Spinal Osteoid osteoma

Osteoid osteoma

A benign bone tumour, typically occurs in children and adolescents, more common in males. Characteristically present with night pain which is relieved by the use of salicylate analgesia such as aspirin.

They are a classic cause of painful scoliosis when occurring in spine, concave on the side of the lesion. Soft tissue swelling and oedema may occur and if close to a growth plate, accelerated growth may be evident, may be related to hyperemia.

Most osteoid osteomas occur in long tubular bones of the limbs such as femur and tibia.

The femur is the most common location especially the neck of femur. The mid-tibial diaphysis is the next common location.

Osteoid osteomas are usually cortical lesions with adjacent sclerosis which is reactive and does not represent the lesion itself. 

The nidus is usually less than 2 cm in diameter and is typically ovoid in shape. Associated solid periosteal reaction with cortical thickening on x-ray or CT. The nidus is sometimes visible as a well-circumscribed lucent region, occasionally with a central sclerotic dot. 

CT is excellent at characterizing the lesion and is the modality of choice. 

Nuclear medicine, skeletal scintigraphy will show typical focal uptake and at times will show a double density sign.

MRI is sensitive, but is non-specific and is often unable to identify the nidus due to associated bone marrow and adjacent soft tissue oedema.

The lesion is benign and treatment has traditionally been with surgical resection. 

General imaging differential considerations include:

osteomyelitis, Brodie abscess

osteoblastoma more than 2 cm in size

stress fracture

cortical desmoid

osteochondroma

osteosarcoma

enostosis 

localized cortical thickening

intracortical hemangioma