CUSTOM ORTHOSIS DESIGN FOR FES
BACKGROUND
Individuals who have suffered from a stroke and display chronic hemiparesis often exhibit flexion synergies at the elbow, wrist, and fingers that directly increase with shoulder torque. Understandably, this reduces their ability to perform activities of daily living (ADLs) such as lifting up a carton of milk to pour a glass for themselves and then put the milk carton back in the fridge. The Neuro-interfaces lab subsection of the Dewald Lab researches the utilization of Functional Electrical Stimulation (FES) to overcome flexion synergies with the goal of improving an individual with chronic hemiparetic stroke's ability to perform ADLs. The goal of this project was to create a custom fit, home-use orthosis that was embedded with EMG electrodes that were placed on certain muscles to detect the individual's hand opening intention as well as stimulating electrodes to execute the FES procedure to open the hand.
DESIGN CONSIDERATIONS
The orthosis needed to be custom fit to each individuals arm and have space for embedded electrodes at pre-determined locations for each participant. This is a key point because, as the device is eventually intended to be used at home, there will not be trained professionals to aid the participant in finding the correct EMG placement locations for themselves. With this in mind, we decided that taking a 3D scan of the arm and then modifying the resulting image would be a good place to start, but this decision in itself led to several important questions:
Which 3D scanner would give us the level of resolution that we needed?
How can we overcome scanning difficulties resulting from the participants inability to keep their wrist in a neutral position?
How can we process the resulting model into a file that can be 3D printed?
What material should the orthosis be printed in such that it would be comfortable, slightly flexible, but also very durable?
How can we minimize the cost of the printed orthosis (including time spent editing the mesh resulting from the scan), and utilize the materials that we have in the lab as much as possible?
3D SCANNING PROCEDURE
We are currently writing up our methods to be submitted for a journal. I will post a link to the methods list when it's published!
SUCCESS!
I was successfully able to develop a procedure and some scanning tools that allow us to quickly and easily get an accurate scan of the patient. Additionally, I found ways to speed up the process of editing the mesh in Rhino, creating the orthosis from that mesh, and sending it to the printer.
Currently, orthoses are being developed for several participants in an ongoing study of improvements in ability to perform ADLs through the use of FES.