Orthopedic cast design requirements:
Following our research, we decided to single the type of design we wanted to use for our project. Although many 3D printed casts are available on the market, we decided to focus on the short-arm orthopedic cast due to its common usage and rather simple design (in comparison to other designs). We decided to work on a scale version of the orthopedic cast which we would later scale to a larger size. We also wanted to use a material which is biocompatible for surface contact with the tissue of the arm, and prevent any irritation. We also believe that post-processing will be required to smooth prints, improve product appearance, and improve patient comfort.
Transitioning from Sketches to CAD:
The design of 3D printed short arm casts tend to be complex. This is due to a few reasons: the need for a breathable cast in order to maintain hygiene, lower amounts of materials, and providing enough rigidity so that the patient’s arm is kept in place while withstanding external forces. Given the complexity of design, this posed a significant barrier to our design process. We needed to create a method to test and produce these complex designs. Given that all of the 3d printed orthopedic casts that we have seen on the market incorporate a lattice structure, we are going to analyze design variations and determine an ideal design for printing and presentation. We began our modeling by utilizing an online 3D anatomical model of an arm which extended from the elbow to the fingertips.
The cast is to be placed between the proximal third of the forearm and the distal palmar crease, allowing for the forearm to be immobilized while the surrounding joints maintain a full range of motion.
Initial Design:
For our initial design we attempted to develop a cast similar to many of the 3D printed orthopedic casts on the market. Many of these designs consist of a cast that features a lattice structure, so we wanted to discover just how exactly we could develop such a design for our cast. Initially we attempted making casts from scratch, but after a while, we found this process to be too complicated and realized it did not make sense if we intended to analyze several design iterations. After quite a bit of trial and error, we discovered that it was best to create a duplicate object from the model of the arm, offset it a few millimeters away from the arm model, remove sections of this object so that it resembles a cast, then use a shape optimization feature. With our resulting design being shown below:
This process is much quicker and reproducible than individually designing each cast, and allows for individualized casts to be made much more efficiently.
Next Steps:
Unfortunately, given the complexity of design, we have had issues in 3D printing our cast since our last update. The largest setbacks revolved around determining our design and how to reliably produce casts at a personalized level; however, since we have recently overcome these setbacks, we now intend to begin performing analysis and printing scale models of our casts and eventually move on to a full-scale model. There will be a few challenges during this phase: as all 3D printed orthopedic casts are printed in multiple components and joined together by some sort of ligature, we need to determine how our cast will be sectioned and joined together in order to meet required specifications.