For many transradial amputees, harness and cable-operated limbs are the only accessible prosthetic option. One of the drawbacks of this prosthesis is its inability to firmly grip small objects. The Additio system is a solution to this quality-of-life issue.

Additio is an adapter that attaches to a split-hook limb and a range of household tools, such as kitchen implements, cleaning tools, maintenance devices, and personal care items. By connecting these tools directly to a prosthetic limb, amputees can use them without gripping. The system leverages strong magnets, enabling users to easily load and remove tools without twisting or bending.

For millions of arm amputees, split-hook and cable limbs are the most advanced prosthetic technologies available. The cost of more responsive myoelectric hands or neuroprosthetic arms can be upward of ten times greater. These barriers mean that the majority of transradial amputees do not have access to the devices that would best facilitate their daily lives.

The Addiito project began as a co-creation session with a quadruple amputee and split-hook user who identified the greatest challenges he faced in living with his disability. He related that the loss of his hands impaired him far more than the loss of his feet. “Your feet,” he said “really only help you stand and walk. The list of things you need your hands for is endless.”

As a single father, he was responsible for the management of his household and the care of his child. Making a snack for his son was at least a twenty-minute task, because he could not grasp a knife tightly enough to easily cut vegetables or fruit. Opening packages and pouring milk were nearly impossible. These activities were not only challenging, but exhausting and painful as he exerted and strained himself to undertake them.

Additio is designed to improve the quality of life of people living with transradial amputation by making their household environments more accessible. By enabling them to use a wider variety of household tools, Additio aims to help these people participate more fully and independently in activities that support and enrich their daily lives.

There were several ways in which my point of view informed the project and brief. Early on, I resolved that Additio must be durable and simple in order to minimize quality issues. The quality stakes are high for assistive devices, as users rely on them to perform critical tasks and lack alternatives if those devices fail. To that end, I was determined that Additio not rely on batteries or a power supply. For the same reason, I decided that the device must not have buttons or any other moving parts. Quality considerations also drove the inclusion of a durable stainless steel form in the adapter, rather than just a plastic body. Additio’s tools needed to be similarly durable, washable and non-rusting. The requirement that they be non-magnetic was introduced when I decided to use a rare earth magnet as the connecting mechanism between the adapter and the tools.

My point of view also brought scalability requirements to the brief. The most important of these was that Additio be multi-functional to enable the widest number of possible use cases. In order for the device to enhance the lives of as many people as possible, it was also critical that its cost and manufacturing process not introduce barriers. I resolved to create a product that could be produced for less than $20. I felt that this price point would make it suitable for retail markets in North America and Europe, while remaining inexpensive enough to produce for users in the developing world.

The initial co-creation sessions included interviews and an in-depth task analysis of an average day for the co-creator. During this day, I observed him eating, drinking, preparing food, interacting with packaging, opening mail, brushing his teeth, and using an umbrella. To gain a kinesthetic understanding of the limitations of prosthetic hooks, I spent another day wearing a prosthetic hook simulator. In addition to what the co-creator had already shown me, I learned that the hooks could become painful to use, and that they easily damaged household items.

In subsequent weeks and months, I conducted additional interviews and user testing. One important requirement I uncovered at this stage was the necessity for the adapter to work with the full existing hook system. A small number of custom prosthetic tool sets already exist on the market, but all of these involve unscrewing a user’s hook in order to screw in implements like knives or brushes. Consultation with the co-creator revealed why this was not an option. “Taking off my hooks is like taking away my hands. I’m completely helpless without them, and I can’t put them back on by myself.” This inspired me to design an adapter that worked with the full existing hook, and to take it a step further so that the hook retained full functionality while the adapter was attached.

