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Lumbar Plexus Anatomy within the Psoas Muscle: Implications for the Transpsoas Lateral Approach to the L4-L5 Disc
Timothy T. Davis, MD1; Hyun W. Bae, MD1; MAJ James M. Mok, MD, MC, USA2; Alexandre Rasouli, MD1; Rick B. Delamarter, MD1
1 Cedars-Sinai Spine Center, Cedars-Sinai Medical Center, 444 San Vicente Boulevard, Suite 800, Los Angeles, CA 90048. E-mail address for T.T. Davis: ttdavis23@gmail.com
2 Orthopaedic Surgery Service, Madigan Army Medical Center, Building 9040A, Fitzsimmons Drive, Tacoma, WA 98431
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Disclosure: None of the authors received payments or services, either directly or indirectly (i.e., via his or her institution), from a third party in support of any aspect of this work. One or more of the authors, or his or her institution, has had a financial relationship, in the thirty-six months prior to submission of this work, with an entity in the biomedical arena that could be perceived to influence or have the potential to influence what is written in this work. No author has had any other relationships, or has engaged in any other activities, that could be perceived to influence or have the potential to influence what is written in this work. The complete Disclosures of Potential Conflicts of Interest submitted by authors are always provided with the online version of the article.

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Investigation performed at Cedars-Sinai Medical Center, Los Angeles, California

A commentary by Michael J. Bolesta, MD, is linked to the online version of this article at jbjs.org.

Copyright © 2011 by The Journal of Bone and Joint Surgery, Inc.
J Bone Joint Surg Am, 2011 Aug 17;93(16):1482-1487. doi: 10.2106/JBJS.J.00962
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The transpsoas lateral surgical approach has been advocated as an alternative to direct anterior approaches for less invasive or minimally invasive access to the spine. Postoperative thigh pain, paresthesia, and/or weakness have been described after the use of this surgical approach. The purpose of this cadaveric anatomic study is to provide a description of the lumbar plexus as it relates to the transpsoas lateral surgical approach.


Dissection of the lumbar plexus was performed in eighteen cadaveric specimens. Needle markers were placed in the L2-L3, L3-L4, and L4-L5 discs in the midcoronal plane. The anatomic structures were surveyed, and the proximity of the needle to the neural structures was observed.


In thirteen of the eighteen specimens, the femoral nerve received its contributions from the L2 to L4 nerve roots and was formed at the L4-L5 disc space. In all specimens, the femoral nerve passed dorsal to or directly at the midpoint of the disc. In three specimens, the needle displaced or was immediately adjacent to the femoral nerve. The femoral nerve was found between the needle and the posterior aspect of the L4-L5 disc space in thirteen of the eighteen specimens.


Because of the proximity of the neural elements, in particular the femoral nerve, to the center of the disc space, the transpsoas lateral surgical approach to the L4-L5 disc space will likely cause intraoperative displacement of neural structures from their anatomic course during retractor dilation. Careful attention should be paid to retractor placement and dilation time during transpsoas lateral access surgery, particularly at the L4-L5 disc.

Clinical Relevance: 

During the transpsoas lateral surgical approach to the L4-L5 disc space, the femoral nerve should be considered to be at risk intraoperatively because of the position and size of currently available retractors.

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    These activities have been planned and implemented in accordance with the Essential Areas and policies of the Accreditation Council for Continuing Medical Education (ACCME) through the joint sponsorship of the American Academy of Orthopaedic Surgeons and The Journal of Bone and Joint Surgery, Inc. The American Academy of Orthopaedic Surgeons is accredited by the ACCME to provide continuing medical education for physicians.
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