Osteomyelitis Diagnostic Approach

Initial Evaluation

The American College of Radiology recommends plain radiographs as the first imaging test for all patients with suspected osteomyelitis, followed by MRI with contrast if radiographs are negative or inconclusive and clinical suspicion remains high 1, 2
Perform a thorough medical and neurologic examination to identify potential sources of hematogenous seeding and assess motor/sensory function 1

Obtain ESR and CRP as first-line laboratory tests, and consider procalcitonin when clinical examination is diagnostically equivocal 1, 2
Obtain two sets of aerobic and anaerobic blood cultures before starting antibiotics 1

Plain radiographs have limited sensitivity in early disease and may be normal for weeks after symptom onset, with radiographic findings including bone sclerosis, areas of destruction, periosteal reaction, and trabecular coarsening 1, 2, 3
MRI with contrast is the gold standard with 97% sensitivity, 93% specificity, and 94% accuracy, and is superior for detecting soft tissue involvement, abscesses, fistulae, and extent of bone involvement 1, 2, 3
A normal marrow signal on MRI reliably excludes infection with 100% negative predictive value 1

Obtain bone samples for culture, either intraoperatively or percutaneously, for definitive diagnosis, with intraoperative excisional biopsy during debridement preferred over core needle biopsy 1, 2
Bone cultures have 76-100% sensitivity but only 8-67% specificity, and combining with histopathology is recommended 2

For children <5 years with suspected extremity osteomyelitis or septic arthritis, ultrasound, radiography, or MRI with contrast are all appropriate initial imaging options, according to the American College of Radiology 4
Ultrasound can detect joint effusions and guide aspiration 4