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Mild (not severe) disc degeneration is implicated in the progression of bilateral L5 spondylolysis to spondylolisthesis.

ABSTRACT: Spondylolytic (or lytic) spondylolisthesis is often associated with disc degeneration at the index-level; however, it is not clear if disc degeneration is the cause or the consequence of lytic spondylolisthesis. The main objective of this computed tomography based finite element modelling study was to examine the role of different grades of disc degeneration in the progression of a bilateral L5-lytic defect to spondylolisthesis.High-resolution computed tomography data of the lumbosacral spine from an anonymised healthy male subject (26 years old) were segmented to build a 3D-computational model of an INTACT L1-S1 spine. The INTACT model was manipulated to generate four more models representing a bilateral L5-lytic defect and the following states of the L5-S1 disc: nil degeneration (NOR LYTIC), mild degeneration (M-DEG LYTIC), mild degeneration with 50% disc height collapse (M-DEG-COL LYTIC), and severe degeneration with 50% disc height collapse(S-COL LYTIC). The models were imported into a finite element modelling software for pre-processing, running nonlinear-static solves, and post-processing of the results.Compared with the baseline INTACT model, M-DEG LYTIC model experienced the greatest increase in kinematics (Fx range of motion: 73% ?, Fx intervertebral translation: 53%?), shear stresses in the annulus (Fx anteroposterior: 163%?, Fx posteroanterior: 31%?), and strain in the iliolumbar ligament (Fx: 90%?). The S-COL LYTIC model experienced a decrease in mobility (Fx range of motion: 48%?, Fx intervertebral translation: 69%?) and an increase in normal stresses in the annulus (Fx Tensile: 170%?; Fx Compressive: 397%?). No significant difference in results was noted between M-DEG-COL LYTIC and S-COL LYTIC models.In the presence of a bilateral L5 spondylolytic defect, a mildly degenerate index-level disc experienced greater intervertebral motions and shear stresses compared with a severely degenerate index-level disc in flexion and extension bending motions. Disc height collapse, with or without degenerative changes in the stiffness properties of the disc, is one of the plausible re-stabilisation mechanisms available to the L5-S1 motion segment to mitigate increased intervertebral motions and shear stresses due to a bilateral L5 lytic defect.

SUBMITTER: Ramakrishna VAS

PROVIDER: S-EPMC5879802 | biostudies-other | 2018 Apr

REPOSITORIES: biostudies-other

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Mild (not severe) disc degeneration is implicated in the progression of bilateral L5 spondylolysis to spondylolisthesis.

Ramakrishna Vivek A S VAS Chamoli Uphar U Viglione Luke L LL Tsafnat Naomi N Diwan Ashish D AD

BMC musculoskeletal disorders 20180402 1

<h4>Background</h4>Spondylolytic (or lytic) spondylolisthesis is often associated with disc degeneration at the index-level; however, it is not clear if disc degeneration is the cause or the consequence of lytic spondylolisthesis. The main objective of this computed tomography based finite element modelling study was to examine the role of different grades of disc degeneration in the progression of a bilateral L5-lytic defect to spondylolisthesis.<h4>Methods</h4>High-resolution computed tomograp ...[more]

PMID: 29609581

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Project description:To investigate optic disc hemorrhage (DH)'s clinical implications to subsequent progression of primary open-angle glaucoma (POAG) in cases of mild-to-moderate myopia.Retrospective comparative study.(1) Fifty-nine (59) myopic (26.5 mm > axial length [AXL] ? 24.0 mm) POAG patients with DH and (2) 59 age-, AXL-, and mean deviation (MD) of visual field (VF)-matched controls without DH were evaluated over the course of a minimum 3.5 years of follow up. For clear assessment of the effect of DH on progression of glaucoma, the patients selected for inclusion in the study were those with stable IOP (i.e., those showing an at least 20% reduction relative to the baseline IOP) whose IOP-lowering medication was not increased, supplemented or changed during the follow-up period.The patients' optic disc/retinal nerve fiber layer (RNFL) photographs were independently evaluated by three glaucoma specialists for structural progression of glaucoma. Event-based analysis with Guided Progression Analysis (GPA) software was used to determine their functional progression. The durations of structural and functional progression were compared by Kaplan-Meier life survival analyses.Optic disc/RNFL progression and VF progression.The mean follow-up periods between the DH and non-DH groups were not significantly different: in the DH group, 5.6±2.7 years; in the non-DH group, 5.4±2.6 years (P = 0.588). In the DH group, 30 (50.8%) of 59 eyes manifested optic disc/RNFL deterioration; in the non-DH group, however, only 17 (28.8%) of 59 eyes showed structural progression. For the DH group, the cumulative probability of structural glaucoma progression was significantly greater than for the non-DH group (P = 0.001; log rank test). Interestingly, the two groups did not significantly differ in the cumulative probability of functional progression (P = 0.79; log rank test): in the DH group, VF progression was observed in 14 eyes (23.7%); in the non-DH group, in 12 eyes (20.3%).DH was associated with a greater probability of structural progression in medically well-controlled-IOP POAG eyes with mild-to-moderate myopia. However, the relevance of DH to VF progression was not clear over the course of the average 5.5-year duration of the study.

Dataset Information

Mild (not severe) disc degeneration is implicated in the progression of bilateral L5 spondylolysis to spondylolisthesis.

Publications

Mild (not severe) disc degeneration is implicated in the progression of bilateral L5 spondylolysis to spondylolisthesis.

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