title: Disc displacement patterns in lumbar anterior spondylolisthesis: contribution to foraminal stenosis.
abstract: OBJECTIVE
  To describe the particular disc displacement pattern seen at MRI in patients with spondylolisthesis, and its potential contribution to foraminal stenosis.
  
  
  METHODS
  38 patients with symptomatic lumbar anterior spondylolisthesis and 38 sex and aged matched control patients with herniated disc disease, at corresponding disc space levels, were included for study. In each case note was made of the presence, absence and direction of disc displacement and also the presence and location of neural contact with the displaced disc.
  
  
  RESULTS
  In 33 of 38 (86.8%) patients in the spondylolisthesis group, the vertical disc displacement was upward. In the control group only 3 patients (7.8%) had upward vertical disc displacement. 19 patients (53%) from the spondylolisthesis group had exit foraminal nerve root contact, compared to 7 patients (18.4%) from the control group. 27 control patients (71%) had contact within the lateral recess, compared to only 6 patients (17%) with spondylolisthesis. Differences for upward displacement were significant (p<0.05).
  
  
  CONCLUSIONS
  Disc displacement in patients with spondylolisthesis is predominately in a cephalad and lateral direction. Although this disc displacement pattern can occur in patients without spondylolisthesis, its incidence is much greater in the subset of patients with concomitant spondylolisthesis. In the setting of acquired osseous narrowing of the exit foramen, this described pattern of disc displacement superiorly and laterally in spondylolisthesis increases the susceptibility of spondylolisthesis patients to radicular symptoms and accounts for the exiting nerve root being more commonly affected than the traversing nerve root.
authors.affiliation: The Department of Radiology, Cappagh National Orthopaedic Hospital, Finglas, Dublin 11, Ireland. petermacmahon@yahoo.com
authors.forename: P J
authors.initials: PJ
authors.lastname: MacMahon
authors.forename: D H
authors.initials: DH
authors.lastname: Taylor
authors.forename: D
authors.initials: D
authors.lastname: Duke
authors.forename: D D
authors.initials: DD
authors.lastname: Brennan
authors.forename: S J
authors.initials: SJ
authors.lastname: Eustace
mesh_terms: D005260:Female; D006801:Humans; D007405:Intervertebral Disc Displacement / Q000150:complications* / Q000175:diagnosis*; D008159:Lumbar Vertebrae / Q000473:pathology; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008875:Middle Aged; D013130:Spinal Stenosis / Q000150:complications* / Q000175:diagnosis*; D013168:Spondylolisthesis / Q000150:complications* / Q000175:diagnosis*