Particular imaging features and customized thermal ablation treatment for intramedullary osteoid osteoma in pediatric patients

OBJECTIVE: To report on the particular imaging features and high success rate of cold mode radio-frequency thermal ablation (RFTA) as the treatment of choice for intramedullary osteoid osteoma. MATERIALS AND METHODS: The study population consisted of 51 patients (39 males, 12 females; mean age 7.2 years; 11 patients under 6 years of age, including 7 males and 4 females) who underwent RFTA for osteoid osteoma and were retrospectively observed. The affected sites were the tibia (n = 22, 43%), femur (n = 13, 25%), pelvis (n = 5, 10%), anklebone (n = 3, 6%), humerus (n = 2, 4%), sacrum (n = 2, 4%), heel, radium, patella ,and rib (n = 1, 2%), respectively. Three patients had tibial intramedullary osteoid osteoma (14% of the tibial lesions, 6% of all cases). Cold mode RFTA was performed for these three patients to obtain a large ablation area without positioning two probes. The noncooled mode was used to treat cortical and subperiosteal lesions. RESULTS: Following RFTA, all patients were pain-free and in good clinical condition. In the intramedullary osteoid osteoma group, no recurrences were observed during the 24-month follow-up period, but one patient, who was affected by cortical osteoid osteoma, required two RFTA treatments to heal completely. CONCLUSION: Children less than 6 years of age with recurrent nocturnal pain and limb swelling should be investigated for intramedullary osteoid osteoma. Once confirmed, CT-guided RFTA should be the first treatment for intramedullary osteoid osteomas because of the high success rate and reduced invasivity, especially with cold mode RFTA. The outcome is related to the disappearance of pain, and the efficacy may be checked shortly after treatment with MR imaging to evaluate the absence of lesion in the ablation area.