Three pathways between the sacroiliac joint and neural structures.

BACKGROUND AND PURPOSE Despite ongoing clinical suspicion regarding the relationship between sacroiliac joint (SIJ) dysfunction and lower extremity symptoms, there is a paucity of scientific literature addressing this topic. The purpose of this study was to describe patterns of contrast extravasation during SIJ arthrography and postarthrography CT in patients with lower back pain and to determine whether there are pathways of communication between the SIJ and nearby neural structures. METHODS Fluoroscopically guided SIJ arthrography was performed on 76 SIJs. After the injection of contrast medium, anteroposterior, lateral, and oblique radiographs as well as 5-mm contiguous axial and direct coronal CT images were obtained. Contrast extravasation patterns were recorded for each joint. These observations included a search for contrast extravasation from the SIJ that contacted nearby lumbosacral nerve roots or structures of the plexus. RESULTS Sixty-one percent of all joints studied revealed one of five contrast extravasation patterns. Three of these observed patterns show a pathway of communication between the SIJ and nearby neural structures. These included posterior extravasation into the dorsal sacral foramina, superior recess extravasation at the sacral alar level to the fifth lumbar epiradicular sheath, and ventral extravasation to the lumbosacral plexus. CONCLUSION Three pathways between the SIJ and neural structures exist.