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Learn more: PMC Disclaimer | PMC Copyright Notice BMC Biotechnol . 2026 Mar 5;26:45. doi: 10.1186/s12896-026-01126-0 Search in PMC Search in PubMed View in NLM Catalog Add to search Mechanical and biological properties of trabecula and strut scaffolds in bone defect reconstruction Linlin Liu Linlin Liu 1 School of Integrated Circuits, Chongqing University of Posts and Telecommunications, Chongqing, 400065 China Find articles by Linlin Liu 1 , Shuxian Wang Shuxian Wang 1 School of Integrated Circuits, Chongqing University of Posts and Telecommunications, Chongqing, 400065 China Find articles by Shuxian Wang 1, ✉ , Xin Wang Xin Wang 1 School of Integrated Circuits, Chongqing University of Posts and Telecommunications, Chongqing, 400065 China Find articles by Xin Wang 1 , Juncai Liu Juncai Liu 2 Department of Orthopaedics, Sichuan Provincial Laboratory of Orthopaedic Engineering, The Affiliated Hospital of Southwest Medical University, Luzhou, Sichuan 646000 China Find articles by Juncai Liu 2 Author information Article notes Copyright and License information 1 School of Integrated Circuits, Chongqing University of Posts and Telecommunications, Chongqing, 400065 China 2 Department of Orthopaedics, Sichuan Provincial Laboratory of Orthopaedic Engineering, The Affiliated Hospital of Southwest Medical University, Luzhou, Sichuan 646000 China ✉ Corresponding author. Received 2025 Nov 25; Accepted 2026 Feb 25; Collection date 2026. © The Author(s) 2026 Open Access This article is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License, which permits any non-commercial use, sharing, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if you modified the licensed material. You do not have permission under this licence to share adapted material derived from this article or parts of it. The images or other third party material in this article are included in the article’s Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http://creativecommons.org/licenses/by-nc-nd/4.0/ . PMC Copyright notice PMCID: PMC13069813 PMID: 41781914 Abstract Background Different porous structures have different mechanical and biological properties in bone defect repair, and different types of porous structures should be applied in different scenarios. In this paper, trabecula scaffolds and strut scaffolds under different porosity conditions were designed and fabricated by 3D printing. Their mechanical and biological properties were studied, and their fluid characteristics were analyzed using computational fluid dynamics (CFD). Results The results showed that the yield strength of the strut scaffold was higher than that of the trabecula scaffold, and the strut scaffold was subjected to uniform force, with the maximum stress being much smaller than that of the trabecula scaffold under the same force. The bone ingrowth performance of the trabecula structure scaffold was better than that of the strut scaffold. CFD analysis indicated that the trabecula scaffold had more fluid flow areas inside and provided greater mechanical stimulation to the pillars, which was conducive to bone tissue growth. Conclusion The study demonstrated that different types of porous structures could be selected based on the characteristics of different implantation sites when designing porous scaffolds, thereby maximizing the advantages of 3D printed porous scaffolds. Keywords: Bone scaffold, Mechanical property, Bone ingrowth, Permeability Background Amputation surgery is one of the best methods for treating large bone defects [ 1 , 2 ]. The commonly used implant materials for limb salvage surgery include autologous bone, allogeneic bone grafts, and artificial prostheses. Compared to autologous bone and allogeneic bone, artificial prostheses have a more stable source and a lower risk of disease transmission, making them excellent implant materials [ 3 ]. However, the artificial implants prepared by traditional manufacturing methods are made of pure metals, and their elastic modulus is much higher than that of the host bone. In a mechanical system composed of two materials with different elastic moduli, when subjected to force, the load is redistributed. The material with the higher elastic modulus bears more load, while the material with the lower elastic modulus does not receive the expected mechanical stimulation, which results in the stress shielding effect of bone tissue [ 4 , 5 ]. At the same time, the solid metal cannot allow bone tissue cells to grow into the interior of the scaffold, which affects the bone integration performance of the scaffold [ 6 , 7 ]. Compared with the traditional manufacturing methods, 3D printing technology can produce more complex shape structures. Therefore, it can achieve personalized customization for patients in the medical field and has broad applications in medical field [ 8 , 9 ]. The porous titanium alloy bone scaffolds fabricated by 3D printing have shown excellent results in repairing large bone defects. Currently, they have been applied in clinical practice [ 10 , 11 ]. Numerous studies have confirmed that the porous titanium alloy (Ti6Al4V) scaffolds prepared by the selective laser melting (SLM) process exhibit excellent bone integration properties [ 12 , 13 ]. The elastic modulus of dense titanium alloy is 110 GPa, which is much higher than that of human bone tissue, when implanting into bone tissue, the elastic modulus of the bone needs to be considered. A suitable porous structure should be designed to match the mechanical and biological properties of the host bone. The porosity and internal structure of the bone scaffold’s porous structure have significant impacts on its mechanical properties and the performance of bone tissue ingrowth [ 14 ]. The trabecular scaffold is designed based on the structure of natural trabeculae. Based on the Voronoi method, it simulates the randomness of the bone trabecular pillars by randomly generating points in space, thereby enhancing the ability of bone cells to grow and multiply [ 15 , 16 ]. The strut scaffold is a porous scaffold obtained by arranging a regular porous structure array. The pillars within the structure have a definite direction, and the arrangement of the pillars is regular, with excellent mechanical properties [ 17 – 19 ]. Regarding the reasons for the influence of geometry and porosity on scaffold biological performance, studies have shown that it is related to the wall shear stress (WSS) within the pores and the fluid flow conditions [ 20 , 21 ]. The fluid distribution within the porous scaffold can be studied via computational fluid dynamics (CFD), and the mechanism of bone tissue cells grow into the interior of the scaffold due to the porous structure can be investigated [ 22 , 23 ]. For load-bearing bones such as the femur, the cortical bone portion is the main area subjected to force, while the cancellous bone portion has lower strength. When performing bone scaffold implantation, we hope that the porous scaffold at the implantation site can not only have a good mechanical match with the host bone, but also have good bone ingrowth characteristics to achieve long-term implantation. Trabecula scaffold and strut scaffold have significant differences in mechanical performance and bone ingrowth performance [ 24 – 26 ]. Separate studies on the two types of porous structures have both demonstrated that their structures can be used for bone defect repair. However, under the same experimental conditions, the differences in mechanical properties and bone integration performance between these two scaffolds and the resulting differences in the applicable scenarios and sites of the two scaffolds, have not yet been thoroughly studied. In this paper, we compared and analyzed the mechanical properties and bone ingrowth conditions involved in the bone defect repair process of the trabecula scaffold and the strut scaffold. Using 3D printing technology, we prepared bone implant samples and compression test samples of the two scaffolds under different porosity conditions. We analyzed the mechanical properties of the porous scaffolds using mechanical compression experiments and finite element analysis, and evaluated the bone ingrowth conditions of different scaffolds by implanting them into the femoral condyles of rabbits. We also calculated the fluid flow of the porous structure using computational fluid dynamics (CFD) to analyze the reasons for the bone tissue ingrowth affected by the porous structure. This paper aims to study the different mechanical and biological characteristics of the trabecula scaffold and the strut scaffold in bone defect repair, and provide theoretical support for the design of scaffolds for large bone defect repair. Materials and methods Design of porous bone scaffolds Previous studies have shown that 3D-printed porous titanium alloy scaffolds with a porosity ranging from 40% to 80% can be used for bone defect repair [ 27 , 28 ]. To investigate the matching of mechanical and biological properties of the scaffolds with bone tissue under different porosity conditions, we selected three representative porosities of 50%, 60%, and 70% for our study. The strut scaffold is a regular structure. We used the NX10.0 software to change the diameter of the pillars to alter the porosity rate, with the unit size being 2 × 2 × 2 mm. The trabecula scaffold generates twenty random points in a 2 × 2 × 2 mm space, connects the random points using the Voronoi method, and changes the porosity rate by controlling the diameter of the pillars [ 29 , 30 ]. Two models of porous structures are shown in Fig. 1 . Fig. 1. Open in a new tab Models of the trabecula scaffold and the strut scaffold Mechanical properties analysis of porous bone scaffolds In order to analyze the stress-strain conditions of the two porous scaffold structures under quasi-static compression conditions, we designed a rectangular scaffold for the mechanical experiment. The sample was prepared using the SLM process, with the metal powder being Ti6Al4V. The experimental samples were fabricated on the XDM 120 equipment (Suzhou XDM 3D Printing Technology