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Background Achieving medial support for proximal humeral fractures (PHFs) by regular calcar screw positioning is challenging when the humeral head is small or locking plates are placed distally, as there are unable inserted calcar screws into the humeral head. We aimed to investigate the suitability of the two strategies, slotting calcar screw (SCS) and off-axis calcar screw (OCS) to achieve medial support for PHFs. Methods Regular calcar screw (RCS), SCS, OCS, and non-calcar screw (NCS) were tested via mechanical experiments and finite element analysis (FEA), using synthetic bones for biomechanical comparisons. All PHFs treated in our hospital from March 2017 to March 2019 were reviewed. The patients were divided into three groups based on the calcar screw fixation: RCS, SCS, and OCS. The postoperative varus collapse (neck-shaft angle changed to less than 120°) and Disabilities of the Arm, Shoulder and Hand (DASH) scores were recorded. Results The properties of RCS, SCS, and OCS against the torsion and varus force were superior to those of NCS, while the stiffness of SCS, OCS, and RCS were similar. FEA predicted lower peri-screw strains in the OCS and SCS than in the RCS, indicating a lower risk of cut-out. Patients (n = 125; 75 female, 50 male) aged 55.9 ± 13.0 years were evaluated. Compared with the RCS (5/55), varus collapse incidences were not significantly higher following SCS (0/29, p = 0.094) or OCS (3/41, p = 0.756), and neither were DASH scores (p = 0.867 and 0.736, respectively). Conclusions This study is a preliminary study demonstrating that the SCS and OCS fixation strategies could be useful alternatives when regular calcar fixation is not possible using the plate at hand.

Femoral neck fractures (FNFs) in young patients usually result from high-energy violence, and the vertical transcervical type is typically challenging for its instability. FNFs are commonly treated with three cannulated screws (CS), but the role of screws type on fixation effects (FE) is unclear. The purpose of this study was to evaluate the FE of ten types of CS with different diameters, lengths, depths, and pitches of thread via finite element analysis which was validated by a biomechanical test. Ten vertical FNF models were grouped, fixed by ten types of CS, respectively, all in a parallel, inverted triangular configuration. Their FE were scored comprehensively from six aspects via an entropy evaluation method, as higher scores showed better results. For partial-thread screws, thread length and thread shape factor (TSF) are determinative factors on stability of FNF only if thread depth is not too thick, and they have less cut-out risk, better compression effects and better detached resistance of fracture than full-thread screws, whereas full-thread screws appear to have better shear and shortening resistance. A combination of two superior partial-thread screws and one inferior full-thread screw for vertical FNF may get optimal biomechanical outcomes. The type of cannulated screw is important to consider when treating vertical FNF.

Jinhui Zhao,1,2,&ast; Qianying Cai,2,&ast; Dajun Jiang,1,2 Lingtian Wang,1,2 Haiyan He,2 Shengbao Chen,2 Weitao Jia,1,2 Changqing Zhang1,2 1Department of Orthopedic Surgery, Shanghai Jiaotong University Affiliated Sixth People’s Hospital, Shanghai, 200233, People’s Republic of China; 2Shanghai Institute of Microsurgery on Extremities, and Department of Orthopedic Surgery, Shanghai Jiao Tong University Affiliated Sixth People’s Hospital, Shanghai, 200233, People’s Republic of China&ast;These authors contributed equally to this workCorrespondence: Weitao Jia; Changqing Zhang, Department of Orthopedic Surgery, Shanghai Jiaotong University Affiliated Sixth People’s Hospital, Shanghai, 200233, People’s Republic of China, Tel +86-18930173388 ; +86-21-64701361, Email jiaweitao@shsmu.edu.cn; zhangcq@sjtu.edu.cnPurpose: Coronavirus disease 2019 (COVID-19) has brought an unprecedented change in wellbeing globally. The spread of the pandemic reportedly reduced the incidence of activity-related trauma, while that of fragility fractures remained stable. Here, we aimed to identify the risk factors associated with the prognosis of SARS-CoV-2 negative elderly patients with hip fractures.Patients and Methods: This retrospective study included elderly patients with hip fractures between 1st January and 9th May during the COVID-19 pandemic (Experiment group) and the same period from 2017 to 2019 (Control group). Perioperative mortality, complications, and functional recovery were compared between two groups of different time frame in the total cohort and patients who received surgical treatment. Multiple linear regression was carried out to identify the risk factors influencing the prognosis of COVID-negative elderly patients with hip fractures.Results: The proportion of patients with admission time less than 24 hours and the 6-month postoperative Parker score were significantly decreased during COVID-19 compared with the pre-COVID-19 period (p < 0.001). Multiple linear regression demonstrated that TTA (defined as time from injury to admission), rehabilitation after discharge and outpatient follow-up were associated with the 6-month Parker score in the total population (p < 0.001) and in patients who received surgical treatment (p < 0.001).Conclusion: Elderly patients with hip fractures had a poorer prognosis in epidemic period despite being COVID-19 negative. Factors including timely admission, postoperative follow-up, and rehabilitation could optimize safety and significantly improve the prognosis of elderly COVID-19 negative patients with hip fractures, even during a pandemic.Keywords: COVID-19, COVID-negative, elderly hip fracture, Parker score

