## 2 Method
### Narrative Review  
A narrative review methodology was selected, utilizing the Google Scholar online database to capture various technologies related to hand orthoses produced via MEX printing. The search employed various combinations of keywords, including: 'additive manufacturing', '3D printing', 'fused filament fabrication', 'FF', 'FDM','material extrusion', 'hand', 'wrist', 'finger', 'thumb', 'upper limb', 'upper extremity', 'orthosis','split', 'device', 'assistive', 'passive', 'active','static', 'dynamic', and 'exoskeleton'.  
After retrieving the search results, specific inclusion criteria were applied to refine the literature search. The inclusion criteria were as follows:  
* The paper is accessible to the authors and is a scientific article written in English.
* The described device is a hand orthosis produced via MEX printing.
* The device is intended for medical purposes.
* The study presents the mechanical aspects of the designed hand orthosis.
* The study includes a figure illustrating the designed device.
* The study provides sufficient information on the design choices.  
The search and selection process were guided by the authors comprehensive understanding and experience in hand orthosis design and MEX technology. The aim was to provide a broad overview of different design approaches in the field, by including studies representing both common and less common design choices, showcasing the variety of and rationale behind different approaches. Consequently, a diverse set of hand orthoses were selected, to demonstrate distinct design features and to reflect the range of possibilities in this area.  
Numerous 3D-printed devices aimed at assisting other joints of the body in ADL were not included, due to the focus on the hand. Therefore, devices that did not involve the wrist or finger joints, or were not at least partially produced via MEX technology, were excluded. The review concentrated on design approaches in this field, hence not all repeated design choices were included.  
The framework was developed to review and analyze the substantial number of studies identified in the literature search. While the review does not attempt to be exhaustive, it aims to provide a representative overview of the various design types and their applications. By categorizing devices as static or dynamic, the review highlights differences and similarities, providing insights into the rationale for selecting certain designs. Grouping the different aspects of design choices was intended to facilitate an understanding of the variety within the field and to assist future designers in recognizing established trends and design alternatives. The authors expertise in the field facilitated a qualitative synthesis of the most relevant and significant developments. The review does not cover every design choice made for each device, but instead highlights specific, key, and previously unmentioned design choices.  
Recognizing the advantages of a narrative approach, which allows for a focused exploration of the most relevant works, the authors acknowledge that this methodology may have introduced some bias in the selection and interpretation of the literature. However, every effort has been made to present a balanced and comprehensive overview that accurately reflects the diversity of design approaches within hand orthoses produced via MEX printing, drawing on the authors' expertise and deep understanding of the field.