Bauer Sabine

than the ventrally located structures. A further example in the field of medicine is studying

It is clearly pointed out that modeling has to be understood as an approximation to the reality. In near future, it will probably not be possible that all influencing factors can be simulated completely as in reality. Often, input parameters based on literature data representing the average of a specific cohort. Because each person has a very specific anthropometric and morphological characteristic, the standard deviations of such investigations may be relatively large. For example, the standard deviation for geometric parameters that describe the sagittal alignment of the spine is partially enormous. The deviation from average of the pelvic incidence is partly more than 20% [31], of the pelvic tilt 53% [32] respectively 70% [33], and of the total lumbosacral lordosis 19% [34], etc. But based on sensitivity analysis, the exact influence of individual parameters can be determined. However, because of the complexity of the models, it is very important to know the exact configuration of the model and the limita‐ tions of its input parameters. Therefore, the modeling and the validation process should to be

Opportunities for improvement and expansion of the different model components will be

In the presented models, the biomechanics of the intervertebral disc is defined by a force law, which can be understood as an initial approach. To precise the biomechanical properties of the annulus fibrosis and nucleus pulposus, a 3D hybrid model consisting of MBS and FE units will be built. The aim is to analyze whether the implementation of FE-disc features contributes to a significant gain of knowledge concerning load distribution of the intervertebral discs and

Currently, a highly accurate modeled individual cartilaginous contact layer for all facet joints is in development. These individually formed layers of cartilage (**Figure 17**) allow us to do a

the effects of different body weights on selected surgical procedures.

44 Numerical Simulation - From Brain Imaging to Turbulent Flows

**5. Meaningfulness and limitation of MBS modeling**

understood as an evolving process and will be advanced in future research.

summarized in the following:

the adjacent spinal structures.

3D calculation of the resulting forces.

**Figure 17.** Facet joints with a 3D layer of cartilage.

Address all correspondence to: bauer@uni-koblenz.de

MTI Mittelrhein, Institute for Medical Engineering and Information Processing, University Koblenz-Landau, Campus Koblenz, Germany
