Abstract

A 16-year-old male caiman lizard (Dracaena guianensis) presented with a focal swelling of the right hind proximal digit 1 (D1) and adjacent metatarsal joint. The lizard was otherwise eating and acting normally. Radiographs confirmed a soft tissue swelling with no obvious osteolysis. Fine-needle aspirate (FNA) found moderate numbers of gram-positive cocci. Treatment with systemic NSAIDs, antibiotics, and topical Epsom salt soaks was begun. Blood chemistry was normal, and CBC showed a mild azurophilia. Additional topical therapy and bandaging showed no improvement. Repeat FNA found moderate granulomatous inflammation, so the mass was surgically debulked. Histopathology revealed a low-grade sarcoma. The lizard was transported off-site for an MRI to delineate the margins of the neoplasia. The tumor surrounded D5 and part of D4 with a suspected track to the D1-metatarsal joint. Based on oncologist recommendations, aggressive surgical resection was pursued, and the foot was amputated proximal to the ankle joint. Recovery was uneventful. Histopathology confirmed a low-grade soft tissue sarcoma of unknown origin with clean surgical margins.

Since the amputation, the veterinary team has worked closely with personnel from the aquarium's Planning and Design (P&D) division to develop a prosthetic right foot. 3D printing technology is not new to the medical field, and more available, less expensive models are expanding their use worldwide.^1-4 First attempts were made by scanning 360-degree photographs of the remaining left hind foot and the stump, but the resulting reconstructed images were suboptimal. Next, a water-based alginate was used to make a mold of the left foot and stump. Using the mold, a cast was made out of rigid urethane plastic. The casting of the stump was used to tailor the fitting on the prosthetic. The cast of the intact left foot was digitally scanned with a MakerBot Digitizer Desktop 3D Scanner (MakerBot Industries, LLC, Brooklyn, NY). The digital image was mirrored with software to create a virtual right foot which was printed on a commercially available MakerBot Replicator 2 Desktop 3D Printer. The prototype was printed in grain-based plastic, and a mold was made and then cast in rigid plastic. Similar to the original cast, it was felt to be too heavy and brittle. More flexible materials were tried: urethane (Vyta-Flex, Smooth-On, Inc., Macungie, PA) and then silicone (Dragon Skin, Smooth-On, Inc.). The flexible, lighter silicone could also be tinted to improve realism. More rounds of molds and casting of the stump produced an attachment site inside the end of the silicone prosthetic that held onto the limb well without the need for additional attachment devices. The prosthesis is still being refined, with P&D staff working to make one that is even lighter and has a more natural angle to accommodate a wider range of motion. This case illustrates how improved tabletop 3D printing technology can be combined with the expertise and skill of innovative fabricators in the aquarium's P&D department and husbandry and veterinary teams to help improve mobility of a lizard amputee.

Acknowledgements

The authors want to acknowledge and sincerely thank the talented and caring staff of the Animal Health and Fishes Departments at Shedd Aquarium for their dedication to the highest standards of animal care and welfare. Special thanks to senior aquarist Jim Watson, primary keeper for the caiman lizard collection, and to the veterinary technicians, particularly Bernadette Maciol and Jennifer Fleming Jones. The authors also thank veterinary radiologist Dr. Hylton Gelb and veterinary internist/oncologist Dr. Rhonda Feinmehl at the Buffalo Grove Veterinary Specialty Center for their generous donation of resources and expertise.

* Presenting author

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