Effect of angular stability and other locking parameters on the mechanical performance of intramedullary nails

2015 ◽  
Vol 60 (2) ◽  
Author(s):  
Stefanie Hoffmann ◽  
Claus Gerber ◽  
Geert von Oldenburg ◽  
Manuel Kessler ◽  
Daniel Stephan ◽  
...  
Keyword(s):  
Mechanical Performance ◽  
Angular Stability ◽  
Generic Model ◽  
Mechanical Stiffness ◽  
Intramedullary Nails ◽  
Optimal Arrangement ◽  
Locking Screws ◽  
Loading Modes ◽  
Im Nailing ◽  
Locking Screw

AbstractTo extend the indications of intramedullary nails for distal or proximal fractures, nails with angle stable locking options have been developed. Studies on the mechanical efficacy of these systems have been inconsistent likely due to confounding variables such as number, geometry, or orientation of the screws, as well as differences in the loading mode. Therefore, the aim of this study was to quantify the effect of angular stability on the mechanical performance of intramedullary nails. The results could then be compared with the effects of various locking screw parameters and loading modes. A generic model was developed consisting of artificial bone material and titanium intramedullary nail that provided the option to systematically modify the locking screw configuration. Using a base configuration, the following parameters were varied: number of screws, distance and orientation between screws, blocking of screws, and simulation of freehand locking. Tension/compression, torsional, and bending loads were applied. Stiffness and clearance around the zero loading point were determined. Angular stability had no effect on stiffness but completely blocked axial clearance (p=0.003). Simulation of freehand locking reduced clearance for all loading modes by at least 70% (p<0.003). The greatest increases in torsional and bending stiffness were obtained by increasing the number of locking screws (up to 80%, p<0.001) and by increasing the distance between them (up to 70%, p<0.001). In conclusion, our results demonstrate that the mechanical performance of IM nailing can be affected by various locking parameters of which angular stability is only one. While angular stability clearly reduces clearance of the screw within the nail, mechanical stiffness depends more on the number of screws and their relative distance. Thus, optimal mechanical performance in IM nailing could potentially be obtained by combining angular stability with optimal arrangement of locking screws.

scholarly journals Reconfigurable honeycomb metamaterial absorber having incident angular stability

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Javad Shabanpour ◽  
Sina Beyraghi ◽  
Homayoon Oraizi
Keyword(s):  
Electromagnetic Interference ◽  
Oblique Incidence ◽  
Mechanical Performance ◽  
Incident Angle ◽  
Normal Incidence ◽  
Metallic Phase ◽  
Metamaterial Absorber ◽  
Angular Stability ◽  
Ohmic Losses ◽  
Potential Applications

Abstract Ultrawide-angle electromagnetic wave absorbers with excellent mechanical properties are required in many diverse applications such as sensing, and stealth technologies. Here, a novel 3D reconfigurable metamaterial absorber (MMA) consisting of honeycomb and VO2 films is proposed. The proposed MMA exhibits a strong absorptivity above 90% in the widest incident angle up to $$87^\circ $$ 87 ∘ for TM- and TE polarized oblique incidences for THz wave propagating in yoz-plane. Under normal incidence, when VO2 films are in the insulating state, the proposed absorber exhibits high absorptivity in the frequency band of 1–4 THz. By increasing the temperature of the whole structure, the structural transformation of VO2 occurs and turns into the metallic phase. We have shown that under oblique incidence, the ohmic losses of VO2 films especially those parallel to the direction of the incident electric field are the most important absorption principles of the proposed MMA. Due to the ultra wide-angle absorption (angular stability) and mechanical performance, it is expected that the presented MMA may find potential applications, such as camouflage technologies, electromagnetic interference, imaging, and sensing. To the best knowledge of authors, the proposed MMA configuration exhibits the absorptivity in the widest incident angle ever reported.

scholarly journals Effect of semi-rigid locking screws on the stiffness of a fracture-fixation construct: A conceptual finite-element study

2019 ◽  
Vol 11 (6) ◽  
pp. 168781401985457
Author(s):  
Xiao-Hua Pan ◽  
Wen-Chuan Chen ◽  
Kun-Jhih Lin ◽  
Kang-Ping Lin ◽  
Cheng-Lung Tsai ◽  
...  
Keyword(s):  
Compressive Load ◽  
Skin Incision ◽  
Delayed Union ◽  
Bone Plate ◽  
Long Bone ◽  
Structural Stiffness ◽  
Locking Screws ◽  
Plate Length ◽  
Working Length ◽  
Locking Screw

