title: Variability of manual lumbar spine segmentation.
abstract: BACKGROUND
  The application of kinematic data acquired during biomechanical testing to specimen-specific, three-dimensional models of the spine has emerged as a useful tool in spine biomechanics research. However, the development of these models is subject to segmentation error because of complex morphology and pathologic changes of the spine. This error has not been previously characterized.
  
  
  METHODS
  Eight cadaveric lumbar spines were prepared and underwent computed tomography (CT) scanning. After disarticulation and soft-tissue removal, 5 individual vertebrae from these specimens were scanned a second time. The CT images of the full lumbar specimens were segmented twice each by 2 operators, and the images of the individual vertebrae with soft tissue removed were segmented as well. The solid models derived from these differing segmentation sessions were registered, and the distribution of distances between nearest neighboring points was calculated to evaluate the accuracy and precision of the segmentation technique.
  
  
  RESULTS
  Manual segmentation yielded root-mean-square errors below 0.39 mm for accuracy, 0.33 mm for intrauser precision, and 0.35 mm for interuser precision. Furthermore, the 95th percentile of all distances was below 0.75 mm for all analyses of accuracy and precision.
  
  
  CONCLUSIONS
  These findings indicate that such models are highly accurate and that a high level of intrauser and interuser precision can be achieved. The magnitude of the error presented here should inform the design and interpretation of future studies using manual segmentation techniques to derive models of the lumbar spine.
authors.affiliation: Department of Neurosurgery, Allegheny General Hospital, Pittsburgh, PA.
authors.forename: Daniel J
authors.initials: DJ
authors.lastname: Cook
authors.affiliation: Department of Neurosurgery, Allegheny General Hospital, Pittsburgh, PA.
authors.forename: David A
authors.initials: DA
authors.lastname: Gladowski
authors.affiliation: Department of Neurosurgery, Allegheny General Hospital, Pittsburgh, PA.
authors.forename: Heather N
authors.initials: HN
authors.lastname: Acuff
authors.affiliation: Department of Neurosurgery, Allegheny General Hospital, Pittsburgh, PA.
authors.forename: Matthew S
authors.initials: MS
authors.lastname: Yeager
authors.affiliation: Department of Neurosurgery, Allegheny General Hospital, Pittsburgh, PA ; Department of Neurosurgery, Drexel University College of Medicine, Pittsburgh, PA.
authors.forename: Boyle C
authors.initials: BC
authors.lastname: Cheng
keywords: Accuracy; Lumbar spine; Manual segmentation; Precision; Solid models