| Study Design. Study of morphological characteristics in cadaveric lowlumbosacral vertebrae spines was performed. Model of disc heightsloss was created and foramina change in the process of the loss ofdisc heights on this model were studied.Objective. To study the morphological characteristics of foramina oflow lumbar and the anatomic relationships between foramina and discsand nerve roots, and their changes in the process of the loss of discheights.Summary of background data. Foramina are lateral "windows" ofspinal canal. The lumbar nerve roots pass through the foramina afteroriginating from the thecal sac. Normally, there is enough space withinforamina to allow nerve roots to pass through. In degenerative lumbar, subluxation of facet joint, lateral bulging of anulus fibrosis and hypertrophic ligamentum flavum increase the risk of foraminal stenosis and nerve roots trapment. Especially, the loss of disc height is always associated with foraminal stenosis. In low lumbar spines, the ratio of the cross-sectional area of nerve roots to cross-sectional area of foramen is higher than upper lumbar. It becomes the cause of higher accidence of nerve roots compression in low lumbar spines. Few studies have focused on the relationship between the loss of disc heights and morphological characteristics and dimensions of foramina. Methods. Eight fresh cadaver lumbar spines (L3~Sacrum) were obtained for study. Surrounding musculature was cleaned, and the ligaments and nerve were reserved. The specimens were stored at -20 "C until tested. After they were completely thawed at room temperature, the morphological characteristics of foramina and nerve roots and their anatomic relationship were observed. The dimensions of foramina were measured with a calliper. Each specimen was taken lateral and 15?oblique radiograph to measure the discs and foraminal heights. Then specimens were placed on the special biomechanical instrument and loaded 500 Newton. The morphological characteristics and dimensions of foramina and the discs heights were studied again. Anulus fibrosises were cut open in the anterior section and nucleus pulposus were removed. Loaded 300 and 500 Newton, the morphologicalcharacteristics and dimensions of foramina and the disc heights were studied again. All the data were recorded Statistical analysis was done with SPSS 10.0 FOR WINDOWS software.Results. In the natural condition without any loaded, the foramina (Us and LsSi) were inverted teardrop-shaped, and nerve roots were located in upper section of foramina surrounded by fat. The foraminal heights wasl 6.14 02.24mm in U/s, and 15.22 .16mm in L5Si; max width was 11.19.06mm in U/s, and 10.4?.08mm in L5Si; min width was 5.4?1.35mm inU/s, and 6.86+1.26mm inL5Sr, anterior disc height was 9. ?1.90mm in L45, and 10.8 ?.01 mm in L5Si; posterior disc height was .84?1.36mm in U/s, and6.09?1.32mm in L5Si. Loaded 500 Newton, the foramina were still inverted teardrop-shaped. The foraminal height lost 10.75% in U/s, and 16.11% in LsS max width Iost11.60% in Us, and 11.39% in LsSi; min width was of no statistical difference in U/s and in L5Si; anterior disc height was of no statistical difference in U/s and in L5Si; posterior disc height lost 11.99% in U/s, and lost 11.82% in L5Si. Nerve roots were still located in upper section of foramina without obviously-crushed fat. After nucleus pulposus were removed and loaded, lateral bulging annulus fibrosis, subluxating facet joint and shrunken ligamentum flavum made foramina change into pear-shaped. Nerve roots got close to anterior annulus fibrosis and posterior ligamentum flavum, and were compressed against the superior pedicle by them. Surrounding fat was crushed obviously.Loaded 300 Newton, the foraminal height lost 26.09% in U/s, and 26.63% in L5Si; max width lost 17.85% in U/s, and 13.98% in L5Si; min width was of no statistical difference in L4/5 and in L5S1; anterior disc height lost 16.63% in U/s, and 26.49% in L5S1, posterior disc height lost 41.08% in U/s, and...
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