Are high-intensity zones and Modic changes mutually exclusive in symptomatic lumbar degenerative discs?

Modic changes (MCs) and high-intensity zones (HIZs) potentially serve as variably sensitive markers for discogenic chronic low-back pain (CLBP). No study has hitherto assessed the phenomenon of MC-HIZ coexistence at a single level, and the goal in this study was to assess the nature and frequency of this phenomenon.

One hundred twenty consecutive patients with discogenic CLBP in whom lumbar MR imaging studies had demonstrated an HIZ, an MC, or both were included.

This cohort (120 consecutive patients with 193 degenerative discs) had discogenic CLBP in at least 1 lumbar level associated with either an HIZ (77 discs), an MC (67 discs), or both (16 patients); there were 55 coexistent non-HIZ/non-MC degenerative discs. Painful MC-HIZ coexistence at 1 level occurred in 6 patients (5 of whom were female). If HIZs and MCs were random, independent entities, then MC-HIZ coexistence at 1 level would have been expected in 67 x 77/193 (that is, 27) discs. The observed frequency was therefore significantly lower (chi(2) = 41, p < 0.001). There were no significant demographic differences between groups. The HIZ disc height (8 +/- 0.2 mm) was significantly greater than the MC (6.6 +/- 0.2 mm) or MC-HIZ (6.7 +/- 0.2 mm) disc heights (p < 0.001).

In patients with discogenic CLBP associated with HIZ or MC lesions, MC-HIZ coexistence at 1 level was significantly rarer than expected even by chance; thus, despite both being manifestations of a seemingly common degenerative process, HIZ and MC more closely represent "either/or" phenomena. Because HIZ disc height was significantly greater, HIZs may develop earlier in the disc degenerative ontogeny. If any degenerative disc may only display an HIZ first, yet may ultimately display an MC instead, then HIZs must invariably regress as MCs supervene (or even vice versa). The MC-HIZ coexistence would therefore represent either a rare stable state (possibly more common in females) or a transitory state, as one lesion gradually replaces the other. Longitudinal studies would confirm or refute these hypotheses, although significantly larger sample sizes would be required.