Intervertebral disc degeneration

Intervertebral disc (IVD) degeneration is a naturally occurring process that is a consequence of biological ageing and exposure to normal physiological loading over a lifetime and is characterized by loss of IVD tissue structural integrity. The nucleus pulposus changes with loss of pressurization, decreased collagen concentration and loss of distinction from annulus fibrosus. The annulus fibrosus and cartilaginous endplate suffer delamination, tears, fractures and clefts of their respective extracellular matrix at both microscopic and macroscopic scales. This loss of structural integrity generally follows a predictable pattern of degeneration, and it predisposes the IVD to pathological states. As the disc degenerates, the likelihood of functional failure to protect the neural elements and/or to provide stable spine motion and support increases. Functional failure takes the degenerated IVD to a state of disc pathology that has various phenotypes: the most common forms are disc herniation, mechanical instability, spinal stenosis, degenerative spondylolisthesis and degenerative scoliosis. IVD pathology is commonly self-limited and non-operative treatment remains the mainstay of treatment in most patients. For patients with refractory disease, surgical intervention focuses on neural decompression and, when indicated, motion segment stabilization. Future therapies for prevention of disc degeneration, targeted disc regeneration and biological modification of the degenerative cascade might prevent or reverse pathological changes across all spinal regions.