Co., Ltd.) using the SLM process. This equipment has a minimum spot diameter of 55 μm and a layer thickness of 20 μm. Laser system is Yb fibre laser, Laser power is 500 W. According to the ISO13314:2011 standard, rectangular supports ( n = 3, 10 × 10 × 10 mm) were subjected to compression experiments on a universal mechanical testing machine (MIT-100, Changzhou Sanfeng Instrument Technology Co., Ltd). To achieve quasi-static compression, the pressure head was pressed down at a speed of 1 mm/min. Data on the displacement of the pressure head during the compression process and the corresponding force magnitude at different times were obtained from the testing machine, and these were converted into stress-strain curves. The yield strength of the porous structure support was obtained from the stress-strain curves. The initial stage of the stress-strain curve represents the elastic deformation phase. Here, 0.2% of the strain offset value is taken as the yield point of the sample, and the slope of the elastic deformation phase represents the equivalent elastic modulus value of the sample, as shown in Fig. 2 . Fig. 2. Open in a new tab ( a ) Compression experimental setup; ( b ) Representative stress-strain curve diagram Simulation analysis of compressive stress conditions of porous structures In order to study the mechanical properties of the two porous structures under different porosity conditions, we used Ansys Workbench software to conduct force analysis on the two porous structures and investigate the stress distribution within them. To ensure that the scaffold could be uniformly stressed, we added rigid plates at the upper and lower ends of the porous scaffold. In the previous experiments on porous structure mechanics, we found that the scaffold in the compression direction remained in the elastic deformation stage when the strain was relatively small. To simulate the process of the mechanical experiment, in the mechanical simulation, a downward compression displacement was applied to the upper plate, while the lower plate was completely fixed. The contact between the rigid plate and the porous scaffold is set as bonded constraint. During the simulation calculation, we assume that the titanium alloy material is an isotropic homogeneous material with an elastic modulus of 110 GPa and a Poisson’s ratio of 0.3 [ 31 ]. The simulation calculation is a static analysis. We only simulated the stress conditions of the porous titanium alloy scaffold during the elastic stage, without considering the plastic deformation stage. The solution was carried out using the linear mechanical solver in ANSYS. Therefore, the density of the material, yield strength, and deformation constitutive model were not involved in this analysis. Regarding the selection of the number of porous structure units for simulation calculations, in order to obtain the stress distribution within and between the structural units, while taking into account the computing capacity and time of the computer, we only selected two units in each direction of the 3D space for simulation calculations. Our previous research results have shown that the shape and size of the units have a relatively small impact on the calculation results in the simulation calculations [ 27 ]. The load and boundary conditions of the mechanical simulation analysis are shown in Fig. 3 . Using Eq. ( 1 ), calculate the elastic modulus (E) of the porous scaffold in the simulation: 1 Fig. 3. Open in a new tab Boundary conditions for porous scaffold simulation where: is stress; is strain; F represents the force exerted on the scaffold; A is the surface area of the force application plane 90; is the displacement along the force direction after compression; L is the total length of the scaffold in the compression direction. Computational fluid analysis of porous structures The fluid flow within the porous structure can be analyzed to understand the flow of oxygen and nutrients within the porous structure, thereby enabling the study of the bone ingrowth within different porous structures [ 3 ]. Using the ANSYS Fluent software, the fluid velocity inside the structure, wall shear stress (WSS), and the fluid flow conditions can be analyzed. Since the porous structure is a lattice structure, the internal structure of each unit is consistent. To save computing time, we only selected two units for the calculation. At the same time, to reduce the boundary effect of the fluid, we added a 0.2 mm thick inlet fluid domain on the fluid domain. The computational fluid mechanics boundary conditions and load conditions for the porous structure are shown in Fig. 4 . The inlet velocity of the fluid in the fluid domain is 0.1 mm/s, the outlet velocity is set to 0, and the wall is set to no slip [ 32 ]. The pressure difference generated by the fluid flowing through the porous structure is obtained by subtracting the pressure at plane B from the pressure at plane A. Assuming that the fluid is incompressible, the calculation is carried out using the Navier-Stokes equation, as shown in Eq. ( 2 ). 