DDx
Diagnostic Considerations
Osteomyelitis is a known mimic of various diseases, and subacute osteomyelitis is no exception, having all of the presenting signs and symptoms of many bone tumors, both benign and malignant. The variety of radiographic presentations of subacute osteomyelitis has been emphasized by Gledhill. [7] The classic solitary lesion located in the metaphysis surrounded by reactive new bone presents little difficulty in diagnosis. However, extensive erosions of cortical bone, periosteal new bone formation, or both may add a more ominous dimension.
Patients with subacute osteomyelitis may occasionally be initially diagnosed with Ewing sarcoma or osteogenic sarcoma. From these observations, the following lesions must be considered among the differential diagnosis of subacute osteomyelitis:
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When the lesion is diaphyseal and associated with an onionskin periosteal reaction, it may be confused with Ewing sarcoma, Langerhans cell histiocytosis, or, much less likely, osteogenic sarcoma
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When the lesion is epiphyseal, it may be confused with a chondroblastoma, fungal osteomyelitis, or tuberculous osteomyelitis, or with an aneurysmal bone cyst, pigmented villonodular synovitis (PVNS) erosions, giant cell tumor, or gout, depending upon the age of the patient
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Metaphyseal eccentric lesions may be confused with the more common nonossifying fibroma, though typically the diagnosis of nonossifying fibroma is easily made, as is the diagnosis of chondromyxoid fibroma
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Brodie abscesses, osteoid osteoma, and intracortical hemangioma should all be included in the differential diagnosis of an intracortical bone lesion
Media Gallery
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Anteroposterior and lateral radiographs of the distal femur. These images depict a type IIIa epiphyseal lesion.
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Anteroposterior radiograph of the left tibia. This image depicts periosteal reaction of the diaphyseal cortex, type IIb.
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Lateral radiograph of the left tibia. This image depicts periosteal reaction of the diaphyseal cortex, type IIb.
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Anteroposterior radiograph of the distal radius. This image depicts a central metaphyseal lesion (punched-out radiolucency), type Ia.
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Lateral radiograph of the distal radius. This image depicts a central metaphyseal lesion (punched-out radiolucency), type Ia.
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Anteroposterior radiograph of the distal tibia. This image depicts an eccentrically located radiolucent lesion crossing the epiphyseal plate, type IIIb.
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Lateral radiograph of the distal tibia. This image depicts an eccentrically located radiolucent lesion crossing the epiphyseal plate, type IIIb.
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Lateral radiograph of the lumbosacral spine. This image depicts destruction of bone and disc space, type IVa.
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Anteroposterior radiograph of the distal tibia. This image depicts an eccentrically located radiolucent lesion crossing the epiphyseal plate, demonstrating the serpentine sign.
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Lateral radiograph of the distal tibia. This image depicts an eccentrically located radiolucent lesion crossing the epiphyseal plate, demonstrating the serpentine sign.
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Total body scan. This image shows increased radionuclide uptake at the distal left tibia.
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Bone scan of both distal legs and feet. This image depicts increased radionuclide uptake at the distal left tibia.
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Computed tomography scan cut of the right lower extremity. This image depicts a sclerotic lesion of the right iliac bone, type IVb.
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Computed tomography scan cut of the right sacrum. This image depicts a round radiolucent lesion with a sclerotic margin.
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Sagittal T1-weighted (time echo = 10 ms, time repetition = 400 ms) magnetic resonance image of the left ankle. This image depicts a well-defined lesion of decreased signal intensity in the anterior aspect of the distal tibial metaphysis, which extends into the adjacent growth plate and epiphysis.
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Axial fast spin echo T2-weighted (time echo = 48 ms, time repetition = 2400 ms) magnetic resonance image through the distal left tibial metaphysis. This image depicts a well-defined lesion of increased signal intensity in the anterolateral aspect of the distal left tibial metaphysis with a rim of decreased signal intensity.
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Sagittal postgadolinium-enhanced T1-weighted (time echo = 10 ms, time repetition = 650 ms) magnetic resonance image with fat saturation. This image shows a hypodense lesion centrally (fluid) with a moderately thick enhancement, which extends through the growth plate into the epiphysis.
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Coronal postgadolinium-enhanced T1-weighted (time echo = 10 ms, time repetition = 650 ms) magnetic resonance image with fat saturation. This image depicts a hypodense lesion centrally (fluid) with a moderately thick enhancement, which extends through the growth plate into the epiphysis.
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Histologic section of bone. This image depicts subacute osteomyelitis with a mixture of polymorphs and plasma cells in an edematous background. Hematoxylin, phloxine, and safranin (HPS) X 440.
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Histologic section of bone. This image shows fibrosis, degenerating bone spicules, and subacute inflammation. Hematoxylin, phloxine, and safranin (HPS) X 10 X 1 X 5.
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Histologic section of bone. This image depicts fibrosis, a mixture of plasma cells, and occasional polymorphs. Hematoxylin, phloxine, and safranin (HPS) X 25 X 1 X 5.
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Modified classification of subacute osteomyelitis. Type I is metaphyseal. Type Ia is a punched-out central metaphyseal lesion. Type Ib is an eccentric metaphyseal cortical erosion. Type II is diaphyseal. Type IIa is a localized cortical and periosteal reaction. Type IIb is a medullary abscess in the diaphysis without cortical destruction but with onionskin periosteal reaction. Type III is epiphyseal. Type IIIa is a primary epiphyseal osteomyelitis. Type IIIb is a lesion that crosses the epiphysis and involves both the epiphysis and the metaphysis. Type IV is a metaphyseal equivalent. Type IVa involves the vertebral body with an erosive or destructive process. Type IVb involves the flat bones of the pelvis. Type IVc involves the small bones, such as the tarsal bones.
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