The role of geosynthetics in reducing the fluidisation potential of soft subgrade under cyclic loading

Objectives The paradoxical migration of the femoral neck element (FNE) superomedially against gravity, with respect to the intramedullary component of the cephalomedullary device, is a poorly understood phenomenon increasingly seen in the management of pertrochanteric hip fractures with the intramedullary nail. The aim of this study was to investigate the role of bidirectional loading on the medial migration phenomenon, based on unique wear patterns seen on scanning electron microscopy of retrieved implants suggestive of FNE toggling. Methods A total of 18 synthetic femurs (Sawbones, Vashon Island, Washington) with comminuted pertrochanteric fractures were divided into three groups (n = 6 per group). Fracture fixation was performed using the Proximal Femoral Nail Antirotation (PFNA) implant (Synthes, Oberdorf, Switzerland; n = 6). Group 1 was subjected to unidirectional compression loading (600 N), with an elastomer (70A durometer) replacing loose fracture fragments to simulate surrounding soft-tissue tensioning. Group 2 was subjected to bidirectional loading (600 N compression loading, 120 N tensile loading), also with the elastomer replacing loose fracture fragments. Group 3 was subjected to bidirectional loading (600 N compression loading, 120 N tensile loading) without the elastomer. All constructs were tested at 2 Hz for 5000 cycles or until cut-out occurred. The medial migration distance (MMD) was recorded at the end of the testing cycles. Results The MMDs for Groups 1, 2, and 3 were 1.02 mm, 6.27 mm, and 5.44 mm respectively, with reliable reproduction of medial migration seen in all groups. Bidirectional loading groups showed significantly higher MMDs compared with the unidirectional loading group (p < 0.01). Conclusion Our results demonstrate significant contributions of bidirectional cyclic loading to the medial migration phenomenon in cephalomedullary nail fixation of pertrochanteric hip fractures. Cite this article: G. W. Law, Y. R. Wong, A. K-S. Yew, A. C. T. Choh, J. S. B. Koh, T. S. Howe. Medial migration in cephalomedullary nail fixation of pertrochanteric hip fractures: A biomechanical analysis using a novel bidirectional cyclic loading model. Bone Joint Res 2019;8:313–322. DOI: 10.1302/2046-3758.87.BJR-2018-0271.R1.

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The Role of Agarose Mechanical Response on the Matrix Synthesis of Nucleus Pulposus Cells: A Pilot Study

ASME 2009 Summer Bioengineering Conference, Parts A and B ◽

10.1115/sbc2009-206763 ◽

2009 ◽

Cited By ~ 1

Author(s):

Arzu Tasci ◽

Ladina Ettinger ◽

Stephen Ferguson ◽

Philippe Büchler

Keyword(s):

Cyclic Loading ◽

Mechanical Response ◽

Low Back ◽

Limited Capacity ◽

Nucleus Pulposus Cells ◽

Matrix Synthesis ◽

Biosynthetic Activity ◽

The Matrix ◽

Ivd Degeneration

Low back pain is the most common spinal disorder and its main cause is intervertebral disc (IVD) degeneration. IVD has a major role of withstanding loads generated in the spine during daily activities. However, it has a limited capacity for self-repair. Since it has an avascular structure, the pathways it uses for regeneration is quite complex and not yet well understood. The mechanical stimulation studies on the cell seeded constructs revealed that cells regulate their biosynthetic activity with cyclic loading [1,2]. The mechanical properties of the scaffold might play an important role in the transmission of mechanical signals to the embedded cells. The objective of this study is to investigate the effect of agarose concentration on the amount of extracellular matrix synthesis in IVD cell seeded constructs under static culture and cyclic loading conditions.

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Disc Mechanics With Trans-Endplate Partial Nucleotomy are not Fully Restored Following Cyclic Compressive Loading and Unloaded Recovery

Journal of Biomechanical Engineering ◽

10.1115/1.2354210 ◽

2006 ◽

Vol 128 (6) ◽

pp. 823-829 ◽

Cited By ~ 15

Author(s):

Edward J. Vresilovic ◽

Wade Johannessen ◽

Dawn M. Elliott

Keyword(s):

