User-Centered Design Framework for Personalized Ankle–Foot Orthoses

Abstract

Background/Objectives: Integrated design and simulation solutions enable the manufacturing of advanced personalized orthotics that improve patients gait characteristics and balance. The success of such a rehabilitation approach is highly dependent on compliance, i.e., users wearing the orthosis consistently. Specifically, for most young children, functionality is secondary to appearance and peer perception. However, the starting point of the traditional design approach is to address functionality and then try to make the appearance more palatable to the wearer. As a result, compliance is a common issue, resulting in slow and uneven rehabilitation progress. Methods: This work proposes a method that inverts this traditional approach and devises an attractive light design that can be adapted to ensure structural soundness. Results/Conclusions: The broader framework is called the user-centered design process. The main advantage is in the flexibility of the added manufacturing approach, allowing for a personalized design that is attractive to the user, promoting higher compliance.

1. Introduction

Ankle–foot orthoses (AFOs) are essential devices in pediatric rehabilitation, particularly for children with conditions such as cerebral palsy, foot drop, or neuromuscular impairments [1,2,3,4]. These devices aid in enhancing mobility, preventing deformities, and improving overall gait. However, adherence to prescribed AFO use among children and adolescents remains a persistent challenge [5]. In a comprehensive study, Bertini et al. [6] reported that 22% of prescribed orthotic devices were never used and 27% were discontinued after initial use, highlighting a critical gap in their effective utilization.

The recommendation for the continuous use of AFOs for an average of 7 h per day, except for periods dedicated to hygiene purposes, is believed to optimize the benefits associated with gait improvement and the alleviation of linked to foot disorders [7]. However, scientific studies have reported that between 6% and 80% of AFO users wear their orthotic devices less frequently than once a month [8,9]. For instance, Ejm [9] reported that 1 out of 15 AFOs were not used at all, suggesting that approximately 6.67% of users do not wear their orthotic devices. Myers et al. [7] documented that their participants wore their AFO for an average of 4.8 to 4.9 days per week. Key factors influencing non-compliance include the following:

• Discomfort and pain: Common complications with orthotic devices, such as foot calluses and ulcerations (13%), contribute to emotional distress and reduced tolerability among users. Bertini et al. [6] discovered that AFO users frequently reported symptoms of depression and physical and general fatigue, with emotional distress being the reason for 17% of abandonment of the orthoses altogether. AFO users complained mostly of skin reddening (52%) and moderate to severe pain (41%), highlighting the need for improved design approaches to reduce such adverse effects. Comfort is essential, as devices that can be worn comfortably for extended periods tend to achieve higher compliance rates; this is dependent on appropriate fitting and the use of non-irritating materials [10,11].
• Psychosocial factors: These include the perception of the device, cosmetic concerns, and peer perceptions adolescents [12]. Peer influence and social acceptance can affect adherence, especially among adolescents, who may feel self-conscious about wearing orthotic devices [12,13]. Okçu et al. [14] emphasized that effective patient education and addressing device comfort can enhance compliance and overall satisfaction.
• Functional limitations: Poor integration with footwear, bulkiness, and difficulty in donning or doffing AFOs further discourage their consistent use. The weight of the device is crucial; lighter orthoses are preferred due to their reduced bulk, making them easier to wear for prolonged periods [11,15,16]. Ease of use is another factor that supports compliance. Orthoses that are easy to put on, take off, and adjust independently are more likely to be used regularly [17,18]. Durability contributes positively to user satisfaction as well, with robust devices that maintain their functionality over time requiring fewer repairs or replacements [19]. In addition, Bertini et al. [6] reported that muscle weakness, particularly in foot dorsiflexion and plantarflexion, affects the tolerability and effectiveness of AFOs. Later, Mohammadi et al. [5] introduced the first AFO with modular artificial muscles, but their preliminary results addressing users’ comfort were inconclusive.

Esthetic considerations also affect user experience, especially for highly visible orthoses, like those designed for the upper and lower limbs. Designs that are discreet or visually appealing tend to enhance user confidence and compliance [11,20]. A previous study reported that esthetic preferences vary by age: younger children prefer vibrant and customizable design features (e.g., colors, graphic designs such as Superman and unicorns, texture, etc.), while older children prefer discreet and visually inconspicuous options [16]. In addition, the ease of integration of users’ shoes with AFOs, esthetic enhancements (e.g., lights, colors), and sleek designs have shown promise in improving engagement, particularly among older children [16,21]. Cosmetic concerns, preferences over function, and negative experiences with homemade or off-the-shelf versions also impact compliance and satisfaction levels among patients [22].

