Pathomechanisms of discogenic low back pain in humans and animal models

Abstract

Background context: Although explored in humans and animal models, the pathomechanisms of discogenic low back pain (LBP) remain unknown.

Purpose: The aim of this study was to review the literature about the pathomechanisms of discogenic LBP.

Methods: Animal models of discogenic pain and specimens from degenerated human intervertebral discs (IVDs) have provided clues about the pathomechanisms of discogenic LBP. Painful discs are characterized by a confluence of innervation, inflammation, and mechanical hypermobility. These three possible mechanisms are discussed in this review.

Results: Animal models and specimens from humans have revealed sensory innervation of lumbar IVDs and sensory nerve ingrowth into the inner layer of IVDs. Cytokines such as tumor necrosis factor-α and interleukins induce this ingrowth. Nerve growth factor has also been recently identified as an inducer of ingrowth. Finally, disc degeneration induces several collagenases; their action results in hypermobility and pain.

Conclusions: To treat discogenic LBP, it is important to prevent sensitization of sensory nerve fibers innervating the IVD, to suppress pathogenic increases of cytokines, and to decrease disc hypermobility.

Keywords: Hypermobility; Inflammation; Intervertebral disc; Pain; Psychosocial factors; Sensory nerve.