Osteomyelitis
Bone infections in patients with diabetes are a major concern and can lead to amputation of digits or lower limb amputation. Early clinical diagnosis of osteomyelitis is imperative in order to minimise the risk of amputation and approximately 80% of cases can be successfully treated with appropriate antibiotics, commenced without delay. The gold standard for diagnosis of osteomyelitis is MRI imaging but this is usually not available for initial imaging.
Typically, the first indicator of bone infection is the need for repeated courses of antibiotics for an ulcer infection, when initial therapy has only improved the soft tissue infection. In digital osteomyelitis, the toe may take on a swollen ‘hot sausage’ appearance, although a fracture or inflammatory arthropathies should also be considered.
Wound probing down to bone demonstrates an increased likelihood of osteomyelitis. Bone probing is not a definitive test because there is evidence that up to half of all ulcers that probe to bone do not exhibit osteomyelitis. A positive bone probe test should direct the clinician to undertake imaging, usually a plain x-ray in the first instance.
If imaging suggests bone infection then appropriate treatment should be instigated as directed by the osteomyelitis pathway (link). If the x-ray is unable to rule out osteomyelitis then a repeat x-ray should be performed two weeks later because radiographic evidence can take time to develop from the point of initial infection.
Microbiological samples should be obtained to help guide antibiotic therapy, with bone biopsy the preferred choice. Depending on the clinical setting, deep swabs, wound biopsy or loose fragmented bone (sequestrum) are alternative culture sources.
A comprehensive clinical history should always be provided to help guide the microbiological assessment. Extracted bone may be available from surgical procedures and should also be sent for microbiological culture.
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