Exploring the regional disc bulge response of the cervical porcine intervertebral disc under varying loads and posture.
Nerve compression due to intervertebral disc (IVD) bulging is a known mechanism for low back pain and typically occurs in the posterior region of the disc. Most in vitro studies are limited in the ability to quantify the magnitude of bulging on the posterior aspect of the disc due to the boney structures that occlude a direct line-of-sight in the intact functional spinal units (FSUs). This study examined anterior and posterior annulus fibrosus (AF) bulges in reduced (posterior elements removed) cervical porcine specimens across four loading conditions and two postures. Surface scans from the anterior and posterior aspect of the IVD were recorded in both neutral and flexed postures using a 3D laser scanner to characterize changes in AF bulge. A significant negative correlation was observed for peak AF bulge on the anterior and posterior side of the disc in a flexed posture (Pearson's r = -0.448; p = 0.002; r2 = 0.2003). The results from this investigation support that there may be a connection between the magnitude of AF bulge on the posterior side and estimations computed using the anterior side.