Pathophysiology and Targeting PSN
The sacroiliac joint complex (SIJC) is a major contributor to chronic low back pain, accounting for up to 30% of cases. It is a diarthrodial synovial joint with complex ligamentous reinforcement, innervated anteriorly by the lumbosacral plexus and posteriorly by the posterior sacral network (PSN). The PSN includes the lateral branches of S1 to S3 and variably L5 and S4.
Targeting the PSN is critical in interventional pain management strategies. Radiofrequency ablation (RFA) of the lateral branches has proven effective in disrupting nociceptive transmission. Anatomical studies emphasize the variability of these nerves, underscoring the importance of wide and continuous lesion coverage to ensure efficacy.
Multitined expandable electrodes enable linear lesioning across the lateral sacral crest, increasing the likelihood of intercepting the PSN. This anatomical rationale supports their clinical application, particularly in cases of refractory sacroiliac joint pain where traditional approaches have failed.
The success of PSN-targeted interventions depends on accurate anatomical knowledge, imaging-guided needle placement, and consistency in lesion creation. These elements form the foundation for effective neuromodulation and long-term pain relief.
Clinical Trial Framework and Outcomes
A multicenter randomized trial investigated the outcomes of percutaneous radiofrequency lesioning of the PSN using multitined expandable electrodes. Inclusion required documented sacroiliac joint pain with a ≥50% reduction following image-guided diagnostic blocks, either via PSN or intra-articular infiltration.
Participants presented with chronic pain for over three months, NPRS ≥4, and failure of conservative therapy. The treatment protocol involved fluoroscopic guidance and temperature-controlled lesioning across multiple sacral levels. Follow-ups occurred at 3, 6, 12, 18, and 24 months, using validated instruments including NPRS, ODI, EQ-5D, and PSQ-3.
At 3 months, over 50% of subjects experienced a clinically significant pain reduction (≥50% NPRS). Functional improvements were equally notable, with ODI reductions ≥15 points in a substantial portion of patients. EQ-5D scores improved by ≥0.03, indicating a meaningful enhancement in quality of life.
Sleep quality, assessed through PSQ-3, also improved post-treatment. These results support the hypothesis that PSN ablation affects both pain intensity and broader functional domains, contributing to overall patient well-being.
Lesioning Technique and Distribution
The success of PSN ablation relies heavily on the precision of electrode placement and the geometry of thermal lesions. Multitined electrodes generate elongated and continuous lesions along the sacral crest, targeting the transverse path of the lateral sacral branches from S1 to S3.
Electrode placement is confirmed via biplanar fluoroscopy (AP and lateral views), with lesioning performed at 85°C for 180 seconds in bipolar mode and 80°C for 90 seconds in monopolar configuration targeting L5. This ensures thorough nerve capture and reproducibility.
Contrast injection during diagnostic blocks enhances accuracy, verifying anesthetic spread and nerve engagement. Pain diaries are used to correlate subjective relief with objective procedural success, allowing a reliable assessment of treatment eligibility.
Uniform application of the technique across centers and operators improves outcome consistency. Operator training and adherence to protocol are critical for minimizing variability and ensuring procedural efficacy.
Long-Term Outcomes and Repeatability
Longitudinal data confirm durable outcomes, with significant pain relief sustained up to 24 months. The protocol allowed for repeat procedures based on clinical judgment and patient-reported outcomes, particularly when NPRS improvement remained ≥50% compared to baseline.
Repeat treatments followed the original technical specifications and preserved the blinding of the randomized study. These secondary procedures showed favorable tolerability and similar efficacy, highlighting the repeatability of the method.
Patients undergoing repeat ablations maintained or regained symptom relief, reducing the need for alternative treatments such as intra-articular injections or surgical fusion. Adverse event rates were minimal across all follow-up intervals.
Kaplan-Meier analysis demonstrated high treatment survival rates, with most patients maintaining benefit without requiring additional interventions. These findings support the role of PSN ablation as a mid-to-long-term management strategy for chronic SI joint pain.
Patient Selection and Clinical Protocols
Patient selection is central to clinical success. Appropriate candidates are identified through diagnostic blocks, response monitoring, and exclusion of alternative pain generators. Confirmatory imaging and a multidisciplinary approach enhance diagnostic accuracy.
Clinical protocols incorporate validated tools such as NPRS, ODI, EQ-5D, and PSQ-3 to monitor therapeutic progress. These instruments provide measurable endpoints for both clinicians and researchers, guiding treatment planning and follow-up strategies.
Technique standardization and operator competency are essential for optimal lesion delivery. The use of multitined electrodes with reproducible lesion geometry supports consistent results across diverse anatomical presentations.
Incorporating repeatability into the treatment model offers a flexible and responsive solution for patients with recurrent or partially responsive pain. PSN ablation should be viewed as a core component of the interventional pain management arsenal, supported by evidence and adaptable to clinical realities.
Recommendations for Pain Specialists
For pain physicians, PSN ablation with multitined electrode systems represents a refined technique grounded in anatomical precision and clinical efficacy. Best practices include:
- Using image-guided diagnostic blocks to confirm SIJ as the pain source
- Applying continuous lesioning along S1–S3 to optimize PSN capture
- Monitoring outcomes with standardized tools (NPRS, ODI, EQ-5D, PSQ-3)
- Planning for repeat procedures as part of long-term patient care
These recommendations reflect a high standard of interventional practice, aligning procedural accuracy with patient-centered outcomes. Adopting such protocols enables reproducible success and integration into multidisciplinary pain management programs.
References
- Conger A. et al. Conventional or Bipolar Radiofrequency Ablation for the Treatment of Sacroiliac Joint Pain? The COBRA-SIJ Study, Double-blind Randomized Trial. University of Utah, 2022.
- Al-Kaisy A., Pang D. NIMBUS: A Novel Multi-Tined Expandable Electrode for Percutaneous Radiofrequency Lesioning of the Sacroiliac Joint. Orthopaedic Proceedings, 2018.
