Low back pain associated with lumbar disc herniation: role of moderately degenerative disc and annulus fibrous tears

Abstract

Lumbar disc herniation is one of the most common spinal degenerative disorders which may lead to low back pain (LBP) and radicular leg pain. However, it remains difficult to diagnose a degenerative herniated disc as the LBP generator in clinical practice. The purpose of this study is to explore the characteristic changes of a herniated disc causing LBP on MRI and to clarify the underlying role of inflammatory mediators and annulus fibrous (AF) tears in LBP generation associated with disc herniation. We prospectively collected intervertebral disc specimens and MRI from 57 single-segment disc herniation patients with radiculopathy. All subjects were grouped according to LBP occurrence or disc degeneration severity for the comparison of inflammatory mediators' expression and AF tears occurrence (High Intensity Zone, HIZ, on MRI). LBP incidence under circumstances of different degeneration severity with or without HIZ was further analyzed. Both LBP incidence and Inflammatory mediators expression in moderately degenerated group was higher than mildly and severely degenerative groups. HIZ incidence was higher in moderately and severely degenerated groups. LBP incidence in the patients with both moderately degenerated discs and HIZ was 86.7%, much higher than the rest of the patient population. In conclusion, the high expression of inflammatory mediators with AF tears causes LBP associated with disc herniation. Moderately degenerative disc with HIZ is MRI morphological change of herniated disc causing LBP, which can be applied to diagnose LBP.

Keywords: Low back pain; annulus fibrous tear; high intensity zone; inflammatory cytokine; lumbar disc herniation.

Figure 1

LBP incidence in moderately degenerated disc was higher than those in mildly and severely degenerated disc (P < 0.05).

Figure 2

The inflammatory mediators expression in moderately degenerated disc was the highest for IL-1β, TNF-α, iNOS and Substance P (P < 0.05), bar = 100 um. Mil: Mild, Mod: Moderate, Sev: Severe.

Figure 3

The mRNA level in moderately degenerated disc was the highest for IL-1β, TNF-α, iNOS and Substance P (P < 0.05).

Figure 4

The inflammatory mediators expression difference between LBP (+) and LBP (-) for IL-1β, TNF-α, iNOS and Substance P did not reach significance (P > 0.05), bar = 100 um.

Figure 5

The mRNA level difference between LBP (+) and LBP (-) for IL-1β, TNF-α, iNOS and Substance P did not reach significance (P > 0.05).

Figure 6

HIZ incidence in moderately and severely degenerated discs were higher than that in mildly degenerated disc (P < 0.05).

Figure 7

LBP incidence in HIZ (+) was higher than that in HIZ (-) (P < 0.05).

Figure 8

LBP incidence was significantly higher in the group with both moderately degenerated discs and HIZ than those in the other groups (P < 0.05).

Figure 9

Three representative MRI scan imaging of intervertebral disc protrution patients. A: Severely degenerated disc with HIZ had no LBP. B: Moderately degenerated disc with HIZ had LBP. C: Moderately degenerated disc without HIZ had no LBP.

Figure 10

A typical disc protrusion case performing radiofrequency ablation. A and C: Preoperative MRI scan imaging showed moderate degeneration and HIZ. After radiofrequency ablation, the low back pain patient had pain relief. B and D: After half one year, MRI scan imaging had no obvious changes. But, the patient had no recurrence of LBP.