Greater Stiffness Research Articles

Abstract 12869: Association of Statin Therapy and Progression of Arterial Stiffness in the Multi-ethnic Study of Atherosclerosis

Background: Statin therapy may alter arterial stiffness by decreasing the low density lipoprotein cholesterol (LDL-C) content within blood vessel walls and reducing inflammation. Progression of arterial stiffness with prolonged statin treatment is not clear. Methods: The subset of MESA participants (n=1,225) with comprehensive data on statin use who underwent B-mode carotid ultrasound at baseline (visit 1) and after (mean ± SD) 9.3±0.7 years (visit 5) was analyzed. Arterial stiffness was measured using carotid distensibility coefficient (DC) and Young’s elastic modulus (YEM) at MESA exam 1 and 5. Linear regression models evaluated associations of ten-year change in DC and YEM with statin treatment duration and intensity during visits 1-4. Models were adjusted for age, sex, ethnicity, systolic blood pressure (SBP), diabetes status, alcohol use, smoking, and lipid profiles. Results: At baseline, participants were 66.5±8.1 years of age, 41% female, 36% Caucasian, 30% African American, 13.7% Asian American, and 20.0% Hispanic, with LDL-C of 149.5±14.5 mg/dL; DC was 2.88×10-3±1.28×10-3 mmHg-1, YEM was 1659±1056 mmHg. Participants not on statin therapy at any visit had greater baseline arterial stiffness measures compared to participants who were treated at all visits (YEM: 1,724 ±993 mmHg vs 1,457 ±776 mmHg; p=0.0003; DC: 2.72 ±1.22×10-3 mmHg-1 vs 3.22 ±1.33×10-3 mmHg-1; p<0.0001). In unadjusted models, neither duration nor intensity of statin therapy was associated with changes in arterial stiffness measures over 10 years. Fully adjusted multivariable linear regression models showed associations with age and SBP but demonstrated no significant associations between DC and YEM and treatment duration or any statin intensity (table). Conclusions: Statin therapy was not associated with progression of carotid artery distensibility and elasticity over nearly a decade of follow up regardless of treatment duration or dose intensity.

Lower-limb stiffness mediates speed but not turning angle during unplanned side-step cutting

An inability to pre-plan a side-step cutting maneuver results in a greater reduction in speed and shallower cut angle. Although leg stiffness has not been directly quantified in cutting, indirect evidence suggest that greater stiffness may benefit cutting speed, but lower stiffness may benefit cut angle. No studies have investigated if stiffness causally mediates the relationship between anticipation, cutting speed and angle. The aims of the present study were to determine the influence of anticipatory cues on leg stiffness, and quantify the mediation effects of stiffness on cutting speed and angle. Seventeen healthy participants performed a 45° cut at an approach speed of 4 m/s. Leg stiffness (% bodyweight/leg length [BW/LL]), cutting angle and change in running speed between initial contact and toe-off of the cut were calculated. Causal mediation analysis was performed with anticipatory cues as the independent variable, cutting speed and angle as the dependent variables, and stiffness as the mediator. Unanticipated cutting significantly increased leg stiffness (β=3.82%BW/LL,P=0.005) compared to anticipated cutting. The average causal mediation effect of stiffness on cutting angle was not significant (P = 0.68). The average causal mediation effect of stiffness on cutting speed was significant (−0.02 m/s [95%CI −0.04 to 0.00 m/s, P = 0.016). Reduced preplanning time in cutting increased leg stiffness. Alterations in leg stiffness only explained the change in speed, and not angle, associated with cutting under different anticipatory cues. Loss of speed when cutting is unplanned may be mitigated by improving leg stiffness.

First-principles investigation on the structural, electronic, mechanical and thermodynamic properties of binary phase in Mg-1Si-3RE(RE = La, Ce) alloys

First-principles calculations method were employed to investigate the structural, electronic, elastic and thermodynamic properties of binary rare earth phases CeSi2 and LaSi2 compared with Mg2Si phase in Mg-1Si-3RE(RE = La, Ce) alloys. The calculated results of cohesive energy and enthalpy formation reveal that CeSi2 has the greatest structural stability and alloying ability. The calculated values of elastic constants show that LaSi2 has the greatest stiffness, followed by Mg2Si and CeSi2. The plasticity decreases in the following order: CeSi2 > LaSi2 > Mg2Si. The analysis on elastic anisotropy show that both CeSi2 and LaSi2 exhibit isotropic in AG and AE, while show anisotropy in AB. Calculated results of Debye temperature indicating that Mg2Si possesses the highest thermal stability among three phases. Current investigation provides a comprehensive understanding of the strengthening mechanism of rare earth elements and helps to optimize the mechanical properties of Mg-Si series alloys.

