What is Osteomyelitis?
Osteomyelitis is an active infection of bone that causes severe inflammation, bone destruction, pain, and significant clinical lameness depending on which bone(s) is affected. It is most often caused by a bacterial infection, but can also be caused by fungal agents. There are many ways animals can develop osteomyelitis. A young animal may get it from a blood-born infection that settles in the growth plates of bones. Adult dogs and cats can get osteomyelitis when damaged bone gets exposed to bacteria or fungi. Some dogs with pneumonia will develop a concurrent bone infection.
Most patients present for exam with a history of lameness or generalized pain. They may appear very ill or act only slightly lethargic. Many will have a low-grade fever, but not always. During exam a painful focus is often identified on a limb or along the spine. The painful area may be swollen and tender to the touch. X-rays typically reveal a mixed destructive and proliferative bone response and swelling of surrounding soft tissue. This typical X-ray appearance may not be evident for up to two weeks after the onset of lameness. Blood cultures or direct lesion sampling are attempted to definitively identify the organism responsible for the infection.
The backbone of treatment is long-term antibiotic therapy, based on culture and sensitivity results (identification of the organism and determination of what kills it) and removal of any underlying causes such as foreign material. Patients are typically on the antibiotic(s) for a minimum of six weeks. In the case of a fungal infection, anti-fungal medications are utilized for much longer periods of time. In chronic and/or severe cases of osteomyelitis, surgical debridement (removal of dead tissue and inflammatory debris) may need to be performed so that the body can completely clear the infection. Infected surgical implants (bone plates, screws, pins) usually need to be removed in order to completely clear the infection. In general, prognosis for patients with osteomyelitis is fair to good if early measures are taken to definitively identify the offending organism and to aggressively treat the condition.