Resection with wide margins should theoretically minimize the chance of local recurrence but at the cost of increase risk of surgical morbidity, especially for lesion located proximal to S3 [19, 22, 52].

Image-guided radio-frequency thermal ablation (RFTA) reduces the pain and improves the function and quality of life of patients with painful bone tumors. It has been used to treat benign bone tumors and tumor-like lesions, and it is the gold-standard procedure for most osteoid osteomas [53]. Even if osteoblastoma is histologically similar to osteoid osteoma, this tumor can exhibit aggressive behavior, and recurrences are not uncommon after classic treatment by surgical excision or curettage [54]. RFTA could be performed in the same way as for osteoid osteomas, using electrodes with a longer active tip or a greater number of ablation sessions or multi-tip array probes [55].

In our literature review, we were able to find only one case of sacral osteoblastoma that died of disease [17]. Dal Cin et al. reported a 35-year-old man with osteoblastoma of the sacroiliac joint treated with partial resection. The pathologic examination revealed an intralesional margin, and the patient was subsequently treated with chemotherapy and radiation therapy (without effect) and died 2 years after diagnosis [17]. The authors explained the aggressive clinical behavior with a possible malignant transformation of the stromal component [17].

The recurrence rates for osteoblastomas of the spine after intralesional excision have been reported between 10 and 19% [3, 56, 57], but the rate approaches 50% in the more aggressive pattern. Some studies reported a correlation between the incidence of recurrence and a previous inadequate treatment in non-referral centers [52, 58]. Boriani et al. [58], in a series of 50 osteoblastomas of the mobile spine, reported an incidence of recurrence among “not intact” patients (cases already treated elsewhere) significantly higher compared to “intact” patients (cases treated in the same institution since the beginning): 50% vs. 5%. Some tumors are more prone to recurrence than others, and some factors relating to surgery may explain this, but the molecular features driving this for osteoblastoma are not known. Also in authors’ experience, previous inadequate intralesional surgery was associated with higher rate of local recurrence (40%—two local recurrences in five cases) than patients primarily treated at a specialized tumor center with high levels of surgical and oncologic expertise (7.7%—one local recurrence in 13 cases) [6].