Osteoid osteoma

Tumours of the bone or neoplasms of the bone are relatively rare, but important conditions in clinical practice. Osteoid osteoma is type of bone formation lesion.
Osteoid osteoma is reactive lesion of the bone, which simulates a tumour. This lesion is benign in nature. There is characteristic “nidus” formation which is less than 2 cm in diameter, and surrounded by a reactive bone lesion. The exact pathogenesis of this lesion is not clear.
Incidence:
It occurs in children and young adults of the age between 10 – 25 years and it is common in males.
The common sites of the involvement are cortex of the long bones such as the tibia, the femur and the humerus.
Clinical features:
There is vague, intermittent pain which can be localized to the bone. The pain is worse at night. The child limbs due to pain. There is swelling, tenderness, restricted movements. There is no stretching of the skin and warmth. There is no raise of temperature. If the hip bone is involved then diffuse back pain is present. If there is involvement of lamina or pedicle of the vertebra then patient presents with a painful scoliosis.
Therapeutic test:
When the patient is given salicylates like Aspirin, the pain reduces dramatically and this test can confirm the diagnosis. This is known as therapeutic test.
Radiology:
There is an area of rarefaction less than 2 cm in diameter, which may be in the cortical, sub – cortical or Sub – periosteal area of the bone. This is surrounded by dense area of osteosclerotic bone tissue. There is a dense ossification centre in the middle called the Nidus. It is clearly seen in the CT scan.
Histology:
The nidus consists of osteoid tissue or woven bone lying in a fibro – vascular stroma. At the periphery there are spicules of calcified osteoid tissue.
Treatment:
Rest and analgesics can prove effective.
In chronic cases, excision of the osteoid bone is done.
Absolute alcohol injection and laser ablation is done with success recently.