Pain Trajectory and Long-Term Clinical Outcomes After CT-Guided Radiofrequency Ablation of Osteoid Osteoma

Technical Summary: Pain Trajectory and Long-Term Clinical Outcomes After CT-Guided Radiofrequency Ablation of Osteoid Osteoma

Problem Statement
Osteoid osteoma is a benign bone tumor characterized by a vascular osteoid-rich nidus, typically causing severe nocturnal pain that significantly impairs quality of life. While CT-guided radiofrequency ablation (RFA) is an established first-line minimally invasive treatment with high success rates, existing literature often relies on binary endpoints (e.g., complete symptom resolution vs. failure). This approach fails to characterize the temporal pattern of pain relief or distinguish between low-grade residual symptoms (which may be benign post-procedural irritation) and clinically relevant treatment failure or recurrence. Consequently, post-procedural counseling and follow-up strategies may lack precision regarding the expected timeline of recovery and the interpretation of minor residual pain.

Methodology
This retrospective, single-center cohort study analyzed 48 patients treated with CT-guided RFA for symptomatic osteoid osteoma between 2019 and 2025. One patient was excluded from an initial pool of 49 due to a revised diagnosis of an atypical stress fracture.

• Patient Demographics: The median age was 19 years (range 4–54), with 68.8% male. Lesions were predominantly located in the femoral diaphysis (27.1%), followed by the tibia and femoral neck.
• Procedure: All procedures utilized sterile technique under CT guidance. A bone biopsy was performed to confirm diagnosis prior to electrode placement. A Cool-tip Series E system with a 7–10 mm active tip was used to ablate the nidus at a target temperature of 90°C. Hydrodissection (using 5% dextrose) was employed in 64.6% of cases to protect adjacent neurovascular or articular structures.
• Anesthesia: Selection was based on patient age and lesion complexity, utilizing general anesthesia (50%), neuraxial anesthesia (43.8%), or regional anesthesia (6.2%).
• Data Collection: Pain intensity was measured using a 10-point Visual Analog Scale (VAS) at three points: pre-procedure, the first postoperative day, and long-term follow-up (6–48 months).
• Definitions:
  • Immediate improvement: Patient-perceived meaningful improvement by day 1.
  • Clinically minimal pain: VAS 0–2.
  • Complete clinical response: VAS 0 at long-term follow-up.
  • Treatment failure: Determined by persistent/recurrent pain combined with functional limitation and imaging evidence of recurrence, rather than a non-zero VAS score alone.
• Statistical Analysis: Changes in pain intensity were analyzed using the Friedman test, followed by Wilcoxon signed-rank tests with Bonferroni correction for pairwise comparisons. Complications were graded according to the CIRSE classification system.

Key Results

• Pain Trajectory: The median VAS score dropped significantly from 9 (severe baseline) pre-procedure to 1 on the first postoperative day, and to 0 at long-term follow-up.
  • Day 1: 95.8% (46/48) of patients achieved a VAS of 0–2. 93.8% (45/48) reported immediate perceived clinical improvement.
  • Long-term: 93.8% (45/48) were completely pain-free (VAS 0).
• Residual Symptoms: Two patients (4.2%) had minimal residual pain (VAS 1–2) at long-term follow-up, which did not cause functional limitations or require retreatment.
• Treatment Failure vs. Alternative Causes: One patient (2.1%) experienced clinically relevant pain (VAS 5) that persisted from day 1. However, 37 months of follow-up imaging showed no evidence of recurrent osteoid osteoma; the pain was attributed to a different clinical condition. No patient returned to pre-procedural pain levels.
• Safety: No procedure-related complications of any CIRSE grade were observed. No patients required repeat ablation, surgery, or other lesion-directed interventions.
• Statistical Significance: Pain intensity differed significantly across all three assessment points (Friedman χ² = 92.30, p < 0.001), with significant improvements observed in all pairwise comparisons.

Significance and Claims
The paper claims that CT-guided RFA provides rapid and durable pain relief for osteoid osteoma, with the majority of therapeutic effect apparent by the first postoperative day. A central contribution of the study is the detailed characterization of the pain trajectory, demonstrating that low-grade residual symptoms (VAS 1–2) are uncommon and do not necessarily indicate radiologic recurrence or treatment failure.

The authors argue that distinguishing between minimal residual symptoms and true recurrence is critical for clinical management. They posit that labeling minor, non-functional symptoms as treatment failure is clinically misleading. Instead, post-ablation pain should be evaluated through a combination of symptom severity, functional impact, temporal evolution, and imaging findings. The study supports the safety and efficacy of the procedure across diverse anatomical sites, including challenging locations like the spine and acetabulum, particularly when adjunctive techniques like hydrodissection are utilized.

Limitations
The authors acknowledge the study's limitations, including its retrospective single-center design, the relatively small sample size preventing robust subgroup analyses (e.g., by lesion location or age), and the lack of a validated multidomain quality-of-life instrument. Furthermore, the absence of a surgical or alternative-ablation comparator limits direct conclusions regarding comparative effectiveness.