19 yrs male with hip pain
|AP Radiograph of pelvis: Mild illdefinition of medial cortex of right femoral neck with a small lytic lesion. Mild osteopenia of femoral neck and adjacent soft tissue thickening seen|
MRI of pelvis STIR sequence: Ill defined hyeprintensity in the proximal femoral metaphysis with adjacent cortical thickening, mild soft tissue edema and mild joint effusion.
· Nuclear medicine techniques, although highly sensitive, are sometimes nonspecific.
· Plain radiographs initially show soft tissue changes, muscle swelling, and blurring of the soft tissue planes.
· In pyogenic infections, the first change in bone indicates that the infectious process has been present for 2 to 3 weeks or more.
· In general, osteomyelitis must extend at least 1 cm and compromise 30 to 50% of bone mineral content to produce noticeable changes in plain radiographs.
· Early findings may be subtle, and changes may not be obvious until 5 to 7 days in children and 10 to 14 days in adults.
· Typical early bony changes include: periosteal thickening, lytic lesions, endosteal scalloping, osteopenia, loss of trabecular architecture, and new bone apposition.
· MRI is highly sensitive for detecting osteomyelitis as early as 3 to 5 days after the onset of infection.
· The earliest finding of acute osteomyelitis on MRI is an alteration of the normal marrow signal intensity, which can be appreciated as early as 1 to 2 days after the onset of infection; the edema and exudates within the medullary space produce an ill-defined low-signal intensity on the T1-weighted images and a high signal on T2-weighted and STIR or fat-suppressed sequences.
Radiographic Imaging in Osteomyelitis: The Role of Plain Radiography, Computed Tomography, Ultrasonography, Magnetic Resonance Imaging, and Scintigraphy, Semin Plast Surg. 2009 May; 23(2): 80–89.