The traditional method of creating AFOs involves negative molding of a cast, or the direct molding of thermoplastics to an individual’s leg [23]. These manufacturing approaches often compromise comfort and fit, and significantly reduce the possibility of any creative freedom [2]. Additive manufacturing (AM) has emerged as a promising solution. AM offers a significant advancement in customization that improves biomechanical function, comfort, and esthetics [24,25,26,27]. Unlike traditional manufacturing, AM enables the following:

• Precision fit: The use of 3D scanning enables precise modeling of a child’s anatomy, allowing the AFO to conform to the shape and size of the user and ensuring a better fit [3], addressing the specific requirements of each user [28,29] and reducing the risk of complications such as pressure sores [6,27].
• Selection of lightweight and durable structures: AM facilitates the creation of complex, lightweight geometries that improve wearability without compromising strength
• Incorporating complex geometries and functional features: AM enables the incorporation of complex geometries and functional features that would be difficult or impossible to achieve with traditional manufacturing methods [2].

These findings underscore the complex interplay between physiological comfort, psychological well-being, and therapeutic adherence in pediatric orthotic intervention. Comfort and fit are dominant issues; traditional rigid AFOs often lead to discomfort, impacting motivation to wear them [30]. Despite these challenges, some studies suggest that improved designs and personalized support could enhance adherence rates. However, the variability in usage highlights the need for tailored interventions to address individual user needs and contexts [31]. In this work, we set a framework for functionality that follows one proposed by an earlier study [32]. The guiding principles we formulated are as follows:

• User acceptance and esthetic preferences
• Comfort and wearability
• Injury prevention.

These guiding rules aim to address age-group-specific objectives and overcome key challenges affecting compliance with a rehabilitation routine that necessarily includes prolonged and consistent wearing of the prescribed orthotics. Hence, the purpose of this study is to develop and validate a systematic framework—enabling the design of personalized orthotics for young children—that integrates the abovementioned principles.

Current approaches to AFO design often emphasize functionality at the expense of child acceptance and comfort, leading to reduced compliance and compromised treatment outcomes. Our methodology uniquely addresses this challenge by incorporating the child’s esthetic preferences during the initial design stage, while ensuring that biomechanical requirements are met through engineering validation. This holistic approach advances pediatric orthotic design by concurrently considering the child’s visual preferences, physical comfort, and safety requirements, thereby creating AFOs that children are more likely to wear consistently and effectively. The process should also incorporate the selection of appropriate additive manufacturing materials, following the procedure developed by [33,34]. In summary, the aim is to establish a robust process for a personalized design, with a starting point of visually acceptable design for the user, while meeting all structural and biomechanical requirements.

2. Materials and Methods

2.1. Outline of the User-Centered Design Process

This study used a user-centered design process, adapted from established engineering design principles, to develop and evaluate an innovative AFO design (Figure 1). The process started by identifying the limitations inherent in existing AFOs, such as discomfort, restricted mobility, and insufficient individualization. Background research was undertaken to assess current AFO designs, materials, and manufacturing techniques, as well as the specific requirements of individuals with conditions necessitating the use of AFOs (e.g., foot drop, cerebral palsy).

Specific design criteria were established, encompassing comfort, range of motion, ease of donning and doffing, and durability. Collaborative brainstorming sessions yielded numerous AFO design concepts, integrating advanced materials and fabrication methods, including additive manufacturing. These concepts were systematically evaluated against the pre-defined criteria in order to select the optimal design. A prototype AFO was subsequently fabricated, incorporating features such as adjustable stiffness and a personalized fit. The prototype underwent rigorous testing and iterative redesign, guided by biomechanical analysis and user feedback. This iterative process persisted until the AFO fulfilled the pre-defined requirements for functionality, comfort, and user satisfaction.

2.2. Define the Problem

In this phase, we systematically addressed key challenges and limitations associated with current pediatric AFOs by conducting background research. We then identified specific user needs and translated them into actionable design requirements.

