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Objective To investigate the influence of different cell structures on the static and dynamic mechanical performance of porous titanium alloy scaffolds,and to provide a theoretical mechanical basis for the application of scaffolds in the repair of mandibular bone defects.Methods Porous titanium alloy scaffolds with diamond,cubic,and cross-sectional cubic cell structures were manufactured using three-dimensional printing technology.Uniaxial compression tests and ratcheting fatigue with compression load tests were conducted to analyze the static and dynamic mechanical performances of scaffolds with different cell structures.Results The elastic moduli of the diamond cell,cross-sectional cubic cell,and cubic cell scaffolds were 1.17,0.566,and 0.322 GPa,respectively,and the yield strengths were 71.8,65.1,and 31.8 MPa,respectively.After reaching the stable stage,the ratcheting strains of the cross-sectional cubic,diamond,and cubic cell scaffolds were 3.3%,4.0%,and 4.5%,respectively.The ratcheting strain increased with increasing average stress,stress amplitude,and peak holding time,and decreased with increasing loading rate.Conclusions The evaluation results of the static mechanical performance showed that the diamond cell scaffold was the best,followed by the cross-sectional cubic cell scaffold and the cubic cell scaffold.The evaluation results of the dynamic mechanical performance showed that the cross-sectional cubic cell scaffold performed the best,followed by the diamond cell scaffold,whereas the cubic cell scaffold performed the worst.The fatigue performance of the scaffold is affected by the loading conditions.These results provide new insights for scaffold construction for the repair of mandibular bone defects and provide an experimental basis for further clinical applications of this scaffold technology.
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Objective To study the mechanical properties of titanium mesh and three-dimensional(3D)-printed metal vertebral body substitutes(VBS)to provide guidance for the selection and structural optimization of artificial vertebral implants in clinical practice.Methods The equivalent elastic modulus,equivalent yield strength,and structural failure mode of titanium mesh and 3D-printed porous,truss,and topologically optimized VBS were systematically investigated using compression tests.Results The elastic modulus of the titanium mesh(2 908.73±287.39 MPa)was only lower than that of the topologically optimized VBS.However,their structural strengths and stabilities were inadequate.The yield strength of the titanium mesh(46.61±4.85 MPa)was only higher than that of the porous VBS and it was the first to yield during compression.The porous VBS was insufficient for use as the vertebral implant owing to its poor mechanical strength(18.14±0.17 MPa-25.79±0.40 MPa).The truss VBS had good elastic modulus(2 477.86±55.19 MPa-2 620.08±194.36 MPa)and strength(77.61±0.50 MPa-88.42±1.07 MPa).However,the structural stability of the truss VBS was insufficient,and instability occurred easily during compression.The topologically optimized VBS had the highest elastic modulus(3 746.28±183.80 MPa)and yield strength(177.43±3.82 MPa)among all the tested VBS types,which could provide improved security and stability for artificial vertebral implant in vivo services.Conclusions Topology optimization results in a high strength and high stability VBS design.Moreover,it provides a large design space and great safety margin to provide increased possibilities for lightweight and new material design of future artificial vertebral implants.
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Objective For patients with foot drop gait, to design a kind of anterior ankle foot orthosis (AFO) with adjustable stiffness, so as to restore natural gait of the ankle by limiting the patients’ unusual plantar flexion to the optimum extent. Methods The minimum orthodontic moment of 10 foot drop male patients was measured by self-made experimental equipment, which could be used to select optimum material modulus of the AFO. The relationship between elastic modulus and different filling structures and filling ratio parameters was studied by tensile test. A typical patient with foot drop was selected, and the anterior AFO fitting the shape of patient’s foot was quickly made by three-dimensional (3D) printing with foot geometric data and specific filling material, filling structure and filling rate. The kinematics and surface electromyography (sEMG) of plantar flexors were tested under barefoot and wearing two kinds of AFOs, so as to verify the effect of the AFO on plantar flexion. The effectiveness of the limitation and the degree of preservation of ankle valgus and plantar flexion were discussed. Results The minimum corrective torque required for 10 male patients with foot drop was 2.16 N·m. Compared with the rigid AFO, the range of motion (ROM) of plantar flexion and valgus increased by 67.8% and 88.6% respectively with the flexible AFO. The activation of the muscles responsible for plantar flexion (soleus, medial head of gastrocnemius and lateral head of gastrocnemius) also decreased by 38.3%, 46.6% and 55.8%. Conclusions This AFO with adjustable stiffness can be used for orthosis customization of patients with foot drop, providing more effective and long-term orthosis function and potential.