2 Fig. 4. Open in a new tab CFD analysis model where: represents the fluid density (kg/m³); v is the fluid velocity (m/s); t is time (s); µ is the hydrodynamic viscosity (kg/m/s); ∇p is the pressure difference (MPa); F is force (N). The permeability of the porous structure is calculated using Eq. ( 3 ): 3 where: Q, L, A and ∆P represent the inlet fluid flow rate (m 3 /s), model length (m), inlet cross-sectional area (m 2 ) and pressure difference (MPa) respectively. When the simulated fluid flows through the internal structure of the porous scaffold, we utilize the fluid characteristics of the porous structure when water flows through it, where the liquid parameters of the water at 37℃ (µ = 0.001 kg/m/s; ρ = 1000 kg/ m 3 ). Evaluation of bone growth in scaffold Surgical procedures This animal experiment was conducted at the Animal Experiment Center of Southwest Medical University, and the experimental animals were also obtained from this center. The prepared cylindrical scaffolds ( n = 3, ∅5 × 8 mm) were implanted into the femoral condyles of rabbits, and the bone ingrowth conditions of the two scaffolds under different porosity conditions were analyzed. This animal experiment was conducted in the Animal Experiment Center of Southwest Medical University and was approved by the Ethics Committee of Southwest Medical University. Eighteen three-month-old New Zealand white rabbits (weighing 2.5–3.0 kg) were randomly divided into two groups, with 9 rabbits in each group. The 18 femoral condyles of each group were respectively corresponding to two time points: 4 weeks and 12 weeks. Before the animal experiment, all the scaffolds and surgical instruments were sterilized using steam at 120℃. The rabbits were anesthetized with 3% pentobarbital sodium (30 mg/kg), and then round column scaffolds were randomly implanted in the left and right femoral condyles of the rabbits. After marking, the wounds were sutured. The animal experiment process is shown in Fig. 5 . After the scaffolds were implanted, all the animals were kept separately and treated with penicillin for three days. At the corresponding time points of each group (4 weeks and 12 weeks), the corresponding rabbits were euthanized by air embolism to prevent the situation where the rabbits did not die due to insufficient anesthesia dosage. The femurs were extracted, and the entire femurs were immersed in 10% formalin for fixation for further analysis. Fig. 5. Open in a new tab ( a ) A rabbit’s femoral condyle was drilled and a porous scaffold was implanted; ( b ) The wound was sutured Micro-CT reconstruction Microcomputed tomography (Micro-CT) System (SCANCO Medical, Switzerland) was used to reconstruct the 3D scaffold and the surrounding bone tissue. During the scanning process, the X-ray source voltage is 90 kV, the beam current is 200 µA, and the resolution is 17.2 μm. The CT data obtained after scanning is then imported into the Mimics 21.0 (Materialise, Belgium) software for 3D reconstruction. The Bone volume (BV) value is measured using the 3D reconstructed model, and the ratio of BV to total void volume (TV) is used to evaluate the quality of bone ingrowth. The higher the BV/TV value, the better the bone ingrowth performance of the corresponding porous structure scaffold. Histological evaluation Hard tissue sections of the samples taken from the animal experiments were prepared using a slicing machine (SP1600, Leica, Germany). Make slices along the longitudinal direction of the cylinder, with a thickness of 50 μm. Subsequently, they were stained with Van-Gieson (1.2% Trinitrophenol and 1% acid Fuchsin) and observed under an optical microscope (DMLA, Leica, DM2500, Germany). Statistical analysis All the data were expressed as mean ± standard deviation and analyzed with the one-way analysis of variance (ANOVA). In all cases, the results were considered statistically significant with a p-value less than 0.05. Results Characterization of scaffold As shown in Fig. 6 , it is the porous structure scaffold fabricated by the SLM process. Figure 6 (a) is the sample from the animal experiment, and Fig. 6 (b) is the sample for the mechanical compression experiment. At the same time, we scanned the samples using Micro-CT and reconstructed the 3D model, as shown in Fig. 6 (c). From the figure, it can be seen that the porous structure samples fabricated by the SLM process well reproduce the design model, have a good pore structure, and can be used for subsequent experiments. Fig. 6. Open in a new tab ( a ) Animal experiment sample; ( b ) Mechanical experiment sample; ( c ) Micro-CT 3D reconstruction model As shown in Table 1 , the designed values and the 3D reconstruction values of the porosity of different scaffold structures are presented. From the table, it can be seen that the reconstructed porosity is less than the designed value, but the difference is within 5%. Table 1. Comparison of designed values of different structural porosity with CT reconstruction values Scaffold type Trabecula-50% Trabecula-60% Trabecula-70% Strut-50% Strut-60% Strut-70% Design porosity 50% 60% 70% 50% 60% 