Planar reinforcement by sheet type stiffeners for fused deposition modeling

This paper presents a planar reinforcement (PR) method for fused deposition modeling. In the proposed PR method, planar reinforcing parts, such as metal sheets or carbon fiber film (CFF), are placed inside the structures laminated by additive manufacturing. The tensile, bending stiffness, and vibration characteristics of the planar reinforced structures were evaluated using mechanical tests (tensile, bending, and impact hammer tests). The mechanical properties of the planar reinforced specimens were compared with those of other specimens built by polylactic acid (PLA) and short carbon fiber reinforcement thermoplastic (SFRTP) filaments. Results show that the planar reinforced structures have greater stiffness than the other specimens. The experimental results are analyzed using the mixture equation of composite materials, and the difference in reinforcement effect caused by metal and CFF sheets is discussed.

Study on bearing stiffness characteristics with residual stress in carburized layer

In this study, a layering method of carburized ring is presented. A finite element (FE) model for analyzing bearing stiffness characteristics is established considering the residual stress in the carburized layer. The residual stress in the carburized layer of a double-row conical roller bearing is tested and the influence of the distribution of residual stress in carburized layer on the bearing stiffness is investigated. Results show that the residual stress in the carburized layer increases the contact stiffness of the bearing by 5% in the low-load zone and 3% in the high-load zone. The radial stiffness of the bearing is increased by 5% in the low-load zone and 3% in the high-load zone. The axial stiffness is increased by 6%, and the angular stiffness increased by 4%. The larger the thickness of the carburized layer, the greater the residual compressive stress in the carburized layer, the deeper the position of the maximum residual stresses in the carburized layer will lead to the greater stiffness of the bearing.

Abiotic and biotic degradations of a LDPE blend in soil of South Brazil landfill

Polyethylene degrades slowly when discarded in the environment and exposed to natural weathering. A solution to this problem is the incorporation of additives to accelerate its biodegradation. In the present study, a biodegradable low-density polyethylene (LDPE) blend was obtained by the mixture of LDPE with a biodegrading additive (8% w/w) and the effect of accelerated weathering on biodegradation process was assessed. Chemical, mechanical, thermal, and morphological properties of non-aged and aged samples were studied. Results showed that aging process caused changes on structural characteristics (insertion of functional groups), morphological (appearance of micro-cracks and increased roughness), mechanical (greater stiffness and loss of plasticity) and thermal (lower degree of crystallinity and thermal stability) properties. The presence of biodegrading additive contributed to aging process, since polar functional groups were inserted into additive exposed to soil underwent greater degradation than their non-aged counterparts. CO2 production of aged LDPE blend demonstrated that accelerated weathering influences biodegradation process. In this work, due to availability of O2 gas, aerobic microorganisms can be the main responsible by the material deterioration, leading to production of microbial biomass, CO2 and H2O. Thus, the results of biodegradation (166 days) obtained in this work are promising, once it was reached a natural soil from South Brazil landfill.

Monitoring the mechanical properties of the solid electrolyte interphase (SEI) using electrochemical quartz crystal microbalance with dissipation

Stable solid electrolyte interphase (SEI) has been well established to be critical for the reversible operation of Li (ion) batteries, yet our understanding of its mechanical properties currently remains incomplete. Here, we used an electrochemical quartz crystal microbalance combined with dissipation monitoring (EQCM-D) to investigate SEI formation. By quantitatively estimating in-situ, the change in mass, shear modulus, and viscosity of the SEI, we show that the SEI formation in propylene carbonate (PC)- and ethylene carbonate/diethyl carbonate (EC/DEC)-based electrolytes involves the growth of a rigid layer followed by a viscoelastic layer, whereas a distinct “one-layer” rigid model is applicable to the SEI formulated in tetraethylene glycol dimethyl ether (TEGDME)-based electrolyte. With the continuous formation of the SEI, its shear modulus decreases accompanied by an increase in viscosity. In TEGDME, the lightest/thinnest SEI (mass lower than in PC by a factor of nine) yet having the greatest stiffness (more than five times that in PC) is obtained. We attribute this behavior to differences in the chemical composition of the SEIs, which have been revealed by tracking the mass-change-per-mole-of-electron-transferred using EQCM-D and further confirmed by X-ray photoelectron spectroscopy.

