment, finite element analysis showed that porous femoral stems can effectively reduce stress shielding and fretting. Conclusion: The new type of femoral stem with porous structure can effectively reduce stress shielding and enhance initial stability, providing a valuable reference for future femoral stem design. Femoral stem Structural design Finite element analysis TPMS SLM Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 Figure 9 Figure 10 Figure 11 1. Introduction Malignant bone tumors, such as osteosarcoma, are highly invasive and pose a risk of metastasis. The distal end of the femur is the most common site for the occurrence of such tumors, and the majority of patients are relatively young. With the advancement and standardization of surgical treatments, limb-salvage procedures have shown significantly improved outcomes [ 1 ]. Metal tumor prostheses have become the preferred method for limb reconstruction due to their immediate stability and favorable short- and long-term functional results [ 2 ]. However, complications associated with these prostheses remain unresolved [ 3 , 4 ]. Among them, aseptic loosening is a major issue, significantly impacting the service life and long-term success of tumor-type prosthetic implants, and is one of the leading causes of prosthesis failure [ 5 , 6 ]. Mechanical factors such as prosthetic stability and stress shielding contribute to aseptic loosening. Micromotion at the bone–prosthesis interface affects the initial stability, while the large mismatch in elastic modulus between the prosthesis and natural bone causes stress shielding [ 7 , 8 ]. Therefore, optimizing prosthesis structure is essential for improving the therapeutic effectiveness and longevity of artificial implants. TPMS structures are suitable as porous part of biomedical implant because of the characteristic of high specific surface area and zero mean curvature. The parameterized design can make TPMS structure satisfy different requirement, enabling optimized material distribution and structural performance while providing essential biological compatibility and adequate mechanical strength [ 9 ]. TPMS structures are generally categorized into two main forms: sheet-like and columnar. Oraib [ 10 ] and Qin Jiawei [ 11 ] reported that sheet-like TPMS structures exhibit superior mechanical properties and a higher specific surface area, therefore they can better promote cell proliferation and bone integration. Furthermore, the porosity is critical to balance mechanical strength with biological functionality in porous implants. The finite element method (FEM) is regarded as an efficient tool for conducting preoperative plan simulations, which can utilize the imaging data of the lower limbs for preoperative planning and simulation [ 12 ]. By simulating various loading conditions and using patient-specific anatomical structures, FEM enables implant designs to be refined, reducing the need for extensive experimental testing while enhancing the safety and effectiveness of the prosthesis [ 13 ]. Traditional computer numerical control (CNC) machining encounters significant limitations when producing complex porous structures. In contrast, selective laser melting (SLM) is an advanced additive manufacturing technique, which is suitable for producing porous implants. It enables the fabrication of intricate three-dimensional porous metal components by melting fine metal powders layer by layer, making it an ideal method for producing customized implants [ 14 , 15 ]. Therefore, investigating the length and fixation method of the femoral stem in tumor-type knee prostheses is essential for understanding their influence on aseptic loosening. The femoral stem with porous structures can improve the initial stability of the prosthesis and reduce stress shielding, offering useful reference for the design of improved artificial knee prostheses. 2. Materials and methods 2.1 Establishment of three-dimensional model of knee joint A healthy volunteer with no history of knee joint disease was selected for CT and MRI data acquisition. Bone structures were extracted using Mimics, followed by multiple iterations in Geomagic Wrap to repair the model and correct geometric inconsistencies. In order to create a more reasonable three-dimensional knee joint model, High-resolution and high-contrast MRI images were used to accurately extract and reconstruct the soft tissue. The bone and soft tissue models were assembled in SolidWorks to generate a complete 3D knee joint model, as shown in Fig. 1 . 2.2 Establishment of knee prosthesis model The rotating hinge knee tumor prosthesis used in this study was manufactured by Weigao Company and features a modular design. The primary materials used in the prosthesis include titanium alloy, ultra-high molecular weight polyethylene (UHMWPE), and cobalt–chromium–molybdenum alloy. Based on CT image analysis, a diameter of 12 mm was determined to be suitable for implantation into the femoral medullary cavity. Accordingly, the diameter of the biologically fixed femoral stem was set at 12 mm. Considering that the ideal bone cement thickness in clinical applications is approximately 2 mm [ 16 ], the diameter of the cemented femoral stem was designed to be 8 mm. To investigate the effect of femoral stem length on the surrounding bone, four stem lengths were evaluated: 80 mm, 95 mm, 110 mm, and 125 mm. A 1 mm gap was introduced between the femoral stem and the femoral base to avoid incomplete contact and ensure consistent modeling conditions [ 17 ]. Taking the 110 mm stem as an example, the biologically fixed prosthesis stem consists of an external porous region and an internal solid core, as illustrated in Fig. 2 . 2.3 Design of TPMS porous structure model TPMS structures can be represented using various methods, including parameterization, boundary representation, and implicit surface functions [ 18 ]. Among them, implicit surface functions offers a relatively straightforward approach to modeling complex geometries. This study selects three typical TPMS structures—Gyroid, Diamond, and Primitive—whose implicit surface equations are showed in Table 1 . Among them, L represents the size of the TPMS unit cell, and C is used to adjust the bias function of the TPMS structure. Table 1 Equation of TPMS structure TPMS Structural equation G \(\:\text{c}\text{o}\text{s}\left(\frac{2\pi\:}{L}x\right)\text{s}\text{i}\text{n}\left(\frac{2\pi\:}{L}y\right)+\text{c}\text{o}\text{s}\left(\frac{2\pi\:}{L}y\right)\text{s}\text{i}\text{n}\left(\frac{2\pi\:}{L}z\right)+\text{c}\text{o}\text{s}\left(\frac{2\pi\:}{L}z\right)\text{s}\text{i}\text{n}\left(\frac{2\pi\:}{L}x\right)=C\) D \(\:\text{c}\text{o}\text{s}\left(\frac{2\pi\:}{L}x\right)\text{c}\text{o}\text{s}\left(\frac{2\pi\:}{L}\text{y}\right)\text{c}\text{o}\text{s}\left(\frac{2\pi\:}{L}z\right)-\text{s}\text{i}\text{n}\left(\frac{2\pi\:}{L}x\right)\text{s}\text{i}\text{n}\left(\frac{2\pi\:}{L}y\right)\text{s}\text{i}\text{n}\left(\frac{2\pi\:}{L}z\right)=C\) P \(\:\text{c}\text{o}\text{s}\left(\frac{2\pi\:}{L}x\right)+\text{c}\text{o}\text{s}\left(\frac{2\pi\:}{L}y\right)+\text{c}\text{o}\text{s}\left(\frac{2\pi\:}{L}z\right)=C\) By adjusting the bias parameter C in the implicit function of TPMS structures, models with different porosities can be generated. This study focuses on three porosity levels − 50%, 60% and 70%. The biocompatibility study indicates that when the porosity is around 60%, it can promote bone ingrowth[ 19 ]. For ease of recording, the 60% porosity Gyroid porous structure is named as YG60. The sample dimensions are set to 10 mm × 10 mm × 12 mm, with a unit cell size of 2 mm. 2.4 Establishment of finite element model after prosthetic replacement surgery The prosthesis model was assembled with the knee joint model to simulate knee replacement surgery and serve as the basis for subsequent numerical simulations. Due to the complexity of the human skeletal structure and the significant variation in bone material properties, a grayscale assignment method based on CT images [ 20 , 21 ] was used to assign material properties to the bone model. Material properties for other components were assigned according to values listed in Table 2 [ 22 – 26 ]. In this study, a Coulomb friction contact condition with a friction coefficient of 0.63 was applied at the bone–prosthesis interface of the biological prosthesis to simulate the immediate postoperative scenario [ 27 ]. At the bone–cement interface, a bonded contact condition was applied, while a Coulomb friction contact with a coefficient of 0.25 was set at the cement–prosthesis interface [ 28 ]. The simulation modeled the knee joint in full extension under a vertical downward load of 700 N applied at the femoral head to represent the standing position. Table 2 Material property parameters Component name Young’s modulus (MPa) Poisson’s ratio Gristle 15 0.46 Anteriior cruciate ligament 116 0.3 Posterior cruciate ligament 87 0.3 Mediial lateral cruciate ligament 48 0.3 Meniscus 27.5 0.33 Titanium alloy 117 0.3 Ultra-high molecular polyethylene 0.685 0.4 Cobalt-chromium-molybdenum alloy 220 0.3 Bone cement 2280 0.3 2.5 Porous Structure Mechanics and Friction Testing To obtain a porous structure that closely matches the elastic modulus of the human femur while ensuring good initial stability, this study conducted quasi-static compression and friction-wear tests on TPMS porous structures. The samples were fabricated using selective laser melting (SLM) technology with Ti-6Al-4V metal powder. Quasi-static compression tests were performed using a C53-195GL electronic universal testing machine, as shown in Fig. 4 (a). During compression, the samples were continuously loaded until plastic deformation occurred. The deformation behavior of each sample was monitored, stress-strain curves were generated, and the elastic modulus and yield strength were calculated. A sample with an elastic modulus lower than that of cortical bone can effectively reduce stress shielding in the femoral stem, while a yield strength higher than that of cortical bone helps prevent mechanical failure. The friction performance of the porous structure is a critical factor in ensuring the initial stability of the femoral stem. The MZF-1 rotary reciprocating friction and wear tester was used to measure the friction coefficient between cortical bone, cancellous bone, and various TPMS structures, as shown in Fig. 4 (b). In the test, the bone pin was prepared from bovine cortical and cancellous bone, with a diameter of 5 mm and a length of 15 mm. An axial load of 30 N was applied between the bone pin and the porous sample. The reciprocating friction speed was set to 5 mm/s, with a stroke length of 20 mm and a total friction duration of 10 minutes. In order to simulate the environment after implantation, bovine serum lubricant at a concentration of 20 g/L was used during testing [ 29 ]. During the test, the first peak value of the friction coefficient recorded was defined as the static friction coefficient [ 30 ], and the average friction coefficient during steady-state sliding was defined as the dynamic friction coefficient [ 31 ]. (b) Friction test equipment 2.6 Gait test Gait test provides real motion and loading data from patients who have received total knee arthroplasty. Using these measurements to conduct finite element analysis enables more accurate simulation of physiological conditions and enhans the reliability of the simulation results. Before the test, a volunteer who had undergone tumor-type knee prosthesis replacement surgery on the right leg was recruited. Reflective markers were placed on key anatomical landmarks of the lower limbs, including the greater trochanter of the femur (representing the hip joint), the medial and lateral femoral condyles, the patella (for tracking knee joint motion), the medial and lateral malleoli (at the ankle), and key points on the foot. The volunteer was instructed to walk naturally along a path equipped with a force plate. During the test, the Vicon system captured the motion data of lower limbs, while the Kistler force platform recorded the reaction forces from the ground. The collected data were initially screened to identify continuous and stable segments, in order to ensure the validity of subsequent analysis. Motion data were then processed using OpenSim software to calculate hip joint contact forces during various phases of the gait cycle [ 32 – 34 ]. These gait-derived forces were applied as boundary conditions in the finite element model. Finally, the stress shielding and initial stability performances of a conventional biological femoral stem and the optimized porous femoral stem proposed in this study were compared to evaluate the effectiveness of the structural optimization. 