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ARUP; ISBN: 978-0-9562121-5-3 - CMBBE 2012 - Cardiff University

ARUP; ISBN: 978-0-9562121-5-3 - CMBBE 2012 - Cardiff University

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attributed to the change of stiffness of the augmented vertebra core. Due to this, a load<br />

shift may occur which increases the risk of fractures in the adjacent vertebra [4].<br />

Fig. 4: Vertical displacement of the upper cortical shell: untreated (left) und treated by<br />

vertebroplasty (right) - (deformed shape plot is up-scaled)<br />

6. CONCLUDING REMARKS<br />

We have introduced a material model that is able to capture thermal and mechanical<br />

characteristics of acrylic bone cements during the chemical process of polymerization as<br />

well as in the solid state of the material. The parameters of the material model have<br />

been identified with respect to one specific acrylic bone cement and the model has been<br />

implemented into a commercial finite element code.<br />

By the help of our developed tools, a unified approach of analyses of processes in<br />

vertebroplasty is enabled. The capability of this approach has been demonstrated using a<br />

representative parametric model of a lumbar vertebral body. The process of exothermal<br />

curing and a subsequent mechanical loading have been examined and typical<br />

characteristics have been reproduced. The presented approach will be used as a basis for<br />

further investigations. This includes the study of different process procedures in<br />

vertebroplasty and their thermal and mechanical impact on the biomechanics of the<br />

spine.<br />

7. REFERENCES<br />

1. Kolmeder, S., Lion, A., Landgraf, R., Ihlemann, J., Thermophysical properties and<br />

material modelling of acrylic bone cements used in vertebroplasty, J Therm Anal<br />

Calorim, 2011, Vol. 105, 705-718<br />

2. Štern D., Likar, B., Pernuš, F. and Vrtovec, T., Parametric modelling and<br />

segmentation of vertebral bodies in 3D CT and MR spine images, Phys. Med. Biol.,<br />

2011, Vol. 56, 7505-7522<br />

3. Zhou, S.H., McGarthy, I.D., McGregor, A.H., Coombs, R.R.H., Hughes, S.P.F.,<br />

Geometrical dimensions of the lower lumbar vertebrae - analysis of data from<br />

digitised CT images, Eur Spine J, 2000, Vol. 9, 242-248<br />

4. Rohlmann, R., Boustani, H.N., Bergmann, G., Zander, T., A probabilistic finite<br />

element analysis of the stresses in the augmented vertebral body after<br />

vertebroplasty, Eur Spine J, 2010, Vol. 19, 1585-1595<br />

5. Stańczyk, M., Study on modeling of PMMA bone cement polymerization, J<br />

Biomech, 2005, Vol. 38, 1397-1403<br />

ACKNOWLEDGEMENTS: The research is funded by the German Research<br />

Foundation (DFG) within the project PAK 273.

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