# Anatomical-Based Customized Cervical Orthosis Design in Automation
## 4 Discussion  
One can adopt commercial computer-aided design software that can also be used to design a cervical orthosis from body scan data. However, this software is usually used for parameterized parts' design purposes, making setting a symmetrical centerline path and its coverage regions with consistent widths challenging. In our previous study, the front piece's coverage regions supported setup manually, encountering complex and demanding work that required operators to make long-hour adjustments [3]. In contrast, our design software generates the coverage area by expanding from the central line of the orthosis, ensuring a consistent width. The central line template is pre-symmetrized, allowing for the creation of a more symmetrical orthosis even if the human body is not perfectly symmetrical. Therefore, the customized symmetrical orthosis can correct a neutral minor skew head posture. Moreover, several issues arise from human factors in design variability using general CAD software. Our design is based on the crucial anatomical infrastructure, which may cause inconsistency when manually setting the infrastructure, such as anatomical neck features and feature lines. A suitable allowance can prevent pressure ulcers and maintain uniform contact forces between the user and the orthosis when worn over a long period. On the other hand, general CAD software cannot generate allowances from an irregular, complex, and concave surface. Assuming a head weight of 6 kg, we embedded the strength requirement in the software: the thickness of both the front and back pieces should be at least 5 mm from FEA results. If the head weight exceeds 6 kg, increasing the thickness is necessary to ensure safety and adequate support. [PERSON] included four types of orthoses--a soft collar, rigid collar, Plastazote collar, and handmade custom-fit collar--to investigate the restriction of cervical spine motion [23]. The soft-material collar had the least effective immobilization due to its lack of a rigid support structure. In contrast, the custom-fit collar and rigid collar provided better immobilization. Given the poor immobilization capability of the soft collar, this study focuses on designing orthoses using rigid materials. The cervical orthosis designed in this study focuses on strength, aesthetics, and ease of wear. It strategically uses key anatomical landmarks on the neck as support areas, aiming for \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Thickness** & **Extension** & **Left Lateral Flexion** & **Right Lateral Flexion** \\ \hline
3 mm & 14.78 & 8.09 & 11.38 \\
4 mm & 25.96 & 11.13 & 14.60 \\
5 mm & 31.94 & 16.04 & 17.51 \\
6 mm & 48.78 & 26.30 & 34.28 \\ \hline \hline \end{tabular}
\end{table} 
Table 6: Maximum load (N) of front piece orthosis for fatigue strength. \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Thickness** & **Extension** & **Left Lateral Flexion** & **Right Lateral Flexion** \\ \hline
3 mm & 39.20 & 38.97 & 45.95 \\
4 mm & 69.04 & 50.18 & 57.50 \\
5 mm & 70.27 & 62.43 & 68.03 \\
6 mm & 98.03 & 72.13 & 91.80 \\ \hline \hline \end{tabular}
\end{table} 
Table 7: Maximum load (N) of back piece orthosis for fatigue strength. a compact yet practical design. Specifically, it supports the head's weight through the chin, mandibular angles, and the lower edge of the occipital bone while anchoring the orthosis to the sternum, clavicles, side neck points, and C7 (Figure 1b). This orthosis avoids contact with the throat, esophagus, aorta, and airways, ensuring the wearer usually breathes and swallows. The design considerations ensure that the orthosis provides necessary support without compromising comfort, avoiding areas that could lead to discomfort or hinder essential functions. Due to usability considerations, rigid orthoses are generally designed as two-piece structures because their rigidity prevents deformation, necessitating division into two pieces to be effectively worn on the neck.