158 - Long-Term Outcomes of CT-Guided Percutaneous Cryoablation of Osteoid Osteomas

Purpose: The purpose of this study is to evaluate the safety, technical success, and clinical efficacy of percutaneous cryoablation for the treatment of osteoid osteoma. In addition, we aim to retrospectively assess the diagnostic yield of pre-ablation nidus core biopsy and to characterize patterns of pain recurrence during long-term follow-up.

Materials and Methods: This retrospective study was performed by using a radiology report search engine (mPower Nuance, Microsoft, USA) to query all radiology reports about cryoablation of suspected osteoid osteomas in our institution. A physician then manually reviewed all reports to include those patients in an institutional database. Then, electronic medical records and radiology reports were used to collect patient demographics, lesion characteristics, biopsy results, procedural information, and follow-up data. Technical success was defined as complete probe coverage of the nidus by ice ball margin, confirmed by a CT imaging after the last thaw. Recurrence was recorded as a routine use of NSAIDs for local pain after ablation at any follow-up visit.

Results: A total of 30 consecutive patients (mean age: 25.8 years; range: 12-68; F:M ratio 5:25) underwent CT-guided cryoablation for imaging suspected osteoid osteoma between 2015 and 2024. The most common bone treated was the femur (n=14), followed by the tibia (n=5), and the ulna (n=3) and fibula (n=3). The mean nidus size was 7.4 mm (range 3 mm - 12 mm). Most of the procedures had two freeze-thaw cycles (87%), three patients underwent 3 cycles, and only one patient underwent 1 cycle. Technical success was achieved in 100% of procedures. Only 4 (13%) patients required post-ablation pain management with NSAIDS before being discharged home on the same day. A total of 29 patients underwent core-biopsy of the nidus before the ablation, 63% (n=19) had a confirmed osteoid osteoma diagnosis, 30% (n=9) had reactive or cortical sclerosis without definite diagnosis, and one case was diagnosed as cortical chondroma. At a mean follow-up time of 40.6 months (range 5 - 91), the permanent symptomatic resolution of the symptoms after one ablation session was 93% (n=28). Recurrence was reported in 7% (n=2) of the cases; one required a second cryoablation session, and the other surgery. Pain was completely resolved in both patients after the second procedure. No complications were observed at immediate or long-term follow-up.

Conclusion: Percutaneous cryoablation is a safe and effective minimally invasive treatment for osteoid osteoma, demonstrating high rates of technical success, durable pain relief, and low recurrence rates.