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The adjacent anatomy of the pelvis is complicated, with digestive, urinary, reproductive and other organs as well as important blood vessels and nerves. Therefore, accurate resection of pelvic tumors and precise reconstruction of defects after resection are extremely difficult. The development of medical 3D printing technology provides new ideas for precise resection and personalized reconstruction of pelvic tumors. The “triune” application of 3D printing personalized lesion model, osteotomy guide plate and reconstruction prosthesis in pelvic tumor limb salvage reconstruction treatment has achieved good clinical results. However, the current lack of normative guidance standards such as preparation and application of 3D printing personalized lesion model, osteotomy guide plate and reconstruction prosthesis restricts its promotion and application. The formulation of this consensus provides normative guidance for 3D printing personalized pelvic tumor limb salvage reconstruction treatment.
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Objective To investigate biomechanical properties of personalized titanium root-analogue implants with porous surface, so as to provide theoretical basis for the design and clinical implantation of such implants. Methods Based on CT data, the personalized model of root-analogue implant with porous surface was designed by using 3-matic software, and after registering it with the mandible model, the mesh was divided and material parameters were attributed. The implant was applied with 200 N loading, and the maximum stress of the implant and the stress and strain of the bone around the implant were analyzed. An appropriate clinical case was selected and the implant was implanted immediately after tooth extraction for conducting clinical evaluation. Results The peak stress of the personalized root-analogue implant with porous surface was mainly concentrated on the interface between the solid structure and the porous structure of the implant. The maximum stresses of the solid structure and porous structure were 137.710 and 37.008 MPa, respectively, which were smaller than its yield strength. The three-dimensional (3D) printed porous root-analogue implants had good initial stability immediately after implantation, with minimal trauma and similar mechanical transmission to natural teeth. This simplified the surgical process, shortened the treatment time, and had high patient satisfaction. Conclusions The 3D printed root-analogue implant with porous surface explores a new method for immediate implantation after tooth extraction.
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Objective To optimize the design of three-dimensional (3D) printed scoliosis orthosis with computer-aided design (CAD), so as to achieve the advantages of good mechanical strength and lightweight model. Methods The body contour of a volunteer was scanned by a hand-held 3D scanner, then the body surface model of the volunteer was established. According to the three-point bending principles, traction and load-free principle, the body surface model was modified, and the pressure area and release area were designed. The model of scoliosis orthosis was then designed preliminarily. Comparative study on local optimization of hollow combinations with 32 different sizes were conducted using orthogonal experimental method. According to the optimization results, the model of scoliosis orthosis was hollowed out and biomechanically analyzed. The stress distributions of the 3D printed hollow scoliosis orthosis were compared, and its optimization effect was verified. Results By adopting the optimal design of local hollowing-out with 9 mm-radius and 23 mm-spacing circular hole (40% local weight loss), the 3D printed scoliosis orthosis with lighter weight, better air permeability and sufficient strength could be obtained. Conclusions Based on finite element biomechanical analysis, by adopting local hollow optimization design of circular hole at non-stress area, the 3D printed scoliosis orthosis can achieve the advantages of less printing materials and increased air permeability, and ultimately improve the wearing comfort and compliance of patients.
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Drug delivery with customized combinations of drugs, controllable drug dosage, and on-demand release kinetics is critical for personalized medicine. In this study, inspired by successive opening of layered structures and compartmentalized structures in plants, we designed a multiple compartmentalized capsular structure for controlled drug delivery. The structure was designed as a series of compartments, defined by the gradient thickness of their external walls and internal divisions. Based on the careful choice and optimization of bioinks composed of gelatin, starch, and alginate, the capsular structures were successfully manufactured by fused deposition modeling three-dimensional (3D) printing. The capsules showed fusion and firm contact between printed layers, forming complete structures without significant defects on the external walls and internal joints. Internal cavities with different volumes were achieved for different drug loading as designed. In vitro swelling demonstrated a successive dissolving and opening of external walls of different capsule compartments, allowing successive drug pulses from the capsules, resulting in the sustained release for about 410 min. The drug release was significantly prolonged compared to a single burst release from a traditional capsular design. The bioinspired design and manufacture of multiple compartmentalized capsules enable customized drug release in a controllable fashion with combinations of different drugs, drug doses, and release kinetics, and have potential for use in personalized medicine.
