The pathogenesis of discogenic low back pain

Area of Science:

• Spinal research
• Pain pathogenesis
• Histopathology

Background:

• Discogenic low back pain is a prevalent cause of disability.
• The underlying mechanisms of discogenic pain remain incompletely understood.
• Understanding disc pathology is crucial for developing effective treatments.

Purpose of the Study:

• To investigate the histological characteristics of painful intervertebral discs.
• To assess the presence and extent of nerve fibers and neuropeptides in symptomatic discs.
• To correlate histological findings with the pathogenesis of discogenic low back pain.

Main Methods:

• Collection of lumbar intervertebral disc specimens from patients undergoing surgery and controls.
• Histological examination to identify tissue changes.
• Immunohistochemical analysis for neurofilament (NF200), substance P (SP), and vasoactive-intestinal peptide (VIP).

Main Results:

• Painful discs exhibited a distinct zone of vascularized granulation tissue extending from the nucleus pulposus to the annulus fibrosus.
• Significantly increased SP-, NF-, and VIP-immunoreactive nerve fibers were observed in painful discs compared to controls.
• Nerve ingrowth into the annulus fibrosus and nucleus pulposus occurred primarily along this granulation tissue in symptomatic discs.

Conclusions:

• The formation of granulation tissue along fissures in the posterior disc is a key histological feature of painful discs.
• Extensive innervation within this granulation tissue likely contributes to the pain experienced in discogenic low back pain.
• These findings suggest a mechanism linking disc degeneration, granulation tissue formation, and neuropathic pain signaling.