Sacroiliac joint involvement in activation of the porcine spinal and gluteal musculature

In the search for causes of low back pain, the sacroiliac joint has gained renewed interest as a possible pain generator. There is reason to believe t hat the sacroiliac joint plays a regulatory role involving reflex muscle ac tivation, which controls trunk mobility and stability, as well as locomotio n. The aim of this experimental study was to determine whether stimulation of nerves in the sacroiliac joint and joint capsule could elicit contractio ns in porcine gluteal or lumbar spinal muscles. Via a lateral retroperitone al approach and using hypodermic needles, bipolar stimulating wire electrod es were inserted into the ventral area of the sacroiliac joint and directly under the surface of the capsular membrane, in 10 adolescent pigs (45 kg). This procedure was performed bilaterally, thus establishing two bilateral stimulation sites in the joints. Six electromyographic electrodes were unil aterally inserted into the following muscles: multifidus, gluteus medius, g luteus maximus, and quadratus lumborum. On stimulation within the ventral a rea of the joint, predominant responses occurred in both the gluteus maximu s and quadratus lumborum muscles. However, when stimulating the capsule, th e greatest muscular responses were detected in the multifidus muscles. This study addressed the possible regulatory function of the sacroiliac joint, namely, its involvement in activation of the spinal and gluteal muscles, wh ich help control locomotion and body posture, as well as provide stability on the segmental level in the lumbar spine.