70% Micro-CT reconstruction 44% 56% 67% 46% 56% 68% Open in a new tab Compressive mechanical properties of the scaffold Figure 7 shows the compressive stress-strain curves of the two types of scaffolds under different porosity levels. As can be seen from the figure, as the porosity increases, the elastic modulus and yield strength of both porous structures decrease. At a porosity of 50% and 60%, the yield strength of the strut scaffold is significantly higher than that of the trabecula structure. At a porosity of 70%, the yield strength and equivalent elastic modulus of the two porous structures do not differ much. Fig. 7. Open in a new tab Stress-strain curves of trabecular structure and strut scaffold at different porosity levels As shown in Table 2 , the different elastic modulus (E) values of the porous scaffolds obtained from simulation analysis and experimental measurement are presented. is the displacement of the scaffold along the direction of force applied as measured by the simulation analysis. Table 2. The simulation results and experimental results of the elastic modulus of different porous scaffolds Scaffold type Trabecula-50% Trabecula-60% Trabecula-70% Strut-50% Strut-60% Strut-70% Simulation 0.00064 0.00095 0.0013 0.00058 0.00091 0.0014 Simulation E/GPa 19.5 13.2 9.6 21.5 13.7 8.9 Experiment E/GPa 3.3 2.1 1.5 3.6 2.9 1.6 Open in a new tab Compression simulation results Before the simulation analysis, we first conducted a mesh sensitivity analysis. Figure 8 (a) shows the stress cloud diagrams of the Strut-70% scaffold with mesh numbers of 5,057 and 15,787. From the figure, it can be seen that the maximum stress varies slightly under different mesh numbers, but the difference is small. The overall stress cloud distribution of the porous structure is consistent. Therefore, the subsequent simulation calculations can be conducted using fewer meshes for analysis and calculation. As shown in Fig. 8 (b), the compressive stress cloud diagrams of different structures under porosities of 50%, 60%, and 70% are presented. From the figure, it can be seen that for the strut scaffold, when under pressure, the pillars along the longitudinal direction of the force bear the main stress, while the internal inclined pillars bear less stress. For the trabecula scaffold, the longitudinal pillars along the force direction also bear a large amount of stress, but the force differences of the internal pillars are relatively large. There is no significant difference in the yield strength between the two structures with a porosity of 70%. Fig. 8. Open in a new tab ( a ) Stress maps of the Strut-70% scaffold under different grid configurations; ( b ) Compression stress contour maps of different porosities of trabecular scaffold and strut scaffold As shown in Fig. 9 , it is a local magnified image of the stress cloud map of the porous scaffold under pressure. Overall, the maximum stress of the strut’s porous scaffold is much lower than that of the trabecula porous scaffold. The maximum stress of the strut scaffold occurs on the longitudinal pillars along the force direction, while the pillar of the trabecula porous scaffold is not uniformly stressed and has a large difference in stress. The maximum stress occurs at the intersection of the pillars. This may be due to the irregularity of the trabecula porous scaffold itself. When the same force is applied to different parts, the irregularity of the structure leads to larger local stress. Fig. 9. Open in a new tab Partial enlarged view of the porous scaffold CFD Simulation Results As shown in Fig. 10 , the wall shear stress (WSS) contour maps of the two porous structures under porosity rates of 50%, 60%, and 70% are presented. From the figure, it can be observed that the WSS on the top of the pillar of strut scaffold is relatively large, while the WSS of the trabecula scaffolds is evenly distributed on each pillar. Fig. 10. Open in a new tab WSS contour map within the porous structure As shown in Fig. 11 , the pressure drops and permeability from the inlet to the outlet under different porosity conditions of the two porous structures were calculated using CFD. From the figure, it can be seen that as the porosity increases for both scaffolds, the pressure drop of the porous structure decreases, indicating that as the porosity increases, the internal obstruction of the porous structure decreases, and at the same time, the permeability also increases. Fig. 11. Open in a new tab CFD calculations of different porous structures: ( a ) pressure drop; ( b ) permeability As shown in Fig. 12 , the internal fluid flow patterns under different porosity conditions of the two types of scaffolds are presented. The internal fluid flow patterns in the porous structure indicate the fluid flow situation within the structure. From the figure, it can be seen that the internal fluid flow patterns of the trabecula scaffold are more complex than those of the strut scaffold. The fluid has flowed through more areas and the fluid path is not regular. Fig. 12. Open in a new tab Flow lines of fluid