title: Morphometric analysis of the working zone for endoscopic lumbar discectomy.
abstract: OBJECTIVE
  Our study's purpose was to analyze the working zone for the current practice of endoscopic discectomy at the lateral exit zone of the intervertebral foramen (IVF) and to define a safe point for clinical practice.
  
  
  METHODS
  One hundred eighty-six nerve roots of the lumbar IVFs of cadaveric spines were studied. Upon lateral inspection, we measured the distance from the nerve root to the most dorsolateral margin of the disc and to the lateral edge of the superior articular process of the vertebra below at the plane of the superior endplate of the vertebra below. The angle between the root and the plane of the disc was also measured.
  
  
  RESULTS
  The results showed that the mean distance from the nerve root to the most dorsolateral margin of the disc was 3.4 +/- 2.7 mm (range 0.0-10.8 mm), the mean distance from the nerve root to the lateral edge of the superior articular process of the vertebra below was 11.6 +/- 4.6 mm (range 4.1-24.3 mm), and the mean angle between the nerve root and the plane of the disc was 79.1 degrees +/- 7.6 degrees (range 56.0-90.0 degrees ).
  
  
  CONCLUSIONS
  The values of the base of the working zone have a wide distribution. Blind puncture of annulus by the working cannula or obturator may be dangerous. The safer procedure would be the direct viewing of the annulus by endoscopy before annulotomy; the working cannula should be inserted into the foramen as close as possible to the facet joint.
authors.affiliation: Department of Neurosurgery, College of Medicine, Korea University, Seoul, Korea.
authors.forename: Jun-Hong
authors.initials: JH
authors.lastname: Min
authors.forename: Shin-Hyuk
authors.initials: SH
authors.lastname: Kang
authors.forename: Jang-Bo
authors.initials: JB
authors.lastname: Lee
authors.forename: Tai-Hyoung
authors.initials: TH
authors.lastname: Cho
authors.forename: Jung-Keun
authors.initials: JK
authors.lastname: Suh
authors.forename: Im-Joo
authors.initials: IJ
authors.lastname: Rhyu
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001837:Body Weights and Measures; D017587:Diskectomy, Percutaneous / Q000379:methods / Q000592:standards*; D004724:Endoscopy / Q000379:methods / Q000592:standards*; D005260:Female; D006801:Humans; D007403:Intervertebral Disc / Q000033:anatomy & histology* / Q000473:pathology / Q000601:surgery; D007431:Intraoperative Complications / Q000209:etiology / Q000517:prevention & control; D008159:Lumbar Vertebrae / Q000033:anatomy & histology* / Q000473:pathology / Q000601:surgery; D008297:Male; D008488:Medical Illustration; D008875:Middle Aged; D013126:Spinal Nerve Roots / Q000033:anatomy & histology / Q000601:surgery; D021801:Zygapophyseal Joint / Q000033:anatomy & histology / Q000601:surgery