Osteoid Osteoma is defined as a bone-forming lesion that is generally less than 2 cm with central well-defined hypervascular areas of rarefaction (Nidus). It consists of Vascular fibrous tissue, proliferating fibroblasts, and minute spicules.
Osteoid Osteoma consists of 10 % of benign bone tumors.
Etiology
There are different hypotheses:
- Trauma
- Inflammation
- Developmental causes secondary to altered vascularity
Age group:
5 – 30 years
90 % below 30 years
Male: Female = 2/3: 1
Site:
Long bone i.e. Proximal femur (most common) > Proximal tibia ( 50 %)
Spine: Posterior elements more commonly affected
In 10 % of cases, there is intraarticular involvement with the Hip.
Clinical Features
Pain is present which is generally progressive, intense, continuous, and worsens at night.
Pain responds to NSAIDs in 70 % of cases.
Localized, tender swelling, fusiform shape.
Reactive sclerosis and pain are present due to the focal production of high levels of prostaglandin E2 and Prostacycline.
Spinal Lesion causes localized back pain, muscle spasm, secondary sclerosis, and pelvic tilt.
Radiological Findings
There is a small solitary rarefaction lesion that is less than 2 cm in size
Subcortical lesion and Subperiosteal lesion which is surrounded by thick sclerotic bone
Radionucleotide scan will shows double density sign
There is a focal area of increased activity and a second smaller area of increased uptake.
CT Scan is the best diagnostic modality which is classified as:
- Subperiosteal
- Intracortical
- Endosteal
- Intramedullary
Pathology
There is a central area of osteoid production surrounded by sclerotic bone.
Treatment
Treatment is self-limiting
It will mature spontaneously over the course of several years.
During maturation, there is the nidus which calcified then ossifies and bends into the surrounding tissue.
Radiofrequency ablation is currently the treatment of choice.
Osteoma
Osteoma is a benign slow-growing tumor that affects mainly membranous bones of the skull and face.
There are two types:
- Sino-nasal Osteoma: Seen in Skull and faces
- Parosteal Osteoma: Seen in long bones
Etiology
Most osteoma occurs spontaneously
Other causes are:
- Trauma
- Inflammation
- Infection
- Developmental reasons
Garden’s Syndrome: Multiple Osteomas + Multiple cutaneous / subcutaneous lesions ( sebaceous cysts, skin fibromas, desmoid tumor) + Intestinal polyposis
Male: Female= 2:1
Osseous choristomas is osteomas in soft tissues.
Clinical Features
Large paranasal sinus causes sinusitis, nasal discharge, headache, and pain.
Loss of the sense of smell is possible
Orbital Osteomas:
Exophthalmos, Double vision, and pressure of the optic nerve may cause loss of vision.
Parosteal osteomas present with pain.
Pathology
Similar to normal bone
It presents as dense compact bone in the slow-growing tumor.
Vibrous fibrous stroma is found in Rapidly growing tumors.
Treatment
In asymptomatic cases, there is no treatment necessary
In symptomatic cases, excision is the treatment of choice.
The defect in the skull is managed with reconstruction with a tantalum plate.
See also: CHONDROBLASTOMA
See also: Osteosarcoma
See also: Musculoskeletal Malignancy: Management
