Presentation
A limping child with left hip pain.
Patient Data
Age: 9 years
Gender: Male
From the case:
Osteoid osteoma
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CT scout shows no evident abnormality.
From the case:
Osteoid osteoma
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- Left femoral neck anterior cortex small well defined intra-cortical lytic lesion measuring about 4.5 mm with central sclerotic focus (nidus) surrounded by thin sclerotic rim and mild cortical thickening.
- No fracture line seen.
- Intact both hip joint. No evidence of slipped capital femoral epiphysis or perthes disease.
- Intact peri-articular musculature.
Case Discussion
Typical radiological features of osteoid osteoma with cenral vascular sclerotic nidus surrounded by lucent area and thin sclerotic rim (double density sign). The patient gave a typical history of night pain that is relieved by salicylates.
Plain x-ray shows no definite abnormality. MRI (not shown) shows focal left femoral neck anterior cortex non-specific marrow edema.
The main differential diagnosis is a Brodie's abscess - oval shaped lytic lesion along the long axis of the bone with dense sclerotic margin, no nidus, no double density sign. Osteoblastoma is a large osteoid osteoma (larger than 2 cm).
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