Osteoid Osteoma is a common benign bone tumour.
It is composed of osteoid and woven bone surrounded by a halo and sclerotic rim.
- Age group of 5-24 years
- Affecting males more commonly.
- Diaphysis and rarely Metaphysis, Epiphysis
- Long Bones are commonly involved, femur, tibia followed by small bones and axial skelet
- Intra Cortical
- Sub Periosteal
- Juxta Articular
An arbitrary limit of 15 mm is used to differentiate osteoid osteoma versus osteoblastoma (larger)
What is the cause of Osteoid Osteoma?
- 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?
- Pain– Dull aching pain for weeks or months
Worse at night (Night cries) which awakens the individual.
This is typically followed by ingestion of Aspirin or Painkiller after which the Pain dramatically subsides but temporarily.
But this is a pattern that can recur and continue in individuals if untreated.
- In chronic presentations, Swelling of the involved limb can also be noticed.
- Osteoid osteoma in the hip can present as knee pain in some individuals
- Spinal osteoid osteoma can present with functional scoliosis or bent spine.
- Juxta articular lesions may present with features of joint synovitis.
- Plain radiograph shows an eccentrically placed sclerotic lesion can be noted in diaphysis of involved bone.
- CT scan (limited with thin cut sections) is considered Diagnostic for osteoid osteoma: An oval radiolucent area (Nidus) surrounded by a halo of bone sclerosis and thick solid periosteal reaction is seen.
- MRI can also provide clues to diagnosis and has the benefit of lesser radiation risk over CT scan. Bone edema is observed on MRI in addition to Nidus
- A Technetium 99 Bone scan can be performed to confirm activity or in cases of suspected local relapse.
What are treatment options for osteoid osteoma?
Natural history of an osteoid osteoma is to regress with time ( average between 2-4 years)
- Initial treatment is supportive therapy with Anti-inflammatory drugs to relieve pain.
- Pain is morbid and can even cause disability in carrying out basic daily activities.
- In the majority of individuals with continuing or severe pain, intervention is recommended.
- Extended curettage
- En-bloc excision of nidus with wide margin
Surgical removal was considered ‘The’ standard of treatment for osteoid osteoma until recently.
The risk of local recurrence with surgery is 9-28 %.
- Currently the “ Gold standard treatment” of Osteoid Osteoma is considered to be a Minimally invasive procedure, ‘Radiofrequency Ablation’ (RFA)
- Percutaneous CT Guided Drilling of the nidus is used alone or in conjunction with RFA.
Benefit of RFA or Drilling is that the pain relief is substantial with minimal morbidity (day care procedure with not more than 1 cm surgical scar). The tissue is sent for histopathological evaluation.
Recurrence rates with Minimally Invasive procedures are between 1-16.3 %
- Risk factors for Recurrence as as follows
Eccentricity index > 3