RESUMEN
Objective:To eveluate and study the anatomic basis of the posterior contour sign of lumbar intervertebral disc.Methods:The most protruding length of the soft tissue mass behind intervertebral spase on lumbar plain film were measured in 100 cases and compared with CT or MR findings.Results:41 posterior contour sign of the interlumbar disc were fined in 39 cases,of which there were 25 in L4/5(61.0%),15 in L3/4(15.6%)and 1 in L2/3(2.4%).The protruding was less than 0.2 cm in 26 and larger than 0.2 cm in 15,there were 10 lumbar disc protruding confirmed by CT or MR ,7 of which the pesterior contour ≥0.2 cm,and 3＞0.3 cm,none was ≤0.2 cm.Conclusion:The adipose tissue in the posterior border of lumbar body and disc was the anatomic basis of the sign,and it was an importent sign for diagnosing of lumbar disc hernia on plain film.