Single-plane osteotomy model is inaccurate for evaluating the optimal strategy in treating vertical femoral neck fractures: A finite element analysis.

BACKGROUND AND OBJECTIVES: The conventional method for simulating vertical femoral neck fractures (vFNFs) is via a vertical single-plane osteotomy (SPO) across the entire femur. However, the accuracy of SPO for evaluating the optimal internal fixation strategy (IFS) and the appropriate assessment parameters is not clear. This study thus aimed to examine the accuracy of SPO in evaluating IFSs and to identify appropriate evaluation parameters using finite element analysis. METHODS: Eighty patient-specific finite element models were developed based on CT images from eight vFNF patients. The natural fracture model was built using structural features of the affected side, while the SPO was simulated on the healthy side. Five different IFSs were applied to both the natural fracture and SPO groups. Thirteen parameters, including stress, displacement, and stiffness, were subjected to a two-way repeated measures ANOVA to determine the effect of IFSs and fracture morphology on stability. A Pearson correlation analysis was performed on varied parameters with various IFSs to identify independent parameters. Based on these independent parameters, the entropy evaluation method (EEM) score was used to rank the performance of IFSs for each patient. RESULTS: Eight of the thirteen parameters were significantly influenced by IFSs (p < 0.05), two by fracture morphology (p < 0.01), and none by the interaction between IFS and fracture morphology. In the natural fracture group, parameters including screw stress and displacement, bone cut rate (BCR), and compression effects varied independently with distinct IFSs. In the SPO group, trunk displacement, BCR, cut-out risk, and compression effects parameters changed independently. The BCR of the Alpha strategy was significantly higher than that of the Inverted strategy in the natural fracture group (p = 0.002), whereas the opposite was observed in the SPO group (p = 0.016). Regarding compression effects, two IFS pairings in the natural fracture group and seven IFS pairings in the SPO group exhibited significant differences. None of the five IFSs achieved the optimal EEM score for each patient. CONCLUSIONS: The single-plane osteotomy model may have limitations in assessing IFSs, particularly when the bone cut rate and compression effects are the main influencing factors. Parameters of the screw stress and displacement, BCR, and compression effects appear to be relevant in evaluating IFSs for natural fracture models. It indicates that individualized natural fracture models could provide more comprehensive insights for determining the optimal IFS in treating vFNFs.

Hybrid lithium tantalite-silicon integrated photonics platform for electro-optic modulation.

Integrated electro-optic modulators are key components in photonic integrated circuits. Silicon photonic technology is considered to be promising for large-scale and low-cost integration. However, silicon does not exhibit any Pockels effect, and the electro-optic modulator based on free-carrier dispersion suffers from challenges such as high-power consumption, limited bandwidth, and large optical propagation loss. Here, a new, to the best of our knowledge, hybrid lithium tantalite-silicon platform is proposed for electro-optic modulators based on the Pockels effect. Benefiting from the strong Pockels coefficients of a thin-film lithium tantalite, a hybrid microring-based modulator is demonstrated. The quality factor and the extinction ratio of the hybrid microring are 1.7 × 104 and 10 dB, respectively. The linear bidirectional wavelength tuning efficiency is measured as 12.8 pm/V. The measured 3-dB bandwidth is > 20 GHz. High-quality eye diagrams of 20 Gbps non-return-to-zero signal and 20 Gbps four-level pulse amplitude modulation signals are generated experimentally. The proposed platform extends the toolbox of silicon photonics technology, which paves the way for high-speed modulators and phase shifters in optical communication and optical phased array.

A biomechanical evaluation of firefighters' musculoskeletal loads when carrying self-contained breathing apparatus in walking and running.

