Identifying S3 and S2 as Key Pain-Sensitive Targets in High-Frequency Ultrasound Therapy for Sacroiliitis

Area of Science:

• Pain Management
• Neuromodulation
• Interventional Radiology

Background:

• Sacroiliitis, a cause of chronic low back pain, often shows limited treatment efficacy.
• High-Intensity Focused Ultrasound (HIFU) offers a noninvasive neuromodulation approach.
• Understanding nerve branch contributions to pain during HIFU is crucial for optimizing treatment.

Purpose of the Study:

• To map pain distribution during HIFU targeting lumbosacral nerve branches (L5-S3) in sacroiliitis patients.
• To identify specific nerve targets that elicit the most pain responses.
• To inform targeted interventional strategies for sacroiliitis.

Main Methods:

• Eight patients with sacroiliitis underwent HIFU ablation targeting L5-S3 nerve branches.
• Procedural data, including pain-related interruptions, were prospectively recorded.
• Statistical analyses (chi-square tests, Cohen's w) evaluated pain interruption distribution.

Main Results:

• Over 243 sonications, 66.7% interruptions were pain-related.
• Pain interruptions predominantly occurred at S2 (81%) and S3 (42%).
• S3 showed significantly higher pain sensitivity than L5, S1, S2, and combined branches (large effect size).

Conclusions:

• Sacral nerve branches, especially S3, are disproportionately sensitive to pain during HIFU.
• S2 also exhibits significant pain sensitivity.
• Prioritizing S3 in HIFU interventions may enhance sacroiliitis treatment efficacy.