Intradiscal pressure in the degenerated porcine intervertebral disc

Abstract

Measuring intradiscal pressure is one way of mechanically assessing the discs degenerative state. In this study, the load-bearing capacity of degenerated and their adjacent lumbar intervertebral discs was evaluated using two different injury models. Seventeen adolescent pigs were divided into two groups, an annulus injury group and an endplate injury group. The annulus injury group was subjected to a stab incision in the L3-L4 disc, whereas the endplate injury group received a cranial endplate perforation of the L4 vertebral body. Both groups were biomechanically evaluated three months later using a miniaturized servohydraulic testing machine across L2-L4 and with two pressure needles inserted into the nucleus pulposus of the L2-L3 and L3-L4 discs. Linear relationships between the intradiscal pressure and the applied load were determined within the load range studied. When comparing the ratio of the injured to the adjacent disc pressure, the endplate injury was lower (mean value 0.31) than the annulus injury (mean value 0.51). The pressures in the discs adjacent to the degenerated level were found to be slightly higher. This increase can be expected due to a redistribution in mobility demands in segments adjacent to those with increased stiffness, i.e. degenerated intervertebral discs.

Factors affecting intradiscal pressure measurement during in vitro biomechanical tests

“…The results are in good agreement with the literature [ 6 ]. The amplitude of IDP was considered normal for the specimens and the test applied.…”

Dynamic Biomechanical Examination of the Lumbar Spine With Implanted Total Disc Replacement Using a Pendulum Testing System

“…This study did not assess the level of disc degeneration of the intact FSUs. Significant degeneration of the disc and facet joints affects FSU stiffness 33 , thus it is difficult to assess if the TDR in this study mimicked healthy or degenerated FSUs. Furthermore, this lack of degeneration assessment may have led to the discrepancy between stiffness values between this investigation and the first pendulum investigation.…”

“…Presumably, this can be accomplished through replication of intact FSU stiffness and motion parameters, although this effect has yet to be clinically proven 1,31,32 . Holm et al examined intradiscal pressure in a pig model of disc injury, and found increasing intradiscal pressure at discs adjacent to injured levels, presumable due to increasing stiffness at the injured disc 33 . This makes intuitive sense that a FSU with greater stiffness will cause increasing stress on adjacent levels.…”

Penetrating Annulus Fibrosus Injuries Affect Dynamic Compressive Behaviors of the Intervertebral Disc Via Altered Fluid Flow: An Analytical Interpretation

“…This implies that changes in fluid pressurization under load have a large effect on compressive mechanics following injury. The concept that puncture injuries predominantly affect IVD pressurization is supported by studies showing IVD height loss following needle puncture and decreased intradiscal pressure following midplane tears only when the injury fully penetrated the annulus [1,7]. Direct measurements of intradiscal pressure during injection show a decrease in disc rupture pressure with increasing needle size with a decrease in sensitivity at larger needle sizes [8].…”