INTRODUCTION: Musculoskeletal loading data are needed to design ergonomic intervention for firefighters. This study aimed to quantify the firefighters' musculoskeletal loads during self-contained breathing apparatus (SCBA) carriage and evaluate the effectiveness of shoulder strap length variation for the prevention of SCBA-related injuries. METHOD: Twelve firefighters (height: 174.6 ±â€¯2.4 cm, mass: 67 ±â€¯3.5 kg, BMI = 22 ±â€¯1 kg/m2) participated the walking and running protocols with no SCBA equipped and three varying-strapped SCBAs conditions. Joint range of motion and surface electromyography (sEMG) were synchronously measured. Subsequently, joint kinematics was inputted for subject-specific musculoskeletal modeling to estimate muscle forces and joint reaction forces, while the sEMG was used to validate the model. Repeated measures analysis of variance was used for the main effects (p < 0.05). Independent samples t-test was performed to determine differences between walking and running. RESULTS: Walking with SCBA increased the rectus femoris force and hip reaction force by 34.92% [F = 53.629; p < 0.001; η2 = 0.317] and 34.71% [F = 53.653; p < 0.001; η2 = 0.517], the growth rate was 54.2% [F = 76.487; p < 0.001; η2 = 0.418] and 51.19% [F = 69.201; p < 0.001; η2 = 0.652] during running, respectively. Running with SCBA significantly increased the knee reaction force by 63.04% [F = 83.960; p < 0.001; η2 = 0.797], while only 18.49% increase during walking. Adjusting SCBA shoulder strap length significantly altered the rectus abdominis force and L4/L5 reaction force during walking and running. CONCLUSIONS: Results revealed that rectus femoris activity, hip and knee exertion was sensitive to SCBA carriage. The variation of shoulder strap length has potential to influence the risk of low back pain (LBP). PRACTICAL APPLICATIONS: The findings suggest that fire services promote targeting physical training at firefighters' hip and knee regions. Test firefighters in this study were not advisable to adjust their shoulder strap at loose-fitting condition. The compatibility design of the trunk morphology and SCBA back-mounted frame was suggested for the management of LBP.

High-speed electro-optic modulation in topological interface states of a one-dimensional lattice.

Electro-optic modulators are key components in data communication, microwave photonics, and quantum photonics. Modulation bandwidth, energy efficiency, and device dimension are crucial metrics of modulators. Here, we provide an important direction for the miniaturization of electro-optic modulators by reporting on ultracompact topological modulators. A topological interface state in a one-dimensional lattice is implemented on a thin-film lithium-niobate integrated platform. Due to the strong optical confinement of the interface state and the peaking enhancement of the electro-optic response, a topological cavity with a size of 1.6 × 140 µm2 enables a large modulation bandwidth of 104 GHz. The first topological modulator exhibits the most compact device size compared to reported LN modulators with bandwidths above 28 GHz, to the best of our knowledge. 100 Gb/s non-return-to-zero and 100 Gb/s four-level pulse amplitude modulation signals are generated. The switching energy is 5.4 fJ/bit, owing to the small electro-optic mode volume and low capacitance. The topological modulator accelerates the response time of topological photonic devices from the microsecond order to the picosecond order and provides an essential foundation for the implementation of large-scale lithium-niobate photonic integrated circuits.

Bovine pericardium leaflet damage during transcatheter aortic valve crimping: a study of the mechanisms.

Leaflet damage has been documented to occur while deploying a transcatheter aortic valve (TAV) due to mechanical loads during the crimping procedures. In this study, the impact of compressive stress on folded leaflets was measured to investigate the mechanism of traumatic leaflet tissue damage. Numerical simulation of TAV crimping procedure was adapted to calculate stress magnitude and distribution of leaflets. A 20 mm balloon expanding short stent TAV with 0.25 mm thickness leaflets was used in the simulation. Then the calculated stresses were applied on leaflet material (bovine pericardium) samples by loading experiments. Mechanical properties evaluation combined with histological and microscopy observation were used to investigate the tissue damage. The elastic modulus and the tensile strength of the tissue began to decrease significantly at 2 MPa stress and 2.5 MPa stress, respectively. No significant differences were observed at 0-1.5 MPa stress. When the TAV was crimped to 14 Fr and 12 Fr, the 2 MPa greater areas on leaflets increased from 18.17% to 76.96%. 2 MPa compressive stress might be the threshold value for leaflet damage. The TAV crimping size should be paid attention to avoid the compressive stress higher than 2 MPa.

Microstructural and mechanical evaluations of region segmentation methods in classifications of osteonecrosis.

Measuring the location of necrotic lesions is necessary to diagnosis of osteonecrosis. Different region segmentation methods of the femoral head were proposed to quantitatively measure necrotic lesions including Japanese Investigation Committee for Avascular Necrosis (JIC) classification and China-Japan Friendship Hospital (CJFH) classification. Biomechanical methods could bring important information to evaluate the reasonability of these classifications. In this study, microstructural and mechanical properties of trabecular bone were quantitatively analyzed according to the region segmentation methods described in these classifications. Microstructural parameters of trabecular bone were analyzed based on micro-CT scanning. Mechanical properties were measured through Nanoindentation and micro-finite element analysis. It was found that microstructural and mechanical properties of trabecular bone in the middle region was more adaptive to load bearing than the medial and lateral regions according to the CJFH classification; lesions in the middle region could bring more changes to microstructure and stress distribution. According to JIC classification, differences of microstructural and mechanical properties among the three regions were not significant. Biomechanical characteristics of trabecular bones could be better distinguished with CJFH classification.