Strong stiffness provided by locking-plate system has resulted in nonunion and delayed union for long bone fracture. Longer bone plate can lengthen the working length to reduce the structural stiffness of the fixation device but will enlarge skin incision. Using the semi-rigid locking screw may be helpful but the efficacy was unclear. In simulated fracture model, four rigid locking screws were continually inserted beneath the fracture gap. The other four rigid/semi-rigid locking screws were equally distributed or concentrated at screw holes superior to the fracture gap. Axial compressive load was exerted to compare the biomechanical performance under various screw configurations and plate working length. Results revealed that using the semi-rigid locking screws, the structural stiffness of the fixation structure were lowered by 29.5%–45.1% comparing to the model with the same screw configuration using rigid locking screws. Semi-rigid screw models with shorter working length represented comparable flexibility of the fixation structure to the rigid locking screw model with longer working length. Compared to rigid locking screw, semi-rigid locking screw may provide similar flexibility with shorter bone plate, which may be beneficial to reduce the required plate length so that the skin incision may be minimized for fracture reduction.

scholarly journals Finite Element Analysis on Acoustic and Mechanical Performance of Flexible Perforated Honeycomb-Corrugation Hybrid Sandwich Panel

2021 ◽  
Vol 2021 ◽  
pp. 1-14
Author(s):  
Jiaming Hu ◽  
Junyi Wang ◽  
Yu Xie ◽  
Chenzhi Shi ◽  
Yun Chen
Keyword(s):  
Finite Element ◽  
Sandwich Panel ◽  
Mechanical Performance ◽  
Mechanical Energy ◽  
Low Frequency ◽  
Rigid Wall ◽  
Acoustic Metamaterials ◽  
Mechanical Stiffness ◽  
Element Analysis ◽  
Low Frequencies

Since proposed, the perforated honeycomb-corrugation sandwich panel has attracted a lot of attention due to its superior broadband sound absorption at low frequencies and excellent mechanical stiffness/strength. However, most existing studies have assumed a structure made of high-strength materials and studied its performance based on the ideal rigid-wall model with little consideration for acoustic-structure interaction, thereby neglecting the structural vibrations caused by the material’s elasticity. In this paper, we developed a more realistic model considering the solid structural dynamics using the finite element method (FEM) and by applying aluminum and rubber as the structural material. The enhancement of the low-frequency performance and inhibition of broadband absorption coexisted in low-strength rubbers, implying a compromise in the selection of Young's modulus to balance these two influences. Further analysis on thermal-viscous dissipation, mechanical energy, and average structural stress indicated that the structure should work right below the resonant frequency for optimization. Based on these findings, we designed a novel aluminum-rubber composite structure possessing enhanced low-frequency absorption, high resistance to shear load, normal compression, and thermal expansion. Our research is expected to shed some light on noise control and the design of multifunctional acoustic metamaterials.

Validations of Computer-Assisted Orthopaedic Surgical System for insertion of distal locking screws for intramedullary nails

2004 ◽  
Vol 1268 ◽  
pp. 614-619 ◽  
Author(s):  
Sabur Malek ◽  
Roger Phillips ◽  
Amr Mohsen ◽  
Warren Viant ◽  
Mike Bielby ◽  
...  
Keyword(s):  
Computer Assisted ◽  
Intramedullary Nails ◽  
Distal Locking ◽  
Locking Screws ◽  
Surgical System

Biomechanical Testing of the Compressive Strength of Various Distal Locking Screw Options for Intramedullary Nails in the Treatment of Tibia Fractures

2011 ◽  
Author(s):  
Fred Xavier ◽  
Elan Goldwyn ◽  
Westley T. Hayes ◽  
Alexandra Carrer ◽  
Max Berdichevsky ◽  
...  
Keyword(s):  
Testing Machine ◽  
Biomechanical Testing ◽  
Intramedullary Nails ◽  
Group Iii ◽  
Distal Locking ◽  
Locking Screws ◽  
Distal Interlocking ◽  
Group I ◽  
Tibia Fractures ◽  
Torsional Stability

Treatment of distal third tibia fractures remains challenging. New intramedullary nails provide torsional stability by using distal interlocking screws. In this study we attempted to determine the most biomechanically stable number and configuration of distal locking screws. The distal part of human cadaveric tibia bones was nailed using a tibial nail (Stryker T2). Distal locking was performed in three different configurations: (a) Group I: 2 screws in the medio-lateral (ML) direction, (b) Group II: 1 ML screw and 1 Screw in the antero-posterior (AP) direction, and (c) Group III: 2 ML screws and 1 AP screw. The specimens were then mounted onto a mechanical testing machine (Instron) and tested in compression. The load carrying capacity of the samples from Group III with these locking screws was higher than Group I & II, although this difference was not statistically significant.

scholarly journals Biomechanical Comparison of Two Locking Plate Constructs Under Cyclic Loading in Four-Point Bending in a Fracture Gap Model: Two Screws versus Three Screws Per Fragment

2019 ◽  
Vol 32 (01) ◽  
pp. 059-066 ◽  
Author(s):  
Sophie Palierne ◽  
Baptiste Froidefond ◽  
Pascal Swider ◽  
André Autefage
Keyword(s):  
Relative Displacement ◽  
Bending Test ◽  
Test Range ◽  
Locking Screws ◽  
Four Point Bending ◽  
Plate Fracture ◽  
The Difference ◽  
Number Of Cycles ◽  
Biomechanical Comparison ◽  
Locking Screw

