With this 3D printed rehabilitation orthosis, a disabled man can perform physical activities. The prototype of the device was manufactured on ZMorph multitool 3D printer.
[UPDATE: Source files are now available for free download from Instructables]
Medical 3D printing has many applications in various fields. In orthotics, industrial 3D printers are used to manufacture custom-sized orthoses, braces as well as prosthesis and parts for powered exoskeletons. First two helps patients with broken bones while the latter are used for amputees. There’s still a lot of untapped potential for helping the patients with cases of mild and partial paresis who need lighter and more comfortable 3D printed rehabilitation orthosis which won’t harm their existing but weak extremities.
Eliza Wrobel faced this problem during her Biomedical Engineering studies under Bogdan Dybala, PhD. Eng. at the Faculty of Mechanical Engineering of the Wroclaw University of Technology. She was asked for help by a 33 years old man suffering from tetraplegia (the limb paresis) after being in an accident a few years back. He needed a light, yet durable orthosis that could help him grab objects during the rehabilitation and other physical activities as he couldn’t hold even the lightest dumbbells. In order to play his favorite table tennis, someone had to tie a paddle to his hand which wasn’t too comfortable.
Answering the Needs
The 3D printed rehabilitation orthosis had to answer the patient’s needs which meant that Eliza has had to reverse engineer it. She started with making a plaster cast of the patient’s hand which was later filled with liquid ceramic mass and supported by a metal bar inside, so the model itself was easier to hold. After 24 hours, the hand’s model was grinded and then 3D scanned using the ATOS II machine available at the Wroclaw University of Technology.
With a 3D model of the patient’s right hand ready, the actual designing of the orthosis have started. In CAD software Eliza tried different mechanical solutions for the rehabilitation device. The biggest challenge was to bring together both the device and the flesh. Solutions used in prosthetics could harm the man’s tissues while standard orthosis used for broken bones would keep his hand in only one setting – open or clenched.
The answer was found somewhere in between. The husk of the orthosis had to be closely fitted to the wrist, while the fingers were supported by smaller parts imitating their joint-structure – 2 joints for the thumb and 3 joints in every other finger. To connect these parts into a working device, Eliza added a series of lever mechanisms controlled by one big lever at the top of the husk. Pressing the main lever accelerated the hand grip while pulling it away returned the fingers to their rest state.
3D Printing of the Design
The design of the rehabilitation orthosis consisted of over 70 different parts. They were all exported as STL files, checked for any shortcomings in Netfabb Basic and then imported to the Voxelizer software in order to prepare them for 3D printing. The parts for the orthosis were later 3D printed on ZMorph multitool 3D printer with single head extruder 1.75 mm using ABS filaments of different colors.
ZMorph’s precision and the quality of the prints allowed Eliza to minimize the number of non-printable parts in her device. Small 3D printed pins were used to connect the smaller leverages and finger casings to each other while the main lever was connected with the husk with a 3D printed latches. Velcro strap was added later in order to fasten the orthosis around patient’s hand.
What’s Next for This 3D Printed Rehabilitation Orthosis?
With the help of ZMorph multitool 3D printer, Eliza was able to quickly fabricate, improve and finalize a working prototype of her design. The desktop machine proved to be a quick, reliable and inexpensive alternative to outsourcing prototyping services based on industrial 3D printers. Thanks to the durability of ABS-based 3D parts printed on the ZMorph, the prototype can be used in a limited capacity by the patient during his physical activities.
Further works on this student’s idea could soon result in a wide production of custom-made 3D printed rehabilitation orthosis for patients with a hand paresis and thus significantly improve their everyday life.