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.

Additive manufacturing(3D printing)technology aligns with the direction of precision and customization in future medicine,presenting a significant opportunity for innovative development in high-end medical devices.Currently,research and industrialization of 3D printed medical devices mainly focus on nondegradable implants and degradable implants.Primary areas including metallic orthopaedic implants,polyether-ether-ketone(PEEK)bone implants,and biodegradable implants have been developed for clinical and industrial application.Recent research achievements in these areas are reviewed,with a discussion on the additive manufacturing technologies and applications for customized implants.Challenges faced by different types of implants are analyzed from technological,application,and regulatory perspectives.Furthermore,prospects and suggestions for future development are outlined.

Objective:To evaluate the effect of cinacalcet on right ventricular function in rats with MCT-induced arterial pulmonary hypertension by echocardiography.Methods:Thirty male SD rats were randomly divided into control group, PAH group, and cinacalcet group, with 10 rats in each group. Rats in the cinacalcet group were given intraperitoneal injection of cinacalcet hydrochloride with 30 mg/kg, and the control group and the PAH group were given equal-volume of solvent. Echocardiographic parameters: right ventricular wall thickness (RVWT), right ventricular basal dimension (RVD), left ventricular eccentricity index (EI), tricuspid annular plane systolic excursion (TAPSE), right ventricular fractional area change (RVFAC), tricuspid lateral annular systolic velocity (s′), right ventricular global longitudinal strain (RV4CSL), and right ventricular free wall longitudinal strain (RVFWSL), etc. Histopathological parameters: pulmonary arteriole wall thickness (WT), right ventricular cardiomyocyte mean diameter (RV cell-D), collagen volume fraction (CVF) and right ventricular hypertrophy index (RVI). Echocardiographic and pathological parameters were compared among three groups, and the correlation between right ventricular pathological changes and strain parameters was analyzed.Results:①Compared with the control group, WT, RV cell-D, CVF and RVI in PAH group were increased (all P<0.01), the size of right ventricle and thickness of RV wall were increased (all P<0.05), and the right ventricular longitudinal strain was reduced ( P<0.01). ②Compared with the PAH group, rats in the cinacalcet group showed reduced WT, RV cell-D, CVF and RVI (all P<0.01), as well as improved structure and function of the right ventricle (all P<0.05). There was no statistical difference of the above parameters between cinacalcet and control group (all P>0.05). ③Correlation analysis: the right chamber remodeling parameters CVF and RV cell-D were positively correlated with WT ( rs=0.706 3, 0.629 4; both P<0.05); and RVFWSL correlated well with CVF, RV cell-D ( rs=-0.685 3, r=-0.767 2; both P<0.05). Conclusions:The right ventricular inverse remodeling of PAH rats with the intervention of cinacalcet was retained, suggesting that cinacalcet had a protective effect on the structure and function of the right ventricle in rats with PAH.

Objective Aiming at the problem of significant anisotropy in the three-dimensional ( 3D) printed polyether-ether-ketone ( PEEK) bone substitutes manufactured by material extrusion technology, taking the femur, the main load-bearing long bone of the lower limb, as an example, the biomechanical properties of the femoral model under different direction in the build chamber were evaluated by the combination of finite element analysis and in-vitro mechanical experiment. Methods A left femoral model was obtained by reconstruction from CT data. The stress and displacement of the 3D printed PEEK femur with different directions in the build chamber under five physiological postures in the human gait cycle were simulated by varying the orthogonal anisotropy mechanical properties. An in-vitro mechanical experiment was conducted to investigate the safety and stability of the femur through a 3D printed PEEK femur. Results When the long axis of the femur model was perpendicular to the building platform of the 3D printer, a better mechanical property was obtained, and the maximum von Mises stress was 46. 56 MPa, which was lower than the yield stress of PEEK, while the maximum displacement was larger than that of the natural femur under same loading condition. Therefore, the 3D printed PEEK femur met the strength requirement, but the stability needs to be improved. Conclusions The long axis is recommended to be perpendicular to the building platform when the material extrusion technology was used for the substitute of the load-bearing long bone, and the effect of its anisotropy on service performance of the substitute should be carefully considered when the 3D printing technology is used for load-bearing bone substitute.

Objective To propose a quick and low-cost personalized diabetic foot modeling and insole design scheme, so as to reduce the plantar pressure accurately. Methods The foot model of the patient was constructed by scaling the model with foot feature parameters, to make biomechanical analysis on plantar pressure. By means of numerical mapping model of insole elasticity and plantar pressure, the three-dimensional (3D) personalized insole model with gradient modulus was constructed. The insole was then manufactured via 3D printing technology and used for experimental validation. Results The related mechanical parameters from finite element prediction of the foot model constructed by the scaling modeling method were close to those of the CT reconstructed model, and the maximum error was controlled within 15%. Compared with wearing the normal insole, the peak pressure of the personalized insole was effectively reduced by 20%. The time and economic cost of this simplified design was reduced by approximately 90%. Conclusions The design scheme of the diabetes insole shortens the design cycle, and the personalized insole can effectively and accurately reduce the sole pressure, and reduce the risk of foot ulcer, which provides a technical basis for the promotion of the personalized diabetes insole.

