VCOM Research Day Program Book 2023

Medical Student Research Biomedical

21 Passive Hip Flexion in the Lateral Decubitus Positive Affects Genitofemoral Nerve Angulation with Respect to the Lumbar Spine: a Proof of Concept with Implications for Patient Positioning in Lateral Approaches to the Spine

Benjamin Mann; Michael McGehee; Jordan Oliver; Jonathan Millard Corresponding author: b.mann@vt.vcom.edu

Edward Via College of Osteopathic Medicine-Virginia Campus

Lateral approaches to anterior column reconstruction have grown in popularity in recent decades. Recent evidence has indicated that lateral methods outperform anterior and posterior approaches in terms of intraoperative blood loss, foraminal height restoration, and in-patient recovery times; however, iatrogenic neural damage remains an issue. There have been many efforts to describe the location of elements of the lumbar plexus with respect to surgical corridors and targets of sharp dissection. The primary aim of this study was to explore the effect that hip flexion has on genitofemoral nerve positioning. Two modified-Thiel-embalmed whole-body donors (VSAP SE) were dissected to reveal the retroperitoneal space. Ten 3-D landmark points were selected on the ilium, femur, spinal column, and genitofemoral nerve. A Microscribe ® i+ 3D Digitizer portable coordinate measuring machine was used to record the position

of the landmarks while passively simulating three different stages of hip flexion guided by a goniometer (40, 60, and 80 degrees). Coordinates were imported in MorphoJ v1.07a for geometric analysis. Generalized Procrustes superimposition was used to remove nuisance factors and isolate shape. Lollipop diagrams were used to assess hip flexion-dependent ventral displacement of the genitofemoral nerve. Visualization was enhanced with AutoDesk Maya v2023.2. Results demonstrate clear angle-dependent anterior shift of the genitofemoral nerve as the hip was moved through its range of motion. At 80 degrees of hip flexion the mean landmark configuration for the genitofemoral nerve breached the plane of the anterior intervertebral discs of the lumbar spine. These findings suggest that increasing hip flexion angle may result in ventral movement of the psoas

muscle relative to the spine with associated corridor eclipsing by components of the lumbar plexus and an increase in risk to neural structures. This study enhances current understanding by utilizing donors with life-like tissue texture and pliability, as well as representational joint resistance. Careful presurgical planning, MR evaluation for natural rising psoas sign, and thoughtful positioning may improve the current rates of postoperative neuropraxia

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