Background The treatment of vertical femoral neck fractures (vFNFs) in young patients remains challenging, with a high complication rate by using traditional techniques. The use of cannulated screws (CSs) combined with a buttress plate represents an alternative approach for treating vFNFs. However, the biomechanical influence of the use or non-use of the proximal screws of buttress plates on vFNFs stability remains unclear. This study aims to analyse the biomechanics of buttress plate fixation with or without the use of proximal screws through finite element analysis (FEA) to further understand this approach. Methods We built five vFNFs (Pauwels angle 70°) finite element models treated using three cannulated screws (CS group) or three cannulated screws plus a locking buttress plate (buttress group). In the buttress group, use or non-use of proximal screws was carried out on two types of plates (4-hole & 6-hole). The following seven parameters were analysed to compare biomechanical properties of the five models: the stiffness; the maximal stress of the plate system (plate and screws), CSs and bone (MPS, MCS, MBS); the maximal displacement of internal fixations (plate system & CSs) and bone (MIFD, MBD); and the maximal relative displacement of interfragments (MID). Results Compared with CS model, the buttress models exhibited improved biomechanical properties, with increased stiffness and decreased MCS, MBS, MIFD, MBD and MID. The models fixed using buttress plates combined with a proximal screw showed greater stiffness (+ 3.75% & + 8.31% vs + 0.98% & + 4.57%) and MPS (795.6 & 947.2 MPa vs 294.9 & 556.2 MPa) values, and smaller MCS, MBS, MIFD, MBD and MID (− 3.41% to − 15.35% vs − 0.07% to − 4.32%) values than those using the same length plates without a proximal screw. Conclusions Based on the FEA results, buttress plates can improve construct mechanics, help to resist shear force and prevent varus collapse; under the modelling conditions, the use of a proximal screw on buttress plate may be a key technical feature in improving anti-shearing ability; additionally, this screw may be essential to reduce stress and prevent re-displacement of cannulated screws and fracture fragments.

Purpose Vitamin D (25[OH]D) status and bone turnover markers (BTMs) are considered important determinants of bone quality, which is associated with the risk of hip fractures, including both femoral neck and intertrochanteric fractures, in older adults; however, the exact relationship of 25(OH)D and BTMs with the type and severity of hip fractures remains unclear and the present study aimed to identify any specific associations. Patients and methods According to the inclusion and exclusion criteria, 441 older female patients with hip fractures from 2015 to 2020 and 215 women without hip fractures were included in this cross-sectional study. According to Garden and AO/OTA classifications for femoral neck and intertrochanteric fractures, patients were divided into less severe (Garden I and Garden II; 31A1) and more severe (Garden III and Garden IV; 31A2 and 31A3) fracture groups. Levels of the serum osteoblast indicator, N-terminal/mid region (N-MID); the osteoclast indicator, beta-carboxy terminal telopeptide (β-CTX); and 25(OH)D were analyzed. Results For patients with less severe fractures, mean 25(OH)D levels were significantly higher than those with more severe fractures (17.67 vs 15.30 ng/mL, p = 0.006). Higher 25(OH)D levels were also observed in patients with less severe intertrochanteric fractures (p = 0.01). After adjustments for confounders, 25(OH)D remained a risk factor for patients with more severe fractures (p = 0.01), particularly those with intertrochanteric fractures (p = 0.011). No significant differences in BTMS were found between patients with less severe and more severe fractures. Conclusion Levels of 25(OH)D were significantly associated with the severity of intertrochanteric, but not femoral neck, fractures. Neither 25(OH)D nor BTMs were associated with the type of hip fracture in older women. Separate consideration of intertrochanteric and femoral neck fractures may be appropriate when investigating the clinical association between 25(OH)D and the severity of hip fractures in older women.

