Diagnostic Approach for Suspected Osteomyelitis of a Wound

Initial Diagnostic Algorithm

The American College of Radiology recommends MRI without and with IV contrast as the most appropriate initial imaging study to rule out osteomyelitis of a wound over the left hip, following plain radiographs, due to its superior sensitivity and specificity 1, 2, 3
Plain radiographs are the first step in the diagnostic algorithm, helping to evaluate for radiodense foreign bodies, soft-tissue gas, and exclude alternative diagnoses such as fractures or tumors, although they have limited sensitivity in early osteomyelitis 1, 4, 5
MRI without and with IV contrast is the second step, proceeding if radiographs are normal or inconclusive but clinical suspicion remains high, providing excellent assessment of both bone and soft tissue involvement 1, 2, 3, 6, 7

When MRI is contraindicated or unavailable, CT with IV contrast can be used to detect cortical bone destruction, sequestra, and sinus tracts, although it is less sensitive than MRI for early osteomyelitis 1, 5, 7
Nuclear medicine studies, such as 3-phase bone scan, can rule out osteomyelitis with high sensitivity but poor specificity, and are most accurate when bone is not affected by other conditions like osteoarthritis or recent fracture 1, 2, 5
A combined nuclear medicine approach, including sequential 3-phase bone scan, WBC scan, and sulfur colloid scan, can increase specificity and is particularly useful with orthopedic hardware or altered bone marrow distribution 1, 2, 5
Ultrasound has a limited role in direct osteomyelitis diagnosis but is useful for detecting associated soft tissue infections, with high sensitivity and specificity for diagnosing superficial abscesses, and can guide aspiration of fluid collections for diagnostic sampling 1, 2, 5

The American College of Radiology advises against relying solely on radiographs to rule out infection, as early osteomyelitis may have normal radiographs, and recommends obtaining contrast-enhanced MRI when evaluating soft tissue involvement 3, 4
Misinterpreting post-surgical or post-traumatic changes as infection on MRI can lead to incorrect diagnosis and treatment 3

If soft tissue abscess is detected, ultrasound or CT-guided aspiration may be needed for microbiological diagnosis, as recommended by the American College of Radiology 2
FDG-PET/CT may be considered for cases with suspected multifocal infection or when hardware is present, according to the American College of Radiology 1