Measurement of Intervertebral Disc Space Height

Abstract

Six methods of measuring intervertebral disc space height (IVD) were evaluated in experiments using isolated vertebral pairs, intact human cadavers, and living subjects. Accurate measurements of IVD required methods that corrected for radiographic magnification and carefully controlled the source–target-film relationships. Axial rotation beyond 40° and lateral bend beyond 20° prevented accurate measurements. A wide variation In IVD was found in 132 patients who had previously undergone surgical procedures for nerve root compression from herniated discs at the L4–5 and L5–S1 levels 10 or more years before. Disc space narrowing was significantly greater at operated than nonoperated levels (P=0.01), but did not correlate with clinical results. The clinical and research applications of these methods are critically assessed.