Calculation of Disc Height Index from Mouse Lumbar Spinal X-ray. Lateral x-ray images of the intact lumbar spine were taken at 4× using a Faxitron ® MX-20 (Faxitron X-Ray LLC, Lincolnshire, IL). Disc Height Index (DHI) was determined according to the following equation: Disc Height Index (DHI) = 2 × (DH1 + DH2 + DH3)/(A1 + A2 + A3 + B1 + B2 + B3) where A and B represent the length of the vertebral bone immediately rostral and caudal to the IVD, respectively; and DH represents the disc height between adjacent vertebrae.
Tajerian et al. Molecular Pain 2011 7:65 doi:10.1186/1744-8069-7-65