• Spine · Nov 2023

    Female Sex and Supine Proximal Lumbar Lordosis are Associated with the Size of the LLIF "Safe Zone" at L4-5.

    • Mitchell S Fourman, Ram K Alluri, J Manuel Sarmiento, Keith W Lyons, Francis C Lovecchio, Kasra Araghi, Sidhant S Dalal, Daniel J Shinn, Junho Song, Pratyush Shahi, Dimitra Melissaridou, John A Carrino, Evan D Sheha, Sravisht Iyer, James E Dowdell, and Sheeraz S Qureshi.
    • Spine Service, Department of Orthopaedic Surgery, Hospital for Special Surgery, New York, NY.
    • Spine. 2023 Nov 15; 48 (22): 160616101606-1610.

    Study DesignRetrospective chart review.ObjectiveIdentify demographic and sagittal alignment parameters that are independently associated with femoral nerve position at the L4-L5 disk space.Summary Of Background DataIatrogenic femoral nerve or lumbar plexus injury during lateral lumbar interbody fusion (LLIF) can result in neurological complications. The LLIF "safe zone" is the anterior half to two third of the disk space. However, femoral nerve position varies and is inconsistently identifiable on magnetic resonance imaging. The safe zone is also narrowest at L4-L5.MethodsAn analysis of patients with symptomatic lumbar spine pathology and magnetic resonance imaging with a visibly identifiable femoral nerve evaluated at a single large academic spine center from January 1, 2017, to January 8, 2020, was performed. Exclusion criteria were transitional anatomy, severe hip osteoarthritis, coronal deformity with cobb >10 degrees, > grade 1 spondylolisthesis at L4-L5 and anterior migration of the psoas.Standing and supine lumbar lordosis (LL) and its proximal (L1-L4) and distal (L4-S1) components were measured. Femoral nerve position on sagittal imaging was then measured as a percentage of the L4 inferior endplate. A stepwise multivariate linear regression of sagittal alignment and LL parameters was then performed. Data are written as estimate, 95% CI.ResultsMean patient age was 58.2±14.7 years, 25 (34.2%) were female and 26 (35.6%) had a grade 1 spondylolisthesis. Mean femoral nerve position was 26.6±10.3% from the posterior border of L4. Female sex (-6.6, -11.1 to -2.1) and supine proximal lumbar lordosis (0.4, 0.1-0.7) were independently associated with femoral nerve position.ConclusionsPatient sex and proximal LL can serve as early indicators of the size of the femoral nerve safe zone during a transpsoas LLIF approach at L4-L5.Copyright © 2022 Wolters Kluwer Health, Inc. All rights reserved.

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