Abstract

Pathogenesis of Lumbar Disc Disease: Although the exact pathogenesis is unknown, the patho-etiologies of degenerative disc disease involve genetic, biomechanical, and biological factors. The intervertebral disc consists of outer annulus fibrosus (AF), which is rich in collagens that accounts for its tensile strength, and inner nucleus pulposus (NP), which contains large proteoglycans and water for resisting compression loading. The chondrocyte-like cells in inner AF and NP produce matrices under the control of a variety of substances including growth factors and bone morphogenetic proteins (BMPs). Catabolic process or breakdown of the matrix is mediated by various matrix metalloproteinases (MMPs) and cytokines. There is balance between the anabolic and catabolic processes in the normal disc, but this balance is lost in degenerating discs. The intervertebral disc also requires nutrition, mainly by diffusion from the vertebral bodies and endplates. Therefore, trauma, cigarette smoking, and other factors that affect the endplates may affect diffusion and affect nutrition to the disc cells. The aging and degenerative changes in the intervertebral disc affects the facets joints and the kinematics of the motion segment changes that could be detected with novel imaging studies and motion preservation devices could be used to restrict or maintain motion in certain directions. It should be emphasized that pain is not necessarily correlated with morphologic or biomechanical changes in the motion segment, and further studies are needed to elucidate the mechanism of pain in degenerative disc disease.Emerging Novel treatments of Lumbar Disc Degeneration: Current treatments of low-back-pain due to disc/facet degeneration include fusion, artificial disc, and perhaps intradiscal electrothermal therapy (IDET) in patients who have failed months of conservative treatment. Emerging novel treatments include posterior motion preservation procedures, artificial nucleus pulposus, and biological intradiscal injections that are not FDA approved but undergoing clinical trials. Artificial nucleus pulposus may have indications in which the annulus and posterior facets are intact in the relatively early stage of disc degeneration. Even though many posterior motion preservation devices are being developed at present, lack of knowledge in the relationship among kinematics, spondylosis and pain is a significant hurdle in treating mechanical LBP with these types of devices. Biological repair or regeneration is feasible by injecting a growth factor or BMP such as OP-1 or GDF-5 or blocking cytokines such as TNF-a or IL-1 that are involved in matrix degradation. Alternatively, transplanting stem cells, chondrocytic cells or cells that are transfected with therapeutic DNAs by viral or non-viral gene therapy have shown some promise. These therapies could restore the degenerated disc but effect on pain relief is not known. Further research on pathogenesis of IVD degeneration and pain mechanism should also be considered.