Osteoid osteoma.

Osteoid osteoma is a relatively frequent benign bone tumour, consisting of osteoid and woven bone, and surrounded by a halo of reactive sclerotic bone, with an average size of the nidus less than 1.5 cm. It is a condition of late childhood, adolescence and young adult age. It usually occurs in the appendicular skeleton and the spine, and is generally localised in or near the cortex. The lesion causes pain, especially at night, but can cause joint pain with synovitis and joint effusion if located in the vicinity of chondral structures, or painful scoliosis if located in the spine. Osteoid osteoma may have an unpredictable course, and may require treatment or resolve spontaneously. In some cases, the diagnostic approach is challenging; there are different treatment methods, some of which have been recently introduced, with promising results. We review the literature about the natural history, clinical presentation, diagnostic approach and classical or modern treatment modalities of osteoid osteoma.