Discussion
Osteoid osteoma is a small, benign, well-circumscribed osteoblastic cortical lesion, typically identified in long bones or, less frequently, in the subperiosteal region.1 It often affects adolescents. Osteoid osteoma has been described in the talus in a few case series2-7 and is associated with a typical nidus that can be identified on CT scans. It does not present acutely, however. The typical presentation for osteoid osteoma is bone pain at night that responds to nonsteroidal anti-inflammatory drugs. However, this presentation is not universal and is frequently missed.2
Juxta-articular osteoid osteomas in the ankle and foot can be difficult to diagnose. The most common site is the talus.3 The majority of patients link their pain to a remote ankle injury. The time delay to diagnosis is on average 2.5 years, but it can be as long as 10 years.4-6 A CT scan is the best method to identify the nidus; MRI can be misleading if it shows only marrow edema but not a nidus.4,5,7 In our patient, an injury was documented, and the patient denied prior symptoms. We cannot explain how an injury would trigger the formation of an osteoid osteoma or cause a previously asymptomatic osteoid osteoma to become symptomatic.
Medical treatment with nonsteroidal anti-inflammatory drugs has been used but is reported to take 2 to 4 years for resolution of symptoms; many patients may consider the treatment time frame too long when other alternatives are available.8 These include open resection, arthroscopic resection, and image-guided ablation. Open surgical techniques include en bloc resection and curettage. Bone grafting or internal fixation may be performed as needed. Arthroscopic excision of juxta-articular osteoid osteomas offers the advantages of good visualization and avoidance of soft-tissue dissection, and allows for complete excision of the lesion as well as synovectomy.6,9,10 Arthroscopic excision also allows for quicker rehabilitation. Image-guided ablation, such as radionuclide-guided excision, CT-guided thermal ablation, and laser photocoagulation, may be even less invasive but do not allow for direct visualization, complete resection, and biopsy.11
Conclusion
Osteoid osteoma is a small, benign, well-circumscribed osteoblastic cortical lesion, typically identified in long bones or, less frequently, in the subperiosteal region.1 It often affects adolescents. Osteoid osteoma has been described in the talus in multiple case series and is associated with a typical nidus that can be identified on CT scans. Usually, it does not present acutely. The typical presentation for osteoid osteoma is bone pain at night that responds to nonsteroidal anti-inflammatory drugs. This presentation is not universal, however, and is frequently missed, especially when the pain is associated with a prior injury.2 Arthroscopic exploration of the ankle with resection of subperiosteal osteoid osteoma and the associated synovitis using thermal ablation of the base with radiofrequency offers lasting cure with minimal morbidity.