Correlation of 3-T MRI and CT findings with patient symptoms and treatment outcome in radiofrequency ablation of osteoid osteoma

Abstract Objective The aim of this prospective study was to evaluate pre- and post-treatment MRI and CT findings of osteoid osteoma (OO) patients treated with radiofrequency thermo-ablation (RFTA) and to compare these findings with visual analog scale (VAS) scores. Methods Sixteen patients (4 females and 12 males; mean age of 18.87 ± 8.75 years (range: 8–37)) with OO were examined with CT and MRI, at baseline and at an average of 3 months following the procedure. On pre- and post-procedural CT and MRIs, OO-related findings were recorded. Treatment success was evaluated with VAS scores. Results Baseline VAS scores were 8 or 9 and follow-up scores were 0 or 1, indicating no early recurrences. Nidus diameters decreased significantly after the procedure ( p  = 0.027, p  = 0.002, and p  = 0.002; and p  = 0.001, p  = 0.001, p  = 0.001 for AP, ML and CC nidus diameters for CT and MRI, respectively). The mean nidus volume were significantly decreased after the procedure ( p  = 0.001, for CT and MRI). On post-procedural images, cortical thickening, the signal intensity and contrast enhancement of the nidus and the extent of periostitis were significantly decreased ( p  = 0.019, p  = 0.001, p  = 0.001 and p  = 0.034, respectively). There was no significant change in nidus calcification, perinidal cortical and intramedullary sclerosis, periosteal reaction, bone deformity, bone marrow and soft tissue edema, joint effusion and synovitis after the procedure ( p  = 0.253, p  = 0.062, p  = 0.245, p  = 1, p  = 1, p  = 0.429, p  = 0.371, p  = 0.625, p  = 1). Conclusion Although the changes in imaging findings may be helpful in early follow-up of OO patients treated with RFTA, these changes alone cannot be used with accuracy in predicting treatment response. Level of Evidence Level IV, Therapeutic Study.