The treatment of sacral insufficiency fractures remains an area of active investigation and development, which has typically concentrated on the lateral elements of the sacrum and the sacral ala. Although these fractures frequently involve the first sacral (S1) vertebral body, this structure has eluded a successful technique to accurately access its central portion for percutaneous cannula placement and cement delivery.
In this article, we describe a percutaneous cannula placement technique developed in cadaver models, utilizing fluoroscopic imaging to enter the S1 vertebral body using a transpedicular approach. The pedicle provides an anatomically safe entry point, but limits the cannula trajectory to the lateral aspect of the S1 vertebral body, which makes delivery of poly(methyl methacrylate) (PMMA) cement to the central body of S1 difficult and unreliable by cannula placement alone. To access the central body of S1 we describe the application of the AVAflex curved nitinol needle, which can be readily directed though the cannula, previously placed through the S1 pedicle, into the central body of S1. The PMMA cement is delivered through the AVAflex needle under fluoroscopic monitoring and results in controlled deposition and good distribution within the central body of S1. The technique employs an extreme caudad angulation of the fluoroscope image intensifier that provides excellent visualization of the sacral spinal canal similar to that obtained with an axial view under CT scan. This view allows for improving transpedicular cannula placement at S1, and real-time fluoroscopic monitoring of the cement deposition to quickly detect and avert possible extravasation toward the central spinal canal. This technique can be used with CT guidance for cannula placement combined with fluoroscopy for cement deposition or done entirely under fluoroscopy alone. Sacroplasty of the lateral sacral element and sacral ala may also be performed at the same time as the S1 vertebroplasty. It appears that with this curved nitinol needle technique, sacral insufficiency fractures that involve the S1 vertebral body may now be safely and accurately addressed.
Conclusion: The treatment of sacral insufficiency fractures by sacroplasty remains an evolving field. The technique using the curved AVAflex nitinol needle is another way to address the S1 component.