Although AFOs can enhance gait stability and decrease energy expenditure, patient compliance is significantly influenced by factors such as the severity of the disease, the degree of customization, and the perceived benefits of the device. Research has consistently indicated suboptimal compliance rates among patients, with reported abandonment rates of 31% and complication rates of 69% associated with AFO use [6].

Current AFO designs are limited by materials, structure, and esthetic requirements. For example, thermoplastic materials often lack breathability, leading to excessive sweating and discomfort, especially in extreme temperatures [16]. Structural rigidity around the malleoli and other areas can cause pressure sores, superficial skin irritation, and reduced mobility. The bulky design of many AFOs restricts footwear options and exacerbates difficulties in fitting both the AFO and accompanying shoes. Esthetic considerations are frequently overlooked, leaving users, particularly older children, feeling self-conscious and reluctant to wear the devices in public [16]. Furthermore, the process of acquiring an AFO often involves delays, fabrication errors, and inconsistent practitioner approaches, frustrating both users and caregivers [16].

These limitations necessitate further investigation to develop user-centered, functional, and esthetically pleasing designs while improving service delivery, to enhance user satisfaction and adherence to AFOs.

2.3. Specify the Requirements

The design requirements for the AFO were established to balance user preferences with functional and safety standards, thereby providing a solution that is child-friendly and easy to use. Customization was emphasized, necessitating a 90% accuracy in fitting assessments conducted by trained orthotists to ensure a tailored fit to individual limb morphology.

Safety was a principal concern, with adherence to ISO 10328 standards and a minimum safety factor of 2.0 established in load-bearing capacity tests [35]. Mobility was enhanced through lightweight construction, with a maximum weight limit of 900 g, and gait support was assured by facilitating smooth transitions between swing and stride phases.

Comfort and ventilation were addressed by requiring users to walk pain-free for a duration of 30 min, alongside the incorporation of strategically placed ventilation channels, which achieved an optimal breathability. Skin protection was ensured through the use of smooth edges and hypoallergenic materials to reduce the risk of irritation.

Ease of use was prioritized, enabling caregivers to apply or remove the AFO within one minute and complete maintenance in under five minutes. Functional capabilities included moderate resistance to prevent foot-slap in 85% of users, unrestricted ankle rotation up to 45 degrees, and drop-foot prevention via 90-degree leg support during swing phases [36]. Compatibility with 80% of children’s shoe sizes was considered, and the design process ensured that the AFO could be manufactured and delivered within a short turnaround time frame, preferably three days after measurement [37].

2.4. Brainstorming Solutions

The ideation phase emphasized user-centered design principles, with a particular focus on pediatric empowerment through creative engagement. The conceptual development process yielded several design solutions, demonstrating playful, child-friendly designs inspired by familiar shapes and characters, such as the “Monkey AFO”. The Monkey AFO uses its arms as functional straps, offering both esthetic appeal and practical utility, while its curved body ensures comfort and fit around the leg (Figure 2).

Additionally, color palettes and patterns inspired by children’s interests, such as TV shows, toys, and nature, were incorporated into other designs (e.g., SpongeBob and snake-inspired designs). These visuals illustrate how themes and bright colors such as yellows, brown, pink, orange, and blues are used to evoke empowerment, self-expression, and engagement among young users. The focus during this stage was to generate a wide range of ideas, setting aside feasibility considerations to encourage innovation. Some concepts were comprehensive designs, while others were collections of features and ideas to be refined in the next stage.

2.5. Develop the Solution

2.5.1. Anthropometric Measurement of the Foot

The initial step of the development of a design solution involved conducting anthropometric measurements of the foot and leg. These measurements were obtained by collecting sample measurements of participants’ feet and legs (Figure 3). The measurement of arch length was based on [33,34].

Anthropometric measurements were conducted using standardized tools to ensure accuracy and consistency. Lengths were measured using a flexible, non-elastic tape measure (precision ±1 mm) and a digital caliper (precision ±0.01 mm) for finer measurements. Circumferences and diameters were measured exclusively with a flexible tape measure, following measurement guidelines for anthropometric research [29,38,39].

