We are going to share with you a procedure for creating and manufacturing of a low-cost custom orthosis for children. The orthoses are devices used to correct or improve the positioning of limbs that have some deformity. We hope you enjoy the idea and that this work brings motivation to all Occupational Therapists (OT) and people who work in this area.
The team that developed this study works at NUFER (Nucleus of Additive Manufacturing and Tooling), which is a 3D printing laboratory of UTFPR (Technological Federal University of Paraná). The team has the support of an OT, teachers and Mechanical Engineering students.
One of the team’s objectives of study is the development of low-cost personalized orthoses for low-income children who have received an OT indication to use this kind of device.
The idea to start this study was based on the observation of available hand orthoses in the market. Often the options available are not the most appropriate to improve a clinical condition or don’t please the user.
The low availability of colors and finishes contribute to the abandonment of theses devices by people (specially children). Moreover, commercially available orthoses do not always fit properly into child’s anatomies by becoming too loose or too tight. This situation can generate discomfort, problems with excess perspiration, pain in specific points, difficulties in placement, among others.
In addition, improper orthosis can aggravate a person's state of health, especially for children, as they are in a rapid growth phase.
The following is a step-by-step guide on how to make a personalized orthosis for a child. Due to the complexity of this process involving therapeutic knowledge, all phases must be accompanied by an OT, especially in the decision regarding the orthosis model and correct posture of the wrist, hands and fingers.
To show the steps we will present a case study that was performed with an 11-year-old child. This girl has deformities in the upper limb due to Cerebral Palsy.
Step 1: Anatomy Acquiring
In this step we acquire the anatomy of the child’s limb that we wish to create an orthosis. Materials needed to perform this procedure are: 1 plaster bandage roll, 1 scissors, 1 container and water. The correct positioning must be done by OT.
Initially the plaster bandage should be cut into strips and folded to form a thick layer, in the measurements and in the model defined by the therapist. This must be moistened with water to be shaped into the child’s hand.
After applying, the time set by the manufacturer must be allowed for the plaster bandage to dry. The mold obtained should be saved for use in the next step.
Step 2: Scanning of the Plaster Bandage by Recap® Photo
This step consists of scanning the plaster bandage mold that was previously obtained. This procedure will allow us to pass the child's anatomy to a computer in a 3D model.
Thus, to perform this procedure you need 1 camera or 1 cell phone that has a camera with good resolution and 1 computer with Autodesk® Recap® Photo program.
The scanning technique is very simple: several photos of the mold must be taken, which should be placed on a table in a well-lit place.
To ensure that the scanning takes place correctly, some objects of known dimensions must be placed around the mold. This allows the determination of a scale factor and helps the program correctly capture the shapes of the mold.
For this study 45 photos were taken, which resulted in a proper mesh for the other steps. A very nice feature of the program is that, after uploading the photos, it notifies you via email when the 3D model is ready to be downloaded. Thus, a 3D file in the STL (stereolithography) format was generated with the mold geometry of the child's anatomy.
The file is small and can be quickly downloaded or sent by email.
Step 3: Orthosis Modeling by Meshmixer®
With the 3D model it is possible to start modeling the orthosis with Autodesk® Meshmixer® program, which is free and easy to use. It has so many tools that allow you to edit the mesh that came from the scanning step. The presence of an OT at this stage is extremely important to evaluate the development of the device.
Thus, in this step the correction of the format through 3D modeling is performed in order to form a smooth surface without holes and imperfections. Here you should use some cutting and smoothing tools to adjust the edges and locations where there were errors in the scan.
From the corrected surface an offset command is used which creates a surface identical to the original at a distance equivalent to the value of the thickness of the orthosis. In general, 3 millimeters is a sufficient value to ensure the rigidity of the orthosis. This procedure allows to create a solid that is the final orthosis with the anatomy of the child’s limb.
The figure shows the mesh obtained in the scanning stage (left side) and the orthosis already shaped (right side) from the scanned mesh.
Now we just need to customize the orthosis modeled according to the child's preferences.
Step 4: Orthosis Customization
One way to encourage the continued use of orthotics by children who need it, is by customizing the device according to their preferences. With so many geometries available, the child has the possibility to choose between different shapes (hearts, stars, soccer team symbols, among others) to stamp on their own orthosis. In addition, the child can choose the color of the printing material and the coating that will be applied to.
In the case study we are presenting, the child chose the pink color and asked us to put hearts shapes. The figure presents the virtual model of the orthosis already customized based on the child's choices. The hearts that the child requested have already been positioned in positions specified by OT to assist in the process of heat dissipation, thus avoiding excessive sweating of the limb.
This customization is only possible thanks to the ease of applying the tools found in the Meshmixer® program.
Step 5: 3D Printing of Orthosis
After modeling in the Meshmixer®, we were able to obtain a customized 3D model of the orthosis. Then you have to print the model using a 3D printer. Thus, at this stage the team chose to use the PLA as a printing material, because it presented a very low-cost. The color chosen by the child was pink, but it can be any color of the rainbow, this is why we decided to tell you a little about our daily work.
Thus, the 3D model of the orthosis created in STL format inside the program that manages the printer is inserted. This will build the GCODE format file with instructions so that the printer can build the modeled artwork.
The impression time of the orthosis for the child we presented in the case study was approximately 9 hours.
Step 6: Custom Orthosis Delivery
After the orthosis is completed, it should be evaluated by the OT that followed the whole development process of this device. After approval, the child began to use the customized orthosis, that until today has its performance evaluated.
With the printed orthosis, the finishing was done in the device, adding comfort items like EVA, Velcro (that helps in the fixation), among others.
Now it’s time to deliver the personalized orthosis to our child! She was very satisfied and liked the result very much. The user identified herself with the colors and was glad with the heart shapes! We hope you enjoyed the result, and that serves as a motivation to create better products and bring happiness to people!
Thank you so much!