title: The risk of foraminal violation and nerve root impingement after anterior placement of lumbar interbody fusion cages.
abstract: METHODS
  Three groups of six embalmed cadaver spines underwent placement of lumbar interbody fusion cages centered either at midline, 10% lateral of midline, or 20% lateral of midline. The spines were evaluated for evidence of neuroforamen violation or nerve root impingement.
  
  
  OBJECTIVE
  To determine the potential for foraminal violation or nerve root impingement after correct placement and lateral misplacement of lumbar interbody fusion cages.
  
  
  BACKGROUND
  Radicular symptoms after anterior cage placement have raised some concern about the potential for inadvertent device-related foraminal violation not adequately appreciated by intraoperative fluoroscopy.
  
  
  METHODS
  Preoperative computed tomography scanning and plain radiography was used to measure endplate dimensions at L4-L5 and to template the appropriately sized interbody fusion cages. The cadaveric specimens were randomly divided into three groups of six (Groups I-III) and instrumented at L4-L5 either at midline (I) or 10% (II) or 20% (III) lateral of midline. Postoperative computed tomography and plain radiography was evaluated for evidence of neuroforamen violation, followed by dissection of the specimens.
  
  
  RESULTS
  Foraminal violation occurred in one of six spines in group II (10% off midline) and in three of six spines in group III (20% off midline). Two of the three cadavers in group III with foraminal violation also were noted to have nerve root abutment on computed tomography scans and spinal dissection.
  
  
  CONCLUSIONS
  Excessive lateral placement of lumbar interbody fusion cages may result in foraminal violation and possible nerve encroachment. The "safe zone" for centering the cages extends approximately 5 mm on either side of midline.
authors.affiliation: Department of Orthopaedic Surgery, The Rothman Institute at Thomas Jefferson University, Philadelphia, PA, USA.
authors.forename: B A
authors.initials: BA
authors.lastname: Taylor
authors.forename: A R
authors.initials: AR
authors.lastname: Vaccaro
authors.forename: A S
authors.initials: AS
authors.lastname: Hilibrand
authors.forename: D A
authors.initials: DA
authors.lastname: Zlotolow
authors.forename: T J
authors.initials: TJ
authors.lastname: Albert
mesh_terms: D005539:Foramen Magnum / Q000000981:diagnostic imaging / Q000293:injuries*; D006801:Humans; D008159:Lumbar Vertebrae / Q000000981:diagnostic imaging / Q000601:surgery; D011859:Radiography; D013123:Spinal Fusion / Q000009:adverse effects* / Q000295:instrumentation / Q000379:methods; D013126:Spinal Nerve Roots / Q000000981:diagnostic imaging / Q000293:injuries*