3. Results 3.1 Finite element analysis after prosthetic replacement surgery To investigate the influence of different femoral stem lengths and fixation methods on femoral stress distribution, the femur was divided into several regions of interest (ROIs). Finite element analysis was used to calculate the average von Mises stress within each ROI, enabling evaluation of the stress shielding, as illustrated in Fig. 5 [ 13 , 26 , 35 ]. The finite element analysis results are shown in Fig. 6 . The stress distribution of the femur after prosthetic replacement is similar to that of the normal femur. Both the long stem prosthesis and the short stem prosthesis showed a gradual stress nephogram distribution, without serious stress mutation. The stress distribution characteristics of the femur in each model are close to the physiological state. With the increase of the length of the stem, the peak stress of the femur under the two fixation methods shows a gradually decreasing trend. With the increase of the length of the stem, the stress shielding effect of the femur intensifies. Observe the average von Mises stress in different regions of interest, as shown in Fig. 7 (a) and 7 (b). When the femoral stem is implanted, it has a significant impact on the stress distribution of the femur. In the region with stem prosthesis implanted, obvious stress shielding phenomenon can be observed, that is, the stress level in this region is significantly lower than that of the healthy femur. Observe the fretting of the femoral stem under different femoral stem lengths and internal fixation methods, as shown in Fig. 7 (c). Under standing load, the fretting peak of the two fixation methods and different lengths of the femoral stem doesn't exceed 150 µm[ 36 , 37 ], and the fretting peak of the biological fixation femoral stem with stem length of 95mm is the highest. It is observed that the fretting trend of the two fixation methods is similar with the length of the femoral stem. With the increase of stem length, the fretting only increases first, then decreases, and finally increases again. 3.2 Porous Structure Mechanics and Friction Test Analysis According to the experimental results in Fig. 8 , it can be found that the mechanical behaviors of G, D and P structures are different when they are compressed, especially in the yield plateau stage. The D-type structure with porosity of 50%, 60% and 70% all appeared fracture phenomenon when entering the yield plateau stage, indicating that the plastic shape of D-type structure is poor. At lower porosity, p-type structure breaks. When the porosity reaches 70%, it no longer breaks directly, but serrated stress fluctuations occur during compression, indicating that p-type structure has better shaping and energy absorption ability at higher porosity. The G-type structure showed excellent plasticity without fracture at all tested porosities. During the process from yield plateau to densification. Based on the data shown in Fig. 8 , the elastic modulus and yield strength of each sample were calculated, as summarized in Table 3 . In this study, the elastic modulus of femoral cortical bone ranges from 5.8 to 16.92 GPa. A porous structure with an elastic modulus lower than that of cortical bone can effectively reduce the stress shielding effect of the femoral stem. Meanwhile, the yield strength of femoral cortical bone is reported to be between 60 and 180 MPa [ 38 ]. To ensure mechanical safety, the yield strength of the porous structure should exceed that of cortical bone, thereby preventing prosthetic failure under load. Table 3 Mechanical properties of porous structures Type Young’s modulos(MPa) Yield strength(MPa) YG50 5.95 ± 0.15 265.8 ± 11.8 YG60 5.33 ± 0.13 192.2 ± 9.1 YG70 4.68 ± 0.10 147.3 ± 8.7 YD50 7.15 ± 0..16 377.2 ± 15.2 YD60 6.27 ± 0.12 266.9 ± 13.1 YD70 5.52 ± 0.11 204.8 ± 9.6 YP50 5..93 ± 0.14 283.6 ± 11.2 YP60 4.95 ± 0.11 179.9 ± 12.1 YP70 4.04 ± 0.09 134.7 ± 89 Based on the friction test results, the friction coefficients between various porous structures and both cortical and cancellous bone were calculated, as shown in Fig. 9 . The experimental data indicate that the static friction coefficient and the dynamic friction coefficient of each structure are relatively high, showing that these porous structures exhibit favorable interfacial friction properties. Furthermore, an upward trend in friction coefficient is observed with increasing porosity, which is consistent with the findings of Dannaway [ 31 ]. The results also show that, for all structures tested, the friction coefficients with cortical bone are higher than those with cancellous bone, both in terms of static and dynamic friction coefficient. 3.3 Finite element analysis of femoral stem under gait load To simulate the mechanical behavior of patients during slow walking, three representative gait phases (0%, 18%, and 45% of the gait cycle) were selected to evaluate femoral stress distribution based on hip joint contact forces [ 39 ]. At the 0% phase of the gait cycle, the knee joint assumes a slight flexion position, representing the minimum knee flexion angle throughout the cycle. Concurrently, the hip joint contact force begins to increase progressively. At the 18% phase of the gait cycle, the hip contact force reaches its first peak value during the entire cycle, with the hip joint undergoing maximal vertical loading. At the 45% phase of the gait cycle, the hip contact force reaches its second peak. Force analysis at this stage is particularly critical for understanding the loading conditions of the hip joint during the latter half of the gait cycle, which aids in evaluating and optimizing walking stability and joint longevity in patients following hip arthroplasty. Using the gait data obtained from the experiment, joint forces at each gait phase were calculated, and the results are summarized in Table 4 . These loads were then applied to the finite element models of the prostheses. The femoral stress distribution was recalculated for both the traditional biological femoral stem and the porous femoral stem with TPMS structure. The finite element analysis results are showed in Fig. 10 . Through the analysis results of the two prostheses, we can see that the traditional biological femoral stem leads to more pronounced stress shielding, however the porous femoral stem significantly reduces this effect, indicating improved biomechanical performance. Table 4 Gait load Gait cycle Hip contact force(N) F x F y F z 0% 227.8 26.33 553.8 18% 342.5 167.9 1670.1 45% 249.2 -74.7 1644.3 The fretting peak of the femoral stem under gait loading conditions is illustrated in Fig. 11 . The results indicate that, compared to the standing state, gait loading state significantly increases fretting peak. Notably, at the 18% phase of the gait cycle, the fretting peak of the traditional biological femoral stem exceeds 150 µm, which poses a risk of bone–prosthesis integration failure. By contrast, the porous femoral stem with TPMS structure consistently exhibits lower fretting peak across all phases of the gait cycle, with values remaining below the critical threshold of 150 µm. 4. Discussion Finite element analysis of different femoral stem lengths and internal fixation methods reveals that the overall stress distribution of the eight femoral stems is similar, with stress primarily concentrated in the anteromedial and posterolateral regions. As the femoral stem length increases, stress concentration at its distal end gradually intensifies. Under varying fixation methods, stress shielding worsens as the length of the implanted prosthetic femoral stem increases. This phenomenon indicates that the presence of the femoral stem alters the internal stress transmission pathway within the femur, reducing the load borne by the bone tissue in the implanted region. However, when the region of interest (ROI) shifts to an area within the medullary cavity that lacks a stem, femoral stress levels progressively rise, ultimately approaching or matching those of the control group without an implanted prosthesis. The rapid rise in stress levels suggests that the sessile region is less affected by the stress shielding effect and continues to bear relatively normal physiological loads. Across all stem lengths, the peak stress value of bone cement fixation was lower than that of biological fixation, demonstrating that bone cement fixation offers greater initial stability during prosthesis implantation. The femoral isthmus, a relatively narrow section in the mid-femur, plays a crucial role in the stability of prosthesis stem. A comparison of fretting peak analysis results with femoral anatomy reveals that when the stem length reaches 110mm, the distal end of the femoral stem is constrained by the femoral isthmus, creating a close match between the prosthesis stem and the isthmus. This constraint reduces fretting peak at the interface, thereby enhancing prosthesis stability. Based on finite element analysis, the optimal femoral stem length is determined to be 110mm. Through quasi-static compression experiments, it was observed that, compared to G and P structures, the stress-strain curve of the G-type structure does not exhibit zigzag fluctuations but instead increases gradually. This indicates that the G-type structure can maintain structural integrity under compressive loads, providing a more uniform stress distribution and greater plastic deformation capability. By calculating the elastic