Osteoid Osteoma is a common benign bone tumour occurring in age group of 5-24 years, affecting males more commonly. It is composed of osteoid and woven bone surrounded by a halo and sclerotic rim.
Common sites are the cortex of shaft or diaphysis of long bones especially femur, tibia, and small bones of foot followed by bones of hand, pelvis and spine
What is the cause of Osteoid Osteoma?
Etiology of osteoid osteoma is believed to be secondary to proliferation of osteoblasts. The nidus of osteoid osteoma show high concentration of prostaglandins, which are considered to generate local peritumoral reaction and severe pain.
How is osteoid osteoma identified?
An individual with osteoid osteoma presents with dull aching pain for weeks or months, which is worse at night (Night cries) which awakens the individual. This is typically followed by ingestion of Aspirin after which the pain dramatically subsides. But this is a pattern can recur and continue in individuals who do not undergo any intervention.
In chronic presentations, swelling of the involved limb can also be noticed. Osteoid osteoma in hip can present as knee pain in some individuals, similarly spinal osteoid osteoma can present with functional scoliosis.
Radiological evaluation is performed in form of Plain radiograph and CT scan.
On plain radiograph, an eccentrically placed sclerotic lesion can be noted in diaphysis of involved bone.
A CT scan with limited exposure and thin cuts sections is considered Diagnostic for osteoid osteoma. It shows an oval radiolucent are (Nidus) surrounded by a halo of bone sclerosis.
MRI can also provide clues to diagnosis and has the benefit of lesser radiation risk over CT scan.
A bone scan can be performed when the diagnosis is doubtful.
What are treatment options for osteoid osteoma?
Natural history of an osteoid osteoma is to regress with time (2-4 years), hence initial treatment is supportive therapy with Anti-inflammatory drugs to relieve pain. Pain is morbid and can even disable an individual from even carrying out basic daily activities. In situations where Osteoid osteoma is ‘Accidentally discovered’ and the individual has bearable pain, conservative treatment with NSAIDs can be provided.
In majority of individuals with continuing or severe pain, complete surgical removal is advised. This is performed by either an extended curettage or En-bloc excision of osteoid osteoma. Surgical removal was considered ‘The’ standard of treatment for osteoid osteoma until recently. The risk of local recurrence with surgery is 5-10 %.
Currently the “ Gold standard treatment” of Osteoid Osteoma is considered to be a minimally invasive procedure- ‘Radiofrequency Ablation’ (RFA), where in a percutaneous manner, a RFA probe is inserted into the nidus and the area is burned by high temperature of 80-90 degree celcius for 2-3 minutes under controlled environment.
This procedure can be done on Outpatient basis and need no or minimal anesthesia. The damage to surrounding bone is minimal and the individual can resume normal activities the same day with 95 % pain relief. The risk of recurrence has been documented as 3-10 %.
The recurrence could be because of wrong localization of the nidus or due to development of new lesion adjacent to the previous. Spinal osteoid osteomas are not suitable for this technique due to the closeness of vital structures.