The Loop 'n' Tack Knot: Biomechanical Analysis of a Novel Suture Technique for Proximal Biceps Tenodesis.

Background:Secure tendon grasping is critical to the success of any tenodesis procedure. Several techniques currently used for tendon grasping can result in longitudinal splitting of the tendon, causing construct failure and failure of the tenodesis.Purpose:To compare the Loop ’n’ Tack knot as a tendon-grasping technique with other common suture techniques. We investigated the biomechanical strength and mode of failure.Study Design:Controlled laboratory study.Methods:Eleven matched pairs of proximal biceps were harvested from fresh-frozen cadaveric shoulders. One tendon from each pair was stitched using 1 of 4 different techniques. The suture techniques evaluated included the Loop ’n’ Tack with 2 different types of high-strength nonabsorbable suture, a double half-racking stitch, and a Krakow stitch. Samples were cyclically loaded between 5 and 20 N for 100 cycles, followed by a pull to failure at 33 mm/s.Results:The Loop ’n’ Tack techniques were equivalent to the double half-racking and Krakow techniques for load to ultimate failure (P = .817 and P = .984, respectively). The double half-racking technique was the stiffest construct, which was significantly greater than the second-stiffest group, the Loop ’n’ Tack method with both FiberLink suture (P = .012) and SutureTape (P = .002), which had greater stiffness than the Krakow group (P < .001). The most common failure mode for the Loop ’n’ Tack stitch was suture breakage compared with the Krakow and double half-racking methods, where the most common mode of failure was suture pullout from the tendon (P < .001).Conclusion:Biomechanical testing found that the Loop 'n’ Tack techniques had similar ultimate load to failure values when compared with the double half-racking and Krakow methods. Mode-of-failure analysis showed that the Loop 'n’ Tack construct typically failed by suture breakage, whereas the other techniques failed by suture pullout.Clinical Relevance:The Loop 'n’ Tack technique allows for secure grasping of tissue without the need for externalization of the tendon. This technique may be beneficial in compromised or poor-quality tissue without reducing overall pullout strength when compared with a standard half-racking or Krakow stitch.

Biomechanical Modeling of Connecting Intermetacarpal K-Wires in the Treatment of Metacarpal Shaft Fractures.

Clinical series have been published using the configuration of 2 intercarpal Kirschner wires (K-wires) adjacent to the fracture being connected, but biomechanical analysis is lacking. The objective of this pilot biomechanical study was to model and compare the effects of externally connecting 2 intermetacarpal K-wires for the stabilization of transverse metacarpal shaft fractures. Our research hypothesis was that the connected constructs would be stiffer than the unconnected K-wires. A 3-dimensional computer-based model of small finger transverse metacarpal fracture stabilization was designed with 3 transverse 1.1 mm K-wires being anchored to the adjacent metacarpal. Three arrangements were tested: all 3 K-wires in parallel, the middle K-wire angled toward the proximal wire, and the middle angled K-wire being rigidly fixed to the proximal K-wire. The proximal wire was proximal to the fracture. A finite element analysis was performed by applying a cantilever force of 100 N at the head of the metacarpal. The metacarpal was considered to be uniform in composition with parameters typical for human bone. Kirschner wire parameters for stainless steel were used. Force (N) versus displacement was measured. The configuration with the middle angled K-wire being rigidly fixed to the proximal K-wire showed greater stiffness (12 N/mm) than nonattached constructs. The connected construct was 2.3 times more stiff than the unattached parallel construct and 2.5 times more stiff than angling the middle K-wire without attachment. In a computer model simulation, our results show that attaching 2 K-wires adjacent to the fracture provides more than twice the stiffness of unconnected K-wires.

Acoustic Radiation Force Impulse (ARFI) elastography imaging of equine distal forelimb flexor structures

ABSTRACT This study set out to determine normal values for acoustic radiation force impulse (ARFI) elastography of the superficial digital flexor tendon, deep digital flexor tendon, accessory ligament of the deep digital flexor tendon and suspensory ligament in horses. Twenty-four horses were submitted to conventional sonographic assessment and elastography imaging (quantitative ARFI method) of distal forelimb tendons and ligaments at nine anatomical regions. Elastograms depicted tendons and ligaments in orange to red tones consistent with greater stiffness. Shear wave velocity was higher in the longitudinal compared to the cross-sectional plane but did not differ significantly between the left and right forelimbs. The suspensory ligament was stiffer compared to remaining structures in the cross-sectional plane. Ligaments were stiffer than tendons and the deep digital flexor tendon was stiffer than the superficial digital flexor tendon in the longitudinal plane. Target structures were stiffer in male compared to female horses and stiffness tended to increase with age. ARFI elastography proved to be a feasible and reproducible imaging modality for assessment of distal forelimb tendons and ligaments in horses. Qualitative features derived from stiffness quantification in these structures can be applied to horses with musculoskeletal disorders, as well as to other animal species.

