**5. Concluding remarks**

194 Polyurethane

0 0.2 0.4 0.6 0.8 1 1.2 1.4

*fracture stability* 

0

0.2

0.4

0.6

0.8

1

1.2

1.4

**Figure 19.** Comparison between FE prediction and experimental measurement

horizontal vertical lateral

Screw fixation FE prediction

Plate fixation Optimized FE prediction

**Figure 20.** Comparison between plate fixation and optimized screw fixation predicted from FE model

horizontal vertical lateral

*4.3.5. Feasibility of the use of synthetic PU-foam based bone in validating FE predictions of* 

We have developed a new and efficient way of simulating interfragmentary movement in acetabular fractures using a FE model. We validated our method with a biomechanical experiment involving PU-foam based synthetic bones. There are numerous studies that employed PU-foam based synthetic bones in measuring fracture stability as discussed in Section 3. However this data has not been used in validating FE model predictions of fracture stability. The use of FE models in fracture analysis is not new. However, the major focus has been to analyze the stress distribution on the implant or the overall stiffness of bone/implant composite after fracture fixation (Eberle et al., 2009, Stoffel et al., 2003). In this chapter we discussed the use of polyurethane in orthopaedic biomechanical experiments. Due to the similarity of polyurethane foam with cancellous bone in terms of microstructure and material properties, polyurethane has found a unique and important position in orthopaedic biomechanics studies. The main use of PU-foams was in experimental studies to find optimum values in various surgical procedures and to test stability of fracture or joint replacement implants. Due to the uniformity and consistency in material properties, PU-foam based synthetic bones are capable of generating reproducible results that are so difficult to obtain when using human cadaver bones. Therefore we used PU-foam materials in designing bone graft harvesters and obtaining validation data for FE model predictions in fracture load and stability. Although material properties of PU-foams are not identical to natural bone, they are able to generate comparable results that can provide important insight into surgical procedures or function of implants or devices. Moreover thanks to the advent of new composite bones made up of PU-foams and other relevant materials that mimic the geometry, structure and material properties of human

bone, only the imagination of biomechanical engineers is the limit in ways that PU-foam based materials can be used in orthopaedic biomechanical studies in the future.

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### **Author details**

V. Shim and I. Anderson *Auckland Bioengineering Institute, University of Auckland, New Zealand* 

J. Boheme and C. Josten *University of Leipzig, Germany* 
