title: Lumbar degenerative spondylolisthesis is not always unstable: clinicobiomechanical evidence.
abstract: METHODS
  A clinicobiomechanical study.
  
  
  OBJECTIVE
  To clarify the clinicobiomechanical characteristics of a segment with lumbar degenerative spondylolisthesis (LDS) using an original intraoperative measurement system.
  
  
  BACKGROUND
  Although radiographical evaluation of LDS is extensively performed, the diagnosis of segmental instability remains controversial. The intraoperative measurement system used in this study is the first clinically available system that performs cyclic flexion-extension displacement of the segment with all ligamentous structures intact and can determine both the stiffness (N/mm) and neutral zone (NZ, [mm/N]).
  
  
  METHODS
  Forty-eight patients with LDS (males/females = 19/29, 68.5 yr; group D) were compared with 48 patients with lumbar spinal stenosis without LDS (males/females = 33/15, 64.8 yr, group N) in terms of symptoms, radiological, and biomechanical results. Instability was defined as a segment with NZ more than 2 mm. Symptoms (36-Item Short Form Health Survey), radiographical findings (radiographs, magnetic resonance images, computed tomographic scans), stiffness, NZ, and frequency of instability were also compared. Risk factors for instability were analyzed by multivariate logistic regression with a forward stepwise procedure.
  
  
  RESULTS
  None of the physical function categories or radiological findings of 36-Item Short Form Health Survey and low back pain (visual analogue scale) differed significantly between the groups. Although NZ was significantly greater in group D (1.97) than in group N (1.73) (P < 0.05), the frequency of instability did not differ significantly between groups. Facet opening (odds ratio, 11.0; P < 0.01) and facet type (odds ratio, 6.0; P < 0.05) were significant risk factors for instability.
  
  
  CONCLUSIONS
  Neither the symptoms nor the frequency of instability differed significantly between groups. The radiological findings of spondylolisthesis did not indicate instability, but facet opening and sagittally oriented facets were indicative of instability. The results of this study demonstrated that LDS is not always unstable in the measurement setting, suggesting that the instability of LDS can stabilize spontaneously during the natural course.
  
  
  METHODS
  N/A.
authors.affiliation: *Niigata Spine Surgery Center, Niigata, Japan †Showa Ikakogyo Co. Ltd, Toyohashi, Japan; and ‡Department of Orthopaedic Surgery, Niigata University Hospital, Niigata, Japan.
authors.forename: Kazuhiro
authors.initials: K
authors.lastname: Hasegawa
authors.forename: Ko
authors.initials: K
authors.lastname: Kitahara
authors.forename: Haruka
authors.initials: H
authors.lastname: Shimoda
authors.forename: Keiji
authors.initials: K
authors.lastname: Ishii
authors.forename: Masatoshi
authors.initials: M
authors.lastname: Ono
authors.forename: Takao
authors.initials: T
authors.lastname: Homma
authors.forename: Kei
authors.initials: K
authors.lastname: Watanabe
mesh_terms: D000368:Aged; D001696:Biomechanical Phenomena / Q000502:physiology; D005260:Female; D006801:Humans; D007593:Joint Instability / Q000503:physiopathology* / Q000601:surgery; D017116:Low Back Pain / Q000503:physiopathology* / Q000601:surgery; D008159:Lumbar Vertebrae / Q000503:physiopathology* / Q000601:surgery; D008297:Male; D008875:Middle Aged; D013130:Spinal Stenosis / Q000503:physiopathology* / Q000601:surgery; D013168:Spondylolisthesis / Q000503:physiopathology* / Q000601:surgery; D016896:Treatment Outcome