Comparison of Radiographs versus Computed Tomography for Evaluation of the Distal Limb in an Asian Elephant
Feet problems are the most commonly seen ailment in captive elephants. In the field of zoo and wildlife medicine, radiographs are the accepted standard of skeletal evaluation of the distal limb of elephants, to show changes in bone density and conformation.1 Although radiographs are considered reliable to show severe degenerative change in the distal phalanges, it is difficult to assess detail of the carpus and tarsus due to the anatomy and superimposition of the large carpal and tarsal bones.
Radiographic images of the distal limbs of a geriatric, female Asian elephant, were compared with postmortem computed tomography (CT) images. This animal had a long history of clinical nail disease treated for many years with diligent foot care and aggressive paring of multiple nails. Arthritis of the carpi, tarsi, and/or digits was suspected and had been treated with nonsteroidal anti-inflammatory medications. Serial radiographs from several years showed obvious degenerative change in multiple digits, especially those most severely affected clinically at the nail. Osseous detail in the carpi and tarsi was suboptimal on radiographs even when postmortem specimens were radiographed with a stationary, high-capacity radiograph machine designed for large animal radiology. CT images of the distal limbs revealed degenerative skeletal changes that were not readily apparent on radiographs. Most degenerative change was noted in the periosteal areas of the carpal and tarsal bones, particularly at articular surfaces.
Realizing that CT of feet and distal limbs of live elephants is impractical, if not impossible, this comparison of radiographs and CT demonstrates that radiographs may not reveal all abnormalities present in joints of the distal extremities. Comparative CT images of younger or clinically normal animals were not available, so it has not been possible to determine the clinical significance of the apparent degenerative changes noted on these radiographs and CT images at the time of this publication. Nonetheless, consideration should be given for the lack of detail when evaluating radiographs of elephant feet.
When radiographic changes are noted in the distal limbs of elephants suffering from arthritis with a history of nail disease, the attending veterinarian may consider prophylactic antibiotic therapy to treat possible osteomyelitis in the bones of the distal limb. Also, in animals with arthritic change on radiographs and no nail disease, implementation of appropriate anti-inflammatory drugs and/or joint supplements should be considered. Hydrotherapy, acupuncture, limb exercise, and other topical therapies may be warranted, depending on each individual case and the clinical signs exhibited. Routine and diagnostic radiographs should be taken from several angles, including oblique views, to assure the most accurate assessment of bony change in the distal limb and to give the best overall images for retrospective comparison. Radiographs should include the carpus and tarsus if the radiograph machine has the capacity for the bone density of that region.
Thanks to the State Veterinary Diagnostic Laboratory, Auburn University College of Veterinary Medicine Department of Radiology for all of their time, expertise, and contributions to this study. Also, thanks to Marcia Riedmiller and the pachyderm care staff at the Birmingham Zoo.
1. Fowler, M.E., and R.E. Miller. 2003. Zoo and Wild Animal Medicine, 5th Edition. St. Louis, MO: Elsevier Science. 547–548.