Background: For nongeriatric patients with femoral neck fractures (FNFs), preoperative evaluation of fracture three-dimensional inclination is essential to identify fracture stability, select appropriate fixation strategies, and improved clinical prognoses. However, there is lack of evaluation system which takes into account both vertical and oblique inclinations. The purpose of this study was to comprehensively investigate the effect of vertical and oblique inclinations on fracture stability and reoperation risks.Methods: We retrospectively reviewed the medical records of 755 FNFs patients with over 2 years follow-up. The 3-D inclination angle in vertical (α) and oblique plane (β) were measured based on CT images. The optimal threshold for unstable 3-D inclination were identified by seeking the highest Youden Index in predicting reoperation and validated in the biomechanical test. According to the cut-off value proposed in the diagnostic analysis, forty-two bone models were divided into seven groups, and were all fixed with traditional three parallel screws. Interfragmentary motion (IFM) was used for comparison among seven groups. The association between reoperation outcome and 3-D inclination was analysed with a multivariate model.Results and Conclusion: The overall reoperation rate was 13.2%. Unstable 3-D inclination angles with an optimally determined Youden index (0.39) included vertical (α > 70°) and oblique (50°β > 20°/β < −20°) types. Biomechanical validation showed these fractures had significantly greater (p < 0.05) interfragmentary motion (1.374–2.387 mm vs. 0.330–0.681 mm). The reoperation rate in 3-D unstable group (32.7%) is significantly (p < 0.001) higher than that in 3-D stable group (7.9%). Multivariate analysis demonstrated that 3-D inclination angle was significantly (OR = 4.699, p < 0.001) associated with reoperation. FNFs with α > 70°; 50°<α < 70° and β > 20°/β < −20° are real unstable types with significantly worse interfragmentary stability and higher reoperation risks. Fracture inclination in vertical and oblique planes is closely related to reoperation outcomes and may be a useful complement to the way FNFs are currently evaluated.

Chondral defects caused by osteoarthritis (OA) are common but difficult to manage due to their limited capacity for self-repair. Further, the activated macrophages induced by OA stimulates chondrocytes degradation and inhibits regeneration, further impeding cartilage repair. Therefore, biomaterials with the potential for blocking vicious cycles between activated macrophages and chondrocytes would be promising for use in the treatment of chondral defects caused by OA. In this study, we fabricated porous Mg-Nd-Zn-Zr alloy (denoted JDBM) scaffolds coated with polydopamine (PDA) and investigated their cytocompatibility and impact on immunoregulation. Mesenchymal stem cells (MSCs) were co-cultured in supernatant from M1-polarized macrophages pretreated with extracts from JDBM scaffolds and the anti-inflammatory effect on the NF-κB pathway and reactive oxygen species (ROS) evaluated. JDBM scaffolds could reduce M1 macrophage numbers, while promoting those of M2 macrophages; recruit MSCs; and enhance chondrogenesis. Furthermore, lipopolysaccharide (LPS)-induced p65 translocation to the nucleus was inhibited by JDBM scaffolds, with ROS production and matrix metalloproteinase (MMP) expression also suppressed. These findings suggest that JDBM scaffolds can both promote chondrogenesis and effectively attenuate local inflammatory responses by transforming macrophages from the M1 to M2 subtype and down-regulating NF-κB signaling. Hence, JDBM scaffolds could promote chondrogenesis under inflammatory microenvironment and represent a promising material for treatment of chondral defects caused by OA.

BackgroundFor nongeriatric patients with femoral neck fractures (FNFs), internal fixation treatment is still the primary choice. Preoperative evaluation of fracture inclination and underlying stability is essential for selecting appropriate fixation strategies, thus improving clinical prognoses. The purpose of this study was to comprehensively investigate the 3-D inclination angle in both vertical and oblique planes from CT images, and its association with fracture stability and reoperation risks.MethodsWe retrospectively reviewed the medical records of 755 FNFs patients with over two years follow-up. The 3-D inclination angle in vertical (α) and oblique plane (β) were measured based on CT images. The optimal threshold for unstable 3-D inclination were identified by seeking the highest Youden Index in predicting reoperation and validated in the biomechanical test. According to the cut-off value proposed in the diagnostic analysis, forty-two bone models were divided into seven groups, and were all fixed with traditional three parallel screws. Interfragmentary motion (IFM) was used for comparison among seven groups. The association between reoperation outcome and 3-D inclination was analysed with a multivariate model.ResultsThe overall reoperation rate was 13.2%. Unstable 3-D inclination angles with an optimally determined Youden index (0.39) included α>70°; 50°20°/ β70°; 50°20°/ β