modulus and yield strength of each structure, it was determined that the Gyroid structure with 60% porosity and the Diamond structure with 70% porosity are suitable as the porous structure of the femoral stem. The design effectively minimizes the stress shielding while ensuring adequate mechanical stability. Furthermore, friction tests revealed that, under the condition of the same porosity, the static and dynamic friction coefficients of the Gyroid structure are higher than those of the other two structures. This indicates superior interface friction properties, allowing the Gyroid structure to provide enhanced initial stability at the bone-implant interface. Finite element analysis using gait data indicates that, under gait loading, the newly designed porous femoral stem in this study outperforms traditional biological femoral stems. It demonstrates significant improvements in reducing stress shielding and fretting peak, offers superior initial stability, and effectively lowers the risk of aseptic loosening. Although the G-type porous structure proposed in this study effectively reduces stress shielding and fretting peak, further optimization of its material composition and structural parameters is necessary to achieve superior biomechanical compatibility and stability. This design concept offers a valuable reference for future optimization of femoral stem structures This study has several limitations. Only a selection of typical TPMS structures was analyzed for the porous design, leaving uncertainty about whether other structures might offer better overall performance. In future research, expanding the range of porous structures and broadening the experimental scope could lead to the identification of a more suitable design for implants. Additionally, due to test conditions and time constraints, the prosthesis stem remains in the simulation analysis phase. To fully evaluate the performance of the new porous knee prosthesis, further biomechanical experiments are necessary. 5. Conclusion This study employs a reverse modeling approach to construct a finite element model for tumor knee joint prosthesis replacement surgery. It analyzes the influence of femoral stem length and fixation methods on stress shielding and initial stability. Additionally, a porous structure is introduced to optimize the femoral stem, with patient data collected through gait experiments. The superiority of the porous femoral stem structure is then compared and verified. The main conclusions are as follows: Impact of femoral stem length and fixation method: Short-stem prostheses help minimize stress shielding, whereas longer femoral stems lead to more pronounced stress shielding effects. Due to its lower elastic modulus, bone cement fixation exhibits less stress shielding. A femoral stem length of 110mm enables tight bonding with the femoral isthmus, reducing fretting peak and enhancing stability. Porous structure optimization: The porous structure, designed using the implicit surface method, exhibits an elastic modulus comparable to cortical bone. The G-type structure with 60% porosity and the D-type structure with 70% porosity demonstrate optimal mechanical properties. In terms of friction performance, the G-type structure outperforms the others, with the friction coefficient of YG60 being superior to that of YD70. This enhances implant stability by reducing fretting peak in the early stage of prosthesis replacement. Gait-based validation of porous femoral stems: Finite element analysis using gait experiments confirms that the newly designed porous biomimetic femoral stem effectively reduces stress shielding and fretting peak, enhances initial stability, and lowers the risk of aseptic loosening. Abbreviations TPMS Triply Periodic Minimal Surface FEM Finite Element Method CNC Computer Numerical Control SLM Selective Laser Melting UHMWPE Ultra-High Molecular Weight Polyethylene ROI Regions Of Interest Declarations Data availability The data used to support the findings of this study are available in the text and can be procured from the corresponding author upon request. Acknowledgements Not applicable. Funding This work was supported by grants from the Natural Science Fund Project of Hebei Province (E2022202164). The sponsors or funders had no involvement in any part of this study. All authors confirmed the independence of researchers from funding sources. The study’s funders had no role in the study design, data collection, analysis, interpretation, or report writing. Author information Authors and Affiliations 1 School of Mechanical Engineering, Hebei University of Technology, Tianjin 300401, China. Peng Shang; Bolong Chen; Fengbin Jin. 2 Department of Bone and soft tissue Oncology, Tianjin University Tianjin Hospital, Tianjin 300211, China. Yancheng Liu 3 School of Energy System, LUT University, Lappeenranta 53850, Finland. Huapeng Wu. Contributions All authors have made substantial contributions to all of the following:(1) the conception and design of the study(Peng Shang, Bo-long Chen, Yan-cheng Liu), (2)acquisition of data(Bo-long Chen, Yan-cheng Liu, Bo-long Chen), (3)analysis and interpretation of data(Peng Shang, Bo-long Chen, Yan-cheng Liu, Feng-bin Jin, Hua-peng Wu), (4)drafting the article or revising it critically for important intellectual content(Peng Shang, Jian-jun Zhang, Hua-peng Wu), and(5) drawing illustrations(Bo-long Chen, Feng-bin Jin). All authors have read and approved the final submitted manuscript. Corresponding author Peng Shang: [email protected] ; Huapeng Wu: [email protected] Ethics declarations Ethics approval and consent to participate The study was reviewed and approved by the Biomedical Ethics Committee of Hebei University of Technology, with the approval number HEBUTMEC2025017. and was performed in accordance with ethical standards laid down in the 1964 Declaration of Helsinki and its later amendments. Informed consent to participate was obtained from all participants included in the study. Consent for publication An informed consent was obtained from all participants to publish the obtained data of the current study. Competing interests The authors declare no competing interests. References Jiang JZ, Pan H, Li MB, Qian B, Lin XF, Fan SW. Predictive model for the 5-year survival status of osteosarcoma patients based on the SEER database and XGBoost algorithm. Sci Rep. 2021;1(1):5542. Misbahuddin, Mujaddid I. 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Analysis of Interface Stress Failure in Unicompartmental Knee Arthroplasty Using Finite Element Method. J Med Biomech. 2022;37(3):473–8. Innocenti B, Bori E, Pianigiani S. Biomechanical analysis of the use of stems in revision total knee arthroplasty. Bioengineering. 2022;9:259. Grant JA, Bishop NE, Götzen N, Sprecher C, Honl M, Morlock MM. Artificial composite bone as a model of human trabecular bone: the implant-bone interface. J Biomech. 2007;40(5):1158–64. Simpson DJ, Little JP, Gray H, Murray DW, Gill HS. Effect of modular neck variation on bone and cement mantle mechanics around a total hip arthroplasty stem. Clin Biomech. 2009;24(3):274–85. Xu KX, Liu W, Cheng X, Pan C, Wang ZG, Yuan ZS, Wang LW. Friction coefficient of a novel bionic trabecular bone. Rare Met Mater Eng. 2021;50(8):2777–82. Luo Y, Yang L, Tian MC. Application of biomedical-grade titanium alloys in trabecular bone and artificial joints. Biomaterials Med Tribology. 2012;191–216. Dannaway J, Dabirrahmani D, Sonnabend D, Martin A, Appleyard R. An investigation into the frictional properties between bone and various orthopedic implant surfaces-implant stability. J Musculoskelet Res. 2015;18(04):1. Benedetti MG, Catani F, Donati D, Simoncini L, Giannini S. Muscle performance about the knee joint in patients who had distal femoral replacement after resection of a bone tumor: an objective study with use of gait analysis. J Bone Joint Surg Am. 2000;82(11):1619–25. Tsuboyama T, Windhager R, Bochdansky T, Yamamuro T, Kotz R. Gait after knee arthroplasty for femoral tumor: foot pressure patterns recorded in 20 patients. Acta Orthop Scand. 1994;65(1):51–4. Kim S, Ryu C, Jung ST. Differences in kinematic and kinetic patterns according to the bone tumor location after endoprosthetic knee replacement following bone tumor resection: a comparative gait analysis between distal femur and proximal tibia. J Clin Med. 2021;10(18):4100. Bori E, Innocenti B. Biomechanical analysis of femoral stem features in hinged revision TKA with valgus or varus deformity: a comparative finite elements study. Appl Sci. 2023;13(4):2738. Engh CA, O'connor D, Jasty M, MCGOVERN TF, BOBYN JD, HARRIS WH. Quantification of implant micromotion, strain shielding, and bone resorption with porous-coated anatomic medullary locking femoral prostheses. Clin Orthop Relat Res. 1992;285(285):13–29. Jasty M, Bragdon C, Burke D, O'Connor D, Lowenstein J, Harris WH. In vivo skeletal responses to porous-surfaced implants subjected to small induced motions. J Bone Jt Surg. 1997;79(5):707–14. Boughton OR, Ma S, Cai X, Yan LY, Peralta L, Laugier P, Marrow J, Giuliani F, Hansen U, Able RL, Grimal Q, Cobb JP. Computed tomography porosity and spherical indentation for determining cortical bone millimetre-scale mechanical properties. Sci Rep. 2019;1(1):7416. Mo FH, Zhang H, Zhao SQ, Xiao Z, Tang L. Coupling musculoskeletal dynamics and subject-specific finite element analysis of femoral cortical bone failure after endoprosthetic knee replacement. Appl Bion Biomech. 