Biomedical subjects

K B Broberg

Publications and source records attributed to K B Broberg.

3 recordsLinked to original sources

PubMed1983

On the mechanical behaviour of intervertebral discs.

The response to compression, shear, bending, and axial rotation of an intervertebral disc is studied by using a theoretical disc model. The annulus fibrosus is modelled by ten fibre layers with alternating fibre inclination. The nucleus pulposus as well as the substance filing the space between the fibre layers is assumed to consist of an incompressible fluid. The end-plates are assumed to bulge at action of the pressure in the fluid phase. Geometry of fibre layers and end-plates are chosen to agree as closely as possible with what is representative for lumbar discs. The results show considerable increase of the different stiffnesses at increasing levels of the axial load. They also show quite large fibre strains, well over 10% at motions within normal physiological limits.

Biomechanical Phenomena↗

PubMedDate not supplied

Slow deformation of intervertebral discs.

Intervertebral discs exhibit pronounced time-dependent deformations when subjected to load variations. These deformations are caused by fluid flow to and from the disc and by viscoelastic deformation of annulus fibres. The fluid flow is caused by differences between mechanical and osmotic pressure. A mechanical model of lumbar disc functions allows one to calculate both the extent of fluid flow and its implications for disc height as well as the role played by viscoelastic deformation of annulus fibres. From such calculations changes in body height are estimated. Experimental results already documented in the literature offer bases for the determination of the parameters involved. Body height variations are studied, both those related to normal diurnal rhythmicity and those related to somewhat exceptional circumstances. The normal diurnal fluid flow is found to be about +/- 40% of the disc fluid content late in the evening. Viscoelastic deformation of annulus fibres contributes approximately one quarter of the height change obtained after several hours normal activity, but dominates during the first hour.

Adult↗

PubMedDate not supplied

Modeling of intervertebral discs.

A model with rotational symmetry of an intervertebral disc is studied. The nucleus pulposus is assumed to consist of an incompressible fluid, and the annulus fibrosus is modeled by 11 fiber layers with alternating fiber inclination. The spaces between the fiber layers are assumed to be filled with an incompressible fluid. The pressures in the fluid compartments, the fiber strains, and the bulge are calculated under different assumptions regarding fiber inclination, fiber force-elongation relation, initial fiber layer bulges, and so on. The agreement with experimental results is very good. Possible extensions of the model are briefly discussed.

Biomechanical Phenomena↗