Objectives The number of locking screws required per fragment during bridging osteosynthesis has not been fully determined in the dog. The purpose of this study was to assess the survival of two constructs, with either two or three screws per fragment, under cyclic bending. Methods A 10-hole, 3.5-mm stainless steel locking compression plate was fixed 1 mm away from a bone surrogate in which the fracture gap was 47 mm. Two groups of 10 constructs, prepared with either two or three bicortical locking screws placed at the extremities of each fragment, were tested in a load-controlled 4-point bending test (range 0.7 to + 7 Nm) until failure. Results The 3-screw constructs were stiffer than the 2-screw constructs (19.73 ± 0.68 N/mm vs. 15.52 ± 0.51 N/mm respectively) and the interfragmentary relative displacements were higher for the 2-screw constructs (11.17 ± 0.88%) than for the 3-screw constructs (8.00 ± 0.45%). The difference between the number of cycles to failure for the 3-screw constructs (162,448 ± 30,073 cycles) and the 2-screw constructs (143,786 ± 10,103 cycles) was not significant. Failure in all constructs was due to plate fracture at the level of the compression holes. Clinical Significance Omission of the third innermost locking screw during bridging osteosynthesis subjected to bending forces led to a 20% reduction in construct stiffness and increased relative displacement (+39.6%) but did not change fatigue life.

scholarly journals The effect of the combination of locking screws and non-locking screws on the torsional properties of a locking-plate construct

2010 ◽  
Vol 23 (01) ◽  
pp. 7-13 ◽  
Author(s):  
N. M. M. Moens ◽  
J. Runciman ◽  
G. Monteith ◽  
S. Gordon
Keyword(s):  
Plastic Deformation ◽  
Locking Plate ◽  
Combination Group ◽  
Clinical Value ◽  
Locking Screws ◽  
Torsional Loads ◽  
Failure Point ◽  
Locking Screw ◽  
Torsional Properties ◽  
Torque Angle

SummaryLittle is known about the torsional properties of bone-plate constructs when a combination of locking and non-locking screws have been used. Sixty cadaveric canine femurs were divided into three groups. In the first group, the plate was affixed using three non-locking screws. In the second group, only locking screws were used while a combination of one locking and two non-locking screws were used in the third group. All constructs were subjected to torsion until failure. Torque, angle of torsion, and work were all calculated at the maximum failure point, as well as at five degrees of plastic deformation, which was thought to be more representative of clinical failure. At the maximum failure point, the locking group had significantly higher torque, angle, and work values than the non-locking group. The combination group was intermediate to the two other groups, and significantly differed from the non-locking group in torque, and from the locking group in work. At five degrees of plastic deformation, the locking group required significantly higher torque and work than the non-locking group. The combination group required a significantly higher torque than the non-locking group. This study suggests that a construct composed of all locking screws will fail at a greater torque value, and sustain greater work to failure in torsion compared to a construct composed of all non-locking screws. The addition of a single locking screw to an otherwise non-locking construct will increase the torque at the offset failure point and may be of clinical value in constructs subjected to high torsional loads.

scholarly journals Thermoplastic Starch (TPS) Films Added with Mucilage from Opuntia Ficus Indica: Mechanical, Microstructural and Thermal Characterization

Materials ◽  
2020 ◽  
Vol 13 (4) ◽  
pp. 1000 ◽  
Author(s):  
Fabrizio Scognamiglio ◽  
Daniele Mirabile Gattia ◽  
Graziella Roselli ◽  
Franca Persia ◽  
Ugo De Angelis ◽  
...  
Keyword(s):  
Mechanical Performance ◽  
Potato Starch ◽  
Thermal Characterization ◽  
Thermoplastic Starch ◽  
Vegetable Waste ◽  
Scanning Calorimetry ◽  
Plasticization Effect ◽  
Magnesium Salts ◽  
The One ◽  
Loading Modes

Opuntia cladodes are a typical vegetable waste, from which mucilage in gel form can be extracted. This work proposes blending it with a self-produced thermoplastic starch (TPS), originating from potato starch with a high content in glycerol (ca. 30%). Three methods were compared for extraction, bare maceration (MA), mechanical blending (ME) and mechanical blending following maceration (MPM) to produce films with an approximate thickness of 150 μm. For the comparison, tensile testing, differential scanning calorimetry and scanning electron microscopy were used. The MPM process proved the most effective, not only for extraction yielding, but also to obtain a larger deformation of the samples with respect to the one allowed by the pure TPS films. A considerable plasticization effect was observed. Despite this, the mechanical performance is still not completely satisfactory, and the expected effect of the calcium and magnesium salts contained in the mucilage to improve the rigidity of the TPS film was not really revealed. Prospected improvements would concern the fabrication process and the investigation of other possible loading modes and sample geometries.

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