11/19/2022
Possible mechanisms of pain from a degenerative disc 🧐
Role of Inflammation 🔥 in Lumbar Pain
👉 Degenerated discs exhibit abnormally widespread innervation with sensory nerve fibres penetrating deep into the nucleus pulposus [https://pubmed.ncbi.nlm.nih.gov/17905946/, https://pubmed.ncbi.nlm.nih.gov/9250186/]. Most discs with positive pain provocation on discography show radial fissures within the annulus [https://pubmed.ncbi.nlm.nih.gov/3589823/].
👉 The process of disc degeneration produces an inflammatory response, generated by cells within the nucleus pulposus, where multiple inflammatory factors are released. Histologic studies reveal ingrowth of vascularized granulation tissue along the annular fissures [https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8185559/].
👉 Immunohistochemical analyses have demonstrated cytokine-sensitized nociceptors, phagocytic cells, and perivascular neoinnervation (axono-genesis). Small, free nerve fibres may be found in the outer annulus and extend to the inner annulus and nucleus pulposus [https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8185559/, https://www.sciencedirect.com/science/article/pii/S1063458420311407].
👉 Nerve fibres in the disc may contain nociceptive neurotransmitters, such as substance P, calcitonin gene-related peptide, and vasoactive intestinal peptide. These inflammatory factors migrate through fissures into the outer third of the annulus or into the endplate, where stimulation of free nerve endings results in nociception and potentially pain [https://pubmed.ncbi.nlm.nih.gov/15686239/]. The degenerating discs thus exhibit free nerve endings (nociceptors) and inflammation, which are contributing factors to a potential pain response [https://onlinelibrary.wiley.com/doi/full/10.1002/jsp2.1196].
📙 Illustration: Calodney, A., Vest, A.T. (2023). Discography. In: Hunter, C.W., Davis, T. T., DePalma, M.J. (eds) Regenerative Medicine . Springer, Cham. https://doi.org/10.1007/978-3-030-75517-1_16