Idealized conductance: A new method to evaluate stiffness of trabecular bone.

Stiffness is an important parameter to evaluate the condition of trabecular bone in biomechanical and clinical research. Microstructural parameters are commonly used to evaluate stiffness, but the accuracy needs to be improved. In this study, the electrical conductance of trabecular bone was calculated based on an idealized condition: trabeculae were electrically conductive and isotropy, other constituents in the trabecular bone were not considered in the simulation. The idealized conductance was calculated to evaluate the stiffness of trabecular bone, and the accuracy was compared with microstructural parameters. Twenty-one cubic trabecular cubes (5 × 5 × 5 mm3 ) from three femoral heads were investigated. Microstructural parameters were measured through Micro-CT scanning. Nominal elastic modulus (E) and idealized conductance (G) of trabecular cubes were measured through micro-finite element analysis. Bone volume fraction (BV/TV) is the major microstructural parameter that determine the stiffness of trabecular bone. The correlation coefficient between BV/TV and E along three directions were 0.815 (X-axis), 0.729 (Y-axis) and 0.914 (Z-axis). The correlation between G and E were stronger (X-axis: r = 0.986, Y-axis: r = 0.986, Z-axis: r = 0.991). A regression model combining different microstructural parameters was built to evaluate stiffness, but the correlation between them were not significantly improved (X-axis: r = 0.831, Y-axis: r = 0.807, Z-axis: r = 0.905). Compared with microstructural parameters, idealized conductance was a better parameter to evaluate stiffness of trabecular bone.

Influence of Configuration on Stress Distribution of Pulmonary Monocusp Leaflet.

PURPOSE: For the relief of right ventricular outflow tract obstruction in operative treatment of tetralogy of Fallot and other complex congenital heart diseases, transannular monocusp patch operations are often necessary to prevent right ventricular pressure overload and reduce pulmonary regurgitation. However, long-term durability of a monocusp leaflet is unsatisfactory, its failure is believed to be related to mechanical stress, whose distribution is primarily affected by geometric configurations. Therefore, the influence of several geometrical parameters on stress distribution of leaflet is investigated. METHODS: Five parameters affecting leaflet configuration were established: angle between free edge of the leaflet and vessel wall, angle formed by the two end points of free edge, length of the free edge of the leaflet, height of the leaflet, and shape of elliptic conical surface constituting the leaflet surface. The first four parameters were fixed, and two factors were defined to describe the last parameter. Seven models with different values of these factors were analyzed using finite element method at the pressure of the pulmonary artery loaded on the leaflet. RESULTS: The peak stresses of all models occurred at end points of the free edge of the leaflet (tear high-risk regions). The middle of leaflet had the greatest stress gradient and produced tissue wrinkling; this area could be the risk region of calcification. Both factors were noted to influence the stress distribution, and one of the factors could also relieve the wrinkling. CONCLUSIONS: The leaflet of model (1.2_min) had the most even stress distribution and lowest peak principal stress, which was the optimal choice among all the models.

Numerical simulation of haemodynamics and low-density lipoprotein transport in the rabbit aorta and their correlation with atherosclerotic plaque thickness.

Two mechanisms of shear stress and mass transport have been recognized to play an important role in the development of localized atherosclerosis. However, their relationship and roles in atherogenesis are still obscure. It is necessary to investigate quantitatively the correlation among low-density lipoproteins (LDL) transport, haemodynamic parameters and plaque thickness. We simulated blood flow and LDL transport in rabbit aorta using computational fluid dynamics and evaluated plaque thickness in the aorta of a high-fat-diet rabbit. The numerical results show that regions with high luminal LDL concentration tend to have severely negative haemodynamic environments (HEs). However, for regions with moderately and slightly high luminal LDL concentration, the relationship between LDL concentration and the above haemodynamic indicators is not clear cut. Point-by-point correlation with experimental results indicates that severe atherosclerotic plaque corresponds to high LDL concentration and seriously negative HEs, less severe atherosclerotic plaque is related to either moderately high LDL concentration or moderately negative HEs, and there is almost no atherosclerotic plaque in regions with both low LDL concentration and positive HEs. In conclusion, LDL distribution is closely linked to blood flow transport, and the synergetic effects of luminal surface LDL concentration and wall shear stress-based haemodynamic indicators may determine plaque thickness.

