Nerve root to lumbar disc relationships at the intervertebral foramen from a surgical viewpoint: An anatomical study

Abstract

The objective of this study was to analyze relationship of the intervertebral disc to the nerve root in the intervertebral foramen. Fourteen formalin-fixed cadavers were studied and measurements were performed. At the medial line of the neural foramen, the disc-root distance gradually increased from L1-L2 to L5-S1. The shortest distance between the disc to nerve root was L1-L2 (mean, 8.2 mm) and the greatest distance was found at L3-L4 (mean, 10.5 mm). In the mid-foramen, the disc-root distance decreased from L1-2 to L5-S1. The shortest distance from the disc to nerve root was found at L5-S1 (mean, 0.4 mm); and the greatest distance, at L1-L2 (mean, 3.8 mm). For the lateral line, the distance between an intersection point between the medial edge of the nerve root and the superior edge of the disc and lateral line of the foramen consistently increased from L1-L2 to L5-S1. The shortest distance from nerve root to the lateral border of the foramen, at the point where the nerve root crosses disc was at level L1-L2 (mean, 2.6 mm), the greatest distance, L5-S1 (mean, 8.8 mm). The width of the foramina progressively increased in a craniocaudal direction (mean, 8.3-17.8 mm from L1-2 to L5-S1, respectively). The mean height of the foramina was more or less the same for disc levels (range, 19.3-21.5). The results showed that nerve roots at lower levels traveled closer to the midline of the foramen. This morphometric information may be helpful in minimizing the incidence of injury to the lumbar nerve root during foraminal and extraforaminal approaches.

Anatomic Considerations of Intervertebral Disc Perspective in Lumbar Posterolateral Approach via Kambin's Triangle: Cadaveric Study

“…Osman and Marsolais [14] stated that the angular range for safely performed diskoscopies between T12 to L3 (38-60 degrees) is different from those of L3–S1 level (40–65 degrees). Arslan et al [15] reported that the L1, L2, and L3 nerve root crossed the disc level closest to lateral border of foramen. Therefore these roots compared with lower level may be at a lower risk of injury during transforaminal percutaneous endoscopic discectomy.…”

The anatomic rationale for transforaminal endoscopic interbody fusion: a cadaveric analysis

“…1,9,10,15 Mirkovic et al described the dimensions of the safe margins for a working cannula in the neural foramen in 1995 and determined that a cannula placed in line with the medial one-third of the pedicle could sustain a safe average diameter of 7.5 mm. 10 Min et al in 2005 determined the mean distance between the exiting nerve root and the superior articulating process to be 11.6 mm, which is sufficiently smaller than our own determination of 15.5 mm for the average distance between the exiting and traversing nerve roots at the top of the base of the working triangle with the superior articulating process removed.…”

Anatomical relationship between Kambin’s triangle and exiting nerve root

“…Arslan et al [13] also showed anatomical variation in the distance between the ENR and pedicle and the height and width of intervertebral foramen from L1-L2 to L5-S1 in 14 male formalin-fixed cadavers.…”