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Abstract
The intervertebral foramen is formed by two adjacent vertebrae and an intervertebral disc. Previous studies examining the foramen have been performed using various methods. The author obtained characteristics of the intervertebral foramen based on silicon mold. The author used 18 cadavers and dissected the lumbar intervertebral foramen. First, positional levels of the spinal nerve in the intervertebral foramen were measured. Second, after being removed all tissues covering the intervertebral, bony foramen was filled with melted silicon to mold the cross section. Subsequently, the solidified silicon mold was removed and stamped on a paper. The paper was scanned and analyzed area, perimeter, height and width of the intervertebral foramen on a computer. Area (average, 9.43 mm2) and perimeter (average, 48.02 mm) did not show any statistical significant pattern for any lumbar vertebral levels. However, the height and width significantly differed at the fifth lumbar vertebra, which had the shortest height (the fifth, 13.00 mm; average, 15.78 mm) and longest width (the fifth, 8.61 mm; average, 7.87 mm), although there were similar patterns in case of area and perimeter of the first to fourth lumbar vertebra. Height had a decrease tendency while width had an increase tendency both from the second to fifth lumbar vertebra. Spinal nerves went through near the intervertebral disc level from the first to fourth lumbar vertebra, although they passed below the disc at the fifth level. This study provides a different view of methodology for the 3-dimensional aspect for the intervertebral foramen. Results of this study may indicate that height and width of the intervertebral foramen changed along all lumbar vertebral levels; nevertheless, area and perimeter of the intervertebral foramen remained constant.
References
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Fig. 1.
Stamp of silicon molds for measurements. The IVF stamps (red, upper) of the cross sections were edited and recreated as gray scale TIFF formats (black, lower). Area, perimeter, height and width of the IVF were measured in the image via the NIH image tool.
Fig. 2.
Height (A) and width (B) patterns of the IVFs. The heights in L1-L5, L2-L5, L3-L5 have different values and show statistical sig-nificance among them. The width shows similar statistical significance in L1-L5 and L2-L5. Standard errors are shown as whiskers at each level.
Fig. 3.
Nerve location levels in the IVFs. From L1 to L5, lower lumbar level tends to have lower position of nerve pathways. The L5 has many nerve pathways running below the intervertebral disc level (U = upper, M = middle, and L = Lower 1/3 of the interverte-bral disc).
Table 1.
Area and perimeter of the intervertebral foramina (unit: mm2 for area and mm for perimeter).
Table 2.
Height and width of the intervertebral foramina (unit: mm).
Table 3.
Results of linear mixed models for height and width and of testing for equality of effects in each model.
| Variable | Test of Effects | ||||
|---|---|---|---|---|---|
| Effect | Num DF | Den DF | F value | Probability> F | |
| Height | Side | 1 | 67 | 4.71 | 0.0335∗ |
| Level | 4 | 79 | 6.08 | 0.0003∗ | |
| Width | Side | 1 | 67 | 0.00 | 0.9733 |
| Level | 4 | 79 | 3.71 | 0.0081∗ | |
Table 4.
Results of least square means (denoted by estimate) and multiple comparisons.
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