Abstract

An adult male American bullfrog (Rana catesbeiana) presented to the Animal Health Department for evaluation of left hind limb lameness. The frog was wild caught one month prior along with another male and a female of the same species. All animals were housed in an isolated quarantine system with re-circulating de-chlorinated fresh water, supplemental UV lighting, and were fed vitamin and mineral supplement loaded crickets daily. Natural rock was used to provide basking sites and half sections of PVC pipe were made available to provide individual hiding areas. Shortly after acquisition the frog in this case developed an ulcerative dermatitis of the right tympanic membrane. Cytology and microbiology were diagnostically unrewarding. The animal was treated with itraconazole baths and topical recombinant platelet derived epithelial growth factor. Despite treatment the lesions progressed to a perforation of the right tympanic membrane and treatment was changed to topical gentamycin sulfate drops. An excellent response was observed and the tympanic membrane was completely healed when the animal presented with the left hind limb lameness. On presentation the frog was bright, alert and responsive. Appetite and enclosure behaviors were reported as normal. There was a mature cicatrix at the previous tympanic perforation site. The left hind limb extensor and flexor muscle groups were markedly atrophic and the stifle joint was unstable. At rest, in flexion, the limb distal to the stifle showed a marked valgus deviation. There was also an angular deformity to the distal interphalangeal joint of digit three of the right forelimb. No other abnormal findings were detected on physical examination. Radiographs confirmed the angular deformities noted on physical examination and demonstrated a significant displacement of the tibia-fibula at the stifle joint. The frog was anesthetized with a topical isoflurane, water, sterile lubricant mixture followed by MS-222 immersion. Maintenance was with recirculation of MS-222 in fresh water over the skin. The animal was placed in dorsal recumbency and the left hind limb aseptically prepared for surgery. A 1/2ö sterile Penrose drain was wrapped under pressure from distal to proximal on the limb to the hip and removed after placing a Penrose tourniquet at the hip. A curvilinear skin incision was made over the anteriomedial aspect of the stifle joint and two 3-0 nylon sutures placed to stabilize the joint. One was placed from the soft tissue surrounding the anteriolateral aspect of the distal femur to the posteriomedial aspect of the proximal tibia-fibula and the other from the anteriomedial aspect of the distal femur to the posteriolateral aspect of the proximal tibia-fibula. Interoperative stability and range-of-motion were excellent after suture placement. The skin was closed in a single layer with 5-0 nylon in a Ford interlocking pattern. Recovery from anesthesia was uneventful. Skin sutures were removed at 2 weeks. Following surgery the animal continued to demonstrate normal appetite and enclosure behaviors, the musculature of the left hind limb returned to normal, and the limb returned to full function. At the time of writing the animal is on display and indistinguishable from the other cohorts. Orthopedic clinical procedures in amphibians are uncommon. The presumed injury reported here is consistent with the unhappy triad of O'Donohue as reported in human medicine. That is, avulsion of the medial collateral ligament, tear of the anterior cruciate ligament and damage to the medial meniscus. Although these structures and injury cannot be confirmed in the frog of this case it demonstrates the ability to perform orthopedic procedures on amphibians and reinforces that all aquarium animals should receive the full benefits of in-house medical facilities and care programs.

Acknowledgements

The authors thank Drs. Jeff Boehm and Caryn Poll along with the Animal Health Department technicians for professional assistance in this case.