## 4 Discussion  
### Computational Models  
Out of the 3 proposed models and the standard FEA method used each method provided a suitable method of comparison between configurations. Each method provided a set of advantages which would specifically benefit different conditions.  
The pin bending model provided a better understanding of the system identifying points through which slippage may occur. However, this behavior was not seen when 2 pins were fixed on the same bone segment as restrictions to slippage are created through geometric restriction. The proposed model is not able to identify this affect. Therefore, the assumptions made based on the interface test and the pin bending test did not hold in the system tests, creating a different shape in the test result graph and the pin bending model graph. Nevertheless the method was able to amplify the differences in the configurations increasing comparability.  
Overall, the spring model provides a more robust solution that will be easy to implement in the clinical setting. The issues with the accuracy could be accounted to measurement errors and material properties used. In addition, assumptions made for simplification also play a part in the accuracy of the result. This method could provide an advantage when comparing complex constructs as extending would be easier, but would also not be able to distinguish between constructs with similar components but have different planes of loading.  
The simplified FEA model reduced the computational cost greatly when compared to the comprehensive FEA model, but still did require more computation time than the previous 2 models. Accuracy was much higher, and would provide a better solution for complex geometries and other types of fixators. This also showed higher accuracy than a geometric specific FEA model. This could be mainly due to the mesh properties being optimized for the simplified model and those properties being used for the other model as well. This was done to create similar conditions to compare computational time, which showed the simplified model with a lower time.  
Out of the proposed models all 3 have potential for use with the simplified FEA model being extended to complex configurations. A comparison of the different models used in this study is shown in Table 4.  
Figure 21: Predictive models versus test results. Spring Model (*-), Simplified FEA (- ), Pin Bending Model (-), FEA (*-) and Test Results (**). Configuration 1—Magenta, Configuration 2—Red, Configuration 3—Blue, Configuration 4—Green, Configuration 5—Cyan, Configuration 6—Black.  
Even though the study was focused towards modeling and simulating the dynamic load of a specific fixator, the procedure followed by [PERSON] et al. is similar to what has been followed in this study, which showcases how the study could be extended into definitive fixation with dynamic loading [49]. The differences in spring models in both studies are based on whether the callus loading is considered or not. In a definitive fixation, the fixator system undergoes loading, whereas in a temporal system focus is given to ensure system stiffness assuming there will not be any weight bearing happening through the fracture site.  
[PERSON] et al. suggested a different approach of comparing fixator configurations where they simplify the model into a 1D finite element model for the fixator and bone system. the authors demonstrate that the 1D approximation of a uni-planar-unilateral fixator is suitable for configuration optimization [22]. A similar model was not used in this study due to limitations in extending towards multi-planar configurations.