2019; 2019: 4650405. Additional Declarations No competing interests reported. Cite Share Download PDF Status: Under Review Version 1 posted Reviewers agreed at journal 09 May, 2026 Reviews received at journal 14 Aug, 2025 Reviewers agreed at journal 12 Aug, 2025 Reviewers invited by journal 30 Jul, 2025 Editor invited by journal 01 Jul, 2025 Editor assigned by journal 30 Jun, 2025 Submission checks completed at journal 30 Jun, 2025 First submitted to journal 30 Jun, 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-6931418","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":494329959,"identity":"319e4484-312b-4354-915b-cc1b1fbef3ba","order_by":0,"name":"Peng Shang","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAA/klEQVRIiWNgGAWjYDACCRiDmfnggw8VEnL8xGthb0s2nHHGwliygWgtPGfMpHnbKhI3ENIiP7v52cOvO2zy5CPSEiRnzpNg3MDA/PDRDTxaDO4cMzeWPZNWbHgj+YDBx20SzOYMbMbGOfi0SCSYSUu2HU7cOCMtIXHmNgk2ywYeNml8WuRnpH8DavkP1JJjcJh3jgSPwQECWhhu5JhJfmw7kDif54xhM2+DhARBLQY3csqkGc8kJ24ABjLjjGMSBpLNBPwCdNg2yZ877BLnNzMf//Ghpq6+n7354WO8DgMCZt4GoHUH4FwCykGA8SdQi3wDESpHwSgYBaNgZAIANEVR2KYtQxAAAAAASUVORK5CYII=","orcid":"","institution":"Hebei University of Technology","correspondingAuthor":true,"prefix":"","firstName":"Peng","middleName":"","lastName":"Shang","suffix":""},{"id":494329960,"identity":"93d6f3f4-fc46-40b0-8a71-985280854d0e","order_by":1,"name":"Bolong Chen","email":"","orcid":"","institution":"Hebei University of Technology","correspondingAuthor":false,"prefix":"","firstName":"Bolong","middleName":"","lastName":"Chen","suffix":""},{"id":494329961,"identity":"b7f5e06f-d438-45fd-9458-eac462672455","order_by":2,"name":"Fengbin Jin","email":"","orcid":"","institution":"Hebei University of Technology","correspondingAuthor":false,"prefix":"","firstName":"Fengbin","middleName":"","lastName":"Jin","suffix":""},{"id":494329962,"identity":"c66c876f-c54f-409f-a83e-581d50b29d5a","order_by":3,"name":"Jianjun Zhang","email":"","orcid":"","institution":"Hebei University of Technology","correspondingAuthor":false,"prefix":"","firstName":"Jianjun","middleName":"","lastName":"Zhang","suffix":""},{"id":494329963,"identity":"26b29ab4-a852-48ec-a6d4-339caa83e1f7","order_by":4,"name":"Yancheng Liu","email":"","orcid":"","institution":"Tianjin University Tianjin Hospital","correspondingAuthor":false,"prefix":"","firstName":"Yancheng","middleName":"","lastName":"Liu","suffix":""},{"id":494329964,"identity":"841c528a-1b55-4ee5-bac1-b957fa732d5c","order_by":5,"name":"Huapeng Wu","email":"","orcid":"","institution":"LUT University","correspondingAuthor":false,"prefix":"","firstName":"Huapeng","middleName":"","lastName":"Wu","suffix":""}],"badges":[],"createdAt":"2025-06-19 12:53:26","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-6931418/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-6931418/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":88339022,"identity":"68e985d6-164e-4d00-acfc-1eab8df5786e","added_by":"auto","created_at":"2025-08-05 12:24:06","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":66621,"visible":true,"origin":"","legend":"\u003cp\u003eEstablishment of knee joint model (a) femur;(b) tibia;(c) fibula;(d) soft tissue;(e) solid model of knee joint\u003c/p\u003e","description":"","filename":"1.png","url":"https://assets-eu.researchsquare.com/files/rs-6931418/v1/8966a3c2e03e56bae2945229.png"},{"id":88339025,"identity":"3f54b233-08ad-4d80-be44-f5f033e43229","added_by":"auto","created_at":"2025-08-05 12:24:06","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":88952,"visible":true,"origin":"","legend":"\u003cp\u003eStructural diagram of tumor-type knee prosthesis (a)Overall Model;(b) Porous femoral stem\u003c/p\u003e","description":"","filename":"2.png","url":"https://assets-eu.researchsquare.com/files/rs-6931418/v1/01e2af2d718ed6ed09ffee79.png"},{"id":88339019,"identity":"f64665eb-48fe-47fd-a41a-682a362e4d53","added_by":"auto","created_at":"2025-08-05 12:24:06","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":557099,"visible":true,"origin":"","legend":"\u003cp\u003eQuasi-static compression test models (a)-(c) are the front right 3D view of YG50, YD60 and YP70; (d)-(f) are the front view of YG50, YD60 and YP70\u003c/p\u003e","description":"","filename":"3.png","url":"https://assets-eu.researchsquare.com/files/rs-6931418/v1/f08d05f38a42538b2a297e15.png"},{"id":88339010,"identity":"726cf541-101e-4b7e-9afe-acb5fd1d62d4","added_by":"auto","created_at":"2025-08-05 12:24:03","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":837921,"visible":true,"origin":"","legend":"\u003cp\u003eSchematic diagram of the experiment (a) Quasi static compression experiment (b) Friction test equipment\u003c/p\u003e","description":"","filename":"4.png","url":"https://assets-eu.researchsquare.com/files/rs-6931418/v1/524ee9c10480d12b90dd1479.png"},{"id":88339086,"identity":"a6f7bd60-48ba-42d2-82f3-1d0fd59aa1ad","added_by":"auto","created_at":"2025-08-05 12:24:08","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":41115,"visible":true,"origin":"","legend":"\u003cp\u003eDivision of the ROI\u003c/p\u003e","description":"","filename":"5.png","url":"https://assets-eu.researchsquare.com/files/rs-6931418/v1/a0a665dc6062fe3ba7fca8f9.png"},{"id":88339100,"identity":"a5d5790d-a53e-4268-ba0a-f3bf8e5aeba0","added_by":"auto","created_at":"2025-08-05 12:24:10","extension":"png","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":353540,"visible":true,"origin":"","legend":"\u003cp\u003eCloud map of finite element analysis results (a)-(d) 80-125mm cement-fixed prostheses were implanted respectively;(e)-(h) implantation of 80-125mm bio-fixed prostheses;(i) stress distribution of femoral stem\u003c/p\u003e","description":"","filename":"6.png","url":"https://assets-eu.researchsquare.com/files/rs-6931418/v1/dbca4c628371b9e0a434ca18.png"},{"id":88339085,"identity":"e93750f8-f92d-4511-96cb-4716ad8480d9","added_by":"auto","created_at":"2025-08-05 12:24:08","extension":"png","order_by":7,"title":"Figure 7","display":"","copyAsset":false,"role":"figure","size":265161,"visible":true,"origin":"","legend":"\u003cp\u003eAnalysis result chart(a) Mean Von Mises stress of cement-fixed ROIs at different stem lengths;(b) Mean femoral ROIs Von Mises stress after bio-fixation with different stem lengths;(c) Peak femoral stem fretting\u003c/p\u003e","description":"","filename":"7.png","url":"https://assets-eu.researchsquare.com/files/rs-6931418/v1/453bc7da9eee6f44b9631c24.png"},{"id":88339037,"identity":"fcd1f3ba-ab71-4201-929f-eda150e06d25","added_by":"auto","created_at":"2025-08-05 12:24:07","extension":"png","order_by":8,"title":"Figure 8","display":"","copyAsset":false,"role":"figure","size":199236,"visible":true,"origin":"","legend":"\u003cp\u003eSress-strain curve of quasi-static compression test\u003c/p\u003e","description":"","filename":"8.png","url":"https://assets-eu.researchsquare.com/files/rs-6931418/v1/89765b27e4335e678320055d.png"},{"id":88339032,"identity":"9679ccf8-d091-442b-8926-82b8e11794f9","added_by":"auto","created_at":"2025-08-05 12:24:07","extension":"png","order_by":9,"title":"Figure 9","display":"","copyAsset":false,"role":"figure","size":44334,"visible":true,"origin":"","legend":"\u003cp\u003eFriction coefficient between TPMS porous structure and bone(a) cortical bone;(b) cancellous bone\u003c/p\u003e","description":"","filename":"9.png","url":"https://assets-eu.researchsquare.com/files/rs-6931418/v1/78dda89ae735c14039cdb9ec.png"},{"id":88339939,"identity":"969c3bb5-a14f-4569-8c64-4cb76cdf2911","added_by":"auto","created_at":"2025-08-05 12:32:06","extension":"png","order_by":10,"title":"Figure 10","display":"","copyAsset":false,"role":"figure","size":584397,"visible":true,"origin":"","legend":"\u003cp\u003eMean Von Mises stresses in the femoral stem ROIs under gait load(a) 0%;(b) 18%;(c) 45%\u003c/p\u003e","description":"","filename":"10.png","url":"https://assets-eu.researchsquare.com/files/rs-6931418/v1/2199252227498adf8a007984.png"},{"id":88339089,"identity":"1b979f3f-1e0d-42ae-bd32-f5714b56d63e","added_by":"auto","created_at":"2025-08-05 12:24:09","extension":"png","order_by":11,"title":"Figure 11","display":"","copyAsset":false,"role":"figure","size":96276,"visible":true,"origin":"","legend":"\u003cp\u003ePeak fem femoral stem micromotion under gait load\u003c/p\u003e","description":"","filename":"11.png","url":"https://assets-eu.researchsquare.com/files/rs-6931418/v1/6ed91a338e734ff284b80db8.png"},{"id":88339962,"identity":"ce7d4891-8808-48f3-9c52-aa45d783eb0f","added_by":"auto","created_at":"2025-08-05 12:32:19","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":3727457,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-6931418/v1/dbddaf35-587c-4cfe-be0e-9673adb561d4.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"Structure Design and Performance Analysis of a Stem for Tumor-type Knee Prosthesis","fulltext":[{"header":"1. Introduction","content":"\u003cp\u003eMalignant bone tumors, such as osteosarcoma, are highly invasive and pose a risk of metastasis. The distal end of the femur is the most common site for the occurrence of such tumors, and the majority of patients are relatively young. With the advancement and standardization of surgical treatments, limb-salvage procedures have shown significantly improved outcomes [\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e]. Metal tumor prostheses have become the preferred method for limb reconstruction due to their immediate stability and favorable short- and long-term functional results [\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e]. However, complications associated with these prostheses remain unresolved [\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e, \u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e]. Among them, aseptic loosening is a major issue, significantly impacting the service life and long-term success of tumor-type prosthetic implants, and is one of the leading causes of prosthesis failure [\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e, \u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e].\u003c/p\u003e\u003cp\u003eMechanical factors such as prosthetic stability and stress shielding contribute to aseptic loosening. Micromotion at the bone\u0026ndash;prosthesis interface affects the initial stability, while the large mismatch in elastic modulus between the prosthesis and natural bone causes stress shielding [\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e, \u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e]. Therefore, optimizing prosthesis structure is essential for improving the therapeutic effectiveness and longevity of artificial implants.\u003c/p\u003e\u003cp\u003eTPMS structures are suitable as porous part of biomedical implant because of the characteristic of high specific surface area and zero mean curvature. The parameterized design can make TPMS structure satisfy different requirement, enabling optimized material distribution and structural performance while providing essential biological compatibility and adequate mechanical strength [\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e]. TPMS structures are generally categorized into two main forms: sheet-like and columnar. Oraib [\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e] and Qin Jiawei [\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e] reported that sheet-like TPMS structures exhibit superior mechanical properties and a higher specific surface area, therefore they can better promote cell proliferation and bone integration. Furthermore, the porosity is critical to balance mechanical strength with biological functionality in porous implants.\u003c/p\u003e\u003cp\u003eThe finite element method (FEM) is regarded as an efficient tool for conducting preoperative plan simulations, which can utilize the imaging data of the lower limbs for preoperative planning and simulation [\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e]. By simulating various loading conditions and using patient-specific anatomical structures, FEM enables implant designs to be refined, reducing the need for extensive experimental testing while enhancing the safety and effectiveness of the prosthesis [\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e].\u003c/p\u003e\u003cp\u003eTraditional computer numerical control (CNC) machining encounters significant limitations when producing complex porous structures. In contrast, selective laser melting (SLM) is an advanced additive manufacturing technique, which is suitable for producing porous implants. It enables the fabrication of intricate three-dimensional porous metal components by melting fine metal powders layer by layer, making it an ideal method for producing customized implants [\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e, \u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e].