title: Evaluation of lumbar segmental instability in degenerative diseases by using a new intraoperative measurement system.
abstract: OBJECTIVE
  In vivo quantitative measurement of lumbar segmental stability has not been established. The authors developed a new measurement system to determine intraoperative lumbar stability. The objective of this study was to clarify the biomechanical properties of degenerative lumbar segments by using the new method.
  
  
  METHODS
  Twenty-two patients with a degenerative symptomatic segment were studied and their measurements compared with those obtained in normal or asymptomatic degenerative segments (Normal group). The measurement system produces cyclic flexion-extension through spinous process holders by using a computer-controlled motion generator with all ligamentous structures intact. The following biomechanical parameters were determined: stiffness, absorption energy (AE), and neutral zone (NZ). Discs with degeneration were divided into 2 groups based on magnetic resonance imaging grading: degeneration without collapse (Collapse[-]) and degeneration with collapse (Collapse[+]). Biomechanical parameters were compared among the groups. Relationships among the biomechanical parameters and age, diagnosis, or radiographic parameters were analyzed.
  
  
  RESULTS
  The mean stiffness value in the Normal group was significantly greater than that in Collapse(-) or Collapse(+) group. There was no significant difference in the average AE value among the Normal, Collapse(-), and Collapse(+) groups. The NZ in the Collapse(-) was significantly higher than in the Normal or Collapse(+) groups. Stiffness was negatively and NZ was positively correlated with age. Stiffness demonstrated a significant negative and NZ a significant positive relationship with disc height, however.
  
  
  CONCLUSIONS
  There were no significant differences in stiffness between spines in the Collapse(-) and Collapse(+) groups. The values of a more sensitive parameter, NZ, were higher in Collapse(-) than in Collapse(+) groups, demonstrating that degenerative segments with preserved disc height have a latent instability compared to segments with collapsed discs.
authors.affiliation: Niigata Spine Surgery Center, Niigata University, Niigata, Japan. kazu3795jp@yahoo.co.jp
authors.forename: Kazuhiro
authors.initials: K
authors.lastname: Hasegawa
authors.forename: Ko
authors.initials: K
authors.lastname: Kitahara
authors.forename: Toshiaki
authors.initials: T
authors.lastname: Hara
authors.forename: Ko
authors.initials: K
authors.lastname: Takano
authors.forename: Haruka
authors.initials: H
authors.lastname: Shimoda
authors.forename: Takao
authors.initials: T
authors.lastname: Homma
mesh_terms: D015502:Absorptiometry, Photon; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001696:Biomechanical Phenomena; D005260:Female; D006801:Humans; D007430:Intraoperative Care; D007796:Laminectomy; D008159:Lumbar Vertebrae / Q000473:pathology* / Q000601:surgery*; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D019636:Neurodegenerative Diseases / Q000175:diagnosis / Q000473:pathology* / Q000601:surgery*; D011183:Postoperative Complications / Q000175:diagnosis* / Q000453:epidemiology; D013168:Spondylolisthesis / Q000175:diagnosis / Q000473:pathology* / Q000601:surgery*