Non-Iterative Semi-Implicit Integration Method for Active Distribution Networks With a High Penetration of Distributed Generations

With the increasing penetration of distributed generations (DGs), the equations governing active distribution networks (ADNs) exhibit stronger nonlinearity and greater stiffness. Additionally, the uncertainties associated with DGs mean that ADNs face more frequent and diversified disturbances. The novel properties of ADNs exacerbate the instabilities and computational burdens on iterations of time-domain simulation when using traditional explicit and implicit integration algorithms. This article proposes a novel semi-implicit integration method incorporating an adaptive Jacobian matrix to solve the differential equations (DEs) governing ADNs, resulting in a non-iterative technique with good numerical stability. The proposed approach simultaneously combines the advantages of both explicit and implicit methods. Moreover, a parameter optimization strategy that comprehensively considers stability, efficiency, and accuracy conditions and an adaptive Jacobian matrix update strategy are developed to further improve the numerical performance of the proposed method. Finally, the proposed method is validated using a modified 33-node system and a practical 436-node distribution system. The simulation results demonstrate the prominent advantages of the proposed method in terms of stability and efficiency compared with the modified Euler and trapezoidal methods.

Flexural Behaviour of Delta Hollow Flange Steel Beam with and without stiffeners

In recent years of construction, steel has been considered as the most commonly used construction materials. Cold Formed steel has many structural benefits like high strength, greater stiffness, high ductility with excellent structural properties and fire resistance. The Cold formed steels are usually used in day by day in residential, commercial and industrial buildings around world. It also reduce the cross section of an element. Steel structure are faster in construction. The main aim of this paper is to study new steel beam. Rather than normal I-shaped beam, it is innovated to form Triangular Hollow Flange Beam (THFB) with slender web using required welded connection to improve the flexural capacity. THFB is also called as Delta Hollow Flange Beam (DHFB). Hollow Tubular Flange Beam provide more strength, stiffness, and stability than a flat plate flange with the same amount of steel. Flanges resist the applied moment, whereas web plates resist the induced shearing force. To improve the flexural resistance the use of the stiffeners also plays an important role, hence the flexural behavior of DHFB with the addition of transverse stiffeners has been investigated in this research work. Initially the section for the research has been chosen, Ultimate load has been calculated manually, Weld used for the sections are designed and they were analyzed through the Finite Element software called ‘ANSYS’. Later, five different specimen which includes specimen with and without stiffeners has been tested experimentally. The flexural test was carried out, along with that other properties like Ductility properties also calculated. From both analytical and experimental study DHFB shows positive results. They were highly used in various application which includes purlins, girts, portal frames and steel frame structures. Steel structure are faster in construction.

Impact of Reduced Graphene Oxide on structure and properties of polyethylene rich binary systems for performance-based applications

This study discloses, for the first time, the impact of Graphene Oxide (GO) chemical reduction on structure and performance of a Polyethylene (PE) rich biphasic system, with Polypropylene (PP) representing the morphology tunable micro phase. A 2% weight fraction of the interface modifier Reduced Graphene Oxide (RGO), together with a strategic mixing of the components, led to RGO high exfoliation and selective localization at the PE/PP interface, demonstrated by Transmission Electron Microscopy (TEM). This resulted into an extremely fine morphology for the ternary system PE/PP/RGO, with micro phase having a uniform droplet diameter distribution, proven by Scanning Electron Microscopy (SEM). The material had greater stiffness, toughness, storage and loss modulus than those of virgin PP, with strength being similar to the one of neat PP. This study provides industrial sectors, such as transportation and energy, with the potential to replace PP rich products with those made of a cheaper, simpler, yet performant PE.