\u003c/p\u003e\u003cp\u003eTherefore, investigating the length and fixation method of the femoral stem in tumor-type knee prostheses is essential for understanding their influence on aseptic loosening. The femoral stem with porous structures can improve the initial stability of the prosthesis and reduce stress shielding, offering useful reference for the design of improved artificial knee prostheses.\u003c/p\u003e"},{"header":"2. Materials and methods","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e\u003ch2\u003e2.1 Establishment of three-dimensional model of knee joint\u003c/h2\u003e\u003cp\u003eA healthy volunteer with no history of knee joint disease was selected for CT and MRI data acquisition. Bone structures were extracted using Mimics, followed by multiple iterations in Geomagic Wrap to repair the model and correct geometric inconsistencies. In order to create a more reasonable three-dimensional knee joint model, High-resolution and high-contrast MRI images were used to accurately extract and reconstruct the soft tissue. The bone and soft tissue models were assembled in SolidWorks to generate a complete 3D knee joint model, as shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec4\" class=\"Section2\"\u003e\u003ch2\u003e2.2 Establishment of knee prosthesis model\u003c/h2\u003e\u003cp\u003eThe rotating hinge knee tumor prosthesis used in this study was manufactured by Weigao Company and features a modular design. The primary materials used in the prosthesis include titanium alloy, ultra-high molecular weight polyethylene (UHMWPE), and cobalt\u0026ndash;chromium\u0026ndash;molybdenum alloy. Based on CT image analysis, a diameter of 12 mm was determined to be suitable for implantation into the femoral medullary cavity. Accordingly, the diameter of the biologically fixed femoral stem was set at 12 mm. Considering that the ideal bone cement thickness in clinical applications is approximately 2 mm [\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e], the diameter of the cemented femoral stem was designed to be 8 mm.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eTo investigate the effect of femoral stem length on the surrounding bone, four stem lengths were evaluated: 80 mm, 95 mm, 110 mm, and 125 mm. A 1 mm gap was introduced between the femoral stem and the femoral base to avoid incomplete contact and ensure consistent modeling conditions [\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e]. Taking the 110 mm stem as an example, the biologically fixed prosthesis stem consists of an external porous region and an internal solid core, as illustrated in Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec5\" class=\"Section2\"\u003e\u003ch2\u003e2.3 Design of TPMS porous structure model\u003c/h2\u003e\u003cp\u003eTPMS structures can be represented using various methods, including parameterization, boundary representation, and implicit surface functions [\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e]. Among them, implicit surface functions offers a relatively straightforward approach to modeling complex geometries. This study selects three typical TPMS structures\u0026mdash;Gyroid, Diamond, and Primitive\u0026mdash;whose implicit surface equations are showed in Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e. Among them, L represents the size of the TPMS unit cell, and C is used to adjust the bias function of the TPMS structure.\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\u003eEquation of TPMS structure\u003c/p\u003e\u003c/div\u003e\u003c/caption\u003e\u003ccolgroup cols=\"2\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e\u003cp\u003eTPMS\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u003cp\u003eStructural equation\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eG\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e\u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:\\text{c}\\text{o}\\text{s}\\left(\\frac{2\\pi\\:}{L}x\\right)\\text{s}\\text{i}\\text{n}\\left(\\frac{2\\pi\\:}{L}y\\right)+\\text{c}\\text{o}\\text{s}\\left(\\frac{2\\pi\\:}{L}y\\right)\\text{s}\\text{i}\\text{n}\\left(\\frac{2\\pi\\:}{L}z\\right)+\\text{c}\\text{o}\\text{s}\\left(\\frac{2\\pi\\:}{L}z\\right)\\text{s}\\text{i}\\text{n}\\left(\\frac{2\\pi\\:}{L}x\\right)=C\\)\u003c/span\u003e\u003c/span\u003e\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eD\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e\u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:\\text{c}\\text{o}\\text{s}\\left(\\frac{2\\pi\\:}{L}x\\right)\\text{c}\\text{o}\\text{s}\\left(\\frac{2\\pi\\:}{L}\\text{y}\\right)\\text{c}\\text{o}\\text{s}\\left(\\frac{2\\pi\\:}{L}z\\right)-\\text{s}\\text{i}\\text{n}\\left(\\frac{2\\pi\\:}{L}x\\right)\\text{s}\\text{i}\\text{n}\\left(\\frac{2\\pi\\:}{L}y\\right)\\text{s}\\text{i}\\text{n}\\left(\\frac{2\\pi\\:}{L}z\\right)=C\\)\u003c/span\u003e\u003c/span\u003e\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eP\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e\u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:\\text{c}\\text{o}\\text{s}\\left(\\frac{2\\pi\\:}{L}x\\right)+\\text{c}\\text{o}\\text{s}\\left(\\frac{2\\pi\\:}{L}y\\right)+\\text{c}\\text{o}\\text{s}\\left(\\frac{2\\pi\\:}{L}z\\right)=C\\)\u003c/span\u003e\u003c/span\u003e\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\u003eBy adjusting the bias parameter C in the implicit function of TPMS structures, models with different porosities can be generated. This study focuses on three porosity levels \u0026minus;\u0026thinsp;50%, 60% and 70%. The biocompatibility study indicates that when the porosity is around 60%, it can promote bone ingrowth[\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e]. For ease of recording, the 60% porosity Gyroid porous structure is named as YG60. The sample dimensions are set to 10 mm \u0026times; 10 mm \u0026times; 12 mm, with a unit cell size of 2 mm.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec6\" class=\"Section2\"\u003e\u003ch2\u003e2.4 Establishment of finite element model after prosthetic replacement surgery\u003c/h2\u003e\u003cp\u003eThe prosthesis model was assembled with the knee joint model to simulate knee replacement surgery and serve as the basis for subsequent numerical simulations. Due to the complexity of the human skeletal structure and the significant variation in bone material properties, a grayscale assignment method based on CT images [\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e, \u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e] was used to assign material properties to the bone model. Material properties for other components were assigned according to values listed in Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e [\u003cspan additionalcitationids=\"CR23 CR24 CR25\" citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e]. In this study, a Coulomb friction contact condition with a friction coefficient of 0.63 was applied at the bone\u0026ndash;prosthesis interface of the biological prosthesis to simulate the immediate postoperative scenario [\u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e]. At the bone\u0026ndash;cement interface, a bonded contact condition was applied, while a Coulomb friction contact with a coefficient of 0.25 was set at the cement\u0026ndash;prosthesis interface [\u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e]. The simulation modeled the knee joint in full extension under a vertical downward load of 700 N applied at the femoral head to represent the standing position.\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 property parameters\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=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e\u003cp\u003eComponent name\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u003cp\u003eYoung\u0026rsquo;s modulus (MPa)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c3\"\u003e\u003cp\u003ePoisson\u0026rsquo;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\u003eGristle\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e15\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e0.46\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eAnteriior cruciate ligament\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e116\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\u003ePosterior cruciate ligament\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e87\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\u003eMediial lateral cruciate ligament\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e48\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\u003eMeniscus\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e27.5\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e0.33\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eTitanium alloy\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e117\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\u003eUltra-high molecular polyethylene\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e0.685\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e0.4\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eCobalt-chromium-molybdenum alloy\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e220\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\u003eBone cement\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e2280\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\u003c/div\u003e\u003cdiv id=\"Sec7\" class=\"Section2\"\u003e\u003ch2\u003e2.5 Porous Structure Mechanics and Friction Testing\u003c/h2\u003e\u003cp\u003eTo obtain a porous structure that closely matches the elastic modulus of the human femur while ensuring good initial stability, this study conducted quasi-static compression and friction-wear tests on TPMS porous structures. The samples were fabricated using selective laser melting (SLM) technology with Ti-6Al-4V metal powder. Quasi-static compression tests were performed using a C53-195GL electronic universal testing machine, as shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e(a). During compression, the samples were continuously loaded until plastic deformation occurred. The deformation behavior of each sample was monitored, stress-strain curves were generated, and the elastic modulus and yield strength were calculated. A sample with an elastic modulus lower than that of cortical bone can effectively reduce stress shielding in the femoral stem, while a yield strength higher than that of cortical bone helps prevent mechanical failure.