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The primary objective of this article is to explore effects of latest development in the area of three dimensional(3D) printing & to assess its abilities,and further undertake helpful reporting.Here the focus is to assess ad-vantages of 3D printing in orthopedics and analyze how 3D printed models help solve complex 3D orthopedics distortions.This study identified that 3D models manufactured by 3D printing models reduce medical parts de-velopment cost and surgical planning time.Integrating 3D printing with orthopaedics helps in understanding the conditions of problems and achieving the operation successfully.This technology can enable doctors/surgeons to design,produce,recreate and plan operations more accurately,carefully,and economically.3D models can assist specialists with a visual comprehension of the patient-particular pathology and life structures.Innovation in 3D printing initiated a scaffold for the virtual outline and execution of medical procedures.This research proposes the utilisation of 3D printers as an elective procedure for the fabrication of parts.It empowers surgeons/patients for better training,education and research.In the future,there is a foreseeable expansion of additive manufacturing in orthopedics.
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Objective:To evaluate the clinical efficacy of the preoperative digital design combined with three-dimensional(3D) printing models to assist percutaneous kyphoplasty (PKP) treatment for thoracolumbar compression frac-tures.Methods:From January 2018 to August 2020,we obtained data of 99 patients diagnosed thoracolumbar com-pression fractures.These patients were divided into control group (n =50) underwent traditional PKP surgery,and observation group (n =49) underwent preoperative digital design combined with 3D printing model assisted PKP treatment.The clinical efficacy was evaluated with five parameters,including operation time,number of intraoperative radiographs,visual analogue scale (VAS) score,Cobb Angle change,and high compression rate of injured vertebrae.Results:There were statistically significant differences of operation time and number of intraoperative radio-graphs between the two groups (P ＜ 0.05).For VAS score,Cobb Angle change and vertebral height compression rate,all of these three parameters were significantly improved when the patients accepted surgery treatment in two groups (P ＜ 0.05).However,there were no significant differences between control group and observation group for these three parameters either before or after surgery (P ＞ 0.05).Conclusions:Through the design of preoperative surgical guide plate and the application of 3D printing model to guide the operation,the precise design of preoperative surgical puncture site and puncture Angle of the injured vertebra was realized,the number of intraoperative radiographs was reduced,the operation time was shortened and the operation efficiency was improved.
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Objective A three-dimensional （3D） printing precise pressure device was designed specifically targeted at cambered limbs according to the requirement of postoperative rehabilitation of total knee replacement(TKR), and its effectiveness and safety was verified by finite element analysis. Methods Based on gastrocnemius muscle of lower limbs as the pressurized objects, the precise pressure device was designed, which contained an air pressure generating module, an inflatable airbag and a 3D printing brace. Through the closed loop control algorithm, the device stably supplied different pressures in the airbag. Distributed pressure data of the airbag-skin within contact surface were collected under different experimental conditions and imported into biomechanical simulation software which combined CT images to reconstruct 3D model of the lower limb mechanics. Finally, the effective compression area fraction and the joint micro-motion angle under each condition were obtained, to verify the effectiveness and safety of the system. Results Using generally preferred 4 cm-size offset and 4-barrel airbag configurations, under different intracapsular pressure of 5.32，6.65，7.98，9.31，10.64 kPa, the simulated knee joint micro-motion angles were 5.3°, 6.1°, 7.2°, 9.5°, 10.6°， respectively, and the effective compression area fraction could be up to 90-8%-95-2%. Conclusions For the optimized scheme, the dynamic range of joint micro-motion angle and the effective compression area fraction caused by different airbag pressure values were the best and met the design requirements of effectiveness and safety. The research findings can contribute to analyzing the influence of compression system on limb biomechanics, which are of great significance for effective and safe rehabilitation training after TKR.
