Image Quiz

Painful Ankle in a Thirteen-Year-Old Boy (continued)

Answer: Osteoid osteoma of the talus.

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Fig. 1	Fig. 2	Fig. 3
Fig. 1 Anteroposterior and lateral radiographs of the right foot (arrows indicate the site of the patient's pain). No osseous abnormalities were noted. Fig. 2 Axial T2-weighted magnetic resonance image of the talus (arrow indicates nidus of the lesion). Fig. 3 Coronal computerized tomographic image of the lesion, demonstrating the nidus.

The patient underwent radiofrequency thermoablation of the nidus, resulting in rapid relief of symptoms. At the time of the four-month follow-up, the patient was active and had full function and no symptoms.

Fig. 4

Fig. 4 Computed tomographically guided radiofrequency thermoablation of the osteoid osteoma.

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Discussion

Osteoid osteoma, a benign tumor of the bone, was first recognized as a clinical entity by Jaffe in 1935¹. It is the third most common primary benign bone tumor, comprising approximately 10% to 12% of benign bone tumors^2-4. The lesion occurs in the long bones, with a predilection for the femur, the tibia, and the lumbar spine, but it can develop in any bone⁵. It is most frequently observed in patients who are in the second decade of life, and it affects men more than women by a ratio of 3:1⁶. The growth of the lesion is restricted, and the lesion is rarely found to be greater than 1.5 cm in diameter⁶. Osteoid osteoma comprises 26% of (benign and malignant) tumors of the foot⁷.

A history of dull pain that is worse at night and disappears within twenty to thirty minutes of treatment with nonsteroidal anti-inflammatory medication is the classic history of a patient with osteoid osteoma. Pain relief with use of nonsteroidal anti-inflammatory drugs is probably related to inhibition of prostaglandin secretion by the tumor. Joint pain and synovitis may occur secondary to an intraarticular lesion. Signs can include a local increase in skin temperature, increased sweating, and local tenderness. An estimated one-third of patients with osteoid osteoma do not present with the classic physical and radiographic findings⁸. Characteristic radiographic findings consist of a well-delineated, smooth, regular, round-to-oval, small radiolucency, with surrounding dense sclerotic bone. Computed tomographic scans have reliably demonstrated the location, nidus, and characteristic diagnostic radiographic features of osteoid osteoma in various studies⁹. In a prospective, blinded study of osteoid osteoma in children, Hosalkar et al. found computed tomography to be more diagnostically accurate than was magnetic resonance imaging¹⁰.

Histologically, the nidus is a woven osteoid and osseous trabeculae of various sizes, clearly surrounded by bone (which may be densely sclerotic)⁶. The histologic and radiologic similarities of osteoblastoma and osteoid osteoma make their differentiation difficult; thus, one must consider lesion size and clinical presentation to arrive at the correct diagnosis¹¹.

Surgical en bloc resection, curettage, or radiofrequency thermoablation of the lesion are the most frequently used modalities of treatment¹². Other procedures include computed tomographically guided core drill excision, magnetic-resonance-image-guided laser ablation, and arthroscopic removal with motorized instruments specifically for talar osteoid osteoma. Local recurrences of 12% after curettage and 4.5% after en bloc resection were reported in a study of 106 patients with peripheral osteoid osteoma¹³. The authors recommended curettage in preference to minimally invasive methods for subperiosteal tumors that are readily accessible. When the diagnosis is unclear or when further histological analysis is required, curettage is also preferable¹³.

Radiofrequency thermoablation has been used in the treatment of all appendicular osteoid osteomas except when the neurovascular bundle is within 1.0 to 1.5 cm of the nidus, the diagnosis is in doubt, or there has been persistence of symptoms despite two ablative procedures¹⁴. Rosenthal et al., in their series of 126 patients who were treated with computed-tomographically guided thermoablation of appendicular osteoid osteomas and then followed for two years, reported complete relief of symptoms after the procedure in one hundred and twelve of one-hundred and twenty-six (89%) patients and resolution after treatment in one-hundred and seven (91%) patients for whom radioablation was the primary treatment¹⁵. We prefer curettage to radiofrequency ablation in any recalcitrant lesion, a lesion within 1.5 cm of a neurovascular structure, or a lesion that is very close to skin. In the latter instance, radiofrequency thermoablation can possibly cause skin burns.

It is important to note that osteoid osteoma may resolve spontaneously. Pain may decrease over two to four years and eventually disappear⁸. Thus, if the symptoms are tolerable, a regimen of observation and treatment with analgesics may be tried¹⁶.

*The authors did not receive grants or outside funding in support of their research for or preparation of this manuscript. They did not receive payments or other benefits or a commitment or agreement to provide such benefits from a commercial entity. No commercial entity paid or directed, or agreed to pay or direct, any benefits to any research fund, foundation, educational institution, or other charitable or nonprofit organization with which the authors are affiliated or associated.

References

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