An alligator's dream come true: how Artec Eva helped give Mr. Stubbs a new tail

24/12/2018

When Arizona police pulled over a suspicious truck, the last thing they expected to find was 32 alligators slithering around inside.

As soon as officers realized that they were literally "up to their elbows in alligators," they called in the Phoenix Herpetological Society for help. The homeless gators, including Mr. Stubbs, were handed over to the Society, which currently houses 1,500 reptiles.

One of those gators would soon be given the name, "Mr. Stubbs," because he was missing his tail.

Not having a tail is no laughing matter for an alligator. Credit: STAX3D

Not having a tail is no laughing matter for an alligator. It meant that besides not being able to swim in deep water (he could easily drown), he also had real trouble at mealtime.

The other alligators around him were faster at catching prey, because gators use their tails for lunging and attacking. What this meant for Mr. Stubbs is that unless some hapless creature plopped down in front of his hungry jaws, he probably wasn't going to get the fattest piece of rabbit pie that day. If any.

His swimming problems were partly solved when they taught him how to dog paddle using his front legs. Not ideal, but at least he wasn't flipping over onto his back and drowning.

Russ Johnson, president of the Phoenix Herpetological Society, wanted to do more for Mr. Stubbs. He had an idea.

Dr. Marc Jokofsky and his assistant Sarah Jarvis from the Center for Orthopedic Research and Education were called in, bringing with them their experience in helping humans with orthopedic challenges. A team of specialists was assembled and they considered their options for creating a prosthetic tail.

3d-model of a future tail for Mr. Stubbs. Credit: STAX3D

Dr. Justin Georgi, Assistant Professor of Anatomy at Arizona’s Midwestern University, who had been studying the movement of alligators and other reptiles for years, offered his help with analyzing Mr. Stubbs, to see how best to fit him with a new tail.

By using some alligator specimens of various sizes from his lab as references, Dr. Georgi and Samanta Arroyos, a lab intern from the Phoenix Union Bioscience High School, together with Dr. Jokofsky and his team, calculated the right size, weight, and density of tail for Mr. Stubbs, one that would be balanced in proportion to the rest of his body, and evenly distributed.

Once they had these measurements, Dr. Georgi selected one of the specimens from his lab to be the model for the new tail. When it came to the actual prosthesis design, Georgi consulted with Dr. Jacofsky and the team from The CORE Institute.

“Without his tail, Mr. Stubbs can barely swim and only walk very poorly,” Georgi said. “His terrestrial posture and gait are so poor there was a real concern about his long-term joint and bone health.”

Dr. Georgi had previously tried to make scans of an alligator's tail using a laser 3D scanner, but the scan quality was too poor for capturing enough detail, so he contacted Artec 3D’s reseller STAX3D to see if they wanted to team up on making a new tail for Mr. Stubbs.

Preparation for scanning the alligator. Credit: STAX3D

Michael Andrew at STAX3D said, “When Justin initially contacted us, we were very intrigued and weren’t sure what we were getting ourselves into.” STAX3D had previous experience with making prostheses with Artec scanners, but only for humans.

Once onsite, Stax3D used an Artec Eva to make a hi-res, 3D model of the “cast tail” of a recently deceased, similarly-sized alligator (Georgi and his team had used the same tail as a model for making earlier prostheses). The Artec Eva 3D scanner works by beaming a pattern of light down onto the surface of the object, and when it bounces back to the scanner, the now-distorted light is instantaneously analyzed by the Artec Studio software and the object's shape is identified and recorded in high resolution at up to 16 frames/second.

Stax 3D processed the resulting data in Artec Studio, modifying the 3D model, fixing a few flaws, and adjusting the size and fit, so it would match perfectly with what little was remaining of Mr. Stubbs' tail. They export the file as an STL and from this the 3D-printed tail was made.

Artec Eva was perfect for this project because of its powerful resolution: being able to capture details as tiny as .5mm in size, yet it can also be used on large objects, such as a king-sized alligator's tail, or something even bigger.

“We were amazed at the speed and quality of the Artec scanner compared to our initial attempt,” Dr. Georgi said.

Artec Eva was perfect for this project because of its powerful resolution. Credit: STAX3D

When they realized the tremendous level of control they had to view and modify the digital model, Georgi and his team were beyond pleased. “The fine control over details of the size and shape of the tail that we achieve with the digital process gives us the chance to actually experiment with different properties so that we can understand on a more direct level how the prosthesis affects Mr. Stubbs,” he said.

After 3D printing the custom model, the researchers created a silicone cast of it, and from that, several prosthetic tails were custom made for Mr. Stubbs.

Now, every time they strap one on him, he acts so natural, as if it's always been there. He doesn't show signs of stress or discomfort while wearing it, proof that it must feel natural to him.

Now, every time they strap one on him, he acts so natural, as if it's always been there. Credit: STAX3D

Mr. Stubbs has been unlearning his old limitations, and acting more and more like a normal alligator. He's out there swimming and diving and lunging after his meals just like the rest of his cold-blooded neighbors.

Over the next 50-60 years of his life, as he grows larger (adult alligators can be up to 20 feet long), Mr. Stubbs will need to be fitted with as many as 40 new tails. Now that they have their 3D model, making modifications to it and printing new tails will be a snap.

Russ Johnson, president of the Phoenix Herpetological Society, told the Arizona Republic newspaper, “He is going to have a long and happy life here.”

The CORE Institute donated all their work and materials for this special project. Dragon Skin® was used for covering the prosthesis. This very special material is a lightweight, flexible silicone, commonly used in creating special effects and animatronics in movies, as well as with prosthetics.

The 3d-model of the tail in Sketchfab

This is certainly a leap in progress along the avenue of alligator prosthetics, but 3D scanning and printing are making even greater headway in the field of human prosthetics. “This isn't the future; this is now,” Andrew said. “Using this technology, companies and individuals are leveraging this technology to break down the limitations of previous manufacturing methods for prostheses. With this technology, you can cut out quite a few steps and a lot of time.”

Everyone involved hopes that Mr. Stubbs’ new tail will draw increased attention to this dynamic sphere. “We’re just scratching the surface of what 3D scanning and printing can do in the field of prosthetics,” Dr. Georgi concluded. “I think perhaps the most important thing Mr. Stubbs’ case can do is capture the imagination of others and inspire them to push these boundaries even further.”