772 - Choosing the Right Path: S1 Vertebral Body Access Strategies in Intervention

Learning Objectives: 1. Review sacral anatomy and common anatomical variations.
2. Outline major sacral access approaches for intervention.
3. Recognize how anatomy and intervention type guide approach selection.

Background: The sacrum is a triangular bone at the base of the spine, formed by five fused vertebrae. It articulates with the ilium laterally and L5 cranially. Variations such as sacral dysmorphism, transitional vertebrae, and altered fusion patterns are common {1}. Zone 1 sacral access is well established {2,3} but vertebral body access can vary in difficulty depending on location. Herein we will demonstrate transpedicular and trans-iliac approaches to performing S1 vertebral body access.

Clinical Findings/Procedure Details: Zone 1 S1 sacral interventions can be performed through several established approaches. The short-axis technique provides percutaneous access perpendicular to the sacral ala and is often used for targeted cement augmentation or biopsy {2}. In contrast, access into S1 vertebral body is more nuanced and less established. The trans-iliac route requires lateral entry across the posterior ilium and sacroiliac joint, enabling access to the S1 vertebral body. This additionally stabilizes the instrument as it traverses a great length of cortical bone. The transpedicular technique uses the sacral pedicle to access central sacral lesions, with trajectory optimized to avoid cortical breach or neurovascular injury. Preprocedural CT or MRI evaluation is essential to assess anatomic variation, plan needle trajectory, and confirm safe osseous corridors. Choice of approach reflects the interplay between target pathology, patient anatomy, and procedural goals, with imaging guidance critical to minimizing complications and achieving durable outcomes.

Conclusion and/or Teaching Points: 1. Sacral anatomical variations influence and may limit access.
2. Variations alter safe corridors for all major approaches.
3. Imaging-guided, pathology-specific selection is essential for success.