Bending experiment on a novel configuration of composite system using rebar as shear connectors with partially encased cold-formed steel built-up beams

In order to achieve greater ductility and strength, as well as to produce a more economical design, a novel composite beam and floor system have been developed to achieve higher strength and ductility, as well as to yield a more economical design purpose. This paper has put focus on this newly developed composite beam system which consists of a profiled metal decking slab made with self-compacting concrete (SCC). It has been joined cold-formed steel (CFS) built-up beams. These beams have been infilled with SCC by means of U-shaped rebar used as shear connectors. The researcher, in order to construct an open section, put together two CFS C-lipped channel sections in a back-to-back formation, and to construct a closed section, the formation was made to be toe-to-toe. The flexural behaviour of the partly encased composite beam was evaluated through experimentation by the researchers. So that the researchers could observe the failure modes and flexural capacity of the construction, a four-point bending test procedure was performed on two samples taking into consideration both closed and open built-up beam sections. The results of the test demonstrated that the open sections were able to exhibit a 24 percent higher ultimate moment capacity as well as greater stiffness and higher vertical deflection. As can be seen from the results of the experimental bending test, the built-up design had a great impact on the capacity and deflection of the section, and the section that was encased was able to reach the ultimate strength when the proposed shear connector was placed in the composite action. In order to validate the present test results, the design and analysis of the new composite beams have been evaluated.

Experimental Flexural Behavior of Composite Beam using Cold Formed Hollow Square Section

Structural hollow sections have excellent properties for resisting static loads, with regard to buckling, bi-axial bending and torsion. Structural hollow sections are generally used for truss components, considering greater stiffness and lateral strength. A square hollow section truss has about two third of surface area of same size I section. Hollow section truss may have smaller members as a result of higher structural efficiency. Construction of composite beam commonly includes I section. This paper deals with comparison of commonly used hot rolled or welded I composite section with cold formed hollow RHS and SHS composite section with respect to flexure and shear. Flexural tests were conducted to evaluate the structural behavior of the proposed composite beams. Two different steel sections were used for this study with nominal concrete strength of 30 MPa. The composite beams were tested under concentrated two points loading. The test results were plotted and compared with analytical results. The mid span deflections and slip were recorded for both composite beams. Buckling modes for both composite beams were identified. comparisons have been carried out between predicted beam strength as provided by Eurocode -4 and experimental test results. Sectional properties are checked for cold formed hollow square section using EN 1993-1-3.

Interference Behaviour in Steel Concrete Composite Construction

The objective of this study is to obtain the most effective utilization of steel and concrete by the method of composite construction through obtaining proper interaction between steel and concrete. Composite construction has various advantages compared to normal method of non composite construction. It provides greater stiffness and provides good strength against bending. By providing proper interaction we can obtain a more economical section and sections with good structural properties It is also a fast track construction practice. Both theoretical and software analysis of normal composite section and a section with profiled steel sheeting have been presented. After analysis it is found that shear connectors and profiled steel sheeting are advantageous in strength increment, reducing deflection and other factors.

3D-printed ceramic triply periodic minimal surface structures for design of functionally graded bone implants

Stress shielding is one of the main problems that lead to bone resorption and revision surgery after implantation. Most of the commercially available metallic non-porous bone implants have a much greater stiffness than the native human bones and are prone to cause stress-shielding. With an open cell structure and intricate architecture, hyperbolic minimal surfaces offer several advantages such as less stress concentration, high permeability and high surface area to volume ratio, thus providing an ideal environment for cell adhesion, migration, and proliferation. This paper explores the use of porous bone implant design based on Triply Periodic Minimal Surfaces (TPMS) which is additively manufactured with ceramic material (Alumina) using Lithography-based Ceramics Manufacturing (LCM) technology. A total of 12 different primitive surface structure unit cells with pore size in the range of 500–1000 μm and porosity above 50% were considered. This is one of the earliest studies reporting the 3D printing of TPMS-based structures using ceramic material. Our results suggest that the choice of material and a porous TPMS-based design led to fabrication of structures with a much lesser compressive modulus comparable with the native bone and hence could potentially be adopted for bone implant design to mitigate the stress-shielding effect.