Background: The optimal internal fixation strategy for vertical femoral neck fractures (VFNFs) in nongeriatric patients remains uncertain. The purpose of this study was to compare the clinical prognoses and underlying mechanical characteristics of the novel off-axis screw technique with dynamic hip screw (DHS) and traditional three parallel screws. Methods: This study included a clinical investigation and a patient-specific finite element analysis (FEA). In the clinical investigation, VFNF patients were grouped by fixation type: (1) three parallel screws (G-TRI); (2) augmentation with an off-axis screw (G-ALP); and (3) DHS with an anti-rotational screw (G-DHS). Fixation failures (non-union, femoral neck shortening (FNS), varus deformation, screw cut-out) and avascular necrosis (AVN) of the three types were compared. In the FEA, twenty-four fixation models with the three fixation types were created based on the data of eight healthy volunteers. Models were assessed under walking conditions. Stiffness, interfragmentary motion (IFM), and implant stress were evaluated. Results: In the clinical investigation, fixation failure rate was significantly (pConclusions: Among fixation types for VFNFs, the off-axis screw technique exhibited a better interfragmentary stability (lowest IFM), and lower fixation failure rate (especially, FNS). Analyzing interfragmentary stability in biomechanical experiments is more consistent with clinical prognosis than construct stability for VFNFs, suggesting that internal fixations should aim for this outcome.

BACKGROUND AND PURPOSE Vertical femoral neck fractures (VFNFs) are one of the most difficult fractures to stabilize, with high non-union (17%), avascular necrosis (AVN, 21%), and femoral neck shortening (FNS, 29.0%) rates. The objective of this investigation was to directly compare the long-term clinical complication rates of VFNFs repaired by crossed (Alpha fixation) or parallel screws in non-geriatric patients. PATIENTS AND METHODS We conducted a retrospective comparative study of VFNFs in patients (

Implant‐associated infections (IAIs) are a common cause of orthopedic surgery failure due to microbial biofilm‐induced antibiotic‐resistance and innate immune inactivation. Thus, the destruction of microbial biofilm plays a key role in reducing IAIs. Herein, first, a magneto‐based synergetic therapy (MST) is proposed and demonstrated against IAIs based on biofilm destruction. Under an alternating magnetic field (AMF), CoFe2O4@MnFe2O4 nanoparticles (MNPs), with a rather strong magnetic hyperthermal capacity, can generate sufficient thermal effect to cause dense biofilm dispersal. Loosened biofilms provide channels through which nitrosothiol‐coated MNPs (MNP‐SNOs) can penetrate. Subsequently, thermosensitive nitrosothiols rapidly release nitric oxide (NO) inside biofilms, thus efficiently killing sessile bacteria under the magnetothermal effect of MNPs. More importantly, MNP‐SNOs can trigger macrophage‐related immunity to prevent the relapse of IAIs by exposing the infected foci to a consistent innate immunomodulatory effect. The notable anti‐infection effect of this nanoplatform is also confirmed in a rat IAI model. This work presents the promising potential of combining magnetothermal therapy with immunotherapy, for the effective and durable control and elimination of IAIs., This work originates a magneto‐based synergetic therapy (MST) strategy against implant‐associated infections (IAIs) based on nitrosated mercaptosuccinic acid (MSA)‐coated CoFe2O4@MnFe2O4 nanoparticles (MNP‐SNO) with excellent magnetic hyperthermal capacity, nitric oxide (NO) releasing efficiency, and innate immunomodulatory activity, which demonstrates the great potentials of magnetic nanomedicine for the durable control and elimination of IAIs.

Vertical femoral neck fractures in patients younger than 65 years of age often require hip‐conserving surgeries. However, traditional fixation strategies using three parallel cannulated screws often fail in such patients due to an unfavorable biomechanical environment. This study compared different cannulated screw fixation techniques in patients via patient‐specific finite element analysis with linear tetrahedral (C3D4) elements. Forty vertical femoral neck fracture models were created based on computed tomography images obtained from eight healthy participants. Five different fixation strategies: alpha, buttress, rhomboid, inverted triangle, and triangle were assessed in walking status. Biomechanical parameters including stiffness, interfragmentary motion in two directions (detachment and shearing), compression force, and maximal implant stress were evaluated. The mean relative coefficient of strain distribution between the finite element analysis and experiment was from 0.78 to 0.94. Stiffness was highest (p

Background Free vascularized fibula graft (FVFG) techniques have most consistently demonstrated beneficial effects in young patients diagnosed with nontraumatic osteonecrosis of the femoral head (NONFH), and the core track technique (CTT) in particular is the most commonly used technique. As an alternative to CTT, the modified light bulb technique (LBT) has been reported to have a higher success rate. However, its biomechanical outcomes are poorly understood. This study aimed to compare the biomechanical properties of modified LBT with those of CTT in treating NONFH. Methods Two types (C1 and C2) of NONFH finite element models were established on the basis of a healthy subject and the Japanese Investigation Committee (JIC) classification system, and the CTT and LBT procedures were simulated in each type of model. The average von Mises stresses and stiffness of the proximal femur were calculated by applying a load of 250% of the body weight on the femoral head to simulate walking conditions. In addition, two patient-specific models were built and simulated under the same boundary conditions to further validate the LBT. Results In the healthy subject-derived models, both the LBT and CTT resulted in reduced stresses in the weight-bearing area, central femoral head, femoral neck, and trochanteric and subtrochanteric regions and increased structural stiffness after surgery. In the weight-bearing area, the CTT reduced the stress more than the LBT did (36.19% vs 31.45%) for type C1 NONFH and less than the LBT did (23.63% vs 26.76%) for type C2 NONFH. In the patient-specific models, the stiffness and stresses also increased and decreased, respectively, from before to after surgery, which is consistent with the results of healthy subject-derived models. Conclusion The biomechanical effects of the LBT and CTT differ by the JIC type of NONFH. In terms of preventing the collapse of the femoral head, the LBT may be more effective for JIC type C2 NONFH and may be a suitable alternative to the CTT, while for JIC type C1 NONFH, the CTT is still a better choice. Both techniques can improve the biomechanical properties of NONFH by reducing the proximal femoral stress and increasing the structural stiffness.

