Porosity and thickness of the vertebral endplate depend on local mechanical loading.
In a recent publication in Spine, a group of researchers looked at the porosity and thickness of the vertebral endplate comparing mechanical stress from adjacent vertebrae to disc degeneration.
Much research has been uncovered regarding what contributes to back pain. Some of the factors were reminded to us in the wonderful introduction to this research paper. Nutrient flow into the discs continue to be one of the hot topics in the cause and prevention of disc degeneration. Vertebral endplates are also important to understand in the realm of back pain because they are innervated by the basivertebral nerve. And modic changes are also known to cause back pain.
The endplate is a .8mm thick layer of hyaline cartilage backed by weakly bonded cortical bone which sandwiches the annulus and nucleus of the intervertebral disc. It is thinnest at the central region at the interface of the nucleus pulposus of the intervertebral disc and thickens to the periphery where the annulus resides. The perforations that contributes to the porosity are mainly at the interface where the nucleus exists. Regarding porosity, the hyaline cartilage is less permeable than cortical bone and therefore plays an important role in generating and maintaining intradiscal pressure to resist compression. But at the same time, the permeability is important for nutrient supply to the disc.
These authors wanted to figure out the role of the porosity of the endplate and whether it is related to thickness or degeneration of the disc.
What the authors concluded was that porosity of the endplates were inversely proportional to the thickness being greatest in the central region. They also found that porosity increased with degeneration but not with age.
What they did interpret from the results was that certain areas of the endplate become thin because of reduced load and as well become more porous primarily because they become thin.
Clinically, this study is important because they showed that the nucleus pressure reduces as intervertebral disc degeneration progresses. This also has implications into vertebral fracture due to bone loss and increased porosity.