A MRI study of lumbar plexus with respect to the lateral transpsoas approach to the lumbar spine

To evaluate the relative position between lumbar plexus and access corridor of minimally invasive lateral transpsoas lumbar approach, as well as the approach safety.

Three-dimensional fast imaging employing steady-state acquisition (3D FIESTA) sequence images of lumbar spine were obtained from 58 patients with lumbar degenerative diseases for reconstruction to analyze the distribution of lumbar plexus from L1–L2 to L4–L5 level with respect to the transpsoas lumbar approach. The axial image distance (AID) between the anterior edge of lumbar plexus and the sagittal central perpendicular line (SCPL) of disc was measured. SCPL was drawn perpendicularly to the sagittal plane of intervertebral disc and it passed through its central point, which is initial dilator trajectory for transpsoas approach. As related to the SCPL of disc, the distance with a positive value was set to indicate neural tissue posterior to it, while anterior to it was represented by a negative value.

In relation to SCPL of disc, the AID of lumbar plexus was measured 13.01 ± 1.70, 8.61 ± 2.26, 1.12 ± 2.37 and −5.42 ± 3.26 mm from L1–L2 to L4–L5 level, respectively, while the AID of genitofemoral nerve was recorded −1.13 ± 2.87, −5.78 ± 2.33 and −10.53 ± 3.30 mm from L2–L3 to L4–L5 level accordingly.

With respect to the SCPL of disc, a trajectory of guide wire or a radiographic reference landmark to place working channel, lumbar plexus lies posteriorly to it from L1–L2 to L3–L4 level and shifts anteriorly to it at L4–L5 level, while genitofemoral nerve locates anteriorly to the SCPL from L2–L3 to L4–L5 level. Neural retraction may take place during sequential dilation of access corridor especially at L4–L5 level.