To minimize potential errors in anthropometric measurements, we employed the following approach: Two independent researchers conducted each measurement three times under controlled conditions. The average value of these six measurements (three from each researcher) was used as the final value for each parameter. This approach ensured consistency and reliability, reducing the influence of individual variability or transient errors. By incorporating this method, we aimed to minimize measurement error and enhance the accuracy of the data, ensuring their reliability for informing the final design.

2.5.2. Computer-Aided Design (CAD)

The CAD process began with extensive sketching to define the overall design concept. These sketches served as a visual exploration tool for various design features, such as the shape, structure, and functional components of the AFO. This step included considerations for edge contours, overall height, base shape, and strap configurations.

CATIA software v5 was used for design development (Figure 4), and parametric models were also used to facilitate flexibility in the design process. This approach enabled the adjustment of key parameters, such as dimensions, curves, and attachment points, to accommodate user-specific needs or esthetic variations. Consequently, this approach ensured that the model could be easily customized and iterated upon.

2.5.3. Finite Element Analysis of the Proposed Design Solution

The finite element analysis (FEA) of the AFO design was conducted using Fusion 360 software to evaluate the structural performance under simulated loading conditions (Figure 5).

• Model Preparation

The AFO design model was imported into Fusion 360 for pre-processing. To facilitate mesh generation, the model underwent remeshing using the Quad Remesher extension by Exoside. This tool enabled the generation of a high-quality quadrilateral mesh, thereby ensuring uniform element distribution and an accurate representation of complex geometries. The target quadrilateral count was iteratively adjusted to achieve an optimal balance between computational efficiency and detail. The quality of the elements was verified to ensure all elements met the standard criteria for aspect ratio and skewness.

• Boundary Conditions and Loading

The boundary conditions were applied to simulate realistic usage scenarios. The upper boundary of the ankle portion was constrained in all planes, representing the connection point where the AFO interfaces with the user’s leg. A static load corresponding to a child’s body weight (15–20 kg) was applied uniformly across the base of the AFO to simulate the typical force exerted during use. The load range was selected based on a normal child’s weight data.

• Material Selection

Three commonly utilized materials for AFO fabrication were evaluated to compare their mechanical performance:

• Nylon (Polyamide 12—PA12), a widely used material in Selective Laser Sintering (SLS) 3D printing. PA12 is known for its high strength, elasticity, low density, and good chemical resistance, making it a versatile material for orthotic applications. The low cost of Nylon PA12, combined with its compatibility with SLS technology, makes it cost-effective for the production of multiple orthoses tailored to diverse user needs. Nylon is recyclable, further supporting environmentally sustainable practices (Figure S1).
• Polypropylene (PP), a semi-rigid, lightweight thermoplastic selected for its durability and flexibility. While PP is soft, making it comfortable for users, its raw materials are expensive.
• High-Density Polyethylene (HDPE), known for its strength, durability, and resistance to chemicals and moisture. HDPE is frequently used in 3D printing for applications requiring high durability. While the material costs of HDPE are relatively cheap, the manufacturing is considered time-consuming and expensive.

• Material properties such as Young’s modulus, Poisson’s ratio, and density were assigned based on the published literature and material data sheets (Figures S1 and S2).
• Mesh Generation: To ensure accurate simulation results, the model was meshed using a quadrilateral mesh generated by the Quad Remesher. The mesh was refined in critical stress-concentration areas, such as the ankle and base regions, while maintaining coarser elements in less critical zones to optimize computational resources.
• The results were analyzed to compare the performance of the three materials. Stress distribution plots, deformation visualizations, and factor of safety (FoS) metrics were documented for each material to identify the most suitable option for AFO fabrication. The analysis also informed potential design improvements to address stress concentration areas or excessive deformation.

2.6. Build a Prototype

The final design was fabricated using an additive manufacturing processes (i.e., as 3D printing) with Nylon PA12 material (Figure 6). This methodology enables the modification of traditional designs to yield a final functional prototype that is both esthetically pleasing and effective.

2.7. Test and Redesign

The 3D-printed AFO underwent user testing involving individuals that were representative of the intended population (Figure 7).

