Segmental Contributions to Lumbar Lordosis: A Computed Tomography Study.

BACKGROUND: The aim of this study was to determine the contribution of individual vertebral body lordosis to lumbar lordosis and establish the relationship of vertebral body lordosis to the pelvic incidence (PI). METHODS: One-hundred and two computed tomography (CT) scans on patients free of radiographic disease were measured for PI and segmental lordosis of both bone and disc from L1 to sacrum. Correlative analysis and analysis of variance (ANOVA) were used to identify contribution from bone and disc to lordosis. RESULTS: The mean total bony lordosis was 10.8° (SD 11.5°), mean total disc lordosis was 36.3° (SD 9.9°), and mean combined lordosis was 47.1° (SD 10.0°). The mean PI of the entire cohort was 49.2° (SD 9.3°). One-way ANOVA demonstrated a significant difference between the PI strata in total bony lordosis values with a mean difference of 14.0° between low and high PI cohorts (P < .001) and also mid- and high PI cohorts of 9.9° (P = .008). Overall, distal lordosis represented 80.8% of the total lordosis. In the proximal lumbar segments, the mean contribution from bone was -4.0° (SD 6.8°) and the mean contribution from disc was 13.6° (SD 6.0°). In the distal, the mean contribution from bone was 14.7° (SD 6.5°) and from disc, 22.7° (SD 6.2°). CONCLUSIONS: The contribution to lordosis from the vertebral bodies is greater in the proximal lumbar spine with increasing PI. With low PI, the proximal vertebral bodies demonstrate reduced contribution to lordosis and in some instances are kyphotic. Future research efforts should place greater emphasis on providing segmental rather than just global analysis of alignment. CLINICAL RELEVANCE: Restoration of lumbar spine lordosis should take into account the variation in segmental lordosis contributions as it relates to PI.