Background: Free vascularized fibula graft (FVFG) technique has achieved the most consistent successful therapeutic effect on young patients diagnosed as nontraumatic osteonecrosis of femoral head (NONFH), of which the Core Track Technique (CTT) has been the most commonly used. As an alternative to CTT, the modified Light Bulb Technique (LBT) was reported to have a higher success rate. However, its biomechanical characters have been poorly understood. This study aimed to investigate the biomechanical properties of modified LBT in treating NONFH by comparing with CTT.Methods: Two types (C1 and C2) of NONFH finite element models were established from a healthy subject according to the Japanese Investigation Committee (JIC) classification, and CTT and LBT procedures were simulated in each type of the models. The average Von Mises stresses and stiffness of the proximal femur were calculated by applying 250% body weight loading on femoral head to simulate walking condition. In addition, two patient-specific models were built and simulated under the same boundary condition for the further validation of LBT.Results: In the healthy subject-derived models, both LBT and CTT resulted in reduced stresses in the weight-bearing area, central femoral head, femoral neck, and trochanteric and subtrochanteric regions, and increased structural stiffness after surgery. In the weight-bearing area, CTT reduced more stresses than LBT (36.19% vs 31.45%) for Type C1, while less reduction (23.63% vs 26.76%) for Type C2. In patient-specific models, stiffness and stresses of before and after surgery were also increased and reduced respectively, which is consistent with healthy subject-derived models.Conclusion: LBT and CTT have different biomechanical performance on different JIC type of NONFH. In terms of preventing the collapse of femoral head, LBT may be more effective for JIC Type C2, which could alternatively be chosen, while for JIC Type C1, CTT is still a better choice. Both techniques can improve biomechanical properties of NONFH with patients’ proximal femur stress reduced and structural stiffness enhanced.

Background Hip fractures in the elderly population has become a global issue due to its high morbidity and mortality. Although an increasing number of researchers are devoting attention to identify risk factors in attempts to reduce the incidence of hip fractures in the elderly, only few studies have investigated combined indicators in elderly hip fractures. The objective of the present study was to compare the accuracy of combined independent risk factors in assessing the risk of hip fractures in elderly women. Methods Ninety elderly females who sustained hip fractures and 110 female outpatients who fulfilled the inclusion criteria were included in our cross-sectional study. Bone mineral density (BMD), Beta-carboxy terminal telopeptide(β-CTX), N-terminal/mid region (N-MID), and 25(OH)D levels were analyzed. A novel evaluation model was established to evaluate combined indicators in assessing hip fractures in elderly women. Results Compared with the control group, taller height, higher levels of β-CTX, and lower levels of total hip BMD, femoral neck BMD, and 25(OH)D were found in the facture group. After adjustment for confounding factors, logistic regression analysis revealed that 25(OH)D, femoral neck BMD and height remained risk factors for hip fractures in elderly women. Then a model including independent risk factors was established. DeLong test showed the area under the ROC(AUC) of 25(OH)D was significantly greater than that for femoral neck BMD (p

Additional file 1. Supplementary materials.

In order to accurately understand the chrematistics of wind farm’ output, it is necessary to consider the correlation of the outputs of multiple wind farms. In this paper, a method for analyzing the correlation of multiple wind farms’ outputs based on fluctuation division and time shift technology is proposed. Firstly, the overall correlation characteristics of multiple wind farms are obtained by using sequential scatter diagram analysis and regression analysis. Then, the fluctuation process of wind farms is divided and paired by output fluctuation division and output fluctuation pairing algorithm. Finally, the time shift technique of Pearson correlation coefficient and granger causality test are used to obtain the optimal time shift quantity and direction. It can be verified by concrete examples that this method can accurately extract the local characteristics of wind farm output fluctuation, and then more accurately describe the relevant characteristics of wind farm output.