inside the porous scaffold Result of bone ingrowth As shown in Fig. 13 (a), it is a 3D reconstruction diagram of the data obtained from Micro-CT scanning using Mimics 21.0 software. The green part in the figure represents the porous structure scaffold, and the purple part represents the bone tissue. Figure 13 (b) shows the 3D reconstruction cross-sectional view of the porous scaffold. It can be seen from the figure that as time increases, the bone tissue grows gradually from the outside to the inside, and the bone tissue also gradually fills the pores of the porous structure. Figure 13 (c) shows the BV/TV values of different porous structures when implanted for 4 weeks (4 W) and 12 weeks (12 W). Fig. 13. Open in a new tab ( a ) 3D reconstruction images of the porous structure when implanted with 4 W and 12 W by Micro-CT; ( b ) Cross-sectional images of 4 W and 12 W porous scaffolds reconstructed by Micro-CT 3D reconstruction images; ( c ) The BV/TV values of the scaffold when implanted with 4 W and 12 W (* p < 0.05 compared with Trabecula 50%, ** p < 0.05 compared with Trabecula 50%) As shown in Fig. 14 , the VG staining images of different porous structures implanted into the femoral condyles of rabbits at 4 W and 12 W are presented. From the figure, it can be seen that the bone tissue cells have grown into the interior of the scaffold and have a good affinity with the scaffold material. Here, we present the staining images of the edge and the center regions of the scaffold. The growth of the bone tissue in the images is basically consistent with the 3D reconstruction shown in Fig. 13 (b). The growth of the bone tissue within the scaffold is not uniform and will change according to the structure and porosity of the scaffold. Fig. 14. Open in a new tab VG staining plots of hard tissue sections of scaffolds with different parameters at 4 W and 12 W. (The scaffold is shown in black, and the new bone tissue cells are displayed in purple. The black part is the scaffold, the pink part is the new bone, and the fibrous tissue is shown in blue, the scale bars is 500 μm) Discussion This paper investigates the mechanical and biological properties of trabecula scaffolds and strut scaffolds when their porosity is 50%, 60%, and 70%. The designed porous scaffolds were fabricated using the SLM process, and the fabricated scaffolds were evaluated by Micro-CT scanning. The excellent porous structure reconstruction shown in Fig. 6 (c) indicates that the SLM process can successfully fabricate the porous scaffolds. Therefore, the porous scaffolds fabricated by SLM technology have gained increasing popularity among researchers and are increasingly being applied in clinical application [ 33 ]. Table 2 presents the comparison between the simulation analysis and the experimental results of the E of different porous scaffolds. From the table, it can be seen that the E value obtained from the simulation analysis is much higher than that from the experiment. This is because the simulation modeling assumes that the porous scaffolds have no manufacturing defects, while the scaffolds used in the experiment were prepared by 3D printing, and the surface of the pillars would have voids and un-melted metal particles, which would significantly reduce their mechanical properties [ 34 , 35 ]. In the stress cloud diagram of the porous structure in Fig. 8 (b), we can observe that the stress distribution of the trabecula scaffold is uneven, and the stress of the internal pillars varies greatly. This is related to the random arrangement of the internal pillars and the stress concentration formed by the intersection of the pillars. The local magnification diagram in Fig. 9 also illustrates this point. For the strut scaffold with regular arrangement of internal pillars, the stress distribution is relatively uniform, and thus, under the same load conditions, the maximum stress of the pillar support is much smaller than that of the trabecula scaffold. As shown in Fig. 9 , at porosities of 50%, 60%, and 70%, the maximum stress of the trabecula scaffold is 52 MPa, 134.6 MPa, and 145 MPa, respectively, while the maximum stress of the strut scaffold under the same porosity is 23.6 MPa, 35.3 MPa, and 54.6 MPa. It can be seen that as the porosity increases, the difference in the maximum stress between the two scaffold also becomes larger, indicating that the strut scaffold has better compressive resistance. The 3D-printed porous scaffold will first develop cracks at the stress concentration areas when subjected to force, and then the cracks will spread, eventually leading to failure [ 36 ]. Therefore, when selecting the scaffold, not only the elastic modulus but also the stress distribution situation should be taken into account [ 37 ]. Figure 10 shows the internal WSS cloud diagrams of different structures. Under the same porosity conditions, the WSS of the trabecula scaffold is significantly greater than that of the strut scaffold. This indicates that under the same circumstances, the wall surface of the trabecula scaffold generates greater stress with