Osteoid Osteoma

By admin Last updated Feb 16, 2024

Ovid: 5-Minute Orthopaedic Consult

Editors: Frassica, Frank J.; Sponseller, Paul D.; Wilckens, John H.

Title: 5-Minute Orthopaedic Consult, 2nd Edition

> Table of Contents > Osteoid Osteoma

Osteoid Osteoma

Frank J. Frassica MD

Basics

Description

A small, benign bone tumor that causes intense pain and marked sclerosis
The lucent nidus in the bone is 0.5–1.5 cm in diameter.
Although the proximal femur is the most
common site, followed by the tibia, almost any bone may be affected,
including the phalanges.

Epidemiology

Incidence (1,2)

Comprises 10% of all benign bone tumors
Occurs primarily in persons 5–25 years old
Male:Female ratio, 3:1 (reason unknown)

Risk Factors

Genetics

No genetic predisposition is known.

Etiology

The cause is unknown.

Diagnosis

Signs and Symptoms

Pain is more severe at night and often is relieved by aspirin or other NSAIDs.
A limp is common.
Mild atrophy or wasting of muscles in the area may occur.
The region is tender to palpation.
If the osteoid osteoma is near a joint, it may cause stiffness.
- If it involves the spine, scoliosis may be seen.
The presence of osteoid osteoma in >1 site in a patient is unusual.

Physical Exam

Mild swelling, erythema, and occasional muscle wasting in the involved area
Absence of fever
Tenderness and stiffness in the region of the osteoid osteoma

Tests

Lab

No laboratory findings aid in the diagnosis.

Imaging

In many areas, because the bone is not seen in cross-section, the diagnosis may not be apparent with plain films.
CT is the best imaging modality for
confirming the lesion, but the lesion’s location must be known to
obtain the correct position on the CT scan.
- Characteristic “target” appearance of the nidus and its sclerotic rim:
  - An oval radiolucent nidus of ~5–10 mm surrounded by a dense reactive zone
  - Nidus often visible in the bone’s cortex
Bone scanning is useful for confirming or
localizing an osteoid osteoma if the lesion’s location cannot be
determined by plain radiographs.
- The bone scan is always focally positive.

Pathological Findings

On cross-section, the nidus appears as a
haphazard arrangement of osteoblasts and trabeculae, which is
surrounded by a dense shell of cortical bone.
On microscopic examination:
- The nidus is composed of dense, normally
  woven bone with osteoblastic rimming, and the reactive shell around it
  is composed of dense cortical bone.
- The cells have a normal, benign appearance.

Differential Diagnosis

Osteomyelitis
Stress fracture
Buckle fracture

P.297

Treatment

General Measures

Osteoid osteomas may resolve spontaneously in 2–6 years.
NSAIDs may be used during this time to control the pain.
Because of pain or intolerance to analgesics, many patients request treatment of the lesion.

Activity

For patients treated nonoperatively, activity may be allowed as tolerated.
Return to normal activity is allowed within 2–4 weeks of radiofrequency ablation.
After surgical excision, partial
weightbearing should be recommended for 6–8 weeks until the bone has
had time to remodel and gain strength.

Medication

Aspirin, regular or enteric-coated
Ibuprofen
Naproxen

Surgery

Radiofrequency ablation is the preferred method of treatment.
- Patients are given general anesthesia.
- The radiofrequency probe is placed into the nidus under CT guidance.
  - The radiofrequency probe must be insulated to prevent soft-tissue necrosis.
- The nidus is heated to ~80°C for 4–6 minutes.
- Effective in 90% of patients with 1 or 2 treatments (3,4)
Surgical resection may be necessary after failed radiofrequency ablation or in sites where the risk of thermal injury is high.
- En bloc resection is not necessary.
- Removal of the cortical bone over the lesion and curettage of the nidus is effective.

Follow-up

Prognosis

The prognosis is excellent.
No risk of malignant transformation exists.

Complications

Fracture after surgical excision may occur.
Gastritis or ulcers from NSAIDs

Patient Monitoring

Frequent monitoring is not needed because these lesions have no malignant potential.

References

1. McCarthy
EF, Frassica FJ. Primary bone tumors. In: Pathology of Bone and Joint
Disorders: With Clinical and Radiographic Correlation. Philadelphia: WB
Saunders, 1998:195–275.

2. Frassica
FJ, Waltrip RL, Sponseller PD, et al. Clinicopathologic features and
treatment of osteoid osteoma and osteoblastoma in children and
adolescents. Orthop Clin North Am 1996;27:559–574.

3. Rosenthal DI, Hornicek FJ, Torriani M, et al. Osteoid osteoma: Percutaneous treatment with radiofrequency energy. Radiology 2003;229:171–175.

4. Venbrux AC, Montague BJ, Murphy KP, et al. Image-guided percutaneous radiofrequency ablation for osteoid osteomas. J Vasc Interv Radiol 2003;14:375–380.

Miscellaneous

Codes

ICD9-CM

213.9 Osteoid osteoma

Patient Teaching

Patients should be counseled about the benign nature of the lesion and its tendency to resolve spontaneously over the years.
Patients may be offered medical or surgical treatment and allowed to choose between them.
For intensely painful or disabling
lesions, or in patients unable to tolerate NSAIDs, an intervention such
as radiofrequency ablation or surgical excision often is selected.

FAQ

Q: Is protected weightbearing necessary after radiofrequency ablation?

A: In general, protected weightbearing is not necessary, and the patient may resume normal activities quickly.

Q: Who performs radiofrequency ablation of osteoid osteomas?

A:
Patients should be seen by an orthopaedic oncologist first and then be
referred to an interventional radiologist for the procedure.

Q: What is the best imaging modality for detecting an osteoid osteoma?

A: CT scanning (thin cuts, 1 mm) is the best method.