A team of ISE researchers work to solve a complex engineering problem to save the life of an endangered sea turtle.
Sea turtles have been swimming the world’s oceans for more than 100 million years. However, their very existence is now in jeopardy from human threats that are proving to be too much for sea turtle populations to handle. Each of the six sea turtle species found in US waters is listed as either endangered or threatened under the Endangered Species Act which means that they may go extinct in the foreseeable future. So when the ISE department was contacted by Christian Legner, curator at the NC Aquarium at Roanoke Island, for help, they knew they had to act.
A sea turtle, now named Augie, was found by tourists on the beach at Carrot Island, NC and turned over to the Coast Guard. Augie eventually found his way to the NC Aquarium at Roanoke Island and in the care of the aquarium staff and the Network for Endangered Sea Turtles (NEST). It had suffered an open fracture to its right front flipper. The good news was that the entire flipper appeared to have viable blood flow and nerve function, making salvage of the limb a good possibility. Due to the irregular shape of the flipper as well as the urgent nature of the case, traditional fracture reduction methods did not appear to offer a practical solution. So a team of ISE staff and students including Tim Horn, Ron Aman, and Austin Isaacs teamed with veterinarian Denis Marcellin-Little, and realized this was an opportunity to apply cutting edge additive manufacturing techniques to solve this challenging problem.
The team received the initial CT scans of Augie from the team at Albemarle Hospital (Janet Jarrett, executive director; Dr. Kenneth Peat, radiologist; and Dr. Emily Christiansen, zoological medicine resident) which included both the broken and intact front flippers. The CT scans where then reconstructed into highly accurate 3D models of Augie’s anatomy with the use of biomedical software (Mimics) that was specifically designed for medical image processing. After viewing the completed 3D models, the solution became clear; build a custom fit external brace to support Augie’s injured flipper.
“The first challenge we faced was overcoming the distorted position of the injured flipper which prevented us from designing the brace based on the anatomy of the injured flipper.” said Tim Horn, ISE research associate. The team’s first approach was to design the brace using the intact limb. After isolating the intact flipper in the model, they created a mirror model to use as a basis for the shape and placement of the brace. This model was imported into a 3D design and simulation software known as SolidWorks to begin the development of the brace.
Using the intact flipper’s surface as a guide, a solid surface was created which followed the contours of the limb. Once the outside surface was determined, a “mold” of the flipper was made which served as the foundation of the brace. The team further refined the mold to include hinges and locking mechanisms to hold it in place while attached to Augie. After several iterations, they devised a hinge and clamp system that better suited Augie’s needs and brace alike. Also included in this latest brace was a smoother, more accurate shape to better fit Augie’s flipper.
Now it was on to the testing phase of the project. The team needed to create a model of the broken flipper so that they could test out the fit of the brace, the placement of the wound opening and structural aspects of brace. They needed a model that closely represented both the soft tissues and bones of the injured limb. Fortunately, the ISE department is one of a handful of facilities in the country that has a multiple material 3D printer. They were able to 3D print a flipper model that used a black rubber like material for the soft tissue and a white hard plastic material for the bones. The team was now ready to put their solution to the test. Little did they know that their greatest challenge lie ahead.
Unfortunately the team quickly discovered that their initial assumptions regarding the symmetry between the intact and injured limbs turned out to be incorrect and the brace did not fit. What were they going to do? The brace had to fit exactly and stay on Augie during the recovery period but the geometry of the injured limb didn’t allow for accurate measurements. The team needed to be able to return the broken limb back to its original position and shape. But how? That is when the team discovered that by loading the original CT scan into a program called ClayTools, sculptural modeling software used to design fine art and jewelry, they were able to recreate the injured flipper and then virtually reduce the fracture and repair the anatomic distortions present in the scan. “This allowed us to build a much more accurate and refined brace.” said Ron Aman, ISE research associate. Another design enhancement was to replace the complex rear connection with a simplified suture system making it relatively easy to attach and remove with readily available resources.
After a couple of iterations they were able to fabricate a brace that fit the patient very well. “We are happy to report that the turtle has returned to normal eating and swimming habits and we are looking forward to hearing more about the turtle’s progress.” said Austin Isaacs, ISE grad student.
To watch Augie swimming around with his new brace, click on our Augie the Turtle video.