Osteoid osteoma

Osteoid Osteoma is a benign (non-cancerous) bone tumor that arises from osteoblasts and is characterized by its small size, typically less than 2 cm in diameter. It most commonly affects the long bones of the body, such as the femur and tibia, but can occur in any bone. The hallmark feature of an osteoid osteoma is severe pain, often worse at night, which is remarkably relieved by nonsteroidal anti-inflammatory drugs (NSAIDs), including aspirin.

Symptoms and Diagnosis

The primary symptom of an osteoid osteoma is localized pain that is usually worse at night and is significantly relieved by NSAIDs. The pain is thought to be caused by the tumor's production of prostaglandins. Other symptoms may include swelling and tenderness at the tumor site, and in long-standing cases, muscle atrophy or limb length discrepancy may occur due to the chronic pain and disuse of the affected limb.

Diagnosis of osteoid osteoma typically involves a combination of clinical evaluation, imaging, and sometimes biopsy. Radiographs (X-rays) often show a small, round lesion with a dense center, known as a nidus, surrounded by a halo of reactive bone sclerosis. Computed tomography (CT) scans are more sensitive than X-rays and can help precisely locate the nidus. Magnetic resonance imaging (MRI) can also be used, particularly to assess the tumor's effect on surrounding tissues.

Treatment

The treatment of osteoid osteoma has evolved significantly over the years. Historically, surgical removal of the nidus was the standard treatment. However, less invasive techniques have become more common, including radiofrequency ablation (RFA) and percutaneous CT-guided drilling. These methods allow for the destruction of the nidus with minimal damage to surrounding tissues and have high success rates with low recurrence.

Epidemiology

Osteoid osteoma accounts for approximately 10% of all benign bone tumors. It most commonly affects individuals between the ages of 10 and 30 years, with a male predominance.

Pathophysiology

The exact cause of osteoid osteoma is unknown, but it involves the overproduction of osteoid (bone matrix) by osteoblasts. The nidus is the active part of the tumor and is surrounded by a sclerotic reaction of the bone, which is responsible for the pain.

Prognosis

The prognosis for individuals with osteoid osteoma is excellent, especially with the advent of less invasive treatment options. Most patients experience complete relief of symptoms following treatment, and the tumor does not progress to malignancy.

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Osteoid_osteoma

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  Osteoid osteoma on X-ray and MRI
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  Osteoid osteoma - intermediate magnification
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  Osteoid osteoma in fibula on CT