Air-blocking ablation of osteoid osteoma; a technical note

Radiofrequency ablation vs microwave ablation for osteoid osteomas: long-term results

OBJECTIVE

Osteoid osteomas are benign bone tumors commonly treated using thermal ablation. We compare the technical success, complication rates, and long-term efficacy of the two most common ablation types: radiofrequency and microwave.

MATERIALS AND METHODS

A retrospective study was performed of all osteoid osteoma ablation procedures between 2007 and 2017. A ten-point numerical pain scale was used to quantify symptoms before and after the procedures with > 12-month follow-up. Complications were reported using the Society of Interventional Radiology Adverse Events reporting criteria.

RESULTS

Twenty-nine patients successfully underwent 15 radiofrequency ablations and 15 microwave ablations with a technical success rate of 83% for radiofrequency and 100% for microwave (p = 0.23). Long-term recurrence rates (p = 1.0) and complication rates (p = 0.60) were not significantly different for the groups. One patient developed a skin burn following microwave ablation and another developed 12 months of sciatic neuropathy following radiofrequency ablation.

CONCLUSION

Microwave and radiofrequency ablation are safe and effective methods for treating osteoid osteomas with similar long-term efficacies. Although radiofrequency ablation is more commonly reported to result in skin burns, this complication can arise during microwave ablation.

A Rare Case of an Osteoid Osteoma of the Cervical Spine

Osteoid osteoma (OO) is a benign bone tumor rarely affecting the cervical spine. OO, currently diagnosed by X-ray, computed tomography (CT), bone scan, and magnetic resonance imaging, is difficult to identify when located in the cervical spine based on spine radiographs due to their usually small size and the complex anatomy of the cervical spine. CT scans successfully diagnose 20–30% of the small osteolytic lesions with dense sclerotic rings and central calcifications and the anatomic location of the nidus. CT-guided radiofrequency ablation is a noninvasive treatment option widely used. However, in specific cases, surgical resection of the nidus is recommended. We present a rare clinical case of cervical spine OO of a 16-year-old female patient. The lesion was located on the left lamina of C7, and once the diagnosis was established by physical examination and imaging, laminectomy and cervical arthrodesis (C6-T1) were performed. Twelve months after the surgical intervention, the patient showed complete remission of the symptoms and no disabilities.

Effect of the trabecular bone microstructure on measuring its thermal conductivity: A computer modeling-based study

The objective of this work is to quantify the relation between the value of the effective thermal conductivity of trabecular bone and its microstructure and marrow content. The thermal conductivity of twenty bovine trabecular bone samples was measured prior to and after defatting at 37, 47, and 57 °C. Computer models were built including the microstructure geometry and the gap between the tissue and measurement probe. The thermal conductivity (k) measured was 0.39 ± 0.06 W m^-1 K^-1 at 37 °C, with a temperature dependence of + 0.2%°C^-1. Replacing marrow by phosphate-buffered saline (defatting) increased both the computer simulations and measurement results by 0.04 W m^-1 K^-1. The computer simulations showed that k increases by 0.02-0.04 W m^-1 K^-1 when the model includes a gap filled by phosphate-buffered saline between the tissue and measurement probe. In the presence of microstructure and fatty red marrow, k varies by ± 0.01 W m^-1 K^-1 compared with the case considering matrix only, which suggests that there are no significant differences between cortical and trabecular bone in terms of k. The computer results showed that the presence of a gap filled by phosphate-buffered saline around the energy applicator changes maximum temperature by < 0.7 °C, while including the bone microstructure involved a variation of < 0.2 mm in the isotherm location. Future experimental studies on measuring the value of k involving the insertion of a probe into the bone through a drill hole should consider the bias found in the simulations. Thermal models based on a homogeneous geometry (i.e. ignoring the microstructure) could provide sufficient accuracy.