the fluid. WSS has been proven to stimulate the growth and differentiation of bone tissue cells. Therefore, it is reasonable to believe that the trabecula scaffold can provide better stimulation for cell growth [ 20 , 38 ]. From the pressure drop graph in Fig. 11 (a), it can be seen that the pressure drop from the inlet to the outlet of the trabecula scaffold is higher than that of the strut scaffold under all three porosity conditions, indicating that the internal structure of the trabecula scaffold poses greater resistance to the flow of fluids. Correspondingly, the permeability of the trabecula scaffold is smaller than that of the strut scaffold under the same porosity conditions. Permeability reflects the ability of fluids to transport oxygen and nutrients within the porous structure. If the permeability is too high, cells will have difficulty adhering to the pillars, and if it is too low, it will not facilitate the transportation of oxygen and nutrients. This also explains why the bone ingrowth effect of the trabecula scaffold is poor when the porosity is relatively small. The permeability of cancellous bone is approximately 1 × 10 − 9 m 2 to 10 × 10 − 9 m 2 [ 39 , 40 ]. From the permeability values in Fig. 11 (b), it can be seen that the porous structures are all within this range. This is also very close to the penetration rate range of TPMS scaffold [ 38 ]. The higher the porosity, the higher the permeability, and the higher quality transmission characteristics of the porous scaffold [ 41 ]. In the fluid flow line diagram of the porous structure shown in Fig. 12 , it can be observed that due to the fact that the number of internal pillars in the trabecula scaffold is much higher than that of the strut scaffold, and the internal pillars are randomly arranged, the fluid can flow through more areas when passing through the interior of the porous structure. Therefore, the internal fluid flow line diagram shows an irregular pattern. The internal pillars in the strut scaffold are arranged in a regular manner, and the pore sizes are uniform. Thus, the internal fluid flow line is uniform. The internal fluid flow can provide oxygen and nutrients for the cells. The more flow paths there are within the porous scaffold, the more attachment space there will be for the cells. Figure 13 (a) shows the bone ingrowth situation of the hole scaffold. The gradual increase of bone tissue on the scaffold over time indicates a good affinity between the 3D printed titanium alloy scaffold and the bone tissue. The 3D cross-sectional view in Fig. 13 (b) shows the ingrowth of bone tissue within the scaffolds at different time points. It can be visually observed that as time progresses and the porosity increases, the ingrowth of bone tissue improves. For the trabecular structure, it might be due to the smaller pores and the abundant space for bone cell growth and attachment inside that the bone tissue grows gradually from the outside to the inside. For the strut scaffolds, possibly because of the larger pores and less space for bone cell attachment inside, bone cells appeared in the internal structure of the scaffolds with porosities of 60% and 70% at 4 W, but these bone tissue cells mostly grew along the pillars, with less bone tissue inside. Figure 13 (c) shows the BV/TV values of the two types scaffolds at 4 W and 12 W under different porosity conditions. When the porosity is 50%, there is no significant difference in the BV/TV values of the two scaffolds at 4 W, and the difference is also small at 12 W. This might be because when the porosity is 50%, the pores of the trabecula scaffold are relatively small, this makes it very difficult for bone cells to grow in. Moreover, with smaller porosity, it is also challenging for blood to flow into the scaffold for the transport of oxygen and nutrients. This is consistent with the existing research results [ 42 ]. As the porosity increases, at porosity of 60% and 70%, the BV/TV values of the trabecula scaffold are higher than those of the strut scaffold, demonstrating the good bone ingrowth characteristics of the trabecula scaffold. At 4 W, the BV/TV values of the trabecula scaffolds with porosity of 60% and 70% are slightly higher than those of the strut scaffold. However, at 12 W, this value significantly exceeds that of the strut scaffolds. This might be because the trabecula scaffold has a larger WSS inside, providing more stimulation for the growth and adhesion of bone tissue cells into the scaffold interior [ 43 ]. At the same time, the fluid flow area inside the trabecula scaffold is larger, meaning that cells have more space for growth and adhesion. Therefore, over time, the trabecula scaffold has better bone ingrowth characteristics. By comparing Fig. 13 (c) and Fig. 11 (b), it can be seen that bone ingrowth and permeability are not linearly related. Therefore, when designing the scaffold structure, a balance should be struck between the transmission of force and the internal WSS stimulation. Figure 14 shows the VG staining images of hard tissue sections after implantation