# Upper Limb Orthoses: Integrating Topology Optimization and 3D Printing for Custom Fit and Function
## 6 Discussion  
To avoid using patient data and causing discomfort during the prototype creation, we used the wrist of one of the co-authors as a reference for the design and manufacturing of the personalized wrist brace. This approach allowed us to develop the personalized wrist splint without compromising patient privacy and comfort.  
The findings of this study demonstrate that combining topology optimization (TO) with additive manufacturing (AM) technology presents a promising strategy for designing and producing personalized wrist splints. However, certain practical factors must be carefully considered to ensure the effective application of this approach.  
One such issue is the scanning procedure of the injured hand, which, due to swelling, may change shape and may later on cause discomfort. To address this, it is suggested that the 3D splint be applied at a later point in time, once the conventional cast/resin has  
Figure 16: Customized optimized wrist braces: (**a**) wrist flexion support brace, (**b**) 22-point force distribution brace.  
\begin{table}
\begin{tabular}{c c c} \hline \hline
**3D Printer** & **Stratasys Dimension Elite** & **FlashForge Creator 3** \\ \hline Layer Height & 0.254 mm & 0.2 mm \\ Filament Deposition Angle & \(\pm\)45\({}^{\circ}\) & \(\pm\)45\({}^{\circ}\) \\ Printing Temperature & 270 \({}^{\circ}\)C & 240 \({}^{\circ}\)C \\ Chamber Temperature & 75 \({}^{\circ}\)C & - \\ Infill Pattern & Rectangular & Rectangular \\ Infill Density & 100\% & 100\% \\ External Perimeters & 1 & 1 \\ Support Pattern & Rectangular & Tree Form \\ \hline \hline \end{tabular}
\end{table}
Table 3: 3D printer parameters.  
been in place for 2-4 weeks. This will allow for more accurate scanning and the ability to continue with a 3D brace for 1-2 months. It may also be worthwhile to scan the hand while in a cast to obtain accurate information about the three pressure points, as researched by [31], although this may be challenging due to the thickness of the cast and coating.  
The process also needs to be automated to guarantee the fast production of the 3D-printed brace, ensuring a smooth transition between a conventional brace (2-4 weeks) and the 3D-printed one. An optimization of the printing procedure is required to further minimize the time needed to provide the brace to the patient.  
Several limitations from the used material were also found during the conduct of this study. ABS can be used to demonstrate a proof of concept, but it comes with the following limitations: (i) poor 3D printing performance; (ii) degradation from UV radiation and moisture absorption; (iii) poor surface finish; (iv) toxic fumes from 3D printing procedures; (v) poor sustainability. These limitations make the choice of ABS unacceptable considering the release of a 3D-printed brace to the general public. Our next research step will consider different materials, such as polycarbonate (PETG) and nylon, as well as composite materials produced by our recycling machine.  
Finally, the waterproof construction of the 3D wrist brace may have significant implications for the treatment of simple fractures and tendonitis in children and adults, as it can make daily application easier, more comfortable, and more effective. Further research in this area may be warranted to explore the potential benefits of this approach for a wider range of clinical cases.