According to ENT surgeons Dr’s. Carolyn Jenks and Conor Devine, mastering knowledge of complex ear anatomy and related surgical skills can be difficult for trainees. Currently, medical students and residents have a limited selection of tools to study from.
Advances in 3D printing and medical imaging have made it possible to replicate microscopic anatomy with life-like materials. Over the course of four months, our team developed a realistic 3D model of the middle ear to be used with otoendoscopes for anatomic and surgical training. Dr. Jenks and Dr. Devine were content specialists who validated the accuracy of the model, I designed and created the model by digital sculpting, and Elizabeth Silvestro in the CHAMP 3D Printing Lab was our printing engineer.
First, the engineer and ENT surgeons generated a 3D model of the middle ear and ear canal from a CT scan of a pediatric temporal bone. The resulting model was very low resolution, like a pixelated photograph. I used digital modeling programs, Pixologic Zbrush and Cinema 4D r21, to add resolution to the model, but in some cases, it was required to sculpt the structures from scratch. This part of the process took about 2 months.
Above: Low resolution model. The original 3D model generated from CT segmentation. Viewed in Cinema 4D.
Above: The modeling process. New anatomical structures were created from scratch using a trace and extrude technique. Finer details were digitally sculpted after this step.
Next, Elizabeth printed the model on a Stratasys J750 printer and the support material (a soft filler to support the plastic structures) was dissolved and cleaned away by Dr. Jenks. She compared the tedious process to actual surgery, remarking how it required hours in the OR to remove the material with surgical instruments.
After three iterative prototypes, we had our final model. The resulting model is life-sized, anatomically accurate, and allow for color-coded identification of all relevant bones, nerves, tendons, and landmarks in the middle ear using straight and angled endoscopes.
Illustrations of middle ear anatomy are good study tools, in fact, my colleague Eo has made some fantastic ones for a surgical atlas (pictured below). Though illustrations have a limited ability to represent 3D spatial relationships in the round. Computer models can show the anatomy in 3D in animation or interactively (allowing a learner to rotate and zoom into the model). When I was taking Anatomy in grad school, I found this animation created by Brandon Pletsch to be really helpful! For examples of interactive models, search www.sketchfab.com, where you’ll find awesome models like this one from the Medical College of Georgia.
Animation by Brandon Pletsch
Illustration by Eo Trueblood, Stream Studios.
Interactive model by Medical College of Georgia
These are all fantastic learning tools, but they don’t give the trainee experience holding the otoendoscope at different angles, and viewing the anatomy the way they would in the OR-- rotated 90 degrees because the patient is lying down, not upright. Cadaveric specimens allow practice with the otoendoscope, but specimens are expensive and not always available.
We are excited to see how medical trainees like using the 3D printed skill trainer. The world of 3D printed learning tools is still in its early stages. We are still figuring out how to evaluate their educational impact, but preliminary testing is promising.
Thanks for reading!
Brittany Bennett, MA