Biological Media
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X-ray computed tomography of porcine patellar tendon.
Soft tissues
The usual definition of soft tissues is that they are the materials that connect, support, or surround other structures and organs of the body, Soft tissues are complex inhomogeneous materials, the constitutive behaviour of which is still relatively poorly understood. Soft tissues include skin, tendon, ligament, brain and arteries but not bone which is classed as a hard tissue (see below).
Of particular interest to the group is the modelling of ligaments and tendons, which are fundamental structures in the musculoskeletal systems of vertebrates. Ligaments connect bone to bone to provide stability and allow joints to function correctly, whereas tendons connect bone to muscle to allow the transfer of forces generated by muscles to the skeleton. The wide variety of roles played by different ligaments and tendons requires them to have considerably different mechanical responses to applied forces, however, it is not known what causes this variety in mechanical behaviour.
Like many biological materials, ligaments and tendon have a hierachical structure varying over several length scales giving rise to complex behaviour. Our group is interested in investigating how the variation in microstructure of ligaments and tendons over multiple length scales leads to the differing stress-strain responses that have been observed in different ligaments and tendons. We take a multidisciplinary approach, using state-of-the-art imaging technology such as X-ray computed tomography to inform the mathematical modelling. In particular we are interested in developing models incorporating parameters that can realistically be measured experimentally. We have developed new strain energy functions that appear to be well-suited to modelling the quasi-static response of a variety of soft tissues and viscoelastic models of their time-dependent behaviour.
The usual definition of soft tissues is that they are the materials that connect, support, or surround other structures and organs of the body, Soft tissues are complex inhomogeneous materials, the constitutive behaviour of which is still relatively poorly understood. Soft tissues include skin, tendon, ligament, brain and arteries but not bone which is classed as a hard tissue (see below).
Of particular interest to the group is the modelling of ligaments and tendons, which are fundamental structures in the musculoskeletal systems of vertebrates. Ligaments connect bone to bone to provide stability and allow joints to function correctly, whereas tendons connect bone to muscle to allow the transfer of forces generated by muscles to the skeleton. The wide variety of roles played by different ligaments and tendons requires them to have considerably different mechanical responses to applied forces, however, it is not known what causes this variety in mechanical behaviour.
Like many biological materials, ligaments and tendon have a hierachical structure varying over several length scales giving rise to complex behaviour. Our group is interested in investigating how the variation in microstructure of ligaments and tendons over multiple length scales leads to the differing stress-strain responses that have been observed in different ligaments and tendons. We take a multidisciplinary approach, using state-of-the-art imaging technology such as X-ray computed tomography to inform the mathematical modelling. In particular we are interested in developing models incorporating parameters that can realistically be measured experimentally. We have developed new strain energy functions that appear to be well-suited to modelling the quasi-static response of a variety of soft tissues and viscoelastic models of their time-dependent behaviour.
- Chang, J. Garva, R., Pickard, A., Yeung, C.-Y.C., Mallikarjun, V., Swift, J., Holmes, D.F., Calverley, B., Lu, Y., Adamson, A., Raymond-Hayling, H., Jensen, O., Shearer, T., Meng, Q.J. and Kadler, K.E. 2020 "Circadian control of the secretory pathway maintains collagen homeostasis". Nature Cell Biology, 22, 74-86. (doi: 10.1038/s41556-019-0441-z)
- Rawson, S.D., Shearer, T., Lowe, T., O'Brien, M., Wong, J.F.K., Margetts, L. and Cartmell, S.H. 2018 "Four-dimensional imaging of soft tissue and implanted biomaterial mechanics: A barbed suture case study for tendon repair". Appl. Mat. Interfaces 10, 38681-38691 (doi: 10.1021/acsami.8b09700).
- Craddock, R.J., Hodson, N.W., Ozols, N., Shearer, T., Hoyland, J.A. and Sherratt, M.J. 2018 "Extracellular matrix fragmentation in young, healthy cartilaginous tissues". Eur. Cell Mater. 35, 34-53 (doi: 10.22203/eCM.v35a04).
