The dynamic response of L2/L3 motion segment in cyclic axial compressive loading
Journal
Clinical Biomechanics
Journal Volume
13
Journal Issue
SUPPL. 1
Date Issued
1998
Author(s)
Abstract
Objective. The dynamic response and load sharing amongst passive elements of an L2-L3 motion segment during axial compressive cyclic loading was investigated. Design. A validated viscoelastic nonlinear finite element model of L2-L3 was used for a detailed stress/strain analysis during axial cyclic loading. Background. The repetitive loading of the spine has been implicated as a risk factor in developing low back disorders. However, the quantitative description of injury mechanisms and the internal load sharing have been lacking. Methods. The applied cyclic axial compressive loading was controlled, peak to peak, from 600 to 1000 N at 0.5 Hz for 15 cycles. The stress/strain and strain energy density of various elements were quantified and the effects of cyclic loading on these parameters were investigated. Results. The axial stiffness of the motion segment decreased, while intradiscal pressure (IDP) and the strain in anulus fibers of the outermost lamella increased. The axial stresses of outer lamellae in the anulus matrix reduced, in contrast to the increased strain at the endplate. Conclusions. The load sharing amongst the passive elements of the motion segment changed. The response of the motion segment to the same external axial load depends on the history of loading. The anulus fibers in the innermost layer were slack due to compression, hence not at risk of failure. The loss of disc height and increased disc bulge led to higher strain in anulus fibers of outermost layer. In future, more complex loading conditions with a longer duration should be considered. Relevance. The short-term cyclic axial loading has caused loss of axial stiffness and higher stress gradient within the disc. It is suggested that the sustained cyclic loading may lead to endplate failure and disruption of the disc, in agreement with clinical and epidemiological studies. The loss of stability due to cyclic loading and exacerabation of pain in chronic low back patients during driving warrants further studies. The role of redistribution of load in the remodeling and accumulation of micro failure should be explored. The dynamic response and load sharing amongst passive elements of an L2-L3 motion segment during axial compressive cyclic loading was investigated. A validated viscoelastic nonlinear finite element model of L2-L3 was used for a detailed stress/strain analysis during axial cyclic loading. The repetitive loading of the spine has been implicated as a risk factor in developing low back disorders. However, the quantitative description of injury mechanisms and the internal load sharing have been lacking. The applied cyclic axial compressive loading was controlled, peak to peak, from 600 to 1000 N at 0.5 Hz for 15 cycles. The stress/strain and strain energy density of various elements were quantified and the effects of cyclic loading on these parameters were investigated. The axial stiffness of the motion segment decreased, while intradiscal pressure (IDP) and the strain in anulus fibers of the outermost lamella increased. The axial stresses of outer lamellae in the anulus matrix reduced, in contrast to the increased strain at the endplate. The load sharing amongst the passive elements of the motion segment changed. The response of the motion segment to the same external axial load depends on the history of loading. The anulus fibers in the innermost layer were slack due to compression, hence not at risk of failure. The loss of disc height and increased disc bulge led to higher strain in anulus fibers of outermost layer. In future, more complex loading conditions with a longer duration should be considered.
SDGs
Type
conference paper