Journal of biomechanics
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Journal of biomechanics · Mar 2018
Osmosis and viscoelasticity both contribute to time-dependent behaviour of the intervertebral disc under compressive load: A caprine in vitro study.
The mechanical behaviour of the intervertebral disc highly depends on the content and transport of interstitial fluid. It is unknown, however, to what extent the time-dependent behaviour can be attributed to osmosis. Here we investigate the effect of both mechanical and osmotic loading on water content, nucleus pressure and disc height. ⋯ This shows that annulus water content is important in the response to axial loading. After unloading, in the absence of an osmotic gradient, there was substantial viscoelastic recovery of 53(±11)% of the disc height, without a change in water content. However, for restoration of the nucleus pressure and for full restoration of disc height, restoration of the osmotic gradient was needed.
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Journal of biomechanics · Mar 2018
Are axial intervertebral disc biomechanics determined by osmosis?
The intervertebral disc faces high compressive forces during daily activities. Axial compression induces creeping fluid loss and reduction in disc height. With degeneration, disc fluids and height are progressively lost, altering biomechanics. ⋯ Reduction of water content and amplitude of creep and recovery showed similarity to degenerative disc biomechanics. However, the time-constants increased, indicating that the hydraulic permeability was reduced, in contrast to what happens with degeneration. This suggests that besides the osmotic gradient, the permeability of the tissues determines healthy intervertebral disc biomechanics.
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Journal of biomechanics · Mar 2018
Three-dimensional primary and coupled range of motions and movement coordination of the pelvis, lumbar and thoracic spine in standing posture using inertial tracking device.
Evaluation of spinal range of motions (RoMs) and movement coordination between its segments (thorax, lumbar, and pelvis) has clinical and biomechanical implications. Previous studies have not recorded three-dimensional primary/coupled motions of all spinal segments simultaneously. Moreover, magnitude/direction of the coupled motions of the thorax/pelvis in standing posture and lumbopelvic rhythms in the frontal/transverse planes have not been investigated. ⋯ The spine had different primary RoMs in different planes/directions (flexion: lumbar: 55.4 ± 12.4°, pelvis: 42.8 ± 21.6°, and T1-T12 thoracic: 19.9 ± 6.4°, extension: lumbar: 23.4 ± 10.1°, thoracic: 11.7 ± 3.4°, and pelvis: 10.2 ± 6.4°, left/right lateral bending: thoracic: 24.5 ± 7.4°/26.5 ± 6.1°, lumbar: 16.4 ± 7.2°/18.3 ± 5.7°, and pelvis: 11.0 ± 4.4°/9.3 ± 6.2°, and left/right axial rotation: thoracic: 33.5 ± 10.0°/37.1 ± 11.7°, pelvis: 31.6 ± 12.5°/27.2 ± 12.0° and lumbar: 7.5 ± 4.5°/9.2 ± 7.3°). Pelvis, lumbar and thoracic spine had different/varying contributions/rhythms to generate total trunk (T1) movement, both within and between planes. Pattern of the coupled motions was inconsistent between subjects but side bending was generally associated with twisting to the same side at the thoracic spine and to the opposite side at the lumbar spine.