title: Risk Factors For the Development of a Mobile Degenerative Spondylolisthesis at L4-L5.
abstract: OBJECTIVE
  The purpose of this study was to identify factors that may be important in determining whether a degenerative spondylolisthesis at L4-L5 is mobile.
  
  
  BACKGROUND
  Degenerative scoliosis is a common condition among middle-aged and elderly adults. Sacropelvic morphology and orientation modulate the geometry of the lumbar spine and, consequently, the mechanical stresses at the lumbo-sacral junction. To date, no in vivo data exist to describe the relationship between these pelvic parameters and their association with a mobile spondylolisthesis.
  
  
  METHODS
  Sixty consecutive patients with a degenerative spondylolisthesis (DS) at L4-L5 with adequate imaging were identified. Patient groups were defined on the basis of whether the DS was mobile (Group A) or nonmobile (Group B) when comparing the upright plain lumbar radiograph to the supine magnetic resonance imaging (MRI). We assessed the grade of slip, lumbar lordosis, pelvic parameters, and facet characteristics (angles, tropism, presents of effusion, degenerative score-cartilage and sclerosis values) as well as disc degenerative score (Pfirrmann) at L4-L5.
  
  
  RESULTS
  There were 40 patients in Group A and 20 in Group B. No significant differences were found between groups for pelvic incidence (p = .409), pelvic tilt (p = .476), sacral slope (p = .785), lumbar lordosis (p = .695), degree of facet tropism (p = .38), and magnitude of the facet effusions (p = .01). Facet angle differences between groups approached significance (p = .058). Significant differences between groups were found in cartilage degenerative score (p = .01), facet sclerosis grade (p = .01), and disc degenerative score (p < .0001). In Group A, 10 of 40 (25%) reduced fully and were not apparent on the supine MRI.
  
  
  CONCLUSIONS
  Sagittal pelvic parameters do not play a significant role in differentiating between mobile and nonmobile DS at L4-L5. However, DS does appear to be associated with more sagittally orientated facets, higher Pfirrmann grade, and higher facet cartilage and sclerosis degenerative scores.
authors.affiliation: Department of Spinal Surgery, Frenchay hospital, North Bristol NHS Trust, Beckspool Road, Frenchay, Bristol, BS16 1LE, United Kingdom.
authors.forename: S
authors.initials: S
authors.lastname: Grannum
authors.affiliation: Department of Spinal Surgery, Frenchay hospital, North Bristol NHS Trust, Beckspool Road, Frenchay, Bristol, BS16 1LE, United Kingdom. Electronic address: alextorrie99@hotmail.com.
authors.forename: P A G
authors.initials: PA
authors.lastname: Torrie
authors.affiliation: Department of Spinal Surgery, Frenchay hospital, North Bristol NHS Trust, Beckspool Road, Frenchay, Bristol, BS16 1LE, United Kingdom.
authors.forename: A
authors.initials: A
authors.lastname: Miller
authors.affiliation: Department of Spinal Surgery, Frenchay hospital, North Bristol NHS Trust, Beckspool Road, Frenchay, Bristol, BS16 1LE, United Kingdom.
authors.forename: I J
authors.initials: IJ
authors.lastname: Harding
keywords: Degenerative spondylolisthesis; Pelvic parameters; Risk factors