Recently there has been considerable interest in the role of inflammatory mediator production by herniated degenerate discs. Modic has described MR endplate changes which have an inflammatory appearance and have been linked with discogenic back pain. To date there has been no biomechanical investigation of discs with associated Modic changes.

The aim of this study is to determine if degenerate discs with associated Modic changes have higher levels of pro-inflammatory mediator production than those without Modic changes.

Intervertebral disc tissue was obtained from 52 patients undergoing spinal surgery for sciatica [40] and discogram proven discogenic low back pain [12]. The tissue was cultured and the medium analysed for interleukin-6, interleukin-8 and prostaglandin E2 using an enzyme linked immunoabsorbetn assay method. Preoperative MR images of the patients were examined by a double blinded radiologist to determine the Modic status of the cultured disc level.

Forty percent of patients undergoing surgery for discogenic low back pain had a Modic 1 change compared to only 12.5% of patients undergoing surgery for sciatica [p< .05] There was a statistically significant difference between levels of IL-6, IL-8 and PGE2 production by both the Modic1 [M1] and Modic2 [M2] groups compared to the Modic negative [NEG] group. IL-6:NEGvM1 p< .001, NEG v M2 p< .05, IL-8: NEG v M1 p< .01, NEG v M2 p> .05, PGE2: NEG v M1 p< 01, NEG v M2 p< .05.

Modic changes have been associated with positive provocative discography by a number of authors. Pain generation requires the presence of nerves and hyperalgsia inducing mediators. Both IL-8 and PGE2 are known to induce hyperalgesia. The fact that Modic changes are associated with high levels of production of these mediators supports their role as an objective marker of discogenic low back pain.