Morphometric MRI analysis of lumbar spine intervertebral foramen

The article presents morphometric MRI-analysis of the lumbar intervertebral foramen for anatomical study of the size of Kambin safety triangle and the vulnerability of the exiting spinal nerve during transforaminal interventions. 200 discs were studied in 50 patients after transforaminal endoscopic intervention. Standard DICOM image viewing program for MRI in T1 WI and T2 WI modes was used for the measurement. The most distant location of the exiting spinal nerve from the intervertebral disc was observed at the level of L5S1 vertebrae (9.82 mm, 0.95CI (9,53 10,10), p<0.05). The narrowest safety triangle turned out to be at the level of L2‑L5 vertebrae, where the distance did not differ statistically (1.97–2.28 mm, p> 0.05). A similar pattern was revealed for the distance between the exiting root and the intervertebral joint. The greatest angle between the exiting spinal nerve and the disc plane was found at the level of L5S1 (134.68 °, 0.95CI (132.39 136.97), p<0.001). The angle was close to a straight one at the other levels. The exiting root located dorsal to the disc plane at the cranial levels (L2L3, L3L4) in all cases, in contrast to L5S1 level, where it always located ventrally. Thus, the greatest narrowness of the Kambin safety triangle was revealed in the intervertebral foramen of the cranial lumbar segments (L2L3, L3L4). Transforaminal interventions require special attention to the exiting spinal nerve at these levels, and possibly additional bone resection to widen the foramen.