Table 1.

A multidisciplinary team (MDT) evaluation which includes radiologist, orthopedic surgeon, infectious disease specialist, and microbiologist is essential for a correct diagnosis of infection.

	X-Ray	Ultrasonography	CT-Scan	MRI	Nuclear Medicine
Acute Osteomyelitis	low sensitivity during the first 10–14 days cortical bone destruction, marrow lucency periosteal reaction soft tissues alterations	juxtacortical swelling of soft tissues periosteal elevation or thickening possible abscess useful in US-guided biopsy	cortical erosion foci of gas soft tissue alterations sinus tracts	highly sensitive in the first 3–5 days medullary edema and exudates zones of necrosis soft tissue alterations/abscess	3-phase 99mTc BS: high negative predictive value LLS + SPECT/CT: method of choice in patients with a recent fracture or recent surgery 18FGD PET/CT: useful in multifocal osteomyelitis and differential diagnosis with tumors 18F-NaF PET/CT recently proposed
Septic Arthritis	bone erosions joint space loss periarticular osteopenia soft tissue swelling acute OM signs on both sides of the joint	joint effusion: high sensitivity, low specificity power doppler: synovial and soft tissue hyperemia useful in US-guided joint aspiration	joint effusion acute OM signs on both sides of the joint	joint effusion enhancing synovitis cartilage thinning periarticular soft tissue edema subperiosteal fluid collection	3-phase 99mTc BS: useful in differentiate OM from soft-tissue infection and in multifocal joint infections 18FDG PET: low specificity
Chronic Osteomyelitis	sclerosis and cortical thickening adjacent to lytic zones within the marrow	useful in case of recrudescence with acute OM signs	sclerosis and cortical thickening invasion of the medullary cavity sequestrum useful in CT-guided biopsy	sequestrum cloaca periostitis fibrovascular scar useful in differentiate acute from chronic OM	18FDG PET/CT: high sensitivity and specificity
Brodie’s abscess	usually, lytic unicameral or multiloculated lesion with a sclerotic rim	not routinary used in diagnosis	lytic lesion with a sclerotic rim well-circumscribed periosteal reaction useful in CT-guided biopsy	“target sign” peripheral ring contrast enhancement	scintigraphy generally positive 18FDG PET: unclear role
Diabetic foot osteomyelitis	foci of air cortical erosion focal osteopenia	not routinary used in diagnosis	periosteal reaction cortical erosion cortical loss changes in bone marrow density	variable acute and chronic OM signs	WBC PET/CT useful in diagnosis
Prosthetic Infections	sclerosis periosteal reaction cortical thickening soft tissue gas component loosening	distention of the pseudocapsule extracapsular fluid collection sinus tracts useful in US-guided joint aspiration	focal and non-focal areas of periprosthetic osseous reabsorption signs of periostitis and cortical alterations soft tissue gas	pericapsular soft tissue edema extracapsular collections bone destruction reactive lymphadenopathy, joint effusion thick or lamellated synovium	LLS + SPECT/CT: method of choice in patients with a recent fracture or recent surgery 18FDG-PET/CT: higher sensitivity but lower specificity than LLS, must be avoided for 3 to 6 months after surgery or trauma
Fracture related infection	low sensitivity and specificity eventually non-union eventually hardware failure eventually acute or chronic OM signs	not routinary used in diagnosis eventually acute or chronic OM signs	eventually non-union eventually hardware failure eventually acute or chronic OM signs	eventually acute or chronic OM signs	3-phase 99mTc BS: high sensitivity, low specificity LLS + SPECT/CT: method of choice for diagnosis 18FDG-PET/CT: high sensitivity and specificity, simpler method, useful in patients on antibiotic therapy
Spondylodiscitis	low sensitivity vertebral body deformity	not routinary used in diagnosis	vertebral body deformity endplate destruction useful in CT-guided biopsy	most used imaging technique high sensitivity, low specificity useful from 1 to 3 weeks before radiographic or CT signs T1-WI hypointense/T2-WI hyperintense vertebral bodies and disc loss of endplate definition high contrast enhancement	3-phase 99mTc BS and LLS: low sensitivity and specificity 67Ga SPECT/TC and 18FDG PET: high sensitivity and specificity new tracers for PET may increase sensitivity and specificity ∙
Tuberculosis arthritis	low sensitivity vertebral body deformity vertebral osteolytic lesions are more frequent than in pyogenic SD	not routinary used in diagnosis	vertebral body deformity often involvement of antero-inferior side of the vertebra posterior involvement more frequent than in pyogenic SD endplate destruction useful in CT-guided biopsy	useful for follow-up lower marrow edema than pyogenic SD areas of caseation intense contrast enhancement large and calcified soft tissue abscesses no bony eburnation	not able to distinguish between pyogenic and non-pyogenic infection
Chronic recurrent multifocal osteomyelitis	X-ray, US, CT-scan are analogous to infective OM sequestra, sinus tracts, abscess are less frequent often symmetrical distribution (clavicles often involved) more frequent in children			whole body STIR sequences useful in diagnosis	scintigraphy less sensitive/specific than whole body MRI 18FDG PET: unclear role