Objective Aiming at the clinical problem of the low matching degree with the patient’s anatomical morphology for traditional cervical fusion cage, a cervical fusion cage with the function of adjustable height and the shape matched with the vertebral body was established, and its biomechanical properties were evaluated. Methods A cervical C4-5 segment fusion model was established according to anterior cervical discectomy and fusion (ACDF), so as to simulate different motion conditions, i.e. anterior flexion, posterior extension, left/right lateral flexion, left/right rotation, and stress of the fusion cage and vertebral endplate was calculated. After three-dimensional (3D) printing of the fusion cage, an in vitro mechanical experiment was conducted to explore safety and stability of the fusion cage. ResultsThe fusion cage could keep the range of motion (ROM) of cervical vertebrae at the fusion segment with 1°-2.8° and reduce the ROM to 40%-80% of the natural segment. In the in vitro compression test, the yield load of the fusion cage was (2 721.67±209) N, which met the maximum demand of the physiological load in service state. Conclusions The designed fusion device with adjustable height shows better biomechanical properties and can reduce the selection step in operation.

Objective To make finite element analysis and compressive performance test on three-dimensional (3D) printed personalized poly-ether-ether-ketone (PEEK) condyle prosthesis, so as to analyze stress distribution characteristics and mechanical properties of the prosthesis, and to evaluate its clinical value and prospect. Methods The finite element models of PEEK condyle prosthesis, mandible and fixation screw were established by software such as CBCT, Mimics, Geomagic Studio, SolidWorks and ANSYS Workbench. The maximum mastication force was applied, and the maximum stress of the condyle prosthesis and screw, as well as the stress and strain of the mandible were recorded. In order to simulate the actual clinical situation, a special fixture was designed to test compression performance of the condyle prosthesis prepared by the fused deposition modeling (FDM) and selective laser sintering (SLS) at the rate of 1 mm/min. Results The peak stress of the PEEK condyle prosthesis was 10.733 MPa, which was located at the back of the condyle neck. The peak stress of 5 fixing screws was 9.707 5 MPa, which appeared on the 2# and 5# screws near the trailing edge of the mandibular ascending branch. The peak stress of both the prosthesis and the screw was smaller than its yield strength. The maximum pressure of the condyle prosthesis prepared by FDM and SLS was (3 814.7±442.6) N and (1 193.970±260.350) N, respectively. Compared with the SLS preparation, the FDM prepared prosthesis not only had higher compression strength but also better toughness. Conclusions The 3D printed personalized PEEK condyle prosthesis shows uniform stress distributions and good mechanical properties, which can provide the theoretical basis for PEEK as reconstruction material for repairing temporomandibular joint.

Objective:To assess global myocardial work in non-ST-segment-elevation acute coronary syndrome (NSTE-ACS) patients with no obvious regional wall motion abnormalities and preserved left ventricular ejection fraction (LVEF) by noninvasive left ventricular (LV) pressure-strain loops, and to explore its diagnostic value in patients with NSTE-ACS.Methods:A total of 169 NSTE-ACS patients with normal wall motion abnormalities and LVEF (>55%) were recruited in Beijing Chao Yang Hospital, Capital Medical University from June to December 2019. The patients were divided into two groups according to the degree of coronary stenosis, including severe coronary artery stenosis group ( n=121), and no severe stenosis group ( n=48). The patients of severe coronary artery stenosis group were further subdivided into single-vessel severe stenosis group ( n=52) and multi-vessel severe stenosis group ( n=69). Global longitudinal strain (GLS) analysis was performed by speckle tracking echocardiography before coronary angiography. Brachial cuff systolic pressure was used as left ventricular pressure to construct a non-invasive left ventricular pressure-strain loop. Global myocardial work index (GWI), global constructive work (GCW), global waste work (GWW) and global myocardial work efficiency (GWE) was computed by LV pressure-strain loops with a proprietary algorithm between groups. ROC curve analysis was used to determine the optimal cutoff value of the parameters to detect severe coronary artery stenosis. Independent factors affecting left ventricular myocardial function were assessed by Logistic regression analysis. Results:GLS, GWI, GCW and GWE were significantly reduced, and GWW was increased in severe coronary artery stenosis group than in no severe stenosis group(all P<0.05). GLS was significantly reduced in multi-vessel severe stenosis group ( P<0.05) but not in single-vessel severe stenosis group ( P=0.32). GWE was an independent factor affecting myocardial function in severe coronary artery stenosis group, GWE<96% had a area under the curve (AUC)=0.83 (74% for sensitivity, 81% for specificity) to identify severe coronary artery stenosis, and was superior to GLS (AUC=0.66, P<0.05) and GWI (AUC=0.70, P<0.05). Conclusions:In NSTE-ACS patients with severe coronary artery stenosis, no obvious regional wall motion abnormalities and preserved LVEF, LV global myocardial function is impaired based on noninvasive pressure-strain loops, GWI, GCW, and GWE are reduced, and GWW is increased, and GWE is a more sensitive index than GLS and GWI to predict severe coronary artery stenosis in NSTE-ACS patients.

