The anatomy of the lateral branches of the sacral dorsal rami: implications for radiofrequency ablation.

BACKGROUND: The sacroiliac joint (SIJ) is a major source of pain in patients with chronic low back pain. Radiofrequency ablation (RFA) of the lateral branches of the dorsal sacral rami that supply the joint is a treatment option gaining considerable attention. However, the position of the lateral branches (commonly targeted with RFA) is variable and the segmental innervation to the SIJ is not well understood.

OBJECTIVES: Our objective was to clarify the lateral branches' innervation of the SIJ and their specific locations in relation to the dorsal sacral foramina, which are the standard RFA landmark.

METHODS: Dissections and photography of the L5 to S4 sacral dorsal rami were performed on 12 hemipelves from 9 donated cadaveric specimens.

RESULTS: There was a broad range of exit points from the dorsal sacral foramina: ranging from 12:00 - 6:00 position on the right side and 6:00 - 12:00 on the left positions. Nine of 12 of the hemipelves showed anastomosing branches from L5 dorsal rami to the S1 lateral plexus.

LIMITATIONS: The limitations of this study include the use of a posterior approach to the pelvic dissection only, thus discounting any possible nerve contribution to the anterior aspect of the SIJ, as well as the possible destruction of some L5 or sacral dorsal rami branches with the removal of the ligaments and muscles of the low back.

CONCLUSION: Widespread variability of lateral branch exit points from the dorsal sacral foramen and possible contributions from L5 dorsal rami and superior gluteal nerve were disclosed by the current study. Hence, SIJ RFA treatment approaches need to incorporate techniques which address the diverse SIJ innervation.