title: Lumbar sagittal contour after posterior interbody fusion: threaded devices alone versus vertical cages plus posterior instrumentation.
abstract: METHODS
  An observational radiographic study examining lumbar sagittal contour of patients undergoing posterior interbody arthrodesis.
  
  
  OBJECTIVE
  To compare operative alterations of lumbar sagittal contour after posterior interbody fusion using threaded interbody devices alone versus vertical cages combined with posterior compression instrumentation.
  
  
  BACKGROUND
  Technique-related alterations of lumbar sagittal contour during interbody arthrodesis have received little attention in the spinal literature.
  
  
  METHODS
  Standing lumbar radiographs were measured for preoperative and postoperative segmental lordosis at levels undergoing posterior interbody arthrodesis using either stand-alone side-by-side threaded devices or vertical cages combined with posterior transpedicular compression instrumentation. Sagittal plane segmental correction (or loss of correction) was calculated and statistically compared.
  
  
  RESULTS
  The radiographs of 30 patients (34 spinal segments) undergoing lumbar or lumbosacral arthrodesis were compared. Seventeen patients (18 segments) had undergone interbody fusion using threaded cages,whereas 13 patients (16 segments) underwent fusion using vertically oriented mesh cages combined with posterior compression instrumentation. Preoperative segmental lordosis averaged 8 degrees for both groups. For patients undergoing fusion with threaded cages, there was a mean lordotic loss of 3 degrees/segment. For patients undergoing fusion with vertically oriented mesh cages combined with posterior compression instrumentation,there was a mean lordotic gain of 5 degrees/segment. This difference in segmental sagittal plane contour was highly significant (P = 0.00).
  
  
  CONCLUSIONS
  Threaded fusion devices placed under interbody distraction with the endplates parallel fail to preserve or reestablish segmental lordosis. Vertical cages, however, when combined with posterior compression instrumentation, not only maintain segmental lordosis, but also can correct sagittal plane deformity.
authors.affiliation: Department of Orthopaedic Surgry and Rehabilitation, Walter Reed Army Medical Center, Washington, DC 20307, USA. William.Klemme@na.amedd.army.mil
authors.forename: W R
authors.initials: WR
authors.lastname: Klemme
authors.forename: B D
authors.initials: BD
authors.lastname: Owens
authors.forename: A
authors.initials: A
authors.lastname: Dhawan
authors.forename: S
authors.initials: S
authors.lastname: Zeidman
authors.forename: D W
authors.initials: DW
authors.lastname: Polly
mesh_terms: D006801:Humans; D008141:Lordosis / Q000000981:diagnostic imaging / Q000601:surgery*; D008159:Lumbar Vertebrae / Q000000981:diagnostic imaging* / Q000601:surgery; D015588:Observer Variation; D011379:Prognosis; D011859:Radiography; D015203:Reproducibility of Results; D012447:Sacrum / Q000000981:diagnostic imaging* / Q000601:surgery; D013123:Spinal Fusion / Q000295:instrumentation*