In recent years, photovoltaic (PV) power generation has developed rapidly at China and abroad. PV power generation is on the trend from auxiliary power supply to main power supply even leading power supply. Due to the fluctuation and intermittent characteristics of PV power generation, and zero inertia, the integration of large-scale grid-connected PV power generation may have a negative impact on the stability of the power system. Modeling grid-connected PV power generation systems is the key factor to investigate the influence between it and other parts of power system. Modeling of PV is also a hot issue that has been studied continuously for many years around the world. GE, WECC, CIGRE, CEPRI and so on have attached great importance to this issue and have published many research results. The existing research at China and abroad is reviewed in this paper, the existing problems are analyzed, and suggestions for future research are given.

Background: Tissue engineering (TE) is a promising solution for orthopaedic diseases such as bone or cartilage defects and bone metastasis. Cell culture in vitro and scaffold fabrication are two main parts of TE, but these two methods both have their own limitations. The static cell culture medium is unable to achieve multiple cell incubation or offer an optimal microenvironment for cells, while regularly arranged structures are unavailable in traditional cell-laden scaffolds, which results in low biocompatibility. To solve these problems, microfluidic techniques are combined with TE. By providing 3-D networks and interstitial fluid flows, microfluidic platforms manage to maintain phenotype and viability of osteocytic or chondrocytic cells, and the precise manipulation of liquid, gel and air flows in microfluidic devices leads to the highly organized construction of scaffolds. Methods: In this review, we focus on the recent advances of microfluidic techniques applied in the field of tissue engineering, especially in orthropaedics. An extensive literature search was done using PubMed. The introduction describes the properties of microfluidics and how it exploits the advantages to the full in the aspects of TE. Then we discuss the application of microfluidics on the cultivation of osteocytic cells and chondrocytes, and other extended researches carried out on this platform. The following section focuses on the fabrication of highly organized scaffolds and other biomaterials produced by microfluidic devices. Finally, the incubation and studying of bone metastasis models in microfluidic platforms are discussed. Conclusion: The combination of microfluidics and tissue engineering shows great potentials in the osteocytic cell culture and scaffold fabrication. Though there are several problems that still require further exploration, the future of microfluidics in TE is promising.

Background The position of Kirschner wires (K-wires) has an influence on the outcome of modified tension-band wiring (MTBW) in fixing patella fractures. However, the instruction for K-wires positioning is not clear enough. This study tried to clarify the effect of K-wires positioning and provide evidence for a more definite instruction. Methods The sagittal position (SP) suitable for placing K-wires was evenly divided into SP 1–5 from anterior to posterior, and the finite element models of midpatella transverse fractures fixed by the figure-of-eight or figure-of-zero MTBW were built up at each SP. Separating displacement of the fracture, stress of the fracture, and stress of the internal fixations were measured at 45° knee flexion by using finite element analysis. Results The separating displacement of the fracture was smaller at SP 3–5 (23% smaller than SP 1–2). From SP 1 to 5, the compression of the fracture surfaces increased (R = 0.99, P = 0.001); the improper stress area of the fracture surfaces decreased (R = − 0.96, P = 0.01), and so was the stress of K-wires (R = − 0.93, P = 0.02). However, the stress of stainless steel wires showed a stable trend. Conclusions The SP of K-wires plays a role in the function of MTBW in the surgical management of transverse patella fracture. At 45° knee flexion, posteriorly placed (close to the articular surface) K-wires enable optimal stability and stress for the fracture, which provides basis for the positioning of K-wires in clinical practice.

In recent years, wind power generation has been developed rapidly. Strong random and weak controllability of wind power makes wind power generation output uncontrollable. The energy storage device has a good active dynamic response performance, and its rapid output change capacity can support power system frequency stability. This paper proposes a wind power-storage system coordinated control method to improve frequency stability.

This paper studies energy storage system participating to frequency regulation of wind farms based on polyline fuzzy neural network (PFNN). Firstly, the concept of generalized inertia of wind-storage combined system is analyzed. Secondly, the frequency requirements of wind-storage combined system are analyzed, and the method of PFNN is introduced. By taking frequency change, frequency change rate and state of energy storage system as the inputs of PFNN, a frequency control method is proposed. Finally, simulations have verified the correctness of the proposed method.

Due to the renewable generation target and the continuously increasing electrical demand, a large number of wind farms and solar photovoltaic (PV)plants are being planned in China. As the electricity fault characteristics of inverter-interfaced renewable energy sources are different from the traditional synchronous generators. The fault circuit contributions are getting more and more attention from engineers. In this paper, the short-circuit calculation method considering dynamic reactive power support of renewable energy systems is proposed. Through a large number of calculations, the factors affecting short-circuit currents and trends of short-circuit current under different voltage drop depths are discussed. The results presented by this paper provide the reference for future research on control and protection of power systems with high penetration of renewable energies.