Cyclic Loading ◽

Stress Relaxation ◽

Nucleus Pulposus ◽

Time Constant ◽

Annulus Fibrosus ◽

Compressive Loading ◽

Magnetic Resonance Images ◽

Mechanical Behaviors ◽

Short Time

Mechanical function of the intervertebral disc is maintained through the interaction between the hydrated nucleus pulposus, the surrounding annulus fibrosus, and the superior and inferior endplates. In disc degeneration the normal transfer of load between disc substructures is compromised. The objective of this study was to explore the mechanical role of the nucleus pulposus in support of axial compressive loads over time. This was achieved by measuring the elastic slow ramp and viscoelastic stress-relaxation mechanical behaviors of cadaveric sheep motion segments before and after partial nucleotomy through the endplate (keeping the annulus fibrosus intact). Mechanics were evaluated at five conditions: Intact, intact after 10,000cycles of compression, acutely after nucleotomy, following nucleotomy and 10,000cycles of compression, and following unloaded recovery. Radiographs and magnetic resonance images were obtained to examine structure. Only the short time constant of the stress relaxation was altered due to nucleotomy. In contrast, cyclic loading resulted in significant and large changes to both the stiffness and stress relaxation behaviors. Moreover, the nucleotomy had little to no effect on the disc mechanics after cyclic loading, as there were no significant differences comparing mechanics after cyclic loading with or without the nucleotomy. Following unloaded recovery the mechanical changes that had occurred as a consequence of cyclic loading were restored, leaving only a sustained change in the short time constant due to the trans-endplate nucleotomy. Thus the swelling and redistribution of the remaining nucleus pulposus was not able to fully restore mechanical behaviors. This study reveals insights into the role of the nucleus pulposus in disc function, and provides new information toward the potential role of altered nucleus pulpous function in the degenerative cascade.

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Experimental study to examine the role of under sleeper pads for improved performance of ballast under cyclic loading

Transportation Geotechnics ◽

10.1016/j.trgeo.2019.01.005 ◽

2019 ◽

Vol 19 ◽

pp. 61-73 ◽

Cited By ~ 17

Author(s):

Chamindi Jayasuriya ◽

Buddhima Indraratna ◽

Trung Ngoc Ngo

Keyword(s):

Experimental Study ◽

Cyclic Loading ◽

Improved Performance

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A Critical Review on the Performance of Pile-Supported Rail Embankments under Cyclic Loading: Numerical Modeling Approach

Sustainability ◽

10.3390/su13052509 ◽

2021 ◽

Vol 13 (5) ◽

pp. 2509

Author(s):

A. S. M. Riyad ◽

Fernanda Bessa Ferreira ◽

Buddhima Indraratna ◽

Trung Ngo

Keyword(s):

Numerical Modeling ◽

Cyclic Loading ◽

Numerical Methods ◽

Environmentally Sustainable ◽

Subgrade Soils ◽

Future Design ◽

Deformation Response ◽

Key Issues ◽

Experimental Approaches ◽

Soft Subgrade

Searching for economical and practical solutions to increase any transport substructure’s protection and stability is critical for ensuring the long-term viability and adequate load-bearing capacity. Piles are increasingly being used as an economical and environmentally sustainable solution to enhance the strength of soft subgrade soils on which embankments are raised. As per the available literature, there are two main strategies used to explain railway embankments’ performance: experimental approaches and numerical simulations on a broad scale. The purpose of this study is to examine the state-of-the-art literature on numerical modeling methods adopted to assess the performance of pile-supported rail embankments subjected to cyclic loading. The paper addresses the main results from various numerical methods to explain the appropriate mechanisms associated with the load deformation response. It also presents the key issues and drawbacks of these numerical methods concerning rail embankment development while outlining the specific shortcomings and research gaps relevant to enhanced future design and analysis.

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Mechanical behaviour of alginate film with embedded voids under compression-decompression cycles

Scientific Reports ◽

10.1038/s41598-019-49589-w ◽

2019 ◽

Vol 9 (1) ◽

Cited By ~ 1

Author(s):

Arindam Banerjee ◽

Somenath Ganguly

Keyword(s):

Cyclic Loading ◽

Mechanical Behaviour ◽

Time Scale ◽

Balance Equations ◽

Gel Structure ◽

Gel Film ◽

Fluidic Device ◽

Cell Colonization ◽

Stress Hysteresis

Abstract Voids of 300 µm diameter were embedded uniformly as monolayer in alginate gel film using a fluidic device. Voids of these dimensions in biopolymer gel film are desired for better transport of bioactive species and cell colonization in engineered tissues. In this article, the role of embedded voids in reducing compressive stress, hysteresis, and time scale of reheal vis-a-vis expulsion of pore fluid and its reabsorption upon reversal of load are reviewed. The cyclic loading was conducted with varying amplitude and frequency. The irreversible changes, if any in the gel structure under extreme compression were analyzed. The rate of expulsion of aqueous phase directly relates to the permeability of the gel film that is estimated here using simplified momentum and volumetric balance equations. The decrease in permeability with deformation is analyzed further, and the contribution of voids in this regard is discussed.

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