A smart brace to support spasticity management in poststroke rehabilitation
This report covers the design of a product to help stroke survivors who are suffering from chronic spasticity manage their everyday activities. In the Netherlands alone, 44.000 people suffer from a Cerebro-Vascular Accident (CVA) each year. A CVA, more commonly known as a stroke, results in brain trauma with afflictions such as paralysis, fatigue and spasticity. It is possible to recover some, if not all, motor function though intensive physiotherapy, which requires long-term stay at a rehabilitation clinic in severe cases. Due to limited room and staff, only 12% of stroke survivors end up rehabilitating in a clinic. The remaining survivors are sent home, and will to travel to the clinic 3-5 times per week for therapy as part of the outpatient rehabilitation. Adjuvo Motion, a young start-up, aims to improve the situation of stroke survivors by bringing the rehabilitation centre to their home through the Adjuvo Platform, which allows them to perform exercises in the context of virtual tasks. They proposed an assignment to extend their product portfolio with a Range of Motion assessment device that is suited for those suffering from spasticity. Spasticity occurs in roughly 60% of stroke survivors with varying degrees of intensity. It is caused by the damaged parts of the brain sending conflicting signals to the muscles, causing them to contract. This inhibits the survivor’s ability to perform daily tasks, but can be solved temporarily with stretching exercises. A solution to compensate for these spastic forces using a passive-assist device was proposed at the start of this project. The project was divided into four stages: Analysis, Synthesis, Embodiment and Evaluation. During the Analysis stage, interviews with a Physiotherapist and stroke survivor and literature studies regarding anatomy, the state of the art and relevant technologies were used to create a framework for the design of a smart passive-assist glove. Looking at competing products, there is a demand for passive assist and Range of Motion assessment functionalities, yet a combination of these in a single device is not yet present in the market. During the Synthesis stage, the design problem of the passive assist device was split into three groups: Orthoses; the connections to the body, Passive Assist; the compensation medium, and RoM measurement; the sensing mechanism(s). These three groups were further split into sub-problems, the solutions to which were compiled into a Morphological Chart. By combining the solution within this chart, three promising concept designs were created: One upgrade to the existing sensor glove, one full integration of sensing and passive assist, and one passive assist glove with removeable sensors. To evaluate these concepts, eight criteria were established and weighted with the help of a physiotherapist. In order to create an objective assessment, the criteria were kept strictly quantitative and the three designs were first scored against the Raphael Smart Glove by Neofect using early prototypes. These scores were then used to evaluate the designs relative to each other, which resulted in an overall higher score for the concept with separable electronics. Making the sensor part of the brace removeable allowed the product to be used during daily life as well as physiotherpy exercises, and proved a key benefit in keeping the product clean. Based on the chosen design, four iterations of prototypes were made, which were tested with healthy subject. During this stage, it became clear that flex sensors are be best suited to create a range of motion assessment for spastic stroke patients, since it is less important to know how well they perform a task, and more important to know if they can actually perfrom it. Based on a quantified use case, the four sub-assemblies; the Wrist Wrap, Finger Modules and Sensor Module, and their connections were materialized in the Embodiment design stage. When selecting production methods, the main challenge was a small batch size of 1000 units, which made conventional techniques for mass production, such as Injection Molding, less attractive. This stage ended in an assesment of the product’s production price and durability: The product would cost €250 to make, and would last for 2.5 years before the Velcro connection on the Wrist Wrap would become too weak to sustain the spasticity forces. In the Evaluation stage, the product was evaluated on the seven most important requirements established during the analysis stage. For several of these, a user test was performed, again with healthy subject. While the Adjuvo Auxilius passed most theoretical requirements, the user tests on healthy subjects could not be used to draw any conclusions regarding its effectiveness on spastic stroke patients. However, since the product’s working principle is based on that of existing spasticity compensation products, the prediction is that the Auxilius will be an effective therapy supplement. The result of this project is the Adjuvo Auxilius; a spasticity-compensation glove with modular sensors, which can be added to allow virtual (stretching) exercises through the Adjuvo Motion’s platform. The results of these exercises are used to create a remote assessment of the patients motor skills, and to adjust the therapy if needed.