An ISE research team were recently contacted about fabricating a custom brace for a Green sea turtle, named Augie, with an open fracture sustained to the right radius and ulna with a large wound on the ventral aspect. The fracture was continuous with partially healed lacerations of the skin. The turtle was found by members of the public off Carrot Island and turned over to the Coast Guard.
The injury to the right front flipper was severe, but the entire flipper appeared to have viable blood flow and nervous function, making salvage of the limb a good possibility. Surgical stabilization of the fractures may have be an option but traditional reduction did not appear to be a practical solution, so the team accepted this challenge as a unique opportunity to apply additive manufacturing techniques due to the irregular shape of the flipper as well as the urgent nature of the case. The team received CT scans of Augie which included both the broken and intact front flippers. The team reconstructed these scans into 3D models using Mimics software.
The distorted geometry of the injured flipper prevented us from directly designing the brace, so our first approach was to design the brace off of the contralateral (intact) limb. After isolating the intact flipper in the model, the team created a mirror model to use as a basis for the shape and placement of the brace. This model was imported into SolidWorks in order to begin the development of the brace.
Using the flipper surface as a guide, a solid surface was created which followed the contours of the limb. After creating the surface, a “mold” of the flipper was made which served as the foundation of the brace. This rough mold was further refined to include hinges and locking mechanisms to hold it in place while on the turtle. After several iterations, The team was able to devise a hinge and clamp system that better suited Augie’s needs and brace alike. In addition, the surface and shape of the brace had to be smoothed and altered slightly so that a better fit could be achieved which was easily done in ClayTools.
The team also printed a model of the broken flipper so that they could test out the brace to check the fit, placement of the wound opening, and structural aspects of brace using our Objet Connex 350. The soft tissues were priinted with the tango black (rubber like) material while the bones were printed using the vero-white (hard plastic) material.
Unfortunately their initial assumptions regarding the symmetry of the contralateral limb turned out to be incorrect. Based on the connex models, the team determined that an entirely new approach was required. new clearGoing back to the original CT scan/stl model they loaded the file into a software called Clay tools, this uses a haptic interface so that they can “feel” the stl model in the computer, using this approach they were able to 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. Rather tan design a complex latching system, the rear connection is designed to be sutured together making it relatively easy to don and doff with readily available resources.
After a couple of iterations the team was able to fabricate a brace that fit the patient very well. The final design was based off the surface model of the “virtually” reduced fracture and globally enlarged by 3%. So far the device is fitting well and Augie is the doing well (eating and swimming).