Understanding Dr. Paul Hubbell’s Publication on Transverse Posterior Transfixing SI Joint Fusion
June 30, 2026
Chronic low back pain is one of the most common and challenging conditions in medicine today, and the sacroiliac (SI) joint is increasingly recognized as a major contributor. For patients who fail conservative care, minimally invasive SI joint fusion has become a reliable treatment option. In his publication, Dr. Paul J. Hubbell III and colleagues present a detailed look at a specific technique—the postero-inferior, transverse posterior transfixing SI joint fusion approach—which offers meaningful biomechanical advantages over traditional methods.
This blog breaks down the key insights from that publication and explains why this technique is gaining attention as a potentially superior strategy for achieving stable, durable SI joint fusion.
Why the SI Joint Matters in Chronic Pain
The SI joint connects the spine to the pelvis and plays a critical role in load transfer, shock absorption, and stability. Despite its limited range of motion, dysfunction in this joint can lead to significant pain and disability.
As outlined in the publication , SI joint pain can arise from degeneration, inflammation, or mechanical instability. When non-surgical treatments such as physical therapy, medications, and injections fail, fusion becomes the next step to stabilize the joint and reduce pain.
The Goal of SI Joint Fusion
All SI joint fusion procedures aim to achieve three primary outcomes:
- Immediate mechanical stabilization
- Reduction of painful micromotion
- Long-term bone fusion (arthrodesis) across the joint
However, not all techniques accomplish these goals equally. The trajectory of the implant—how and where it travels through the bone—plays a major role in determining stability and fusion success.
What Makes the Transverse Posterior Transfixing Approach Different?
Traditional SI joint fusion approaches typically include:
- Lateral approaches
- Posterior oblique approaches
While effective, these methods often lack optimal engagement with the strongest anatomical structures of the SI joint.
Dr. Hubbell’s described transverse posterior transfixing approach—as used with systems like the Omnia DNA device—takes a different path. Instead of simply crossing the joint, the implant follows a carefully planned trajectory that maximizes contact with both cortical and cancellous bone while engaging the joint’s unique anatomy.
The Biomechanical Advantage: “Hitting the Boomerang”
One of the most important concepts in this technique is engagement with the anterior SI joint’s “boomerang-shaped” cortical surface.
This matters because:
- The anterior portion of the SI joint contains dense cortical bone
- It provides a natural structural “lock point”
- Engaging it creates a self-constrained construct
Most other techniques do not reach or lock into this region. As a result, they may rely more heavily on cancellous bone, which is softer and less resistant to motion.
By contrast, the transverse transfixing approach transforms the implant from a simple stabilizer into a mechanically anchored system with enhanced resistance to movement.
Understanding the Implant Trajectory
The power of this technique lies in its multi-zone engagement. The implant follows a very specific path:
- Sacral cancellous entry zone – initial entry with lower resistance
- Sacral cortical crossing – first strong anchor point
- SI joint traversal – crossing the joint space
- Iliac cortical engagement – second anchor point
- Iliac cancellous zone – transitional support
- Anterior cortical “boomerang” engagement – critical final anchor
This creates what can be described as a multi-layer fixation system, combining both soft and dense bone interfaces for maximum stability.
Three Cortical Anchor Points: Why They Matter
A defining advantage of this approach is the presence of three cortical anchor points:
- Sacral cortex
- Iliac cortex
- Anterior SI joint cortical surface
Cortical bone is significantly denser and stronger than cancellous bone. By anchoring into multiple cortical surfaces, the implant gains:
- Higher resistance to loosening
- Greater load-bearing capacity
- Improved long-term durability
This is a key reason why the technique is considered biomechanically superior to both:
- Pure cortical transfixing methods (limited anchoring zones)
- Oblique cancellous approaches (less dense bone engagement)
Triplanar Stability and Micromotion Resistance
Another major advantage is triplanar resistance, meaning the implant resists movement in three planes:
- Rotational
- Translational
- Shear forces
Why is this important?
Micromotion at the fusion site is one of the biggest obstacles to successful bone healing. Excessive movement can:
- Delay or prevent fusion
- Lead to implant failure
- Prolong patient pain
By creating a self-constrained, triplanar construct, the transverse transfixing approach significantly reduces micromotion, giving the body a better chance to form solid bone across the joint.
Enhanced Fusion Potential: Cortical + Cancellous Integration
Fusion success depends on the body’s ability to grow bone across the joint space. This process benefits from:
- Stability
- Blood supply
- Bone-to-bone contact
This technique enhances both:
Cancellous Bone Contribution
- Provides a biologically active environment
- Supports early bone growth
Cortical Bone Contribution
- Offers structural strength
- Maintains long-term stability
Because the implant engages both types of bone—and adds direct anterior cortical contact—it creates an ideal environment for fusion.
Procedural Safety and Precision
According to the publication , the postero-inferior approach also offers a safer surgical corridor compared to traditional lateral techniques.
Benefits include:
- Reduced risk of nerve injury
- Lower chance of breaching critical structures
- More predictable anatomical landmarks
Additionally, the implant is positioned near the natural axis of rotation of the sacrum, which helps distribute mechanical forces more efficiently.
The Trade-Off: Technical Precision Required
While the biomechanical advantages are compelling, this technique is not without challenges.
The primary limitation is technical execution:
- The trajectory must be highly accurate
- The surgeon must successfully “hit” the anterior boomerang cortical surface
- Imaging guidance and experience are critical
If the trajectory is off, the full mechanical benefits may not be realized.
In other words, this is a high-reward, precision-dependent technique.
Why This Technique Stands Out
When executed correctly, the transverse posterior transfixing SI joint fusion approach offers several key advantages:
- Stronger fixation through multiple cortical anchors
- Improved stability via triplanar resistance
- Enhanced fusion potential through combined bone engagement
- Reduced micromotion, promoting faster healing
- Better use of natural anatomy, especially the anterior SI joint
Compared to traditional approaches, it represents a shift toward biomechanically optimized fusion rather than simply achieving joint fixation.
Final Thoughts
Dr. Hubbell’s publication highlights an important evolution in SI joint fusion techniques. By leveraging both anatomy and biomechanics, the transverse posterior transfixing approach provides a compelling argument for improved outcomes—particularly in terms of stability and fusion success.
While the technique requires precision and expertise, its potential benefits are significant. As more clinical data becomes available, this method may continue to shape the future of minimally invasive SI joint fusion.
For patients struggling with chronic SI joint pain, advancements like this represent meaningful progress toward more reliable, long-lasting relief.