Effects of different fluid shear stress patterns on the in vitro degradation of poly(lactide-co-glycolide) acid membranes.

The applications of poly (lactide-co-glycolide) acid (PLGA) for coating or fabricating polymeric biodegradable stents (BDSs) have drawn more attention. The fluid shear stress has been proved to affect the in vitro degradation process of PLGA membranes. During the maintenance, BDSs could be suffered different patterns of fluid shear stress, but the effect of these different patterns on the whole degradation process is unclear. In this study, in vitro degradation of PLGA membranes was examined with steady, sinusoid, and squarewave fluid shear stress patterns in 150 mL deionized water at 37°C for 20 days, emphasizing on the changes in the viscosity of the degradation solution, mechanical, and morphological properties of the samples. The unsteady fluid shear stress with the same average magnitude as the steady one accelerate the in vitro degradation process of PLGA membranes in terms of maximum fluid shear stress and "window" of effectiveness. Maximum fluid shear stress accelerates the in vitro degradation of molecular fragments that diffused out in the solution while the "window" of effectiveness affects too in the early stage. Besides, maximum fluid shear stress and "window" of effectiveness accelerates the in vitro loss of tensile modulus and ultimate strength of the PLGA membranes while the maximum fluid shear stress plays the leading role in the decrease of tensile modulus at the early degradation stage. This study could help advance the degradation design of PLGA membranes under different fluid shear stress patterns for biomedical applications like stents and drug release systems. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 105A: 23-30, 2017.

Hydrolytic Amino Acids Employed as a Novel Organic Nitrogen Source for the Preparation of PGPF-Containing Bio-Organic Fertilizer for Plant Growth Promotion and Characterization of Substance Transformation during BOF Production.

Opportunity costs seriously limit the large-scale production of bio-organic fertilizers (BOFs) both in China and internationally. This study addresses the utilization of amino acids resulting from the acidic hydrolysis of pig corpses as organic nitrogen sources to increase the density of TrichodermaharzianumT-E5 (a typical plant growth-promoting fungi, PGPF). This results in a novel, economical, highly efficient and environmentally friendly BOF product. Fluorescence excitation-emission matrix (EEM) spectroscopy combined with fluorescence regional integration (FRI) was employed to monitor compost maturity levels, while pot experiments were utilized to test the effects of this novel BOF on plant growth. An optimization experiment, based on response surface methodologies (RSMs), showed that a maximum T-E5 population (3.72 × 108 ITS copies g-1) was obtained from a mixture of 65.17% cattle manure compost (W/W), 19.33% maggot manure (W/W), 15.50% (V/W)hydrolytic amino acid solution and 4.69% (V/W) inoculum at 28.7°C after a 14 day secondary solid fermentation. Spectroscopy analysis revealed that the compost transformation process involved the degradation of protein-like substances and the formation of fulvic-like and humic-like substances. FRI parameters (PI, n, PII, n, PIII, n and PV, n) were used to characterize the degree of compost maturity. The BOF resulted in significantly higher increased chlorophyll content, shoot length, and shoot and root dry weights of three vegetables (cucumber, tomato and pepper) by 9.9%~22.4%, 22.9%~58.5%, 31.0%~84.9%, and 24.2%~34.1%, respectively. In summary, this study presents an operational means of increasing PGPF T-E5 populations in BOF to promote plant growth with a concomitant reduction in production cost. In addition, a BOF compost maturity assessment using fluorescence EEM spectroscopy and FRI ensured its safe field application.

Biomechanism of impact resistance in the woodpecker's head and its application.

The woodpecker does not suffer head/eye impact injuries while drumming on a tree trunk with high acceleration (more than 1000×g) and high frequency. The mechanism that protects the woodpecker's head has aroused the interest of ornithologists, biologists and scientists in the areas of mechanical engineering, material science and electronics engineering. This article reviews the literature on the biomechanisms and materials responsible for protecting the woodpecker from head impact injury and their applications in engineering and human protection.