Thermoresponsive starch-based particle-stabilized Pickering high internal phase emulsions as nutraceutical containers for controlled release

Pickering high internal phase emulsions (HIPEs) stabilized solely by bioderived starch-based particles hold potential for application in the food and pharmaceutical fields. This paper reports the use of a thermoresponsive 2-hydroxy-3-butoxypropyl starch (HBPS) particle as a representative natural biocompatible material for use as an effective stabilizer for HIPE formation. HBPS is synthesized by using butyl glycidyl ether as a hydrophobic reagent to change the hydrophobic–hydrophilic balance of starch, and then starch-based particles are fabricated by a simple nanoprecipitation procedure. The size of particles increased with an increase in temperature, and the particles are essentially monodisperse with a PDI of about 0.1 when the temperature was above 15 °C. These HBPS particles were subsequently used as an effective stabilizer to fabricate stable oil-in-water (o/w) Pickering HIPEs with an internal phase volume of 80% at different stabilizer concentrations. The results demonstrated that increasing the particle concentration is conducive to the formation of stable Pickering HIPEs with greater stiffnesses. In addition, the nutraceutical material (β-carotene) was encapsulated into HIPEs and in vitro release experiments revealed that the release in this system can be controlled by adjusting the temperature.

Bilaminar Mechanics of the Human Optic Nerve Sheath

ABSTRACT Purpose/Aim The adult human optic nerve (ON) sheath has recently been recognized to be bilaminar, consisting of inner layer (IL) and outer layer (OL). Since the ON and sheath exert tension on the globe in large angle adduction as these structures transmit reaction force of the medial rectus muscle to the globe, this study investigated the laminar biomechanics of the human ON sheath. Materials and Methods Biomechanical characterization was performed in ON sheath specimens from 12 pairs of fresh, post-mortem adult eyes. Some ON sheath specimens were tested completely, while others were separated into IL and OL. Uniaxial tensile loading under physiological temperature and humidity was used to characterize a linear approximation as Young’s modulus, and hyperelastic non-linear behavior using the formulation of Ogden. Micro-indentation was performed by imposing small compressive deformations with small, hard spheres. Specimens of the same sheaths were paraffin embedded, sectioned at 10 micron thickness, and stained with van Gieson’s stain for anatomical correlation. Results Mean (± standard error of the mean, SEM) tensile Young’s modulus of the inner sheath at 19.8 ± 1.6 MPa significantly exceeded that for OL at 9.7 ± 1.2 MPa; the whole sheath showed intermediate modulus of 15.4 ± 1.1 MPa. Under compression, the inner sheath was stiffer (7.9 ± 0.5 vs 5.2 ± 0.5 kPa) and more viscous (150.8 ± 10.6 vs 75.6 ± 6 kPa s) than outer sheath. The inner sheath had denser elastin fibers than outer sheath, correlating with greater stiffness. Conclusions We conclude that maximum tensile stiffness occurs in the elastin-rich ON sheath IL that inserts near the lamina cribrosa where tension in the sheath exerted during adduction tethering may be concentrated adjacent the ON head.

A biomechanical comparison of single- versus double-threaded cannulated screws for femoral neck fractures of Pauwels type III

Objective To compare the biomechanical performance between the single- versus double-threaded cannulated screws in the treatment of femoral neck fractures of Pauwels type Ⅲ. Methods Models of femoral neck fracture of Pauwels type Ⅲ (70°) were made of the Sawbone synthetic composite femurs. All specimens were divided into 2 groups (n=12). Group A was fixated with single-threaded cannulated screws and group B with double-threaded cannulated screws, both in an inverted triangle configuration. The screws ranged from 90 to 95 mm in length and from 7.3 to 7.5 mm in diameter. All the specimens were subjected to axial stiffness and failure load tests with 7° valgus (simulating normal two-legged weight-bearing stance) and 25° valgus (simulating normal one-legged weight-bearing stance) and torsion test as well. The 2 groups were compared in the torques at axial stiffness angles of 1°, 2°, 3°, 5° and 7°. Results Group B had significantly greater axial stiffness at 7° valgus and 25° valgus (89±26 N/mm and 128±37 N/mm) and failure load (1,154±368 N) than group A did (36±12 N/mm and 47±16 N/mm; 688±94 N) (P< 0.05). The torques increased with the increase in rotation angle in both groups. However, the torques in group B (3.26±0.96, 4.16±1.23, 4.64±1.13, 5.59±1.26 and 6.53±1.47 N·m) were all significantly larger than in group A (1.44±0.19, 2.03±0.41, 2.33±0.62, 2.74±0.87 and 3.05±1.07 N·m) (P<0.05). Conclusion Double-threaded cannulated screws may provide better biomechanical stability than single-threaded ones, due to their substantial improvement in anti-compression and anti-rotation performance. Key words: Femoral neck fractures; Fracture fixation, internal; Bone nails; Biomechanics; Pauwels Ⅲ