of the porous scaffold at different times. From the figure, it can be seen that there are more cross-junctions of pillars inside the trabecula scaffold, which provides more space for bone tissue to grow and adhere. Under different porosity conditions, the trabecula scaffold has better bone ingrowth performance than the strut scaffold. At 4 W, the cells were more adhered to the outer surface of the scaffold. By 12 W, bone cells also appeared inside the scaffold, and the cells grew inward along the inner wall of the scaffold. From the cross-sectional diagram of the center regions of the scaffold, it can be seen that although the bone tissue can grow along the pillar in the strut scaffold, the pores are too large for the bone cells to adhere. The internal bone tissue in this case is less than that of the trabecula scaffold. This might be the reason why the bone growth situation of the trabecula scaffold is better than that of the strut scaffold. Regarding the long-term stability issue after the implantation of the scaffold, once the scaffold is implanted in the bone defect area, it will induce the growth of bone tissue to enter and integrate with the host bone, forming a biological fixation, thereby achieving long-term stability [ 44 ]. This is also the reason why researchers, when studying porous titanium alloy scaffolds, not only consider their mechanical properties but also their biological properties [ 8 , 45 ]. Moreover, when implanting the porous scaffold, a fixation device is usually required for fixation. Therefore, when choosing the type of scaffold, it is necessary to comprehensively consider the combined mechanical effects of the porous scaffold and the fixation device. The stress conditions of porous scaffolds under physiological conditions are complex. This study only analyzed the situation of uniaxial compression. Therefore, in terms of the matching of the mechanical properties of porous scaffolds with the host bone under physiological conditions, multi-axis loading conditions need to be considered [ 37 , 46 ]. The finite element method should be used to conduct further analysis on the selected porous scaffold and fixation method, so that the scaffold can have both good mechanical support and good biological performance [ 4 , 47 ]. Conclusion This study employed a combined approach of mechanical experiments and simulation analysis to investigate the compressive mechanical properties of two types of scaffolds under different porosity conditions. Animal experiments investigated the biological properties of two types of scaffolds under different porosity. Under the same compression displacement, the internal stress distribution of the trabecula scaffold was uneven, the maximum stress within trabecula scaffold is much higher than that of the strut scaffold. The yield strength was also lower than that of the strut scaffold, indicating that the strut scaffold has better performance in terms of load-bearing The in vivo experiments demonstrated that the trabecula scaffold had better bone ingrowth performance under different porosity conditions than the strut scaffold. The results of CFD analysis also confirmed that the trabecula scaffold had more fluid areas and larger WSS to stimulate the proliferation of bone cells. Therefore, the trabecula scaffold is more suitable for the cancellous bone area with smaller loads and higher requirements for bone integration performance, while the strut scaffold is more suitable for the cortical bone area with higher requirements for mechanical performance When designing a scaffold for large segment bone defect repair, the scaffold can be divided into different areas, and different types of porous scaffolds can be adopted in different areas. The two complement each other, thereby maximizing the advantages of the 3D printed porous scaffold Author contributions L. L: Conceptualization, Methodology, Writing - original draft, Formal analysis, Writing - review & editing. S. W: Validation, Validation, Data curation, Conceptualization. X. W: Formal analysis, Supervision, Investigation. J. L：Investigation, Visualization, Resources, Supervision. All authors reviewed the manuscript. Funding This work was supported by Sichuan Science and Technology Program (2024YFHZ0067), China Postdoctoral Science Foundation (2023MD744134), Chongqing Natural Science Foundation (CSTB2025NSCQ-GPX1296), Natural Science Foundation of China (52205553), Science and Technology Research Program of Chongqing Municipal Education Commission (KJQN202500641 and KJQN202300628), Special Funding for Postdoctoral Research Projects in Chongqing (2023CQBSHTB3018). Data availability The data can be obtained from the corresponding author upon reasonable request. Declarations Ethics approval and consent to participate The study received approval from the Ethics Committee of the Affiliated Hospital of Southwest Medical University by the Declaration of Helsinki. Consent for publication Not applicable. Competing interests The authors declare no competing interests. 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