title: Effect of the transligamentous extension of lumbar disc herniations on their regression and the clinical outcome of sciatica.
abstract: METHODS
  Magnetic resonance imaging of symptomatic herniated lumbar discs was investigated longitudinally and prospectively for the presence of tear in the posterior longitudinal ligament (PLL).
  
  
  OBJECTIVE
  To clarify the effect of transligamentous extension through the PLL of herniated disc on its regression and to determine the factors contributing to a successful clinical outcome.
  
  
  BACKGROUND
  Greater regression of the herniated fragment has been noted with larger initial disc herniations. The exposure of herniated disc materials to the epidural vascular supply through the ruptured PLL has been suspected to play a part in the mechanism of disappearance of the herniated nucleus pulposus. However, it had not been shown clinically.
  
  
  METHODS
  Clinical outcomes and magnetic resonance images of 36 patients with symptomatic lumbar disc herniations, treated conservatively, were analyzed. Patients were divided into three groups: subligamentous, transligamentous, and sequestered herniations. The size of the herniated disc was measured by herniation ratio, which is defined as the ratio of the area of herniated disc to that of the thecal sac on the axial view. Factors associated with the natural regression of herniated disc and the successful clinical outcome were explored.
  
  
  RESULTS
  Of the 36 herniated discs, 25 decreased in size. Ten (56%) of 18 subligamentous herniations, 11 (79%) of 14 transligamentous herniations, and all 4 (100%) sequestered herniations were reduced in size. The average decreases in herniation ratio of the subligamentous, transligamentous, and sequestered disc groups were 17%, 48%, and 82% respectively. The decrease in herniation ratio was related to the presence of transligamentous extension but was not related to the initial size of herniation. Successful outcome correlated with a decrease in herniation of more than 20%.
  
  
  CONCLUSIONS
  Transligamentous extension of herniated disc materials through the ruptured PLL is more important to its reduction in size than is the initial size of the herniated disc. Decrease in herniation ratio of more than 20% seems to correspond to successful clinical outcome.
authors.affiliation: Department of Rehabilitation Medicine, College of Medicine, Yeungnam University, Taegu, Korea. shahn@medical.yeungnam.ac.kr
authors.forename: S H
authors.initials: SH
authors.lastname: Ahn
authors.forename: M W
authors.initials: MW
authors.lastname: Ahn
authors.forename: W M
authors.initials: WM
authors.lastname: Byun
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D007403:Intervertebral Disc / Q000473:pathology* / Q000503:physiopathology*; D007405:Intervertebral Disc Displacement / Q000473:pathology* / Q000503:physiopathology*; D017846:Longitudinal Ligaments / Q000473:pathology* / Q000503:physiopathology*; D008159:Lumbar Vertebrae / Q000473:pathology* / Q000503:physiopathology*; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D011379:Prognosis; D012585:Sciatica / Q000473:pathology* / Q000503:physiopathology