Diagnosing Osteomyelitis and Deep Tissue Injury

Initial Diagnostic Approach

The Infectious Diseases Society of America recommends beginning with plain radiographs of the affected foot to look for bony abnormalities, soft tissue gas, and radio-opaque foreign bodies 2
A probe-to-bone test can help diagnose or exclude osteomyelitis, especially in cases with high or low likelihood 2
Osteomyelitis should be considered as a potential complication of any infected, deep, or large foot ulcer, especially one that is chronic or overlies a bony prominence 2

Deep tissue injury presents with soft tissue swelling, effacement of fat planes, and possible fluid collections, according to the American College of Radiology 3
Radiographs may show only soft tissue swelling without bony changes in deep tissue injury 3
MRI shows soft tissue edema and enhancement without bone marrow signal abnormalities in deep tissue injury, as per the American College of Radiology 4
Osteomyelitis is characterized by periosteal reaction, focal bone lucency, and frank bone destruction on X-ray, although these findings may take 7-10 days to appear 5
MRI shows bone marrow edema, cortical disruption, and adjacent soft tissue inflammation in osteomyelitis, as recommended by the Infectious Diseases Society of America 4

MRI is the recommended imaging modality after initial radiographs when osteomyelitis is suspected, according to the Infectious Diseases Society of America and the American College of Radiology 2, 4
Negative MRI effectively rules out osteomyelitis, as defined by maintenance of intramedullary fat signal intensity and integrity of cortical signal 6
If MRI is unavailable or contraindicated, consider a leukocyte or antigranulocyte scan combined with a bone scan, as suggested by the Infectious Diseases Society of America 7

The most definitive way to diagnose osteomyelitis is through combined bone culture and histology, as recommended by the Infectious Diseases Society of America 7
Bone biopsy should be considered when diagnostic uncertainty exists, soft tissue cultures are inconclusive, or infection fails to respond to empirical antibiotic therapy, according to the Infectious Diseases Society of America 7

The Infectious Diseases Society of America recommends antibiotic therapy for 2-3 weeks for moderate to severe osteomyelitis infections 2
For deep tissue injury without bone involvement, shorter antibiotic courses may be sufficient, as suggested by the Infectious Diseases Society of America 2
Prolonged (≥4 weeks) antibiotic treatment is suggested when there is persistent infected or necrotic bone, according to the Infectious Diseases Society of America 7