Outside of the co-creation sessions, I referred to psychology journals to research the impact of amputation on self-esteem. In addition to confirming that self-worth can be negatively impacted by amputation and its effects, the research also revealed that a high number of amputees suffer from reclusiveness and anxiety about how they are perceived by strangers. Some amputees ultimately abandon their prosthetics due to the limbs’ “ugliness” and “institutional look”. This guided the decision to borrow from the visual language of consumer products for Additio, and not to use the “Barbie skin” that typically covers prosthetic limbs.

Materials exploration was driven by several other key considerations. In addition to being durable and cost-effective, the chosen material needed to be food safe. This requirement in particular meant that wood was not an appropriate material for Additio. Likewise carbon fiber, while food safe and durable, did not meet the cost requirements. My exploration then turned toward plastics, and I considered various types including acrylics and PVC before selecting ABS as a recyclable material that best met all project requirements.

I consulted with local manufacturers to identify various options for producing the adapter, tool set and tool box. Alternatives included milled engineered plastic and 3D printing, but I ultimately determined that injection molding was the most cost-effective method. This decision influenced the prototype, as manufacturing limitations like undercuts and side action needed to be accounted for in the design. In the prototyping stage, multiple iterations were made to optimize usability, tool connectivity and ergonomic angles. Early prototypes were made using cardboard, while later iterations were 3D printed. User testing was conducted throughout this process to adjust the design and gain co-creator feedback.

The overall objective for Additio is to enable people living with disabilities and reduced manual dexterity to experience better physical and mental health due to increased facility and independence. By making it easier for users to perform everyday tasks, the ultimate aim of the product is to allow them more time, energy and confidence to do the things they enjoy. Enabling users to shift their focus from basic tasks to self-actualizing activities benefits them as individuals while also allowing them richer opportunities to participate in their fields, disciplines and communities.

By providing a more ergonomic approach to these routine tasks, Additio alleviates strain and fatigue, helping its users to better preserve their physical wellness. Furthermore, by removing the barriers presented by everyday tasks, Additio offers the opportunity to experience an increased sense of empowerment and independence. In addition to improving the user’s quality of life, these physical and mental health benefits mean less reliance on the wider health care system in the user’s community.

Finally, Additio is designed to be inexpensive to manufacture, purchase and use specifically to make it accessible to the widest possible number of users. A low-cost solution is more likely to be adopted by local amputee support organizations, while remaining affordable for individuals who cannot access such services. Furthermore, the ability to mass produce this low-cost product means that it can be manufactured and priced to be accessible to users in the developing world.

In trials, the co-creator expressed delight at the increased ability and facility he experienced while using Additio. He was able to chop vegetables much faster with Additio than without it, while exerting less pressure and holding his body at a more ergonomic angle. He also expressed relief at being able to complete the task without adjusting his grip. Tests with other Additio attachments were equally promising. Umbrellas, which had formerly been almost impossible for him to use, became easy to hold in the Additio adapter. In one user trial, the co-creator was able to sweep the floor for the first time since his amputation.

Once the final prototype was ready, I brought it to a group of occupational therapists and a prosthetist for their feedback. The occupational therapists were excited about the project and agreed that it fulfills a real need that has no viable existing solution. One told me that Additio could make a real difference to her clients’ everyday lives. The prosthetist was likewise supportive of the project’s potential. According to him, the only household tool alternatives for amputees are very expensive, custom tools that are not covered by health plans. A local rehabilitation society was very enthusiastic about Additio and expressed interest in partnering to further develop the project.

To take Additio to the next level, more users will need to be engaged for trials to further prove the concept and refine the prototype. I also intend to widen Additio’s scope to include an adapter for people who suffer from arthritis, as these users also experience grip and dexterity issues and struggle to use small household tools. The goal would be for the arthritis adapter to accept the same tool attachments as the amputee adapter, as compatibility between the two tool systems would simplify manufacturing and reduce costs.

While the current model of Additio seeks to give users more time for self-actualizing activities, future developments would focus on enabling those activities directly. Adapters to help amputees play musical instruments, participate in sports, and engage in other leisure activities are possible with further research and development.