## 4 Discussion
### Workflow for Surgical Assistance  
The objective of the study was to present a model for external fixator configuration optimization and test its feasibility. The pilot study, even though limited in its scope provided valuable information on the proposed method. As the focus was on creating a low-cost solution suitable for developing regions, external fixators were considered. Linear fixators are generally used for temporary fixation to stabilize the fracture site during initial surgical care and for simple fractures. For complex fractures and fractures with significant bone loss, circular external fixation is considered a better option than a linear fixator [24]. Fracture categorization was used to reduce cost of computation where possible. Simple fractures (e.g., diaphyseal transverse fractures) would not require extensive analysis and would also be fixable using simple fixation techniques. The framework was broken down into several steps in order to create a methodology to add external fixator information. Initially, a testing protocol was developed to identify mechanical properties of the fixator, while limiting the complexity and volume of testing. Two tests were developed to understand the main components with varying geometry and properties when comparing different fixator types. The main drawback of the developed procedure is that separate rigs were needed to be fabricated to complete testing. This issue was mitigated to a certain extent by using low cost material and simple machining techniques. Testing for standard parts like the shaft were not conducted, to reduce the number of tests. Pin testing was conducted as modeling the clamp system required understanding pin behavior. For system development pin length variation was not done: objective was to reduce the number of steps used in the testing process to ease implementation. The 2 tests were thought to be sufficient per pin and clamp type. Simplifying testing also provided a fair share of drawbacks when modeling the system as the test results had a larger range of deviation. Multiple tests were carried out to reduce the deviation. Improving testing accuracy for tests like the system test will be required when modeling complex systems. The test results on the low cost MK02 fixator provided valuable input on the fixator behavior. Interface tests displayed slippage during testing, which is a result of the design including 2 clamps for each pin clamp assembly, kept in place with one fixture. The results showed significant improvement of stability when tightening torque was increased. When \begin{table}
\begin{tabular}{c c c c c} \hline \hline \multirow{2}{*}{**Method**} & **Computational Cost and Computation Time** & **Development Complexity** & \multirow{2}{*}{**Accuracy**} & **Simplicity in Being Extended to Other Fixator Forms** \\ \hline Pin bending model & Low & High & Low & Complex \\ Spring model & Low & Medium & Medium & Simple \\ Simplified FEA Model & Medium & Medium & High & Complex \\ FEA Model & High & Low & High & Medium \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Model comparison. complimented by more pins in an assembly, the fixator showed very good performance comparable with other commercially available systems. It should be noted that for a fixator of this type, tightening torque plays a very important role, especially due to the higher number of interfaces between parts. Changes in the MK02 fixator stiffness with configuration changes are similar to those seen with other linear fixators. The pin behavior changing substantially when in a system provided an issue when modeling which required less assumptions to be made. Even though computationally the cost was not increased significantly, the model development required extensive work.