Poroelastic modeling of the intervertebral disc: A path toward integrated studies of tissue biophysics and organ degeneration

Lumbar intervertebral disc (IVD) degeneration is the leading cause of lower back pain. While lumbar IVDs have low cellularity and limited capacity of regeneration, they bear high mechanical loads. Accelerated disc degeneration may happen because of undue cell stimulation, and cell nutrition also seems to be particularly influent in the disc. Cell nutrition depends on exchange of oxygen, glucose, and lactate between the periphery and the various regions of the IVD, which in turn depends on mechanical deformations. The mechanical regulation of disc cell nutrition, known as indirect mechanotransduction, is difficult to study in vivo or in vitro. This review reports on an important alternative in the form of numerical methods, which are based on the ability of poromechanical models to be coupled to solute transport-reaction models. Models need to address intricate nonlinear and time-dependent phenomena, but have allowed for important mechanisms to be proposed, complementing current knowledge gained from in vivo or in vitro observations.