title: Replacing the nucleus pulposus of the intervertebral disc.
abstract: OBJECTIVE
  To determine whether replacement of the nucleus with a synthetic material would prevent the effects of nucleus removal.
  
  
  METHODS
  Laboratory experiments on excised tissues and a finite element model.
  
  
  BACKGROUND
  Removal of the nucleus from the intervertebral disc causes the inner margins of the annulus to bulge inwards, instead of outwards, during compression. This may cause the annulus to degenerate further.
  
  
  METHODS
  Video recordings of sheep discs, sectioned in the sagittal plane, were obtained during compression in a materials testing machine; the cut face of the disc was sealed with a Perspex window. Experiments were repeated with the nucleus removed and then replaced by a synthetic implant. A finite element model of an intact disc was also used to investigate the effect of nucleus replacement.
  
  
  RESULTS
  When the nucleus of sectioned discs was replaced with the polymer materials, the inward bulging of the annulus was not observed. The predictions from the finite element model of the intact disc were consistent with this result.
  
  
  CONCLUSIONS
  Replacement of the nucleus with a synthetic material can prevent the changes in annulus behaviour that result from removal of the nucleus.
  
  
  CONCLUSIONS
  A suitable implant to replace the nucleus after surgical removal may help prevent inward bulging of the inner layers of the annulus.
authors.affiliation: Department of Bio-Medical Physics and Bio-Engineering, University of Aberdeen, Foresterhill, AB25 2ZD, Aberdeen, UK. j.meakin@biomed.abdn.ac.uk
authors.forename: J R
authors.initials: JR
authors.lastname: Meakin
authors.forename: J E
authors.initials: JE
authors.lastname: Reid
authors.forename: D W
authors.initials: DW
authors.lastname: Hukins
mesh_terms: D000818:Animals; D001696:Biomechanical Phenomena; D020342:Finite Element Analysis; D007403:Intervertebral Disc / Q000503:physiopathology* / Q000601:surgery*; D007405:Intervertebral Disc Displacement / Q000503:physiopathology; D016012:Poisson Distribution; D011108:Polymers; D019736:Prostheses and Implants; D012756:Sheep; D012828:Silicones; D013499:Surface Properties; D014741:Video Recording
chemical_list: D011108:Polymers; D012828:Silicones