In long tubular bones, osteoid osteoma is found is most often found within the proximal or distal portions of the bone shafts.
Fifty percent of cases are found in the lower extremities.
The femoral neck is the single most frequent anatomic site.The tibia is the second most frequently involved long tubular bone; fibular lesions are very rare.
In the upper limbs, the humerus is the most frequently involved bone, and a majority of cases occur around the elbow joint. Involvement of the distal ulna and radius is very rare.
Radiographically, the intracortical lesions of long bones are usually associated with distinct fusiform cortical thickening that is sometimes accompanied by periosteal reaction. Occasionaly the periosteal reaction can be very exuberant, with multiple layers of new bone formation.
When a strong periosteal reaction is present, the lesion can be confused with stress fractures or Ewing’s sarcoma. The intramedullary lesions usually produce less surrounding sclerosis. The absence of distinct sclerosis around the intramedullary nidus is probably related to its distant location from labile periosteum.
A rare complication of osteoid osteoma of long tubular bones is localized overgrowth of bone, angular deformity, or both.
Long-standing hyperemia induced by prostaglandins is probably a factor in accelerated growth of bone in osteoid osteoma. It must be noted that this could only occur in patients who are in growing age. The resulting bone deformity and discrepancy never completely resolve.
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