Radiographic findings in several joints of nine bears

Discussion
In the literature skeletal pathologies in captive bears are described. These observations were
made, without any exception, directly at necropsy or on skeletons in collections of museums
and in addition they were recorded in old adults. The patients of our study consisted of nine
captive bears with an age from 11 to 33 years and the examinations were performed under
general anesthesia.
Considerable problems arose during the radiographic examination. An important
factor was the security (flight tracks) of all involved people (technicians, veterinarians, animal
keepers, but also zoo visitors). In most instances we decided therefore to leave the bears
within the stable. Where possible, we moved them to the room in front of the stable. The
examination room was quite confined in almost every zoo. Under these conditions,
positioning of the animals, the cassette and the x-ray-tube was generally difficult. Some bears
weighted up to 280 kg and at least four strong men were necessary to move and elevate the
patients. The examinations were additionally hindered by the inhalation anesthesia and the
consideration of the radiation protection. We were not able to finish our examination protocol
in one case due to the unexpected early recovery of a patient anesthetized with an injection
protocol. Due to the limited number of phosphor storage plates sometimes we were forced to
read out some plates during the examination in a local human hospital. The limited
performance of mobile systems furthermore disabled acquiring hip joint radiographs in some
instances. And sometimes the wet wrap of bears created artifacts when it was raining.
A great number of secondary causes of osteoarthritis are discussed in the literature
such as trauma, metabolic disorder, immune-mediated arthritis or crystal induced arthritis. 15
One of them is “physiological” aging. Other factors are genetic predispositions (joint
dysplasia, osteochondrosis), captivity (characteristic of floor of the enclosure), nutrition and
infection. 15, 16 Degenerative joint disease are described in humans and a lot of mammals such
as horse and dog. 17, 18 The disease in these species may be primary or secondary to a
developmental or acquired disorder. The aetiopathogenesis, the specific locations and the
radiographic signs of this joint disease are quite well known.
16, 17, 18, 19
In our patientload we detected changes resembling to alterations described in other mammals.
In analogy to alterations found in horses for example, we detected a collapse of the small
tarsal bones 16 , changes in the strong part of the tarsus resembling to bone spavin 20 and
osteochondromatosis-like lesions in one stifle joint 21 . Other changes resembled to
radiographic findings in dogs. The type of radiographic changes in some stifle joints, for
example, are comparable to changes found in cranial cruciate ligament lesions and some
alterations in hip joints were similar to dogs with bilateral hip displasia and concurrent
coxarthrosis. 18, 22 The cuff-like type of lesion in two elbow joints, however, resembles to the
changes detected in cats suffering from a chronic hypervitaminosis A. 15 And comparable
enostotic lesions as detected in the tibia of one of the brown bears have been described in
horses and dogs (endostal reaction).
15, 16, 17
The nutrition can play a role at two levels in zoo bears. Large quantities of food can
induce an overweight and afterwards can cause osteoarthritic changes as described in other
animals. An inadequate food for bears, might influence the upset of skeletal disorders such as
it is described in osteochondrosis of dogs and pigs with possible consequent osteoarthritis. 18,
23
Polyarthritis is thought to be followed by osteoarthritic changes. In the literature
infectious and non-infectious causes are mentioned. Some authors 8, 10, 11 suggest that
osteoarthritis in bears and in felids could be caused by reactive arthritis, which is described in
humans as a sequale to infectious diarrhea due to Salmonella, Shigella, Yersinia,
Campylobacter or to transmitted infection (Chlamydia trachomatis). 24 This type of
polyarthritis is called Reiter’s Syndrome in human medicine. Many enthesiophytes were
visible on the radiographs of the tarsal and the stifle joints in our patientload, which have
comparable characteristic to Reiter’s syndrome. But a human being with the Reiter’s
syndrome shows often asymmetrical peripheral nonpurulent arthritis in more than five joints,
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