\u003c/p\u003e\u003cp\u003eThe friction performance of the porous structure is a critical factor in ensuring the initial stability of the femoral stem. The MZF-1 rotary reciprocating friction and wear tester was used to measure the friction coefficient between cortical bone, cancellous bone, and various TPMS structures, as shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e(b). In the test, the bone pin was prepared from bovine cortical and cancellous bone, with a diameter of 5 mm and a length of 15 mm. An axial load of 30 N was applied between the bone pin and the porous sample. The reciprocating friction speed was set to 5 mm/s, with a stroke length of 20 mm and a total friction duration of 10 minutes. In order to simulate the environment after implantation, bovine serum lubricant at a concentration of 20 g/L was used during testing [\u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e29\u003c/span\u003e]. During the test, the first peak value of the friction coefficient recorded was defined as the static friction coefficient [\u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e30\u003c/span\u003e], and the average friction coefficient during steady-state sliding was defined as the dynamic friction coefficient [\u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e31\u003c/span\u003e].\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003e(b) Friction test equipment\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec8\" class=\"Section2\"\u003e\u003ch2\u003e2.6 Gait test\u003c/h2\u003e\u003cp\u003eGait test provides real motion and loading data from patients who have received total knee arthroplasty. Using these measurements to conduct finite element analysis enables more accurate simulation of physiological conditions and enhans the reliability of the simulation results.\u003c/p\u003e\u003cp\u003eBefore the test, a volunteer who had undergone tumor-type knee prosthesis replacement surgery on the right leg was recruited. Reflective markers were placed on key anatomical landmarks of the lower limbs, including the greater trochanter of the femur (representing the hip joint), the medial and lateral femoral condyles, the patella (for tracking knee joint motion), the medial and lateral malleoli (at the ankle), and key points on the foot. The volunteer was instructed to walk naturally along a path equipped with a force plate. During the test, the Vicon system captured the motion data of lower limbs, while the Kistler force platform recorded the reaction forces from the ground. The collected data were initially screened to identify continuous and stable segments, in order to ensure the validity of subsequent analysis.\u003c/p\u003e\u003cp\u003eMotion data were then processed using OpenSim software to calculate hip joint contact forces during various phases of the gait cycle [\u003cspan additionalcitationids=\"CR33\" citationid=\"CR32\" class=\"CitationRef\"\u003e32\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e34\u003c/span\u003e]. These gait-derived forces were applied as boundary conditions in the finite element model. Finally, the stress shielding and initial stability performances of a conventional biological femoral stem and the optimized porous femoral stem proposed in this study were compared to evaluate the effectiveness of the structural optimization.\u003c/p\u003e\u003c/div\u003e"},{"header":"3. Results","content":"\u003cdiv id=\"Sec10\" class=\"Section2\"\u003e\u003ch2\u003e3.1 Finite element analysis after prosthetic replacement surgery\u003c/h2\u003e\u003cp\u003eTo investigate the influence of different femoral stem lengths and fixation methods on femoral stress distribution, the femur was divided into several regions of interest (ROIs). Finite element analysis was used to calculate the average von Mises stress within each ROI, enabling evaluation of the stress shielding, as illustrated in Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003e [\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e, \u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e, \u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e35\u003c/span\u003e].\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eThe finite element analysis results are shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003e. The stress distribution of the femur after prosthetic replacement is similar to that of the normal femur. Both the long stem prosthesis and the short stem prosthesis showed a gradual stress nephogram distribution, without serious stress mutation. The stress distribution characteristics of the femur in each model are close to the physiological state. With the increase of the length of the stem, the peak stress of the femur under the two fixation methods shows a gradually decreasing trend. With the increase of the length of the stem, the stress shielding effect of the femur intensifies.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eObserve the average von Mises stress in different regions of interest, as shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e7\u003c/span\u003e (a) and 7 (b). When the femoral stem is implanted, it has a significant impact on the stress distribution of the femur. In the region with stem prosthesis implanted, obvious stress shielding phenomenon can be observed, that is, the stress level in this region is significantly lower than that of the healthy femur. Observe the fretting of the femoral stem under different femoral stem lengths and internal fixation methods, as shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e7\u003c/span\u003e (c). Under standing load, the fretting peak of the two fixation methods and different lengths of the femoral stem doesn't exceed 150 \u0026micro;m[\u003cspan citationid=\"CR36\" class=\"CitationRef\"\u003e36\u003c/span\u003e, \u003cspan citationid=\"CR37\" class=\"CitationRef\"\u003e37\u003c/span\u003e], and the fretting peak of the biological fixation femoral stem with stem length of 95mm is the highest. It is observed that the fretting trend of the two fixation methods is similar with the length of the femoral stem. With the increase of stem length, the fretting only increases first, then decreases, and finally increases again.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec11\" class=\"Section2\"\u003e\u003ch2\u003e3.2 \u003cb\u003ePorous Structure Mechanics and Friction Test Analysis\u003c/b\u003e\u003c/h2\u003e\u003cp\u003eAccording to the experimental results in Fig.\u0026nbsp;\u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e8\u003c/span\u003e, it can be found that the mechanical behaviors of G, D and P structures are different when they are compressed, especially in the yield plateau stage. The D-type structure with porosity of 50%, 60% and 70% all appeared fracture phenomenon when entering the yield plateau stage, indicating that the plastic shape of D-type structure is poor. At lower porosity, p-type structure breaks. When the porosity reaches 70%, it no longer breaks directly, but serrated stress fluctuations occur during compression, indicating that p-type structure has better shaping and energy absorption ability at higher porosity. The G-type structure showed excellent plasticity without fracture at all tested porosities. During the process from yield plateau to densification.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eBased on the data shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e8\u003c/span\u003e, the elastic modulus and yield strength of each sample were calculated, as summarized in Table\u0026nbsp;\u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\u003e. In this study, the elastic modulus of femoral cortical bone ranges from 5.8 to 16.92 GPa. A porous structure with an elastic modulus lower than that of cortical bone can effectively reduce the stress shielding effect of the femoral stem. Meanwhile, the yield strength of femoral cortical bone is reported to be between 60 and 180 MPa [\u003cspan citationid=\"CR38\" class=\"CitationRef\"\u003e38\u003c/span\u003e]. To ensure mechanical safety, the yield strength of the porous structure should exceed that of cortical bone, thereby preventing prosthetic failure under load.\u003c/p\u003e\u003cp\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\u003eMechanical properties of porous structures\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=\"\u0026plusmn;\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\"\u0026plusmn;\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e\u003cp\u003eType\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u003cp\u003eYoung\u0026rsquo;s modulos(MPa)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c3\"\u003e\u003cp\u003eYield strength(MPa)\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eYG50\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c2\"\u003e\u003cp\u003e5.95\u0026thinsp;\u0026plusmn;\u0026thinsp;0.15\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c3\"\u003e\u003cp\u003e265.8\u0026thinsp;\u0026plusmn;\u0026thinsp;11.8\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eYG60\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c2\"\u003e\u003cp\u003e5.33\u0026thinsp;\u0026plusmn;\u0026thinsp;0.13\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c3\"\u003e\u003cp\u003e192.2\u0026thinsp;\u0026plusmn;\u0026thinsp;9.1\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eYG70\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c2\"\u003e\u003cp\u003e4.68\u0026thinsp;\u0026plusmn;\u0026thinsp;0.10\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c3\"\u003e\u003cp\u003e147.3\u0026thinsp;\u0026plusmn;\u0026thinsp;8.7\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eYD50\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c2\"\u003e\u003cp\u003e7.15\u0026thinsp;\u0026plusmn;\u0026thinsp;0..16\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c3\"\u003e\u003cp\u003e377.2\u0026thinsp;\u0026plusmn;\u0026thinsp;15.2\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eYD60\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c2\"\u003e\u003cp\u003e6.27\u0026thinsp;\u0026plusmn;\u0026thinsp;0.12\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c3\"\u003e\u003cp\u003e266.9\u0026thinsp;\u0026plusmn;\u0026thinsp;13.1\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eYD70\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c2\"\u003e\u003cp\u003e5.52\u0026thinsp;\u0026plusmn;\u0026thinsp;0.11\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c3\"\u003e\u003cp\u003e204.8\u0026thinsp;\u0026plusmn;\u0026thinsp;9.6\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eYP50\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c2\"\u003e\u003cp\u003e5..93\u0026thinsp;\u0026plusmn;\u0026thinsp;0.14\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c3\"\u003e\u003cp\u003e283.6\u0026thinsp;\u0026plusmn;\u0026thinsp;11.2\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eYP60\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c2\"\u003e\u003cp\u003e4.95\u0026thinsp;\u0026plusmn;\u0026thinsp;0.11\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c3\"\u003e\u003cp\u003e179.9\u0026thinsp;\u0026plusmn;\u0026thinsp;12.1\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eYP70\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c2\"\u003e\u003cp\u003e4.04\u0026thinsp;\u0026plusmn;\u0026thinsp;0.09\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c3\"\u003e\u003cp\u003e134.7\u0026thinsp;\u0026plusmn;\u0026thinsp;89\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\u003eBased on the friction test results, the friction coefficients between various porous structures and both cortical and cancellous bone were calculated, as shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig9\" class=\"InternalRef\"\u003e9\u003c/span\u003e. The experimental data indicate that the static friction coefficient and the dynamic friction coefficient of each structure are relatively high, showing that these porous structures exhibit favorable interfacial friction properties. Furthermore, an upward trend in friction coefficient is observed with increasing porosity, which is consistent with the findings of Dannaway [\u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e31\u003c/span\u003e]. The results also show that, for all structures tested, the friction coefficients with cortical bone are higher than those with cancellous bone, both in terms of static and dynamic friction coefficient.