The research team wore the AFO prototype for a pre-defined duration, during which key activities, such as standing, walking, ascending and descending stairs, and engagement in light physical activity, were observed. The AFO was fitted by the participants themselves or with assistance from carers to evaluate the ease of application and removal. The prototype was evaluated based on the following criteria:

• Comfort: Users reported the absence of pain, irritation, or overheating during use.
• Usability: Ease of putting on and removing the AFO, and whether the straps provided adequate support.
• Mobility: Users’ ability to walk, climb stairs, and engage in daily activities without significant hindrance.
• Durability: Observations of the prototype’s ability to withstand use without visible deformation or wear.
• Esthetics: Users’ feedback on the appearance of the AFO and whether it was perceived as empowering or appealing.

3. Results and Discussion

The methodology employed in this study was designed to systematically address the limitations of existing AFOs through a user-centered design and engineering approach (Figure 1). Current AFOs, as a rule, prioritize functionality while neglecting user comfort, esthetics, and adaptability, resulting in challenges such as poor compliance, discomfort, and diminished user satisfaction. By synthesizing insights garnered from user feedback, esthetic research, and engineering analysis, this study sought to create AFO designs that enhance both functional performance and the emotional well-being of users (Figure 2).

3.1. Design Considerations

During the design process for this AFO, once anthropometric data were collected (Figure 3), they could be easily integrated into CAD software to develop custom AFO designs tailored to individual users (Figure 4).

We used the ‘extrude’ approach to modify the support’s thickness to the desired height and then shape it by cutting away material to create a tree-like form. This approach met the esthetic design requirement, aiming to empower the user. Additionally, we used a filleting tool to create soft, rounded edges, ensuring comfort by preventing pinching or sharp transitions against the skin. The design also effectively distributed torque from the support down to the base by gradually connecting the two components. The current study prioritized user empowerment in the design by incorporating visually engaging elements that promote compliance and self-expression. Existing AFOs often adopt a closed “boot” design that restricts airflow and contributes to overheating. Our designs integrated strategically placed ventilation features to improve breathability and overall comfort. Our designs also allowed for the AFO to remain integrated within a shoe, facilitating streamlined usability. The used of CAD-based approaches enables easy adjustments and iterative refinement, rendering the manufacturing process more flexible and efficient.

3.2. Customization

One of the key decisions in our design approach was the selection of anthropometric measurement methods over advanced 3D scanning technologies, as has been suggested previously [28,29]. While 3D scanning offers precision and automation, it is often inaccessible in remote Australian areas and developing regions such as Loas, the Pacific Islands, and parts of Africa, where such advanced technology may not be readily available.

The reliance on anthropometric measurement techniques makes this approach highly adaptable to regions where 3D scanning equipment is not feasible. Using standard tools such as tape measures and calipers, users or healthcare providers can collect precise measurements of the foot and leg by following established guidelines for anthropometric research. These guidelines ensure consistency and reproducibility in measurement collection, even when conducted by individuals with minimal technical expertise. This makes the methodology suitable for communities with limited access to healthcare infrastructure or advanced manufacturing technologies. This approach addresses the gap between advanced healthcare technology and the needs of remote or resource-limited communities, enabling a global impact on mobility and quality of life.

However, in urban or resource-rich environments, 3D scanning could play a complementary role by improving the accuracy of anatomical data capture, reducing fabrication errors, and expediting the production process. The ability to produce detailed 3D models of limb morphology could also enhance the integration of advanced manufacturing techniques, such as additive manufacturing, for creating more precise and bespoke designs. While our approach focuses on providing low-cost, scalable solutions for underserved regions, the potential for hybrid systems combining anthropometry and 3D scanning in diverse healthcare settings warrants further exploration in future work.

3.3. Engineering Evaluation

FEA simulations were performed on the AFO designs to assess their performance under static loading conditions, and provided critical insights into the feasibility of our designs under the loading conditions. The results demonstrated that the proposed design (Figure 5) displayed moderate deformation (12 mm) and low stress levels (1.8 MPa), with acceptable safety factors (FoS = 15) for Nylon material.

The FEA demonstrated the importance of material selection in balancing strength, flexibility, and weight (400 g). Nylon consistently outperformed other materials, showing the lowest deformation and highest safety factors across all designs. This material’s properties align well with the requirements of lightweight yet durable AFOs.

The manufacturing flexibility provided by CAD modeling and the use of 3D printing technologies, allowed for rapid prototyping and iterative refinement (Figure 6). This approach reduced the time and cost associated with traditional molding methods while enabling the creation of customizable designs tailored to individual users.

