title: An anatomic study of the lumbar plexus with respect to retroperitoneal endoscopic surgery.
abstract: METHODS
  The distribution of the lumbar plexus was analyzed using cadavers.
  
  
  OBJECTIVE
  To clarify the safety zone to prevent nerve injuries with respect to retroperitoneal endoscopic surgery.
  
  
  BACKGROUND
  Surgical approaches to the retroperitoneal space vary among surgeons. Recently, retroperitoneal endoscopic surgery has been applied to various spinal disorders. When the psoas major muscle is separated during retroperitoneal endoscopic surgery, there is a potential risk of injury to the lumbar plexus or nerve roots. However, there is sparse knowledge regarding the relationship between the greater psoas muscle and the lumbar plexus.
  
  
  METHODS
  A total of 30 cadavers were analyzed. Six lumbar spines of the cadavers were cut in parallel with the lumbar disc space. Each axial section was photographed and captured into a computer. The distribution of the lumbar plexus was analyzed using computer images. The positions where the genitofemoral nerve emerged on the abdominal surface of the psoas major muscle were analyzed using 24 cadavers.
  
  
  RESULTS
  L2/3 and above, all parts of the lumbar plexus, and nerve roots were located from the dorsal fourth of the vertebral body and dorsally. The genitofemoral nerve descends obliquely forward through the psoas major muscle, emerging on the abdominal surface between the cranial third of the L3 vertebra and the caudal third of the L4 vertebra. The safety zone of the psoas major muscle to prevent nerve injuries, excluding the genitofemoral nerve, is at L4/L5 and above.
  
  
  CONCLUSIONS
  The safety zone, excluding the genitofemoral nerve, is at L4-L5 and above.
authors.affiliation: Department of Orthopaedic Surgery, Fukushima Medical University, School of Medicine, Fukushima City, Japan. moro@fmu.ac.jp
authors.forename: Takatomo
authors.initials: T
authors.lastname: Moro
authors.forename: Shin-ichi
authors.initials: S
authors.lastname: Kikuchi
authors.forename: Shin-ichi
authors.initials: S
authors.lastname: Konno
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Yaginuma
mesh_terms: D002102:Cadaver; D005267:Femoral Nerve / Q000033:anatomy & histology; D005835:Genitalia / Q000294:innervation; D006801:Humans; D010535:Laparoscopy / Q000379:methods*; D008160:Lumbosacral Plexus / Q000033:anatomy & histology*; D009132:Muscles / Q000033:anatomy & histology; D012187:Retroperitoneal Space; D013126:Spinal Nerve Roots / Q000033:anatomy & histology