From the case:
Tuffier's line
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The horizontal line drawn across the highest points of both the iliac crests in an anteroposterior (AP) lumbar radiography is called Tuffier's line.
The line intersect L4/L5 intervertebral disc.
Case Discussion
Intercristal line, Tuffier's line or Jacoby's line most often intersects the L4 vertebral body or its inferior endplate in men, whereas it intersect the L5 vertebral body or its superior endplate in women. In the general population, the intersection of the intercristal line may vary anywhere between the inferior endplate of L4 to the superior endplate of L5.