Pathophysiology, diagnosis, and treatment of discogenic low back pain

Abstract

Discogenic low back pain is a serious medical and social problem, and accounts for 26%-42% of the patients with chronic low back pain. Recent studies found that the pathologic features of discs obtained from the patients with discogenic low back pain were the formation of the zones of vascularized granulation tissue, with extensive innervation in fissures extending from the outer part of the annulus into the nucleus pulposus. Studies suggested that the degeneration of the painful disc might originate from the injury and subsequent repair of annulus fibrosus. Growth factors such as basic fibroblast growth factor, transforming growth factor β1, and connective tissue growth factor, macrophages and mast cells might play a key role in the repair of the injured annulus fibrosus and subsequent disc degeneration. Although there exist controversies about the role of discography as a diagnostic test, provocation discography still is the only available means by which to identify a painful disc. A recent study has classified discogenic low back pain into two types that were annular disruption-induced low back pain and internal endplate disruption-induced low back pain, which have been fully supported by clinical and theoretical bases. Current treatment options for discogenic back pain range from medicinal anti-inflammation strategy to invasive procedures including spine fusion and recently spinal arthroplasty. However, these treatments are limited to relieving symptoms, with no attempt to restore the disc's structure. Recently, there has been a growing interest in developing strategies that aim to repair or regenerate the degenerated disc biologically.

Keywords: Classification; Degeneration; Diagnosis; Discogenic low back pain; Internal annular disruption; Internal disc disruption; Internal endplate disruption; Intervertebral disc; Treatment.

Figure 1

Endplate disruption grading method schematic diagram.

Figure 2

Discography and computed tomography. A: Discography showing a radial disruption on the lower endplate of L4 vertebra and that the contrast medium flows into the cancellous bone of the lower endplate of L4 vertebra through the fissure; B: Computed tomography scan showing the contrast medium dispersed in the lower endplate of L4 vertebra, with Grade 4 endplate disruption.

Figure 3

Magnetic resonance imaging and discography. A: A 35-year-old woman had a 5-year history of low back pain. Sagittal T2 weighted magnetic resonance imaging showed L4/5 disc degeneration with a high intensity zone in the posterior annulus fibrosus; B: Discography showed L4/5 disc disruption with exact pain reproduction. After discography, 10 mg methylene blue was injected into the painful disc through discographic needle. Low back pain was almost totally relieved. No recurrence was observed at a 12-mo follow-up interval.