3.4. User Evaluation

Physical testing was performed by using the printed AFOs on group members (Figure 7), with a focus on user experience, particularly in terms of comfort and fit. The physical testing of the prototypes revealed several enhancements in comparison to existing AFOs:

• Comfort and Fit: Discomfort was observed around the calf connection. This was primarily due to the unrounded edges of the 3D-printed material. This sharp geometry created localized pressure points, leading to skin irritation and discomfort during wear. This issue highlights a design oversight rather than a material flaw, as simple modifications like rounding edges with a fillet could mitigate these effects. These findings highlighted the importance of incorporating ergonomic design principles into AFO development, particularly for pediatric users, whose skin is more sensitive to pressure and friction. Modifying the material’s flexibility and further refining the edge geometry would likely alleviate these concerns.
• Flexibility and Stiffness: The prototypes provided adequate alignment support; however, they exhibited excessive stiffness, which impeded natural gait and resulted in discomfort during prolonged use. The rigidity observed in the design was directly attributed to the selection of material and the structural design, which aimed at providing stability and maintaining foot alignment. However, this stiffness restricted natural movement around the ankle, inhibiting gait dynamics and contributing to an unnatural walking experience. While stiffness is beneficial for alignment and stability, excessive rigidity can impede compliance by causing fatigue and discomfort during extended use. In practical terms, future iterations could focus on modifications to the 3D-printed materials, such as using hybrid materials or layered structures to introduce localized flexibility around the ankle. Additionally, design modifications, including integrating hinges or segmented components, could be potential solutions to enhance range of motion without compromising support.
• Ease of Use: The integration of adjustable straps and compatibility with standard footwear significantly enhanced usability. This feature enables children to independently don and doff the AFO, which is essential for promoting compliance and fostering autonomy.
• Esthetic and Psychological Impact: A survey-based methodology to evaluate the psychological impact of esthetic designs was developed to evaluate the relationship between AFO designs and perceived empowerment using a five-Likert rating scale, ranging from “Children will not feel empowered wearing this AFO” (1) to “Children will feel extremely empowered wearing this AFO” (5). This survey was only conducted internally with project team members, due to resource limitations and time constraints. This approach allowed us to validate the framework, refine the survey structure, and ensure consistency in the rating process. The visual appeal of the designs was positively received by the intended users, aligning with the objective of creating a device that fosters empowerment and self-expression. The actual design was an initial prototype that could be adapted to the body surface to increase the functional comfort. We refrained from using a composite structure with soft pads on the interfaces in order to keep the cost down. Adding appropriate foam pads would address the comfort issue, but a less costly option is also possible.

3.5. Material Selection

Material selection is a critical aspect of designing pediatric AFOs, requiring comfort, durability, cost, and environmental sustainability to be balanced. Our evaluation focused on three candidate materials—Nylon PA12, Polypropylene (PP), and High-Density Polyethylene (HDPE)—to determine the most suitable option for our design.

In addition to superior mechanical and chemical properties for medical applications like AFOs, the smooth surface finish and elasticity of Nylon PA12 could reduce pressure points and irritation. It can be treated or padded for enhanced skin comfort, making it suitable for prolonged wear. The low cost and recyclability of Nylon PA12 make it sustainable for the production of multiple orthoses tailored to diverse user needs.

It was observed that the semi-crystalline structure of PP caused significant warping during cooling, complicating its use in 3D printing. The high material and production costs of PP also limit its feasibility for pediatric AFOs. Similarly, HDPE is prone to warping and exhibited poor adhesion during 3D printing, necessitating precise temperature control and pre-treatment.

Among the three materials, Nylon PA12 was selected as the optimal choice for pediatric AFOs due to its balance of mechanical performance, skin comfort, cost-effectiveness, and sustainable production, with minimal material waste.

3.6. Implications and Future Directions

The results reveal the importance of adopting a holistic approach to AFO design, integrating engineering performance, user comfort, and esthetics. While the prototypes address many of the limitations of current AFOs, further optimization is required, particularly in reducing stiffness and addressing fit-related discomfort. The initial evaluation of our AFO design focused on short-term metrics, such as comfort, ease of use and immediate user satisfaction.