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec12\" class=\"Section2\"\u003e\u003ch2\u003e3.3 Finite element analysis of femoral stem under gait load\u003c/h2\u003e\u003cp\u003eTo simulate the mechanical behavior of patients during slow walking, three representative gait phases (0%, 18%, and 45% of the gait cycle) were selected to evaluate femoral stress distribution based on hip joint contact forces [\u003cspan citationid=\"CR39\" class=\"CitationRef\"\u003e39\u003c/span\u003e]. At the 0% phase of the gait cycle, the knee joint assumes a slight flexion position, representing the minimum knee flexion angle throughout the cycle. Concurrently, the hip joint contact force begins to increase progressively. At the 18% phase of the gait cycle, the hip contact force reaches its first peak value during the entire cycle, with the hip joint undergoing maximal vertical loading. At the 45% phase of the gait cycle, the hip contact force reaches its second peak. Force analysis at this stage is particularly critical for understanding the loading conditions of the hip joint during the latter half of the gait cycle, which aids in evaluating and optimizing walking stability and joint longevity in patients following hip arthroplasty.\u003c/p\u003e\u003cp\u003eUsing the gait data obtained from the experiment, joint forces at each gait phase were calculated, and the results are summarized in Table\u0026nbsp;\u003cspan refid=\"Tab4\" class=\"InternalRef\"\u003e4\u003c/span\u003e. These loads were then applied to the finite element models of the prostheses. The femoral stress distribution was recalculated for both the traditional biological femoral stem and the porous femoral stem with TPMS structure. The finite element analysis results are showed in Fig.\u0026nbsp;\u003cspan refid=\"Fig10\" class=\"InternalRef\"\u003e10\u003c/span\u003e. Through the analysis results of the two prostheses, we can see that the traditional biological femoral stem leads to more pronounced stress shielding, however the porous femoral stem significantly reduces this effect, indicating improved biomechanical performance.\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\u003eGait load\u003c/p\u003e\u003c/div\u003e\u003c/caption\u003e\u003ccolgroup cols=\"4\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003cdiv align=\"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\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\" morerows=\"1\" rowspan=\"2\"\u003e\u003cp\u003eGait cycle\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colspan=\"3\" nameend=\"c4\" namest=\"c2\"\u003e\u003cp\u003eHip contact force(N)\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u003cp\u003eF\u003csub\u003e\u003cem\u003ex\u003c/em\u003e\u003c/sub\u003e\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c3\"\u003e\u003cp\u003eF\u003csub\u003e\u003cem\u003ey\u003c/em\u003e\u003c/sub\u003e\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c4\"\u003e\u003cp\u003eF\u003csub\u003e\u003cem\u003ez\u003c/em\u003e\u003c/sub\u003e\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e0%\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e227.8\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e26.33\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e553.8\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e18%\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e342.5\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e167.9\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e1670.1\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e45%\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e249.2\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e-74.7\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e1644.3\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\u003eThe fretting peak of the femoral stem under gait loading conditions is illustrated in Fig.\u0026nbsp;\u003cspan refid=\"Fig11\" class=\"InternalRef\"\u003e11\u003c/span\u003e. The results indicate that, compared to the standing state, gait loading state significantly increases fretting peak. Notably, at the 18% phase of the gait cycle, the fretting peak of the traditional biological femoral stem exceeds 150 \u0026micro;m, which poses a risk of bone\u0026ndash;prosthesis integration failure. By contrast, the porous femoral stem with TPMS structure consistently exhibits lower fretting peak across all phases of the gait cycle, with values remaining below the critical threshold of 150 \u0026micro;m.\u003c/p\u003e\u003c/div\u003e"},{"header":"4. Discussion","content":"\u003cp\u003eFinite element analysis of different femoral stem lengths and internal fixation methods reveals that the overall stress distribution of the eight femoral stems is similar, with stress primarily concentrated in the anteromedial and posterolateral regions. As the femoral stem length increases, stress concentration at its distal end gradually intensifies.\u003c/p\u003e\u003cp\u003eUnder varying fixation methods, stress shielding worsens as the length of the implanted prosthetic femoral stem increases. This phenomenon indicates that the presence of the femoral stem alters the internal stress transmission pathway within the femur, reducing the load borne by the bone tissue in the implanted region. However, when the region of interest (ROI) shifts to an area within the medullary cavity that lacks a stem, femoral stress levels progressively rise, ultimately approaching or matching those of the control group without an implanted prosthesis.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eThe rapid rise in stress levels suggests that the sessile region is less affected by the stress shielding effect and continues to bear relatively normal physiological loads. Across all stem lengths, the peak stress value of bone cement fixation was lower than that of biological fixation, demonstrating that bone cement fixation offers greater initial stability during prosthesis implantation.\u003c/p\u003e\u003cp\u003eThe femoral isthmus, a relatively narrow section in the mid-femur, plays a crucial role in the stability of prosthesis stem. A comparison of fretting peak analysis results with femoral anatomy reveals that when the stem length reaches 110mm, the distal end of the femoral stem is constrained by the femoral isthmus, creating a close match between the prosthesis stem and the isthmus. This constraint reduces fretting peak at the interface, thereby enhancing prosthesis stability. Based on finite element analysis, the optimal femoral stem length is determined to be 110mm.\u003c/p\u003e\u003cp\u003eThrough quasi-static compression experiments, it was observed that, compared to G and P structures, the stress-strain curve of the G-type structure does not exhibit zigzag fluctuations but instead increases gradually. This indicates that the G-type structure can maintain structural integrity under compressive loads, providing a more uniform stress distribution and greater plastic deformation capability.\u003c/p\u003e\u003cp\u003eBy calculating the elastic modulus and yield strength of each structure, it was determined that the Gyroid structure with 60% porosity and the Diamond structure with 70% porosity are suitable as the porous structure of the femoral stem. The design effectively minimizes the stress shielding while ensuring adequate mechanical stability. Furthermore, friction tests revealed that, under the condition of the same porosity, the static and dynamic friction coefficients of the Gyroid structure are higher than those of the other two structures. This indicates superior interface friction properties, allowing the Gyroid structure to provide enhanced initial stability at the bone-implant interface.\u003c/p\u003e\u003cp\u003eFinite element analysis using gait data indicates that, under gait loading, the newly designed porous femoral stem in this study outperforms traditional biological femoral stems. It demonstrates significant improvements in reducing stress shielding and fretting peak, offers superior initial stability, and effectively lowers the risk of aseptic loosening. Although the G-type porous structure proposed in this study effectively reduces stress shielding and fretting peak, further optimization of its material composition and structural parameters is necessary to achieve superior biomechanical compatibility and stability. This design concept offers a valuable reference for future optimization of femoral stem structures\u003c/p\u003e\u003cp\u003eThis study has several limitations. Only a selection of typical TPMS structures was analyzed for the porous design, leaving uncertainty about whether other structures might offer better overall performance. In future research, expanding the range of porous structures and broadening the experimental scope could lead to the identification of a more suitable design for implants. Additionally, due to test conditions and time constraints, the prosthesis stem remains in the simulation analysis phase. To fully evaluate the performance of the new porous knee prosthesis, further biomechanical experiments are necessary.\u003c/p\u003e"},{"header":"5. Conclusion","content":"\u003cp\u003eThis study employs a reverse modeling approach to construct a finite element model for tumor knee joint prosthesis replacement surgery. It analyzes the influence of femoral stem length and fixation methods on stress shielding and initial stability. Additionally, a porous structure is introduced to optimize the femoral stem, with patient data collected through gait experiments. The superiority of the porous femoral stem structure is then compared and verified. The main conclusions are as follows:\u003c/p\u003e\u003cp\u003e\u003col\u003e\u003cspan\u003e\u003cli\u003e\u003cp\u003eImpact of femoral stem length and fixation method: Short-stem prostheses help minimize stress shielding, whereas longer femoral stems lead to more pronounced stress shielding effects. Due to its lower elastic modulus, bone cement fixation exhibits less stress shielding. A femoral stem length of 110mm enables tight bonding with the femoral isthmus, reducing fretting peak and enhancing stability.