Table 1.
Predefined MRI variables at index level(s) with type 1 or 2 MCs and prior disc herniation
| Description | Analysed subgroups | |
|---|---|---|
| STIR signal extent and intensity | ||
| STIR volume | Largest volume of high STIR signal in % of vertebral body marrow volume, visually estimated (not measured), and scored as 0, 1 (< 10%), 2 (< 25%), 3 (25–50%), or 4 (> 50%) | Scores 0–1, 2, and 3–4 |
| STIR height | Maximum height of region with high STIR signal, measured and recalculated into a percentage of vertebral body marrow height | Analysed as a continuous variable and dichotomised into ≤ 50% and > 50% |
| STIR intensity | Maximum intensity of the high STIR signal, measured as a percentage on a scale from normal vertebral body marrow intensity (0%) to cerebrospinal fluid intensity (100%) | < 25%, 25–40%, and > 40%a |
| STIR sup/inf | Presence of high STIR signal both superior (sup) and inferior (inf) to index disc (yes/no) | Yes and no |
| STIR composite | Categorised as STIR3 (volume ≥ 25% AND height > 50% AND intensity ≥ 25% AND yes for sup/inf), STIR2 (not STIR3 or STIR1) and STIR1 (volume < 25% AND intensity < 25%) | STIR1, STIR2, and STIR3 |
| MC type and extent on T1/T2 | ||
| MC type 1 degree | Categorised as type 1 major (primary type 1 both superior and inferior to disc), type 1 minor (primary or secondary type 1, but not type 1 major), and type 2 only (not type 1) | Type 2 only, type 1 minor, and type 1 major |
| MC volume | Largest volume of MC (including all MC types) in % of vertebral body marrow volume, visually estimated, and scored as 0, 1 (< 10%), 2 (< 25%), 3 (25–50%), or 4 (> 50%) | Scores 1, 2, and 3–4 (not score 0; conclusive MC volume cannot be 0 at an index level) |
| MC height | Maximum MC height (including all MC types), measured and recalculated as a percentage of vertebral body marrow height | Analysed as a continuous variable and dichotomised into ≤ 50% and > 50% |
| MC composite | Categorised as 1++ (type 1 major AND volume ≥ 10%—OR—primary type 1 AND volume ≥ 25% AND height ≥ 50% AND yes for sup/inf), 1+ (primary or secondary type 1 but not type 1++) and type 2 only | Type 2 only, 1+, and 1++ |
MRI, magnetic resonance imaging; MCs, Modic changes; STIR, short tau inversion recovery; T1/T2, T1- and T2-weighted fast spin echo images
aSTIR intensity < 25% included MCs with no conclusive STIR signal increase (or decreased STIR signal) and thus no conclusive measured STIR intensity values. These values had likely been < 25% if measured, since the STIR intensity was < 20% for > 90% of intensity measurements reported by only one radiologist (as the other radiologists found no visual signal increase and therefore did not measure STIR intensity). To enhance clinical credibility, images were reviewed to ensure that intensity ≥ 25% implied visually convincing hyper-intensity