High School CTS: 3D-Printed Bone Replacements

The high school-level “project” courses are ones that exist within the curriculum to add flexibility to the CTS courses to allow for additional projects of interest that aren’t already present within the curriculum. I designed a DES2190 course (intermediate-level design) where students have to design and print bones and bone segments with the intent of surgical bone-replacement. Very few schools in the world would have the necessary technology to design implant-worthy 3D prints of course, so the focus of this course is the design and printing of the bones rather than the use of them as actual medical tools.

The full Word document with curriculum connections and activity design can be downloaded right here for you to access and modify as needed: High School CTS: Bone Replacements

You can also find the activity and the models that I built here on Thingiverse.

Real-Life Connections: The concept here is that 3D printers are already being used in the medical profession for many purposes, so getting high school students who are interested in medical technologies as a career path some experience with 3D design and printers could be a fantastic career-connection.

Here’s a link to the article that was the inspiration for this course: 3D Printed Bone Transplants

Bones aren’t the only things being printed to replace human tissue either. Many organs, both external and internal are able to be printed with various plastics and even stem cells. The process for this is quite different than what happens with a “traditional” 3D printer, but the ideas are the same.

Design Programs: This course would require the use of more advanced mesh-modeling programs such as Blender or ZBrush. I would also encourage my students to give 123D Catch a shot, although I’ve had limited success with it myself. Beginner-level programs such as 123D Design and 3D Slash would not be appropriate here. Similarly-advanced computers would also be required, as some models may require much more processing power as the number of faces of the model increase.

Results: The very first part of the course I designed so that the students themselves have to go do internet research on the processes of 3D printing and bone transplants in medicine. One of the things that they should find is that bone replacements don’t always need to match the original bones exactly, but this depends at least partially on which bones are being replaced and the muscles, tendons, and other tissues that are attached to them. Some replacements, as seen below, do not look like the original bones at all.

As a result of this, not all of the replacements developed by the students in the course will look like “bones,” although as I will say again below, I recommend that at least one of the finished models be done in this fashion.

I used Blender to design the upper portion of a femur by taking photos of a model femur and using the sculpting features of Blender to shape and texture the model. By no means would I call this particular piece an exemplar, but I will keep working on the process to try and make a better final product as a demonstration.

Assessment: In the project document, I outline my grading criteria based on the reports the students research and write, as well as the models of the bones that they produce in relation to their references.

My Recommendations: There is a lot to talk about here. First off, it took me a while to figure out a “good” way to sculpt a bone as difficult as the top of the femur. In the end, I went with taking reference photos of a model at different angles and sculpting them in Blender. One of the problems that I encountered there was the difficulty in keeping exactly 90° angle differences in the reference photos’ perspectives. This led to some dissimilarities between the model and the reference image. Students may need to come up with a technical solution on the best way to get reference photos.

References are important here, so I would recommend making use of a full human skeleton model, which many biology departments will have access to. Having that physical reference will always be better than mere photos off the internet.

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The reason that I require my students to show progress pictures is because there are many skeletal models available online for free and for money, so to limit the possibility of plagiarism, having students document their work is useful.

Although my experience with ZBrush is limited, I would probably posit the theory that ZBrush would be better suited to the task of sculpting an organic-looking bone than Blender is.

I also tried many times to capture a good model of the reference bone using 123D Catch, although I have very limited success there, possibly because of the lighting I was using, but also possibly because it was a difficult shape to capture. I would encourage any and all of my students to try something similar though, or if not with 123D catch then with an alternative like ReconstructMe.

I would highly recommend that any teacher who wants to implement this course try their hand first at creating the models themselves to familiarize themselves with the programs being used, as well as the challenges your students will face. Their reflections in their final reports and the plans for their designs in their introductory reports will be much more meaningful to a teacher who has dealt with the same struggles and better feedback and scaffolding can be provided from that position of experience.

Overall, this will be a difficult course for the students. My recommendation is to have them work on different types of implant designs as well as to try them all from different approaches and software, not just sculpting them all in Blender (for example).

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