We acknowledge the importance of long-term testing for a comprehensive evaluation of the performance, durability and impact on therapeutic outcomes of AFOs. To achieve this, future studies could also benefit from advanced user testing, including long-term wear trials and motion analysis, to assess the functional and psychological impacts of the designs. To ensure structural integrity, particularly in high-stress regions like the ankle and heel, repeated load-bearing evaluations and material fatigue analyses to ensure structural fatigue analysis should be considered. Periodic surveys with users should be conducted to evaluate prolonged skin comfort, ease of use, and esthetic satisfaction, thereby determining any changes in user preferences and device functionality. Furthermore, gait analyses using a motion capture system such as the Vicon system, force plate technology, and gait analysis software should be considered to monitor potential improvements in spatial–temporal parameters such as step length, stride symmetry and cadence. Additionally, muscle strength, particularly in foot dorsiflexion and plantarflexion, should be evaluated to monitor improvements in functional mobility. These tools and methodologies will provide objective metrics to determine whether the AFO supports natural gait patterns and contributes to improved therapeutic outcomes.

The anthropometric approach empowers users and carers to participate actively in the design process. By providing simple tools and instructions, individuals can measure their foot and leg dimensions accurately and send these data to a designer. To ensure accuracy and reproducibility, future work should focus on developing standardized, easy-to-follow protocols for anthropometric measurements that are tailored to AFO design. Training materials, such as instructional videos or illustrated guides, could be created to assist users and healthcare providers in collecting reliable data. Furthermore, future iterations of this methodology could integrate emerging technologies, such as mobile-phone-based 3D scanning. This would provide a bridge between low-tech and high-tech solutions, expanding applicability as technology becomes more widespread in underserved regions.

This study demonstrates the potential for modern design and manufacturing techniques to create AFOs that not only improve mobility and alignment, but also empower users through comfort, usability, and self-expression. By prioritizing user-centered design principles, AFOs can shift from being solely function-focused devices to holistic solutions that enhance both physical and emotional well-being.

In this study, we only incorporated a survey-based methodology to validate the framework, refine the survey structure, and ensure consistency in the rating process. However, as the survey did not involve external participants, future studies will be required to extend this methodology to include children and their caregivers, ensuring more comprehensive and generalizable results. Future work should also incorporate established questionnaires, such as the Pediatric Quality of Life Inventory (PedsQL) or the Self-Perception Profile for Children (SPPC), to evaluate psychological outcomes more robustly. These tools will allow for a deeper understanding of how esthetic design impacts user confidence, social acceptance, and compliance with prescribed use.

Although this study demonstrated the utility of materials such as Nylon 6 for 3D-printed AFOs, future research should explore alternative materials that have already been obtained following the procedure presented by Hu et al. [33] and Hu et al. [34], and manufacturing methods that balance cost, durability, and user comfort. Developing low-cost 3D printing solutions that are tailored for use in developing regions could further enhance the scalability of this approach.

4. Conclusions

This study highlights the importance of a user-centered design in enhancing adherence to and satisfaction with AFOs. By systematically addressing key factors such as comfort, functionality, esthetics, weight, ease of use, and customization, we propose design solutions that are tailored to the diverse needs and preferences of users. Our research has established a framework for functionality, informed by prior studies, that focuses on principles such as user acceptance, comfort, wearability, and injury prevention. Incorporating user feedback was found to be a key strategy to address persistent issues, including poor fit, skin irritation, and psychological discomfort, which often lead to device rejection or inconsistent use.

The project also explored the potential of additive manufacturing to create more comfortable and engaging AFOs for children. This approach sought to mitigate non-compliance caused by discomfort and unappealing designs, while advancing functionality and esthetic appeal. Our methodology encompassed concept development, prototyping, testing, and iterative refinement. Beyond meeting functional requirements, these solutions must also address esthetic and psychological factors to enhance the overall user experience.

Future studies should expand on these findings by exploring advanced manufacturing methods, such as additive manufacturing, and integrating emerging technologies, such as smart materials, to further personalize and optimize AFO performance. By fostering both theoretical and practical advancements in AFO design, we hope to contribute to a significant change in rehabilitation technology that prioritizes user satisfaction and clinical effectiveness.