- Osteoid osteoma is a self-limiting benign bone tumor.
- It’s one of three bone tumors in which tumor cells produce osteoid:
- Most osteoid osteomas occurs in the second or third decades of life (< 30 years old).
- Male > female (3:1).
- The tumor usually found in cortical bone, (It can also be found in cancellous bone).
- Common locations include diaphyseal bone, proximal femur, tibia, and spine.
- The patient with an osteoid osteoma has pain that is worsen at night and is relieved by aspirin or other nonsteroidal anti-inflammatory medications (NSAIDs).
- Maybe due to increased levels of cyclooxygenases and prostaglandins that have been found in the lesion.
- When the tumor is near a joint, swelling, stiffness, and contracture may occur.
- May produce painful non-structural scoliosis in adolescent.
- The Osteoid osteoma found on the side of concavity.
- This is thought to result from marked para vertebral muscle spasm.
- Imaging studies usually are diagnostic.
- Plain radiographs often are sufficient to make the diagnosis.
- The lesion consists of a small (<1.5 cm) central radiolucent nidus with surrounding bony sclerosis.
- Computed tomography CT is the best study to identify the nidus and confirm the diagnosis.
- It demonstrates better contrast between the lucent nidus and reactive bone.
- Technetium bone scans always show intense focal uptake.
- Double density sign which if present is highly specific and helpful in distinguishing it from osteomyelitis.
- Ultrasound: focal cortical irregularity with adjacent hypoechoic synovitis may be present at the site of intra-articular lesions.
- MRI usually shows extensive surrounding edema.
The double density sign, also sometimes referred to as the hotter spot within hot area sign. It refers to a central focus of intense uptake (the nidus) within a surrounding lower, but nonetheless increased uptake(the rim).
- Fibrovascular tissue with immature bony trabeculae that are rimmed by
prominent osteoblasts, and surrounded by a sclerotic rim.
- It’s appears similar to osteoblastoma (osteoblastomas are larger).
The osteoid osteoma is composed of three concentric parts:
2. Fibrovascular rim
3. Surrounding reactive sclerosis
- Long bones lesions differential diagnosis are:
- Enostoses (bone island)
- Stress fracture.
- Osteomyelitis (Brodie abscess).
- Cortical desmoid
- Posterior spinal lesions differential diagnosis are:
- Aneurysmal bone cyst.
|Presentation||– Diurnal pain pattern/night pain|
– Pain relieved by aspirin/NSAIDs
|– Random pain pattern|
– Pain not relieved by aspirin/NSAIDs
|Imaging||– Central radiolucent nidus < 1 cm Large secondary bone reaction|
– Characteristic “target” appearance
|– Central radiolucent nidus > 2 cm|
– Minimal secondary bone reaction gives lesion a more aggressive appearance
|Location||Diaphyseal (typical)||– Diaphyseal or metaphyseal|
– Posterior spine elements
|Growth pattern||Self-limited growth pattern||Unlimited growth pattern|
|Treatment||– Radiofrequency ablation (RFA)|
– Surgery if tumor is close to nerve or vessels (e.g., spine)
- The patient’s symptoms are adequately controlled.
- The patient is willing to undergo long term medical management.
- Anti-inflammatory medication can be used as the definitive treatment.
- Patients treated in this manner usually experience spontaneous healing of the lesion within 3 to 4 years.
- CT scan–guided RFA:
- It’s the dominant method of treatment.
- Failure of medical management
- Most patients with lesions of the pelvis or long bones of the extremities.
- A lesion close to a critical structure (i.e., neurovascular bundle or spinal cord) is a to RFA.
- A radiofrequency probe is placed into the lesion, and the nidus is heated to 80-90°C.
- It usually is done as an outpatient procedure, and patients usually can return immediately to full activity.
- Recurrence rates are less than 10%.
- Open surgical removal:
- Failure of medical management
- A lesion close to a critical structure (i.e., neurovascular bundle or spinal cord).
- Removal of the entire nidus, this can be accomplished by curettage or en bloc resection.
- Recurrence rates with this technique are less than 10%.