Due to wind power forecasting error, active power control may not satisfy the control objective. By analysis, the main reason is the asymmetry of power forecasting error. For this, an active power control strategy considering the asymmetry of wind power forecasting error is proposed. Using historical data, wind power forecasting error and its confidence interval are estimated. And confidence interval of wind power forecasting is introduced to establish the optimization model for dispatching active power among wind farms. Then the asymmetry power forecasting error can be compensated by the model. Based on this, operation risk is introduced to optimize the power distribution strategy. Then a simulation is designed using actual data of one wind power base in China. The results show that the proposed strategy is reasonable and effective to improve the performance of active power control of wind power and reduce the risk of power shortage.

A centralized frequency regulation strategy of PV plant based on equal adjustable capacity proportion mode is proposed in this paper. When the system frequency changes due to some disturbances, the requirement of adjust active power value is calculated according to the frequency changing, then original active power reference is added with this adjust value to obtain the final active power reference as to change the active power output of PV units to participate in system primary frequency regulation. On this basis, in order to allow all PV units in same PV plant to coordinate with each other, also to prevent some PV units from excessive regulation, a proportional regulation of power method (PROP) is implemented to allocate active power reference to each PV unit more reasonable, namely, each PV unit's output is according to equal adjustable capacity proportion. Finally, an actual PV plant model is established on DIgSILENT PowerFactory platform to verify the effectiveness of the proposed control strategy.

In this paper, a steady-state multi-terminal voltage source converter high voltage direct current (VSC MTDC) model for power system analysis in DIgSILENT PowerFactory is introduced. Power flow is one of the most important and most widely used calculation in power system analysis. Although DIgSILENT PowerFactory provides a variety of elements for building MTDC grids, it's very inefficient when using the basic elements, such as ElmVscmono and ElmDcdc, to build multi-voltage level MTDC grids for example collection of large-scale renewable energy generation cluster. The aim of this paper is to derive custom steady-state VSC HVDC models to be incorporated into built-in AC/DC power flow computations that can handle power grids with high proportion of renewable energy generation connected. The hybrid modeling methods can effectively improve the modeling efficiency and extensibility. An AC/DC power flow is implemented using DIgSILENT PowerFactory to show the validity of the steady-state models.

In order to make full use of the active function of the photovoltaic (PV) power unit itself, a decentralized frequency regulation strategy for PV plant is proposed based on droop control idea in this paper. The active power regulation value, as an additional active power reference, is obtained according to the frequency regulation coefficient of PV unit; then the active power output of the PV unit is quickly regulated to the reference value, so that the frequency recovery of power system is restored. Since each PV unit in the power plant can achieve frequency regulation directly through the change of terminal frequency value, the response time will be faster than other control modes. Finally, a PV power plant which adopts the decentralized frequency regulation system is modelled on the DIgSILENT PowerFactory platform, and the control effect of the decentralized frequency regulation is verified by simulation results under different disturbances.

In order to make full use of the ability of photo voltaic (PV) units to regulate their own reactive power to participate in voltage stability control of power system, this paper takes full account of the interaction between power grid and PV power plant and proposes a multi-level reactive power control strategy based on sensitivity analysis for PV plant. Firstly, reference of reactive power is calculated combined with the analysis of reactive power and voltage sensitivity of PV power plant and the operation status of power grid. Secondly, reactive power command is allocated to each PV unit according to the reactive power margin. Finally, a reactive power control system model based on an actual PV plant project is established to verify the correctness of proposed strategy in this paper.

As the commonly used fixation strategy of medial malleolar fractures, cancellous screws (CS) have been challenged for instability, bone destruction, and metal prominence. It is still unclear whether a locking compression plate (LCP) is a better choice in such fractures. Our purpose is to compare the mechanical efficacy of LCP with traditional 4.0-mm CS for transverse, oblique, and vertical medial malleolar fractures by using finite element analysis. In this study, 3-dimensional models of the distal tibia were reconstructed from a computed tomography scan of a young healthy male adult. Conditions included 3 fracture lines at 30°, 60°, and 90°; 2 groups of fixation (LCP and CS); and 3 adduction loads of 300, 500, and 700 N applied to the medial malleolar joint surface. The proximal part of the tibia was fixed for all degrees of freedom. The fracture displacements of the LCP were smaller than those of CS (p < .05). The stiffness of the LCP constructs was much higher than that of the CS constructs, especially in the 90° fractures (490.3 versus 163.6 N/mm). The mean stress around the CS was higher than that in LCP for 60° and 90° fractures, but there was no difference for 30°. Maximal bone stress increased (19.84 to 50.86 MPa) and concentrated on cortical bone in LCP, whereas it concentrated on cancellous bone in CS. The results showed that LCP could improve stability, preventing bone destruction in oblique and vertical medial malleolar fractures. However, in transverse fractures, CS provides sufficient stability, with no need to use LCP.

