Static axial overloading primes lumbar caprine intervertebral discs for posterior herniation

Abstract

IntroductionLumbar hernias occur mostly in the posterolateral region of IVDs and mechanical loading is an important risk factor. Studies show that dynamic and static overloading affect the nucleus and annulus of the IVD differently. We hypothesize there is also variance in the effect of overloading on the IVD’s anterior, lateral and posterior annulus, which could explain the predilection of herniations in the posterolateral region. We assessed the regional mechanical and cellular responses of lumbar caprine discs to dynamic and static overloading.Material and methodsIVDs (n = 125) were cultured in a bioreactor and subjected to simulated-physiological loading (SPL), high dynamic (HD), or high static (HS) overloading. The effect of loading was determined in five disc regions: nucleus, inner-annulus and anterior, lateral and posterior outer-annulus. IVD height loss and external pressure transfer during loading were measured, cell viability was mapped and quantified, and matrix integrity was assessed.ResultsDuring culture, overloaded IVDs lost a significant amount of height, yet the distribution of axial pressure remained unchanged. HD loading caused cell death and disruption of matrix in all IVD regions, whereas HS loading particularly affected cell viability and matrix integrity in the posterior region of the outer annulus.ConclusionAxial overloading is detrimental to the lumbar IVD. Static overloading affects the posterior annulus more strongly, while the nucleus is relatively spared. Hence, static overloading predisposes the disc for posterior herniation. These findings could have implications for working conditions, in particular of sedentary occupations, and the design of interventions aimed at prevention and treatment of early intervertebral disc degeneration.

Quantitative MRI in early intervertebral disc degeneration: T1rho correlates better than T2 and ADC with biomechanics, histology and matrix content

“…This could potentially exacerbate the effects of Cabc-induced degeneration or diminish water-content loss under axial compression in degenerative discs. We observe a slightly higher overall water-content (76–89%) in the IVDs when compared to data from our previous reports (70–85%) [ 46 , 49 , 50 ]. However, we can still quantify T2 and water-content differences between the experimental groups, which refutes the latter.…”

“…We quantitatively mapped the IVD’s 5 distinct regions on T2, T1rho, and ADC images and found significant differences between the nucleus, inner-annulus, and the anterior, lateral and posterior outer-annulus. These regions have previously been described to be distinct on histological appearance, as well as their biochemical composition of the matrix in both human and caprine IVDs [ 46 , 49 , 50 , 62 – 65 ]. The current baseline MR values found for these IVD regions closely resemble values found in similar regional measurements of human lumbar discs [ 66 – 70 ].…”

“…If an IVD had any degenerative changes or aberrancies it was excluded. Mid-lumbar disc levels L2-L3, L3-L4 and L4-L5 (n = 24 total) were used in the culture experiments, as these disc levels do not significantly differ in height, size, mechanical properties or matrix content [ 46 , 49 – 51 ]. Still, all experimental groups had an equal distribution of disc levels.…”

“…This is a descriptive histological score that quantifies degenerative changes in the NP, AF and endplate using both transverse and sagittal sections. On a continuous scale, 0–2 signifies a healthy non-degenerated disc, 3–5 mild degeneration, 6–8 moderate degeneration, 9–11 severe degeneration, and a score of 12–15 being completely degenerated [ 46 , 61 ].…”

A narrative review of non-operative treatment, especially traditional Chinese medicine therapy, for lumbar intervertebral disc herniation

“…At the onset or acute phase of LIDH, 1-2 weeks of bed rest will be recommended for patients with severe pain (16). It is reported that the pressure on intervertebral discs is related to the patients' position and varies with body positions with the highest in sitting position and the lowest in recumbent position (17). When resting in bed, the pressure on intervertebral disc is reduced, which will be a benefit for removing tension of surrounding soft tissues, and restoring the biomechanical balance of the intervertebral disc?…”