Localization of the Lumbar Plexus in the Psoas Muscle: Considerations for Avoiding Lumbar Plexus Injury during the Transpsoas Approach

Hidetoshi Nojiri; Takatoshi Okuda; Kei Miyagawa; Nozomu Kobayashi; Tatsuya Sato; Takeshi Hara; Yukoh Ohara; Hiroyuki Kudo; Tatsuo Sakai; Kazuo Kaneko

doi:10.22603/ssrr.2020-0074

Localization of the Lumbar Plexus in the Psoas Muscle: Considerations for Avoiding Lumbar Plexus Injury during the Transpsoas Approach

Spine Surg Relat Res. 2020 Aug 20;5(2):86-90. doi: 10.22603/ssrr.2020-0074. eCollection 2021.

Authors

Hidetoshi Nojiri^{1

2}, Takatoshi Okuda^{1

2}, Kei Miyagawa^{1

2}, Nozomu Kobayashi^{1

2}, Tatsuya Sato^{1

2}, Takeshi Hara^{3

2}, Yukoh Ohara^{3

2}, Hiroyuki Kudo⁴, Tatsuo Sakai⁴, Kazuo Kaneko^{1

2}

Affiliations

¹ Department of Orthopedic Surgery, Juntendo University, Tokyo, Japan.
² Spine and Spinal Cord Center, Juntendo Hospital, Juntendo University School of Medicine, Tokyo, Japan.
³ Department of Neurosurgery, Juntendo University, Tokyo, Japan.
⁴ Department of Anatomy and Life Structure, Juntendo University, Tokyo, Japan.

Abstract

Introduction: Transpsoas lumbar spine surgery is minimally invasive and has very good corrective effects. However, approach-side nerve complications delay post-operative rehabilitation. We anatomically investigated the localization of the lumbar plexus running in the psoas muscle.

Methods: We examined 27 formalin-fixed cadavers. The left-sided psoas muscle was extracted and cut parallel to the intervertebral disc at the L2/3, L3/4, and L4/5 disc levels. Using digitized photographs, we calculated the ratio of the distance from the front edge of the psoas muscle to the center of the lumbar plexus in the anteroposterior diameter of the psoas muscle (%). Then, we calculated the ratio of the distance from the lateral edge of the psoas muscle to the center of the lumbar plexus in the lateral diameter of the psoas muscle (%).

Results: The anterior-posterior lumbar plexus localization was 74.5 at L2/3, 74.7 at L3/4, and 81.2 at L4/5. There was a significant difference between L2/3 and L4/5 and between L3/4 and L4/5, but not between L2/3 and L3/4 (P=0.02, 0.01, and 0.94, respectively). The lateral and medial lumbar plexus localization was 85.4 at L2/3, 83.9 at L3/4, and 77.7 at L4/5. There was a significant difference between L2/3 and L4/5 and between L3/4 and L4/5, but not between L2/3 and L3/4 (P=0.01, 0.04, and 0.41, respectively).

Conclusions: The lumbar plexus was localized in the posterior one-third and medial one-third of the psoas muscle and moved to a posterolateral location at L4/5. To avoid neuropathy, consider the psoas muscle's position relative to that of the intervertebral disc. It is essential to understand lumbar plexus localization in the psoas muscle when looking directly at this muscle to enter the pricking point or route with a lower risk of nerve damage.

Keywords: anatomy; cadaver; localization; lumbar plexus; lumbar spine surgery; nerve complication; psoas muscle; transpsoas approach.