Location of the Femoral Nerve in the Lateral Decubitus Versus Prone Position

Abstract

Study Design Cadaveric study. Objective To compare the position of the femoral nerve within the lumbar plexus at the L4-L5 disc space in the lateral decubitus vs prone position. Methods Seven lumbar plexus specimens were dissected and the femoral nerve within the psoas muscle was identified and marked with radiopaque paint. Lateral fluoroscopic images of the cadaveric specimens in the lateral decubitus vs prone position were obtained. The location of the radiopaque femoral nerve at the L4-L5 disc space was normalized as a percentage of the L5 vertebral body (0% indicates posterior location and 100% indicates anterior location at the L4-L5 disc space). The location of the femoral nerve at L4-L5 in the lateral decubitus vs prone position was compared using a paired t test. Results In the lateral decubitus position, the femoral nerve was located 28% anteriorly from the posterior edge of the L4-L5 disc space, and in the prone position, the femoral nerve was relatively more posterior, located 18% from the posterior edge of the L4-L5 disc space ( P = .037). Conclusions The femoral nerve was on average more posteriorly located at the L4-L5 disc space in the prone position compared to lateral decubitus. This more posterior location allows for a larger safe zone at the L4-L5 disc space, which may decrease the incidence of neurologic complications associated with Lateral lumbar interbody fusion in the prone vs lateral decubitus position; however, further studies are needed to evaluate this possible clinical correlation.

A retrospective review of single-position prone lateral lumbar interbody fusion cases: early learning curve and perioperative outcomes

“…Prone positioning has been documented to play an important role in improving passive segmental lordosis [12] and has been seen to drift the psoas and plexus posteriorly [9]. These are desirable when performing a lumbar interbody fusion using the LLIF technique.…”

“…Although possible, these workarounds have not come into general favour with the larger spine community. There is still a preference to perform pedicle screw placement in the prone position, both for ease and improved lordosis in the prone position [8,9]. In an effort to restore operating room efficiency while maintaining the benefits of a LIF, the prone lateral technique for interbody fusion is studied [10,11].…”

Extreme lateral interbody fusion (XLIF) approach for L5-S1: Preliminary experience

“…The femoral nerve, the obturator nerve and the genitofemoral nerve are the three branches of the lumbar plexus that were carefully avoided during the surgery. According to Uribe et al (24,25), the femoral nerve, formed from branches of the L2, L3, and L4 roots, was found deep in the psoas muscle, descending in a gradual posterior-to-anterior trajectory at the L4-5 disc space and continuing downward between the psoas and the iliacus muscle. In a study by Jianfei Ji et al (26), the femoral nerve of all 6 specimens was located at the posterior middle quarter and the posterior quarter part at the L5-S1 level.…”

The Prone Lateral Approach for Lumbar Fusion—A Review of the Literature and Case Series

“…Furthermore, it has been hypothesized that, while in the prone position, extension of the hips results in a posterior retraction of the psoas muscle. This may move the nerves of the lumbar plexus posteriorly and thus provide a larger safe corridor to access the disc space [ 21 , 22 ], although recent imaging findings have not supported this theory [ 23 ]. While it is a relatively new approach, early reports regarding the prone lateral approach have been promising.…”