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Objective To establish a comprehensive method combining physical model experiment and numerical simulation for studying airflow state of upper respiratory tract. Methods Based on CT medical images published online, a three-dimensional (3D) model of human upper respiratory tract was reconstructed. Based on 3D printing technology, an experimental model of the upper respiratory tract was established and the flow process of respiration was measured. A numerical simulation model was created based on the meshing of upper respiratory tract model and the turbulent Realizable k-ε model. Results Firstly, the result of numerical simulation was compared with the experimental conditions, and good agreement was achieved. The numerical simulation results showed that the airflow in respiratory process was in a parabolic shape; the distribution of flow field, pressure on wall and vortex structure were different between inspiratory and expiratory phases; there were air residues in the upper and lower nasal passages during the respiratory exchange process. In addition, the effects of airflow on physiological environment of the upper respiratory tract were preliminarily analyzed through the steak line, pressure field and vortex structure distribution. Conclusions The method proposed in this paper has the characteristics of pertinence, rapidity and accuracy, which gives full play to the advantages of reliable physical experiments and fine numerical simulation, and is applicable for studying different problems of the upper respiratory tract in different cases, with a high value for personalized diagnosis and treatment in clinic.
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The high elastic modulus of scaffolds or implants will result in stress shielding effect, which may lead to bone resorption and scaffold or implant loosening in the late stage. Porous scaffolds and implants can adjust their porosity and elastic modulus according to the mechanical environment, thereby reducing stress shielding; meanwhile, porous structures are beneficial to bone tissue growth, which is conducive to osseointegration. Three kinds of basic structure for porous scaffolds and implants by 3D printing were summarized, namely, uniform porous structure, bone-like trabecular structure and functionally graded structure. The design methods of these structures were introduced respectively, including computer-aided design (CAD)-based, implicit surface-based, image-based and topology optimization-based design method, so as to provide references for solving the stress shielding problem, as well as designing porous scaffolds and implants.
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The high elastic modulus of scaffolds or implants will result in stress shielding effect, which may lead to bone resorption and scaffold or implant loosening in the late stage. Porous scaffolds and implants can adjust their porosity and elastic modulus according to the mechanical environment, thereby reducing stress shielding; meanwhile, porous structures are beneficial to bone tissue growth, which is conducive to osseointegration. Three kinds of basic structure for porous scaffolds and implants by 3D printing were summarized, namely, uniform porous structure, bone-like trabecular structure and functionally graded structure. The design methods of these structures were introduced respectively, including computer-aided design (CAD)-based, implicit surface-based, image-based and topology optimization-based design method, so as to provide references for solving the stress shielding problem, as well as designing porous scaffolds and implants.
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Objective To obtain the distribution of stress concentration on the microporous structure of 3D-printed materials through a mapping algorithm with low calculation cost, so as to provide a new method of finite element calculation of 3D-printed materials for the prediction of fatigue life and the optimization of structural design. Methods Node coordinates and stress values within the influential region of the single pore were extracted to calculate the stress concentration coefficients of different nodes. The nearest node to each node on the ideal model was determined by distance, and the corresponding coefficient was multiplied by its stress value. When the nearest nodes of several nodes were the same, the average of these coefficients was assigned. For the pores close to the edge, an edge coefficient must be multiplied to reduce the error. Results An error of less than 8% between the mapping result and the calculation result was achieved for the case in which the pores were not near the edge, but for the case in which the pores were close to each other near the edge, the error was less than 15%. Conclusions The mapping algorithm can effectively characterize the stress concentration of the microporous structure of 3D-printed materials, and determine the stress distribution with low cost. This novel algorithm provides the finite element result for the optimization design and fatigue analysis of implants in clinical applications.
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Numerous applications for three-dimensional (3D) printing are extended rapidly and expected to revolutionize manufacturing industry, as well as the various aspects of medical field. This paper summarizes the domestic and overseas literatures on 3D printing used in medical field, and shows several advantages of 3D printing technique in the application of medicine. The 3D bio-printing technique, however, still need time to be evolved. In addition, the orderly and efficient development of 3D printing within the medical field will ultimately depend on the formulation of relevant policies and regulations and ongoing evolution of technique itself, and it still need carry out more in-depth research and exploration for functional human tissue and organ with 3D printing.
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Individualized treatment is an important direction in the development of orthopaedics. Either the application of the custom-made implants or using patient-specific surgical instrument to assist the implantation of conventional prosthesis, theoretically, could improve the matching between the implants and adjacent bony structures, so as to improve the overall function of the patients. However, the superiority of individualized treatment in theory cannot compensate its complexity and time-lag caused by individualized therapy in preoperative planning, design, manufacturing, etc. Therefore, individualized treatment is just a concept in most of the time. With the development of image technology and the maturity of 3D printing technique, the efficiency of individualized design and manufacturing is expected to be improving significantly, which shows the potential to translate this elegant concept into a practical principle.