Imaging Guidelines for Osteomyelitis

Initial Imaging Modality

The American College of Radiology recommends plain radiographs (X-rays) as the initial imaging modality for suspected osteomyelitis, providing an excellent anatomical overview and helping to exclude other conditions, though they have limited sensitivity in early infection 1
X-rays provide valuable baseline information and can detect erosions and periosteal reaction, bone sclerosis, soft tissue swelling, presence of gas or foreign bodies, and fractures or tumors that might mimic infection 1

MRI with and without contrast is the most accurate follow-up imaging modality with sensitivity and specificity >90%, providing excellent evaluation of bone marrow changes, soft tissue involvement, abscess formation or fistulas, and extent of infection for surgical planning 1
CT scan is useful when MRI is contraindicated, better than X-ray for detecting sequestrum, foreign bodies, or gas, but less sensitive than MRI for early osteomyelitis 1
Nuclear Medicine Studies, such as 3-phase bone scan, FDG-PET/CT, and WBC scan with SPECT/CT, have high sensitivity and specificity for detecting osteomyelitis 1
The diagnostic imaging tests have the following sensitivities and specificities for chronic osteomyelitis:
Test Sensitivity Specificity
FDG-PET 94% 87%
Bone scintigraphy 82% 25%
MRI >90% >90%

The American College of Radiology recommends considering image-guided bone biopsy for definitive diagnosis if diagnosis remains uncertain after advanced imaging 1
Probe-to-bone test can be performed if an ulcer is present, with a positive test strongly suggesting osteomyelitis 3, 4
Recent surgery or trauma in the affected region can mimic infection on imaging studies 1
Clinical findings such as ulcers overlying bony prominences, exposed bone in wound, ulcer area >2 cm², and erythematous and indurated "sausage toe" appearance should be evaluated, as these are associated with osteomyelitis 4
Elevated inflammatory markers, such as C-reactive protein (CRP), erythrocyte sedimentation rate (ESR >27 mm/h), and procalcitonin, are associated with chronic osteomyelitis 2
Blood cultures are positive in cases of hematogenous spread, with a strength of evidence supporting their use in diagnosis 2

Start with plain X-rays of the affected region (multiple views) 1
If X-rays are negative or inconclusive but clinical suspicion remains high, proceed to MRI with and without contrast (preferred), or consider CT or nuclear medicine studies if MRI is contraindicated 1
The American College of Radiology recommends MRI without and with IV contrast as the preferred imaging modality for evaluating bone and joint infections, rated 9/9 for appropriateness, due to its superior soft tissue contrast and ability to delineate the extent of infection 2, 1

Targeted antibiotic therapy based on culture results, surgical debridement in chronic cases, and extended antibiotic course (typically several weeks) are recommended for the treatment of chronic osteomyelitis, according to the American College of Radiology 2
Appropriate bone sampling for culture is crucial for effective treatment, with a strength of evidence supporting its use in guiding antibiotic therapy 2
Prior antibiotic use can lead to false-negative cultures, according to the American College of Radiology 5
A postoperative antibiotic strategy, including parenteral followed by oral antibiotics, should be considered, and antibiotic-impregnated materials may be useful in certain cases, according to the American College of Radiology 2

Diabetic foot osteomyelitis should be considered in patients with foot ulcers, with a specialized workup recommended, as suggested by the Diabetes/Metabolism Research and Reviews 3
For vertebral osteomyelitis, perform PPD test or interferon-γ release assay if tuberculosis is suspected, and consider fungal blood cultures in at-risk patients, as recommended by the Infectious Diseases Society of America 6
For prosthetic joint infection, joint aspiration with cell count, differential, and culture should be performed, and if initial aspiration is negative but infection still suspected, repeat aspiration, according to the American College of Radiology 5
For diabetic foot osteomyelitis, consider wound cultures from tissues closest to bone when ulcer/sinus tract is present, and avoid wound swab cultures due to contamination risk, as recommended by the Radiological Society of North America 7