Imaging-guided radiofrequency ablation of osteoid osteoma in typical and atypical sites: Long term follow up

Abstract

Purpose: To assess efficacy and safety of imaging-guided radiofrequency ablation (RFA) of Osteoid Osteoma (OO) in both typical and atypical sites.

Methods and materials: Between January 2014 and March 2019, 102 consecutive percutaneous RFA were performed and retrospectively reviewed. The procedures were performed using a RFA bipolar ablation system (Covidien, exposed tip of 0.7-1cm), under Computed Tomography (CT) guidance or using a navigation system (Masmec) under CT and Cone Beam CT (CBCT) guidance. Patients were followed up over 24 months. Clinical success and recurrences were considered on the base of established criteria. In patients with clinical failure and/or imaging evidence of relapse, retreatment was considered.

Results: Administered power per-procedure was ≤8 W (mean temperature, 90°C). The pre-procedure average value of visual analog scale (VAS) was 8.33+/-0.91. Primary and secondary success rate 96.08% (98/102) and100% (102/102), respectively. No major complication was described. Technical success was proved in every patient by CT scan acquisition after needle positioning. Relapse and tumour location were significantly correlated (p-value = 0.0165). The mean dose-length product was 751.55 mGycm2. Advanced bone healing was noted in 68 lesions after 1y-follow up and in 86 lesions after 2y-follow up.

Conclusion: Imaging-guided percutaneous RFA is a highly effective technique for OO, both in typical and atypical sites. CT or CBCT guidance, navigation systems and operator experience grant the technical success, which is the most crucial parameter affecting outcome.

Fig 1. Consort flow chart.

Fig 2. The RF electrode positioning in the osteoid osteoma before ablation under CT guidance.

Fig 3. Average values for VAS score with 95% C.I.

Fig 4. 23-year-old male patient with an osteoid osteoma in the left sacroiliac joint.

A, B–Sagittal and axial CT scans performed with patient in prone decubitus position show an osteoidosteoma in the left sacroiliac joint (arrows). The diameter of the nidus is 13 mm. C, D–Coronal and axial CT-guided RFA scans show the correct position of the tip of the RF electrode (arrow heads) within the center of the nidus (technical success). Ablation was successfully performed. No complication was registered. The patient was discharged symptom-free three days after the procedure (clinical success).

Fig 5. 15-year-old male patient affected by an osteoid osteoma in the left lamina of the posterior arch of L4.

A–Axial CT image shows an osteoidosteoma in the external aspect of the posterior arch of L4. The diameter of nidus is 7 mm. B, C, D–Axial CT-guided RFA scans show the correct position of the tip of the RF electrode within the center of the nidus (technical success). (c) Ablation was successfully performed. The risk was the possibility of affection of the nerves belonging to the caudaequina and the left L5 nerve root by thermal injury. However, this did not happen as the size of the active electrodetip was exactly equal to the diameter of the nidus and the whole thermal energy was contained within the nidus. The patient was discharged symptom-free two days after the procedure.