title: Bilateral pedicle fractures following anterior dislocation of the polyethylene inlay of a ProDisc artificial disc replacement: a case report of an unusual complication.
abstract: METHODS
  An unusual complication resulting from an artificial disc replacement for lumbar degenerative disc disease and its treatment are reported
  
  
  OBJECTIVE
  To describe the clinical circumstance, radiologic findings, treatment, and outcome of bilateral pedicle fractures associated with dislocation of the polyethylene inlay of a ProDisc replacement at L5/S1 level.
  
  
  BACKGROUND
  To the authors' knowledge, no published reports in the English literature have described bilateral pedicle fractures following a single level artificial lumbar total disc replacement.
  
  
  METHODS
  A 30-year-old male underwent a ProDisc total disc replacement at L5/S1 level for discogenic pain. Six-week postoperative assessment showed improvement in the visual analog and Oswestry scores. Assessment at 18 weeks postoperatively for acute pain revealed an anterior slip of the superior plate component, and computerized tomography showed bilateral pedicle fractures of the fifth lumbar vertebra. At surgery, the poly insert was found to have dislocated anteriorly. A salvage interbody fusion was then performed using the stand-alone anterior lumbar interbody fusion cage.
  
  
  RESULTS
  The most recent review confirmed radiologic evidence of fusion with improvement in the subjective evaluation scores
  
  
  CONCLUSIONS
  We hypothesize that the current implant design in which the contribution to lordosis angle is purely from the superior component may be responsible for the reported complication. We suggest that dividing the contribution equally between both endplates might increase the stability, and this has been discussed with the manufacturers.
authors.affiliation: Department of Orthopaedics, Princess Alexandra Hospital, Harlow, United Kingdom. philip.mathew@virgin.net
authors.forename: Philip
authors.initials: P
authors.lastname: Mathew
authors.forename: Mark
authors.initials: M
authors.lastname: Blackman
authors.forename: Sridhar
authors.initials: S
authors.lastname: Redla
authors.forename: Ahmed A
authors.initials: AA
authors.lastname: Hussein
mesh_terms: D000328:Adult; D019643:Arthroplasty, Replacement / Q000009:adverse effects* / Q000295:instrumentation; D001860:Bone Plates; D015775:Fractures, Stress / Q000000981:diagnostic imaging / Q000209:etiology*; D006801:Humans; D016268:Internal Fixators; D007405:Intervertebral Disc Displacement / Q000601:surgery*; D008159:Lumbar Vertebrae / Q000000981:diagnostic imaging / Q000601:surgery; D008297:Male; D016348:Osseointegration; D011183:Postoperative Complications; D011475:Prosthesis Failure; D012086:Reoperation; D012447:Sacrum / Q000000981:diagnostic imaging / Q000601:surgery; D016103:Spinal Fractures / Q000000981:diagnostic imaging / Q000209:etiology*; D014057:Tomography, X-Ray Computed; D016896:Treatment Outcome