To review the research and application progress of bioactive glass in bone repair.The recently published literature concerning bioactive glass in bone repair was reviewed and summarized.Bioactive glass can classified different types, such as bioactive glass particulate, bioactive glass scaffold, bioactive glass coating, injectable bioactive glass cement, and bioactive glass delivery system. Bioactive glass has been well studied in the field of bone repair due to its excellent biological properties. Also, the remarkable progress has been made in various aspects.Bioactive glass is a reliable material of bone repair and will play an even more important role in the future.综述生物玻璃在骨修复中的研究进展。.查阅国内外相关研究文献，并对取得的主要成果进行总结。.生物玻璃包括生物玻璃颗粒、生物玻璃支架、生物玻璃涂层、可注射型生物玻璃骨水泥、生物玻璃载体，因其具有良好的生物学性能，成为骨修复材料的研究热点，并已取得显著进展。.生物玻璃是一种可靠的骨修复材料，在未来骨修复治疗中将占据更重要的地位。.

Qualitative and quantitative analysis are employed to estimate the possibility of sub-synchronous resonance (SSR) for a 500kV series compensated transmission system in this paper. Firstly, the torsional mode frequencies and mode shapers in sub-synchronous band are calculated by analysis method. Secondly, the impedances in different frequencies are computed after processing this system at the instance of frequency scanning principle, and then according to impedance-frequency curve, the risk of SSR for the system is evaluated qualitatively. Finally, the time-domain simulation is adopted to the system at different operating conditions on the basis of PSCAD/EMTDC. The results show that the shaft torsional vibration modal calculated by analysis method and time-domain simulation are consistent; the shaft torsional vibration intensity and modal vary a lot from operating conditions; under the condition that the electrical and mechanical parameters are the same, with the number of parallel generator increasing, the interaction of different units is more apparent and the shaft torsional vibration intensity is more serious; the torsional vibration will not take place at the shaft in generator segment under any conditions.

 Abstract—PSASP is a widely used power system analysis program in China, and it provides various measured models and corresponding parameters of synchronous generator's control system. DIGSILENT Power Factory is a popular power system analysis software package around the world. In this paper, some commonly used models in PSASP are established in DIGSILENT Power Factory. The contrast effect is implemented by conducting small perturbation and large disturbance in a two-area four-machine system at last.

The accuracy of wind plant power control strategy is the key to ensure the adaptability of the wind plant. Effective testing and verification are essential means for the correctness of the control strategy. In this paper, the principle of active and reactive power control system for wind plant is studied firstly, the implementation architecture of power control system of wind plant is analyzed then, the modules of the power control system of the wind plant is implemented according to the modular design thirdly. Finally, a wind plant model with practical engineering background is established to validate the feasibility of the proposed wind plant power control system by injecting the measured data.

Accurate wind turbine model is the basis of studying its dynamic physical process and performance characteristics. In order to resolve the difficulties in modeling direct-drive permanent magnet wind turbine (DD-PMWT) because of the absence of permanent magnet synchronous generator (PMSG) model in some existing power system analysis software, the method to interconversion between electrical excitation synchronous generator (EESG) and PMSG was presented as well as the parameter conversion formulas and procedure were provided on the basis of their mathematical model and equivalent circuit in this paper. In additon, the model of DD-PMWT was built in DIgSILENT PowerFactory by means of replacing PMSG with EESG. Finally, based on the typical test system provided by Western Electricity Coordinating Council (WECC), the dynamic characteristics of DD-PMWT were analyzed. The simulation results verified the validity of the proposed method and the rationality of the established DD-PMWT model.

The integration of large-capacity wind energies into a power system creates big challenges to the power system operation and control due to the intrinsic intermittence of wind energies, which constrains further developments of wind power generation. Countries around the world including Europe, USA and China have all made Grid Codes with clear requirements on active and reactive power controls in a wind farm. By effective active and reactive power controls, wind power curtailments can be substantially reduced. Furthermore, there have been no mature simulation and analysis platforms in China on testing correctness and rationality of wind farm control strategies so far. This chapter reports our research as well as engineering practices on building an integrated active and reactive power control system for wind farms using PowerFactory and MATLAB. The highlights that make this work unique are as follows: (i) the integration of PowerFactory and MATLAB makes the active and reactive power control modelling efficient and flexible; (ii) both the real measurements of wind speeds and the active power forecasted from history data are inputted in text file format to each wind generator in PowerFactory; (iii) the reactive power control capabilities of wind generators are fully utilized to reduce the scale of the reactive power compensations installed in a wind farm or from the grid.