Objective To evaluate the cardiac hemodynamics and function before and after balloon pulmonary angioplasty ( BPA ) treatment in patients with chronic thromboembolic pulmonary hypertension ( CTEPH) using echocardiography ,and to discuss the clinical value of the treatment . Methods A total of 36 CT EPH patients with medium‐high risk stratification underwent BPA during the period of September 2016 to January 2019 in Beijing Chao‐Yang Hospital ,Capital M edical University were recruited . T he following conventional echocardiographic parameters including right ventricular basal diameter ( RVD ) ,left ventricular basal diameter ( LVD) ,right atrial diameter ( RAD) ,left atrial diameter ( LAD) ,main pulmonary artery diameter ( DM PA ) , left ventricular eccentricity index ( LVEI ) , left ventricular ejection fraction ( LVEF) and pulmonary artery systolic pressure ( PASP ) were recorded .Echocardiographic parameters of right ventricular ( RV ) function including tricuspid annular plane systolic excursion ( T APSE ) , right ventricular fractional area change ( RVFAC ) ,tissue Doppler – derived tricuspid lateral annular systolic velocity ( S′) ,RV index of myocardial performance ( RIM P ) and right ventricular free wall longitudinal strain ( GLS) were measured . T he patients were divided into 2 groups according to the threshold value of postoperative SPAP of 50 mmHg (group Ⅰ :SPAP ≤ 50 mmHg ,group Ⅱ :SPAP＞50 mmHg) . Changes between each parameter before and after BPA were analyzed . Results ① T he frequency of BPA treatment for CT EPH patients ranged from 1 to 6 times . After BPA treatment ,SPAP decreased significantly ,and the measurements of RV function including T APSE ,RVFAC ,RIM P and GLS improved significantly ( all P ＜0 .05) . ②Patients in group Ⅰ showed significantly better RV function including T APSE ,RVFAC and GLS compared with group Ⅱ before BPA ( P ＜0 .05) . ③Univariate logistic regression showed that parameters of preoperative RV function T APSE , RVFAC and GLS had certain effects on the curative effect of interventional surgery . Conclusions Echocardiography can evaluate the hemodynamics and RV function in CT EPH patients with BPA .After BPA ,pulmonary artery pressure decreases and RV function improves to some extent ,suggesting that the treatment of BPA has certain clinical application and popularization value .

Objective: To evaluate the cardiac hemodynamics and function before and after balloon pulmonary angioplasty (BPA) treatment in patients with chronic thromboembolic pulmonary hypertension (CTEPH) using echocardiography, and to discuss the clinical value of the treatment. Methods: A total of 36 CTEPH patients with medium-high risk stratification underwent BPA during the period of September 2016 to January 2019 in Beijing Chao-Yang Hospital, Capital Medical University were recruited. The following conventional echocardiographic parameters including right ventricular basal diameter (RVD), left ventricular basal diameter (LVD), right atrial diameter (RAD), left atrial diameter (LAD), main pulmonary artery diameter (DMPA), left ventricular eccentricity index (LVEI), left ventricular ejection fraction (LVEF) and pulmonary artery systolic pressure (PASP) were recorded.Echocardiographic parameters of right ventricular (RV) function including tricuspid annular plane systolic excursion (TAPSE), right ventricular fractional area change (RVFAC), tissue Doppler–derived tricuspid lateral annular systolic velocity (S′), RV index of myocardial performance (RIMP) and right ventricular free wall longitudinal strain (GLS) were measured. The patients were divided into 2 groups according to the threshold value of postoperative SPAP of 50 mmHg (group Ⅰ: SPAP ≤ 50 mmHg, group Ⅱ: SPAP>50 mmHg). Changes between each parameter before and after BPA were analyzed. Results: ①The frequency of BPA treatment for CTEPH patients ranged from 1 to 6 times. After BPA treatment, SPAP decreased significantly, and the measurements of RV function including TAPSE, RVFAC, RIMP and GLS improved significantly (all P<0.05). ②Patients in group Ⅰ showed significantly better RV function including TAPSE, RVFAC and GLS compared with group Ⅱ before BPA (P<0.05). ③Univariate logistic regression showed that parameters of preoperative RV function TAPSE, RVFAC and GLS had certain effects on the curative effect of interventional surgery. Conclusions Echocardiography can evaluate the hemodynamics and RV function in CTEPH patients with BPA.After BPA, pulmonary artery pressure decreases and RV function improves to some extent, suggesting that the treatment of BPA has certain clinical application and popularization value.