title: Spontaneous reduction finding: magnetic resonance imaging evaluation of segmental instability in spondylolisthesis.
abstract: METHODS
  Retrospective chart review.
  
  
  OBJECTIVE
  To assess whether spontaneous reduction of spondylolisthesis, as seen on magnetic resonance imaging (MRI), is related to the degree of segmental instability and low back pain.
  
  
  BACKGROUND
  The flexion-extension radiographs obtained in the sagittal plane are frequently used when segmental instability of spondylolisthesis is evaluated.
  
  
  METHODS
  We retrospectively reviewed 137 patients and measured the differences of the percentage of sagittal translation and sagittal angulation to determine the segmental instability between the flexion and extension radiographs, and the spontaneous reduction on MRI. We then compared the degrees of segmental instability and the degrees of spontaneous reduction. To assess the effect of low back pain on segmental motion in regards to the flexion-extension radiographs, we compared the preoperative visual analogue scales (VAS) score for low back pain between the more and the less spontaneous reduction groups.
  
  
  RESULTS
  The mean degree of spontaneous reduction was 5.2%. A statistically significant correlation was found between the sagittal translation on the flexion-extension radiographs and the degree of spontaneous reduction (r = 0.557, p < 0.001) and between the sagittal angulation on the flexion-extension radiographs and the degree of spontaneous reduction (r = 0.215, p = 0.012). The preoperative VAS scores for low back pain of the more spontaneous reduction group and the less spontaneous reduction group were 4.6 and 3.6 points, respectively, and this difference was statistically significant (p = 0.002).
  
  
  CONCLUSIONS
  Spontaneous reduction of spondylolisthesis on MRI was found to be closely related to segmental instability, and the degree of spontaneous reduction seen on MRI could be useful for the evaluation of segmental instability in patients with spondylolisthesis, especially with severe low back pain.
authors.affiliation: Department of Orthopedic Surgery, Chonnam National University Hospital, Chonnam National University Medical School, Gwangju, Korea.
authors.forename: Jae Yoon
authors.initials: JY
authors.lastname: Chung
authors.forename: Sung Kyu
authors.initials: SK
authors.lastname: Kim
authors.forename: Sung Taek
authors.initials: ST
authors.lastname: Jung
authors.forename: Keun Bae
authors.initials: KB
authors.lastname: Lee
authors.forename: Hyoung Yeon
authors.initials: HY
authors.lastname: Seo
authors.forename: Chang Yong
authors.initials: CY
authors.lastname: Hu
authors.forename: Gi Heon
authors.initials: GH
authors.lastname: Park
keywords: Magnetic resonance imaging; Segmental instability; Spondylolisthesis; Spontaneous reduction