We analyzed the relationship between the level of Jacoby's line (Intercrestal line, Tuffier's line), which is an imaginary line between the uppermost iliac crest, and the grade of disc degeneration as evaluated by magnetic resonance imaging. The subjects of this study were 147 patients with low back pain and/or sciatica, with ages ranging from 20 to 59 years, with elderly patents excluded. The distance between the upper posterior margin of the sacral vertebra and the level of the uppermost iliac crest was divided by the height of L4 vertebra measured on lateral roentgenogram. We named this numerical value the Jacoby height index (JHI) and suggested it as a parameter which shows the level of Jacoby's line. JHI, lumbar lordotic angle (LLA) and lumbosacral angle (LSA) were compared with the grade of disc degeneration. The grade of disc degeneration increased significantly less with JHI at the L4-5 (p<0.05) and L5-S (p<0.01). However at the L3-4 level, there was no relationship between JHI and the grade of disc degeneration. LLA and LSA did not correlate with the grade of disc degeneration. We concluded that the lower the level of the uppermost iliac crest, the higher the grade of disc degeneration at L4-5 and L5-S.
