Virginia Research Day 2025

Medical Student Research Biomedical

07 Genitofemoral Nerve Patterning with Applications to Lateral Lumbar Interbody Fusion

Tobias Addis, MPH; Fernanda Robles; Jonathan Millard, Ph.D Corresponding author: taddis@vcom.edu

Edward Via College of Osteopathic Medicine - Virginia Campus

for emergence and centered around L1/L2 for rami contribution. The results from this study suggest that a reliable pattern exists for where the GFN may track from its origin in the lumbar plexus. Furthermore, differences in spinal cord ventral rami contributions to the GFN may be influenced by sex, highlighting the importance of considering individual patients’ anatomies when performing procedures in proximity to the lumbar plexus. The significant trending of the sex-based differences in GFN emergence from the psoas major further reinforces the need to consider patients’ anatomies and may help guide practitioners when performing LLIF/XLIF procedures. Future research with increased sample sizes may help to reinforce these findings and should aim to include samples with anatomical variation - such as when the GFN splits into its genital and femoral branches prior to emergence from the psoas major. Efforts to identify and manually preserve the GFN during LLIF procedures may be guided by these findings and lead to reduction in iatrogenic injury.

The prevalence of spinal degenerative disease in the U.S. is 27.3% by age 65 and increases with age - with nearly 200,000 lumbar fusions performed in 2015. The left lateral interbody fusion, or LLIF (also: extreme lateral lumbar interbody fusion, or XLIF), technique has recently been developed to reduce invasiveness in lumbar fusion and requires a transpsoas approach in order to access the T12/L1 to L4/L5 disc spaces. Because of its unique anatomical course and variability, iatrogenic damage to the genitofemoral nerve (GFN) has been identified as a key concern for practitioners utilizing the LLIF technique for lumbar vertebral fusion. The retraction of the psoas major muscle during this approach can place stress on the GFN. Research has identified the prevalence of immediate postoperative anterior thigh/groin pain at over 38% in LLIF. The objective of this study is to identify anatomical trends in the course of the GFN in order to guide visualization of the nerve in hopes of sparing its function during LLIF. 122 adult cadavers were dissected to localize the spinal level at which the GFN emerged from the

psoas. The psoas was then dissected out to identify the spinal ventral rami contributions to the GFN. After localizing the muscular emergence of the GFN and its spinal contributions, a Chi-squared analysis was performed to identify whether the factors of sex or laterality influence the spinal levels at which the GFN emerges from the psoas muscle and if those factors influence the spinal levels contributing to the GFN. The analysis indicated that, while there was not a statistically significant difference between sexes for GFN emergence from the psoas, there was a strong trend towards significance, [ X 2 (5, N = 122) = 9.496, p = .091]. Laterality had no significance on GFN emergence, [ X 2 (5, N = 122) = 3.196, p = .670] or spinal rami contribution [ X 2 (2, N = 122) = .202, p = .904]. However, the analysis identified a statistically significant difference between sexes for the rami contributing to the GFN [ X 2 (2, N = 122) = 6.934, p = .031]. Furthermore, histogram analysis of the prevalence of the GFN’s psoas emergence and spinal level contribution revealed a normal distribution centered around the L3/L4 disc

72