Innervation Patterns of the Anterior and Posterior Ligamentous Region of the Sacroiliac Joint: Insights from a Cadaveric Study.

Abstract

Background: In addition to the sacroiliac joint (SIJ) itself, the anterior and posterior ligaments of the SIJ are also sources of pain in the SIJ complex. Nevertheless, detailed descriptions of the nerves that supply the anterior and posterior ligamentous areas of the SIJ are lacking in the literature.

Objectives: The purpose of this study was to examine the anatomical characteristics of the lumbar and sacral nerve branches, which are primarily responsible for the pain signal pathway in the SIJ complex and are distributed within the anterior and posterior ligaments of the SIJ.

Study design: A dissection-based study of 10 embalmed human cadavers.

Setting: The research took place at Central Hospital of Dalian University of Technology.

Methods: A total of 20 SIJs were examined in this study. The research focused on measuring the angles formed by the lateral branches of the ventral ramus of L4-L5 and the vertical axis, as well as the angles formed by the lateral branches of the posterior ramus of S1-S4 and the vertical axis. The distance from the lateral branches of the sacral posterior ramus to the posterior median line, specifically at a point 8 mm away from the edge of the posterior sacral foramen (PSFs), was also measured.

Results: The angles formed by the lateral branches of the ventral ramus of L4-L5 and the vertical axis were measured to be 43° ± 6° and 25° ± 2°, respectively. Similarly, the angles formed by the lateral branches of the posterior ramus of S1-S4 and the vertical axis were found to be approximately 39° ± 6°, 48° ± 12°, 43° ± 12°, and 44° ± 6°, respectively. At a distance of 8 mm from the PSFs, the distances from the lateral branches of the sacral posterior ramus to the posterior median line were approximately 20-30 mm.

Limitations: The study is subject to certain constraints, including the utilization of preserved specimens that may have resulted inadvertently in damage to the lateral branches of the sacral ventral ramus during anatomical dissections. Furthermore, the study was limited by a small sample size and difficulties in controlling the movement of nerve fibers during data collection.

Conclusions: In the event that the lateral branch capture rate of the perioral bipolar leapfrog technique attains 100%, it is imperative to delineate bipolar lesions in the superolateral and inferolateral quadrants of each PSF. Moreover, when employing the lateral pathway of the PSFs for lateral branch radiofrequency ablation (RFA), it is recommended that the radiofrequency (RF) needles be positioned at a minimum distance of 30 mm from the posterior midline to mitigate the risk of inadvertent thermal injury to the spinal nerves. The lateral branches of the lumbar posterior ramus should also be denervated during the RFA. If the patient's pain symptoms are still not effectively relieved after completing the above treatment, surgeons may use intra-articular injections to alleviate factors originating from an anterior source.