Tie‐fibre structure and organization in the knee menisci

Andrews, Stephen H. J.; Rattner, J. B.; Abusara, Ziad; Adesida, Adetola B; Shrive, Nigel G.; Ronsky, Janet L.

doi:10.1111/joa.12170

Cited by 61 publications

(60 citation statements)

References 13 publications

(28 reference statements)

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“…Since the fiber-level microstructure of the meniscus ECM has been revealed in detail by optical microscopy [9, 10], this study focused on the fibril-level, nanoscale structure of collagen. Immediately after AFM tests, each section was fixed with Karnovsky’s fixative (Electron Microscopy Sciences, Hatfield, PA), dehydrated in a series of graded water-ethanol and ethanol-hexamethyldisilazane (HMDS) mixtures [38], and dried in air to retain the 3D collagen architecture.…”

Section: Methodsmentioning

confidence: 99%

Micromechanical anisotropy and heterogeneity of the meniscus extracellular matrix

Han

et al. 2017

Acta Biomaterialia

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To understand how the complex biomechanical functions of the meniscus are endowed by the nanostructure of its extracellular matrix (ECM), we studied the anisotropy and heterogeneity in the micromechanical properties of the meniscus ECM. We used atomic force microscopy (AFM) to quantify the time-dependent mechanical properties of juvenile bovine meniscus at deformation length scales corresponding to the diameters of collagen fibrils. At this scale, anisotropy in the elastic modulus of the circumferential fibers, the major ECM structural unit, can be attributed to differences in fibril deformation modes: uncrimping when normal to the fiber axis, and laterally constrained compression when parallel to the fiber axis. Heterogeneity among different structural units is mainly associated with their variations in microscale fiber orientation, while heterogeneity across anatomical zones is due to alterations in collagen fibril diameter and alignment at the nanoscale. Unlike the elastic modulus, the time-dependent properties are more homogeneous and isotropic throughout the ECM. These results enable a detailed understanding of the meniscus structure-mechanics at the nanoscale, and can serve as a benchmark for understanding meniscus biomechanical function, documenting disease progression and designing tissue repair strategies.

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Section: Methodsmentioning

confidence: 99%

Micromechanical anisotropy and heterogeneity of the meniscus extracellular matrix

Han

et al. 2017

Acta Biomaterialia

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“…In addition to circumferential fibers, the meniscus also contains a population of radial tie fibers (RTFs). These RTFs originate at the meniscus periphery, and interdigitate amongst the circumferential fibers [1–3,5]. Comprised of types I and II collagen [1], RTFs vary spatially in both size and in their arborization [5].…”

Section: Introductionmentioning

confidence: 99%

“…These RTFs originate at the meniscus periphery, and interdigitate amongst the circumferential fibers [1–3,5]. Comprised of types I and II collagen [1], RTFs vary spatially in both size and in their arborization [5]. Morphological characterization of RTFs, first detailed by Skaggs, et al , indicate that they are thin and numerous in the anterior region of the meniscus, and posteriorly become thicker and longer, reaching into the inner one third of the tissue [3].…”

Section: Introductionmentioning

confidence: 99%

Mechanical function near defects in an aligned nanofiber composite is preserved by inclusion of disorganized layers: Insight into meniscus structure and function

et al. 2017

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The meniscus is comprised of circumferentially aligned fibers that resist the tensile forces within the meniscus (i.e., hoop stress) that develop during loading of the knee. Although these circumferential fibers are severed by radial meniscal tears, tibial contact stresses do not increase until the tear reaches ~90% of the meniscus width, suggesting that the severed circumferential fibers still bear load and maintain the mechanical functionality of the meniscus. Recent data demonstrates that the interfibrillar matrix can transfer strain energy to disconnected fibrils in tendon fascicles. In the meniscus, interdigitating radial tie fibers, which function to stabilize and bind the circumferential fibers together, are hypothesized to function in a similar manner by transmitting load to severed circumferential fibers near a radial tear. To test this hypothesis, we developed an engineered fibrous analog of the knee meniscus using poly(ε-caprolactone) to create aligned scaffolds with variable amounts of non-aligned elements embedded within the scaffold. We show that the tensile properties of these scaffolds are a function of the ratio of aligned to non-aligned elements, and change in a predictable fashion following a simple mixture model. When measuring the loss of mechanical function in scaffolds with a radial tear, compared to intact scaffolds, the decrease in apparent linear modulus was reduced in scaffolds containing non-aligned layers compared to purely aligned scaffolds. Increased strains in areas adjacent to the defect were also noted in composite scaffolds. These findings indicate that non-aligned (disorganized) elements interspersed within an aligned network can improve overall mechanical function by promoting strain transfer to nearby disconnected fibers. This finding supports the notion that radial tie fibers may similarly promote tear tolerance in the knee meniscus, and will direct changes in clinical practice and provide guidance for tissue engineering strategies.

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“…15 In meniscus, the fibrous architecture displays a distribution of fiber orientations, where the majority of collagen fibers are aligned longitudinal to the meniscus circumference (Fig. 1), and a smaller subset of collagen fibers, called tie fibers, 16 are aligned transverse to the circumference. The circumferential collagen fibers provide the majority of the load distribution function, as these fibers resist deformation caused by the circumferential tensile stress or hoop stress generated in the semi-circular meniscus during joint compression.…”

Section: Introductionmentioning

confidence: 99%

Fatigue life of bovine meniscus under longitudinal and transverse tensile loading

Creechley

Krentz

Lujan

2017

Journal of the Mechanical Behavior of Biomedical Materials

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The knee meniscus is composed of a fibrous matrix that is subjected to large and repeated loads. Consequently, the meniscus is frequently torn, and a potential mechanism for failure is fatigue. The objective of this study was to measure the fatigue life of bovine meniscus when applying cyclic tensile loads either longitudinal or transverse to the principal fiber direction. Fatigue experiments consisted of cyclic loads to 60, 70, 80 or 90% of the predicted ultimate tensile strength until failure occurred or 20,000 cycles was reached. The fatigue data in each group was fit with a Weibull distribution to generate plots of stress level vs. cycles to failure (S-N curve). Results showed that loading transverse to the principal fiber direction gave a two-fold increase in failure strain, a three-fold increase in creep, and a nearly four-fold increase in cycles to failure (not significant), compared to loading longitudinal to the principal fiber direction. The S-N curves had strong negative correlations between the stress level and the mean cycles to failure for both loading directions, where the slope of the transverse S-N curve was 11% less than the longitudinal S-N curve (longitudinal: S=108–5.9ln(N); transverse: S=112–5.2ln(N)). Collectively, these results suggest that the non-fibrillar matrix is more resistant to fatigue failure than the collagen fibers. Results from this study are relevant to understanding the etiology of atraumatic radial and horizontal meniscal tears, and can be utilized by research groups that are working to develop meniscus implants with fatigue properties that mimic healthy tissue.

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Tie‐fibre structure and organization in the knee menisci

Cited by 61 publications

References 13 publications

Micromechanical anisotropy and heterogeneity of the meniscus extracellular matrix

Micromechanical anisotropy and heterogeneity of the meniscus extracellular matrix

Mechanical function near defects in an aligned nanofiber composite is preserved by inclusion of disorganized layers: Insight into meniscus structure and function

Fatigue life of bovine meniscus under longitudinal and transverse tensile loading

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