Anatomical variations of lumbosacral plexus.

BASIS: Deviations detected during spinal operations have motivated us to start research related to variations of lumbosacral plexus formation. Aim of this work was to find out deviations of its formation from ascension of particular roots from foramen invertebrale and foramina sacralia up to formation of terminal branches. SET: One hundred lumbosacral plexi have been examined in 50 adult cadavers for a purpose to find out an incidence of neural variations. We have observed participation of Th(12) root, L(4) and L(5) roots in its formation, as well as various deviations from ascension of particular plexiform roots up to their ending branches. For lumbal plexus, we have observed four nerve roots and six lumbal nerves; for sacral one, three sacral roots with a share of S(4) and lumbosacral trunk formed of L(4) and L(5) roots and four sacral nerves. We have considered also their course, anastomoses and thickness. We highlight motoric innervation particularities in relation to diagnostics besides anatomical complexity and variability.

RESULTS: Variations on the level of neural roots were common, nerve formations were uncommon. Thickness of neural roots, formation or their absence were dependent on the type of plexus, particularly in sacral area. For lumbal plexus, L(1) root was the thinnest and L(4) root was the thickest. L(3) root was the thickest in six cases. Fifth lumbal root usually completely filled foramen invertebrale. We have observed double ascension of L(4) root from foramen invertebrale in 25 cases and plexiform in five cases. In other cases it was branched in various distance following ascension from foramen invertebrale. Plexiform ascension of L(3) root along with L(4) root was present in two cases. Double ascension of L(3) root was present in four cases. L(2), L(3) along with L(5) roots were doubled in two cases. Iliohypogastric nerve was the longest, ilioinguinal was the thinnest and nervus femoralis was the thickest. Changes in sacral plexus on the level of neural roots have been observed 41-times. Double ascension of L(5) root was present in eight cases and plexiform in four cases. Double S(1) root at ascension from foramina sacralia was present 16 times, S(2) 8 times, S(3) once and S(1) along with S(2) 4 times. S(1), S(2) and S(3) roots were branched in various distance following ascension from foramina sacralia in 15 cases. Truncus lumbosacralis was thickened in 19 cases, a share from L(4) root was thicker as L(5) root in 11 cases. Low level of connection between truncus lumbosacralis and S(1) root was observed in 10 cases. Nervus ischiadicus has branched into tibial and peroneal portions already in minor pelvis in two cases. The level of distance of n. (nervus) gluteus superior, n. gluteus inferior, n. cutaneus femoris posterior and n. pudendus was dependent on the plexus type.

CONCLUSION: This study enabled us to find out and to describe extraordinary anatomical deviations in formation of neural roots and nerves of lumbal and sacral plexus, undescribed yet.