Intervertebral disc degeneration: evidence for two distinct phenotypes

Abstract

We review the evidence that there are two types of disc degeneration. 'Endplate-driven' disc degeneration involves endplate defects and inwards collapse of the annulus, has a high heritability, mostly affects discs in the upper lumbar and thoracic spine, often starts to develop before age 30 years, usually leads to moderate back pain, and is associated with compressive injuries such as a fall on the buttocks. 'Annulus-driven' disc degeneration involves a radial fissure and/or a disc prolapse, has a low heritability, mostly affects discs in the lower lumbar spine, develops progressively after age 30 years, usually leads to severe back pain and sciatica, and is associated with repetitive bending and lifting. The structural defects which initiate the two processes both act to decompress the disc nucleus, making it less likely that the other defect could occur subsequently, and in this sense the two disc degeneration phenotypes can be viewed as distinct.

DISC (Degenerate-disc Infection Study With Contaminant Control)

“…Many theories have been proposed as to the etiology of disc degeneration: mechanical, chemical, and recently bacterial. 1,8,9 The organisms implicated are low virulent organisms like P. acnes which generally reside as skin commensals. Possible mechanisms as to their involvement include regular bacteremia from brushing, bowel movements, and others, 10 and the fact that the nucleus pulposus lacks vascular supply and the necrotic tissue due to degeneration is a good medium for proliferation of organisms.…”

“…Risk factors for degeneration include age, hereditary, smoking, and mechanical causes including lifting heavy weights. 1 Correlation between magnetic resonance imaging (MRI) scan findings of degenerate disc and back pain is poor although a few features like Modic changes (MC) can be suggestive. 1,2 Radicular symptoms are often related to the prolapsed disc compressing on the nerve root; however, it is not uncommon to find discrepancy between degree of prolapsed disc and pain severity.…”

Effects of resting modes on human lumbar spines with different levels of degenerated intervertebral discs: a finite element investigation

“…In this process, fluid flow, which causes variations in disc height and proteoglycans content, is an important step [1][2][3]. However, intervertebral discs often suffer from degeneration because of aging and poor working environment, and it could be other plausible reasons for disc degeneration, such as genetic inheritance, inadequate metabolite transport, and loading history, which may directly change the normal hydrated environment and fluid flow and indirectly result in instability and reduction of the carrying capacity [1,[4][5][6]. Thus, investigating the changes of biomechanical parameters for different degrees of disc degeneration to explore relevant mechanism of disc degeneration and search for effective treatment strategies has significant value.…”

The biology behind the human intervertebral disc and its endplates

“…Individual genes associated with IVD degeneration include those for type IX collagen, aggrecan, vitamin D receptor, alkaline phosphatase, matrix metalloproteinase (MMP)-3, and cartilage intermediate layer protein [1,4,39,54,80,84]. The products of these genes probably affect the strength of skeletal tissues, and their systemic effects may explain why IVD degeneration is more prevalent in those with osteoarthritis [33].…”

“…Adams and Dolan [1] have brought to light that there exist two distinct types of IVD degeneration -"endplate-driven" involving endplate defects and inward collapse of the AF and "annulus-driven" involving a radial fissure and/or an IVD prolapse. The structural defects which initiate the two processes both act to decompress the NP, making it less likely that the other defect could occur subsequently.…”