Background: Severe and chronic back pain often originates from degenerated intervertebral discs, probably from lesions in the outer posterior anulus. Unlike the nucleus, the outer anulus has a high cell density and adequate metabolite transport. The outer annulus can heal after injury in small and young experimental animals, but little is known about the healing potential of adult human discs.

Purpose: We seek evidence that healing of the human outer anulus follows the three stages of tendon healing: inflammation, repair, remodelling. If so, then manual therapy and self-treatment techniques known to facilitate tendon healing could be adapted to treat discogenic back pain.

Methods: Anulus tissue was removed at surgery (usually posteriorly) from 14 patients with discogenic back pain. Tissue was paraffin embedded and sectioned at 5 μm for histology and immunohistochemistry. Apoptosis was detected using an antibody for caspase-3.

Results: Fissures in the peripheral posterior annulus, and herniated tissue fragments, were associated with blood vessels, inflammatory cells, and with focal loss of proteoglycans. Cell density decreased with distance from fissures from the disc periphery. Overall cell density decreased with age. Apoptosis was greater in the nucleus than in the annulus, and was particularly associated with cell clusters, and with anulus fissures.

Conclusion: These preliminary results suggest an inflammatory healing response in the outer anulus, strongly associated with radial fissures. Loss of proteoglycan from fissure margins may facilitate the ingrowth of capillaries and nerves, which then stimulate local healing in the vicinity of the fissures.

Conflicts of Interest: None

Source of Funding: BackCare