\u003c/p\u003e\u003c/li\u003e\u003c/span\u003e\u003cspan\u003e\u003cli\u003e\u003cp\u003ePorous structure optimization: The porous structure, designed using the implicit surface method, exhibits an elastic modulus comparable to cortical bone. The G-type structure with 60% porosity and the D-type structure with 70% porosity demonstrate optimal mechanical properties. In terms of friction performance, the G-type structure outperforms the others, with the friction coefficient of YG60 being superior to that of YD70. This enhances implant stability by reducing fretting peak in the early stage of prosthesis replacement.\u003c/p\u003e\u003c/li\u003e\u003c/span\u003e\u003cspan\u003e\u003cli\u003e\u003cp\u003eGait-based validation of porous femoral stems: Finite element analysis using gait experiments confirms that the newly designed porous biomimetic femoral stem effectively reduces stress shielding and fretting peak, enhances initial stability, and lowers the risk of aseptic loosening.\u003c/p\u003e\u003c/li\u003e\u003c/span\u003e\u003c/ol\u003e\u003c/p\u003e"},{"header":"Abbreviations","content":"\u003cp\u003e\u003cstrong\u003eTPMS \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp;\u0026nbsp;\u003c/strong\u003eTriply Periodic Minimal Surface\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFEM \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp;\u0026nbsp;\u003c/strong\u003eFinite Element Method\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eCNC\u003c/strong\u003e\u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; Computer Numerical Control\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eSLM \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp;\u0026nbsp;\u003c/strong\u003eSelective Laser Melting\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eUHMWPE\u003c/strong\u003e\u0026nbsp; \u0026nbsp; Ultra-High Molecular Weight Polyethylene\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eROI \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp;\u0026nbsp;\u003c/strong\u003eRegions Of Interest\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eData availability\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe data used to support the findings of this study are available in the text and can be procured from the corresponding author upon request.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAcknowledgements\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eNot applicable.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFunding\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThis work was supported by grants from the Natural Science Fund Project of Hebei Province (E2022202164). The sponsors or funders had no involvement in any part of this study. All authors confirmed the independence of researchers from funding sources. The study\u0026rsquo;s funders had no role in the study design, data collection, analysis, interpretation, or report writing.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAuthor information\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAuthors and Affiliations\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e\u003csup\u003e1\u003c/sup\u003eSchool of Mechanical Engineering, Hebei University of Technology, Tianjin 300401, China. Peng Shang; Bolong Chen; Fengbin Jin.\u003c/p\u003e\n\u003cp\u003e\u003csup\u003e2\u003c/sup\u003eDepartment of Bone and soft tissue Oncology, Tianjin University Tianjin Hospital, Tianjin 300211, China. Yancheng Liu\u003c/p\u003e\n\u003cp\u003e\u003csup\u003e3\u003c/sup\u003eSchool of Energy System, LUT University, Lappeenranta 53850, Finland. Huapeng Wu.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eContributions\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eAll authors have made substantial contributions to all of the following:(1) the conception and design of the study(Peng Shang, Bo-long Chen, Yan-cheng Liu), (2)acquisition of data(Bo-long Chen, Yan-cheng Liu, Bo-long Chen), (3)analysis and interpretation of data(Peng Shang, Bo-long Chen, Yan-cheng Liu, Feng-bin Jin,\u0026nbsp;Hua-peng Wu), (4)drafting the article or revising it critically for important intellectual content(Peng Shang, Jian-jun Zhang,\u0026nbsp;Hua-peng Wu), and(5) drawing illustrations(Bo-long Chen, Feng-bin Jin). All authors have read and approved the final submitted manuscript.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eCorresponding author\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003ePeng Shang: [email protected]; \u0026nbsp;Huapeng Wu: [email protected]\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eEthics declarations\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eEthics approval and consent to participate\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe study was reviewed and approved by the Biomedical Ethics Committee of Hebei University of Technology, with the approval number HEBUTMEC2025017. and was performed in accordance with ethical standards laid down in the 1964 Declaration of Helsinki and its later amendments. Informed consent to participate was obtained from all participants included in the study.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConsent for publication\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eAn informed consent was obtained from all participants to publish the obtained data of the current study.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eCompeting interests\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors declare no competing interests.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eJiang JZ, Pan H, Li MB, Qian B, Lin XF, Fan SW. Predictive model for the 5-year survival status of osteosarcoma patients based on the SEER database and XGBoost algorithm. Sci Rep. 2021;1(1):5542.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eMisbahuddin, Mujaddid I. Functional outcome of limb salvage surgery with megaprosthesis in primary bone tumour arround knee. 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Appl Bion Biomech. 2019; 2019: 4650405.\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":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"bmc-musculoskeletal-disorders","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"bmsd","sideBox":"Learn more about [BMC Musculoskeletal Disorders](http://bmcmusculoskeletdisord.biomedcentral.com/)","snPcode":"","submissionUrl":"https://author-welcome.nature.com/12891","title":"BMC Musculoskeletal Disorders","twitterHandle":"BMC_series","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"stoa","reportingPortfolio":"BMC Series","inReviewEnabled":true,"inReviewRevisionsEnabled":true},"keywords":"Femoral stem, Structural design, Finite element analysis, TPMS, SLM","lastPublishedDoi":"10.21203/rs.3.rs-6931418/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-6931418/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003e\u003cstrong\u003eBackground: \u003c/strong\u003eAfter undergoing tumor-type knee prosthesis replacement, patients with bone tumor in the distal femur may experience aseptic loosening on the femoral side, potentially resulting in implant failure. Compared with the traditional bone cement fixation method, the biological fixation can ensure the long-term stability of the prosthesis. To reduce stress shielding of the biologically fixed femoral stem and enhance its initial stability, this study focuses on the structural design and performance analysis of porous femoral stem.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eMethod: \u003c/strong\u003eThe three-dimensional model of the knee joint was constructed using inverse modeling, and the finite element models were established for prosthetic replacements featuring various femoral stem lengths and fixation methods. The fretting of the femoral stem was designed based on a triply periodic minimal surface (TPMS) structure. To determine the most suitable TPMS structure, quasi-static compression and friction test were performed. Additionally, gait experiments were conducted to collect patient-specific data, using for the loading of the finite element analysis.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eResult: \u003c/strong\u003eBoth fixation methods exhibited stress shielding, and it increased with greater stem length. Constraining the top of the femoral stem at the femoral isthmus was found to reduce the fretting of the femoral stem. Experimental results showed that the Gyroid structure with 60% porosity demonstrated higher yield strength and friction coefficient, furthermore it maintained an elastic modulus comparable to that of natural bone tissue. Based on data collected from gait experiment, finite element analysis showed that porous femoral stems can effectively reduce stress shielding and fretting.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConclusion: \u003c/strong\u003eThe new type of femoral stem with porous structure can effectively reduce stress shielding and enhance initial stability, providing a valuable reference for future femoral stem design.\u003c/p\u003e","manuscriptTitle":"Structure Design and Performance Analysis of a Stem for Tumor-type Knee Prosthesis","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-08-05 12:23:27","doi":"10.21203/rs.3.rs-6931418/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"reviewerAgreed","content":"86585216636767956711279688625337087942","date":"2026-05-09T15:11:57+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-08-15T02:25:18+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"113903736586847366548598303806009592694","date":"2025-08-13T02:18:14+00:00","index":"hide","fulltext":""},{"type":"reviewersInvited","content":"","date":"2025-07-30T10:32:03+00:00","index":"","fulltext":""},{"type":"editorInvited","content":"","date":"2025-07-01T17:20:23+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2025-06-30T17:02:05+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2025-06-30T07:35:36+00:00","index":"","fulltext":""},{"type":"submitted","content":"BMC Musculoskeletal Disorders","date":"2025-06-30T07:32:10+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"bmc-musculoskeletal-disorders","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"bmsd","sideBox":"Learn more about [BMC Musculoskeletal Disorders](http://bmcmusculoskeletdisord.biomedcentral.com/)","snPcode":"","submissionUrl":"https://author-welcome.nature.com/12891","title":"BMC Musculoskeletal Disorders","twitterHandle":"BMC_series","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"stoa","reportingPortfolio":"BMC Series","inReviewEnabled":true,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"7e72e621-63b2-487f-bcc1-47794aa88d7f","owner":[],"postedDate":"August 5th, 2025","published":true,"recentEditorialEvents":[{"type":"reviewerAgreed","content":"86585216636767956711279688625337087942","date":"2026-05-09T15:11:57+00:00","index":100,"fulltext":""}],"rejectedJournal":[],"revision":"","amendment":"","status":"under-review","subjectAreas":[],"tags":[],"updatedAt":"2025-08-05T12:23:27+00:00","versionOfRecord":[],"versionCreatedAt":"2025-08-05 12:23:27","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-6931418","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-6931418","identity":"rs-6931418","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}