@article{BaroudWuBohneretal.2003,
  author    = {Baroud, G. and Wu, J.Z. and Bohner, M and Sponagel, Stefan and Steffen, T.},
  title     = {How to determine the permeability for cement infiltration into osteoporotic cancellous bone},
  series = {Medical Engineering \& Physics. 25 (2003), H. 4},
  journal   = {Medical Engineering \& Physics. 25 (2003), H. 4},
  issn      = {1350-4533},
  pages     = {283 -- 288},
  year      = {2003},
  abstract  = {Cement augmentation is an emerging surgical procedure in which bone cement is used to infiltrate and reinforce osteoporotic vertebrae. Although this infiltration procedure has been widely applied, it is performed empirically and little is known about the flow characteristics of cement during the injection process. We present a theoretical and experimental approach to investigate the intertrabecular bone permeability during the infiltration procedure. The cement permeability was considered to be dependent on time, bone porosity, and cement viscosity in our analysis. In order to determine the time-dependent permeability, ten cancellous bone cores were harvested from osteoporotic vertebrae, infiltrated with acrylic cement at a constant flow rate, and the pressure drop across the cores during the infiltration was measured. The viscosity dependence of the permeability was determined based on published experimental data. The theoretical model for the permeability as a function of bone porosity and time was then fit to the testing data. Our findings suggest that the intertrabecular bone permeability depends strongly on time. For instance, the initial permeability (60.89 mm4/N.s) reduced to approximately 63\% of its original value within 18 seconds. This study is the first to analyze cement flow through osteoporotic bone. The theoretical and experimental models provided in this paper are generic. Thus, they can be used to systematically study and optimize the infiltration process for clinical practice.},
  subject      = {Osteoporose},
  language  = {en}
}
@article{KuehnHaugnerStaatetal.2004,
  author    = {K{\"u}hn, Raoul-Roman and Haugner, Werner and Staat, Manfred and Sponagel, Stefan},
  title     = {A Two Phase Mixture Model based on Bone Observation},
  year      = {2004},
  abstract  = {An optimization method is developed to describe the mechanical behaviour of the human cancellous bone. The method is based on a mixture theory. A careful observation of the behaviour of the bone material leads to the hypothesis that the bone density is controlled by the principal stress trajectories (Wolff's law). The basic idea of the developed method is the coupling of a scalar value via an eigenvalue problem to the principal stress trajectories. On the one hand this theory will permit a prediction of the reaction of the biological bone structure after the implantation of a prosthesis, on the other hand it may be useful in engineering optimization problems. An analytical example shows its efficiency.},
  subject      = {Knochen},
  language  = {en}
}