title: Variability in Flexion Extension Radiographs of the Lumbar Spine: A Comparison of Uncontrolled and Controlled Bending.
abstract: BACKGROUND
  While low back pain is one of the most prevalent, if not the most prevalent reasons for visits to physicians, a majority of patients with low back pain cannot be given a definitive diagnosis. While there have been substantial advances in imaging technologies over the past 30 years, relatively little has changed in the methodologies for evaluating functionality of the lumbar spine. The current standard of care for function assessment of the lumbar spine focuses on uncontrolled patient directed motion which results in increased inter-patient variability. Recent advancements in functional lumbar spine testing utilize controlled bending and computerized imaging evaluation.
  
  
  OBJECTIVE
  To compare the measurement variability of lumbar spine motion when diagnosed using measurements of intervertebral motion taken from standard bending flexion/extension radiographs (FE) between uncontrolled and controlled motion.
  
  
  METHODS
  One-hundred nine patients (57 asymptomatic, 52 symptomatic) were consented in the prospective investigation. The research was designed to compare studies involving FE to controlled motion bending radiographs using the Vertebral Motion Analysis (VMA), (Ortho Kinematics, Inc) within the same patient. Each patient agreed to undergo fluoroscopic still imaging to capture FE data and to undergo cine fluoroscopic imaging to capture VMA data.
  
  
  METHODS
  Measurement variability was determined by the mean and standard deviation of intervertebral rotation when evaluated by 5 independent observers evaluating each of the 109 patients FE and VMA. The resulting standard deviation of the intervertebral rotation determinations was used as the measure of variability.
  
  
  METHODS
  The VMA measurements for assessing intervertebral motion were characterized by the use of: (1) a handling device that assists patients through a standard arc of lumbar bending in both an upright and recumbent posture (70 degree flexion/extension arcs; 60 degree left/right bending arcs); (2) video fluoroscopy imaging of the lumbar spine during bending (capturing images at 8 frames per second); and (3) image processing software capable of automatic frame-to-frame registration and tracking of vertebral bodies across the sequence of video-fluoroscopic images to derive measurements of intervertebral rotation and translation. The FE data were assessed from voluntary bending by the patient.
  
  
  RESULTS
  There was statistical greater measurement variability in intervertebral rotation in FE when compared to VMA (both standing and lying). When comparing measurement variability between FE and VMA, results indicate between a 26% to 46% decrease in measurement variability under VMA compared to FE. These findings are consistent across asymptomatic and symptomatic patients.
  
  
  CONCLUSIONS
  The current standard of care for functional testing of the lumbar spine utilizes uncontrolled FE with a manual data evaluation process. Recent developments in using computerized imaging processes has improved, however there remains variability in patient bending due to the self-selected rate and position of the bending. VMA results in a significant reduction in measurement variability of intervertebral rotation measurements.
authors.affiliation: Department of Neurosurgery, Drexel University College of Medicine, Pittsburgh, PA.
authors.forename: Boyle
authors.initials: B
authors.lastname: Cheng
authors.affiliation: Florida Orthopedic Institute, Tampa, FL.
authors.forename: Anthony E
authors.initials: AE
authors.lastname: Castellvi
authors.affiliation: Department of Neurosurgery, Greater Baltimore Medical Center, Baltimore, MD.
authors.forename: Reginald J
authors.initials: RJ
authors.lastname: Davis
authors.affiliation: Southern Neurologic and Spinal Institute, Hattiesburg MS.
authors.forename: David C
authors.initials: DC
authors.lastname: Lee
authors.affiliation: Neuro-Spine Solutions, Bristol, TN.
authors.forename: Morgan P
authors.initials: MP
authors.lastname: Lorio
authors.affiliation: Department of Industrial and Systems Engineering, Auburn University, Auburn, AL.
authors.forename: Richard E
authors.initials: RE
authors.lastname: Prostko
authors.affiliation: Department of Industrial and Systems Engineering, Auburn University, Auburn, AL.
authors.forename: Chip
authors.initials: C
authors.lastname: Wade
keywords: controlled motion bending; flexion/extension radiographs; lumbar spine; variability; vertebral motion analysis (vma)