Lumbar spine bone mineral density

Method

Areal bone mineral density of the lumbar spine, typically L1-L4 or L2-L4, by dual-energy X-ray absorptiometry. The vertebral levels included, the scanner manufacturer, and whether the result is absolute density or percent change from baseline are recorded on the edge; cross-manufacturer values require standardisation.

The method is part of the endpoint identity. Studies measuring the same quantity by a different method are held as separate endpoints.

Notes

Site-specific, not a whole-skeleton measure. Its near-miss is femoral neck bone mineral density from the SAME scan session in the same unit: the lumbar spine is predominantly trabecular and the femoral neck predominantly cortical, they respond on different timescales, and they dissociated inside a single trial in this round (spine significant, neck not). Merging them into one bone-density node averages away a real site-specific effect. Distinct also from non-vertebral fracture incidence, an event endpoint in risk-ratio units for which this is only a surrogate. Degenerative facet disease and aortic calcification inflate spine values in older cohorts.