How Prone Position Affects the Anatomy of Lumbar Nerve Roots and Psoas Morphology for Prone Transpsoas Lumbar Interbody Fusion

BACKGROUND: Lumbar nerve root injury is a serious complication of transpsoas lumbar interbody fusion. Researchers have reported lumbar nerve roots and psoas muscle anatomy in the supine position, but no previous studies have used prone position magnetic resonance imaging to evaluate these structures. OBJECTIVE: The purpose of this study was to show the changes in the lumbar nerve roots and psoas muscle related to the lumbar intervertebral disc using supine and prone magnetic resonance imaging. METHODS: Thirty volunteers without spinal or hip abnormalities were included in this observational study. Each volunteer underwent supine and prone lumbosacral magnetic resonance imaging without abdominal compression. The lumbar nerve roots, psoas muscle, aorta, superior vena cava, common iliac artery, and vein were identified at each lumbar disc level. The lumbar plexus position relative to the transpsoas working channel, psoas muscle morphology, and great vessels relative to the anterior and posterior aspects of the annulus fibrosus in the axial plane were measured by 1 observer, and intraobserver reliability was calculated. RESULTS: Fifteen men and 15 women were included in this study. There were no significant differences in the axial image distance of the lumbar nerve roots, psoas/disc ratio, and location of other related anatomy between the supine and prone positions. More lordosis (both upper and lower arc lordosis) was noted in the prone position (51.98 degrees +/- 0.54 degrees) than in the supine position (42.12 degrees +/- 10.13 degrees). CONCLUSIONS: Lumbar nerve roots, psoas morphology, and great vessel position were not affected by the prone position compared with the supine position.

Automated summary

This study used magnetic resonance imaging to observe the changes in lumbar nerve roots and psoas muscle during lumbar intervertebral disc surgery. The results showed that the prone position did not affect the lumbar nerve roots, psoas morphology, and great vessel position compared to the supine position.