- Shearer, T., Thorpe, C.T. and Screen H.R.C. 2017 "The relative compliance of energy-storing tendons may be due to the helical fibril arrangement of their fascicles". J. R. Soc. Interface 14, 2017026. (doi: 10.1098/rsif.2017.0261)
- Shearer, T., Bradley, R.S., Hidalgo-Bastida, A., Sherratt, M.J. and Cartmell, S.H. 2016 "Three-dimensional visualisation of soft biological structures by X-ray computed micro-tomography". J. Cell Sci. 129, 2483-2492. (doi: 10.1242/jcs.179077)
- Balint, R., Lowe, T. and Shearer, T. 2016 "Optimal contrast agent staining of ligaments and tendons for X-ray computed tomography". PLoS ONE 11, e0153552. (doi: 10.1371/journal.pone.0153552)
- Shearer, T. 2015 “A new strain energy function for modelling ligaments and tendons whose fascicles have a helical arrangement of fibrils”. J. Biomech. 48, 3017-3025. (doi: 10.1016/j.jbiomech.2015.07.032)
- Shearer, T. 2015 “A new strain energy function for the hyperelastic modelling of ligaments and tendons based on fascicle microstructure”. J. Biomech. 48, 290-297. (doi: 10.1016/j.jbiomech.2014.11.031)
- Gilchrist, M.D., Murphy, J.G., Parnell, W.J. and Pierrat, B. "Modelling the slight compressibility of anisotropic soft tissue", 2014 Int. J. Solids Structures 51, 3857-3865. (doi: 10.1016/j.ijsolstr.2014.06.018)
- Shearer, T., Rawson, S., Castro, S.J., Balint, R., Bradley, R.S., Lowe, T., Vila-Comamala, J., Lee, P.D. and Cartmell, S.H. 2014 "X-ray computed tomography of the anterior cruciate ligament and patellar tendon", Muscle, Ligaments and Tendons Journal 4, 238-244. (doi:10.11138/mltj/2014.4.2.238)
Bone
Like soft tissue, bone also has a complex inhomogeneous microstructure across several lengthscales. Bone is, however a hard tissue and it can be assessed effectively by wave propagation. We have been particularly active in modelling the effective behaviour of cortical bone, the dense, low porosity bone around the outer rim of the bone shaft. Wave propagation techniques can be used in an ultrasound context to predict the onset of osteoporosis, for example, and provide a less dangerous probing technique than X-ray imaging. As in the context of soft tissue we are particularly interested in developing models that can incorporate parameters that can realistically be measured experimentally.
Like soft tissue, bone also has a complex inhomogeneous microstructure across several lengthscales. Bone is, however a hard tissue and it can be assessed effectively by wave propagation. We have been particularly active in modelling the effective behaviour of cortical bone, the dense, low porosity bone around the outer rim of the bone shaft. Wave propagation techniques can be used in an ultrasound context to predict the onset of osteoporosis, for example, and provide a less dangerous probing technique than X-ray imaging. As in the context of soft tissue we are particularly interested in developing models that can incorporate parameters that can realistically be measured experimentally.
- Granke, M., Grimal, Q., Parnell, W.J., Raum, K., Gerisch, A., Peyrin, F., Saied, A. and Laugier, P.
"To what extent can cortical bone millimeter scale elasticity be predicted by a two phase composite model with variable porosity?"
Acta Biomaterialia 12, 207-215. (doi: 10.1016/j.actbio.2014.10.011) - Parnell, W.J., Vu, M.-B., Grimal, Q. and Naili, S., 2012, "Analytical methods to determine the effective mesoscopic and macrosopic elastic properties of cortical bone". J. Biomechanics and Modelling in Mechanobiology 11, 883-901. (doi:10.1007/s10237-011-0359-2)
- Grimal, Q., Rus, G., Parnell, W.J. and Laugier, P. 2011, "A two-parameter model of the effective elastic modulus tensor for cortical bone", J. Biomechanics 44, 1621-1625 (doi:10.1016/j.jbiomech.2011.03.006 )
- Parnell, W.J. and Grimal, Q., 2009, "The influence of mesoscopic porosity on cortical bone anisotropy. Investigations via asymptotic homogenization.", J. Royal Society Interface 6, 97-109 (doi:10.1098/rsif.2008.0255)
