Derivation of inter-lamellar behaviour of the intervertebral disc annulus

Mengoni, Marlène; Luxmoore, Bethany Jane; Wijayathunga, Vithanage N.; Jones, Alison C.; Broom, Neil D.; Wilcox, Ruth K.

doi:10.1016/j.jmbbm.2015.03.028

Cited by 41 publications

(39 citation statements)

References 41 publications

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“…This is due to two phenomena: the lamellae getting closer or further away from each other due to the changes in their fibre alignment, and the fibre bundles being pulled apart or closer to each other. Previous work by Mengoni et al [34] reported an inter-lamella stiffness higher than intra-lamella. Those authors, however, applied a very specific loading to a thin radial slice of annulus whereas in this case the composite-like structure of the annulus was not compromised.…”

Section: Discussionmentioning

confidence: 80%

Lamellar and fibre bundle mechanics of the annulus fibrosus in bovine intervertebral disc

et al. 2016

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Section: Discussionmentioning

confidence: 80%

Lamellar and fibre bundle mechanics of the annulus fibrosus in bovine intervertebral disc

et al. 2016

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“…Some of the experiments that have been used that indirectly assessed the ILM are radial tensile tests of intact tissue and with enzymatic digestion or cross‐linking, shear testing, NP pressurization of the intact disc, and peel testing . One recent study, however, has directly assessed ILM mechanical properties . In this study, the stiffness of the ILM under radial loading was consistently higher than the corresponding lamellar values, and was measured to be greater at the outer (43–75% higher) relative to the inner AF.…”

Section: Inter‐lamellar Matrix Micromechanical Propertiesmentioning

confidence: 76%

“…Complexity of the elastic fibers in the ILM including their thickness and coil‐like structures with high degree of elastin–fibrillin co‐localization have been suggested to play a mechanical role; however, their impact on AF mechanical properties and integrity is unknown. Therefore, using lamellae that were concentric and physically isolated when developing computational models of the AF, may not be an appropriate representation …”

Section: Inter‐lamellar Matrix Microstructurementioning

confidence: 99%

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Structure and mechanical function of the inter‐lamellar matrix of the annulus fibrosus in the disc

Tavakoli

Elliott

Costi

2016

Journal Orthopaedic Research

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The inter-lamellar matrix (ILM) has an average thickness of less than 30 mm and lies between adjacent lamellae in the annulus fibrosus (AF). The microstructure and composition of the ILM have been studied in various anatomic regions of the disc; however, their contribution to AF mechanical properties and structural integrity is unknown. It was suggested that the ILM components, mainly elastic fibers and cross-bridges, play a role in providing mechanical integrity of the AF. Therefore, the manner in which they respond to different loadings and stabilize adjacent lamellae structure will influence AF tear formation and subsequent herniation. This review paper summarizes the composition, microstructure, and potential role of the ILM in the progression of disc herniation, clarifies the micromechanical properties of the ILM, and proposes critical areas for future studies. There are a number of unknown characteristics of the ILM, such as its mechanical role, impact on AF integrity, and ultrastructure of elastic fibers at the ILM-lamella boundary. Determining these characteristics will provide important information for tissue engineering, repair strategies, and the development of more-physiological computational models to study the initiation and propagation of AF tears that lead to herniation and degeneration. Keywords: inter-lamellar matrix; cross-bridges; annulus fibrosus; elastic fibersThe inter-lamellar matrix (ILM) lies between the lamellae of the annulus fibrosus (AF) of the intervertebral disc and has a thickness of less than 30 mm. The ILM is comprised of four main components: Matrix, cross-bridges, elastic fibers, and cells; however, those components are not restricted to the ILM alone (i.e., cross-bridges are present in the ILM space and cross radially through multiple AF layers). 1-5 ILM failure results in delamination (separation of lamellae) and may be one of the initial stages of herniation and degeneration. 6-8 Knowledge of the ILM structure and mechanical function is important to determining the loading conditions under which the AF is at risk of delamination and subsequent disc disruption and herniation. This understanding of the ILM may lead to the development of improved clinical strategies for disc treatment of herniation and painful degenerative disc disorders.AF delamination and tears, and the associated disc degeneration, are directly related to the structural integrity of the ILM. 9-12 Migration of the NP propagates-under certain circumstances-circumferentially, increasing ILM localized stress and risk of delamination in deep (i.e., inner) AF layers. 8 ILM failure and associated delamination alters ovine spine segment mechanics and causes increased lamellar thickness and vertebral bone volume fraction. 7 On the other hand, delamination may also lead to increased tensile loading within the collagenous AF lamellae components. Therefore, the role of the ILM on the AF microstructural integrity 13 and strength is evident, as mechanical properties of multi-lamellae are different from single ...

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“…The initial stiffness values of the lamellar and inter-lamellar springs,

k_{l, 0}

and

k_{italicil, 0}

, were derived from an elastic model (Mengoni et al, 2015). The damaged springs were modelled in line with the continuum damage mechanics theory (Lemaitre and Desmorat, 2005).…”

Section: Methodsmentioning

confidence: 99%

Modelling the failure precursor mechanism of lamellar fibrous tissues, example of the annulus fibrosus

Mengoni

Jones

Wilcox

2016

Journal of the Mechanical Behavior of Biomedical Materials

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The aims of this study were to assess the damage and failure strengths of lamellar fibrous tissues, such as the anterior annulus fibrosus (AF), and to develop a mathematical model of damage propagation of the lamellae and inter-lamellar connections. This level of modelling is needed to accurately predict the effect of damage and failure induced by trauma or clinical interventions. 26 ovine anterior AF cuboid specimens from 11 lumbar intervertebral discs were tested in radial tension and mechanical parameters defining damage and failure were extracted from the in-vitro data. Equivalent 1D analytical models were developed to represent the specimen strength and the damage propagation, accounting for the specimen dimensions and number of lamellae. Model parameters were calibrated on the in-vitro data. Similar to stiffness values reported for other orientations, the outer annulus was found stronger than the inner annulus in the radial direction, with failure at higher stress values. The inner annulus failed more progressively, showing macroscopic failure at a higher strain value. The 1D analytical model of damage showed that lamellar damage is predominant in the failure mechanism of the AF. The analytical model of the connections between lamellae allowed us to represent separately damage processes in the lamellae and the inter-lamellar connections, which cannot be experimentally tested individually.

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Derivation of inter-lamellar behaviour of the intervertebral disc annulus

Cited by 41 publications

References 41 publications

Lamellar and fibre bundle mechanics of the annulus fibrosus in bovine intervertebral disc

Lamellar and fibre bundle mechanics of the annulus fibrosus in bovine intervertebral disc

Structure and mechanical function of the inter‐lamellar matrix of the annulus fibrosus in the disc

Modelling the failure precursor mechanism of lamellar fibrous tissues, example of the annulus fibrosus

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